Hemodynamic changes during laparoscopic cholecystectomy in patients with heart disease

[Comparative analysis of renal graft function after open vs. laparoscopic nephrectomy: experimental model]

INTRODUCTION

Living donor renal transplant reports a higher patient and graft survival in comparison to cadaver donor and represents a good alternative facing the current lack of organs for transplant.

GOALS

To analyze comparatively in an experimental model (pig) the influence of ischemia-reperfusion and functional outcome of renal graft retrieved by open Vs laparoscopic nephrectomy.

MATERIAL AND METHODS

30 lab pigs were nephrectomized (left kidney): 15 by laparoscopy and 15 by open surgery, as living donors, in a model of renal autotransplant. Renal blood flow (RBF) was measured by means of an electromagnetic probe and creatinine levels during the first week after the implant.

RESULTS

Comparative analysis of RBF during the immediate 60 min after unclamping showed a significant reduction of average RBF in laparoscopic group in comparison to open group (p < 0.001), with a more evident reduction of RBF in the laparoscopic group during the 5-min period after unclamping (p < 0.001) and a progressive recuperation of RBF during the 1st hour, slowest in laparoscopic group. Creatinine levels in the first week after the transplant decreased progressively from 1.3 to 0.8 mgrs/dl in the open group and from 2 to 1.1 mg/dl in laparoscopic group (p < 0.001).

CONCLUSIONS

Renal grafts retrieved by laparoscopy presents a more evident ischemia-reperfusion syndrome shown by a lower average RBF after unclamping and a significant deterioration of renal function during the first week after transplant.

[Comparative analysis about hemodynamic and renal blood flow effects during open versus laparoscopic nephrectomy. An experimental study]

BACKGROUND

The increase of intraabdominal pressure to 10 mmHg provokes a decrease of renal blood flow (RBF). Pneumoperitoneum during laparoscopic techniques with intra-abdominal pressure (IAP) to 15 mmHg, results in a decrease in RBF, urine output and glomerular filtration rate (GFR).

PURPOSE

Analyze the changes in RBF, urine output an GFR in a porcine experimental model during open vs laparoscopic nephrectomy.

MATERIALS AND METHODS

30 pigs (medium weigh= 22.6+3.2 Kg) were divided into two groups: Laparoscopic nephrectomy was performed using 15 pigs and open nephrectomy in 15 pigs, following a living donor nephrectomy autotransplantation model. Study parameters were urine volume and GFR baseline values, 30 and 60 minutes during nephrectomy. RBF was measured using an electromagnetic flow catheter around the main renal artery during the initial 60 minutes of nephrectomy.

RESULTS

The laparoscopic technique was associated with a significant reduction of RBF (80+2.7 vs 262+3 ml/min) (p<0.005), diuresis (42%) and GFR (38%), vs the open group.

CONCLUSIONS

Laparoscopic nephrectomy involves a significant reduction of RBF, GFR and diuresis, which is potentially transcendent in living donor nephrectomy and kidney transplantation.

Acute changes in renal function after laparoscopic gastric surgery for morbid obesity

BACKGROUND

Acute renal failure (ARF) is a serious complication that contributes to patient morbidity and may result in death. To date, no data are available regarding the predictive risk of ARF or its effect on the outcome of patients who undergo laparoscopic gastric bypass.

METHODS

The medical records of 1800 patients who underwent gastric bypass from July 1997 to July 2003 at a single institution were analyzed. The data collected included demographics, comorbid factors, operative details, and postoperative outcomes. Multivariant analysis was performed and the results were compared with those of 500 age-, gender-, and comorbidity-matched control patients who underwent similar operations.

RESULTS

The mean age was 50 +/- 8 years; 23 were men and 19 were women. Of the 1800 patients, 42 (2.3%) developed ARF after surgery. Dialysis was required in 6 patients, 2 of whom became dialysis dependent. ARF completely resolved in the remaining patients.

CONCLUSION

Primary ARF after laparoscopic gastric bypass is an uncommon complication, with an incidence of 2.3% in our institution. Patients with a body mass index >50, previous chronic renal failure, and long operating times and intraoperative hypotension are at the greatest risk of postoperative renal failure. All patients who had normal renal function preoperatively returned to normal renal function within 6 months.

Anuria during pneumoperitoneum in infants and children: a prospective study

INTRODUCTION

Transient oliguria during laparoscopic surgery is a known phenomenon. Currently, no data on the impact of pneumoperitoneum on renal function in children are available.

