Patent Publication Number: US-11648026-B2

Title: Devices, systems, and methods for cooling a surgical instrument

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. patent application Ser. No. 15/155,953, filed on May 16, 2016, the entire contents of which are incorporated by reference herein. 
    
    
     FIELD 
     The present disclosure relates to devices, systems, and methods for cooling a surgical instrument and, in particular, to devices, systems, and methods for cooling a surgical instrument and systems and methods for controlling the same. 
     BACKGROUND 
     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 to treat, e.g., coagulate and/or cut, tissue. 
     Ultrasonic surgical instruments, for example, typically include a waveguide having a transducer coupled thereto at a proximal end of the waveguide and an end effector disposed at a distal end of the waveguide. The waveguide transmits ultrasonic energy produced by the transducer to the end effector for treating tissue at the end effector. The end effector may include a blade, hook, ball, shears, etc., and/or other features such as one or more jaws for grasping or manipulating tissue. During use, the waveguide and/or end effector of an ultrasonic surgical instrument can reach temperatures greater than 200° C. 
     It would therefore be desirable to provide devices, systems, and methods for cooling a surgical instrument and controlling cooling of the same. 
     SUMMARY 
     As used herein, the term “distal” refers to the portion that is being described which is further from a user, while the term “proximal” refers to the portion that is being described which is closer to a user. 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. 
     A surgical system provided in accordance with aspects of the present disclosure includes a surgical instrument defining an input and an output, and a cooling module operably coupled to the input and output of the surgical instrument. The cooling module includes a fluid reservoir retaining a conductive cooling fluid, a pump assembly, first and second electrodes, and a controller. The pump assembly is operably coupled to the fluid reservoir and configured to pump the conductive cooling fluid along a flowpath from the fluid reservoir, into the input of the surgical instrument, through at least a portion of the surgical instrument, out the output of the surgical instrument, and back to the fluid reservoir. The first and second electrodes are disposed at first and second spaced-apart positions along the flowpath and are configured to sense an electrical property of the conductive cooling fluid at the first and second positions. The controller is configured to determine an impedance of the conductive cooling fluid between the first and second positions based upon the sensed electrical properties of the first and second electrodes. 
     In an aspect of the present disclosure, the surgical instrument includes an ultrasonic waveguide having a blade defined at the distal end thereof. In such aspects, the flowpath may extend at least partially through the blade. The surgical instrument may further include an ultrasonic transducer coupled to the ultrasonic waveguide and configured to energize the blade for treating tissue therewith. 
     In another aspect of the present disclosure, the surgical system further includes a generator configured to supply energy to the surgical instrument. The generator may be disposed on the surgical instrument or may be spaced-apart therefrom. 
     In yet another aspect of the present disclosure, the surgical instrument further includes an activation button operably coupled to the generator and including a first activated position and a second activated position for activating the surgical instrument in a first mode and a second mode. In such aspects, the first and second electrodes may be operably coupled to the generator through the activation button. 
     In still another aspect of the present disclosure, the first position is disposed adjacent a distal end of the surgical instrument and/or the second position is disposed adjacent the cooling module. 
     In still yet another aspect of the present disclosure, the controller is configured to determine a temperature of the surgical instrument based upon the determined impedance. Additionally or alternatively, the controller is configured to determine whether the flowpath has been properly primed with the conductive cooling fluid based upon the determined impedance. Additionally or alternatively, the controller is configured to at least one of start or stop the pump assembly based upon the determined impedance. Additionally or alternatively, the controller is configured to control the pump assembly based upon the determined impedance. Additionally or alternatively, the controller is configured to determine the presence of at least one of air bubbles, a blockage, or mechanical damage to the surgical instrument based upon the determined impedance. 
     In another aspect of the present disclosure, the cooling module is disposed on the surgical instrument. Alternatively, the cooling module may be spaced-apart from the surgical instrument. 
     A method for cooling a surgical instrument provided in accordance with aspects of the present disclosure includes detecting an electrical property of a conductive cooling fluid at a first position along a flowpath from a fluid reservoir, into an input of a surgical instrument, through at least a portion of the surgical instrument, out an output of the surgical instrument, and back to the fluid reservoir. The method further includes detecting an electrical property of the conductive cooling fluid at a second position along the flowpath and determining an impedance of the conductive cooling fluid between the first and second positions based upon the detected electrical properties at the first and second positions. 
