It is accepted treatment to give
vasopressin to adults in postcardiotomy
shock, but such use in children is controversial.
Cardiopulmonary bypass is presumed to attenuate the normal endogenous
vasopressin response to
shock. We hypothesized that levels of
vasopressin in children are altered by bypass, and that children having low endogenous levels perioperatively are more likely to develop
hypotension, or require vasopressors.
METHODS: Of 61 eligible patients, we enrolled 39 (63%). Their median age was 5 months. The mean level of
vasopressin prior to bypass was 18.6 picograms per millilitre, with an interquartile range from 2.6 to 11.4. Levels of
vasopressin peaked during bypass at 87.1, this being highly significant compared to baseline (p < 0.00005), remained high for 12 hours at a mean of 73.5, again significantly different from baseline (p = 0.002), were falling at 24 hours, with a mean of 28.1 (p = 0.04), and had returned to baseline by 48 hours, when the mean was 7.4 (p = 0.3). Age, gender, and the category for surgical risk had no influence on the levels of
vasopressin. There was no statistically significant relationship between the measured levels and
hypotension or the requirement for vasopressors, although a few persistently hypotensive patients had high levels subsequent to bypass. Higher levels correlated with higher levels of
sodium in the serum (r(s) = 0.37, p < 0.00005), higher osmolality (r(s) = 0.37, p < 0.00005), and positive fluid balance (r(s) = 0.23, p < 0.008). Preoperative use of inhibitors of
angiotensin converting enzyme, preoperative congestive
cardiac failure, and longer periods of bypass predicted higher levels during the first eight postoperative hours.
CONCLUSIONS: Children do not have deficient endogenous levels of
vasopressin following bypass, and lower levels are not associated with
hypotension. Any therapeutic efficacy of infusion of
vasopressin for post-cardiotomy
shock in children is likely due to reasons other than physiologic replacement.