The study of prevention of venous air embolism -Concerning with dural sinus pressure

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When dural sinus pressure was studied in the clinical cases and animal experiments in order to prevent venous air embolism,it was shown that,not only gravity,but also anteflexion and rotation of the neck,various manipulation during operation,durg-or bleeding-induced hypotension,etc.,were influenced for its development.On the other hand, it was considered that retroflexion of the neck,PEEP,neck and abdominal compression,extraneous fluid administration and drug induced hypertension are useful for its prevention. Among them,induced hypertension and continuous neck compression were expected for clinical application,and cerebral circulation(rCBF by H2 clearance method, vertebral blood flow by square wave electromagnetic flowmetry),cerebral function (cortical EEG)and function of blood brain barrier (BBB)due to these were further evaluated by animal experiments. (1)induced hypertension:The various changes at the increase of 40% of mean blood pressure at 45゜upright position were studied comparing with those of 80% rCBF and VBF increased to 8% and 7% by 40%-induced hypertension, while the autoregulation were broken down by 80% In cEEG, slow wave recognized by elevation of the operating table was considerably impproved by 40%,while rather aggravate by 80%. BBB dysruption was not noted by 40%-induced hypertension,while noted remarkably by 80%. (2)Neck compression:The cuff for the blood pressure mesurment was rolled so as to adhere to the skin,and its internal pressure was adjusted to 15mmHg,and 30mmHg was employed for control.rCBF decreased to 22,3% by 15mmHg of intracuff pressure,and more decreased to 45% by 30mmHg. The aggravating tendency of cerebral function and function of BBB was noted by neck compression.These results suggest that approx. 40%-induced hypertension contribute to the prevention of air embolism, and no problem for the clinical application,while neck compression has many problem for the clinical application.