Background: In neonates, sinus tachycardia frequently occurs after cardiac surgery despite correction
of usual causes, such as stress, pain, fever, hypovolemia or anemia. Tachycardia-induced
additional myocardial oxygen consumption may even deteriorate function of postoperative
hearts. Beta-1-selective, short-acting β-blockers are useful to control the heart
rate but data on their efficacy and safety in newborn cardiac surgery with CPB are
lacking.
Method: As an institutional approach, we used a continuous esmolol infusion to optimize postoperative
heart rate as >140 bpm was deemed “out-of-proportion” and unnecessary to maintain
cardiac output. Patients with ECMO support were excluded from this retrospective analysis.
Between 2009 and 2020, a total of 69 newborns (female/male = 30/39) after cardiac
surgery with CPB were included in this study. Esmolol dosage was adopted to achieve
a heart between 120 and 140 bpm. Postoperative care followed a standardized protocol.
Biometric data and oximetry were recorded at start of esmolol and under “steady state”
conditions. Side effects, as well as outcome data, were analyzed.
Results: Median age was 8 (IQR: 5–14) days, median body weight 3.4 (IQR: 2.9–3.7) kg. Surgery
was performed for d-TGA in 32 (46%) and for repair of a hypoplastic aortic arch in
20 (29%) patients. Other diagnosis included truncus arteriosus (n = 6) and TAPVR (n = 5). Median cardiac arrest time was 98 (IQR: 37–120) minutes. Esmolol infusion was
started perioperatively in 29 (42%) patients and between 2 and 18 hours in 40 (58%)
children. Median initial esmolol dosage was 48 (IQR: 25–80) µg/kg/min and was increased
in 36 (52%), decreased in 12 (17%), and unchanged in 21 (31%) patients. Median heart
rate at postoperative admission on ICU was 159 (IQR: 149–169) bpm and decreased with
esmolol to 140 (IQR: 130–147; p < 0.001) bpm. Blood pressure and amplitude, as well as pressure-rate product decreased
significantly with esmolol therapy. While there was no difference in serum lactate
and central venous saturation between ICU admission and esmolol therapy, AVDO2 decreased
significantly with esmolol therapy (33 vs. 30%; p = 0.001). No organ failure or death occurred.
Conclusion: Currently, it is doctrine that newborns primarily depend on heart rate to generate
cardiac output. Questioning this, we showed that heart rate reduction did not deteriorate
hemodynamics but ergonomizes heart rate in a cohort after cardiac surgery. Whether
this approach leads to an improved outcome has to be demonstrated in further studies.
