Patent Publication Number: US-2023141739-A1

Title: Tissue-Cutting Dilators and Methods Thereof

Description:
PRIORITY 
     This application claims the benefit of priority to U.S. Provisional Patent Application No. 63/277,002, filed Nov. 8, 2021, which is incorporated by reference in its entirety into this application. 
    
    
     BACKGROUND 
     Before placing a catheter in a blood vessel of a patient, it is common to nick the patient&#39;s skin about a needle tract at an insertion site for dilation of tissue therearound with a dilator. Typically, nicking the patient&#39;s skin and dilating the tissue around the needle tract is performed separately. Indeed, the nicking is usually performed with a dedicated skin nicker or a scalpel having a #11 blade; the dilating is usually performed with a dilator two French sizes larger than the catheter being placed. Attempts to integrate the nicking of the patient&#39;s skin and the dilating of the tissue around the needle tract have resulted in a spring-loaded blade generally regarded as unsafe due to clinicians not being able to control the blade. What is needed is a tissue-cutting dilator that safely integrates the nicking of a patient&#39;s skin at an insertion site with the dilating of tissue around a needle tract at the insertion site. Such a dilator would reduce procedural time and errors when, for example, placing a catheter at the insertion site. 
     Disclosed herein are tissue-cutting dilators and methods thereof that address the foregoing. 
     SUMMARY 
     Disclosed herein a tissue-cutting dilator including, in some embodiments, an elongate dilator body, a dilator tip, a plurality of retractable blades, and a cap. The dilator body includes a plurality of longitudinal guide slots along a distal portion of the dilator body. The dilator tip is formed in the distal portion of the dilator body or coupled to a distal end of the dilator body. The dilator tip includes a plurality of blade slots. The blades are disposed in the dilator body. The blades are configured to extend through the blade slots in at least a ready-to-dilate state of the dilator to cut tissue around an insertion site upon insertion into the insertion site. The cap is slidably disposed over the dilator body. The cap covers the dilator tip in at least the ready-to-dilate state of the dilator. 
     In some embodiments, the guide slots terminate as grooves in the dilator tip. The grooves provide reinforcing structure to the dilator tip over that provided by the guide slots for tissue dilation with the dilator tip. 
     In some embodiments, distal ends of the blades are short of a distal end of the dilator or the dilator tip thereof. Having distal ends of the blades short of the distal end of the dilator or the dilator tip thereof allows at least the distal end of the dilator tip to engage the insertion site before cutting the tissue around the insertion site. 
     In some embodiments, the blades include two intersecting blades coupled to a catch plate slidably disposed in the dilator body proximal of the dilator tip. 
     In some embodiments, the two intersecting blades provide four orthogonal blade edges. Each blade edge of the foregoing blade edges is orthogonal to its immediately adjacent blade edges. 
     In some embodiments, the catch plate is proximal of the distal tip in the ready-to-dilate state of the dilator. 
     In some embodiments, the cap includes a plurality of cap protrusions protruding toward a central axis of the dilator. The cap protrusions are disposed in at least a distal portion of the cap such that the cap protrusions slide in the guide slots and engage the catch plate when proximally sliding the cap over the dilator body past the dilator tip. Engaging the catch plate when proximally sliding the cap over the dilator body past the dilator tip retracts the blades into the dilator body for subsequent dilation with the dilator without further cutting the tissue around the insertion site. 
     In some embodiments, the cap is configured to proximally slide over the dilator body by interaction with skin around the insertion site as the dilator tip is inserted into the insertion site. 
     In some embodiments, the catch plate includes a plurality of notches configured to engage the cap protrusions in the distal portion of the cap. The notches in the catch plate are orthogonal to the blades. 
     In some embodiments, the cap protrusions are further disposed in a proximal portion of the cap. The cap protrusions in the proximal portion of the cap are configured to slide in the guide slots and obviate any play between the proximal portion of the cap and the dilator body thereunder. 
     In some embodiments, the catch plate includes a stabilizer integral with the catch plate or coupled to a proximal end of the catch plate. The stabilizer includes split legs configured to slidably engage an inner wall of the dilator body and mitigate tilting of the catch plate within the dilator body. Mitigating tilting of the catch plate within the dilator body keeps the blades properly aligned in the dilator body, thereby avoiding blade jams. 
     In some embodiments, the dilator further includes a compression spring. The compression spring is between a proximal end of the catch plate and a seat therefor in the dilator body. The compression spring is configured to mitigate tilting of the catch plate within the dilator body. Mitigating tilting of the catch plate within the dilator body keeps the blades properly aligned in the dilator body, thereby avoiding blade jams. 
     In some embodiments, the compression spring is further configured to keep the blades extending through the blade slots in the ready-to-dilate state of the dilator whether or not the dilator is pointed, in part, along a gravitational vector. 
     Also disclosed herein is another tissue-cutting dilator including, in some embodiments, an elongate dilator body, a dilator tip, and a pair of rotatable blades. The dilator tip is formed in the distal portion of the dilator body or coupled to a distal end of the dilator body. Each blade of the blades has an approximate shape of a geometric disk sector   with a blade edge along an arc thereof. Each blade of the blades is disposed in an opposite side of the dilator such that the blades cut tissue on opposite sides of an insertion site upon insertion of the dilator into the insertion site. 
