The effect of the prone maximal restraint position with and without weight force on cardiac output and other hemodynamic measures.
BACKGROUND
The prone maximal restraint (PMR) position has been used by law enforcement and emergency care personnel to restrain acutely combative or agitated individual. The position places the subject prone with wrists handcuffed behind the back and secured to the ankles. Prior work has indicated a reduction in inferior vena cava (IVC) diameter associated with this position when weight force is applied to the back. It is therefore possible that this position can negatively impact hemodynamic stability.


OBJECTIVE
We sought to measure the impact of PMR with and without weight force on measures of cardiac function including vital signs, oxygenation, stroke volume (SV), IVC diameter, cardiac output (CO) and cardiac index (CI).


METHODS
We conducted a randomized prospective cross-over experimental study of 25 healthy male volunteers (22-43 years of age) placed in 5 different body positions: supine (SU), prone (PR), prone maximal restraint with no weight force (PMR-0), prone maximal restraint with 50 lbs added to the subject's back (PMR-50), and prone maximal restraint with 100 lbs added to the subject's back (PMR-100) for 3 min. Heart rate (HR), blood pressure (BP), and oxygenation saturation (O2 sat) were monitored. In addition, echocardiography was performed to measure left ventricular outflow tract diameter (LVOTD), and SV, CO, and CI were then calculated. Data were analyzed using repeated measures ANOVA with pair-wise comparisons when appropriate to evaluate changes with each variable with respective positioning.


RESULTS
Despite a small decrease in SV between SU and PMR positions, there were no statistically significant differences in CO between the 5 different positions. There were also no differences in CI between positions other than a small decrease when comparing SU and PMR-50 only (mean difference -0.39 L/stroke, p = 0.005). There was no evidence of hemodynamic compromise in any of the PMR positions when evaluating HR, MAP or O2 sat.


CONCLUSIONS
PMR with and without weight force did not result in any changes in CO or other evidence of cardiovascular or hemodynamic compromise.
Department of Emergency Medicine, University of California, San Diego School of Medicine, San Diego, CA, USA.
Davut J
DJ
Savaser
Colleen
C
Campbell
Edward M
EM
Castillo
Gary M
GM
Vilke
Christian
C
Sloane
Tom
T
Neuman
Allan V
AV
Hansen
Virag
V
Shah
Theodore C
TC
Chan
D000328:Adult; D000704:Analysis of Variance; D001794:Blood Pressure; D002302:Cardiac Output / Q000502:physiology*; D018592:Cross-Over Studies; D004452:Echocardiography; D006339:Heart Rate; D006352:Heart Ventricles / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D010100:Oxygen / Q000097:blood; D011329:Prisoners; D016684:Prone Position / Q000502:physiology*; D011446:Prospective Studies; D012149:Restraint, Physical / Q000502:physiology*; D013318:Stroke Volume; D016683:Supine Position / Q000502:physiology; D016277:Ventricular Function, Left; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult
D010100:Oxygen
Cardiovascular function; Prone restraint; Sudden custody deaths