     In an aspect of the present disclosure, the method further includes determining whether the flowpath has been properly primed with the conductive cooling fluid based upon the determined impedance. Additionally or alternatively, the method may further include at least one of initiating or stopping flow of the conductive fluid along the flowpath based upon the determined impedance. Additionally or alternatively, the method may further include determining at least one of air bubbles, a blockage, or mechanical damage to the surgical instrument based upon the determined impedance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects and features of the present disclosure are described hereinbelow with reference to the drawings wherein like numerals designate identical or corresponding elements in each of the several views: 
         FIG.  1    is a perspective view of a surgical system provided in accordance with the present disclosure including an endoscopic ultrasonic surgical instrument, a cooling module, and a cooling system incorporated therein; 
         FIG.  2 A  is an enlarged, perspective view of the area of detail indicated as “ 2 A” in  FIG.  1   ; 
         FIG.  2 B  is an enlarged, perspective view of the area of detail indicates as “ 2 B” in  FIG.  1   ; 
         FIG.  3    is an enlarged, perspective view of the distal end of the surgical instrument of  FIG.  1   ; 
         FIG.  4    is a schematic illustration of the surgical system of  FIG.  1    depicting the internal operating components of the cooling system thereof; 
         FIG.  5    is an exploded, perspective view of another surgical system provided in accordance with the present disclosure including a handheld endoscopic ultrasonic surgical instrument ultrasonic surgical instrument including an on-board cooling module and having a cooling system incorporated therein; 
         FIG.  6    is a side, cross-sectional view of an open ultrasonic surgical instrument provided in accordance with the present disclosure and including a cooling system configured for use therewith; 
         FIG.  7    is an enlarged, top, cross-sectional view of the blade of the surgical instrument of  FIG.  6   ; 
         FIG.  8 A  is an enlarged, side, cross-sectional view of a portion of the surgical instrument of  FIG.  6   , illustrating routing of the cooling conduits into and through the waveguide of the surgical instrument; 
         FIG.  8 B  is a greatly enlarged, side, cross-sectional view of a portion of the surgical instrument of  FIG.  6   , illustrating the routing of the cooling conduits through the waveguide of the surgical instrument; 
         FIG.  9    is an enlarged, side view illustrating coupling of the cooling conduits of the surgical instrument of  FIG.  6    with a tube splitter of the surgical instrument to enable the supply and return of cooling fluid from the surgical instrument; 
         FIG.  10 A  is a flow diagram depicting a method of cooling a surgical instrument provided in accordance with the present disclosure; 
         FIG.  10 B  is a flow diagram depicting another method of cooling a surgical instrument provided in accordance with the present disclosure; and 
         FIG.  11    is a schematic illustrating of another cooling system provided in accordance with the present disclosure, depicting the internal operating components of the cooling system. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    depicts a surgical system  10  provided in accordance with the aspects and features of the present disclosure. Surgical system  10  generally includes an endoscopic ultrasonic surgical instrument  100  and a base unit  500  that, together, incorporate a cooling system for cooling a blade  162  of an end effector assembly  160  of endoscopic ultrasonic surgical instrument  100 . Although detailed hereinbelow with respect to surgical system  10  and, more particularly, endoscopic ultrasonic surgical instrument  100  and cooling module  500  thereof, the aspects and features of the present disclosure are equally applicable for use with any other suitable surgical system, surgical instrument, and/or cooling module incorporating a cooling system. For example, the aspects and features may be provided for use in connection with a surgical system  20  including an endoscopic ultrasonic surgical instrument  1100  incorporating a cooling module  1500  thereon (see  FIG.  5   ). Further still, another surgical instrument provided in accordance with the present disclosure, open ultrasonic surgical instrument  2100  ( FIGS.  6 - 9   ), may similarly incorporate the aspects and features of the present disclosure. Obviously, different considerations apply to each particular type of system, instrument, and/or unit; however, the aspects and features of the present disclosure are equally applicable and remain generally consistent with respect to any such system, instrument, and/or unit. 
     Continuing with reference to  FIG.  1   , endoscopic ultrasonic surgical instrument  100  generally includes a disposable  102 , a transducer and generator assembly (“TAG”)  200  including a transducer  210  and a generator  220  ( FIG.  4   ), a battery  300 , and a cable  400 . Disposable  102  includes a housing  110 , a handle assembly  120 , a rotating assembly  130 , an activation button  140 , an elongated body portion  150 , and end effector assembly  160 . TAG  200  and battery  300  are releasably engagable with housing  110  of disposable  102  and, when engaged therewith, are disposed in electrical communication with one another such that power and/or control signals can be relayed between TAG  200  and battery  300  for operating instrument  100 . TAG  200  may further include an indicator  202  disposed thereon, which will be described in greater detail below. 
     Elongated body portion  150  of disposable  102  of instrument  100  includes a waveguide  152  which extends from housing  110  to end effector assembly  160 , an outer tube  154 , and an inner tube (not shown). The distal end of waveguide  152  extends distally from outer tube  154  and defines blade  162  of end effector assembly  160 , while the proximal end of waveguide  152  is operably coupled to TAG  200 . Outer tube  154  is slidably disposed about waveguide  152  and extends between housing  110  and end effector assembly  160 . Rotating assembly  130  is rotatably mounted on housing  110  and operably coupled to elongated body portion  150  so as to enable rotation of elongated body portion  150  and end effector assembly  160  relative to housing  110 . 
     End effector assembly  160  is disposed at a distal end of elongated body portion  150  and includes blade  162  and a jaw member  164 . Jaw member  164  is pivotable relative to blade  162  between an open position, wherein jaw member  164  is spaced-apart from blade  162 , and a closed position, wherein jaw member  164  is approximated relative to blade  162  in juxtaposed alignment therewith for clamping tissue therebetween. Jaw member  164  is operably coupled to the distal end of outer tube  154  and the proximal end of outer tube  154  is operably coupled to movable handle  122  of a handle assembly  120 , such that jaw member  164  is movable between the open position and the closed position in response to actuation of movable handle  122  of handle assembly  120  relative to fixed handle portion  124  thereof. 
     Blade  162  is configured to serve as an active or oscillating ultrasonic member that is selectively activatable to ultrasonically treat tissue grasped between blade  162  and jaw member  164 . TAG  200  is configured to convert electrical energy provided by battery  300  into mechanical energy that is transmitted along waveguide  152  to blade  162 . More specifically, TAG  200  is configured to convert the electrical energy provided by battery  300  into a high voltage alternating current (AC) waveform that drives the transducer (not shown) of TAG  200 . Activation button  140  is disposed on housing  110  of disposable  102  and is electrically coupled between battery  300  and TAG  200 . Activation button  140  is selectively activatable in a first position and a second position to supply electrical energy from battery  300  to TAG  200  for operating instrument  100  in a low-power mode of operation and a high-power mode of operation, respectively. 
