A porcine model for renal hemodynamic study during laparoscopy

Saline-filled laparoscopic surgery: A basic study on partial hepatectomy in a rabbit model

BACKGROUND

There is still a poor understanding of the effects of pneumoperitoneum with insufflation of carbon dioxide gas (CO2) on malignant cells, and pneumoperitoneum has a negative impact on cardiopulmonary responses. A novel saline-filled laparoscopic surgery (SAFLS) is proposed, and the technical feasibility of performing saline-filled laparoscopic partial hepatectomy (LPH) was evaluated in a rabbit model.

MATERIAL AND METHODS

Twelve LPH were performed in rabbits, with six procedures performed using an ultrasonic device with CO2 pneumoperitoneum (CO2 group) and six procedures performed using a bipolar resectoscope (RS) in a saline-filled environment (saline group). Resection time, CO2 and saline consumption, vital signs, blood gas analysis, complications, interleukin-1 beta (IL-1β) and C-reactive protein (CRP) levels were measured. The effectiveness of the resections was evaluated by the pathological findings.

RESULTS

LPH was successfully performed with clear observation by irrigation and good control of bleeding by coagulation with RS. There were no significant differences in all perioperative values, IL-1βand CRP levels between the two groups. All pathological specimens of the saline group showed that the resected lesions were coagulated and regenerated as well as in the CO2 group.

CONCLUSIONS

SAFLS is feasible and provides a good surgical view with irrigation and identification of bleeding sites.

Deleterious Effects of Increased Intra-Abdominal Pressure on Kidney Function

Elevated intra-abdominal pressure (IAP) occurs in many clinical settings, including sepsis, severe acute pancreatitis, acute decompensated heart failure, hepatorenal syndrome, resuscitation with large volume, mechanical ventilation with high intrathoracic pressure, major burns, and acidosis. Although increased IAP affects several vital organs, the kidney is very susceptible to the adverse effects of elevated IAP. Kidney dysfunction is among the earliest physiological consequences of increased IAP. In the last two decades, laparoscopic surgery is rapidly replacing the open approach in many areas of surgery. Although it is superior at many aspects, laparoscopic surgery involves elevation of IAP, due to abdominal insufflation with carbonic dioxide (pneumoperitoneum). The latter has been shown to cause several deleterious effects where the most recognized one is impairment of kidney function as expressed by oliguria and reduced glomerular filtration rate (GFR) and renal blood flow (RBF). Despite much research in this field, the systemic physiologic consequences of elevated IAP of various etiologies and the mechanisms underlying its adverse effects on kidney excretory function and renal hemodynamics are not fully understood. The current review summarizes the reported adverse renal effects of increased IAP in edematous clinical settings and during laparoscopic surgery. In addition, it provides new insights into potential mechanisms underlying this phenomenon and therapeutic approaches to encounter renal complications of elevated IAP.

A prospective assessment of renal oxygenation in children undergoing laparoscopy using near-infrared spectroscopy

BACKGROUND

This study was designed to determine whether a decrease in renal oxygenation occurs during CO2 pneumoperitoneum in children with normal renal function undergoing laparoscopy.

METHODS

Near infrared spectroscopy (NIRS) probes were applied to both the lateral flank (T10-L2) and lateral cerebral area of all patients with normal renal function undergoing a laparoscopic procedure. Information was recorded in 5-s intervals for 15-min before, during, and for 15-min after pneumoperitoneum insufflation and desufflation. Simultaneously, additional hemodynamic parameters (arterial saturation, mean arterial pressure, end tidal CO2, and urine output) were recorded every 5-min. Pneumoperitoneum pressures used were: 0-1 month old, <6 mmHg; 2-12 months old, <8 mmHg; 1-2 years old, <10 mmHg, and 2-8 years old, <12 mmHg. The lowest possible pressure was used to obtain adequate vision.