     In some embodiments, the blades are short of a distal end of the dilator or the dilator tip thereof. Having the blades short of the distal end of the dilator or the dilator tip thereof allows at least the distal end of the dilator tip to engage the insertion site before cutting the tissue around the insertion site. 
     In some embodiments, each blade of the blades includes a primary tissue catch extending from a leading corner of the blade where a leading edge meets the blade edge. The primary tissue catch is configured to catch the tissue around the insertion site, rotate the blade out from the dilator body, and cut the tissue around the insertion site as the dilator is inserted into the insertion site. 
     In some embodiments, just the primary tissue catch extends from its respective side of the dilator in a ready-to-dilate state of the dilator. 
     In some embodiments, each blade of the blades includes a secondary tissue catch in a midsection of the blade edge. The secondary tissue catch is configured to further catch the tissue around the insertion site, further rotate the blade out from the dilator body, and further cut the tissue around the insertion site as the dilator is further inserted into the insertion site. 
     In some embodiments, each blade of the blades includes a tertiary tissue catch extending from a trailing corner of the blade where a trailing edge meets the blade edge. The tertiary tissue catch is configured to catch the tissue around the insertion site and rotate the blade into the dilator body without further cutting the tissue around the insertion site as the dilator is inserted into the insertion site. 
     In some embodiments, each blade of the blades is rotatably mounted on a pin of a pair of pins disposed in a pinhole of a pair of pinholes of a supporting frame. The frame is optionally divided between sides of the dilator including the blades. 
     In some embodiments, each pin of the pair or pins is disposed in a junction between the dilator body and the dilator tip. 
     In some embodiments, the frame is disposed in a middle of the dilator along a longitudinal plane of symmetry. 
     Also disclosed herein is a method of a tissue-cutting dilator including, in some embodiments, a dilator-inserting step, a tissue-cutting step, and a ceasing step. The dilator-inserting step includes inserting a dilator tip of the dilator into an insertion site. The dilator-inserting step commences dilation of tissue around the insertion site. The tissue-cutting step includes cutting the tissue around the insertion site with a plurality of blades while further inserting the dilator tip into the insertion site. The blades are disposed in the dilator short of a distal end of the dilator or the dilator tip thereof. The ceasing step includes ceasing to cut the tissue around the insertion site with the blades while even further inserting the dilator tip into the insertion site. The blades either retract or rotate into the dilator while even further inserting the dilator tip into the insertion site. 
     In some embodiments, a cap of the dilator is made to proximally slide over the dilator by interaction with skin around the insertion site while inserting the dilator tip into the insertion site during the dilator-inserting step. Proximally sliding the cap over the dilator exposes the blades for the cutting of the tissue around the insertion site. 
     In some embodiments, the blades include two intersecting blades coupled to a catch plate slidably disposed in a dilator body of the dilator. The catch plate is disposed in the dilator body proximal of the dilator tip. 
     In some embodiments, the two intersecting blades provide four orthogonal blade edges. Each blade edge of the foregoing blade edges is orthogonal to its immediately adjacent blade edges. 
     In some embodiments, the cap is further made to proximally slide over the dilator by the interaction with the skin around the insertion site while further inserting the dilator tip into the insertion site during the tissue-cutting step. Proximally sliding the cap further over the dilator keeps the blades exposed for the cutting of the tissue around the insertion site. 
     In some embodiments, the cap is even further made to proximally slide over the dilator by the interaction of the skin around the insertion site while even further inserting the dilator tip into the insertion site during the ceasing step. Proximally sliding the cap even further over the dilator makes cap protrusions of the cap extending through guide slots of the dilator to engage the catch plate and retract the blades into the dilator for the ceasing to cut the tissue around the insertion site with the blades. 
     In some embodiments, primary tissue catches of the blades in corresponding leading corners of the blades extend from sides of the dilator and catch skin around the insertion site while inserting the dilator tip into the insertion site during the dilator-inserting step. Catching skin around the insertion site while inserting the dilator tip into the insertion site rotates the blades out of the dilator for the cutting of the tissue around the insertion site. 
     In some embodiments, secondary tissue catches of the blades in midsections of the blades catch the tissue around the insertion site while further inserting the dilator tip into the insertion site during the tissue-cutting step. Catching skin around the insertion site while further inserting the dilator tip into the insertion site continues to rotate the blades out of the dilator for the cutting of the tissue around the insertion site. 
     In some embodiments, tertiary tissue catches of the blades in corresponding trailing corners of the blades catch the tissue around the insertion site while even further inserting the dilator tip into the insertion site during the ceasing step. Catching skin around the insertion site while even further inserting the dilator tip into the insertion site rotates the blades into the dilator for the ceasing to cut the tissue around the insertion site with the blades. 
     These and other features of the concepts provided herein will become more apparent to those of skill in the art in view of the accompanying drawings and following description, which describe particular embodiments of such concepts in greater detail. 
    
    
     
       DRAWINGS 
         FIG.  1    illustrates a first tissue-cutting dilator in a ready-to-dilate state with a cap over a dilator tip, the cap thereby covering retractable blades that extend through blade slots of the dilator tip in accordance with some embodiments. 
         FIG.  2    illustrates the first dilator in a relatively early dilating state with the cap over a proximal portion of a dilator body, the cap thereby exposing the blades that extend through the blade slots of the dilator tip in accordance with some embodiments. 
         FIG.  3    illustrates the first dilator in a relatively late dilating state with the cap over a medial portion of the dilator body, the blades retracted into the dilator body in accordance with some embodiments. 
         FIG.  4    illustrates an end-on view of a distal end of the first dilator in the ready-to-dilate state thereof in accordance with some embodiments. 
         FIG.  5    illustrates a detailed view of a distal portion of the first dilator in the ready-to-dilate state thereof in accordance with some embodiments. 
         FIG.  6    illustrates a detailed view of the distal portion of the first dilator in the relatively early dilating state thereof in accordance with some embodiments. 
         FIG.  7    illustrates a detailed view of the distal portion of the first dilator in the relatively late dilating state thereof in accordance with some embodiments. 
         FIG.  8    illustrates a detailed view of the cap of the first dilator in accordance with some embodiments. 
         FIG.  9    illustrates a longitudinal cross section of the cap of the first dilator in accordance with some embodiments. 
         FIG.  10    illustrates a detailed view of at least the distal portion of the first dilator without the cap in the relatively late dilating state thereof in accordance with some embodiments. 
         FIG.  11    illustrates a longitudinal cross section of at least the distal portion of the first dilator without the cap in the relatively late dilating state thereof, the dilator including a first blade carriage in accordance with some embodiments. 
         FIG.  12    illustrates the first blade carriage of the first dilator in accordance with some embodiments. 
         FIG.  13    illustrates an exploded view of the first blade carriage in accordance with some embodiments. 
         FIG.  14    illustrates a longitudinal cross section of at least the distal portion of the first dilator without the cap in the relatively late dilating state thereof, the dilator including a second blade carriage in accordance with some embodiments. 
         FIG.  15    illustrates the second blade carriage of the first dilator in accordance with some embodiments. 
         FIG.  16    illustrates an exploded view of the second blade carriage in accordance with some embodiments. 
         FIG.  17    illustrates a second tissue-cutting dilator in a ready-to-dilate state with proximally facing primary tissue catches of a pair of rotatable blades extending from sides of the dilator in accordance with some embodiments. 
         FIG.  18    illustrates a detailed view of a distal portion of the second tissue-cutting dilator in the ready-to-dilate state with the proximally facing primary tissue catches of the blades extending from the sides of the dilator in accordance with some embodiments. 
         FIG.  19    illustrates the second tissue-cutting dilator in a relatively early-to-mid dilating state with proximally facing secondary tissue catches of the blades extending from the sides of the dilator in accordance with some embodiments. 
         FIG.  20    illustrates a detailed view of the distal portion of the second tissue-cutting dilator in the relatively early-to-mid dilating state with the proximally facing secondary tissue catches of the blades extending from the sides of the dilator in accordance with some embodiments. 
         FIG.  21    illustrates the second tissue-cutting dilator in a mid-dilating state with proximally facing tertiary tissue catches of the blades extending from the sides of the dilator in accordance with some embodiments. 
         FIG.  22    illustrates a detailed view of the distal portion of the second tissue-cutting dilator in the mid-dilating state with the proximally facing tertiary tissue catches of the blades extending from the sides of the dilator in accordance with some embodiments. 
         FIG.  23    illustrates the second tissue-cutting dilator in a relatively mid-to-late dilating state with tertiary tissue catches of the blades rotating back into the sides of the dilator in accordance with some embodiments. 
         FIG.  24    illustrates a detailed view of the distal portion of the second tissue-cutting dilator in the relatively mid-to-late dilating state with the tertiary tissue catches of the blades rotating back into the sides of the dilator in accordance with some embodiments. 
         FIG.  25    illustrates the second tissue-cutting dilator in a relatively late-dilating state with the blades rotated back into the sides of the dilator in accordance with some embodiments. 
         FIG.  26    illustrates a detailed view of the distal portion of the second tissue-cutting dilator in the relatively late-dilating state with the blades rotated back into the sides of the dilator in accordance with some embodiments. 
         FIG.  27    illustrates an exploded view of the second tissue-cutting dilator in accordance with some embodiments. 
         FIG.  28    illustrates a detailed, exploded view of the distal portion of the second tissue-cutting dilator in accordance with some embodiments. 
         FIG.  29    illustrates a detailed view of a blade of the pair of blades in accordance with some embodiments. 
     
    
    
     DESCRIPTION 
     Before some particular embodiments are disclosed in greater detail, it should be understood that the particular embodiments disclosed herein do not limit the scope of the concepts provided herein. It should also be understood that a particular embodiment disclosed herein can have features that can be readily separated from the particular embodiment and optionally combined with or substituted for features of any of a number of other embodiments disclosed herein. 
