Are multiple cryoprobes additive or synergistic in renal cryotherapy?

OBJECTIVE: To investigate the relationship between multiple cryoprobes was investigated to determine whether they work in an additive or synergistic fashion in an in vivo animal model because 1.47 mm (17-gauge) cryoprobes have been introduced to the armamentarium for renal cryotherapy. METHODS: Laparoscopic-guided percutaneous cryoablation was performed in both renal poles of 3 pigs using 3 IceRod cryoprobes. These 12 cryolesions were compared with 12 cryolesions using a single IceRod cryoprobe. Each cycle consisted of two 10-minute freeze cycles separated by a 5-minute thaw. The iceball volume was measured using intraoperative ultrasonography. The kidneys were harvested, and cryolesion surface area was calculated. The lesions were fixed and excised to obtain a volume measurement. Statistical analysis was used to compare the single probe results multiplied by 3 to the multiple probe group for iceball volume, cryolesion surface area, and cryolesion volume. RESULTS: The iceball volume for the first freeze cycle for the single cryoprobe multiplied by 3 was 8.55 cm3 compared with 9.79 cm3 for the multiple cryoprobe group (P=.44) and 10.01 cm3 versus 16.58 cm3 for the second freeze (P=.03). The cryolesion volume for the single cryoprobe multiplied by 3 was 11.29 cm3 versus 14.75 cm3 for the multiple cyroprobe group (P=.06). The gross cryolesion surface area for the single cryoprobe multiplied by 3 was 13.14 cm2 versus 13.89 cm2 for the multiple probe group (P=.52). CONCLUSION: The cryolesion created by 3 simultaneously activated 1.47-mm probes appears to be larger than that of an additive effect. The lesions were significantly larger as measured by ultrasonography and nearly so (P=.06) as measured by the gross cryolesion volume.

Ice burn: protecting the flank during renal cryotherapy.

INTRODUCTION AND OBJECTIVES: Cryoablation is a viable minimally invasive strategy for the treatment of small renal masses. One of the most common postoperative complaints is pain or paresthesia at the cryoprobe insertion site. The use of a 14-gauge angiocatheter to insulate the flank during renal cryotherapy was investigated. MATERIALS AND METHODS: Six Yorkshire swine underwent laparoscopy-guided percutaneous cryoablation of the upper and lower poles of both kidneys with a 1.47 mm (17 gauge) cryoneedle. Treatment consisted of a double 10-minute freeze separated by a 5-minute active thaw. Trials were randomized to placement of the cryoneedle directly through the flank or through a 14-gauge angiocatheter as an insulating sheath. Temperatures were recorded adjacent to the cryoneedle at two depths in the flank with a Multi-Point Thermal Sensor. RESULTS: Twelve trials were completed each with a bare and sheathed cryoneedle. The coldest temperature observed was -26 degrees C for the bare cryoneedle and -21 degrees C for the sheathed cryoneedle. At the outer sensor, there was a 4.1 degrees C increase in mean temperature for freeze 1, and 6.2 degrees C increase in mean temperature for freeze 2 with sheath use. At the inner sensor, there was a 3.0 degrees C increase in mean temperature for freeze 1, and 9.4 degrees C increase in mean temperature for freeze 2 with sheath use. There was a trend toward statistical significance of sheath insulation at the outer (p = 0.07) and inner (p = 0.08) temperature sensors. CONCLUSIONS: A 14-gauge angiocatheter may provide some insulation and thereby might help protect against "ice burn" during renal cryotherapy.

In vitro, ex vivo and in vivo isotherms for renal cryotherapy.

PURPOSE: Preoperative planning for renal cryotherapy is based on isotherms established in gel. We replicated gel isotherms and correlated them with ex vivo and in vivo isotherms in a porcine model. MATERIALS AND METHODS: PERC-17 CryoProbes (1.7 mm) and IceRods (1.47 mm) underwent trials in gel, ex vivo and in vivo porcine kidneys. Temperatures were recorded at 13 predetermined locations with multipoint thermal sensors. RESULTS: At the cryoprobe temperatures were not significantly different along the probe in any medium for either system (p = 0.0947 to 0.9609). However, away from the probe ex vivo and in vivo trials showed warmer temperatures toward the cryoprobe tip for each system (p = 0.0003 to 0.2141). Mean +/- SE temperature 5 mm distal to the cryoprobe tip in vivo was 19.2C +/- 16.1C for CryoProbes and 27.3C +/- 11.2C for IceRods. Temperatures were consistently colder with CryoProbes than with IceRods in gel (p <0.00005), ex vivo (p <0.00005) and in vivo (p = 0.0014). At almost all sites temperatures were significantly colder in gel and in ex vivo kidney than in in vivo kidney for CryoProbes (p = 0.0107 and 0.0008, respectively) and for IceRods (each p <0.00005). CONCLUSIONS: Gel and ex vivo isotherms do not predict the in vivo pattern of freezing. Thus, they should not be used for preoperative planning. The cryoprobe should be passed 5 mm beyond the tumor border to achieve suitably cold temperatures. Multipoint thermal sensor probes are recommended to record actual temperature during renal cryotherapy.

Impact of pneumoperitoneum on renal cryotherapy.

