Hypertension and Bradycardia Associated with High‐Dose Dexamethasone in a Premature Infant with Borderline Hyponatraemia

Background: High‐dose dexamethasone in premature infants has been effective in improving short‐term respiratory status and reducing the time of ventilation. However, these high doses have commonly been associated with hypertension and left ventricular hypertrophy. Rare cases of bradycardia have also been reported. Case Report: We present a case of a premature female infant who developed blood pressure elevation and reduced heart rate after six doses of dexamethasone when her serum sodium concentration was 139 mmol/L. Blood pressure increased further and significant bradycardia occurred after a second course of dexamethasone (2 doses) when serum sodium concentration was 130 mmol/L. Her normal heart rate returned after ceasing dexamethasone. Subsequently she developed tachycardia. Discussion: Angiotensin II increases blood pressure and attenuates the baroreceptor response. High angiotensin II concentrations are known to be associated with low gestational age and low serum sodium. In combination these effects may lead to significant baroreceptor‐mediated bradycardia. A biphasic effect on the chronotropic response has also been seen in foetal lambs treated with dexamethasone. We postulate that lower doses of dexamethasone and maintaining a serum sodium concentration higher in the normal range may reduce the risk of hypertension and cardiac arrhythmia.