Patent Publication Number: US-11654306-B2

Title: Ultrasonic surgical instrument with cooling system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/705,653, filed on Sep. 15, 2017, which is a continuation of U.S. patent application Ser. No. 14/630,138, filed Feb. 24, 2015, now U.S. Pat. No. 9,764,166, which is a continuation-in-part of U.S. patent application Ser. No. 14/284,741, filed May 22, 2014, now U.S. Pat. No. 9,622,767, which claims the benefit of and priority to U.S. Provisional Patent Application Nos. 61/876,449 and 61/876,457, both of which filed Sep. 11, 2013. The entire contents of each of the above applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates generally to surgical instruments, and in particular, to ultrasonic surgical instruments having fluid-cooled components and related methods of cooling ultrasonic surgical instruments. 
     2. Discussion of Related Art 
     Energy-based tissue treatment is well known in the art. Various types of energy (e.g., electrical, ultrasonic, microwave, cryogenic, thermal, laser, etc.) are applied to tissue to achieve a desired result. Ultrasonic energy, for example, may be delivered to tissue using a surgical probe that includes a transducer coupled with an end effector configured to deliver the ultrasonic energy to tissue. 
     A typical ultrasonic surgical instrument incorporates a sinusoidal driving signal which causes the mechanical tip of a waveguide to vibrate at a selected frequency, usually in the range of 20 KHz to 60 KHz, for cutting and/or coagulating tissue. Improved cutting may result from increased tissue-to-mechanical tip coupling caused by the high frequency of vibration of the mechanical tip in relation to tissue. Improved coagulation may result from heat generated by coupling between the high frequency vibrations of the mechanical tip and body tissue. 
     Ultrasonic surgical instruments may include any of a variety of waveguides configured to achieve a surgical result. For example, an ultrasonic waveguide may be disposed at a distal end of the ultrasonic instrument. The waveguide may include an end effector that includes a cutting blade, shears, a hook, a ball, etc., and may be combined with other features such as jaws for grasping or manipulating tissue. During use, waveguides on ultrasonic surgical instruments can reach temperatures greater than 200° C. 
     SUMMARY 
     According to an aspect of the present disclosure, an ultrasonic surgical instrument is provided including a handle assembly, an elongated body member, a tool assembly, and a blade cooling system. The elongated body member extends distally from the handle assembly and defines a longitudinal axis. The elongated body member includes a waveguide positioned coaxially within a lumen of an outer tube. The tool assembly is coupled to a distal end of the elongated body member and includes a blade coupled to the distal end of the wave guide. The blade is configured to oscillate with respect to the outer tube for ultrasonically treating tissue. The blade cooling system includes a blade conduit extending at least partially through the blade. A cooling fluid is configured to flow through the blade conduit. In embodiments, the blade cooling system is a closed-loop system. In some embodiments, the blade cooling system is an open system. 
     The elongated body member can also include a cooling conduit in fluid communication with the blade conduit. In aspects, the cooling conduit is defined between the outer tube and the waveguide. In particular aspects, the cooling conduit is constructed of a microtube. In certain aspects, the cooling conduit and the blade conduit form a fully enclosed heat pipe such that the cooling fluid is configured to absorb heat from the blade and the cooling conduit is configured to release the absorbed heat to the surrounding environment. 
     In aspects, the blade conduit includes a blade outlet in a distal surface of the blade. The blade cooling system may also include an inflow conduit in fluid communication with the blade conduit. In some aspects, the inflow conduit is constructed of a microtube. In particular aspects, the blade cooling system further includes a return conduit in fluid communication with the blade conduit. The return conduit can also be constructed of a polyimide microtube. In certain embodiments, the blade conduit includes a blade inlet between the inflow conduit and the blade conduit and positioned in a proximal portion of the blade. The blade conduit can extend distally within the blade in parallel orientation relative to the longitudinal axis to a first end of a distal section of the blade conduit which is orthogonal to the longitudinal axis and spaced apart from a distal surface of the blade. A second segment of the blade conduit extends proximally within the blade in parallel orientation to the longitudinal axis from a second end of the distal segment to a blade outlet. The blade conduit forms a continuous flow path through the blade from the blade inlet through the distal section and exiting through the blade outlet. The blade outlet can be distal to the blade inlet. The distal section of the blade conduit is spaced-apart from the distal surface of the blade a distance in the range of 0.005 to 0.025 mm. 
     According to another aspect of the present disclosure a surgical system includes an ultrasonic surgical instrument and a blade cooling system. The ultrasonic surgical instrument includes a handle assembly, an elongated body member, and a tool assembly. The elongated body member includes a waveguide having a blade coupled to the distal end. The blade configured to oscillate with respect to the outer tube to ultrasonically treat tissue. The blade cooling system includes a blade conduit, an inflow conduit, and a fluid control system. The blade conduit is disposed within and along the length of the blade. The inflow conduit is disposed within and along the length of the elongated body member. The fluid control system includes a pump configured to pump cooling fluid through the inflow conduit and the blade conduit. 
     The blade cooling system can also include a fluid reservoir storing a cooling fluid therein such that the pump is configured to draw the cooling fluid from the fluid reservoir. In aspects, the blade cooling system further includes a return conduit and the blade conduit includes a distal section orthogonal to the longitudinal axis of the blade. The distal section spaced-apart from a distal surface of the blade. The fluid control system configured to pump the cooling fluid through the inflow conduit, through the blade conduit including the distal section, and through the return conduit. The return conduit in fluid communication with the inflow conduit such that the blade cooling system is a closed-loop system. 
     In aspects, the fluid control system controls activation and deactivation of the pump in accordance with at least one property or condition of the ultrasonic instrument. More specifically, a first sensor may be provided to sense a temperature of the blade. The fluid control system may thus be configured to activate the pump when the temperature of the blade exceeds an upper temperature limit and/or deactivate the pump when the temperature of the blade is less than a lower temperature limit. A second sensor configured to sense a position of an activation button of the ultrasonic surgical instrument may additionally or alternatively be provided. The fluid control system may thus be configured to activate and deactivate the pump for predetermined periods of time according to the position of the activation button (independently of or in conjunction with temperature-based feedback control). 
