Letters to the Editor

To the Editor:

Laparoscopic techniques are thought to provide tremendous benefits to patients, including reduced postoperative pain, superior cosmetic results, and reduced hospitalization. However, the most important aspect favoring the laparoscopic approach may turn out to be the preservation of the patient’s immune functions during and after surgery. ¹ Conventional surgery is known to impair the systemic immune response. Postoperative changes in the systemic immune response are proportional to the degree of surgical trauma, and subsequent immune suppression may be implicated in the development of septic complications and tumor metastasis formation. ²

Carbon dioxide (CO₂) is at present the most commonly used gas for abdominal insufflation, despite the serious drawback of causing respiratory acidosis due to transperitoneal absorption. West et al presented experimental data suggesting that these metabolic consequences of CO₂ can also benefit the patient. They proposed that cellular acidification induced by abdominal insufflation contributes to the blunting of the local inflammatory response during laparoscopic surgery, suggesting a partial scientific explanation for the observed scant inflammatory reaction to laparoscopic abdominal surgery. ³ This hypothesis has never been tested clinically. We therefore chose to compare CO₂ with helium insufflation. Helium is, in contrast to CO₂, metabolically inactive and is minimally absorbed across the peritoneum. ⁴

Sixteen patients scheduled for elective laparoscopic cholecystectomy were included and randomly assigned to undergo laparoscopy using either CO₂ or Helium (prototype insufflator specially adapted for helium insufflation, kindly made available by Karl Storz, Endoscopy-America, Culver City, CA) for abdominal insufflation. There were no preoperative signs of acute cholecystitis or stones in the common bile duct. The surgical technique, the American method for laparoscopic cholecystectomy performed through four cannulas, has been published elsewhere. ⁵ None of the patients had other diseases or conditions causing immunosuppression, nor did they receive immunosuppressive therapy during the perioperative period. The postoperative acute phase response was assessed by measuring C-reactive protein (CRP). Postoperative immune function was assessed by measuring monocyte HLA-DR expression. All results are expressed as mean ± standard error of the mean, HLA-DR expression as percentage of preoperative value.

Laparoscopy using helium insufflation resulted in significantly higher levels of CRP one day after surgery when compared to CO₂ pneumoperitoneum (18.0 ± 3.5 vs 29.1 ± 3.8, P < 0.05, Mann-Whitney U Test). Helium insufflation resulted in a significant reduction of monocyte HLA-DR expression at 1 day (58% ± 7) and 2 days (56% ± 16) after surgery when compared with preoperative levels (P < .05, Wilcoxon Signed Ranks Test). No significant changes between pre- and postoperative values could be observed after CO₂ insufflation.

These results confirm the experimental data of West et al and suggests that CO₂ used for abdominal insufflation decreases the activation of the inflammatory response and preserves parameters reflecting immunocompetence. We therefore postulate that cellular acidification of cells of the peritoneum induced by abdominal CO₂ insufflation contributes to blunting of the local inflammatory response, thereby preserving postoperative immune functions.

April 14, 1999

Colin Sietses MD
Miguel Cuesta MD, PhD
Robert H. J. Beelen PhD
B. Mary E. von Blomberg MD, PhD