RESULTS

Twenty-nine patients were enrolled in the study. Renal regional oxygen saturation (rSO2) did not decrease significantly between baseline (preinsufflation), insufflation, and desufflation of the pneumoperitoneum (p = 0.343). Meta-analysis of this data demonstrated a pooled weighted difference of -1.4 (-3.5 to 0.54), confirming no significant change. A significant increase in cerebral rSO2 occurred during the insufflation period of the CO2 pneumoperitoneum (p = 0.001). Heart rate (F = 11.05; p < 0.001) and mean arterial pressure (MAP) (F = 19.2; p < 0.001) also increased significantly during the laparoscopy. No significant correlation was identified between fluid input and urine output during the laparoscopy (r = 0.012; p = 0.953).

CONCLUSIONS

Renal hypoxia does not occur during laparoscopic surgery in children if the minimum age-appropriate intra-abdominal pressures are used. Alternative causes must account for the oliguria and anuria demonstrated in children undergoing laparoscopy.

Acute obstructive jaundice and chronic cirrhosis protect against the adverse renal effects of pneumoperitoneum: role of nitric oxide

BACKGROUND

Obstructive jaundice and cirrhosis are associated with impaired renal function. Previously we demonstrated that increased intra-abdominal pressure (IAP, pneumoperitoneum) in normal rats induced renal dysfunction. This study investigated the renal effects of pneumoperitoneum in rats with acute jaundice and cirrhotic rats.

METHODS

Following a baseline period, rats with obstructive jaundice or cirrhosis induced by acute or chronic bile duct ligation (BDL), respectively, and their sham-controls were subjected to consecutive IAPs of 10 and 14 mmHg for 45 min each. Urine flow (V), Na(+) excretion (UNaV), glomerular filtration rate (GFR), renal plasma flow (RPF), and urinary NO metabolites ([Formula: see text]) and cGMP (UcGMP) were determined.

RESULTS

Elevating IAP from 0 to 10 and 14 mmHg in normal rats caused IAP-dependent reductions in V, UNaV, GFR, RPF, [Formula: see text] and UcGMP. Basal renal function and hemodynamics were lower in rats with obstructive jaundice. In contrast to normal rats, application of elevated IAP of 10 and 14 mmHg significantly improved V, UNaV, GFR, RPF, and MAP along with increased [Formula: see text] and preserved UcGMP. Similarly, when identical IAP conditions were applied to cirrhotic rats, no deleterious changes in V, UNaV, GFR or RPF were observed.

CONCLUSIONS

Application of pneumoperitoneum to rats with acute BDL improves kidney function and renal hemodynamics. Likewise, increased IAP does not exert adverse renal effects in cirrhotic rats. These effects are distinct from the deleterious renal consequences of increased IAP in normal rats. Perturbations in the generation of NO/cGMP during IAP in normal rats but not in rats with BDL or cirrhosis may contribute to these differences.

Effect of pneumoperitoneum on renal tissue oxygenation and blood flow in a rat model

OBJECTIVES

To determine the correlation between the renal blood flow (RBF) and tissue oxygenation (PO(2)) at varying intra-abdominal pressures (IAPs) and to compare the effects on renal blood flow from carbon dioxide-induced pneumoperitoneum.

METHODS

Carbon dioxide pneumoperitoneum was established in Sprague-Dawley rats (n = 6). Licox oxygen/temperature tissue probes were laparoscopically inserted into the renal parenchyma, with the renal PO(2) and RBF recorded every 30 seconds while the IAP was gradually increased. Microprobes measuring the RBF, mean arterial pressures and serum pH were placed into the parenchyma to compare the effects of carbon dioxide pneumoperitoneum (n = 7) with that of open surgery (n = 6) and medical air pneumoperitoneum (n = 6).