     According to another aspect of the present disclosure, a method for treating tissue is provided including ultrasonically treating tissue by oscillating a blade of an ultrasonic surgical instrument in contact with tissue and activating a fluid control system to pump the cooling fluid through a blade conduit to cool the blade. The ultrasonic surgical instrument and/or fluid control system may be any of those described herein. 
     In aspects, activating the fluid control system includes depressing an activation button to activate the fluid control system. In aspects, depressing the activation button activates the fluid control system and oscillates the blade. The method may further include releasing the activation button to deactivate the fluid control system and to cease oscillation of the blade. In some aspects, after the activation button is released the method includes delaying the deactivation of the fluid control system until a predetermined amount of time has passed. In particular aspects, the method includes receiving a sensed temperature of the blade after releasing the activation button and deactivating the fluid control system after the sensed temperature of the blade is below a lower temperature limit. 
     In aspects, the method includes receiving a sensed temperature of the blade and verifying the sensed temperature of the blade is above an upper temperature limit before activating the fluid control system. In aspects, the method includes deactivating the fluid control system after the sensed temperature of the blade is below a lower temperature limit. In some aspects, the method includes inputting the upper temperature limit and/or the lower temperature limit before ultrasonically treating tissue. In particular aspects, the method includes varying the amount of fluid flowing through the blade cooling system in response to the sensed temperature of the blade. 
     Another ultrasonic surgical instrument provided in accordance with aspects of the present disclosure includes a handle assembly, an elongated body extending distally from the handle assembly, a waveguide extending at least partially through the elongated body, and a tool assembly including a blade coupled to a distal end of the waveguide. The blade defines a blade lumen extending through the blade. The blade lumen has closed proximal and distal ends. The blade further defines an output in communication with the blade lumen towards the proximal end of the blade lumen. An inflow conduit enters the blade lumen via the output and extends distally through the blade lumen. The inflow conduit defines an open distal end positioned within the blade lumen adjacent the distal end of the blade lumen. A return conduit defines an open distal end positioned within the blade lumen adjacent the proximal end of the blade lumen. The return conduit exits the blade lumen via the output and extends proximally therefrom. 
     In aspects, the inflow and return conduits are microtubes. In aspects, the output is sealed about the inflow and return conduits. In aspects, the output is defined at an anti-node of the waveguide or at any other suitable position along the waveguide. In aspects, an interior surface of the blade lumen and an outer surface of the inflow conduit define an annular gap therebetween. In aspects, the inflow and return conduits extend along the exterior of the elongated body. 
     According to another aspect of the present disclosure a surgical system includes an ultrasonic surgical instrument and a blade cooling system. The ultrasonic surgical instrument may be similar to any of the ultrasonic instruments detailed above. The blade cooling system includes a fluid reservoir and an inflow pump operatively coupled between the fluid reservoir and a proximal end of the inflow conduit. 
     In aspects, the inflow pump is configured to deliver a fluid from the fluid reservoir, through the inflow conduit and the blade lumen, and into return conduit. In aspects, the return conduit is configured to return the fluid to the fluid reservoir or a return reservoir. In aspects, the blade cooling system further includes a return pump coupled to a proximal end of the return conduit and configured to facilitate the return of the fluid from the return conduit into the fluid reservoir or return reservoir. 
     In aspects, the blade cooling system further includes a fluid control system configured to control activation and deactivation of the inflow pump in accordance with at least one property or condition of the ultrasonic surgical instrument. In aspects, a first sensor is configured to sense a temperature of the blade, the fluid control system configured to activate the inflow pump when the temperature of the blade exceeds an upper temperature limit, the fluid control system configured to deactivate the inflow pump when the temperature of the blade is less than a lower temperature limit. In aspects, a second sensor is configured to sense a position of an activation button of the ultrasonic instrument, the fluid control system configured to activate and deactivate the inflow pump for predetermined periods of time according to the position of the activation button. 
     According to another aspect of the present disclosure an ultrasonic surgical instrument is provided including a handle assembly, an elongated body extending distally from the handle assembly, a waveguide extending at least partially through the elongated body, and a tool assembly including a blade coupled to a distal end of the waveguide. The blade defines a blade lumen extending through the blade. The blade lumen has closed proximal and distal ends. The blade further defines an output in communication with the blade lumen towards the proximal end of the blade lumen. An inflow conduit and a return conduit are also provided. The inflow and return conduits extend from a proximal end of the elongated body, distally along an outer surface of the elongated body, through the output, and into the blade lumen. 
     In aspects, the inflow conduit is configured to couple to a first pump at a proximal end thereof, the first pump configured to deliver a fluid through the inflow conduit the blade lumen. In aspects, the return conduit is configured to couple to a second pump at a proximal end thereof, the second pump configured to push and/or pull fluid from the blade lumen through the return conduit. In aspects, the inflow conduit extends distally through the blade lumen and defines an open distal end positioned within the blade lumen adjacent the distal end of the blade lumen. 
     In aspects, the return conduit defines an open distal end positioned within the blade lumen adjacent the proximal end of the blade lumen. In aspects, the output is sealed about the inflow and return conduits. In aspects, the inflow and return conduits are microtubes. 
