Exaggerated vasopressin secretion and attenuated osmoregulated thirst in human survivors of hyperosmolar coma.
OBJECTIVE
To test the hypothesis that subnormal thirst sensation could contribute to the development of the hypernatraemia characteristic of hyperosmolar coma, we studied osmoregulation in survivors of hyperosmolar coma.


METHODS
Eight survivors of hyperosmolar coma, eight control subjects with Type II (non-insulin-dependent) diabetes mellitus and eight healthy control subjects underwent water deprivation during which measurements of thirst, plasma osmolality and vasopressin were taken.


RESULTS
Water deprivation caused greater peak plasma osmolality in the hyperosmolar coma group (301.7 +/- 2.7 mmol/kg) than in Type II diabetic (294.3 +/- 3.2 mmol/kg, p < 0.01) or control group (296.9 +/- 3.0 mmol/kg, p < 0.01) and a greater increase in plasma vasopressin concentration (hyperosmolar coma, 5.8 +/- 1.3 pmol/l, Type II diabetes, 1.8 +/- 1.3 pmol/l, p < 0.001, control subjects, 2.2 +/- 1.8 pmol/l, p < 0.001). Thirst ratings were lower following water deprivation in the hyperosmolar coma group (3.5 +/- 0.8 cm) than in Type II diabetes (7.7 +/- 1.6 cm, p < 0.001) or control subjects (7.4 +/- 1.3 cm, p <0.001), and the hyperosmolar group patients drank less in 30 min following water deprivation (401 +/- 105 ml) than Type II diabetic (856 +/- 218 ml, p < 0.001) or control subjects (789 +/- 213 ml, p < 0.001).


CONCLUSIONS
Survivors of hyperosmolar coma have subnormal osmoregulated thirst and fluid intake, which might contribute to the hypernatraemic dehydration typical of the condition.
McKenna
K
K
Department of Diabetes, Beaumont Hospital, Dublin, Republic of Ireland.
Morris
A D
AD
Azam
H
H
Newton
R W
RW
Baylis
P H
PH
Thompson
C J
CJ
D000368:Aged; D000369:Aged, 80 and over; D001127:Arginine Vasopressin / Q000097:blood; D001769:Blood; D003681:Dehydration / Q000209:etiology; D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D005260:Female; D006801:Humans; D006944:Hyperglycemic Hyperosmolar Nonketotic Coma / Q000150:complications / Q000503:physiopathology*; D006955:Hypernatremia / Q000209:etiology; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D013894:Thirst; D014667:Vasopressins / Q000378:metabolism*; D014868:Water Deprivation; D014882:Water-Electrolyte Balance
D014667:Vasopressins; D001127:Arginine Vasopressin