Vasopressin in arterial hypotension in extremely low birth weight infants To the Editor: Rios and Kaiser demonstrated that vasopressin is as effective as dopamine in increasing arterial blood pressure in extremely low birth weight infants with early arterial hypotension.1 We would like to comment on their work. Based on 10 patients receiving vasopressin therapy, we believe that no firm statements about safety can be made. A much larger cohort is needed to evaluate the safety of vasopressin administration. Importantly, profound intestinal ischemia must be of concern in extremely low birth weight infants who are susceptible to the occurrence of necrotizing enterocolitis. The authors do not provide specific information with regard to initial dosing. This would have been helpful given that the recommended dose for continuous intravenous treatment with vasopressin varies substantially according to the manufacturer’s recommendation (0.0002-0.002 IU/kg/min).2 Moreover, a head-to-head comparison with noradrenalin as a potent vasopressor would have been more meaningful. The authors did not discriminate according to underlying disease (eg, hypovolemia, cardiogenic, or septic cause) nor did they measure endogenous vasopressin concentrations. Endogenous vasopressin levels are dependent on vasopressin synthesis and release as well as on its clearance and vasopressin-receptor sensitivity. In our experience vasopressin is most helpful in neonates with severe arterial hypotension secondary to sepsis.3 This is in line with previous reports demonstrating that vasopressin is most beneficial in patients with catecholamine-refractory septic shock with depletion of endogenous vasopressin and subsequent hypersensitivity to exogenous vasopressin. Conversely, endogenous vasopressin release is increased in cardiogenic shock, causing a decreased response to exogenous vasopressin.2,4

We suggest that future clinical studies assess endogenous vasopressin levels prior to starting exogenous vasopressin and monitor changes in circulating vasopressin levels over time in response to treatment. Endogenous vasopressin concentrations may turn out to be an important adjunct in detecting those infants who are at risk of developing severe forms of sepsis as low vasopressin/norepinephrine predicts impending septic shock.5 Moreover, the assessment of endogenous vasopressin levels may help predict the response pattern (success or failure) to exogenous administration in individual patients. Sascha Meyer, MD Eleni Z. Giannopoulou, MD Department of Pediatric Intensive Care Medicine and Neonatology University Hospital of the Saarland Homburg, Germany http://dx.doi.org/10.1016/j.jpeds.2015.05.024

References 1. Rios DR, Kaiser JR. Vasopressin versus dopamine for treatment of hypotension in extremely low birth weight infants: a randomized, blinded pilot study. J Pediatr 2015;166:850-5. 2. Meyer S, Gortner L, McGuire W, Baghai A, Gottschling S. Vasopressin in catecholamine-refractory shock in children. Anaesthesia 2008;63:228-34. 3. Meyer S, Gottschling S, Baghai A, Wurm D, Gortner L. Arginine-vasopressin in catecholamine-refractory septic versus non-septic shock in extremely low birth weight infants with acute renal injury. Crit Care 2006;10:R71-6. 4. Landry DW, Levin HR, Gallant EM, Ashton RC Jr, Seo S, D’Alessandro D, et al. Vasopressin deficiency contributes to the vasodilatation of septic shock. Circulation 1997;95:1122-5. 5. Lin IY, Ma HP, Lin AC, Lin CM, Wang TL. Low plasma vasopressin/ norepinephrine ratio predicts septic shock. Am J Emerg Med 2005;23: 718-24.

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