Plasma vasopressin concentrations prior to randomization clustered in two groups : one ( n = 5 ) with concentrations inappropriately low for the degree of hypotension ( 8.4 + / -2.1 pg/mL ) and a second ( n = 3 ) with moderately elevated levels ( 33.7 + / -1.6 pg/mL ) ; vasopressin increased mean arterial pressure in the low vasopressin group from 57 + / -4 to 85 + / -2 mm Hg ( P < .01 ) and in the high vasopressin group from 68 + / -8 to 86 + / -4 mm Hg .
