Balloon occlusion and hypothermic perfusion of the renal artery in laparoscopic partial nephectomy

Preliminary feasibility study of a new method of hypothermia in an experimental canine model

OBJECTIVE

To build up a new microcontroller thermoelectric system to achieve renal hypothermia.

MATERIAL AND METHODS

Renal hypothermia system was tested under in vivo conditions in the kidneys of ten Mongrel dogs. Ambient temperature was evaluated using two different microcontrollers. In order to ensure hypothermia in the renal parenchyma, selection can be made among 4 modules and sensors which detect the temperature of the area. The temperature range of the system was adjusted between -50°C and +50°C.

RESULTS

When single and double poles of the kidney were cooled, initial mean intraperitoneal temperature values were found 37.7°C for rectum and 36.5°C for renal cortex and medulla. After the temperature of the cooling module was set to 12°C, the module was placed on the poles of the kidney. After fifteen minutes, temperature was 15.4°C in the lower pole of the kidney, 28.1°C in the cortex of the other side and 29.2°C in the intramedullary region. The temperature was found to be 15°C in the vicinity and 26.1°C in the cortex across the module. After the system was stabilized, a very slight change was observed in the temperature.

CONCLUSION

Hypothermia system developed ensured desired cooling of the targeted part of the kidney; however, it did not cause a change in the temperature of other parts of the kidney or general body temperature. Thus, it was possible to create a long-term study area for renal parenchymal surgery.

Temporary targeted renal blood flow interruption using a reverse thermosensitive polymer to facilitate bloodless partial nephrectomy: a swine survival study

What's known on the subject? and What does the study add? Lumagel™ is a reverse thermosensitive polymer (RTP) that has previously been described in the literature as providing temporary vascular occlusion to allow for bloodless partial nephrectomy (PN) while maintaining blood flow to the untargeted portion of the kidney. At body temperature, Lumagel™ has the consistency of a viscous gel but upon cooling rapidly converts to a liquid state and does not reconstitute thereafter. This property has allowed for it to be used in situations requiring temporary vascular occlusion. Previous experience with similar RTPs in coronary arteries proved successful, with no detectable adverse events. We have previously described our technique for temporary vascular occlusion of the main renal artery, as well as segmental and sub-segmental renal branches, to allow for bloodless PN in either an open or minimally invasive approach. These experiments were performed in the acute setting. This study is a two-armed survival trial to assess whether this RTP is as safe as hilar clamping for bloodless PN. Surviving animals showed normal growth after using the RTP, absence of toxicity, no organ dysfunction, and no pathological changes attributable to the RTP. We conclude that Lumagel™ is as safe as conventional PN with hilar clamping, while adding the advantage of uninterrupted perfusion during renal resection.

OBJECTIVE

To examine whether randomly selected regions of the kidney could undergo temporary flow interruption with a reverse thermosensitive polymer (RTP), Lumagel™ (Pluromed, Inc., Woburn, MA, USA), followed by partial nephrectomy (PN), without adding risks beyond those encountered in the same procedure with the use of hilar clamping.

MATERIALS AND METHODS

A two-armed (RTP vs hilar clamp), 6-week swine survival study was performed. Four swine underwent PN using hilar clamps, while six underwent PN with flow interruption using the RTP. The RTP, administered angiographically, was used for intraluminal occlusion of segmental or subsegmental arteries and was compared with main renal artery clamping with hilar clamps. The resection site was randomized for each swine. Laboratory studies were performed preoperatively, and at weeks 1, 3 and 6. Before killing the swine, repeat angiography was performed with emphasis on the site of previous flow interruption. Gross and microscopic examination of kidney, liver, lung, heart, skeletal muscle was later performed, and the vessel that had supported the previous plug was examined.

RESULTS

All animals survived. No abnormal chemistry or haematology results were encountered over the 6 weeks. There were no surgical complications in either group. Using angiography we found 100% patency of vessels that had been occluded with the polymer 6 weeks previously for PN. The only gross or microscopic abnormalities were related to the renal resection and scar formation, and were similar in the two groups.

CONCLUSION

Targeted flow interruption with the RTP added no additional risk to PN while allowing bloodless resection and uninterrupted flow to untargeted renal tissue.

Temporary targeted hemostasis to facilitate bloodless partial nephrectomy

OBJECTIVE

To extend previous robotic-assisted techniques developed in the swine model to studies of laparoscopic and open partial nephrectomy conducted in pigs and calves, designed to encompass vessel diameters similar to those encountered in humans. Lumagel (Pluromed, Woburn, MA), a nontoxic polymer, can be administered intra-arterially under fluoroscopic guidance to obtain a bloodless operative field during partial nephrectomy while maintaining normal circulation to uninvolved renal tissue.

METHODS

A total of 10 animals (7 pigs and 3 calves) underwent flow interruption to the kidney, 2 with cross-clamping of the main renal artery, the remaining with Lumagel. Other than the first pig and calf, all the animals then underwent partial nephrectomy.

RESULTS

Using Lumagel, targeted blood flow interruption was achieved and circulation to the uninvolved renal tissue was maintained. Hemostasis lasted for ≥30 minutes. The surgical resection time averaged 11 minutes (range 10-13) and 23.3 minutes (range 9-40) in the open and laparoscopic groups, respectively. The estimated blood loss was negligible, with the exception of 2 cases, 1 in which an error in angiographic assessment led to an unoccluded vessel near the resection site and a second case in which a guidewire was inadvertently passed through a vessel. The interval to complete flow return, as determined by direct visualization of the kidney and its corresponding angiogram, averaged 7 and 2.5 minutes for Lumagel and arterial clamping, respectively.

CONCLUSION

Lumagel provides reliable and reproducible intraluminal blood flow interruption and flow restoration in both main and segmental renal arteries. By providing blood-free resection, the techniques described could facilitate partial nephrectomy without global renal ischemia.