Chronic cocaine exposure alters carbon dioxide reactivity but does not affect cerebral blood flow autoregulation in anesthetized dogs.
BACKGROUND
Cocaine use is common in trauma victims. Consequently, understanding how cocaine alters normal physiology is important to providing appropriate medical care for these patients. This study was designed to identify how chronic cocaine exposure alters cerebrovascular physiology.


METHODS
Ten dogs (seven experimental, three control) were studied. Transcranial Doppler was used to measure CO2 reactivity and autoregulation of cerebral blood flow velocity (CBFvel). Measurements were made in anesthetized animals (0.6% or 1.8% isoflurane in oxygen and intravenous fentanyl) at baseline before cocaine exposure and then at weekly intervals for 4 weeks. During the 4-week study period, cocaine was administered intravenously four times per day.


RESULTS
Cocaine did not alter autoregulation of CBFvel in response to changes in mean arterial pressure. However, cocaine markedly impaired CO2 reactivity in three of the seven animals. In this subset of animals, increasing Paco2 decreased CBFvel, which is consistent with vasoconstriction rather than vasodilation.


CONCLUSIONS
Chronic cocaine exposure does not alter autoregulation of CBFvel but does alter CO2 reactivity in a subset of susceptible animals. If confirmed in humans, these findings have implications for traumatic brain injury patients who are chronic cocaine users. Specifically, the findings suggest that hyperventilation could exacerbate intracranial hypertension in a subset of these patients.
Bernards
Christopher M
CM
Department of Anesthesiology, University of Washington, Seattle, Washington 98195-6540, USA. chrisb@u.washington.edu
Artru
Alan
A
Visco
Elizabeth
E
Powers
Karen M
KM
Lam
Arthur
A
D000768:Anesthesia, General; D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology; D001784:Blood Gas Analysis; D001930:Brain Injuries / Q000097:blood / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002245:Carbon Dioxide / Q000097:blood / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000187:drug effects* / Q000502:physiology*; D003042:Cocaine / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology*; D004195:Disease Models, Animal; D004285:Dogs; D006706:Homeostasis / Q000187:drug effects* / Q000502:physiology*; D008297:Male; D017585:Ultrasonography, Doppler, Transcranial
D002245:Carbon Dioxide; D003042:Cocaine