To the Editor: Over the past 2 yr, we have anesthetized 10 patients with Williams syndrome and concur with the recommendations by Burch et al.1 in their recent article. In addition, we have additional suggestions based on the successful resuscitation of two infants who suffered a cardiac arrest under anesthesia. In both infants, induction of anesthesia was with incremental doses of sevoflurane (2% and 3%), a remifentanil infusion and rocuronium. Cardiac arrest occurred within 5 min of induction and before intubation. The electrocardiograms demonstrated marked ST segment depression that was followed soon after by bradycardia. Neither patient had discernible systemic output (no palpable or Doppler evidence of pulses). Resuscitation with phenylephrine, epinephrine, and small fluid boluses occurred during the institution of cardiopulmonary resuscitation. Within 5 min from the start of resuscitation, the transthoracic echocardiography (TTE) demonstrated biventricular akinesis in the first and severe biventricular hypokinesis in the second patient. We used TTE to guide our therapy, allowing us to monitor wall motion abnormalities, guide fluid administration, and carefully titrate vasopressors without worsening tachycardia or the dynamic component of subarterial outflow tract obstruction. In addition, we avoided administration of epinephrine once the rhythm returned, but pulses were still absent (pulseless electrical activity) because the TTE demonstrated severely hypertrophied, underfilled ventricles. In this population, the inappropriate administration of epinephrine as per the pediatric advanced life support protocol for pulseless electrical activity could have compromised recovery. The second patient required urgent extracorporeal membrane oxygenation cannulation after sustaining another cardiac arrest several hours after arrival in the pediatric intensive care unit within 3 min after receiving a 1 μg/kg dose of fentanyl. Both the patients underwent successful surgical repair. These patients had severe bilateral outflow track obstruction with what Stamm et al.2 have termed “macaroni pulmonary arteries” (Fig. 1). It is noteworthy that the presence of an intracardiac shunt (patent foramen ovale and small restrictive ventricular septal defect) did not decrease the risk of arrest.Figure 1.: The PA hypoplasia.Despite an induction technique designed to minimize changes in coronary perfusion, our experience demonstrates that these patients continue to have a very high-anesthetic risk of cardiac arrest. We postulate that, during induction, a decrease in coronary perfusion pressure occurred secondary to vasodilation and in combination with relative hypovolemia, and severe biventricular hypertrophy precipitated ischemia leading to cardiac arrest. In the second patient, a cardiac arrest occurred within minutes after a small dose of fentanyl, highlighting the precarious hemodynamic balance of these children. We recommend preinduction hydration, ideally with an IV, but at minimum liberal PO fluids until 2 h preinduction and the early use of TTE to help treat hemodynamic abnormalities and guide therapy. Denise C. Joffe, MD Michael Richards, BM Michael Eisses, MD Brian Emerson, MD Jeremy Geiduschek, MD Department of Pediatric Anesthesiology University of Washington Seattle, Washington [email protected]