     Regarding terms used herein, it should also be understood the terms are for the purpose of describing some particular embodiments, and the terms do not limit the scope of the concepts provided herein. Ordinal numbers (e.g., first, second, third, etc.) are generally used to distinguish or identify different features or steps in a group of features or steps, and do not supply a serial or numerical limitation. For example, “first,” “second,” and “third” features or steps need not necessarily appear in that order, and the particular embodiments including such features or steps need not necessarily be limited to the three features or steps. In addition, any of the foregoing features or steps can, in turn, further include one or more features or steps unless indicated otherwise. Labels such as “left,” “right,” “top,” “bottom,” “front,” “back,” and the like are used for convenience and are not intended to imply, for example, any particular fixed location, orientation, or direction. Instead, such labels are used to reflect, for example, relative location, orientation, or directions. Singular forms of “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. 
     With respect to “proximal,” a “proximal portion” or “proximal section” of, for example, a tissue-cutting dilator includes a portion or section of the dilator intended to be near a clinician when the dilator is used on a patient. Likewise, a “proximal length” of, for example, the dilator includes a length of the dilator intended to be near the clinician when the dilator is used on the patient. A “proximal end” of, for example, the dilator includes an end of the dilator intended to be near the clinician when the dilator is used on the patient. The proximal portion, the proximal section, or the proximal length of the dilator can include the proximal end of the dilator; however, the proximal portion, the proximal section, or the proximal length of the dilator need not include the proximal end of the dilator. That is, unless context suggests otherwise, the proximal portion, the proximal section, or the proximal length of the dilator is not a terminal portion or terminal length of the dilator. 
     With respect to “distal,” a “distal portion” or a “distal section” of, for example, a tissue-cutting dilator includes a portion or section of the dilator intended to be near or in a patient when the dilator is used on the patient. Likewise, a “distal length” of, for example, the dilator includes a length of the dilator intended to be near or in the patient when the dilator is used on the patient. A “distal end” of, for example, the dilator includes an end of the dilator intended to be near or in the patient when the dilator is used on the patient. The distal portion, the distal section, or the distal length of the dilator can include the distal end of the dilator; however, the distal portion, the distal section, or the distal length of the dilator need not include the distal end of the dilator. That is, unless context suggests otherwise, the distal portion, the distal section, or the distal length of the dilator is not a terminal portion or terminal length of the dilator. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art. 
     As set forth above, it is common to nick a patient&#39;s skin about a needle tract at an insertion site for dilation of tissue therearound with a dilator before placing a catheter in a blood vessel of the patient. Typically, nicking the patient&#39;s skin and dilating the tissue around the needle tract is performed separately. Indeed, the nicking is usually performed with a dedicated skin nicker or a scalpel having a #11 blade; the dilating is usually performed with a dilator two French sizes larger than the catheter being placed. Attempts to integrate the nicking of the patient&#39;s skin and the dilating of the tissue around the needle tract have resulted in a spring-loaded blade generally regarded as unsafe due to clinicians not being able to control the blade. What is needed is a tissue-cutting dilator that safely integrates the nicking of a patient&#39;s skin at an insertion site with the dilating of tissue around a needle tract at the insertion site. Such a dilator would reduce procedural time and errors when, for example, placing a catheter at the insertion site. 
     Disclosed herein are tissue-cutting dilators and methods thereof that address the foregoing. 
     Dilators 
       FIGS.  1 - 17    illustrate a first tissue-cutting dilator  100  in accordance with some embodiments. 
     As shown, the dilator  100  includes an elongate dilator body  102 , a dilator tip  104 , a blade carriage  106 , and a cap  108 . 
     The dilator body  102  includes a plurality of longitudinal guide slots  110  along a distal portion of the dilator body  102 . The guide slots  110  distally terminate with open-ended grooves  112  in the dilator tip  104 , which grooves  112  provide reinforcing structure (e.g., connecting or bridging portions) to the dilator tip  104  over that provided by the guide slots  110  for tissue dilation with the dilator tip  104 . The guide slots  110  and the grooves  112  are configured to accept therein the cap protrusions  134  for proximally sliding the cap  108  over the dilator body  102 . Notably, one or more of the guide slots  110  can include up to at least a pair of guide-slot catches  114  per guide slot. Such catches are configured to restrict the cap  108  from distally sliding over the dilator tip  104  in the ready-to-dilate state of the dilator  100  by inhibiting the cap protrusions  134  in the proximal portion of the cap  108 , which cap protrusions are proximal of the guide-slot catches  114  in the ready-to-dilate state of the dilator  100 , from passing thereby. Such catches are also configured to restrict the cap  108  from distally sliding back over the dilator body  102  in later dilating states of the dilator  100  by inhibiting the cap protrusions  134  in the distal portion of the cap  108 , which are proximal of the guide-slot catches  114  in the later dilating states of the dilator  100 , from passing thereby. In addition, the guide slots  110  proximally terminate with terminal ends  116  in, for example, a medial portion of the dilator body  102 . Such terminal ends are configured to restrict the cap  108  from proximally sliding too far over the dilator body  102  by inhibiting the cap protrusions  134  in either the proximal or distal portion of the cap  108  from passing thereby. 