RESULTS

Renal PO(2) was inversely related to the IAP (P < .001). Despite the reduction in IAP, the renal PO(2) in the recovery phase was lower than at baseline (P = .045). The renal PO(2) and RBF changed in a virtually identical pattern at varying levels of IAP (P > .05). The RBF significantly declined with a pneumoperitoneal pressure of 15 and 20 mm Hg (P = .022), regardless of the gas used to create the pneumoperitoneum. A partial reversal of the RBF occurred with a decrease of the IAP. The RBF in the open surgical arm remained unchanged. Although both the serum pH and the mean arterial pressure were inversely proportional to the IAP (P < .001), the mean arterial pressure was depressed to the greatest extent in the medical air group (P = .02).

CONCLUSIONS

These results have demonstrated that elevated IAP secondary to pneumoperitoneum causes significant renal hypoxia and decreased RBF. Additionally, this experiment has demonstrated the use of the Licox probes in monitoring the renal PO(2) and established a novel method for evaluating the effects of IAP on the kidney.

Targeting individual hemodynamics to maintain renal perfusion during pneumoperitoneum in a porcine model

BACKGROUND

Although aggressive fluid hydration prevents a decrease in renal cortical perfusion (RCP) during laparoscopic donor nephrectomy, excess fluid is deleterious. We assessed whether goal-directed fluid administration, based on hemodynamic measures, would maintain RCP during pneumoperitoneum with less fluid loading.

METHODS

In a pilot study of 7 pigs, goal-directed fluid administration was guided by monitoring of stroke volume (SV) by esophageal Doppler measurement. During 15 mmHg CO(2) pneumoperitoneum, a bolus of 5 mL/kg 0.9% NaCl was given when SV decreased to 90% of baseline. Next, 18 pigs were randomized into 3 groups: low fluid (5 mL/kg per hour), high fluid (25 mL/kg per hour) and goal directed. Urine output, heart rate, mean arterial pressure, cardiac output, SV, and RCP were recorded every 15 minutes.

RESULTS

Pilot data revealed mean RCP (mL/min per 100 g) was maintained (40 vs 39) during pneumoperitoneum using goal-directed therapy. In the randomized study, RCP was decreased in the low fluid group (43 vs 29; P= .02), but maintained in the high (46 vs 40) and goal-directed (42 vs 39) groups. Mean fluid administered in the goal-directed group during pneumoperitoneum was 10 mL/kg and only 3 of 6 of pigs required boluses. Urine output was decreased in all 3 groups.

CONCLUSION

A goal-directed strategy during pneumoperitoneum allows for tailored fluid administration and maintains RCP with lower volumes of intravenous fluid.

Effect of pneumoperitoneum on renal perfusion and function: a systematic review

BACKGROUND

The precise physiologic consequences of insufflating carbon dioxide into the abdominal cavity during laparoscopy are not yet fully understood. This systematic review aimed to investigate whether pneumoperitoneum results in decreased renal blood flow (RBF) or renal function.

METHODS

A literature search was conducted electronically using Medline, Embase, and the Cochrane libraries on 1 July 2005. Various combinations of the medical subject headings--renal blood flow, pneumoperitoneum, renal function, and laparoscopy--were searched in all three databases. Reference lists from articles fulfilling the search criteria were used to identify additional articles.

RESULTS

The literature search retrieved 20 articles concerning RBF and 25 articles concerning renal function during pneumoperitoneum. It was found that 17 of the 20 studies identified a decrease in RBF, and 20 of the 25 studies identified a decrease in renal function during pneumoperitoneum.

CONCLUSION

There appears to be sufficient evidence to conclude that both renal function and RBF are decreased during pneumoperitoneum. The magnitude of the decrease is dependent on factors such as preoperative renal function, level of hydration, level of pneumoperitoneum, patient positioning, and duration of pneumoperitoneum.

Elucidating the relationship between cardiac preload and renal perfusion under pneumoperitoneum

INTRODUCTION

Pneumoperitoneum is associated with a well-described decrease in renal blood flow, but it remains unclear whether a decrease in cardiac preload is responsible. Our aim was to characterize the relationship between cardiac preload and renal perfusion during pneumoperitoneum.