     Further, to the extent consistent, any of the aspects described herein may be used in conjunction with any or all of the other aspects described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of the present disclosure are described hereinbelow with reference to the drawings, wherein: 
         FIG.  1    is a perspective view of a surgical system provided in accordance with the present disclosure including a surgical instrument incorporating a cooling system; 
         FIG.  2    is an exploded view of the components of the elongated body portion of the surgical instrument of  FIG.  1   ; 
         FIG.  3    is an enlarged view of the tool assembly of the surgical instrument of  FIG.  1    with a portion of the outer tube of the surgical instrument cut away; 
         FIG.  3 A  is an enlargement of the distal end of the surgical instrument of  FIG.  1    with the tool assembly in the closed position; 
         FIG.  4    is a longitudinal, cross-sectional view of the distal end of the surgical instrument of  FIG.  1    illustrating operation of the cooling system; 
         FIG.  5    is an enlarged view of the detail area “ 5 ” of  FIG.  4   ; 
         FIG.  6    is a perspective view of another surgical system provided in accordance with the present disclosure including a surgical instrument incorporating a cooling system; 
         FIG.  7    is a longitudinal, cross-sectional view of the distal end of the surgical instrument of  FIG.  6    illustrating operation of the cooling system; 
         FIG.  8    is a longitudinal, cross-sectional view of another cooling system provided in accordance with the present disclosure and configured for use with the surgical instrument of  FIG.  6   ; 
         FIG.  8 A  is an enlarged view of the detail area “ 8 A” of  FIG.  8   ; 
         FIG.  9    is a perspective view of yet another surgical system provided in accordance with the present disclosure including a surgical instrument incorporating a cooling system; 
         FIG.  9 A  is an enlarged view of the detail area “ 9 A” of  FIG.  9   ; 
         FIG.  10    is a longitudinal, cross-sectional view of the blade of the surgical instrument of  FIG.  9    illustrating the cooling system; 
         FIG.  11    is a longitudinal, cross-sectional view of another blade cooling system provided in accordance with the present disclosure including a cooling conduit disposed within a waveguide; 
         FIG.  12    is a perspective view of yet another surgical system provided in accordance with the present disclosure including a surgical instrument incorporating a cooling system; 
         FIG.  12 A  is an enlarged view of the detail area “ 12 A” of  FIG.  12   ; 
         FIG.  13    is an enlarged, perspective view of the distal end of the surgical instrument of  FIG.  12   ; 
         FIG.  14    is a longitudinal, cross-sectional view of the blade of the surgical instrument of  FIG.  12   ; and 
         FIG.  15    is a perspective view of another surgical system provided in accordance with the present disclosure including a surgical instrument incorporating a cooling system. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present disclosure are now described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. As used herein, the term “clinician” refers to a doctor, a nurse, or any other care provider and may include support personnel. Throughout this description, the term “proximal” will refer to the portion of the device or component thereof that is closest to the clinician and the term “distal” will refer to the portion of the device or component thereof that is furthest from the clinician. Throughout the drawings, the arrows within and adjacent to portions of the cooling system indicate the direction of the flow of the cooling fluid. 
     Referring now to  FIG.  1   , one exemplary embodiment of an ultrasonic surgical instrument configured for use in accordance with the present disclosure is shown generally identified by reference numeral  10 , although it is also envisioned that the aspects and features of the present disclosure be similarly incorporated into any suitable ultrasonic surgical instrument. Ultrasonic surgical instrument  10  generally includes a handle assembly  12 , an elongated body portion  14 , and a tool assembly  16 . Handle assembly  12  supports a battery assembly  18  and an ultrasonic transducer and generator assembly (hereinafter “TAG”)  20 . Handle assembly  12  includes a rotatable nozzle  22 , an activation button  24 , and a clamp trigger  26 . Battery assembly  18  and TAG  20  are each releasably secured to a central body  28  of handle assembly  12  and are removable from central body  28  to facilitate disposal of the entire device, with the exception of battery assembly  18  and TAG  20 . 
     With additional reference to  FIG.  2   , elongated body portion  14  includes a waveguide  30  which extends from handle assembly  12  to tool assembly  16  ( FIG.  1   ). A distal end of waveguide  30  defines a blade  32 , which will be discussed in further detail below. A proximal end of waveguide  30  has a threaded extension  34  for engaging TAG  20 . Waveguide  30  further includes a proximal tapered portion  30   a  and distal tapered portions  30   b  and  30   c . A series of annular abutments  31   a - d  are disposed along, e.g., machined onto, waveguide  30  at node points along waveguide  30 . 
     An inner tube  36  is positioned about waveguide  30  between proximal tapered portion  30   a  and distal tapered portion  30   b  of waveguide  30 . A distal seal member  38  is supported about waveguide  30  distally of a distal end of inner tube  36  and proximally of distal tapered portion  30   c  of waveguide  30  to provide a fluid-tight seal at the distal end of elongated body portion  14  between waveguide  30  and an inner surface of a middle tube  42 . Ultrasonic energy is isolated from transfer to middle tube  42  by inner tube  36 . A series of splines  44  are formed at the proximal end of waveguide  30 . Splines  44  engage splines (not shown) formed on an inner surface of a torque adapter  46  to rotatably secure torque adapter  46  to waveguide  30 . Torque adapter  46  also includes diametrically opposed wings  48  which are positioned in recesses (not shown) in rotatable nozzle  22  to secure torque adapter  46  to rotatable nozzle  22 . 
     With additional reference to  FIGS.  3  and  3 A , middle tube  42  is positioned about inner tube  36  and includes a distal end having a corset feature  50  and a pair of spaced clamp support arms  52 . Corset feature  50  is positioned to receive distal seal member  38  to maintain distal seal member  38  in the proper position about the distal end of waveguide  30 . Distal seal member  38  is positioned at a node point along waveguide  30 . An O-ring  40  is supported about corset feature  50  to provide a fluid-tight seal between an outer surface of middle tube  42  and an inner surface of an outer tube  66 . 
     With particular reference to  FIGS.  3  and  3 A , spaced clamp support arms  52  each define an opening  54  for pivotally receiving pivot members  56  formed on a clamp member  58  of tool assembly  16 . Clamp member  58  of tool assembly  16  is pivotal between an open position ( FIG.  3   ), wherein clamp member  58  is spaced from blade member  32 , and a closed position ( FIG.  3 A ), wherein clamp member  58  is in juxtaposed alignment with blade member  32 . Clamp member  58  is moved between the open position and the closed position in response to actuation of clamp trigger  26  ( FIG.  1   ). 
