The relationship between post-burn increases in peripheral resistance and vasopressin

Using the dog anaesthetized with sodium pentobarbital receiving a 15 per cent total body surface full skin thickness flame burn as an experimental model, it was observed that administration of the vasopressin, V-1 receptor, blocking agent d(CH2)5Tyr(Me)AVP (SK&F100273) prior to burn could significantly reduce the increase in peripheral resistance which occurs in untreated burned animals. At 30 min post-burn peripheral resistance was 60.2 +/- 7.8 units in treated animals and 117.1 +/- 16.8 units in untreated animals. At 60 min post-burn these values were 71.3 +/- 7.2 units and 117.0 +/- 13.5 units, respectively. Changes in cardiac output were significantly less in treated than untreated experimental animals. The mean arterial blood pressures were not significantly different. Plasma levels of vasopressin were measured by radio-immunoassay prior to burn and at 30-min intervals for 6 h following burn. At the time of taking blood samples for vasopressin levels, mean arterial blood pressure and cardiac output were measured and peripheral resistance was calculated. The results of this study showed that immediately post-burn vasopressin plasma levels increased from 6.2 +/- 2.2 pg/ml to 27.3 +/- 9.5 pg/ml and peripheral resistance increased from 62.3 +/- 6.3 units to 128.0 +/- 20.3 units. During the remaining 6 h of the experimental study both vasopressin plasma levels and peripheral resistance remained elevated. These results show that following thermal injury there is a significant release of vasopressin and suggest that the increase in peripheral resistance observed could be due in part to the vasoconstrictor action of the released vasopressin.