METHODS

Eleven pigs were submitted to three 30 minute study periods: 1) Baseline (n=11): no interventions, 2) Pneumoperitoneum (n=11): 12 mmHg CO2 pneumoperitoneum, 3) Preload Reduction: pneumoperitoneum and nitroglycerin infusion (n=8); or pneumoperitoneum and hemorrhage to a mean arterial pressure (MAP) of 40 mmHg (n=3). Echocardiographic measurements of left ventricular end-diastolic diameter (LVEDD) were used as an index of preload. Renal cortical perfusion (RCP) was measured using laser doppler flowmetry.

RESULTS

LVEDD decreased from 4.2 +/- 0.5 to 4.1 +/- 0.6 cm (p=0.02) with pneumoperitoneum and then to 4.0 +/- 0.5 cm (p=0.03) with the addition of nitroglycerin. There was no statistically significant change in RCP with pneumoperitoneum (33.5 +/- 8.4 to 28.5 +/- 8.4 ml/min/100g tissue, p=0.2), but it decreased to 18.5 +/- 11.3 ml/min/100g tissue (p=0.001) with the addition of nitroglycerin. The correlation between RCP and LVEDD was weak (0.35, p=0.003), whereas correlation between RCP and MAP was superior (R=0.59, p<0.0001).

CONCLUSIONS

While decreasing preload under extreme lab conditions also decreases RCP, simply creating a pneumoperitoneum of 12 mmHg does not. The decrease in renal blood flow associated with pneumoperitoneum is likely not solely a function of preload.

Does aggressive hydration reverse the effects of pneumoperitoneum on renal perfusion?

BACKGROUND

Although pneumoperitoneum (PP) decreases renal blood flow, it remains unclear whether this impacts renal function. Our aim was to characterize the effects of PP on renal perfusion and function using two fluid strategies for intravenous fluid administration.

METHODS

Twelve 30-kg pigs were randomized into two groups: maintenance (3 cc/kg/h of normal saline (NS)) and bolus (15 cc/kg/h + 20 cc/kg NaCl bolus prior to induction of PP). Pigs were studied in a blinded fashion for 30 min prior, 60 min during, and 30 min after release of 15 mmHg CO(2) PP. Cardiac output (CO) and stroke volume (SV) were measured using an esophageal Doppler probe, renal cortical perfusion (RCP) was measured with a laser Doppler probe on the right kidney, and renal function was measured using the fractional excretion of sodium (FeNa) and urine output. Statistical analysis was performed with area-under-the-curve (AUC) analysis and analysis of variance

RESULTS

AUC analysis revealed moderate effect size for CO (0.416) and small effect size for SV (0.366) and RCP (0.363), with decreases seen in the control group but not the bolus group. During PP, urine output increased in the bolus group (p = 0.04) but not in the control group; there was no difference in FeNa in either group.

CONCLUSION

Aggressive fluid hydration during CO(2) PP of 15 mmHg preserves CO, SV, and RCP while increasing urine output. No effect on renal function as measured by FeNa was observed in either group.

Effect of increasing cardiac preload, sympathetic antagonism, or vasodilation on visceral blood flow during pneumoperitoneum

BACKGROUND AND AIMS

An impaired visceral perfusion caused by pneumoperitoneum may contribute to morbidity after laparoscopic surgery. The following three therapeutic concepts: increasing cardiac preload, controlled vasodilation, or selective sympathetic antagonism, were evaluated regarding a possible increase of visceral blood flow during pneumoperitoneum with carbon dioxide.