     Outer tube  66  is slidably repositionable between an advanced position and a retracted position. Upon movement of outer tube  66  from the advanced position to the retracted position, clamp member  58  is moved from the open position ( FIG.  3   ) to the closed position ( FIG.  3 A ). A proximal end of outer tube  66  includes an elongated slot  70  ( FIG.  2   ) which receives projections (not shown) of rotatable nozzle  22  ( FIG.  1   ) such that outer tube  66  is rotatably secured to, but slidable about, the projections to facilitate movement of outer tube  66  between the advanced and retracted positions. 
     Referring again to  FIG.  2   , the proximal end of outer tube  66  includes a bifurcated portion that defines an axially extending throughbore  72  that slidably receives wings  48  of torque adapter  46 . A pair of diametrically opposed windows  74  are formed in the proximal end of outer tube  66 . Windows  74  receive bosses (not shown) formed in handle assembly  12  ( FIG.  1   ) to couple outer tube  66  to handle assembly  12  ( FIG.  1   ). 
     Referring to  FIG.  4   , one embodiment of a blade cooling system  80  incorporated into ultrasonic surgical instrument  10  ( FIG.  1   ) in accordance with the present disclosure is shown including an inflow conduit  82  and a blade lumen  84 . Inflow conduit  82  is annularly defined between middle tube  42  and waveguide  30 . Blade lumen  84  is formed within and extends substantially through the length of blade  32 . Blade lumen  84  includes one or more blade inlets  84   a , e.g., one or more blade inlets  84   a  extending radially outwardly from blade lumen  84 , and a blade outlet  84   b . Blade inlet(s)  84   a  may be positioned at an anti-node point along waveguide  30  or at any other suitable position therealong. Blade outlet  84   b  is defined at the distal end of blade  32 . Blade lumen  84  is in fluid communication with inflow conduit  82  via blade inlet(s)  84   a . Blade outlet  84   b  includes an angled surface  85   b  disposed at an angle θ to the inner surface of blade lumen  84  as shown in  FIG.  5    to facilitate the outflow of fluid from blade lumen  84 . Angle θ may be in a range of about 0° to about 45°. Blade lumen  84  may have a diameter in the range of about 0.25 mm to about 0.65 mm. In embodiments, blade inlet  84   a  may have a diameter in the range of about 0.25 mm to about 1.00 mm. Other suitable configurations are also contemplated. 
     As noted above, inflow conduit  82  is defined between middle tube  42  and waveguide  30 . Alternatively or additionally, inflow conduit  82  may be defined between outer tube  66  and middle tube  42 . In such embodiments, inflow conduit  82  includes an input opening (not shown) in inner tube  36  and/or middle tube  42 , which provides fluid communication between inflow conduit  82  and blade inlet  84   a.    
     Annular abutment  31   d  is positioned within inflow conduit  82  and configured to permit a cooling fluid  89  ( FIG.  1   ) to flow through inflow conduit  82  to blade inlet  84   a . In embodiments, as opposed to defining inflow conduit  82  annularly between middle tube  42  and waveguide  30 , inflow conduit  82  may comprise one or more polyimide microtubes (or other suitable microtubes) disposed between inner tube  36  and waveguide  30  and extending proximally from the proximal end of elongated body member  14 . In such configurations, annular abutment  31   d  may include a passage (or passages) dimensioned and configured to slidably receive the one or more microtubes. 
     Referring to  FIGS.  1 - 4   , blade cooling system  80  further includes a fluid reservoir  88  in fluid communication with inflow conduit  82 . Fluid reservoir  88  may be positioned external to instrument  10 , positioned on handle assembly  12 , or positioned within handle assembly  12 . In embodiments where fluid reservoir  88  is external to instrument  10 , central body  28  of handle assembly  12  includes an inflow port  81  to provide fluid communication between fluid reservoir  88  and inflow conduit  82 . Fluid reservoir  88  is configured to hold a supply of cooling fluid  89 . Cooling fluid  89  can be any fluid capable of conductively and/or conventionally absorbing heat from a thermally conductive solid surface. Exemplary cooling fluids include but are not limited to water, saline, compressed air, compressed nitrogen, compressed oxygen, etc. 
     Blade cooling system  80  further includes a fluid control system  90  having a pump  92 . Pump  92  is configured to pump cooling fluid  89  from fluid reservoir  88  through inflow conduit  82  and blade lumen  84  such that cooling fluid  89  exits blade  32  through blade outlet  84   b . In embodiments, fluid control system  90  is selectively operated by a clinician. In some embodiments, fluid control system  90  is automatically operated by conditions of instrument  10  sensed by fluid control system  90 . Fluid control system  90  may include a plurality of sensors  94   a - d  positioned on and/or within instrument  10  to provide feedback of conditions of instrument  10 . Sensors  94   a - d  may include, for example, a blade thermocouple  94   a  configured to measure the temperature of blade  32 , a clamp sensor  94   b  ( FIG.  3   ) configured to determine the position of clamp  58  and/or the position of clamp trigger  26 , a waveguide thermocouple  94   c  configured to measure the temperature of a portion of waveguide  14 , and an activation sensor  94   d  configured to measure the position of activation button  24 . Other suitable sensors and/or combinations of sensors are also contemplated, as are any other suitable mechanisms for providing feedback and/or indicating a state, parameter, condition, etc. of a component of instrument  10  and/or the surrounding environment. 
     When pump  92  of fluid control system  90  is activated, pump  92  draws cooling fluid  89  from fluid reservoir  88  and pumps cooling fluid  89  through inflow conduit  82  and blade lumen  84 . When cooling fluid  89  is pumped through blade lumen  84 , cooling fluid  89  flows out of blade outlet  84   b  formed through the distal surface of blade  32  (see  FIGS.  3 - 3 A ). As cooling fluid  89  exits from blade outlet  84   b , cooling fluid  89  can form a mist. As angle θ of angled surface  85   b  is decreased, the misting of cooling fluid  89  decreases. As cooling fluid  89  fluid flows through blade lumen  84 , cooling fluid  89  absorbs heat from blade  32  such that blade  32  is cooled by blade cooling system  80 . Cooling fluid  89  flowing through inflow conduit  82  also absorbs heat from waveguide  30 . Fluid control system  90  regulates the amount of cooling fluid  89  that pump  92  draws from fluid reservoir  88  and pumps through blade cooling system  80  thus controlling the cooling of blade  32 . 
