Laparoscopic ice slush renal hypothermia for partial nephrectomy: the initial experience

PURPOSE: We describe a novel technique of laparoscopic renal hypothermia with intracorporeal ice slush during partial nephrectomy as well as clinical experience with the initial 12 patients. MATERIALS AND METHODS: A total of 12 select patients with an infiltrating renal tumor who were candidates for nephron sparing surgery underwent transperitoneal laparoscopic partial nephrectomy with renal hypothermia. An Endocatch II (United States Surgical Corp., Norwalk, Connecticut) bag was placed around the mobilized kidney and its drawstring was cinched around the intact renal hilum. The renal artery and vein were occluded en bloc with a Satinsky clamp. The bottom of the engaged bag was retrieved through a 12 mm port site and opened, and ice slush was introduced within the bag to completely surround the kidney. After renal hypothermia was achieved laparoscopic partial nephrectomy was performed by duplicating open surgical techniques. Renal parenchymal temperature was measured using a thermocouple needle in 5 patients. Median tumor size was 3.2 cm (range 1.5 to 5.5), 6 tumors (50%) were central in location and an imperative indication for partial nephrectomy was present in 7 patients (58%). RESULTS: All procedures were successfully completed laparoscopically without open conversion. Median time to deploy the bag around the kidney was 7 minutes (range 5 to 20), the median volume of ice slush introduced was 600 cc (range 300 to 750) and the time needed to insert the ice slush was 4 minutes (range 3 to 10). Median blood loss was 200 cc, total ischemia time was 43.5 minutes (range 25 to 55) and total operative time was 4.3 hours (range 3 to 5.5). Nadir renal parenchymal temperature was 5C to 19C and the mean decrease in systemic temperature was 0.6C. Histopathology confirmed renal cell carcinoma in 11 patients (92%), of whom all had negative surgical margins. Intraoperative complications occurred in 2 initial patients, including partial bag slippage in 1 and Satinsky clamp malfunction in 1. Postoperatively renal scan confirmed a functioning ipsilateral kidney in all cases. CONCLUSIONS: To our knowledge we present the initial clinical report of laparoscopic renal hypothermia for partial nephrectomy. By replicating standard open surgical practice our intracorporeal ice slush technique has the potential to extend the scope of laparoscopic partial nephrectomy to more complicated renal tumors.     

Experiments with a bowl of saline: the hidden risk of hypothermic-osmotic damage during topical cardiac cooling

Some of the misconceptions in the application of cardiac hypothermia are that the temperature of cold normal saline solution is necessarily above 0 degrees C, cold saline solution and slush are relatively safe for living tissues, and normal saline will retain normal osmolality even if partially frozen. These postulates were examined in thermodynamic experiments that demonstrated three points: (1) The temperature of unfrozen saline solution may drop way below the freezing point. (2) When liquids and solid components of saline solution are separated, the components will become hypo-osmolar or hyperosmolar. (3) Ice chips and slush ice produced in the operating rooms may reach temperatures as low as -36 degrees C. We recommend that the possibility of these events should be taken into consideration whenever topical cardiac hypothermia is clinically applied.     

Renal hypothermia using ice slush for retroperitoneal laparoscopic partial nephrectomy

Renal hypothermia using ice slush for retroperitoneal laparoscopic partial nephrectomy was performed in 2 patients. A cylindrical device was secured in the enlarged port site. Through the device, ice slush was introduced and placed around the kidney. The nadir renal temperature under renal ischemia in the 2 patients was 18.4 degrees C and 25.8 degrees C.     

Mild hypothermia improves survival after prolonged, traumatic hemorrhagic shock in pigs