     The dilator tip  104  is formed in the distal portion of the dilator body  102  or coupled to a distal end of the dilator body  102 . The dilator tip  104  includes a plurality of blade slots  118  orthogonal to the guide slots  110  configured for extending the blades  122  therethrough. Notably, distal ends of the blade slots  118  are short of a distal end of the dilator  100  or the dilator tip  104  thereof. Having distal ends of the blade slots  118  short of the distal end of the dilator  100  or the dilator tip  104  thereof allows at least the distal end of the dilator tip  104  to engage an insertion site before cutting tissue around the insertion site with the blades  122 . 
     The blade carriage  106  is slidably disposed in the dilator body  102  such that a catch plate  120  thereof is proximal of the dilator tip  104  in the ready-to-dilate state of the dilator  100 . The blade carriage  106  includes a plurality of retractable blades  122  coupled to the catch plate  120 , the blades  122  being retractable in accordance with proximally sliding the blade carriage  106  with the cap  108  when the cap  108  is proximally slid over the dilator body  102 . 
     The blades  122  are configured to extend through the blade slots  118  in at least a ready-to-dilate state of the dilator  100  for cutting tissue around an insertion site upon insertion into the insertion site. However, distal ends of the blades  122  are short of the distal end of the dilator  100  or the dilator tip  104  thereof. Having distal ends of the blades  122  short of the distal end of the dilator  100  or the dilator tip  104  thereof allows at least the distal end of the dilator tip  104  to engage an insertion site before cutting tissue around the insertion site with the blades  122 . 
     The blades  122  can include two intersecting blades coupled to the catch plate  120 ; however, the blades  122  are not limited to the two intersecting blades as fewer or more of the blades  122  can be used with or without intersecting to a same or different effect. That said, the two intersecting blades provide four orthogonal blade edges  124 , wherein each blade edge of the blade edges  124  is orthogonal to its immediately adjacent blade edges  124 . Advantageously, the blades  122  cut tissue in an ‘X’-style cut along two orthogonal planes with comparatively shorter individual cuts along the two orthogonal planes than that required in existing methods such as those set forth above. Such an ‘X’-style cut of the tissue maximizes the so-called opening response of the tissue, leading to less tension in the tissue and, thus, a lower insertion force, thereby reducing damage to the tissue. 
     The catch plate  120  can include one or more slots or recesses  126  in which proximal ends of the blades  122  are disposed with transition- or interference-type engineering fits. In addition to the foregoing engineering fits, or as an alternative to them, the proximal ends of the blades  122  can be bonded to the one-or-more slots or recesses  126  of the catch plate  120 . 
     The catch plate  120  can include a plurality of distally opening notches  128  configured to engage the cap protrusions  134  in the distal portion of the cap  108 . Indeed, the notches  128  engaging the cap protrusions  134  when proximally sliding the cap  108  over the dilator body  102  past the dilator tip  104  proximally slides the blade carriage  106  in the dilator body  102 , thereby retracting the blades  122  into the dilator body  102  for subsequent dilation of an insertion site with the dilator  100  without further cutting tissue around the insertion site. While the notches  128  can vary in number in accordance with the cap protrusions  134 ,  FIG.  12    illustrates four orthogonal notches, wherein each notch of the notches  128  is orthogonal to its immediately adjacent notches  128 ; however, the notches  128  in the catch plate  120  are isogonally staggered with the blade edges  124 , the proximal ends of the blades  122 , or the one- or-more slots or recess  126  in the catch plate  120  by 45° to provide maximal circumferential clearance between the blade edges  124  and the cap protrusions  134 . 
     The catch plate  120  can include a stabilizer  130  integral with the catch plate  120  or coupled to a proximal end of the catch plate  120 . The stabilizer  130  includes split legs  132  configured to slidably engage an inner wall of the dilator body  102 . Notwithstanding the terminal ends  116  of the guide slots  110 , the split legs  132  of the stabilizer  130  in combination with, for example, one or more inner-wall protrusions protruding from the inner wall of the dilator body  102 , are configured to form a stopping mechanism in a proximal portion of the dilator body  102  for stopping the blade carriage  106  from proximally sliding too far in the dilator body  102 . Advantageously, when the stabilizer  130 , the one-or-more inner-wall protrusions, and the guide-slot catches  114  are present in the dilator  100 , the blade carriage  106  can be locked into a proximal location in the dilator body  102  by a combination of the cap protrusions  134  proximal of the guide-slot catches  114  in the guide slots  110 , the cap protrusions  134  disposed in the notches  128  of the catch plate  120 , and the split legs  132  of the stabilizer  130  distal of the one the one-or-more inner-wall protrusions when the blade carriage  106  is proximally slid to that location while dilating with the dilator  100 . In this way, the foregoing features provide an integrated single-use enforcement mechanism enforcing a single use of each dilator like the dilator  100 . Notably, the stabilizer  130  can mitigate tilting of the catch plate  120  within the dilator body  102 . Mitigating the tilting of the catch plate  120  within the dilator body  102  keeps the blades  122  properly aligned in the dilator body  102 , thereby avoiding blade jams against, for example, the inner wall of the dilator body  102  or that of the dilator tip  104  adjacent the blade slots  118  when the blade carriage  106  is proximally slid in the dilator body  102 . 
