The liver produces bile, which has many functions, including elimination of waste processed by the liver and digestion of fat. Bile is temporarily stored in the gallbladder (an organ situated underneath the liver) before it reaches the small bowel. Concretions in the gallbladder are called gallstones. Gallstones are present in about 5% to 25% of the adult Western population. Between 2% and 4% become symptomatic within a year. Symptoms include pain related to the gallbladder (biliary colic), inflammation of the gallbladder (cholecystitis), obstruction to the flow of bile from the liver and gallbladder into the small bowel resulting in jaundice (yellowish discolouration of the body usually most prominently noticed in the white of the eye, which turns yellow), bile infection (cholangitis), and inflammation of the pancreas, an organ that secretes digestive juices and harbours the insulin-secreting cells that maintain blood sugar level (pancreatitis). Removal of the gallbladder (cholecystectomy) is currently considered the best treatment option for patients with symptomatic gallstones. This is generally performed by key-hole surgery (laparoscopic cholecystectomy). Laparoscopic cholecystectomy is generally performed by inflating the tummy with carbon dioxide gas to permit the organs and structures within the tummy to be viewed so that the surgery can be performed. The gas pressure used to inflate the tummy is usually 12 mm Hg to 16 mm Hg (standard pressure). However, this causes alterations in the blood circulation and may be detrimental. To overcome this, lower pressure has been suggested as an alternative to standard pressure. However, using lower pressure may limit the surgeon's view of the organs and structures within the tummy, possibly resulting in inadvertent damage to the organs or structures. The review authors set out to determine whether it is preferable to perform laparoscopic cholecystectomy using low pressure or standard pressure. A systematic search of medical literature was performed to identify studies that provided information on the above question. The review authors obtained information from randomised trials only because such types of trials provide the best information if conducted well. Two review authors independently identified the trials and collected the information.
A total of 1092 patients were studied in 21 trials. Patients were assigned to a low pressure group (509 patients) or a standard pressure group (583 patients). The choice of treatment was determined by a method similar to the toss of a coin. Most of the trials included low surgical risk patients undergoing planned laparoscopic cholecystectomy.
Laparoscopic cholecystectomy could be completed successfully using low pressure in approximately 90% of people undergoing this procedure. No deaths were reported in either low pressure or standard pressure groups in eight trials that reported deaths (total of 434 patients in both groups). Seven trials with 394 patients described complications related to surgery. One participant experienced the outcome of serious adverse events (low pressure group 1/179, 0.6%; standard pressure group 0/215, 0%). Quality of life, return to normal activity, and return to work were not reported in any of the trials. The difference in the percentage of people undergoing conversion to open operation (from key-hole operation) between the low pressure group (2/269; 0.8%) and the standard pressure group (2/287; 0.7%) was imprecise. This was reported in 10 studies. No difference was noted in the length of hospital stay between the groups. Operating time was about two minutes longer (very low quality evidence) in the low pressure group than in the standard pressure group. Currently no evidence is available to support the use of low pressure pneumoperitoneum in low surgical risk patients undergoing planned laparoscopic cholecystectomy. The safety of low pressure pneumoperitoneum has to be established.
Quality of evidence
Only one trial including 140 participants was at low risk of bias (low chance of arriving at wrong conclusions because of study design). The remaining 20 trials were at high risk of bias (high chance of arriving at wrong conclusions because of trial design). The overall quality of evidence was very low.
Further well-designed trials are necessary, particularly in high surgical risk patients undergoing laparoscopic cholecystectomy.
Laparoscopic cholecystectomy can be completed successfully using low pressure in approximately 90% of people undergoing laparoscopic cholecystectomy. However, no evidence is currently available to support the use of low pressure pneumoperitoneum in low anaesthetic risk patients undergoing elective laparoscopic cholecystectomy. The safety of low pressure pneumoperitoneum has to be established. Further well-designed trials are necessary, particularly in people with cardiopulmonary disorders who undergo laparoscopic cholecystectomy.
A pneumoperitoneum of 12 to 16 mm Hg is used for laparoscopic cholecystectomy. Lower pressures are claimed to be safe and effective in decreasing cardiopulmonary complications and pain.
To assess the benefits and harms of low pressure pneumoperitoneum compared with standard pressure pneumoperitoneum in people undergoing laparoscopic cholecystectomy.
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded until February 2013 to identify randomised trials,
using search strategies.
We considered only randomised clinical trials, irrespective of language, blinding, or publication status for inclusion in the review.
Two review authors independently identified trials and independently extracted data. We calculated the risk ratio (RR), mean difference (MD), or standardised mean difference (SMD) with 95% confidence intervals (CI) using both fixed-effect and random-effects models with RevMan 5 based on available case analysis.
A total of 1092 participants randomly assigned to the low pressure group (509 participants) and the standard pressure group (583 participants) in 21 trials provided information for this review on one or more outcomes. Three additional trials comparing low pressure pneumoperitoneum with standard pressure pneumoperitoneum (including 179 participants) provided no information for this review. Most of the trials included low anaesthetic risk participants undergoing elective laparoscopic cholecystectomy. One trial including 140 participants was at low risk of bias. The remaining 20 trials were at high risk of bias. The overall quality of evidence was low or very low. No mortality was reported in either the low pressure group (0/199; 0%) or the standard pressure group (0/235; 0%) in eight trials that reported mortality. One participant experienced the outcome of serious adverse events (low pressure group 1/179, 0.6%; standard pressure group 0/215, 0%; seven trials; 394 participants; RR 3.00; 95% CI 0.14 to 65.90; very low quality evidence). Quality of life, return to normal activity, and return to work were not reported in any of the trials. The difference between groups in the conversion to open cholecystectomy was imprecise (low pressure group 2/269, adjusted proportion 0.8%; standard pressure group 2/287, 0.7%; 10 trials; 556 participants; RR 1.18; 95% CI 0.29 to 4.72; very low quality evidence) and was compatible with an increase, a decrease, or no difference in the proportion of conversion to open cholecystectomy due to low pressure pneumoperitoneum. No difference in the length of hospital stay was reported between the groups (five trials; 415 participants; MD -0.30 days; 95% CI -0.63 to 0.02; low quality evidence). Operating time was about two minutes longer in the low pressure group than in the standard pressure group (19 trials; 990 participants; MD 1.51 minutes; 95% CI 0.07 to 2.94; very low quality evidence).