     Referring to  FIGS.  1 - 3   , cooling inflow and return conduits  172 ,  174  extend from cooling module  500 , through housing  110 , and at least partially through outer tube  154  of elongated body portion  150  substantially along the length thereof. Proximal ends  173   a ,  175   a  of inflow and return conduits  172 ,  174 , respectively, are operably coupled to cooling module  500 , as detailed below (see also  FIG.  4   ). 
     With particular reference to  FIG.  3   , distal ends  173   b ,  175   b  of inflow and return conduits  172 ,  174 , respectively, extend into waveguide  152 . More specifically, a lumen  166  is formed within waveguide  152  that extends through a portion of waveguide  152  including substantially along the length of blade  162  of waveguide. Lumen  166  defines a closed distal end. Conduits  172 ,  174  enter lumen  166  through an opening  168  defined within waveguide  152  and disposed in communication with lumen  166 . A seal (not shown) disposed within opening  168  and around inflow and return conduits  172 ,  174  is provided to inhibit the escape of fluid thereform. Inflow conduit  172  is disposed within and extends distally through lumen  166 . Return conduit  174  is disposed within the proximal end of lumen  166 , although the above-detailed configuration of inflow and return conduits  172 ,  174  may be reversed. Inflow conduit  172  has a smaller diameter than lumen  166  leaving an annular gap  169  therebetween to permit the return of fluid to return conduit  174 . As such, during cooling, fluid, e.g., water, saline, etc., is pumped through inflow conduit  172 , exits a distal end of inflow conduit  172  at the distal end of lumen  166 , and travels proximally back through lumen  166  within annular gap  169 , ultimately being received by return conduit  174  for return to cooling module  500  ( FIG.  1   ). Inflow and return conduits  172 ,  174  are at least partially formed from polyimide tubing. However, as it has been found that the portion of inflow conduit  172  that extends distally through lumen  166  may be subject to delamination and, as a flow, may block the flow of fluid during use. As such, in embodiments, the portion of inflow conduit  172  that extends distally through lumen  166  is formed from stainless steel or other material suitable to withstand high temperatures. Further, in embodiments where blade  162  is curved, the portion of inflow conduit  172  that extends distally through lumen  166  is likewise curved so as not to rub on the interior surface of blade  162 . 
     Referring to  FIG.  4   , cooling module  500  includes an input port  510 , a pump assembly  520 , a controller  530 , and a user interface  540 . Input port  510  enables operable coupling of cable  400  with cooling module  500 . More specifically, input port  510  includes an inflow conduit receptacle  512 , a return conduit receptacle  514 , and one or more electrical receptacles  516 . Inflow conduit receptacle  512  operably couples inflow conduit  172  with pump assembly  520  upon engagement of cable  400  with cooling module  500 , return conduit receptacle  514  operably couples return conduit  174  with pump assembly  520  upon engagement of cable  400  with cooling module  500 , and the electrical receptacles  516  operably couple TAG  200  with controller  530 , via wires  410 , upon engagement of cable  400  with cooling module  500 . Inflow and return conduit receptacles  512 ,  514  each include one or more sensors  513 ,  515 , respectively, associated therewith for sensing the temperature of fluid flowing therethrough, the flow rate of fluid therethrough, and/or the presence of gas bubbles flowing therethrough, as detailed below. 
     Pump assembly  520  includes a fluid reservoir  522  and a pump  524  and is coupled between inflow conduit  172  and return conduit  174 . Fluid reservoir  522  stores fluid to be circulated through conduits  172 ,  174  and lumen  166  to cool blade  162  of end effector assembly  160  (see  FIG.  3   ) after use. In some embodiments, fluid reservoir  522  may be configured to regulate the temperature of the fluid retained therein. Further, instead of a closed system utilizing fluid reservoir  522 , an open system may be provided wherein fluid to be circulated is received from an external fluid source (not shown), and fluid returning is output to a drain or return reservoir (not shown). 
     Pump  524  is configured as a pull-pump, wherein pump  524  operates to pull fluid through conduits  172 ,  174  and lumen  166 . A pull-pump configuration is advantageous in that pressure build-up in push-pump configurations, e.g., due to an obstruction along the fluid flow path, is avoided. However, in some embodiments, pump  524  may be configured as a push-pump. Pump  524  may be a peristaltic pump, or any other suitable pump. 
     Continuing with reference to  FIG.  4   , controller  530  of cooling module  500  includes a processor  532  and a memory  534  storing instructions for execution by processor  532 . Controller  530  is coupled to pump assembly  520 , sensors  513 ,  515 , TAG  200  (via wires  410  extending through cable  400 ), and user interface  540 . Controller  530  may be configured to implement the method of  FIG.  10 A or  10 B  so as to instruct pump assembly  520  to turn pump  524  ON or OFF, to thereby initiate or stop blade cooling, based at least upon feedback received from sensors  513 ,  515 , TAG  200 , or other received feedback. As detailed below, controller  532  may be configured so as to instruct pump assembly  520  to turn OFF pump  524  where sensor  515  indicates a sufficiently low temperature of fluid returning from return conduit  174 . The temperature of blade  162  ( FIG.  3   ) of end effector assembly  160  may be extrapolated from the temperature of fluid returning from fluid conduit  174 , or the temperature difference between the fluid entering inflow conduit  172  and that returning from return conduit  174 , and, accordingly, pump  524  may be turned OFF upon blade  162  reaching a sufficiently cool temperature, e.g., below about 60° C. (or other suitable temperature threshold), as indicated by a sufficiently low return fluid temperature or sufficiently small temperature differential. As an alternative to sensors  513 ,  515  sensing temperature at input port  510 , temperature sensors may be incorporated into pump assembly  520  for similar purposes as noted above. Further, in embodiments, a thermocouple  167  ( FIG.  4   ) or other suitable temperature sensor may additionally or alternatively be incorporated into blade  162  (see, for example, thermocouple  2173  ( FIG.  7   )) to enable the sensing of temperature at blade  162 . 
     Controller  530 , as also detailed below with respect to  FIGS.  10 A and  10 B , may additionally or alternatively instruct pump assembly  520  to turn OFF pump  524  or disable the entire system where sensor  513  and/or sensor  515  indicates an error. Such errors may include, for example, where sensor  513  and/or sensor  515  detects a flow rate through inflow conduit  172  and/or return conduit  174  below a threshold flow rate, and/or where sensor  515  detects gas bubbles, or a gas bubble volume greater than a threshold volume, returning from return conduit  174 . Reduced flow rate and/or the presence of gas bubbles (or a greater volume of gas bubbles) may be an indication of a blockage or leak within the fluid flow path or damage to one of the conduits  172 ,  174  and, thus, the circulation of fluid is stopped by turning OFF pump  524  when such is detected. As noted above, in embodiments, rather than just turning OFF pump  524 , the entire system is disabled, thereby inhibiting further use permanently or until the error or problem is remedied. 
     Controller  530  may further be configured, as also detailed below with respect to  FIGS.  10 A and  10 B , to output an appropriate signal to user interface  540  and/or indicator  202  of TAG  200  to alert the user that blade cooling is in effect, e.g., that pump  524  is ON, that an error, e.g., a blockage or leakage, has occurred, and/or that blade  162  ( FIG.  3   ) has been sufficiently cooled and is ready for further use. User interface  540  and/or indicator  202  may provide such an alert in the form of audible, visual, and/or tactile output. 
     Controller  530  may, additionally or alternatively, as also detailed below with respect to  FIGS.  10 A and  10 B , be configured to communicate with TAG  200  to determine whether endoscopic ultrasonic surgical instrument  100  is in use, e.g., whether activation button  140  is actuated such that ultrasonic energy is being supplied to blade  162  (see  FIG.  1   ), and to control pump assembly  520  in accordance therewith. More specifically, controller  530  may instruct pump assembly  520  to turn OFF pump  524  when endoscopic ultrasonic surgical instrument  100  is in use. Once use is complete, pump  524  may be turned ON for a pre-determined time, until blade  162  has been sufficiently cooled, until an error is detected, or until endoscopic ultrasonic surgical instrument  100  is once again put into use. 
     Controller  530  may further communicate with TAG  200  to control the cooling system and/or determine whether the cooling system is operating normally based on the frequency of the transducer  210  and/or waveguide  152  ( FIG.  3   ). Thus, TAG  200  provides, e.g., via wires  410 , the frequency of the transducer  210  and/or waveguide  152  ( FIG.  3   ) to the controller  530 . This frequency information is useful in that it is indicative of the state of the system. More specifically, it has been found that during use, e.g., during tissue treatment, the frequency decreases, while, upon deactivation and release of tissue, the frequency increases. It has further been found that, if waveguide  152  is cooled shortly after deactivation and release of tissue, the frequency increases at a significantly greater rate as compared to an un-cooled waveguide  152 . Thus by monitoring the rate of change in frequency, e.g., by monitoring deviation of the rate of change relative to a threshold value or threshold range, controller  530  can determine whether the cooling system is working to effectively cool waveguide  152 , or whether cooling is ineffective or inoperable. Such may be used in addition to or in place of temperature sensors. For example, the frequency information may be used, in conjunction with the flow rate information from sensors  513 ,  515 , to determine whether cooling is working properly, based upon the flow rates and frequency rate of change, without the need to directly monitor temperature. 
     Turning now to  FIG.  5   , surgical system  20  is similar to surgical system  10  ( FIG.  1   ) and generally includes an endoscopic ultrasonic surgical instrument  1100  and a cooling module  1500 . However, rather than being coupled via a cable  400  as with endoscopic ultrasonic surgical instrument  100  and cooling module  500  ( FIG.  1   ), instrument  1100  includes cooling module  1500  disposed thereon, e.g., formed as part of disposable  1102  or releasably mounted thereon. 
     Instrument  1100  generally includes a disposable  1102 , a transducer and generator assembly (“TAG”)  1200  including a transducer  1210  and a generator  1220 , and a battery  1300 . Disposable  1102  includes a housing  1110 , a handle assembly  1120 , a rotating assembly  1130 , an activation button  1140 , an elongated body portion  1150 , and an end effector assembly  1160 , each of which are similar to the corresponding components of instrument  100  ( FIG.  1   ), detailed above. TAG  1200  and battery  1300  are releasably engagable with housing  1110  of disposable  1102  and, when engaged therewith, are disposed in electrical communication with one another such that power and/or control signals can be relayed between TAG  1200  and battery  1300  for operating instrument  1100 . TAG  1200  and battery  1300  are similar to those detailed above with respect to instrument  100  ( FIG.  1   ), except as otherwise noted below. 
     Cooling module  1500 , similar as with cooling module  500  ( FIG.  4   ), includes input ports  1512 ,  1514 , a pump assembly  1520 , and a controller  1530 . Cooling module  1500  may be permanently mounted on TAG  1200 , may be releasably engagable with both TAG  1200  and disposable  1102 , or may be permanently mounted on or within disposable  1102 . Input port  1512  enables operable coupling of pump assembly  1520  with the conduits  1172 ,  1174  of instrument  1100 , while input port  1514  enables communication between controller  1530  and generator  1220 , both of which are similar as detailed above with respect to input port  510  ( FIG.  4   ). Pump assembly  1520  and controller  1530  are also similar as detailed above, and may be configured to operate in a similar manner as mentioned above and as described in greater detail below. 
