Comparative study of low pressure versus standard pressure pneumoperitoneum in laparoscopic cholecystectomy

During laparoscopic cholecystectomy adequate working space is required in the abdomen for good exposure that contributes to satisfactory results and patient safety. Common methods to create working space in the abdomen are pneumoperitoneum and abdominal wall lifting methods such as the laparotensor and laparolift.[1] Pneumoperitoneum for laparoscopic cholecystectomy is most often created by insufflating carbon dioxide gas into the peritoneal cavity and then holding it at constant pressure till the end of surgery when it is released at the time of withdrawal of the ports.[1,2] Standard pressure pneumoperitoneum, employing a pressure range of 12-14 mm Hg, over prolonged periods has been associated with adverse effects such as decreased pulmonary compliance, altered blood gas parameters, impaired functioning of the circulatory system, raised liver enzymes and renal dysfunction,and even increased intra-abdominal venous pressures.[3,4,5,6,7][

An emerging trend has been the use of low pressures for pneumoperitoneum in the range of 7-10 mm Hg instead of the standard pressure pneumoperitoneum in an attempt to lower the impact of pneumoperitoneum on human physiology while providing adequate working space.[6,7] This method appears to have little adverse effect on the cardiac and respiratory functions and is suitable for the elderly and for those with chronic cardiac or respiratory diseases. Other possible advantages of low pressures during pneumoperitoneum appear to be lower incidence of shoulder tip pain in the postoperative period and also better quality of life in the week following surgery [8,9,10,11,12].

However the lower pressures involved in the low pressure laparoscopic cholecystectomy might result in a less than adequate exposure of the operating field resulting in longer than usual operating time, higher rate of intraoperative complications and also possibly higher frequency of conversion to standard pressure laparoscopic cholecystectomy or open cholecystectomy.[8,9,10,11,12,13,14,15]

This study proposes to compare the use of the low pressure pneumoperitoneum (defined as 10 mm Hg) with the use of standard pressure pneumoperitoneum (defined as 14 mm Hg) in patients undergoing laparoscopic cholecystectomy in a prospective randomized manner. The main areas of interest will be the adequacy of operating field, intraoperative hemodynamic stability and postoperative course especially pain scores.

Methods

The study was carried out in the Department of General Surgery in a tertiary care hospital, in India, over a period of one year from July 2006 to June 2007. All consecutive patients with uncomplicated symptomatic gallstone disease tagged for laparoscopic cholecystectomy were included in the study.

Patients with acute cholecystitis and with complications of gallstone disease like gallbladder perforation, empyema, and common bile duct stone were excluded from the study. Ethical clearance from the Institute Ethics Committee was taken. The procedure was explained in detail and informed consent taken.

The study was done in a randomised prospective manner with a sample size of 60 patients. Patients were randomized into two groups using a random number table. One group with 30 patients underwent laparoscopic cholecystectomy with standard pressure pneumoperitoneum at 14 mm Hg while the other group with 30 patients underwent laparoscopic cholecystectomy with low pressure pneumoperitoneum at 10 mm Hg. The surgeries were performed by two experienced consultant surgeons. During the surgery the first port was inserted at a pressure of 14 mm Hg. In the standard pressure group, the pressure was taken up to 14 mm Hg whilst in the low pressure group the pressure was reduced to 10 mm Hg for the remaining duration of surgery. A standard laparoscopic cholecystectomy was performed with the insertion of four ports at the start of surgery. Intra-operative monitoring was performed by monitoring heart rate and blood pressure non-invasively every 5 minutes. Closure of the rectus sheath was done at 10 mm ports at the umbilicus site and at the epigastric site using absorbable sutures. Skin was approximated at all the port sites using staples.

The anaesthetic protocol was the same for both groups. Postoperative analgesia was administered in the form of diclofenac 12 hourly with additional doses where necessary. Patients were encouraged to become ambulatory early and were allowed oral intake six hours after surgery. They were discharged on day one following surgery.

