Platelet activation and serotonin release during colorectal surgery

In vitro studies show serotonin has a profound vasospastic effect on human mesenteric arteries. A similar response has peen shown in vivo in atherosclerotic primates. If platelet serotonin stores are released as a consequence of platelet activation during colorectal surgery, a similar effect may significantly alter the perfusion of newly formed anastomoses leading to ischaemia and anastomotic breakdown. Here we have studied the effects of surgery and anaesthesia on intraplatelet and plasma serotonin levels during the peri- and postoperative period following colorectal surgery. A series of six consecutive patients undergoing colorectal resection and anastomosis were selected. Peripheral venous blood samples, taken at specified times before and after surgery and prepared in a platelet stabilizing buffer solution, were analysed using a validated enzyme immunoassay technique. Intraplatelet serotonin levels were seen to fall post-operatively, whilst plasma serotonin levels were shown to rise, implying significant platelet activation and serotonin during the peri-operative period. This study demonstrates the increased bioavailability of serotonin during the peri-operative period in colorectal surgery patients. If the in vitro effects of this amine are mirrored in vivo, increased plasma levels of serotonin may have an important role in anastomotic dehiscence secondary to ischaemia.