PATIENTS AND METHODS

Thirty children with normal kidney function, who underwent laparoscopic surgery, were included in a prospective study. A transurethral catheter was placed to measure urine output during and 6 hours after operation. Renal blood flow (resistive index) was evaluated by Doppler ultrasound of a segmental renal artery before surgery, every 15 minutes during laparoscopy, and after 24 hours. Blood and urine samples were studied before and 24 hours after surgery. Hemodynamic parameters were monitored continuously during standardized anesthesia, including a standardized intravenous infusion regimen.

RESULTS

Urine output decreased within 45 minutes of pneumoperitoneum in all patients. Of 8 children younger than 1 year, 7 (88%) developed anuria vs 3 of 22 (14%) children aged 1 to 15 years (P < .001). Nine children 1 year and older (32%) developed oliguria. There was a significant recovering in the mean urine output until 5 to 6 hours after pneumoperitoneum in both age groups. No significant alterations of the renal blood flow (resistive index) and the serum and urine levels of cystatin C, creatinine, and urea nitrogen were evident until 24 hours postoperatively. The volume of infusion during pneumoperitoneum did not correlate with urine output.

CONCLUSION

Pneumoperitoneum leads to anuria in most children younger than 1 year and to oliguria in about one third of older children. This is a completely reversible phenomenon. Urine output should not be taken into consideration for calculating intravenous fluid administration during pneumoperitoneum in children.

Effects of intra-abdominal CO2-insufflation on normal and impaired myocardial function: an experimental study

BACKGROUND

Intra-abdominal pressure (IAP) elevation during CO2-pneumoperitoneum increases cardiac afterload and may enhance dysfunction of the already compromised heart. This study focused on the effects of acute IAP increases on left and right ventricular loadings and contractility in the heart with impaired global function.

METHODS

Impairment of myocardial function (IMF) was pharmacologically induced in 16 pigs by administration of halothane and propranolol, while baseline arterial pressure was maintained by intravenous phenylephrine. Intra-abdominal pressure was gradually increased by 10 mmHg up to 30 mmHg in the supine position (IMF group 1, n = 8) or in a head-down tilted position (IMF group 2, n = 8). In two control groups with normal myocardial function, IAP was also increased in the supine position or the head-down tilted position. Cardiac function in all groups was assessed by epicardial echocardiography, intraventricular pressure measurements and pulmonary artery catheterization.

RESULTS

The increase in IAP was accompanied by a transient rise in LV end-systolic wall stress and reduced cardiac output significantly by 16-24% in all groups. In the IMF groups, LV end-diastolic transmural pressure increased by 34-60% to peak values of 24 mmHg, while cross-sectional LV end-diastolic areas remained unchanged. Increases in right ventricular end-diastolic volume and decreases in right ventricular ejection fraction as well as in cardiac output were most pronounced at IAP 20 mmHg and significantly stronger in both IMF groups than in the control groups (P < 0.001).

CONCLUSION

Following the acute elevation of IAP, the right ventricular volume load shifted more extensively in the IMF groups than in the animals with normal myocardial function. Myocardial function in the impaired heart may worsen during IAP elevation due to right ventricular load alterations rather than a LV afterload increase.

Catecholamine release during laparoscopic fundoplication with high and low doses of remifentanil

BACKGROUND

Reports on stress responses to laparoscopic surgery have been conflicting. Depth of anesthesia may influence the neuro-hormonal release, including catecholamines. Opioids depress general sympathetic activation in a dose-dependent manner. We investigated the hypothesis that remifentanil would depress the catecholamine response to pneumoperitoneum and laparoscopic surgery differently with a high dose (HD) compared with a low dose (LD).

METHODS

In a randomized, prospective study we investigated 18 ASA I-II patients undergoing laparoscopic fundoplication with an intra-abdominal pressure of 12 mmHg. The patients were randomized to receive either a LD (0.13 microg kg-1x min-1) or HD (0.39 microg kg-1 x min-1) of remifentanil with a target-controlled infusion (TCI) technique. Bispectral index of EEG (BIS) was maintained at 40-55 by propofol delivered by a TCI system. Arterial catecholamines were analyzed at different times during the procedure.

RESULTS

Norepinephrine increased equally in both groups during pneumoperitoneum and surgical intervention. Epinephrine stayed low in the HD-group, while increasing during surgery in the LD-group.

