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 m easurement in situ of gas tension (pCO(2) and pO(2)) and of pH, was ap plied to arterial blood, cerebrospinal fluid (CSF), and brain parenchy ma during intravenous lactate infusion in monkeys. Comparison of simul taneous biosensor measurements and discrete arterial blood sampling fo r traditional blood gas analyses indicated a high level of correlation for pCO(2), pO(2), and pH. Arterial pO(2) and pH values were signific antly higher and pCO(2) significantly lower than corresponding CSF and brain parenchyma values at baseline, during and following lactate inf usion. There was a divergence between arterial and brain parenchyma pH and pO(2) measurements. Lactate infusion was associated with progress ive arterial pH rises, consistent with the production of a metabolic a lkalosis. Cerebrospinal fluid pCO(2) remained unchanged during and fol lowing lactate infusion. Brain parenchyma exhibited a complex pattern of response characterized by a trend for pO(2) and pH to decrease duri ng lactate infusion, which reversed following completion of the infusi on. These observations are suggestive of a transient hypoxia from decr eased cerebral blood flow and/or reduced oxyhemoglobin dissociation du ring lactate infusion, but verification of these results is required.