At admission, the patient’s blood pressure and heart rate were noted. Intraoperative blood pressure and heart rate were noted. The difference between the readings at admission and those taken intraoperatively were calculated. Postoperative pain was measured at 6, 12 and 24 hours using a visual analogue scale. Need for additional analgesia over and above the 12 hourly diclofenac and incidence of shoulder tip pain was also noted.

Statistical analysis was carried out using the chi square and independent student t tests. A p value <0.05 was taken as statistically significant.

Results

Of the 30 patients taken up for laparoscopic cholecystectomy with standard pressure pneumoperitoneum at 14 mm Hg, 2 patients had to be converted to open cholecystectomy which was interpreted as failure of the technique leaving a sample size of 28. Of the 30 patients planned for laparoscopic cholecystectomy with low pressure pneumoperitoneum at 10 mm Hg, 3 patients had to be converted to standard pressure pneumoperitoneum which was taken as failure of the technique leaving a sample size of 27. This difference in failure rate was not statistically significant (p =1.00)

Laparoscopic cholecystectomy with standard pressure pneumoperitoneum took an average of 46.4 ± 6.9 minutes with a minimum of 35 minutes and a maximum of 65 minutes. Laparoscopic cholecystectomy with low pressure pneumoperitoneum took an average of 49.1 ± 5.7 minutes with a minimum of 40 minutes and a maximum of 60 minutes. Low pressure laparoscopic cholecystectomy took on average three minutes more than standard pressure laparoscopic cholecystectomy but this difference was not statistically significant (p = 0.1). The operating surgeons had noted that there was little difference in the exposure at 10mm Hg as compared to that at 14 mm Hg.

Three (11.1%) of the 27 patients who underwent low pressure laparoscopic cholecystectomy and five (17.9%) of the 28 patients who underwent standard pressure laparoscopic cholecystectomy needed additional analgesia postoperatively. This difference was not statistically significant (p = 0.7).

One (3.7%) of the 27 patients who underwent low pressure laparoscopic cholecystectomy and two (7.1%) of the 28 patients who underwent standard pressure laparoscopic cholecystectomy had post operative pain referred to the tip of the right shoulder. This difference was not statistically significant (p = 1.0). The average pain score at 6 hours for patients who underwent low pressure laparoscopic cholecystectomy was 62.2 ± 11.7 with a minimum of 36 and a maximum of 82. The pain score at 6 hours for standard pressure laparoscopic cholecystectomy was 59.1 ± 18.0 with a minimum of 35 and a maximum of 100. This difference was not statistically significant (p = 0.4). The average pain score at 12 hours for patients who underwent low pressure laparoscopic cholecystectomy was 54.2 ± 8.5 with a minimum of 38 and a maximum of 69. The average pain score at 12 hours for patients who underwent standard pressure laparoscopic cholecystectomy was 62.2 ± 12.0 with a minimum of 35 and maximum of 100. This difference was statistically significant. The average pain score at 24 hours for patients who underwent standard pressure laparoscopic cholecystectomy was 5.2 ± .8 with a minimum of 3.5 and a maximum of 10. Average pain score at 24 hours for patients who underwent low pressure laparoscopic cholecystectomy was 4.60 ± .81 with a minimum of 3.6 and a maximum of 8.2. This difference was not statistically significant.

The average change in systolic BP in patients who underwent low pressure laparoscopic cholecystectomy was an increase of 0.96 + 6.27 mm Hg with a maximum rise of 13 mm Hg and a maximum fall of 10 mm Hg. The average change in systolic BP in patients who underwent standard pressure laparoscopic cholecystectomy was an increase of 0.8 + 8.9 mm Hg with a maximum rise of 18 mmHg and a maximum fall of 16mm Hg. This difference was not statistically significant.

Average change in diastolic blood pressure in patients who underwent low pressure laparoscopic cholecystectomy was increase of 1.8 ± 5.2 mm Hg with a maximum rise of 13 mm Hg and a maximum fall of 7 mm Hg. The average change in diastolic BP in patients who underwent standard pressure laparoscopic cholecystectomy was an increase of 2.8 ± 4.2 mm Hg with a maximum rise of 10 mm Hg and a maximum fall of 7 mm Hg. This difference was not statistically significant.

The average change in heart rate in patients who underwent low pressure laparoscopic cholecystectomy was a decrease of 0.5 ± 5.28 beats per minute. Average change in heart rate in patients who underwent standard pressure laparoscopic cholecystectomy was an increase of 1.5 ± 6.02 beats per minute. This difference was not statistically significant.

Discussion

The advent of laparoscopic cholecystectomy is a milestone achieved in both the treatment of gallstones and in the evolution of minimal access surgery.[1,2] The aim was to reduce the trauma during access and maintain appropriate exposure of the surgical field during surgery.[1,2] To achieve this surgeons have traditionally relied on creating a pneumoperitoneum of up to 14-15 mm Hg by insufflating carbon dioxide gas into the peritoneal cavity at the time of insertion of ports. This has the desired effect of raising the abdominal wall away from the viscera giving room to visualise the gall bladder and surrounding organs, allowing manipulation of instruments and also allowing the intestine to fall away from the sub-hepatic space when the patient is positioned properly.[2] However pneumoperitoneum with carbon dioxide gas at the pressures commonly used has been shown to be associated with unique and specific side effects.[3,4,5,6,7] To negate these specific problems, the concept of low pressure pneumoperitoneum with carbon dioxide has been introduced. Initial studies have indicated that the use of low pressure during pneumoperitoneum is associated with better intra-operative tolerance (including anaesthesia tolerance) and improved postoperative recovery with reduced intensity of the surgical pain.[8,9,10,11,12,13,14,15] Many centres have reported that laparoscopic cholecystectomy performed with low pressure pneumoperitoneum resulted in a better postoperative quality of life as compared to laparoscopic cholecystectomy performed with standard pressure pneumoperitoneum.[8,9,10,11] Incidence and intensity of postoperative pain were significantly lower in low pressure pneumoperitoneum groups with fewer requirements of analgesics in the postoperative period.[8,9,10,11,12,13,14,15]

Pain following pneumoperitoneum for laparoscopic cholecystectomy is related to a number of factors. Whilst tissue injury at port insertion sites and gall bladder bed are probably the most important contributing factors, other factors that have been proposed are peritoneal stretch, diaphragmatic stretch and chemical irritation of the peritoneum by carbon dioxide and attendant carbonic acid formation, and stimulation of the sympathetic nervous system by hypercarbia.[6,7] Some centres have reported that the incidence and intensity of postoperative shoulder tip pain was significantly less in the low pressure pneumoperitoneum group when compared to standard pressure pneumoperitoneum groups.[11,12,13,14,15] However our study shows low incidence of shoulder pain in both groups with no statistical difference. It also shows that higher demand for additional analgesia is not significnt in the first 24 hours after surgery for the standard pressure group. Although statistically not significant this finding matches that of other studies that show lower analgesic consumption in low pressure groups. It has been proposed that in comparison to standard pressure pneumoperitoneum, low pressure pneumoperitoneum results in lesser hemodynamic changes with regard to cardiac output, heart rates and blood pressure.[12,13,14] However, our study failed to show any statistically significant difference between the two groups with regard to blood pressure changes and heart rate changes. One reason may be that the actual difference of 4 mm Hg in the intraperitoneal pressures in our low pressure pneumoperitoneum and standard pressure pneumoperitoneum groups was not sufficient to influence the hemodynamic status. Also our low pressure pneumoperitoneum group had intraperitoneal pressure maintained at 10 mm Hg which is close to what some investigators describe as standard pressure in their own studies. The comparatively lower pressure of 10 mm Hg in our study might have been sufficiently high to produce the adverse effects of pneumoperitoneum to the same degree as standard pressure pneumoperitoneum at 14 mm Hg. In one study it was found that there was no statistical difference in change in blood pressure and heart rate in low pressure pneumoperitoneum (defined as 7 mm Hg) and standard pressure pneumoperitoneum (defined as 15 mm Hg) groups.[14] They also noted that cardiac output fell to the same level in both groups though it recovered earlier in the low pressure pneumoperitoneum group. In another study, both low pressure pneumoperitoneum and standard pressure pneumoperitoneum caused a decrease in heart rate and mean arterial BP but this was not statistically significant.[11] In our study none of the patients had any major intra-operative or postoperative complications. The postoperative course was by and large uneventful in all patients.