     Fluid control system  90  may be configured to control the cooling of blade  32  via regulating pump  92  such as, for example, by: activating pump  92  to continually pump cooling fluid  89  through blade cooling system  80 ; activating/deactivating pump  92  to pump cooling fluid  89  through blade cooling system  80  when activation button  24  ( FIG.  1   ) is depressed (actuated); activating/deactivating pump  92  to pump cooling fluid  89  through blade cooling system  80  when activation button  24  ( FIG.  1   ) is released (un-actuated); activating/deactivating pump  92  to pump cooling fluid  89  through blade cooling system  80  according to a predetermined schedule; activating/deactivating pump  92  to pump cooling fluid  89  through blade cooling system  80  once activation button  24  ( FIG.  1   ) has been depressed (actuated) for a predetermined period of time; activating/deactivating pump  92  to pump cooling fluid  89  through blade cooling system  80  once activation button  24  ( FIG.  1   ) has been released (un-actuated) for a predetermined amount of time; and/or activating/deactivating pump  92  to pump cooling fluid  89  through blade cooling system  80  based upon temperature feedback so as to maintain the temperature of blade  32  and/or waveguide  30  below a predetermined threshold temperature or within a predetermined temperature range. As described in detail below, fluid control system  90  may include sensors  94   a - d , or any other suitable mechanisms for providing feedback and/or indicating a state, parameter, condition, etc. of a component of instrument  10  and/or the surrounding environment, to facilitate controlling of pump  92 . Other control systems, mechanisms, methods, and/or protocols are also contemplated. 
     As mentioned above, in some embodiments, fluid control system  90 , together with blade cooling system  80 , may be configured to maintain blade  32  below a predetermined temperature. In such a configuration, the clinician inputs an upper temperature limit into fluid control system  90 . In embodiments, the upper temperature limit may also be preset at the time of manufacture of fluid control system  90 . Fluid control system  90  activates pump  92  when blade thermocouple  94   a  determines the temperature of blade  32  is approaching the upper temperature limit. When pump  92  is activated, pump  92  pumps cooling fluid  89  through blade cooling system  80  to prevent blade  32  from exceeding the upper temperature limit. The amount of fluid pumped through blade cooling system  80  may also be varied depending on the sensed temperature. 
     Additionally, blade  32  may be maintained within a range of predetermined temperatures. In such a configuration, the clinician inputs an upper and lower temperature limit of the range of predetermined temperatures into fluid control system  90 . Similar to the previous configuration, the upper and lower temperature limits can be preset. Fluid control system  90  activates pump  92  (or increases the rate at which fluid is pumped) when blade thermocouple  94   a  determines the temperature of blade  32  is approaching the upper temperature limit to cool or decrease the temperature of blade  32 . When fluid control system  90  determines the temperature of blade  32  is approaching the lower temperature limit, as measured by blade thermocouple  94   c , fluid control system  90  deactivates pump  92  (or decreases the rate at which fluid is pumped) stopping (or reducing) the flow of cooling fluid  89  through blade  32 . 
     Additionally or alternatively, blade cooling system  80  may be configured to cool blade  32  after a clinician has activated and deactivated blade  32 . In this configuration blade  32  is allowed to heat up when used to dissect and/or coagulate tissue, but is actively cooled via blade cooling system  10  once blade  32  is no longer in use. In such a configuration, fluid control system  90  activates pump  92  when blade thermocouple  94   a  determines the temperature of blade  32  exceeds an upper temperature limit and activation sensor  94   d  (or other suitable mechanism) determines that activation button  24  is in the released (un-actuated) position. Fluid control system  90  may deactivate pump  92  when the temperature of blade  32  reaches a lower temperature limit, or when activation button  24  is in the depressed (actuated) position. Fluid control system  90  may further include a clamp sensor  94   b  (or other suitable mechanism) to determine the position of clamp  58 , i.e. open or closed. When clamp  58  is in the open position, as determined by clamp sensor  94   b , and the temperature of blade  32  exceeds the upper temperature limit, fluid control system  90  activates pump  92 . On the other hand, when clamp  58  or the temperature of blade  32  is below the lower temperature limit, fluid control system  90  deactivates pump  92 . 
     Referring to  FIGS.  6  and  7   , another ultrasonic surgical instrument  110  is provided in accordance with the present disclosure including a waveguide  130  and incorporating a blade cooling system  180 . Ultrasonic surgical instrument  110  and blade cooling system  180  are substantially similar to ultrasonic surgical instrument  10  and blade cooling system  80  ( FIGS.  1 - 5   ), with similar elements represented by similar numerals. As such only the differences are discussed in detail below. 
     Blade cooling system  180  is a closed circuit and includes an inflow conduit  182 , a blade lumen  184 , and a return conduit  186 . Inflow conduit  182  is defined between middle tube  142  and waveguide  130 . Inflow conduit  182  is in fluid communication with blade lumen  184  via one or more blade inlets  184   a  disposed at an anti-node point along waveguide  130 . A seal is disposed about or in proximity to annular abutment  131   d  to seal a distal end of inflow conduit  182 . In embodiments, annular abutment  131   d  forms a seal at the distal end of inflow conduit  182 . Blade lumen  184  is defined within and extends through blade  132 . Blade lumen  184  includes blade inlet(s)  184   a  and a blade outlet  184   b . Blade inlet(s)  184   a  is proximal of the seal of, about, or in proximity to annular abutment  131   d  to permit the inflow of fluid from inflow conduit  182  into blade inlet(s)  184   a . Blade lumen  184  extends distally from blade inlet  184   a  such that blade lumen  184  extends substantially along the length of blade  132  in a parallel orientation to the longitudinal axis. A distal section  184   c  of blade lumen  184  is orthogonal to the longitudinal axis of blade  132  (or otherwise curved, bent, or angled) such that distal section  184   c  of blade lumen  184  is parallel (or otherwise curved, bent, or angled) to a distal surface  132   a  of blade  132 . Distal section  184   c  is spaced-apart from distal surface  132   a  of blade  132  and distal section  184   c  defining a gap  187  therebetween. Gap  187  may be in the range of about 0.005 to about 0.025 mm; however, larger and smaller dimensions for gap  187  are also contemplated. Blade lumen  184  returns along a length of blade  132  from distal section  184   c  to blade outlet  184   b . Blade outlet  184   b  may be disposed at an anti-node point along waveguide  130  or any other suitable position therealong and is disposed in fluid connection with return conduit  186 , e.g., via positioning of blade outlet  184   b  proximally of distal seal member  138  and distally of the seal of, about, or in proximity of annular abutment  131   d . Return conduit  186  is defined between middle tube  142  and outer tube  166  and is in fluid communication with blade outlet  184   b  through a slot  142   a  of middle tube  142 . An O-Ring  140  is positioned distal to slot  142   a  between middle tube  142  and outer tube  166  to seal the distal end of return conduit  186 . 