CONCLUSION

High dose of remifentanil depressed the epinephrine response to pneumoperitoneum and surgery, indicating no general activation of the sympathetic nervous system. Neither a LD nor HD of remifentanil depressed the norepinephrine response during pneumoperitoneum. This suggests a centrally independent release of norepinephrine.

Laparoscopic surgery in older adults

This article provides an overview of the current role of laparoscopic surgery in older patients. A retrospective review and analysis of the recent English-language literature on laparoscopic procedures with special attention devoted to those articles focused on geriatric patients was performed. Laparoscopic surgery has rapidly become the fastest-growing discipline within the surgical arena and new applications for laparoscopy continue to be reported. The primary benefits to patients of these developments are smaller scars, decreased postoperative pain, and more-rapid return to normal activity. As society ages, more older patients will present with pathology amenable to laparoscopic intervention. Several aspects of laparoscopy impose unique physiologic stresses and, as such, may alter surgical risk to the geriatric patient. In addition, older patients often have delayed surgical interventions because of more-conservative medical management or unusual symptomatology, which may further complicate the laparoscopic approach. These limitations may alter the risk-to-benefit ratio of laparoscopic versus open procedures. Despite this lack of elucidation of full-risk profiles, laparoscopic approaches should be considered regardless of a patient's age.

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.

Vasopressin antagonist improves renal function in a rat model of pneumoperitoneum

Pneumoperitoneum (PP) is associated with oliguria and increased plasma arginine vasopressin (AVP) levels. This study investigated the role of AVP in the pathogenesis of oliguria due to PP. Anesthetized and ventilated rats (n = 12) were subjected for 1 h to carbon dioxide PP with an intra-abdominal pressure of 8 mmHg or, as control, at 0 mmHg, before the determination of plasma AVP level. Another group of rats (n = 48) subjected to PP or control conditions was pretreated with the AVP V2 receptor antagonist, OPC-31260 (5 mg/kg), or vehicle, and their renal parameters were measured. Glomerular filtration rate (GFR) was determined by inulin clearance in an additional group of rats (n = 12) subjected to PP with or without pretreatment with OPC-31260. Rats subjected to PP had higher plasma AVP levels than did controls (17.3 +/- 8.1 pg/ml vs 1.5 +/- 0. 6 pg/ml, P < 0.05). In rats pretreated with vehicle, PP decreased urine output, excretion of water, and urea nitrogen, leading to reduced serum osmolality and serum sodium levels as well as elevated blood urea nitrogen levels. OPC-31260 pretreatment improved urine output, excretion of water, and urea nitrogen, thereby preventing changes in serum osmolality, serum sodium levels, and blood urea nitrogen levels. OPC-31260 pretreatment did not affect GFR. Results suggest that plasma AVP contributes to the oliguria due to PP. OPC-31260 may be useful in treating the water retention associated with PP.

Renal effects of carbon dioxide insufflation in rabbit pneumoretroperitoneum model

To determine the effects of carbon dioxide insufflation on renal function in a pneumoretroperitoneum model, 24 adult New Zealand rabbits were divided into four groups, six rabbits in each. The first group underwent a 2-hour CO2 insufflation at a pressure of 10 mm Hg in the retroperitoneal space after balloon dissection. In another group, the same procedure was maintained for 4 hours. In the sham-treated groups, the procedure was similarly carried out but without CO2 insufflation. In all four groups, serum and urine creatinine concentrations and renal artery and renal vein blood flow rates were determined separately at the beginning and at the end of the procedure and at 24 hours. Urine output was also recorded at the end of the procedure and at 24 hours. The serum creatinine in the 2- and 4-hour study groups had increased significantly at the end of the procedure, accompanied by a significant decrease in the urine creatinine value. Renal artery and renal vein blood flow rates and urine output were reduced in both groups during the study. All changes in the serum and urine creatinine, renal artery and vein flow rates, and urine output was more pronounced in the 4-hour group. All measures returned to their prestudy values by 24 hours. Pneumoretroperitoneum causes reversible renal dysfunction, which becomes more pronounced with prolonged insufflation. Further research is needed to show the impact of our findings in high-risk patients undergoing retroperitoneoscopic surgery.