     The cap  108  is slidably disposed over the dilator body  102 . The cap  108  covers the dilator tip  104  providing a safeguard with respect to the blades  122  extending through the blade slots  118  of the dilator tip  104  in at least the ready-to-dilate state of the dilator  100 . Notably, the cap  108  is configured to proximally slide over the dilator body  102  by interaction with skin around an insertion site as the dilator tip  104  is inserted into a needle tract at the insertion site. Indeed, as the dilator tip  104  is advanced into the needle tract, the skin around the insertion site pushes the cap  108  such that it proximally slides over the dilator body  102 . 
     The cap  108  includes a plurality of cap protrusions  134  protruding toward a central axis of the dilator  100 . The cap protrusions  134  are disposed in at least a distal portion of the cap  108  such that the cap protrusions  134  slide in the guide slots  110  and engage the notches  128  of the catch plate  120  when proximally sliding the cap  108  over the dilator body  102  past the dilator tip  104 . The cap protrusions  134  engaging the notches  128  of the catch plate  120  when proximally sliding the cap  108  over the dilator body  102  past the dilator tip  104  proximally slides the blade carriage  106  in the dilator body  102 , thereby retracting the blades  122  into the dilator body  102  for subsequent dilation of an insertion site with the dilator  100  without further cutting tissue around the insertion site. Notably, the cap protrusions  134  or a protruding annulus can be further disposed in a proximal portion of the cap  108 . The cap protrusions  134  in the proximal portion of the cap  108  can be configured to slide in the guide slots  110  and obviate any play between the proximal portion of the cap  108  and the dilator body  102  thereunder. That said, the cap protrusions  134  or the protruding annulus in the proximal portion of the cap  108  can be configured to slide over the dilator body  102  outside of the guide slots  110  and likewise obviate any play between the proximal portion of the cap  108  and the dilator body  102  thereunder. 
     While not shown, the dilator  100  can further include a compression spring. When present, the compression spring can be between and, optionally, coupled to the proximal end of the catch plate  120  and a seat for the compression spring in the dilator body  102  like that of the one-or-more inner walls set forth above. When present, the compression spring keeps the blades  122  of the blade carriage  106  extending through the blade slots  118  of the dilator tip  104  in the ready-to-dilate state of the dilator  100  whether or not the dilator  100  is pointed, in part, along a gravitational vector. Like the stabilizer  130 , the compression spring can also mitigate the tilting of the catch plate  120  within the dilator body  102 . As set forth above, mitigating the tilting of the catch plate  120  within the dilator body  102  keeps the blades  122  properly aligned in the dilator body  102 , thereby avoiding blade jams. 
       FIGS.  8 - 29    illustrate a second tissue-cutting dilator  200  in accordance with some embodiments. 
     As shown, the dilator  200  includes an elongate dilator body  202 , a dilator tip  204 , a supporting frame  236 , and a pair of rotatable blades  238 . 
     The dilator tip  204  is formed in the distal portion of the dilator body  202  or coupled to a distal end of the dilator body  202 . Regardless, the dilator  200  includes a pair of blade slots  240  in sides of the dilator  200  between the dilator tip  204  and the dilator body  202  configured for rotating the blades  238  out of the dilator  200  in a ready-to-dilate state of the dilator  200  and back into the dilator  200  in a mid-dilating state to a relatively late-dilating state of the dilator  200 . Notably, distal ends of the blade slots  240  are short of a distal end of the dilator  200  or the dilator tip  204  thereof. Having distal ends of the blade slots  240  short of the distal end of the dilator  200  or the dilator tip  204  thereof allows at least the distal end of the dilator tip  204  to engage an insertion site before cutting tissue around the insertion site with the blades  238 . 
     The frame  236  is disposed in a middle of the dilator  200  between the dilator tip  204  and the dilator body  202  in support of the blades  238  and their rotation out of the dilator  200  in the ready-to-dilate state of the dilator  200  and back into the dilator  200  in the mid-dilating state to the relatively late-dilating state of the dilator  200 . The frame  236  is optionally a single piece, two pieces divided between top and bottom halves of the dilator  200  defined as being on opposite sides of a first longitudinal plane of symmetry of the dilator  200  including the frame  236  and the blades  238 , or four pieces divided between the top and bottom halves of the dilator  200  as well as sinistral and dextral sides of the dilator  200  defined as being on opposite sides of a second longitudinal plane of symmetry of the dilator  200  orthogonal to the first longitudinal plane of symmetry. Regardless, the frame  236  includes a pair of pinholes  242  in a transition or junction between the dilator tip  204  and the dilator body  202  but symmetrically distributed between sinistral and dextral sides of the dilator  200 . A pin of a pair of pins  244  is disposed in each pinhole of the pinholes  242 , and each blade of the blades  238  is rotatably mounted on one of the foregoing pins  244 . 