METHODS

Forty three pigs were assigned to treatment with an increase of preload and vasodilation (group A) or selective sympathetic antagonism with esmolol (group B). In both groups, pigs were assigned to head-up, head-down, or supine position. Perfusion of the vena porta and renal artery was measured by transonic volume flow meters and documented before capnoperitoneum, after induction of a 14-mmHg capnoperitoneum in each body position, after controlled vasodilation with sodium nitroprusside, and after controlled increase of intravascular volume by colloidal infusion.

RESULTS

Increasing intravascular volume improved portal blood flow in all body positions (p<0.05), but not renal blood flow. Medication of esmolol did not alter the measured parameters in any body position compared to control. Vasodilation with sodium nitroprusside reduced renal blood flow in supine and in head-up position.

CONCLUSION

An optimal intravascular volume was most effective in improving portal blood flow during capnoperitoneum in this trial. Esmolol had no negative effects on portal and renal blood flow. Patients with renal dysfunction might be treated carefully with sodium nitroprusside during capnoperitoneum.

A porcine model of systemic and renal haemodynamic responses to infrarenal aortic cross-clamping

OBJECTIVES

cross-clamping of the infrarenal aorta is associated with complex haemodynamic disturbances. Several experimental models of aortic cross-clamping (AXC) have been described with heterogeneous results. The main purpose of this study was to establish an animal model in which infrarenal AXC could reproduce similar systemic and renal haemodynamic changes to those observed in humans.

METHODS

eleven anaesthetised pigs underwent AXC just below the renal arteries. Renal blood flow was measured using clearance of (131)I hippuran. Systemic and renal parameters were collected at 3 consecutive 30-min periods.

RESULTS

AXC did not alter the extraction fraction of (131)I hippuran but was accompanied by significant (13%) decrease in cardiac index (p = 0.005) and a 23% increase in mean arterial pressure (p = 0.005). AXC induced significant 135% increase in renal vascular resistance (p = 0.012) and a 35% decrease in renal blood flow (p = 0.016). This worsened after removal of the aortic clamp, whereas systemic variables returned to baseline levels.

CONCLUSIONS

this AXC animal model reproduces the changes observed in humans. It provides a reliable animal model which allows to investigate the underlying mechanisms of renal vasoconstriction and the effect of new drugs.

A função renal de ratos espontaneamente hipertensos submetidos ao pneumoperitônio

Objetivo: Estudar a função renal de ratos espontaneamente hipertensos submetidos ao pneumoperitônio com CO2. Métodos: Foram utilizados 60 ratos, sendo 30 Wistar SHR e 30 EPM-1 Wistar, com idade ao redor de quatro meses, com peso médio de 341g. A amostra foi distribuída em dois grupos, experimento (ratos hipertensos) e controle (ratos normotensos), de acordo com a linhagem, SHR e EPM-1 Wistar, respectivamente. Cada grupo foi redistribuído em dois subgrupos, com 15 animais cada, de acordo com a pressão de pneumoperitônio, 10 e 4mmHg. Os animais foram anestesiados e posicionados, dando início ao procedimento de cateterização da artéria femoral esquerda, que permitiu aferição da pressão arterial média e a coleta sanguínea durante todo o experimento. Após a anti-sepsia, procedeu-se à realização de incisão transversa de 5mm de comprimento na região central do abdome para introdução de trocarte de 2mm, por onde foi introduzida a agulha de Veress, permitindo a insuflação de CO2 até atingir a pressão estabelecida para cada grupo (4mmHg ou 10mmHg), que foi mantida durante uma hora, seguida por uma hora de desinsuflação. Ao término do período de desinsuflação todos os animais de todos os grupos, ainda sob efeito anestésico, foram submetidos à eutanásia por exanguinação, através do cateter arterial. As amostras de sangue foram coletadas em três fases: 1) após a cateterização, 2) após uma hora de pneumoperitônio, e 3) após uma hora de desinsuflação, sendo conduzidas ao laboratório para dosagens de uréia e creatinina. Resultados: Houve aumento da creatinina para o rato SHR durante pneumoperitônio com pressão de 10mmHg; já a uréia mostrou-se aumentada tanto para o SHR quanto para o Wistar, durante o pneumoperitônio com pressão de 10mmHg. Durante o pneumoperitônio com pressão de 4mmHg, a creatinina e a uréia mantiveram-se nos níveis basais. Conclusão: A função renal do SHR se altera de forma transitória, semelhante ao rato não-hipertenso quando submetido ao pneumoperitônio.

