The response of plasma oxytocin to surgical stress.

Recent evidence suggests that oxytocin (OXT) and arginine vasopressin (AVP) are involved in the response to stress. We have examined the changes in peripheral plasma OXT during abdominal surgery in eight patients (six males, two female; ages 60-82 years) undergoing hemicolectomy and compared the results with those for AVP to the same stimulus. There was no significant change in systolic blood pressure, blood haematocrit or plasma sodium, osmolality or glucose. AVP rose significantly after premedication (from 1.8 +/- 0.3 pmol/l to 5.5 +/- 2.3 pmol/l; P less than 0.05) but the greatest increase (to 35.8 +/- 6.6 pmol/l) occurred after gut manipulation. Plasma OXT concentrations fell slightly with premedication (from 5.7 +/- 2.0 pmol/l to 3.3 +/- 0.9 pmol/l; P less than 0.05) but rose markedly (to a peak of 33.5 +/- 11.4 pmol/l) after gut manipulation. The data support the concept that OXT like AVP may play a role in the neuroendocrine response to surgery. The stimulus to OXT release and its function remain to be determined.