INTRODUCTION: Clinical studies have demonstrated improved survival after cardiac arrest with induction of mild hypothermia (34 degrees C). Infusion of ice-cold saline seems beneficial. The American Heart Association recommends therapeutic hypothermia for comatose survivors of cardiac arrest. For hemorrhagic shock (HS), laboratory studies suggest that mild hypothermia prolongs the golden hour for resuscitation. Yet, the effects of hypothermia during HS are unclear since retrospective clinical studies suggest that hypothermia is associated with increased mortality. Using a clinically relevant, large animal model with trauma and intensive care, we tested the hypothesis that mild hypothermia, induced with intravenous cold saline (ice cold or room temperature) and surface cooling, would improve survival after HS in pigs. METHODS: Pigs were prepared under isoflurane anesthesia. After laparotomy, venous blood (75 mL/kg) was continuously withdrawn over 3 hours (no systemic heparin). At HS 35 minutes, the spleen was transected. At HS 40 minutes, pigs were divided into three groups (n = 8, each): 1) Normothermia (Norm)(38 degrees C), induced with warmed saline; 2) Mild hypothermia (34 degrees C) induced with i.v. infusion of 2 degrees C saline (Hypo-Ice) and surface cooling; and 3) Mild hypothermia (34 degrees C), induced with room temperature (24 degrees C) i.v. saline (Hypo-Rm) and surface cooling. Fluids were given when mean arterial pressure (MAP) was <30 mmHg. At HS 3 hours, shed blood was returned and splenectomy was performed. Intensive care was continued to 24 hours. RESULTS: At 24 hours, there were two survivors in the Norm group, four in the Hypo-Ice group and seven in the Hypo-Rm group (p < 0.05 versus the Norm group, Log Rank). Time required to achieve 34 degrees C was 17 +/- 9 minutes in the Hypo-Ice group and 15 +/- 4 minutes in the Hypo-Rm group (NS). Compared with the Hypo-Rm group, the Hypo-Ice group required less saline during early HS (321 +/- 122 versus 571 +/- 184 mL, p < 0.05). The Hypo-Ice group also had higher lactate levels than the Hypo-Rm group (p < 0.05). Hypothermia did not cause any increase in bleeding compared with normothermia. CONCLUSION: Mild hypothermia during HS, induced by infusion of room temperature saline and surface cooling, improves survival in a clinically relevant model of HS and trauma. However, the use of iced saline in this model had detrimental effects and did not cool the animal more quickly than room temperature fluids. These findings suggest that optimal methods for induction of hypothermia need to be addressed for each potential indication, e.g. cardiac arrest versus HS.     

A pilot study of ice-slurry application for inducing laparoscopic renal hypothermia

OBJECTIVE: To assess, in a pilot study, the feasibility of delivering a microparticulate ice slurry (MPS) to provide regional hypothermia, as renal cooling during laparoscopic procedures is cumbersome and inefficient. MATERIALS AND METHODS: An ex vivo preparation was used to simulate the boundary conditions of a kidney. Four pig kidneys were placed onto a thin membrane overlying a constant temperature bath (37 degrees C) with parenchymal thermocouples. Renal surfaces were coated with MPS and temperatures recorded. In an in vivo pig model we assessed laparoscopic delivery and cooling ability of the MPS under physiological conditions. Kidneys in two pigs were laparoscopically exposed; thermocouple probes were placed throughout the kidney and the hilum was clamped. MPS was delivered through a modified 5-mm laparoscopic suction/irrigation cannula. Cortical and core body temperatures were measured. RESULTS: In the ex vivo study, the mean (sd) initial temperature was 37.1 (0.4) degrees C; the mean time to reach 15 degrees C was 10.3 (2.6) min and the mean nadir temperature was 13.0 (1.5) degrees C. In vivo, the MPS was delivered with no technical difficulty; the mean renal unit starting temperature and core body temperature were 37.2 degrees C and 37.0 degrees C, respectively. The mean (range) time to reach 15 degrees C was 16.5 (5.5-28.6) min. The mean nadir core body temperature was 34.0 degrees C. CONCLUSION: This initial study showed efficient and rapid induction of renal hypothermia using MPS delivered through 5-mm laparoscopic ports, with no technical difficulty. These exploratory pilot findings support further, larger scale, histopathological and renal functional investigations of topical ice slurries as a means of providing renal hypothermia in laparoscopic procedures.     