     Similar to inflow conduit  82  described above ( FIG.  4   ), inflow conduit  182  and return conduit  186  may alternatively be formed from polyimide microtubes. For example, inflow conduit  182  can be a polyimide microtube disposed between middle tube  142  and waveguide  130  and in fluid communication with blade inlet  184   a  and return conduit  186  can be a polyimide microtube in fluid communication with blade outlet  184   b  passing through slot  142   a  of middle tube  142  and extending proximally through a channel disposed between outer tube  166  and middle tube  142 . Moreover, as shown in  FIGS.  8  and  8 A , in embodiments where microtubes are provided, conduits  182 ,  186  of polyimide microtubes may be disposed within the same channel, e.g., between the middle tube  142  and the waveguide  130 , and blade outlet  184   b  can be proximal to annular abutment  31   d.    
     In embodiments, return conduit  186  is in fluid communication with inflow conduit  182  such that the fluid continually circulates through blade cooling system  180 . In some embodiments, blade cooling system  180  includes a fluid control system  190  having a pump  192  positioned between return conduit  186  and inflow conduit  182  to circulate cooling fluid  189  through blade cooling system  180 . Pump  192  can be disposed within central body  128  of handle assembly  112 . In certain embodiments, blade cooling system  180  further includes a fluid reservoir  188  positioned between and in fluid communication with return conduit  186  and inflow conduit  182 . Fluid reservoir  188  can be disposed within central body  128  or external to instrument  110 . When fluid reservoir  188  is disposed external to instrument  110 , central body  128  includes an inflow port  182   a  and a return port  186   a  in fluid communication with inflow conduit  182  and return conduit  186 , respectively. Fluid control system  190  may also include a sensors  194   a - d  similar to the sensors  94   a - d  discussed above with respect to instrument  10  ( FIGS.  1 - 5   ) and may also include a return conduit thermocouple  194   e  ( FIG.  7   ) configured to measure the temperature of cooling fluid  189  in return conduit  186 . 
     Blade cooling system  180  of instrument  110  functions substantially similar to blade cooling system  80  of instrument  10 . However, as blade cooling system  180  is a closed system, cooling fluid  189  flows through inflow conduit  182  through blade lumen  184  and returns through return conduit  186  before recirculating through blade cooling system  180 . As cooling fluid  189  flows through blade cooling system  180 , cooling fluid  189  absorbs heat from waveguide  130  and/or blade  132 . The absorbed heat may be released to the surrounding environment through an outer surface of outer tube  166 , central portion  128  of housing assembly  112 , and/or from fluid reservoir  188 . Additionally, fluid reservoir  188  may be actively cooled to facilitate cooling of the fluid  189  returned from blade  132  prior to recirculation. 
     Referring to  FIGS.  9 - 10   , another ultrasonic surgical instrument  210  is provided in accordance with the present disclosure including a waveguide  230  and incorporating a blade cooling system  280 . Ultrasonic surgical instrument  210  and blade cooling system  280  are substantially similar to ultrasonic surgical instrument  10  and blade cooling system  80  ( FIGS.  1 - 5   ), with similar elements represented by similar numerals. As such only the differences are discussed in detail below. 
     Blade cooling system  280  includes a blade lumen  284  and a cooling conduit  286 . It is envisioned that the distal end  284   a  of blade lumen  284  is spaced from a distal surface  232   a  of blade  232  by a gap  287 . Gap  287  may be in the range of about 0.005 to about 0.025 mm; however, larger and smaller dimensions for gap  287  are also contemplated. Blade lumen  284  extends proximally within and substantially along the length of blade  232  to a blade outlet  284   b . Cooling conduit  286  is disposed within blade lumen  284  and a longitudinal slot  266   a  in the outer surface of outer tube  266  along a length of an elongated body portion  214  (see  FIG.  9 A ). A proximal end  286   b  of cooling conduit  286  may be sealed or may be configured to couple to a fluid reservoir similarly as described above with respect to previous embodiments. A distal end  286   a  of cooling conduit  286  is proximate to distal end  284   a  of blade lumen  284 . Cooling conduit  286  can be a polyimide tube. 
     Referring to  FIG.  11   , a blade cooling system  380  is provided in accordance with the present disclosure incorporated within a waveguide  330  and blade  332 . Waveguide  330  and blade cooling system  380  are substantially similar to waveguide  30  and blade cooling system  80  ( FIGS.  1 - 5   ), with similar elements represented by similar numerals, and may be used with any of ultrasonic instruments  10 ,  110 , and  210 . It is also contemplated that blade cooling system  380  can be used with other suitable ultrasonic instruments. As such only the differences are discussed in detail below. 