Dynamic study of the distribution of microcirculatory blood flow in multiple splanchnic organs in septic shock

OBJECTIVES

To study dynamic distribution of microcirculatory blood flow in multiple splanchnic organs during septic shock; to test the hypothesis that changes in microcirculatory blood flow in splanchnic organs correlate with changes in regional flow during septic shock.

DESIGN

A prospective, controlled, animal study.

SETTING

Animal laboratory in a university medical center.

SUBJECTS

Nine anesthetized and mechanically ventilated domestic pigs.

INTERVENTIONS

Systemic flow (cardiac output) was measured with thermodilution and regional (superior mesenteric artery) flow with transit time flowmetry. Local blood flow (microcirculatory flow) was continuously measured in splanchnic organs (gastric, jejunal, and colon mucosa, liver, and pancreas) and the kidney with multichannel laser Doppler flowmetry. Septic shock was induced with fecal peritonitis. After 240 mins of sepsis, intravenous fluids were administered to alter hypodynamic shock to hyperdynamic septic shock.

MEASUREMENTS AND MAIN RESULTS

In this severe septic shock model, systemic and regional flows decreased by approximately 50% during the first 240 mins. Similar reductions were recorded in microcirculatory flow in the mucosa of the stomach (-41%; p < .001) and colon (-47%; p < .001). In the jejunal mucosa, on the other hand, flow remained virtually unchanged. Microcirculatory flow was also significantly decreased in the liver (-49%; p < .001), pancreas (-56%; p < .001), and kidney (-44%; p < .001). Administration of intravenous fluids at 240 mins was followed by three-fold increases in systemic and regional flows (approximately 70% above baseline). In the jejunal mucosa, flow also increased significantly above baseline (42%; p < .001), whereas in the stomach and the colon, it barely reached baseline. Kidney blood flow increased to baseline, whereas pancreas and liver flows remained 26% (p < .05) and 34% (p < .001), respectively, below baseline.

CONCLUSION

Changes in microcirculatory blood flow in the splanchnic organs are heterogeneous, both in early hypodynamic and in hyperdynamic septic shock, and cannot be predicted from changes in systemic or regional flows. Microcirculatory blood flow in the jejunal mucosa remains constant during early septic shock, whereas pancreatic blood flow decreases significantly more than regional flow.

Acute renal failure following laparoscopic cholecystectomy: a case report

The carbon dioxide (CO2) pneumoperitoneum of laparoscopic surgery is a complex physiologic event associated with neuroendocrine, respiratory, cardiovascular, and renal disturbances, as well as compromised organ blood flow. A case is presented of a 67-year-old man with a history of chronic renal failure, renal tubular acidosis, and hypertension, who underwent an uneventful elective laparoscopic cholecystectomy that included 75 minutes of CO2 pneumoperitoneum of 15 mmHg pressure. Postoperatively, the patient developed acute renal failure from which he recovered within 2 weeks. In the absence of other evident precipitating factors, we suspect that the CO2 pneumoperitoneum played a causal role in the development of his acute renal failure. The potential seriousness of the physiologic insult of conventional CO2 pneumoperitoneum suggests that "minimal access" surgery is not necessarily "minimally invasive."

Abdominal wall lift versus carbon dioxide insufflation for laparoscopic resection of ovarian tumors

STUDY OBJECTIVE

To evaluate and compare changes in pulmonary mechanics and stress hormone responses between abdominal wall lift (gasless) and carbon dioxide (CO2) insufflation laparoscopic surgery during controlled general anesthesia.