Upright posture reduces thermogenesis and augments core hypothermia

We recently reported that baroreceptor-mediated reflexes modulate thermoregulatory vasoconstriction during lower abdominal surgery. Accordingly, we examined the hypothesis that postural differences and the related alterations in baroreceptor loading similarly modulate the thermogenic (i.e., shivering) response to hypothermia in humans. In healthy humans (n = 7), cold saline was infused IV (30 mL/kg at 4 degrees C) for 30 min to decrease core temperature. Each participant was studied on 2 separate days, once lying supine and once sitting upright. Tympanic membrane temperature and oxygen consumption were monitored for 40 min after each saline infusion. The decrease in core temperature upon completion of the infusion in the upright posture position was 1.24 degrees C +/- 0.07 degrees C, which was significantly greater than the 1.02 degrees C +/- 0.06 degrees C seen in the supine position. The core temperature was reduced by 0.59 degrees C +/- 0.07 degrees C in the upright position but only by 0.37 degrees C +/- 0.05 degrees C in the supine position when the increase in oxygen consumption signaling thermogenic shivering occurred. Thus, the threshold temperature for thermogenesis was significantly less in the upright than the supine position. The gain of the thermogenic response did not differ significantly between the positions (363 +/- 69 mL. min(-1). degrees C(-1) for upright and 480 +/- 80 mL. min(-1). degrees C(-1) for supine). The skin temperature gradient was significantly larger in the upright than in the supine posture, suggesting that the peripheral vasoconstriction was augmented by upright posture. Plasma norepinephrine concentrations increased in response to cold saline infusion under both conditions, but the increase was significantly larger in the upright than in the supine posture. Baroreceptor unloading thus augments the peripheral vasoconstrictor and catecholamine response to core hypothermia but simultaneously reduces thermogenesis, which consequently aggravated the core temperature decrease in the upright posture. IMPLICATIONS: Upright posture attenuates the thermogenic response to core hypothermia but augments peripheral vasoconstriction. This divergent result suggests that input from the baroreceptor modifies the individual thermoregulatory efferent pathway at a site distal to the common thermoregulatory center or neural pathway.     

Laparoscopic ice slurry coolant for renal hypothermia

PURPOSE: We assessed the safety and efficacy of microparticulate ice slurry for laparoscopic hypothermia during renal ischemia in a single kidney porcine model. MATERIALS AND METHODS: A total of 18 farm pigs were randomized to 3 groups of 6 each. All groups underwent initial right laparoscopic nephrectomy, followed by 1 of 3 procedures on the left kidney. Group 1 underwent 90-minute hilar clamping under warm ischemia, group 2 underwent 90-minute hilar clamping under cold ischemia using laparoscopically delivered microparticulate ice slurry and control group 3 underwent hilar dissection, no clamping and no microparticulate ice slurry. Body and renal cortical temperatures were measured. Serum creatinine and the glomerular filtration rate were assessed preoperatively, and on postoperative days 1, 3, 8 and 15. RESULTS: Average time to achieve a renal temperature of 20C or less was 9.7 minutes and it remained constant during the 90-minute cold ischemia time. Mean serum creatinine was significantly higher in the warm ischemia group than in the cold ischemia and control groups on postoperative days 1 and 3. Additionally, mean serum creatinine in the cold ischemia and control groups was similar at all time points. The mean glomerular filtration rate was significantly lower in the warm ischemia group than in the cold ischemia and control groups on postoperative days 1, 3 and 8. The mean glomerular filtration rate in the cold ischemia group was lower than in the control group on postoperative day 1, while it was similar on postoperative days 3, 8 and 15. CONCLUSIONS: In the porcine model laparoscopic renal hypothermia achieved with microparticulate ice slurry was safe and efficient. It significantly decreased renal dysfunction secondary to an ischemic insult with no adverse effects or complications associated with microparticulate ice slurry use.     

Effect of induction rate for mild hypothermia on survival time during uncontrolled hemorrhagic shock in rats