     Turning now to  FIGS.  6 - 9   , another instrument provided in accordance with the present disclosure, an open ultrasonic surgical instrument  2100 , is detailed. Open ultrasonic surgical instrument  2100  is configured to operably coupled to a table-top generator (or other remote generator) (not shown) and a cooling module (similar to cooling module  500 ). In some embodiments, the generator and cooling module are integrated into a single housing (not shown). Open ultrasonic surgical instrument  2100  generally includes two elongated shaft members  2110   a ,  2110   b , an activation button  2140 , an elongated body portion  2150 , an end effector assembly  2160 , a tube assembly  2170 , and a transducer assembly  2200 . 
     Referring to  FIG.  6   , each shaft member  2110   a ,  2110   b  includes a handle  2111   a ,  2111   b  disposed at the proximal end  2112   a ,  2112   b  thereof. Each handle  2111   a ,  2111   b  defines a finger hole  2113   a ,  2113   b  therethrough for receiving a finger of the user. One of the shaft members, e.g., shaft member  2110   a , includes a jaw member  2164  of end effector assembly  2160  extending from the distal end  2114   a  thereof. The other shaft member, e.g., shaft member  2110   b , supports elongated body portion  2150  and transducer assembly  2200  thereon. Shaft members  2110   a ,  2110   b  are pivotably coupled to one another towards the distal ends  2114   a ,  2114   b , respectively, thereof via a pivot pin  2118 . 
     Elongated body portion  2150  of shaft member  2110   b  includes a waveguide  2152  ( FIGS.  8 A and  8 B ) which extends from transducer assembly  2200  to end effector assembly  2160 , and an outer sleeve  2154  surrounding waveguide  2152 . The distal end of waveguide  2152  extends distally from outer sleeve  2154  and defines a blade  2162  of end effector assembly  2160 , while the proximal end of waveguide  2152  is operably coupled to transducer assembly  2200 . Due to the pivotable coupling of shaft members  2110   a ,  2110   b  towards the distal ends  2114   a ,  2114   b , respectively, thereof, handles  2111   a ,  2111   b  may be pivoted relative to one another to thereby pivot jaw member  2164  relative to blade  2162  between an open position, wherein jaw member  2164  is spaced-apart from blade  2162 , and a closed position, wherein jaw member  2164  is approximated relative to blade  2162  in juxtaposed alignment therewith for clamping tissue therebetween. 
     Transducer assembly  2200  is configured to convert electrical energy provided by the generator (not shown) and supplied via cable  2210 , into mechanical energy that is transmitted along waveguide  2152  to blade  2162 . Transducer assembly  2200  may be permanently affixed to elongated body portion  2150  or may be removable therefrom. Activation button  2140  is disposed on one of the shaft members, e.g., shaft member  2110   b , and, similarly as detailed above with respect to instrument  100  ( FIG.  1   ), is selectively activatable in a first position and a second position to supply electrical energy to transducer assembly  2200  for operating instrument  2100  in a low-power mode of operation and a high-power mode of operation, respectively. 
     With reference to  FIGS.  7  and  8 A- 8 B , elongated body portion  2150  is described in greater detail. As noted above, elongated body portion  2150  includes waveguide  2152  and outer sleeve  2154 . The distal end of waveguide  2152  extends distally from outer sleeve  2154  and defines blade  2162 . Waveguide is secured within outer sleeve  2154  via an O-ring  2156  ( FIGS.  8 A and  8 B ). As shown in  FIG.  7   , blade  2162  defines a curved configuration. Blade  2162  may be curved in any direction relative to jaw member  2164 , for example, such that the distal tip of blade  2162  is curved towards jaw member  2164 , away from jaw member  2164 , or laterally (in either direction) relative to jaw member  2164 . Waveguide  2152  and blade  2162  may include any of the features of waveguide  152  and blade  162  (see  FIG.  3   ), and vice versa. Further, waveguide  2152  and blade  2162  may be used with instrument  100  ( FIG.  1   ), or any other suitable instrument, and, likewise, waveguide  152  and blade  162  (see  FIG.  3   ) may be used with instrument  2100  ( FIG.  6   ), or any other suitable instrument. 
     Referring again to  FIGS.  7  and  8 A- 8 B , waveguide  2152  defines a lumen  2166  therethrough that extends into blade  2162 . Lumen  2166  is open at its proximal end, the proximal end of waveguide  2152 , and closed at its distal end, the closed distal end of blade  2162 . Connection between waveguide  2152  and transducer assembly  2200  at the proximal end of waveguide  2152  serves to close off the proximal end of lumen  2166  (see  FIG.  8 A ). Lumen  2166  defines a proximal segment  2167   a  having the open proximal end and defining a first diameter, and a distal segment  2167   b  having the closed distal end and defining a second diameter smaller than the first diameter. 
     Tube assembly  2170  ( FIG.  6   ) includes inflow and return conduits  2172 ,  2174 , respectively, and a tube splitter  2176  ( FIG.  9   ). Conduits  2172 ,  2174  are arranged such that conduit  2174  is coaxially disposed about conduit  2172 . Conduits  2172 ,  2174  enter proximal segment  2167   a  of lumen  2166 , in the above-noted coaxial arrangement, through an opening  2168  disposed in communication with lumen  2166 . Inflow conduit  2172  extends distally from return conduit  2174  through proximal segment  2167   a  of lumen  2166  into distal segment  2167   b  of lumen  2166  to the distal end of blade  2162 . Inflow conduit  2172  has a smaller diameter than distal segment  2167   b  of lumen  2166  leaving an annular gap  2169   a  therebetween to permit the return of fluid to return conduit  2174 . Return conduit  2174  does not extend into distal segment  2167   b  of lumen  2166 . Rather, a ferrule  2175  is disposed about return conduit  2174  at the distal end of proximal segment  2167   b  of lumen  2166  so as to seal an annular gap  2169   b  of lumen  2166  surrounding return conduit  2174 . As such, during cooling, fluid is pumped through inflow conduit  2172 , exits a distal end of inflow conduit  2172  at the distal end of lumen  2166 , and travels proximally back through lumen  2166  within annular gap  2169   a , ultimately being received by return conduit  2174 . Ferrule  2175  inhibits further proximal flow of cooling fluid, e.g., into annular gap  2169   b , thus ensuring that the returning fluid enters return conduit  2174 . 
