Issn Print: 1079-6061
Publication Date: 1998/02/01
DIRECT MONITORING OF BRAIN TISSUE OXYGENATION DURING HEMORRHAGIC SHOCK AND RESUSCITATION
G. Manley; C. Doyle; J. Gibson; D. Morabito; H. Hopf; L. Pitts; M. Knudson
Excerpt
Background: Hemorrhagic shock, hypoxia, and hypotension are significant causes of brain ischemia and death following major trauma. A goal of resuscitation is rapid restoration and maintenance of cerebral oxygenation, however, current systemic monitoring modalities may not reflect tissue oxygen debt in critical areas of the brain. Flexible, polargraphic Clark-type micro-probes have been developed that are capable of continuously monitoring tissue oxygenation. Purpose: The aim of this study was to investigate the feasibility and utility of directly monitoring cerebral oxygenation during hemorrhage and resuscitation. Methods: Licox[registered sign] CMP tissue oxygen probes, tissue temperature probes, and ICP monitors were inserted into the brains of anesthetized York shire swine (n=6). Standard physiologic measurements were collected. After stabilization, the animals were subjected to controlled hemorrhage through iliac arterial catheters to 50% of estimated blood volume. Rapid resuscitation was performed with the total amount of shed blood and crystalloids at a rate of 40ml/kg. Animals surviving the resuscitation phase of the protocol were observed for a minimum of 3 hours prior to euthanasia. Results: The mean baseline (Bl) brain tissue oxygen prior to hemorrhage was 39.2 +/- 5.7 mmHg. Brain oxygen rapidly declined to 20.4 +/- 6.0 mmHg in response to a graded hemorrhage of 50% estimated blood volume (50%H). Continued hemorrhage to a MAP of 20 mm or cardiac arrest (end hemorrhage, EH) resulted in a brain oxygen of 3.7 +/- 0.7 mmHg. Successfully resuscitated animals (n=3) achieved brain oxygen levels comparable to baseline measurements (35.83 +/- 3.5mmHg). Brain tissue oxygen never exceeded 10.8 mmHg in animals that expired. Conclusions: We have demonstrated that direct monitoring of brain tissue oxygenation is a highly responsive and reliable method for detecting cerebral ischemia during graded hemorrhage and resuscitation. Furthermore, this model of hemorrhagic shock, utilizing direct monitoring of cerebral oxygenation as an endpoint, appears to be ideal for evaluating a variety of cerebral resuscitation methods and responses to secondary brain insults.
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