BACKGROUND: Rapid induction of hypothermia has been shown to improve survival in uncontrolled hemorrhagic shock (UHS) rat studies. We hypothesized that prolonged induction of hypothermia would be equally beneficial for survival during UHS. METHODS: Light anesthesia was induced with halothane in 30 rats, and spontaneous breathing was maintained. Rectal temperature (Tr) was monitored and maintained at 38 degrees C. UHS was induced by blood withdrawal of 2.5 mL/100 g during a 15-minute period, followed by 75% tail amputation. Immediately after cutting the tail, rats were randomized into three groups of 10 rats each: Group 1, maintained at Tr 38 degrees C; group 2, passively cooled to 34 degrees C by exposure to room temperature (23 degrees C); and group 3, actively cooled to 34 degrees C by applying alcohol to the skin and under an electric fan. Next, rats were controlled at each target Tr and observed without fluid resuscitation until either death or a maximum of 240 minutes. RESULTS: Cooling rate was -0.09 +/- 0.01 degrees C/min in group 2 and -0.36 +/- 0.9 degrees C/min in group 3 (p < 0.01). Mean survival time was 72 +/- 21 minutes in group 1 (38 degrees C), and was nearly doubled by hypothermia to 132 +/- 62 minutes for group 2 (p < 0.01 vs. group 1) and 150 +/- 69 minutes for group 3 (p < 0.01 vs. group 1). No significant difference in survival was noted between groups 2 and 3. Additional blood loss from the tail stump did not differ significantly between groups. CONCLUSION: Therapeutic mild hypothermia, induced either slowly (approximately -0.1 degrees C/min) or rapidly (approximately -0.4 degrees C/min) prolongs survival during lethal UHS in rats.     

Local saline infusion into ischemic territory induces regional brain cooling and neuroprotection in rats with transient middle cerebral artery occlusion

OBJECTIVE: The neuroprotective effect of hypothermia has long been recognized. Use of hypothermia for stroke therapy, which is currently being induced by whole-body surface cooling, has been limited primarily because of management problems and severe side effects (e.g., pneumonia). The goal of this study was to determine whether local infusion of saline into ischemic territory could induce regional brain cooling and neuroprotection. METHODS: A novel procedure was used to block the middle cerebral artery of rats for 3 hours with a hollow filament and locally infuse the middle cerebral artery-supplied territory with 6 ml cold saline (20 degrees C) for 10 minutes before reperfusion. RESULTS: The cold saline infusion rapidly and significantly reduced temperature in cerebral cortex from 37.2 +/- 0.1 to 33.4 +/- 0.4 degrees C and in striatum from 37.5 +/- 0.2 to 33.9 +/- 0.4 degrees C. The significant hypothermia remained for up to 60 minutes after reperfusion. Significant (P < 0.01) reductions in infarct volume (approximately 90%) were evident after 48 hours of reperfusion. In ischemic rats that received the same amount of cold saline systemically through a femoral artery, a mild hypothermia was induced only in the cerebral cortex (35.3 +/- 0.2 degrees C) and returned to normal within 5 minutes. No significant reductions in infarct volume were observed in this group or in the ischemic group with local warm saline infusion or without infusion. Furthermore, brain-cooling infusion significantly (P < 0.01) improved motor behavior in ischemic rats after 14 days of reperfusion. This improvement continued for up to 28 days after reperfusion. CONCLUSION: Local prereperfusion infusion effectively induced hypothermia and ameliorated brain injury from stroke. Clinically, this procedure could be used in acute stroke treatment, possibly in combination with intra-arterial thrombolysis or mechanical disruption of clot by means of a microcatheter.     

Improved lung preservation with cold air storage

Conventional topical slush cooling limits lung transport to 4 to 6 hours. For this canine study of an alternate air cooling system, 37 canine lungs were removed: 24 were placed in plastic bags, and inserted in a Transplanthermm container at core air temperatures (n = 6 lungs each) of (A) 4 degrees C, (B) 8 degrees C, (C) 12 degrees C, and (D) 20 degrees C; 6 were stored conventionally in ice slush (E); and 7 were transplanted immediately (F). After 8 hours, the stored lungs were transplanted and the contralateral pulmonary artery was ligated. Survival, arterial oxygen tension, and extravascular lung water were monitored at 15 minutes and every hour for 4 hours. Four-hour survival was 100% in groups A, B, and F; 83% in group C, 50% in group D, and 17% in group E. The mean arterial oxygen tension at 1 hour was lower in group E (6.4 +/- 2.4 kPa) than in group A (39.8 +/- 13.2 kPa) (p = 0.0002) or in group F (42.0 +/- 16.2 kPa) (p = 0.0035). Extravascular lung water in group E was higher at 15 minutes (15.44 +/- 5.63 mL/kg) than in group A (3.76 +/- 0.63 mL/kg) (p = 0.0001) and group F (4.69 +/- 1.65 mL/kg) (p = 0.003). Cold air storage appears to provide better lung preservation than hypothermic immersion in ice slush.     

