Key result
Phenylephrine infusion in patients after low-risk cardiac surgery significantly increased cardiac output (median increase 0.25 L/min, p=0.012) and biventricular filling pressures.
Why the study?
Cardio-pulmonary bypass alters vasoreactivity and many patients exhibit chronotropic insufficiency after cardiac surgery, raising concern that phenylephrine may increase blood pressures at the expense of blood flow.
Does phenylephrine infusion alter haemodynamic parameters and cardiac output in patients after low-risk cardiac surgery?
Does phenylephrine infusion alter haemodynamic parameters and cardiac output in patients after low-risk cardiac surgery?
Effect estimate: median Δ 0.25 L/min
p-value: p=.012
In patients after low-risk cardiac surgery, phenylephrine infusion increases cardiac output and biventricular filling pressures without adversely affecting the pulmonary-to-systemic vascular resistance ratio.
Supports phenylephrine in stable post-cardiac surgery patients without ratio shift; leaves open effects in higher-risk or unstable cases.
BACKGROUND: Phenylephrine increases systemic- and pulmonary resistances and therefore may increase blood pressures at the expense of blood flow. Cardio-pulmonary bypass alters vasoreactivity and many patients exhibit chronotropic insufficiency after cardiac surgery. We aimed to describe the haemodynamic effects of phenylephrine infusion after cardiac surgery. METHODS: Patients in steady state after low-risk cardiac surgery received incremental infusion rates of phenylephrine up to 1.0 μg/kg/min with the aim of increasing systemic mean arterial blood pressure 20 mmHg. Invasive haemodynamic parameters, including pulmonary wedge pressures, were captured along with echocardiographic measures of biventricular function before, during phenylephrine infusion at target systemic blood pressure, and 20 min after phenylephrine discontinuation. RESULTS: Thirty patients were included. Phenylephrine increased mean arterial pressure increased from 78 (±9) mmHg to 98 (±10) mmHg with phenylephrine infusion. Also, pulmonary blood pressure as well as systemic- and pulmonary resistances increased. The ratio between systemic- and pulmonary artery resistances did not change statistically significantly (p = .59). Median cardiac output was 4.35 (interquartile range [IQR] 3.6-5.4) L/min at baseline and increased significantly with phenylephrine infusion (median Δcardiac output was 0.25 [IQR 0.1-0.6] L/min) (p = .012). Pulmonary artery wedge pressure increased from 10.2 (±3.0) mmHg to 11.9 (±3.4) mmHg (p < .001). This was accompanied by significant increases in central venous pressure. Phenylephrine infusion increased left ventricular end-diastolic volume from 105 (±46) mL to 119 (±44) mL (p < .001). All results of phenylephrine infusion were reversed with discontinuation. CONCLUSION: In haemodynamically stable patients after cardiac surgery, phenylephrine increased PVR and SVR, but did not change the PVR/SVR ratio. Phenylephrine increased biventricular filling pressures and left ventricular end-diastolic area. Consequently, CO increased as ejection fraction was maintained. These findings do not discourage the use of phenylephrine after low-risk cardiac surgery. REGISTRATION: clinicaltrial.gov (identifier NCT04419662).
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Juhl‐Olsen et al. (2023) studied low-risk cardiac surgery (n=30). Phenylephrine vs. baseline was evaluated on cardiac output (median Δ 0.25 L/min, p=.012). Phenylephrine infusion in patients after low-risk cardiac surgery significantly increased cardiac output (median increase 0.25 L/min, p=0.012) and biventricular filling pressures.
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