APPLICATION OF A NOVEL FIBEROPTIC BIOSENSOR IN-SITU TO INVESTIGATE THE METABOLIC EFFECT OF LACTATE INFUSION

Recently developed biosensor technology, which allows near real-time measurement in situ of gas tension (pCO(2) and pO(2)) and of pH, was applied to arterial blood, cerebrospinal fluid (CSF), and brain parenchyma during intravenous lactate infusion in monkeys. Comparison of simultaneous biosensor measurements and discrete arterial blood sampling for traditional blood gas analyses indicated a high level of correlation for pCO(2), pO(2), and pH. Arterial pO(2) and pH values were significantly higher and pCO(2) significantly lower than corresponding CSF and brain parenchyma values at baseline, during and following lactate infusion. There was a divergence between arterial and brain parenchyma pH and pO(2) measurements. Lactate infusion was associated with progressive arterial pH rises, consistent with the production of a metabolic alkalosis. Cerebrospinal fluid pCO(2) remained unchanged during and following lactate infusion. Brain parenchyma exhibited a complex pattern of response characterized by a trend for pO(2) and pH to decrease during lactate infusion, which reversed following completion of the infusion. These observations are suggestive of a transient hypoxia from decreased cerebral blood flow and/or reduced oxyhemoglobin dissociation during lactate infusion, but verification of these results is required.