Ultrashort intracorporeally maneuverable cryoprobes for laparoscopic renal cryoablation in the porcine model

AIM: To determine the feasibility and efficacy of laparoscopic renal cryosurgery using a novel ultrathin ultrashort intracorporeal cryoprobe in a porcine model. MATERIAL AND METHODS: Novel cryoprobes 4 cm in length and 1.5 mm in diameter were manipulated intracorporeally after insertion via a designated 15 mm laparoscopic port. Renal cryoablative lesions were induced laparoscopically in four 40 kg female piglets. We correlated between intraoperative temperature, ice ball geometry, intraoperative ultrasonographic properties, and histology. RESULTS: Laparoscopic manipulation of the cryoprobes was straightforward. No port site bleeding occurred during insertion, freezing, thawing or upon removal of the probes. The 0 degrees C, -20 degrees C, and -40 degrees C isotherms were measured at 6, 8, and 12 mm from the probe circumferentially. Ice-ball volume stabilization as determined by ultrasound occurred after 10 min of activation. Lower temperatures were reached after 10 min of probe activation as compared with 5 min (ice ball diameter 30 mm, DeltaT = 13-21 degrees C). Using a second 10-min-long freeze cycle resulted in a 14-22 degrees C lower temperature within the ice ball compared to a single cycle. Full coagulative necrosis was noted in the areas between the inserted probes with an additional 1-2 mm circumferential rim of severe tubular damage and apoptosis. CONCLUSIONS: Our novel cryoprobe can be used effectively and conveniently in laparoscopic renal cryosurgery. Considering the size of the cryogenic lesion, using a cluster of probes may be advisable.     

Rapid body cooling by cold fluid infusion prolongs survival time during uncontrolled hemorrhagic shock in pigs

OBJECTIVE: The purpose of this study was to examine whether cold fluid infusion could rapidly decrease the core temperature and prolong survival during uncontrolled hemorrhagic shock in pigs. METHODS: Fourteen pigs under light halothane anesthesia and spontaneous breathing underwent initial blood withdrawal of 25 mL/kg over 15 minutes, followed by uncontrolled hemorrhage (5-mm aortotomy). Immediately after the aortotomy, the pigs were randomized to receive 500 mL lactated Ringer's solution at either 4 degrees C (group 1, n = 7) or 37 degrees C (group 2, n = 7) over 20 minutes through the internal jugular vein and observed until their death or for a maximum of 240 minutes. RESULTS: The pulmonary artery temperature of group 1 decreased to 35.5 degrees +/- 0.3 degrees C after the infusion, then remained at 35.5 degrees C during the observation period. Pulmonary artery temperature values of group 2 remained at around 37.5 degrees C throughout the experiment. The mean survival time was 220 +/- 45 minutes in group 1 versus 136 +/- 64 minutes in group 2 (p < 0.05, life table analysis). The additional intraperitoneal blood loss of group 1 was similar to that of group 2 (9 +/- 4 g/kg vs. 10 +/- 5 g/kg). CONCLUSION: In lightly anesthetized pigs during uncontrolled hemorrhagic shock, infusion with 4 degrees C lactated Ringer's solution (which seems to be feasible in the clinical setting) decreases the core temperature rapidly and prolongs survival.     

Transureteral saline perfusion to obtain renal hypothermia: potential application in laparoscopic partial nephrectomy.

