Tuesday, January 02, 2007

Laparoscopy: Maintaining Delicate Integrity

Douglas E. Ott, MD, MBA, Professor of Biomedical and Environmental Engineering, Mercer University, Macon, GAThe peritoneal surface is one cell thick. It is delicate and must be treated with care and respect. We have been taught and admonished to keep peritoneal surfaces moist throughout surgical procedures because of the fragility of the tissue caused by drying. Tissue desiccation is one of the components and precursors of the inflammatory response and adhesion formation. While laparoscopy offers the patient and surgeon many advantages, it is the change and contrast from laparotomy operating room atmospheric conditions of air at 20oC and 50-60% relative humidity (RH) influenced by convection currents, under operating theater lights to one of forced gas flow through restrictive trocars at high terminal gas velocities with very dry gas that is the reason for the untoward effects of hypothermia, postoperative pain and adhesion formation. Government regulatory agencies of all countries mandate that the gas have 200 parts per million or less of water vapor (0.0002% RH). Delivery of the gas is through trocars with small openings. The result is a wind chill effect on tissue surfaces caused by rapid evaporation of the thin layer of peritoneal fluid. The currently used dry CO2 directed through a 2-millimeter diameter needle one centimeter from peritoneal tissue desiccates and kills peritoneum for a 2.5 square centimeter area within a 20-second exposure. After the peritoneal fluid layer is evaporated away as a result of the jet streaming effect of the dry gas, the peritoneal cell membrane is exposed. This causes vapor and osmotic pressure changes due to the high intracellular water content compared to the extracellular no water vapor state that results in rupture of the cell membrane. Rupture of the peritoneal cell membrane alters peritoneal integrity exposing the underlying ground substance releasing interleukins, cytokines and lymphokines, tumor necrosis factor and interleukin 1-6. These substances are not only part of the inflammatory response leading to adhesion formation but are also involved with the patients’ perception of postoperative pain. It is the spray drying of peritoneal surfaces during gas flow that significantly contributes to delayed cell death (apoptosis) and increased peritoneal fluid viscosity. As clinicians we see these occurrences during endoscopic procedures. To follow the precept of Primum Non Nocere (first do no harm) it is necessary, responsible and ethical to prevent injury to healthy tissue, reproduce normal equilibrium, promote safety and hold our patients’ comfort and the best outcome in the highest regard during and after endoscopic surgical procedures. This demands the use of an intra peritoneal environment that preserves the delicate balance of the peritoneum.
continued -->

No comments: