IMPACT OF STANDARD PRESSURE AND LOW PRESSURE PNEUMOPERITONEUM IN SHOULDER PAIN FOLLOWING LAPAROSCOPIC CHOLECYSTECTOMY: A DOUBLE BLIND RANDOMIZED CONTROLLED TRIAL

Laparoscopic cholecystectomy is the standard of care of gall stone disease.However there are certain issues which although not life threatening, cause considerable post operative discomfort and anxiety to the patient. Post operative shoulder pain is one of such issue. 30-50% of patients of laparoscopic choecystectomy suffer from shoulder pain in the immediate post operative period. It commonly occurs in the first post operative day, although, it may persist for several days.. As the location of the pain is far from the surgical site, it causes considerable anxiety to the patients.  It also prolongs the hospital stay.

Shoulder pain is a unique complication following laparoscopic cholecystectomy. It is never seen following open surgery. Thus it appears to be an inherent problem associated with laparoscopy itself. The exact pathophysioslogy of shoulder pain following laparoscopic cholecystectomy is not well elucidated. Several hypotheses have been proposed. The most thought about hypothesis is that, pneumoperitoneum, in which cabondioxide gas (CO2) is used to inflate the abdomen, inflicts stretching trauma to the diaphragm and the peritoneum. This in turn causes referred pain to the shoulder (C4 distribution). The other possible theories are irritating effects of CO2 on the peritoneum and loss of suction effect between liver and diaphragm due to remaining pockets of CO2gas.

Pneumoperitoneum i.e. insufflations of abdominal cavity with CO2 gas is a primary step of all laparoscopic procedures. Pneumoperitoneum inflates the abdominal cavity thus provides working space for manipulation of laparoscopic instruments and aids in visualization of the internal organs. Commonly the intra-abdominal pressure is kept at around 14 mm Hg and it provides adequate working space and endoscopic visualization of the internal organs to the operating surgeon. However, it is hypothesized that this range of pressure causes stretching of the diaphragm injuring small vassels, nerves and muscle fibres and liberates inflammatory cytokines. Overall impacts of all these is referred pain along the C4 distribution, causing pain over the shoulder joint.

Several attempts have been made to reduce the incidence and severity of shoulder pain following laparoscopic cholecystectomy which include, maintaining low pressure pneumoperitoneum during the procedure , keeping a drainage in the abdominal cavity to remove the residual air, abdominal  wall lift, use of  nitrous  oxide instead of CO2, active gas aspiration, pulmonary recruitment manoeuvre, intra-peritoneal normal saline instillation and  low insufflation rate. Among all these, low pressure pneumoperitoneumn, low insufflations rate and pulmonary recruitment manueuvre are found to be effective in reducing the incidence of post operative shoulder pain  Several range of  pressure have been tried to reduce  the incidence of shoulder pain. Arbitrarily, a pressure range of 12-16mmHg has been designated as standard pressure and pressure less than 12 mmHg is termed as low pressure pneumoperitoneum.

The result of randomized trials comprising low pressure pneumoperitoneum and standard pressure pneumoperitoneum in reducing the incidence and severity of shoulder pain is variable. A few trials have shown significant reduction  in incidence of shoulder pain, while a few others have failed to show any major change. A chocrane meta-analysis of four randomized control trial showed significant reduction of incidence of shoulder pain following low pressure pneumoperitoneum. Another recent meta-analysis also favour use of low pressure (10mmHg) for pneumoperitoneum to reduce the incidence of shoulder pain.

One major concern for adopting low pressure pneumoperitoneum for regular laparoscopic procedure is its possible negative effect on working space and visualization of internal organs. In other words, will low pressure pneumoperitoneum compromise the safety of the procedure? The Cochrane analysis showed that the low pressure pneumoperitoneum prolonged the operation time by 2 minutes. However there was no difference in surgical complications rate or nor in the rate of conversion to open surgery. Thus it is imperative that low pressure pneumoperitoneum may be as safe as standard pressure pneumoperitoneum. However, no studies have systematically evaluated the surgeosn’s satisfaction pertaining to exposure and working space during laparoscopic cholecystecotmy at low pressure.

The present work is designed to evaluate the incidence and severity of shoulder pain following laparoscopic cholecystectomy at low pressure and standard pressure pneumoperitoneum as the primary end point. The patient and the doctor accessing  pain will be blinded about the allocated group of the patient.   The secondary end points will be to assess the operating time, surgeons satisfaction score pertaining to pneumoperitoneum, technical difficulty,  changes in intra-operative heart rate and blood pressure and post operative  abdominal pain.