     Blade cooling system  380  is a closed heat pipe system and includes a blade lumen  384  and a cooling conduit  386 . It is envisioned that the distal end  384   a  of blade lumen  384  is spaced from a distal surface  332   a  of blade  332  by a gap  387 . Gap  387  may be in the range of about 0.005 to about 0.025 mm; however, larger and smaller dimensions for gap  387  are also contemplated. Blade lumen  384  extends proximally within and substantially along the length of blade  332  to a blade outlet  384   b . Blade outlet  384   b  is in fluid communication with cooling conduit  386 , i.e., blade lumen  384  and cooling conduit  386  cooperate to define a heat pipe extending through and between at least a portion of both waveguide  330  and blade  332 . Cooling conduit  386  is disposed within waveguide  330 . Cooling conduit  386  includes a conduit opening  386   a  at a distal end of waveguide  330  in fluid communication with blade outlet  384   b  and a proximal or closed end  386   b  is proximate to the proximal end of waveguide  330 . Closed end  386   b  of cooling conduit  386  is sealed. In embodiments, the inner wall of the blade lumen  384  and/or cooling conduit  386  includes a wick structure (not shown) configured to exert capillary pressure on the cooling fluid when the cooling fluid is in a liquid phase. The wick structure may be a series of grooves parallel to the longitudinal axis of waveguide  330 . Cooling conduit  386  is constructed of a material with a high thermal efficiency, e.g., copper, polyimide micro tubing, etc. 
     In use, as the temperature of blade  332  increases, cooling fluid  389  which is disposed within blade lumen  384  absorbs heat from blade  332  transitioning cooling fluid  389  from a liquid phase to a vapor phase. Cooling fluid  389  in the vapor phase travels through blade cooling system  380  from blade lumen  384  to cooling conduit  386  where the cooling fluid  389  releases the absorbed heat through the surface of cooling conduit  386 , i.e., waveguide  330 , to the surrounding environment. As cooling fluid  389  releases the absorbed heat, cooling fluid  389  returns from the vapor phase to the liquid phase. When cooling fluid  389  returns to the liquid phase, cooling fluid  389  returns to blade lumen  384  to repeat the cycle. As can be appreciated, the distal-to-proximal movement of the vapor and the proximal-to-distal movement of the liquid can be facilitated by gravity when in use as blade  332  is generally angled downwardly relative to waveguide  330  into the surgical site. 
     The present disclosure also provides methods of manufacturing ultrasonic surgical instruments including cooling systems, such as those instruments detailed above. The method may include fabricating a waveguide, fabricating two halves of a blade separated along the longitudinal axis of the blade, cutting a portion of a conduit in each half of the blade, welding the two halves of the blade into a blade, and welding the blade to the distal end of the waveguide. As such, the conduits extending through the blade, as detailed above, can be readily formed to a desired configuration. 
     Cutting a portion of the conduit in each half of the blade may particularly include cutting a half-cylindrical channel along the length of the blade half including an opening in the outer surface of the blade and at the distal end of the blade. Blade  32  ( FIG.  4   ) may be manufactured in this manner. Alternatively, to achieve blade  132  ( FIG.  7   ), the cutting a portion of the conduit in each half of the blade includes cutting a half-cylindrical channel along the length of the blade half from a first opening in the outer surface of the blade, along the length of the blade towards the distal end, continuing the channel substantially parallel to the distal end of the blade defining a gap between the channel and the distal end of the blade, continuing the channel back along the length of the blade towards the proximal end of the blade, continuing the channel out a second opening in the outer surface of the blade substantially opposing the first opening. The cutting in either of the above embodiments may be accomplished by laser cutting or etching. 
     Welding the two halves of the blade into a blade may include aligning the two halves of the blade such that the half-cylindrical channels in each blade are positioned adjacent to each other to form a continuous cylindrical conduit within the blade. Welding the two halves may include laser welding the two halves of the blade together. Welding the blade to the waveguide may include laser welding the proximal end of the blade to the distal end of the waveguide. 
     In embodiments, the distal end of the waveguide includes threads configured to cooperate with threads of the blade to secure the waveguide to the blade. In some embodiments, the blade lumen is formed by drilling through a portion of the blade such that the distal end of the blade remains closed and does not require welding. Electrical Discharge Machining (EDM) may alternatively be used to make the blade lumen, followed by the distal end of the blade being welded shut. Other suitable manufacturing methods are also contemplated. 
     Referring now to  FIGS.  12 - 14   , another embodiment of an ultrasonic surgical instrument configured for use in accordance with the present disclosure is shown generally identified by reference numeral  410 . Ultrasonic surgical instrument  410  is similar to and may include any of the aspects and/or features of any of the instruments detailed above. Thus, for purposes of brevity, only the differences between ultrasonic surgical instrument  410  and the above instruments will be detailed below, while similarities will be summarily described or omitted entirely. 
     Ultrasonic surgical instrument  410  generally includes a handle assembly  412 , an elongated body portion  414 , a tool assembly  416  having a blade  432 , and a blade cooling system  480 . Blade cooling system  480  has a fluid reservoir  488  that may be separate from ultrasonic surgical instrument  410  (as shown), on handle assembly  412 , or within handle assembly  412 . Fluid reservoir  488  is configured to hold a supply of cooling fluid  489 , which can be any suitable fluid such as those detailed above. 
     Blade cooling system  480  further includes a fluid control system  490  having a pump  492  configured to pump cooling fluid  489  from fluid reservoir  488  through blade  432  of ultrasonic surgical instrument  410  via a cooling inflow conduit  482 . Cooling fluid  489  absorbs heat from blade  432  of ultrasonic surgical instrument  410  and is returned through a cooling return conduit  486 . Heated cooling fluid  489  may be returned to fluid reservoir  488 , thus forming a closed-loop system, or may be released into a separate return reservoir (not shown) as part of an open-loop system. 
