Abstract
Following neurosurgical operations, diabetes insipidus or SIADH is often observed, the former characterized b) polyuria, hypernatremia and a low plasma level of arginine vasopressin (AVP) ; and the latter by hyponatremie and a high plasma level of AVP. In this study, plasma levels of AVP, human growth hormone (HGH), nicotine stimulated neurophysine (NSN), estrogen stimulated neurophysine (ESN), sodium and creatinine; plasma osmolarity and urine output were measured during neurosurgical operations. Plasma levels of AVP, NSN, ES? and HGH were assayed by radio-immunoassay. Plasma AVP and NSN rose to the highest level towards the end of each operation in parallel with the change of plasma HGH levels. Significant correlation was observed betweerr the plasma levels of AVP [y: (pg/ml)] and NSN [x: (ng/ml)]; y=2.lx+6.5 (r=0.64, P<0.01). It is thought that the elevation of plasma levels of AVP and NSN towards the end of the operation is mainly caused by surgical stress.
There were no significant correlations between the level of AVP in plasma and plasma osmolarity or between the former and change in blood pressure during the period of observation. It is suggested that these two factor: which are important in regulating the AVP level under physiological conditions may not be critical in the elevation of AVP by neurosurgical procedures.
From the course of AVP levels in plasma, it was considered that surgical stress after manipulation of the dura mater may be the main factor evoking the course of AVP release, resulting in retention of free water.