BACKGROUND: Partial nephrectomy for resection of renal tumors often requires renal artery clamping and external renal cooling using ice-slush. Laparoscopic surgery precludes traditional ice-slush cooling. To facilitate renal cooling during laparoscopic partial nephrectomy, we investigated a method of intrarenal cooling by retrograde transureteral iced saline perfusion. METHODS: Open laparotomy was performed in 6 pigs. After atraumatic renal artery clamping, one kidney was cooled externally by using standard ice-slush; the other was cooled transureterally. For transureteral cooling, the ureter was cannulated with a double lumen 12 Fr catheter. Chilled saline (4 degrees C) irrigation was flushed through the catheter into the renal pelvis (16.7 mL/min) and allowed to drain via the second lumen of the catheter. Using a 30-gauge hypodermic thermometer, kidney temperatures were measured at 5-minute intervals for 30 minutes at 3 locations and 2 depths (0.5 cm and 1.5 cm). The animals were euthanized, and the kidneys were harvested for histologic examination. RESULTS: Renal cooling was achieved with both external and transureteral cooling. However, lower (5.0 versus 26.1 degrees C, P<0.001) parenchymal temperatures were achieved more rapidly with external renal cooling. During transureteral cooling, medullary (1.5 cm) temperatures were lower than cortical (0.5 cm) temperatures were; this difference did not reach statistical significance. CONCLUSIONS: Although renal hypothermia can be achieved by transureteral iced saline infusion, external cooling by using ice-slush appears to be more efficient in the porcine model. With refinement of the technique, intrarenal cooling via a transureteral approach may allow more effective cooling of the renal medulla, and limit warm ischemia during laparoscopic partial nephrectomy.     

Cold-blood potassium cardioplegia: evaluation of glutathione and postischemic cardioplegia

Potassium (34 mEq/L) cardioplegia was induced with cold blood (CBK) in three groups of six dogs undergoing 60 minutes of myocardial ischemia at a systemic temperature of 27 degrees +/- 2 degrees and a myocardial temperature of 7 degrees +/- 2 degrees C (crushed ice). Group 1 (CBK) animals were reperfused initially with 400 ml cold blood over 8 to 10 minutes at increasing pressures of up to 75 mm Hg. Group II (CBK-K) dogs were reperfused in the same manner as Group I with the addition of potassium chloride, 30 mEq/L. In Group III (CBKG-KG) glutathione, 30 mg/100 ml, was added to both the pre- and postischemic perfusions with CBK. After 30 minutes of reperfusion control studies were repeated. Heart rate, peak systolic pressure, rate of rise of left ventricular pressure, maximum velocity of contractile element, pressure-volume curves, coronary flow distribution, muscle stiffness, and heart water were not significantly different from control values. Total coronary flow and myocardial uptake of oxygen, lactate, and pyruvate did not serve to separate the three groups; the same was true for right ventricular creatine phosphate, adenosine triphosphate, and adenosine diphosphate during ischemia and recovery. Ultrastructural myofibrillar lesions were noted in all groups. thus, postischemic cardioplegia and use of a physiological reducing agent do not enhance CBK cardioplegia with topical and systemic hypothermia.     

Advances in laparoscopic partial nephrectomy

PURPOSE OF REVIEW: The advantages of the laparoscopic approach in the management of kidney tumors are unequivocal and the role of laparoscopy in nephron-sparing surgery is evolving. In a selected group of patients with small exophytic renal tumors laparoscopic partial nephrectomy became an alternative to open partial nephrectomy. However, the application of laparoscopic partial nephrectomy to larger, centrally located tumors or tumors in unfavorable sites is limited by the difficulty of achieving adequate, prompt collecting system closure and hemostasis with a limited warm ischemia time. The most recent developments in laparoscopic partial nephrectomy are the subject of this review. RECENT FINDINGS: A number of sealant products have been used as an adjunct or principal hemostatic agent in the animal model. Their application in the clinical setting remains limited to small parenchymal bleeding; larger vessels and pelvicaliceal openings are better managed by vascular clamping and intracorporeal suturing. Vascular clamping confers warm ischemia, and attempts at renal hypothermia included cold kidney irrigation through either a ureteral stent or a renal artery cannulation, and the application of ice slush for parenchymal surface cooling. SUMMARY: Laparoscopic partial nephrectomy is technically demanding; efforts directed towards facilitating hemostasis, improving renal cooling or shortening the warm ischemia time will expand its indications further.     

