Document Detail

Mechanism of loss of consciousness during vascular neck restraint.
MedLine Citation:
PMID:  22096121     Owner:  NLM     Status:  MEDLINE    
Vascular neck restraint (VNR) is a technique that police officers may employ to control combative individuals. As the mechanism of unconsciousness is not completely understood, we tested the hypothesis that VNR simply compresses the carotid arteries, thereby decreasing middle cerebral artery blood flow. Twenty-four healthy police officers (age 35 ± 4 yr) were studied. Heart rate (HR), arterial pressure, rate of change of pressure (dP/dt), and stroke volume (SV) were measured using infrared finger photoplethysmography. Bilateral mean middle cerebral artery flow velocity (MCAVmean) was measured by using transcranial Doppler ultrasound. Neck pressure was measured using flat, fluid-filled balloon transducers positioned over both carotid bifurcations. To detect ocular fixation, subjects were asked to focus on a pen that was moved from side to side. VNR was released 1-2 s after ocular fixation. Ocular fixation occurred in 16 subjects [time 9.5 ± 0.4 (SE) s]. Pressures over the right (R) and left (L) carotid arteries were 257 ± 22 and 146 ± 18 mmHg, respectively. VNR decreased MCAVmean (R 45 ± 3 to 8 ± 4 cm/s; L 53 ± 2 to 10 ± 3 cm/s) and SV (92 ± 4 to 75 ± 4 ml; P < 0.001). Mean arterial pressure (MAP), dP/dt, and HR did not change significantly. We conclude that the most important mechanism in loss of consciousness was decreased cerebral blood flow caused by carotid artery compression. The small decrease in CO (9.6 to 7.5 l/min) observed would not seem to be important as there was no change in MAP. In addition, with no significant change in HR, ventricular contractility, or MAP, the carotid sinus baroreceptor reflex appears to contribute little to the response to VNR.
Jamie R Mitchell; Dan E Roach; John V Tyberg; Israel Belenkie; Robert S Sheldon
Publication Detail:
Type:  Journal Article     Date:  2011-11-17
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  112     ISSN:  1522-1601     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2012 Feb 
Date Detail:
Created Date:  2012-02-03     Completed Date:  2012-08-23     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  396-402     Citation Subset:  IM    
Department of Cardiac Sciences, University of Calgary, Calgary, Alberta, Canada.
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MeSH Terms
Blood Flow Velocity / physiology
Blood Pressure / physiology
Carotid Arteries / physiology*
Carotid Sinus / physiology
Cerebrovascular Circulation / physiology*
Consciousness / physiology*
Fixation, Ocular / physiology
Heart Rate / physiology
Hemodynamics / physiology
Middle Cerebral Artery / physiology*
Neck / physiology
Pressoreceptors / physiology
Restraint, Physical / adverse effects,  methods*
Stroke Volume / physiology
Young Adult

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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