     As shown in  FIGS.  12  and  12 A , cooling inflow and return conduits  482 ,  486  are disposed on the outer surface of elongated body portion  414  of ultrasonic surgical instrument  410  and extend substantially along the length thereof. Positioning conduits  482 ,  486  on the exterior of elongated body portion  414  helps inhibit the heating of waveguide  430  ( FIG.  13   ) and other internal components extending through elongated body potion  414  via the heated fluid returning through the return conduit  486 . A proximal end  482   a  of inflow conduit  482  is configured to couple to pump  492  via handle assembly  412  (as shown) or separately therefrom and a proximal end  486   a  of return conduit  486  is configured to couple to fluid reservoir  488  (or a separate return fluid reservoir (not shown)) via handle assembly  412  (as shown) or separately therefrom. Distal and proximal apertures  466   a ,  466   b , respectively, are defined within elongated body portion  414  to enable conduits  482 ,  486  to exit and enter elongated body portion  414 , respectively. However, it is also contemplated that ultrasonic surgical instrument  410  be configured with conduits  482 ,  486  extending within elongated body portion  414 . 
     Referring to  FIGS.  13  and  14   , blade  432  defines a blade lumen  434  that is formed within and extends substantially along the length of blade  432 . Blade lumen  434  may be coaxial with or extend in a parallel orientation relative to a longitudinal axis defined by blade  432 . Blade lumen  434  defines a closed distal end. Inflow conduit  482  and return conduit  486  enter blade lumen  434  through a blade output  460  defined towards the proximal end of blade lumen  434 . A seal is formed about blade output  460  and around inflow and outflow conduits  482 ,  486  to inhibit the escape of fluid thereform. The seal may be affixed to the blade output  460  and conduits  482 ,  486 . Alternatively, the seal may be releasably attached to blade output  460  permitting access to blade lumen  434 . Blade output  460  may be positioned at an anti-node point along waveguide  430  of ultrasonic surgical instrument  410  or at any other suitable position therealong. Inflow conduit  482  is disposed within and extends distally through blade lumen  434 . Return conduit  486  is disposed within the proximal end of blade lumen  434 . Inflow conduit  482  has a smaller diameter than blade lumen  434  leaving an annular gap  436  ( FIG.  14   ) between the inner surface of blade  432  defining blade lumen  434  and the outer surface of inflow conduit  482 . Blade lumen  434  may have a diameter in the range of about 0.25 mm to about 0.65 mm; however, other suitable configurations are also contemplated. During operation, cooling fluid  489  is pumped or otherwise circulated distally through inflow conduit  482 , exits a distal end of inflow conduit  482  at the distal end of blade lumen  434 , and travels proximally back through blade lumen  434  within annular gap  436 , ultimately being received by return conduit  486 , e.g., under suction force or under urging from the pumped inflowing fluid. Inflow and return conduits  482 ,  486  may comprise one or more polyimide microtubes (other suitable microtubes, or may be formed in any other suitable fashion). 
     Referring again to  FIGS.  12 - 14   , the fluid control system  490  is similar to the fluid control systems described above except for the relative positions of inflow and return conduit  482 ,  486  and the flow path of cooling fluid  489 . When pump  492  of fluid control system  490  is activated, pump  492  draws cooling fluid  489  from fluid reservoir  488  and pumps cooling fluid  489  through inflow conduit  482  into the distal end of blade lumen  434 . As cooling fluid  489  fluid flows proximally back through blade lumen  434  within annular gap  436 , cooling fluid  489  absorbs heat from blade  432  such that blade  432  is cooled. The cooling fluid  489  is then pushed and/or pulled through the return conduit  486  into fluid reservoir  488 , creating a closed circuit, or pushed and/or pulled into a return reservoir (not shown) creating an open circuit. Fluid control system  490  regulates the amount of cooling fluid  489  that pump  492  draws from fluid reservoir  488  and pumps through blade cooling system  480 , thus controlling the cooling of blade  432 . Control may be performed similarly as detailed above with respect to the previous embodiments, or in any other suitable fashion. 
     Referring to  FIG.  15   , another ultrasonic surgical instrument  510  is provided in accordance with the present disclosure incorporating a blade cooling system  580 . Ultrasonic surgical instrument  510  is similar to ultrasonic surgical instrument  410  ( FIGS.  12 - 14   ), except for the configuration of blade cooling system  580 , as detailed below. 
     Blade cooling system  580  includes an inflow conduit  582 , a return conduit  586 , an inflow pump  592 , and a return pump  594 . Inflow conduit  582  and return conduit  586  may be formed from polyimide microtubes (or in any other suitable manner). 
     Similar to the cooling systems described above, return conduit  586  is in fluid communication with inflow conduit  582  such that the fluid continually circulates through blade cooling system  580 . Blade cooling system  580  includes a fluid control system  590  having an inflow pump  592  positioned between a fluid reservoir  588  and inflow conduit  582  and a return pump  594  positioned between return conduit  586  and fluid reservoir  588 . Alternatively, return pump  594  may be positioned between return conduit  584  and a separate return reservoir (not shown) to define an open-loop system. Inflow and return pumps  592 ,  594  can be externally disposed (as shown), or may be disposed within central body  528  of handle assembly  512 . Fluid control system  590  may also include sensors (not shown) similar to the sensors discussed above to enable feedback-based control. 
     Similar to the fluid control systems detailed above, when inflow pump  592  of fluid control system  590  is activated, inflow pump  592  draws cooling fluid  589  from fluid reservoir  588  and pumps cooling fluid  589  through inflow conduit  582  and the blade of ultrasonic surgical instrument  510 . As cooling fluid  589  fluid flows through blade lumen (not shown) of the blade, return pump  594  is activated to draw the heated cooling fluid  589  from the blade lumen (not shown), through the return conduit  586 , and into the fluid reservoir  588  or alternatively the return reservoir (not shown). The inflow and return pumps  592 ,  594  may operate simultaneously. However, the operation times of pumps  592 ,  594  may also be staggered. Fluid control system  590  may include sensors (not shown), or any other suitable mechanisms for providing feedback and/or indicating a state, parameter, condition, etc. of a component of surgical instrument  510  and/or the surrounding environment, to facilitate controlling of inflow and return pumps  592 ,  594 . Fluid control system  490  ( FIG.  12   ) may similarly include such features. Other control systems, mechanisms, methods, and/or protocols are also contemplated for either or both embodiments. 
     While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Any combination of the above embodiments is also envisioned and is within the scope of the claimed invention. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.