     Notwithstanding the pins  244  upon which the blades  238  are rotatably mounted, the frame  236  includes a pair of blade-lock pins  246  proximal of the pinholes  242  in the transition or junction between the dilator tip  204  and the dilator body  202 . The blade-lock pins  246  are configured to insert into the blade-lock holes  260  of the blades  238  when the blades  238  rotate their respective blade-lock holes  260  over the blade-lock pins  246  in the relatively late-dilating state of the dilator  200 . Advantageously, both the blade-lock pins  246  and the blade-lock holes  260  function in concert to lock the blades  238  in the dilator body  202  in the relatively late-dilating state of the dilator  200 , thereby ceasing to cut tissue around an insertion site even if continuing to insert the dilator  200  into the insertion site. In this way, the foregoing features provide an integrated single-use enforcement mechanism enforcing a single use of each dilator like the dilator  200 . 
     Each blade of the blades  238  is disposed in an opposite side (e.g., the sinistral or dextral side) of the dilator  200  such that the blades  238  cut tissue on opposite sides of an insertion site upon insertion of the dilator  200  into the insertion site. However, the blades  238  are short of a distal end of the dilator  200  or the dilator tip  204  thereof. Having the blades  238  short of the distal end of the dilator  200  or the dilator tip  204  thereof allows at least the distal end of the dilator tip  204  to engage the insertion site before cutting the tissue around the insertion site. 
     Each blade of the blades  238  has an approximate shape of a geometric disk sector   with a radius such as a leading radius of a leading edge  248  or a trailing radius of a trailing edge  250  as well as a blade edge  252  along an arc between the foregoing radii or edges  248  and  250 . Each blade of the blades  238  includes a primary tissue catch  254  (e.g., a hook) extending from a leading corner of the blade where the leading edge  248  meets the blade edge  252 . The primary tissue catch  254  is configured to catch the tissue around the insertion site, rotate its corresponding blade out from the dilator body  202 , and cut the tissue around the insertion site as the dilator  200  is inserted into the insertion site. Notably, just the primary tissue catch  254  extends from its respective side of the dilator  200  in a ready-to-dilate state of the dilator  200 . Each blade of the blades  238  also includes a secondary tissue catch  256  (e.g., a hook, but less pronounced than that of the primary tissue catch  254 ) in a midsection of the blade edge  252 . The secondary tissue catch  256  is configured to further catch the tissue around the insertion site, further rotate its corresponding blade out from the dilator body  202 , and further cut the tissue around the insertion site as the dilator  200  is further inserted into the insertion site. Each blade of the blades  238  also includes a tertiary tissue catch  258  including a trailing corner of the blade where the trailing edge  250  meets the blade edge  252 . The tertiary tissue catch  258  is configured to catch the tissue around the insertion site and rotate its corresponding blade into the dilator body  202  without further cutting the tissue around the insertion site as the dilator  200  is inserted into the insertion site. 
     The blades  238  also have blade-lock holes  260 , wherein each blade of the blades  238  has a blade-lock hole along the trailing edge  250  thereof. Such a blade-lock hole is configured to accept insertion of a blade-lock pin of the blade-lock pins  246  therein when its corresponding blade is rotated over the blade-lock pin in the relatively late-dilating state of the dilator  200 . Advantageously, both the blade-lock holes  260  and the blade-lock pins  246  function in concert to lock their corresponding blades  238  in the dilator body  202  in the relatively late-dilating state of the dilator  200 , thereby ceasing to cut tissue around an insertion site even if continuing to insert the dilator  200  into the insertion site. In this way, the foregoing features provide an integrated single-use enforcement mechanism enforcing a single use of each dilator like the dilator  100 . 
       FIGS.  17 - 26    illustrate the dilator  200  in various states thereof from the ready-to-dilate state of the dilator  200  through the relatively late-dilating state of the dilator  200 , which, in turn, illustrates how features of the blades  238  including the various tissue catches (i.e., the primary tissue catch  254 , the secondary tissue catch  256 , and the tertiary tissue catch  258 ) thereof function when dilating a needle tract of an insertion site with the dilator  200 . Indeed,  FIGS.  17  and  18    illustrate the dilator  200  in the ready-to-dilate state of the dilator  200  with the primary tissue catch  254  of each blade of the blades  238  proximally facing and extending from the sides (e.g., the sinistral and dextral sides) of the dilator  200 . Again, the primary tissue catch  254  are configured to catch the tissue around the insertion site, rotate the blades  238  out from the dilator body  202 , and cut the tissue around the insertion site as the dilator  200  is inserted into the insertion site. 
       FIGS.  19  and  20    illustrate the dilator  200  in a relatively early-to-mid dilating state of the dilator  200  with the secondary tissue catch  256  of each blade of the blades  238  proximally facing and extending from the sides of the dilator  200  in accordance with some embodiments. Again, the secondary tissue catch  256  is configured to further catch the tissue around the insertion site, further rotate the blades  238  out from the dilator body  202 , and further cut the tissue around the insertion site as the dilator  200  is further inserted into the insertion site.  FIGS.  21  and  22    illustrate the dilator  200  in the mid-dilating state of the dilator  200  with the tertiary tissue catch  258  of each blade of the blades  238  proximally facing extending from the sides of the dilator  200  in accordance with some embodiments. Again, the tertiary tissue catch  258  is configured to catch the tissue around the insertion site and rotate the blades  238  into the dilator body  202  without further cutting the tissue around the insertion site as the dilator  200  is inserted into the insertion site. 
