HEMODYNAMIC-EFFECTS OF SODIUM-BICARBONATE IN CRITICALLY ILL NEONATES

Objective: To analyze the cardiovascular effects of sodium bicarbonate in neonates with metabolic acidosis. Design: Prospective, open, non-randomized, before-after intervention study with hemodynamic measurements performed before and 1, 5, 10, 20, and 30 min after bicarbonate administration. Setting: Neonatal intensive care unit, tertiary care center. Patients: Sequential sample of 16 paralysed and mechanically ventilated newborn infants with a metabolic acidosis (pH < 7.25 in premature and < 7.30 in term infants, base deficit > -8). Intervention: An 8.4% sodium bicarbonate solution diluted 1 : 1 with water (final osmolality of 1 000 mOsm/1) was administered in two equal portions at a rate of 0.5 mmol/min. The dose in mmol was calculated using the formula ''base deficit x body weight (kg) x 1/3 x 1/2''. Measurements and results: Sodium bicarbonate induced a significant but transient rise in pulsed Doppler cardiac output (CO) (+27.7%), aortic blood flow velocity (+15.3%), systolic blood pressure (BP) (+9.3%), (+14.6%), transcutaneous carbon dioxide pressure (PtcCO2) (+11.8%), and transcutaneous oxygen pressure (PtCO2) (+8%). In spite of the PaCO2 elevation, pH significantly improved (from a mean of 7.24 to 7.30), and the base deficit decreased (-39.3%). Calculated systemic vascular resistance (SVR) (-10.7%) and diastolic BP (-11.7%) decreased significantly, while PaO2 and heart rate (HR) did not change. Central venous pressure (CVP) (+6.5%) increased only slightly. By 30min after bicarbonate administration all hemodynamic parameters, with the exception of the diastolic BP, had returned to baseline. Conclusion: Sodium bicarbonate in neonates with metabolic acidosis induces an increase in contractility and a reduction in afterload.