Cerebral protection by lidocaine during cardiac operations

Cerebral arterial gas embolism by helium: an unusual case successfully treated with hyperbaric oxygen and lidocaine

A 27-year-old man inhaled helium from an unregulated pressurized cylinder and underwent cerebral arterial gas embolism (CAGE), leaving him blind and with radiologic evidence initially suggesting cortical infarction. There was complete recovery of vision and substantial regression of the radiologic changes after 4 hyperbaric oxygen treatments and a 54-hour lidocaine infusion, which began 6 hours after the accident. This is the second reported case of CAGE occurring by this mechanism and the first case of unequivocal CAGE in which lidocaine has been used as an adjunctive treatment with hyperbaric oxygen.

Venous air in the bypass circuit: a source of arterial line emboli exacerbated by vacuum-assisted drainage

BACKGROUND

Arterial emboli cause neurocognitive deficits in cardiac surgical patients. Carotid artery emboli, detected ultrasonically, have been observed after venous air entrainment into the cardiopulmonary bypass circuit. We investigated in vitro the extent to which venous air affected emboli detected in the arterial line downstream from a 40-microm filter.

METHODS

Using salvaged clinical cardiopulmonary bypass circuits, fixed volumes of air were introduced into the venous return line at unrestricted rates and at fixed rates using gravity venous drainage and vacuum-assisted venous drainage. Emboli counts were recorded distal to the arterial line filter using a 2-MHz pulsed-wave Doppler monitor. Emboli counts were similarly recorded after the introduction of carbon dioxide into the venous return line instead of air.

RESULTS

The number of emboli rose with increasing volumes of entrained venous air (p < 0.001), and there was an almost tenfold increase with vacuum-assisted venous drainage (p < 0.0001) compared with gravity venous drainage. Venous air was entrained at a significantly faster rate under vacuum-assisted venous drainage (p < 0.0001). When the entrainment rate of venous air was fixed, the difference in emboli numbers recorded for gravity and assisted venous drainage was not significant. There was a significant reduction in arterial line emboli when carbon dioxide rather than air was entrained under both vacuum-assisted and gravity drainage (p < 0.001).

CONCLUSIONS

Entrained venous air during cardiopulmonary bypass is a potential hazard, particularly during vacuum-assisted venous drainage. Every effort should be made to avoid venous air entrainment.

Treatment of diving emergencies

Recognition of condition attributable to the environmental changes experienced by divers will facilitate appropriate treatment. The diagnosis of these conditions rarely requires sophisticated imaging or electrophysiologic testing. Divers who have suspected DCI, in addition to general supportive measures, should be administered fluids and oxygen and transported to a recompression chamber. For diving-related conditions, on-line consultation is available from the Divers Alert Network, Durham, NC (919-684-8111).