Untoward cardiac changes during CO2 insufflation in laparoscopic cholecystectomies in low-risk patients

In the past decade, laparoscopic cholecystectomy has become the gold standard treatment for gallbladder disease. A debate has arisen about using CO2 to distend the abdomen because of negative effects on venous return to the heart and declining cardiac output. Some authors have supported the use of pulmonary artery catheters for intraoperative monitoring while others have recommended gasless techniques to avoid these negative effects for high-risk patients. In this study, four cases of bradycardia and/or asystole during CO2 pneumoinsufflation at the beginning of planned, elective laparoscopic cholecystectomies are described. These patients were ASA category II, without history of cardiac disease. To determine the frequency and any underlying common denominators, we analyzed these laparoscopic cholecystectomies. Each patient experienced bradycardia shortly after the start of the laparoscopic cholecystectomy. None had known cardiac disease or symptoms. Two were on antihypertensive medications, and one had experienced an episode of unexplained bradycardia 6 years earlier. These cases occurred during 725 laparoscopic cholecystectomies (0.6% approximately). Using the senior author's conversion rate of 10% to open cholecystectomies, the entire group would be approximately 800, and the risk of bradycardia upon induction of CO2 is 4 per 800, or 0.5%. Although cardiovascular changes were noted during laparoscopic gynecologic surgery approximately 20 years ago, only in the last few years have cardiovascular changes been reported during laparoscopic cholecystectomies. This study reviews four cases of bradycardia during CO2 insufflation in patients that were considered to be low-risk. Surgeons should be prepared to encounter such cardiovascular changes even with low-risk patients.

Cardiovascular changes during laparoscopic cholecystectomy: a study using transoesophageal Doppler monitoring

A transoesophageal Doppler cardiac output monitor was used to study the cardiovascular changes occurring during laparoscopic cholecystectomy in patients without (group A) or with (group B) a history of cardiovascular disease, i.e. hypertension, ischaemic heart disease or heart failure. Insufflation of the abdomen with carbon dioxide caused significant (P < 0.01) falls in mean cardiac index (17.9% in group A, 25.1% in group B) and mean stroke volume index (15.3% in group A, 21.2% in group B). Simultaneously, there was a significant (P < 0.05) increase in mean systolic blood pressure (19.4%) in group A. There were no other differences in the cardiovascular responses of the two groups. There was no correlation between systolic blood pressure and either cardiac index or stroke volume index. No significant complications or morbidity were associated with the use of the transoesophageal Doppler monitor. We conclude that the cardiovascular changes associated with insufflation are neither predictable by clinical assessment nor adequately determined by routine monitoring. We recommend the transoesophageal Doppler monitor for use in this situation.

Hemodynamic changes during laparoscopic cholecystectomy in patients with severe cardiac disease

STUDY OBJECTIVE

To evaluate the hemodynamic changes and need for pharmacologic interventions during laparoscopic cholecystectomy in patients with severe cardiac dysfunction.

DESIGN

Prospective open study.

SETTING

University hospital.

PATIENTS

17 ASA physical status III and IV patients with severe cardiac dysfunction undergoing elective laparoscopic cholecystectomy.

INTERVENTIONS

A standardized general anesthetic and surgical technique was used for all patients. In addition to routine monitoring, invasive hemodynamic monitoring included radial and pulmonary artery (PA) cannulation.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic parameters were recorded prior to induction of anesthesia, 5 minutes after induction of anesthesia but prior to incision, 5 minutes after carbon dioxide (CO2) insufflation and head-up tilt, every 10 minutes after change of position, after deflation of the abdomen and return to supine position, and 10 minutes after attaining supine position. Need for any pharmacologic interventions [to maintain mean arterial pressure (MAP) < 100 mmHg and/or systemic vascular resistance (SVR) < 2,000 dynes sec/cm-5, and/or cardiac index (CI) > 1.5 L/min/m2] and the incidence of any myocardial morbidity and mortality was noted. CI decreased significantly (p < 0.05) following insufflation and remained low until exsufflation. MAP, SVR, and PA occlusion pressure increased significantly (p < 0.05) after CO2 insufflation. Three of the 17 patients required administration of nitroglycerin to maintain the MAP and SVR within the accepted limits, one of whom also required administration of dobutamine to maintain CI. There was no myocardial morbidity or mortality in the perioperative period.

CONCLUSION

Laparoscopic cholecystectomy in patients with severe cardiac dysfunction results in significant hemodynamic changes.