     Referring to  FIG.  9   , tube splitter  2176  of tube assembly  2170  is disposed within one of the shaft members, e.g., shaft member  2110   b , of instrument  2100  (see  FIG.  6   ). Tube splitter  2176  receives the proximal ends of conduits  2172 ,  2174  which, as noted above, are coaxially disposed relative to one another, and routes the flow of fluid to/from conduits  2172 ,  2174  and respective connector tubes  2182 ,  2184 . Connector tubes  2182 ,  2184 , in turn, are coupled with a cooling module (not shown, similar to cooling module  500  ( FIG.  1   )) to enable the inflow and outflow of cooling fluid to/from conduits  2172 ,  2174 , similarly as detailed above with respect to instrument  100  ( FIG.  1   ). 
     Tube splitter  2176  generally includes a housing  2190  defining a conduit port  2192 , an interior chamber  2194 , input and output ports  2196   a ,  2196   b , respectively, and an auxiliary port  2198 . Conduit port  2192  receives the proximal ends of conduits  2172 ,  2174  which, as noted above, are disposed in coaxial relation relative to one another. Return conduit  2174  is sealingly engaged within conduit port  2192  so as to inhibit the escape of fluid therebetween. Return conduit  2174  terminates at interior chamber  2194  and is disposed in fluid communication with interior chamber  2194 . Inflow conduit  2172  extends through interior chamber  2194  and into input port  2196   a , wherein inflow conduit  2172  is sealingly engaged. Connector tube  2182  is sealingly engaged about input port  2196   a . Thus, fluid flowing through connector tube  2182  is routed into inflow conduit  2172  and, ultimately, through lumen  2166  ( FIG.  7   ) of waveguide  2152  and blade  2162  ( FIG.  7   ). Connector tube  2184  is sealingly engaged about output port  2196   b , which communicates with chamber  2194 . As such, fluid flowing through return conduit  2174  ultimately flows into chamber  2194  and, thereafter, out through output port  2196   b  to connector tube  2184 . However, it is also contemplated that inflow and return conduits  2172 ,  2174 , respectively, be reversed, and, thus, that fluid flows in the opposite direction. Auxiliary port  2198  communicates with chamber  2194  and includes a stopper  2199  sealingly engaged therein. 
     Tube splitter  2176  further includes sensors  2197   a ,  2197   b  disposed adjacent input and output portion  2196   a ,  2196   b , respectively, although sensors  2197   a    2197   b  may be positioned at any suitable position on or along instrument  2100  or the components thereof, e.g., the waveguide  2152 , blade  2162 , inflow and return conduits  2172 ,  2174 , transducer assembly  2200 , etc. (see  FIGS.  6 - 8 B ). Sensors  2197   a ,  2197   b  may be configured as thermocouples for sensing temperature and/or may otherwise be configured similar to sensors  513 ,  515  ( FIG.  4   ), respectively, to, as noted above, sense the temperature of fluid flowing therethrough, the flow rate of fluid therethrough, and/or the presence of gas bubbles flowing therethrough. 
     Referring to  FIGS.  1  and  9   , although detailed above with respect to instrument  2100  ( FIG.  6   ), tube splitter  2176  and connector tubes  2182 ,  2184  may similarly be used in connection with instrument  100 , serving to couple cooling module  500  and conduits  172 ,  174 . In such a configuration, tube splitter  2176  is mounted within housing  110  of disposable  102  so as to receive the proximal ends of conduits  172 ,  174 . Connector tubes  2182 ,  2184 , in such a configuration, would extend through cable  400  for coupling with cooling module  500 . Instrument  100  would otherwise be configured similarly as detailed above and would function in a similar manner as detailed above and described in further detail below. 
     Turning now to  FIG.  10 A , a method provided in accordance with the present disclosure, and applicable for use with instrument  100  ( FIG.  1   ), instrument  1100  ( FIG.  5   ), instrument  2100  ( FIG.  6   ), or any other suitable ultrasonic surgical instrument incorporating or configured for use with a cooling system is described. 
     Initially, at S 901 , the end effector of the instrument is activated so as to supply ultrasonic energy to the end effector thereof to treat, for example, coagulate and/or cut, tissue. At S 902  it is determined whether ultrasonic energy is still being supplied to the end effector. Such a determination may be performed, as noted above, by determining whether an activation button is activated. However, other suitable ways of determining whether ultrasonic energy is being supplied to the end effector are also contemplated, e.g., monitoring the output of the battery or the input to or output from the transducer. If it is determined that ultrasonic energy is being supplied, the determination at S 902  is repeatedly made, periodically or continuously, until it is determined that ultrasonic energy is no longer being supplied to the end effector. 
     Once it is determined that ultrasonic energy is no longer being supplied to the end effector, the cooling system is activated as indicated in S 903 , to circulate cooling fluid through the end effector to cool the end effector. Likewise, an indicator S 904  is provided to indicate that cooling is ongoing. During cooling, it is determined, at S 905 , whether the temperature of the end effector is below a threshold temperature. As noted above with respect to instrument  100  ( FIG.  1   ), the temperature of the end effector may be determined indirectly by sensing the temperature of the fluid output to the end effector and returning therefrom. Such a configuration enables the use of temperature sensors remote from the end effector. 
