BOLUS ADMINISTRATION OF BUFFERING AGENTS IMPROVE HEMODYNAMICS DURING HYPOXIC LACTIC ACIDOSIS IN NEWBORN SHEEP. 299

Recent studies report deleterious effects of sodium bicarbonate (BIC) in treatment of hypoxic lactic acidosis and have shown carbicarb (CAR), a CO2 consuming buffer, to be more beneficial. In a previous study we found no differences in hemodynamic effects of BIC, CAR or saline (SAL) when administered slowly over 30 min. to hypoxia-induced lactic acidotic lambs. During resuscitation, buffers are generally administered over a much shorter period. We hypothesized that administering buffers in a rapid injection, as in a resuscitative effort, would improve hemodynamics compared to use of SAL. Six newborn lambs underwent surgical instrumentation for catheter and transducer placement to allow measurements of blood pressure (BP), cardiac output (CO) and stroke volume (SV) and allowed 2 days for recovery. The animals were then intubated and mechanically ventilated. Hypoxia was induced using a mixture of 92% nitrogen and 8% oxygen until pH reached 7.0 and the lactic acid reached 13 mmoles/L. BIC, CAR, or equimolar SAL in equal volumes were administered over two minutes. Each animal underwent three experiments receiving each infusion in a randomized fashion. The animals were then placed in room air and allowed to recover. Hemodynamic measurements prior to the boluses were similar between the three groups. Hemodynamic responses pre and post-bolus are shown in thetable. In the SAL group, hemodynamics tended to continue to deteriorate whereas they improved with either BIC or CAR. We conclude, when administered in a rapid fashion, buffers improve hemodynamics during hypoxic lactic acidosis in newborn lambs. This gives support to the use of buffers in neonatal resuscitation.