Naval Medical Research Unit San Antonio JBSA, Fort Sam Houston United States
Background Hemodynamic resuscitation methods are employed to attenuate tissue hypoxia and maintain circulatory homeostasis during hemorrhagic shock. There is increasing advocacy for permissive hypotension resuscitative methods to prevent exsanguination. While data supports this strategy to decrease hemorrhage, questions remain regarding its physiologic effect on the brain. Transcranial Doppler TCD ultrasonography is a non-invasive modality that can be used to monitor cerebral perfusion during resuscitation. Utilizing a non-human primate NHP model, our goal was to use TCD ultrasonography to characterize normal cerebral hemodynamics, allowing for future comparative analyses of cerebral hemodynamics in animal models of polytraumatic hemorrhagic shock. Materials and Methods Concurrent with an ongoing NHP protocol, the ophthalmic artery OA was insonated to establish baseline TCD values. A transorbital acoustic window was used, imaging was obtained with a 2.0 MHz transducer probe. OA was chosen as the transtemporal window for middle cerebral artery MCA resulted in suboptimal waveforms. Results The following TCD results represent the mean standard deviation, n 10. Pulsatility index 1.66-0.33, mean flow velocity MFV 21.64-5.48 cms, peak systolic velocity 45.46-5.48 cms, end diastolic velocity 9.84-3.91 cms and resistance index 0.79-0.08. Conclusions We discovered that Rhesus macaques are absent of an adequate transtemporal acoustic window for MCA insonation, and normal resting OA MFV pressure in NHPs mimics reported OA MFV in humans. This data is foundational for our future studies to evaluate cerebral hemodynamics during hemorrhage and the degrees of severity in hemorrhagic shock. Our future goals include the utilization of TCD technology to elucidate a safety threshold for permissive hypotensive resuscitation or aggressive fluid resuscitation as it pertains to cerebral blood flow.