The effect of apnea on brain compliance and intracranial pressure.
The effect of 2 minutes of apnea during endotracheal intubation on intracranial pressure (ICP), compliance, and cerebral blood volume (CBV) was studied in 19 adult dogs during normo-, hypo-, and hypercapnia. The compliance was measured from the cisterna magna in response to an intrathecal bolus injection (pressure-volume index). CBV was monitored by radiolabeled red blood cell activity. These measurements were made before and after 2 minutes of apnea. At normocapnia (pCO2 of 35-40 mm Hg), a period of apnea resulted in an increase in ICP from 9.6 to 26.3 mm Hg, a decrease in compliance from 0.051 to 0.020 ml/mm Hg (60%), and an increase in CBV of 0.26 ml (9.6%). When the animals were hypocapnic (pCO2 of 24-28 mm Hg), ICP increased from 12.8 to 19.6 mm Hg, compliance fell from 0.041 to 0.029 ml/mm Hg(29%), and CBV increased 0.07 ml (3.1%). Hypercapnia (pCO2 of 50-58 mm Hg) before apnea resulted in an increase in ICP from 21.5 to 47.1 mm Hg, a decrease in compliance from 0.032 to 0.015 ml/mm Hg (52%), and an increase in CBV of 0.41 ml (13.4%). These results suggest that hyperventilation (hypocapnia) before intubation limits the adverse decrease in brain compliance and increase in ICP by reducing changes in cerebral blood volume.
Williams
G
G
Neurosurgical Section, University of Oklahoma Health Sciences Center, Oklahoma City.
Roberts
P A
PA
Smith
S
S
Stevens
F A
FA
Tompkins
P
P
Arancibia
C
C
Pollay
M
M
D000818:Animals; D001049:Apnea / Q000503:physiopathology*; D001810:Blood Volume / Q000502:physiology; D001921:Brain / Q000503:physiopathology*; D002946:Cisterna Magna / Q000502:physiology; D003187:Compliance; D004285:Dogs; D007427:Intracranial Pressure / Q000502:physiology*; D013667:Technetium
D013667:Technetium