Renal hypothermia achieved by retrograde endoscopic cold saline perfusion: technique and initial clinical application

We describe the technique and initial clinical results with application of a novel method to achieve renal parenchymal hypothermia using retrograde ureteral access. A 38-year-old man was scheduled to undergo an open right partial nephrectomy for renal cell carcinoma. Before the open procedure, a ureteral access sheath was advanced to the ureteropelvic junction under fluoroscopic guidance; through the access sheath, a 7.1F pigtail catheter was also advanced. After clamping the renal artery and vein, ice-cold saline (-1.7 degrees C) was circulated through the access sheath and drained via the 7.1F pigtail catheter; renal cortical and medullary parenchymal temperatures were measured using thermocouples. This technique of intrarenal cooling achieved a renal cortical temperature of 24 degrees C and a medullary temperature of 21 degrees C. The endoscopic procedure required an additional 35 minutes of operation time to complete. Histopathologic investigation of the specimen revealed no associated damage to the ureteral urothelium from access sheath placement or to the collecting system urothelium from exposure to ice-cold saline irrigation. Retrograde endoscopic renal hypothermia is feasible and effective. The technique requires no novel equipment or special surgical skills. This method can be applied to patients undergoing open or laparoscopic complex renal ablative and reconstructive procedures that require renal hypothermia.     

Renal hypothermia in situ. Comparison between surface and perfusion cooling concerning renal function in pigs (author's transl)]

There are 2 competing methods for cooling the kidney in situ during surgical ischemia: from without by applying ice to the renal surface and from within by perfusing the renal artery. The latter procedure is said to be superior in protecting renal function. Herein the protective effect on renal function of both methods are compared. Pigs of 15--25 kg weight underwent nephrectomy on one side. The remaining kidney was subjected to cold ischemia during 90 minutes while perfusion- or surface cooling was performed. For perfusion cooling the aorta was punctured and the catheter introduced into the renal artery. The perfusing liquid consisted of a physiologic electrolyt solution (Ringer-Lactate) with heparin kept at a temperature of 3--5 degrees C. The initial perfusion lasted 10 minutes and resulted in a median renal core temperature of 23 degrees C. Then the kidney was put on a cooling pad and every 15 minutes again perfused for one minute. For surface cooling sterile melting ice made of glucose solution 5% was applied directly to the kidney. The renal core temperature could be kept at 15--20 degrees C. The two methods of hypothermia were judged by comparing the serum creatinine levels and the I131-hippuran clearances one month after surgery. There was no difference whatever as analysed by the t-test. Hypothermia by applying ice to the renal surface therefore proved to be equivalent to hypothermia by perfusion. Moreover it is much simpler.     

Rapid hypothermic aortic flush can achieve survival without brain damage after 30 minutes cardiac arrest in dogs

BACKGROUND: Neither exsanguination to pulselessness nor cardiac arrest of 30 min duration can be reversed with complete neurologic recovery using conventional resuscitation methods. Techniques that might buy time for transport, surgical hemostasis, and initiation of cardiopulmonary bypass or other resuscitation methods would be valuable. We hypothesized that an aortic flush with high-volume cold normal saline solution at the start of exsanguination cardiac arrest could rapidly preserve cerebral viability during 30 min of complete global ischemia and achieve good outcome. METHODS: Sixteen dogs weighing 20-25 kg were exsanguinated to pulselessness over 5 min, and circulatory arrest was maintained for another 30 min. They were then resuscitated using closed-chest cardiopulmonary bypass and had assisted circulation for 2 h, mild hypothermia (34 degrees C) for 12 h, controlled ventilation for 20 h, and intensive care to outcome evaluation at 72 h. Two minutes after the onset of circulatory arrest, the dogs received a flush of normal saline solution at 4 degrees C into the aorta (cephalad) via a balloon catheter. Group I (n = 6) received a flush of 25 ml/kg saline with the balloon in the thoracic aorta; group II (n = 7) received a flush of 100 ml/kg saline with the balloon in the abdominal aorta. RESULTS: The aortic flush decreased mean tympanic membrane temperature (Tty) in group I from 37.6 +/- 0.1 to 33.3 +/- 1.6 degrees C and in group II from 37.5 +/- 0.1 to 28.3 +/- 2.4 degrees C (P = 0.001). In group 1, four dogs achieved overall performance category (OPC) 4 (coma), and 2 dogs achieved OPC 5 (brain death). In group II, 4 dogs achieved OPC 1 (normal), and 3 dogs achieved OPC 2 (moderate disability). Median (interquartile range [IQR]) neurologic deficit scores (NDS 0-10% = normal; NDS 100% = brain death) were 69% (56-99%) in group I versus 4% (0-15%) in group II (P = 0.003). Median total brain histologic damage scores (HDS 0 = no damage; > 100 = extensive damage; 1,064 = maximal damage) were 144 (74-168) in group I versus 18 (3-36) in group II (P = 0.004); in three dogs from group II, the brain was histologically normal (HDS 0-5). CONCLUSIONS: A single high-volume flush of cold saline (4 degrees C) into the abdominal aorta given 2 min after the onset of cardiac arrest rapidly induces moderate-to-deep cerebral hypothermia and can result in survival without functional or histologic brain damage, even after 30 min of no blood flow.     

