Cerebral arterial air embolism: IV. Failure to recover with treatment, and secondary deterioration.

Cerebral arterial gas embolism was induced in 23 dogs that were then treated using one of six routines: no treatment; air at 2.8 bar (60 ft) for 2 min; air at 10 bar (300 ft) for 5 min; oxygen at 2.8 bar for 10 or 20 min; and air at 6 bar (165 ft) for 10 min. After decompression they were monitored for a total of 90 min after the time of embolization. The dogs then underwent an autoradiographic study of cerebral blood flow (CBF). A number of the air-treated dogs experienced a reduction in cortical evoked potential after decompression. Dogs in all groups, except the untreated group and the dog at 10 bar for 5 min, showed an improved CBF compared with their short-study counterparts. After compression treatment, CBF improved with time. Function in 7 dogs deteriorated to a variable small degree in the air-treated groups, while only 3 dogs in the group on oxygen for 10 min deteriorated by around 10%. The CBF of the oxygen groups was close to the undived control values, and their cerebrospinal fluid (CSF) pressures had returned to control levels. There was a dissociation between improving CBF and deteriorating function. It is evident that secondary deterioration is a random affair and therefore not easily studied. The results of the four-part series are summarized and discussed.