Correlation of end-tidal CO2 to cerebral perfusion during CPR.
OBJECTIVE
A number of studies have demonstrated a correlation between end-tidal carbon dioxide (ETCO2), cardiac output, and return of spontaneous circulation in experimental animals and in patients undergoing closed-chest CPR. Our study attempted to correlate ETCO2 to cerebral blood flow during cardiac arrest.


METHODS
Sixteen piglets were anesthetized, intubated, and instrumented for cerebral blood flow studies. An ultrasonic flow probe was placed on both internal carotid arteries for continuous flow measurements. The animal was fibrillated, and closed-chest CPR was begun. Continuous ETCO2 measurements were obtained and compared with simultaneous internal carotid, cardiac output, and cerebral blood flow measurements.


RESULTS
Correlations between ETCO2 and carotid and cerebral blood flow were determined using Pearson's method. The correlation between ETCO2 and total internal carotid flow was .58 (P = .01, Bonferroni's adjusted P = .30). Correlation between ETCO2 and cerebral blood flow was .64 (P = .01, Bonferroni's adjusted P = .09). A partial correlation coefficient for ETCO2 versus cardiac output was .70, whereas it was only .30 for ETCO2 versus cerebral blood flow.


CONCLUSIONS
Partial correlation coefficients suggest that ETCO2 correlates with cerebral blood flow when changes in cerebral blood flow parallel changes in cardiac output.
Lewis
L M
LM
Emergency Medicine Division, St Louis University Medical Center, Missouri.
Stothert
J
J
Standeven
J
J
Chandel
B
B
Kurtz
M
M
Fortney
J
J
D000818:Animals; D000829:Animals, Domestic; D001921:Brain / Q000098:blood supply; D002245:Carbon Dioxide / Q000378:metabolism; D002302:Cardiac Output / Q000502:physiology; D016887:Cardiopulmonary Resuscitation; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006323:Heart Arrest / Q000378:metabolism / Q000503:physiopathology* / Q000628:therapy; D013552:Swine
D002245:Carbon Dioxide