Administration of Milrinone Following Tetralogy of Fallot Repair Increases Postoperative Volume Administration Without Improving Cardiac Output.

Background: Phosphodiesterase inhibitors are known to relieve symptoms in the setting of heart failure, although their effects in restrictive ventricular physiology have been poorly characterized. We explored the association between the use of milrinone and volume administration during the first 72 hours following surgical repair of tetralogy of Fallot (TOF).

Methods: We reviewed all cases of primary surgical repair of TOF with pulmonary stenosis or atresia at Boston Children's Hospital between 2011 and 2020. To adjust for baseline differences between patients who did and did not receive milrinone, we matched patients with similar propensity scores in a 1:1 ratio (use of milrinone versus not). We then compared the need for volume administration during the first 72 hours postoperatively, vital signs, and measures of cardiac output between the matched cohorts. Additionally, in the group of patients receiving milrinone, linear regression modeling was used to explore the relationship between total dose of milrinone and total volume administration.

Results: Among 351 included patients, 134 received perioperative milrinone. A total of 212 patients (106 per group) were matched based on anatomic and surgical risks using a propensity score. After propensity matching, compared with nonmilrinone-treated patients, milrinone-treated patients were given postoperative volume more frequently (66% vs 52%; difference 14% [95% confidence interval, CI, 1%-27%]; P = .036). Milrinone-treated patients had a slower recovery of tachycardia during the first 12 hours (difference in slope 0.30 [95% CI, 0.14-0.47] beats per minute [BPM]/h; P < .001), and the intergroup difference peaked at 12 hours postoperatively (8 [95% CI, 5-12] BPM). Milrinone administration was not associated with improved cardiac output, including arteriovenous oxyhemoglobin saturation difference. In propensity-matched patients receiving milrinone, the total volume administered during the first 72 postoperative hours was significantly associated with the cumulative dose of postoperative milrinone ( r = 0.20; 95% CI, 0.01-0.38; P = .036). Based on the slope of the regression line, for every 1000 µg/kg of milrinone (equivalent to ~0.25 µg/kg/min for 72 hours) administered in the first 72 postoperative hours, an estimated 11.0 (95% CI, 0.6-21.4) mL/kg additional volume was administered.

Conclusions: The use of milrinone within the first 72 hours following TOF repair is associated with more frequent administration of volume, a positive association between a higher total dose of postoperative milrinone and the amount of postoperative volume administered, a higher heart rate, and a lower blood pressure, but is not associated with improved cardiac output.