Laparoscopic surgery and its potential for medical complications

Laparoscopic surgery is very popular among physicians and patients because this technique is associated with safety, shorter hospital stay, early return to normal activity, and cosmetic acceptance of the operative scar. Although the procedure involves minimal invasion and tissue damage, it has potentially serious complications, including cardiopulmonary effects that result mainly from hypercarbia and raised intraabdominal pressure caused by pneumoperitoneum. Absorbed carbon dioxide from the peritoneal cavity tends to cause acidosis. Leakage of the gas into tissue spaces may induce subcutaneous emphysema, pneumothorax, pneumomediastinum and pneumopericardium. Cardiac effects include arrhythmias, hypotension, cardiac arrest, gas embolism, pulmonary edema, and myocardial ischemia or infarction. Some of these effects, though rare, are serious and potentially fatal. Physicians should anticipate these problems in their patients undergoing laparoscopic procedures. This review discusses the technique of and physiologic considerations in laparoscopic surgery as well as its potential complications.

Inferior vena caval blood flow and cardiac hemodynamics during carbon dioxide pneumoperitoneum

BACKGROUND

The effects of carbon dioxide pneumoperitoneum on venous return and cardiac hemodynamics during laparoscopic surgery were studied.

METHODS

Twelve adult pigs underwent placement of an electromagnetic flow meter across the infrarenal vena cava (IVC) as well as placement of Swan Ganz and arterial monitoring catheters. Measurements of the flow through infrarenal IVC, cardiac output (CO), pulmonary capillary wedge pressure (PCWP), mean arterial pressure (MAP), and heart rate were recorded at baseline, 5 and 60 min following insufflation to 15 mmHg with CO2, and 5 min following desufflation. Stroke volumes and systemic vascular resistance (SVR) were calculated as well.

RESULTS

Flow through the IVC dropped by 24 and 31% at 5 and 60 min (p = 0.03 and 0.02, respectively). Paradoxically, cardiac output rose by 14 and 28% at 5 and 60 min (p = 0.03 at 60 min). Central venous and pulmonary capillary wedge pressures rose transiently by 35 and 36% at 5 min before returning to baseline (p < 0.01). Mean arterial pressure and heart rate remained relatively constant during insufflation. Systemic vascular resistance diminished from 938 dynes/cm/s prior to insufflation to its nadir at 60 min of 650 dynes/cm/s (p < 0.01).

CONCLUSIONS

These observations suggest potentially complex interactions between the mechanical and systemic effects of the CO2 pneumoperitoneum on venous return. Transient elevations in cardiac filling pressures occur by an unknown mechanism, and a generalized enhanced inotropic state mediated via increased sympathetic outflow is observed in this hypercapnic anesthetized animal model.

Hemodynamic effects of prolonged abdominal insufflation for laparoscopic procedures

Abdominal insufflation for laparoscopic procedures leads to numerous hemodynamic effects. We focused on blood flow distribution and arterial and venous pressure changes during CO2 insufflation at an intra-abdominal pressure of 12 mm Hg. Three segments of the vascular system were investigated (intrathoracic, cranial extrathoracic, caudal extrathoracic) in supine animals at insufflation, during a 90-minute period of pneumoperitoneum, and at desufflation. Except for instrumentation of the animals, no further surgery was performed. At insufflation (+5 minutes), cardiac output increased from 2.7 +/- 0.5 to 3.3 +/- 1.1 L/min while heart rate decreased from 138 +/- 26 to 128 +/- 17 beats per minute. Increases in jugular venous (from 6 +/- 1 to 11 +/- 4 mm Hg) and atrial (right, from 7 +/- 1 to 12 +/- 3; left, from 12 +/- 4 to 17 +/- 5 mm Hg) pressures occurred uniformly during inspiration. The great variance in atrial pressures during ventilation was not associated with changes in stroke volume, as the effective transmural filling pressures remained nearly constant. The increase in femoral venous pressure occurring during both inspiration and expiration (from 10 +/- 2 to 18 +/- 4 mm Hg) exceeded the increase in right atrial and jugular venous pressures during inspiration. Parallel increases were noted in arterial pressures (carotid, from 119 +/- 15 to 129 +/- 9; femoral, from 122 +/- 16 to 133 +/- 10 mm Hg), left ventricular pressure (from 133 +/- 17 to 143 +/- 10 mm Hg), and carotid and femoral flow (carotid, from 174 +/- 71 to 195 +/- 70; femoral, from 66 +/- 25 to 73 +/- 40 (NS) mL/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiopulmonary function and laparoscopic cholecystectomy