PURPOSE: Pneumoperitoneum is known to decrease blood flow to the kidney during laparoscopy. We investigated if this change in blood flow would increase the size of the cryolesion. MATERIALS AND METHODS: Twelve Yorkshire swine underwent laparoscopy-guided percutaneous cryoablation of the upper and lower pole of each kidney at four randomized pneumoperitoneum pressures (10, 15, 20, and 25 mm Hg). Cryolesions were made with a 1.47-mm IceRod (Galil Medical, Plymouth Meeting, PA). Each site underwent two 10-minute freeze cycles separated by a 5-minute active thaw with pressurized helium gas. At the conclusion of each freeze cycle, the iceball volume was measured with intraoperative ultrasound. After completion of the four cryolesions, the kidneys were harvested, and the cryolesion surface area was calculated. The lesions were fixed in 10% buffered formalin and then excised with a 1-mm margin to obtain a volume measurement using fluid displacement. RESULTS: Iceball volume was 3.41, 2.85, 3.44, and 2.36 cm(3) for freeze cycle 1 (p = 0.16) and 3.67, 3.34, 4.88, 3.95 cm(3) for freeze cycle 2 (p = 0.20) at 10, 15, 20, and 25 mm Hg, respectively. Cryolesion volume by fluid displacement was 4.06, 3.77, 3.97, and 3.93 cm(3) (p = 0.86) and cryolesion surface area was 4.55, 4.38, 4.39, and 4.20 cm(2) (p = 0.71) at 10, 15, 20, and 25 mm Hg, respectively. CONCLUSIONS: In this study, pneumoperitoneum pressure between 10 and 25 mm Hg did not affect iceball size as measured by intraoperative ultrasound, cryolesion volume by fluid displacement, or cryolesion surface.

Preliminary study of virtual reality and model simulation for learning laparoscopic suturing skills.

PURPOSE: Repetitive practice of laparoscopic suturing and knot tying can facilitate surgeon proficiency in performing this reconstructive technique. We compared a silicone model and pelvic trainer to a virtual reality simulator in the learning of laparoscopic suturing and knot tying by laparoscopically naïve medical students, and evaluated the subsequent performance of porcine laparoscopic cystorrhaphy. MATERIALS AND METHODS: A total of 20 medical students underwent a 1-hour didactic session with video demonstration of laparoscopic suturing and knot tying by an expert laparoscopic surgeon. The students were randomized to a pelvic trainer (10) or virtual reality simulator (10) for a minimum of 2 hours of laparoscopic suturing and knot tying training. Within 1 week of the training session the medical students performed laparoscopic closure of a 2 cm cystotomy in a porcine model. Objective structured assessment of technical skills for laparoscopic cystorrhaphy was performed at the procedure by laparoscopic surgeons blinded to the medical student training format. A video of the procedure was evaluated with an objective structured assessment of technical skills by an expert laparoscopic surgeon blinded to medical student identity and training format. The medical students completed an evaluation questionnaire regarding the training format after the laparoscopic cystorrhaphy. RESULTS: All students were able to complete the laparoscopic cystorrhaphy. There was no difference between the pelvic trainer and virtual reality groups in mean +/- SD time to perform the porcine cystorrhaphy at 40 +/- 15 vs 41 +/- 10 minutes (p = 0.87) or the objective structured assessment of technical skills score of 8.8 +/- 2.3 vs 8.2 +/- 2.2 (p = 0.24), respectively. Bladder leak occurred in 3 (30%) of the pelvic trainer trained and 6 (60%) of the virtual reality trained medical student laparoscopic cystorrhaphy procedures (Fisher exact test p = 0.37). The only significant difference between the 2 groups was that 4 virtual reality trained medical students considered the training session too short compared to none of those trained on the pelvic trainer (p = 0.04). CONCLUSIONS: There is no significant difference between the pelvic trainer and virtual reality trained medical students in proficiency to perform laparoscopic cystorrhaphy in a pig model, although both groups require considerably more training before performing this procedure clinically. The pelvic trainer training may be more user-friendly for the novice surgeon to begin learning these challenging laparoscopic skills.

LapED 4-In-1 silicone training aid for practicing laparoscopic skills and tasks: a preliminary evaluation.

OBJECTIVE: We developed a simple, inexpensive model to simulate four reconstructive laparoscopic procedures: pyeloplasty, vesicourethral anastomosis, bladder injury repair, and partial nephrectomy. MATERIALS AND METHODS: Liquid silicone was applied in layers to a mold to create the 4-in-1 model. A questionnaire evaluating its face and content validity was distributed to postgraduate urologists participating in a mini-residency program at the University of California-Irvine (UCI), and in the 2006 American Urological Association Hands-On course on reconstructive laparoscopic pyeloplasty. RESULTS: A total of 56 postgraduate urologists used the model and completed an evaluation questionnaire. Ninety-four percent (51/54) and 96% (48/50) agreed that the model was helpful for practicing laparoscopic pyeloplasty and urethrovesical anastomosis, respectively. Urologists who were experienced in either performing laparoscopic pyeloplasty (n = 6) or robot-assisted and/or laparoscopic prostatectomy (n = 11) would recommend this model to surgeons in training. Overall, 94% (48/51) and 96% (50/52) of the respondents would recommend this model for postgraduate surgeons and residents, respectively. CONCLUSION: We present a versatile model for practicing laparoscopic and robotic suturing and knot-tying skills in four reconstructive urologic procedures. Our results support the face and content validity of this model for performing pyeloplasty and vesicourethral anastomoses.