       FIGS.  23  and  24    illustrate the dilator  200  in a relatively mid-to-late dilating state of the dilator  200  with the tertiary tissue catch  258  of each blade of the blades  238  rotating back into the sides of the dilator  200  in accordance with some embodiments. Lastly,  FIGS.  25  and  26    illustrate the dilator  200  in the relatively late-dilating state of the dilator  200  with the blades  238  rotated back into the sides of the dilator  200  in accordance with some embodiments. Notably, each blade of the blades  238  rotates about 330° from the ready-to-dilate state of the dilator  200  through the relatively late-dilating state of the dilator  200 . 
     Methods 
     Methods include methods of using the dilator  100  or  200 . For example, a method of using the dilator  100  or  200  includes one or more steps selected from a dilator-inserting step, a tissue-cutting step, and a ceasing step. 
     The dilator-inserting step includes inserting at least the distal end of the dilator tip  104  or  204  into a needle tract (e.g., a needle tract from an area of skin to a blood-vessel lumen) of an insertion site after the needle tract is established with an introducer needle. The dilator-inserting step commences dilation of tissue around the insertion site. 
     The tissue-cutting step includes cutting the tissue around the insertion site with the blades  122  or  238  while further inserting the dilator tip  104  or  204  into the insertion site. As set forth above, the blades  122  or  238  are disposed in the dilator  100  or  200  short of the distal end of the dilator tip  104  or  204  such that at least the distal end of the dilator tip  104  or  204  can engage the insertion site in the dilator-inserting step before cutting the tissue around the insertion site with the blades  122  or  238  in the tissue-cutting step. 
     The ceasing step includes ceasing to cut the tissue around the insertion site with the blades  122  or  238  while even further inserting the dilator tip  104  or  204  into the insertion site. When the dilator  100  is used, the blades  122  retract into the dilator  100  while even further inserting the dilator tip  104  into the insertion site. But when the dilator  200  is used, the blades  238  rotate into the dilator  200  while even further inserting the dilator tip  204  into the insertion site. 
     Adverting to the dilator  100  for description thereof in the foregoing steps, the cap  108  of the dilator  100  is made to proximally slide over the dilator  100  by interaction with skin around the insertion site while inserting the dilator tip  104  into the insertion site during the dilator-inserting step. Proximally sliding the cap  108  over the dilator  100  exposes the blades  122  for the cutting of the tissue around the insertion site. The cap  108  is further made to proximally slide over the dilator  100  by the interaction with the skin around the insertion site while further inserting the dilator tip  104  into the insertion site during the tissue-cutting step. Proximally sliding the cap  108  further over the dilator  100  keeps the blades  122  exposed for the cutting of the tissue around the insertion site. The cap  108  is even further made to proximally slide over the dilator  100  by the interaction of the skin around the insertion site while even further inserting the dilator tip  104  into the insertion site during the ceasing step. Proximally sliding the cap  108  even further over the dilator  100  makes the cap protrusions  134  extending through the guide slots  110  of the dilator  100  to engage the catch plate  120  and retract the blades  122  into the dilator  100  for the ceasing to cut the tissue around the insertion site with the blades  122 . 
     Adverting to the dilator  200  for description thereof in the foregoing steps, the primary tissue catch  254  of each blade of the blades  238  in the corresponding leading corners of the blades  238  extend from the sides of the dilator  200  and catch skin around the insertion site while inserting the dilator tip  204  into the insertion site during the dilator-inserting step. Catching the skin around the insertion site while inserting the dilator tip  204  into the insertion site rotates the blades  238  out of the dilator  200  for the cutting of the tissue around the insertion site. The secondary tissue catch  256  of each blade of the blades  238  in the midsections of the blades  238  catch the tissue around the insertion site while further inserting the dilator tip  204  into the insertion site during the tissue-cutting step. Catching the skin around the insertion site while further inserting the dilator tip  204  into the insertion site continues to rotate the blades  238  out of the dilator  200  for the cutting of the tissue around the insertion site. The tertiary tissue catch  258  of each blade of the blades  238  in the corresponding trailing corners of the blades  238  catch the tissue around the insertion site while even further inserting the dilator tip  204  into the insertion site during the ceasing step. Catching the skin around the insertion site while even further inserting the dilator tip  204  into the insertion site rotates the blades  238  into the dilator  200  for the ceasing to cut the tissue around the insertion site with the blades  238 . 
     While some particular embodiments have been disclosed herein, and while the particular embodiments have been disclosed in some detail, it is not the intention for the particular embodiments to limit the scope of the concepts provided herein. Additional adaptations or modifications can appear to those of ordinary skill in the art, and, in broader aspects, these adaptations or modifications are encompassed as well. Accordingly, departures may be made from the particular embodiments disclosed herein without departing from the scope of the concepts provided herein.