     If the temperature of the end effector is determined to be above the threshold temperature, cooling continues at S 903  and the temperature is continuously or periodically determined at S 905 . At the same time, an indicator, as indicated in S 904 , is provided to alert the user that cooling is still ongoing. Once the temperature of the end effector assembly is below the threshold temperature, as indicated in S 906 , cooling is deactivated and the indicator is removed. The threshold temperature, in some embodiments, may be about 60° C. 
     Referring to S 907 , during cooling, if an error is detected, cooling is deactivated at S 906  and an indicator is provided at S 904 . Alternatively, the entire system may be shut down, inhibiting further activation or use, as indicated at S 906 ′. An error may include, as noted above, a condition where the flow rate of fluid is below a flow rate threshold, a condition where the fluid includes gas bubbles or a sufficiently high volume of gas bubble, or other suitable error condition. The indicator provided in response to an error may be different from the indicator provided during cooling. If no error is detected, cooling continues at S 903 . 
     Turning to S 908 , during cooling, it is determined whether the supply of ultrasonic energy to the end effector has been activated. If so, cooling is deactivated at S 909  and the method returns to S 901 . If the supplying of ultrasonic energy to the end effector has not been activated, the method returns to S 903  and cooling is continued until the temperature of the end effector is below the threshold temperature, an error is detected, or the supply of ultrasonic energy to the end effector is activated. 
     Referring to  FIG.  10 B , another method provided in accordance with the present disclosure, and applicable for use with instrument  100  ( FIG.  1   ), instrument  1100  ( FIG.  5   ), instrument  2100  ( FIG.  6   ), or any other suitable ultrasonic surgical instrument incorporating or configured for use with a cooling system is described. 
     The method of  FIG.  10 B  is similar to that of  FIG.  10 A  except that, during cooling, S 913 , it is determined at S 914  whether the time cooling has been activated has reached a threshold time. If the cooling time has reached the threshold time, cooling is deactivated at S 915 . If the cooling time has not reached the threshold time, cooling continues at S 913 . Determination of the cooling time may be based upon an uninterrupted duration of cooling, a cumulative amount of cooling since the last energization of the end effector, or in any other suitable manner. 
     Turning to  FIG.  11   , another surgical system for cooling a surgical instrument provided in accordance with the aspects and features of the present disclosure is shown generally identified by reference numeral  3010 . Surgical system  3010 , as detailed below, is configured for use with a conductive cooling fluid circulating through the instrument so as to enable measurement of the electrical impedance thereof to provide an indication of events that may occur during use, for example, determination of the whether the system is properly primed, detection of mechanical failure, detection of obstruction(s) in the flowpath, detection of gas bubbles in the flowpath, determining whether cooling is operating normally, etc. Surgical system  3010  may include any of the features of the surgical systems detailed above, and vice-versa. Accordingly, only those distinguishing features and those necessary to facilitate the understand of surgical system  3010  are described in detailed below. 
     Surgical system  3010  generally includes a surgical instrument  3100 , a cooling module  3500 , and a cooling fluid flowpath  3600  defined therebetween, e.g., via tubing, conduits, etc., that, together, incorporate a cooling system for cooling surgical instrument  3100 . Surgical instrument  3100  may be configured similar to surgical instrument  100  ( FIG.  1   ), surgical instrument  1100  ( FIG.  5   ), surgical instrument  2100  ( FIG.  6   ), or any other suitable surgical instrument. Inflow line  3610  of flowpath  3600  is configured to deliver conductive cooling fluid from cooling module  3500  to surgical instrument  3100 , while outflow line  3620  of flowpath  3600  is configured to return conductive cooling fluid from surgical instrument  3100  to cooling module  3500 . 
     Cooling module  3500  may be separate from surgical instrument  3100  (as with cooling module  500  ( FIG.  1   )) or may be integrated into surgical instrument  3100  (as with cooling module  1500  ( FIG.  5   )). Cooling module  3500  includes a generator  3510 , a pump assembly  3520 , a fluid reservoir  3530  retaining a conductive cooling fluid therein, and a controller  3540 . Generator  3510  is electrically coupled to instrument  3100 , e.g., via one or more wires  3512 , for supplying energy thereto. Where instrument  3100  is an ultrasonic instrument, for example, generator  3510  supplies suitable energy to the transducer (not shown) of instrument  3100  to drive the transducer. Generator  3510  further includes electrodes  3514 ,  3516  that are disposed in communication with the conductive cooling fluid adjacent the output from cooling module  3500  to instrument  3100  (location “A”) and towards the distal tip of instrument  3100  (location “B”), respectively. Electrodes  3514 ,  3516  may extend through inflow line  3610  and/or outflow line  3620  to respective locations “A” and “B,” as shown, may extend exteriorly of inflow line  3610  and/or outflow line  3620  and electrically couple to the conductive cooling fluid by way of one or more conductive couplings (not shown) at respective locations “A” and “B,” and/or may extend through a side wall of inflow line  3610  and/or outflow line  3620  into communication with the conductive cooling fluid at respective locations “A” and “B” with a seal disposed thereabout for sealing the opening in the side wall of inflow line  3610  and/or outflow line  3620 . Based upon electrical properties of the conductive cooling fluid detected by electrodes  3514 ,  3516 , generator  3510  is capable of determining the impedance of the conductive cooling fluid between locations “A” and “B.” The determined impedance can then be relayed to controller  3540  for outputting an indication of various events and/or controlling system  3010  accordingly, as detailed below. Additional or alternative locations for determining impedance therebetween are also contemplated, for example, the electrodes may be positioned as detailed in any or all of the above systems with respect to the sensors thereof. 
