Microdialysis in cisterna magna during cerebral air embolism in swine.

Arterial gas embolism may occur as a consequence of lung rupture, decompression sickness, following operative procedures or as accidental infusion of gas during various diagnostic procedures. It can lead to severe morbidity or even death. Microdialysis is a technique that has been extensively used for evaluating localized changes in the brain. The microdialysis probe is only capable of measuring changes in the immediate adjacent tissue. In arterial gas embolism the changes are multifocal. Thus a probe located in the cerebral cortex will not detect the total amount of damage. We used microdialysis in the cisterna magna of 9 anaesthetized pigs to study the diffuse injury following arterial gas embolism. After injection of 5.0 mL of air in the internal carotid artery, we found a significantly increased lactate-pyruvate ratio in the cerebrospinal fluid, lasting for 2 hours. This indicates anaerobic metabolism. Mean levels of glycerol were significantly increased, indicating membrane disruption. Glutamate levels were also elevated, although not significantly. The injection of air affected carotid flow. Flow in the carotid artery of the side of injection decreased significantly, but returned to baseline in 1 hour. Flow in the contralateral carotid was increased, but not significantly. We conclude that massive air embolism causes ischemia and reduced blood flow in the brain that can be detected in the cisterna magna.

[Prognostic significance of lactate concentration and indicators of acid-base balance in air embolism of cerebral vessels]. / Prognosticheskoe znachenie kontsentratsii laktata i pokazatelei kislotno-osnovnogo ravnovesiia spinomozgovoi zhidkosti pri vozdushnoi émbolii sosudov golovnogo mozga.

Acid-base balance and lactate concentration in the arterial blood and spinal liquor have been studied in 32 patients after air embolism of the brain vessels developed during cardiopulmonary bypass surgery. It has been shown that an increase of lactate concentration in the spinal liquor over 3.5 mmol/l after air embolism of the brain vessels is indicative of severe hypoxic brain damage, in which the prospect of stable consciousness recovery is doubtful. In lactate concentration 4.5-5 mmol/l and higher as well as in metabolic acidosis of liquor (sodium hydrocarbonate concentration less than 20 mmol/l) the intensive care procedures used were not effective. It is believed that these parameters are of prognostic value in the condition under study.