This review analyzes the literature dealing with cardiopulmonary function during and pulmonary function following laparoscopic cholecystectomy in order to describe the patterns of changes in these functions and the mechanisms involved as well as to identify areas of concern and lacunae in our knowledge. Information was obtained from a Medline literature search and the annual meeting supplements of Anesthesiology, Anesth Analg, Br J Anaesth, and Can J Anaesth. The principal findings were that changes in cardiovascular function due to the insufflation are characterized by an immediate decrease in cardiac index and an increase in mean arterial blood pressure and systemic vascular resistance. In the next few minutes there is partial restoration of cardiac index and resistance but blood pressure and heart rate do not change. The pattern is the result of the interaction between increased abdominal pressure, neurohumoral responses and absorbed CO2. Pulmonary function changes are characterized by reduced compliance without large alterations in PaO2, but tissue oxygenation can be adversely affected due to reduced O2 delivery. A major difficulty in maintaining normocarbia is due to the abdominal distention reducing pulmonary compliance and to CO2 absorption. End tidal CO2 tension is not a reliable index of PaCO2, particularly in ASA III-IV patients. The pattern of lung function following LC is characterized by a transient reduction in lung volumes and capacities with a restrictive breathing pattern and the loss of the abdominal contribution to breathing. Atelectasis also occurs. These changes are qualitatively similar to but of a lesser magnitude than those following "open" abdominal operations. It is concluded that the changes in cardiopulmonary function during laparoscopic upper abdominal surgery lead us to suggest judicious invasive monitoring and careful interpretation in ASA III-IV patients. Lung function following extensive procedures in sick patients has not been reported.

Right atrial to left atrial shunt through foramen ovale during pneumoperitoneum for laparoscopic cholecystectomy

A 62-year old female patient in whom paradoxical right atrial to left atrial shunt flow through the foramen ovale was detected by transesophageal echocardiography during pneumoperitoneum for laparoscopic cholecystectomy was reported. This patient had a history of mitral valve replacement with residual tricuspid valve regurgitation. It was considered that the onset of paradoxical interatrial shunting through the foramen ovale might be caused not only by mechanical ventilation with positive end-expiratory pressure but also by pneumoperitoneum, especially in patients with heart disease, even if the intra-abdominal pressure was maintained at 12 mmHg.

Renal effects of CO2 insufflation: oliguria and acute renal dysfunction in a rat pneumoperitoneum model

OBJECTIVE

To determine the mechanism by which oliguria develops during raised intra-abdominal pressure secondary to CO2 insufflation, we created a rat pneumoperitoneum model.

METHODS

Male Sprague-Dawley rats (n = 67) were organized into three groups. Each group was subjected to abdominal pressures of 0 (control), 5, or 10 mm Hg, over one, two, and four hours. Fourteen additional rats underwent a two-hour period of 10 mm Hg insufflation pressure followed by desufflation to 0 mm Hg. Urine output (UO) and serum creatinine levels were measured both during insufflation at one, two, and four hours, and two, four, ten, and twenty-two hours following its release. These measurements were compared to control values at each time point. Ultrasonic flow probes placed around both the inferior vena cava (IVC) and abdominal aorta during insufflation characterized the effects of increased abdominal pressure on blood flow. The flow rate was determined at insufflation pressures of 0 (control, 100% flow) to 25 mm Hg.

RESULTS

Rats subjected to 10 mm Hg pressure had significant decreases in UO (oliguria) compared to controls for up to four hours (P < 0.01). There were no significant differences in UO in the control or 5 mm Hg groups over each time interval. While a reduction in UO was observed at two, four, and ten hours postrelease, significance was achieved only at ten hours (P < 0.006). By twenty-two hours postrelease, no differences in UO were observed. Serum creatinine elevations declined two hours postdesufflation. IVC flow was reduced by 92.9 percent at 10 mm Hg, while arterial flow decreased by 46.4 percent. Flow was restored to preinsufflation levels after release of pneumoperitoneum.

CONCLUSIONS

Oliguria can be produced in rats undergoing pneumoperitoneum. The renal effects of pneumoperitoneum are most likely related to renal vascular insufficiency from central venous compression.