     Pump assembly  3520  may include any suitable pump, such as those detailed above, suitable for pumping conductive cooling fluid to circulate from cooling module  3500 , through instrument  3100 , and back to cooling module  3500 . Controller  3540  may control pump assembly  3520  to turn the pump “ON” and “OFF,” to pump the conductive cooling fluid at a particular flow rate and/or to achieve a particular rate of cooling. Fluid reservoir  3530  may be, for example, an IV bag retaining saline (or other suitable conductive cooling fluid) therein, or any other suitable fluid reservoir, such as those detailed above. 
     Referring still to  FIG.  11   , in use, as noted above, the determined impedance of the conductive cooling fluid between locations “A” and “B” can provide an indication of various events during use. For example, prior to cooling, system  3010  is primed by pump assembly  3520  operating to pump conductive cooling fluid to fill flowpath  3600  and remove any air bubbles from flowpath  3600 . The impedance measurement can be used to determine whether system  3010  has been properly primed, with all air bubbles removed. Specifically, this can be determined by comparing a target “PRIMED” impedance (which may be stored in a memory of controller  3540 ), representing the impedance in a condition where the cooling fluid flowpath  3600  is full, to the measured impedance between locations “A” and “B.” If there is a mismatch, difference outside an acceptable range of variability, or no impedance reading at all, this could indicate that system  3010  has not been properly primed or that priming is not yet complete. In response, pump assembly  3520  may be further operated to pump the conductive cooling fluid through flowpath  3600  to fill flowpath  3600  and remove the air bubbles therefrom. Upon determining that the target “PRIMED” impedance has been achieved (or the measured impedance is within the acceptable range of variability), the pump assembly  3520  may be shut “OFF” and an indication provided that system  3010  is primed and ready for cooling. 
     In the same manner as above, the impedance measurement can be used to indicate whether there is an obstruction or leakage in the flowpath  3600  and/or whether the surgical instrument is mechanically damaged, as such would result in a different impedance as compared to a corresponding target impedance, an impedance outside the acceptable range of variability as compared to a corresponding target impedance, or a “short circuit” condition, wherein an impedance measurement between locations “A” and “B” is unable to be obtained due to the lack of conductive cooling fluid extending therebetween. Based upon the impedance measurement and comparison, suitable indications may be provided to alert the user that there is an error or that an event that has occurred. 
     As another example, the impedance measurement may be utilized to determine a cooled state, initiate cooling, deactivate cooling, control cooling, and/or whether cooling is operating properly. This is because the impedance of the conductive cooling fluid will vary depending upon temperature. Thus, for example, controller  3540  can signal pump assembly  3520  to begin pumping the conductive cooling fluid when a target “ON” impedance or impedance within a particular range has been reached and/or to stop pumping the conductive cooling fluid when a target “OFF” impedance or impedance within a particular range has been reached. Delays may also be built-in, for example, where pump assembly  3520  is turned “OFF” a pre-determined time after the target “OFF” impedance or impedance within a particular range has been reached. Controller  3540  may further direct pump assembly  3520  to increase or decrease the flow rate of the conductive cooling fluid, for example, based upon an initial impedance at the beginning of cooling (indicative of the initial temperature), a rate of change in impedance during cooling (indicative of the efficiency of cooling), reaching certain intermediate impedance targets (indicative of the efficiency of cooling), etc. A failure to cool or inefficient cooling can also be detected based upon the impedance, indicating a lack of cooling or an unacceptable slow cooling. 
     The impedance-based feedback and control detailed above with respect to surgical system  3010  may be used in conjunction with or in place of the other controls detailed hereinabove. 
     Referring to  FIG.  11   , in conjunction with  FIGS.  1 ,  5 , and  6   , as noted above, instruments  100 ,  1100 ,  2100  include activation buttons  140 ,  1140 ,  2140  that are each selectively activatable in a first position and a second position to supply electrical energy to operate the instrument  100 ,  1100 ,  2100  in a low-power mode of operation and a high-power mode of operation, respectively. Such activation buttons  140 ,  1140 ,  2140 , more specifically, are each coupled to corresponding circuitry that provide low-voltage activation signals in either a first state, indicating the low-power mode of operation, or a second state, indicating the high-power mode of operation, such that the appropriate amount of energy is supplied to operate the instrument  100 ,  1100 ,  2100  in the selected mode. 
     Surgical instrument  3100  may include a similar activation button  3140  as detailed above with respect to instruments  100 ,  1100 ,  2100 , so as to provide either a “low” or “high” power signal to generator  3510  (or other suitable component such as, for example, a battery that powers generator  3510 ) to activate surgical instrument  3100  in the corresponding mode. In such a configuration, the electrodes  3514 ,  3516  utilized to determine impedance, rather than being directly coupled to generator  3510  (or the other suitable component), may be coupled to the circuitry of activation button  3140  and utilize the connections between activation button  3140  and generator  3510  (or the other suitable component), to provide the electrical property measurements to generator  3510  (or the other suitable component) without the need for additional wiring extending between instrument  3100  and cooling module  3500  (or between the electrodes and the battery or generator, when instrument  3100  employs an on-board battery and generator). As the “low” and “high” activation commands provided by activation button  3140  are at least an order of magnitude different from the electrical property signals sensed by electrodes  3514 ,  3516  to determine impedance, utilizing the same connections does not interfere with the determination of whether activation button  3140  has been activated in either the “low” or “high” power modes. 
     While several embodiments of the disclosure have been shown in the drawings and described hereinabove, 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. 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.