In conclusion, low pressure pneumoperitoneum does result in some benefit to the patient in the form of lower intensity of postoperative pain but the impact on intra-operative hemodynamics is not significant. This needs to be examined through a more complex set up and probably a larger sample size that includes a significant numbers of patients with cardiovascular comorbid conditions.

Refferences

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2. Chok KS, Yuen WK, Lau H, Fan ST. Prospective randomized trial on low pressure versus standard pressure pneumoperitoneum in out patient laparoscopic cholecystectomy. Surg Laparosc Endosc Percutan Tech. 2006;16:383–6.

3. Koc M, Ertan T, Tez M, Kocpinar MA, Kilic M, Gocmen E,et al. Randomized prospective comparison of postoperative pain in lowversus- high pressure pneumoperitoneum. ANZ J Surg. 2005;75:693–6.

4. Esmat ME, Elsebae MM, Nasr MM, Elsebaie SB. Combined low pressure pneumoperitoneum and intraperitoneal infusion of normal saline for reducing shoulder tip pain following laparoscopic cholecystectomy. World J Surg. 2006;30:1969–73.

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6. Joris J, Cigarini I, Legrand M, Jacquet N, De Groote D, Franchimont P, et al. Metabolic and respiratory changes after cholecystectomy performed via laparotomy or laparoscopy. Br J Anaesth. 1992;63:341–5.

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8. Barczyñski M, Herman RM.. A prospective randomized trial on comparison of low pressure and standard pressure pneumoperitoneum for laparoscopic cholecystectomy. Surg Endosc. 2003;17:533–8.

9. Davidas D, Birbs K, Vezakis A, Mcmohan MJ. Routine low pressure pneumoperitoneum during laparoscopic cholecystectomy. Surg Endosc. 1999:13:87–9.

10. Barczyñski M, Herman RM. The usefulness of low pressure pneumoperitoneum in laparoscopic surgery. Folia Med Cracow. 2002;43:43–50 (Abstract)

11. Vezakis A, Davides D, Gibson JS, Moore MR, Shah H, Larvin M,et al. Randomized comparison between laparoscopic cholecystectomy and gasless laparoscopic cholecystectomy. Surg Endosc. 1999;13:890–3.

12. Wallace DH, Serpell MG, Baxter JN, O’Dwyer PJ. Randomized trial of different insufflation pressures for laparoscopic cholecystectomy. Br J Surg. 1997;84:455–8

13. Perrakis E, Vezakis A, Velimexis G, Savanis G, Deverakis S, Antoniades J, et al. Randomized comparison between different insufflation pressure for laparoscopic cholecystectomy. Surg Laparo Endosc Percutan Tech. 2003;13:245–9.

14. Dexter SP, Vucevic M, Gibson J, McMahon MJ. Hemodynamic consequences of high and low pressure capnoperitoneum during laparoscopic cholecystectomy. Surg Endosc. 1999;13:376–81

15. Sarli L, Costi R, Sansebastiano G, Trivelli M, Roncoroni L. Prospective randomized trial of low pressure pneumoperitoneum for the reduction of shoulder tip pain following laparoscopy. Br J Surg. 2000;87:1161–5.

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