High-flow venovenous rewarming for the correction of hypothermia in a canine model of hypovolemic shock

BACKGROUND: Continuous arteriovenous rewarming (CAVR) has been shown to effectively reverse hypothermia; however, its use is limited in the setting of profound hypotension. We have evaluated the effectiveness of high-flow venovenous rewarming (HFVR) using bypass for the correction of hypothermia in a hypotensive canine model and compared these results to CAVR. METHODS: Eight dogs, randomly assigned to either HFVR or CAVR, were cooled to a core temperature of 29.5 degrees C and then bled to a mean arterial pressure of 55 mm Hg. Rewarming was then initiated and the time required for blood, liver parenchyma, and esophageal (core) temperature to reach 36 degrees C was recorded. RESULTS: Mean flow rates were 1,536 +/- 667 mL/min for HFVR and 196 +/- 35 mL/min for CAVR (p = 0.007). Time in minutes to rewarm to 36 degrees C for the HFVR versus the CAVR groups, respectively, were as follows: blood, 12 +/- 2 versus 99 +/- 19; liver, 21 +/- 3 versus 102 +/- 16; and esophageal, 25 +/- 6 versus 125 +/- 17 (all < 0.001). CONCLUSION: HFVR is an effective method for rapid rewarming in a profoundly hypothermic, hypotensive animal model and may have clinical utility in patients presenting with hypovolemia/hypotension complicated by hypothermia.     

The importance of brain temperature in patients after severe head injury: relationship to intracranial pressure,cerebral perfusion pressure,cerebral blood flow,and outcome

Brain temperature was continuously measured in 58 patients after severe head injury and compared to rectal temperature, intracranial pressure, cerebral blood flow, and outcome after 3 months. The temperature difference between brain and rectal temperature was also calculated. Mild hypothermia (34-36 degrees C) was also used to treat uncontrollable intracranial pressure (ICP) above 20 mm Hg when other methods failed. Brain and rectal temperature were strongly correlated (r = 0.866; p < 0.001). Four groups were identified. The mean brain temperature ranged from 36.9 +/- 0.4 degrees C in the normothermic group to 38.2 +/- 0.5 degrees C in the hyperthermic group, 35.3 +/- 0.5 degrees C in the mild therapeutic hypothermia group, and 34.3 +/- 1.5 degrees C in the hypothermia group without active cooling. The mean DeltaT(br-rect) was positive for patients with a T(br) above 36.0 degrees C (0.0 +/- 0.5 degrees C) and negative for patients during mild therapeutic hypothermia (-0.2 +/- 0.6 degrees C) and also in those with a brain temperature below 36 degrees C without active cooling (0.8 +/- -1.4 degrees C) - the spontaneous hypothermic group. The cerebral perfusion pressure (CPP) was increased significantly by active cooling compared to the normothermic and hyperthermic groups. The mean cerebral blood flow (CBF) in patients with a brain temperature between 36.0 degrees C and 37.5 degrees C was 37.8 +/- 14.0 mL/100 g/min. The lowest CBF was measured in patients with a brain temperature <36.0 degrees C and a negative brain-rectal temperature difference (17.1 +/- 14.0 mL/100 g/min). A positive trend for improved outcome was seen in patients with mild hypothermia. Simultaneous monitoring of brain and rectal temperature provides important diagnostic and prognostic information to guide the treatment of patients after severe head injury (SHI) and the wide differentials that can develop between the brain and core temperature, especially during rapid cooling, strongly supports the use of brain temperature measurement if therapeutic hypothermia is considered for head injury care.