DESIGN

Prospective, randomized clinical study.

SETTING

Operating rooms at a university medical center.

PATIENTS

12 ASA physical status I and II female patients undergoing laparoscopic resection of ovarian tumors.

INTERVENTIONS

Patients were divided into two groups of six each: the abdominal wall lift group and the CO2 pneumoperitoneum laparoscopic group. Following induction of anesthesia, patients were paralyzed and the trachea was intubated. Anesthesia was maintained with isoflurane and nitrous oxide (N2O) in oxygen. Throughout the procedure, patients were mechanically ventilated with a tidal volume of 10 ml/kg and a respiratory rate of 10 breaths per minute.

MEASUREMENTS AND MAIN RESULTS

During the laparoscopic procedure, arterial blood gases, acid-base balance, pulmonary mechanics, stress-related hormones, and urine output were measured and recorded. In the CO2 pneumoperitoneum group, arterial CO2 tension increased (p < 0.01), dynamic pulmonary compliance decreased (p < 0.01), peak inspiratory airway pressure increased (p < 0.01), and plasma epinephrine (p < 0.05), norepinephrine (p < 0.05), dopamine (p < 0.01), and antidiuretic hormones (p < 0.05) increased significantly during the laparoscopic procedure as compared to the abdominal lift group. Adrenocorticotropic hormone and cortisol increased as compared to baseline value in both groups (p < 0.05). Urine output was significantly less (p < 0.01) in the CO2 pneumoperitoneum group than in the abdominal wall lift group.

CONCLUSIONS

Abdominal wall lift laparoscopic surgery is physiologically superior to CO2 pneumoperitoneum laparoscopic surgery as seen during the conditions of this study. Abdominal wall lift laparoscopic surgery provides normal acid-base balance and a lesser degree of hormonal stress responses, it maintains urine output, and it avoids derangement of pulmonary mechanics.

Pneumoperitoneum produces reversible renal dysfunction in animals with normal and chronically reduced renal function

Laparoscopic surgery with intraperitoneal insufflation is associated with acute oliguria. Although in healthy patients, this impairment is transient and without any apparent sequelae, as the scope of laparoscopic surgery expands, subtle renal injury may become clinically significant, particularly when applications expand to patients with reduced baseline renal function. We have investigated the changes in renal function during and after pneumoperitoneum in animals with reduced renal mass to identify both acute alterations and long-term impairments, if any. Twelve swine underwent surgical reduction in renal mass to produce chronic renal insufficiency. Glomerular filtration rate (GFR) was determined by inulin clearance for each animal before and after ablation to establish the degree of renal impairment (mean 22%; range 18%-31% of normal). The animals were followed during a stepwise insufflation as a study of pneumoperitoneum-induced changes in chronic renal failure. Urine output declined dramatically (-80% at 20 mm Hg), the GFR fell (-63% at 20 mm Hg), and renal blood flow declined (mean -12%; range -9% to -19%) over the course of the test. These values did not return to baseline during a 90-minute observation period after release of the pneumoperitoneum. Acute renal failure occurred despite aggressive hydration with maintenance of central venous pressure and only modest changes in cardiac output. The animals were exposed to a 6-hour CO2 pneumoperitoneum to 20 mm Hg to model the insult of complex laparoscopy. This exposure resulted in elevation of the amount of N-methyl-beta-D-glucosaminidase being shed into the urine in addition to the previously indicated impairments. The animals were allowed to recover for 1 week, and then GFR was again measured. The GFR returned to the preexposure chronic renal failure levels for both the group as a whole and individual animals. The magnitude and duration of the alteration in urine output, GFR, and renal blood flow suggest that regulatory mechanisms rather than simple mechanical forces are involved in the acute changes. No long-term impact on renal function from the acute renal injury was identified, even in animals with existing renal insufficiency.