Shock after blast wave injury is caused by a vagally mediated reflex.
OBJECTIVE
Bomb blast survivors occasionally suffer from profound shock and hypoxemia without signs of external injury. We hypothesize that a vagally mediated reflex such as the pulmonary defensive reflex is the cause of shock from blast wave injury. This study was a prospectively randomized, controlled animal study.


METHODS
By using a previously described model of blast wave injury, we randomized rats to one of four groups: control, blast-only, bilateral cervical vagotomy plus atropine 200 microg/kg i.p. only, and bilateral cervical vagotomy plus atropine 200 microg/kg i.p. before blast injury. Cardiopulmonary parameters were recorded for 90 minutes after the blast or until death.


RESULTS
Bradycardia, hypotension, and absence of compensatory peripheral vasoconstriction, typically seen in animals subjected to a blast pressure injury, were prevented by bilateral cervical vagotomy and intraperitoneal injection of atropine methyl-bromide. Hypoxia and lung injury were not statistically significant between the blasted groups, suggesting equivalent injury.


CONCLUSIONS
Our data implicate a vagally mediated reflex such as the pulmonary defensive reflex as the cause of shock seen immediately after a blast pressure wave injury.
Department of Surgery, University of Oklahoma Health Sciences Center, and Department of Veterans Affairs Medical Center, Oklahoma City 73126, USA.
R J
RJ
Irwin
M R
MR
Lerner
J F
JF
Bealer
P C
PC
Mantor
D J
DJ
Brackett
D W
DW
Tuggle
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001753:Blast Injuries / Q000150:complications* / Q000473:pathology; D006439:Hemodynamics; D008168:Lung / Q000294:innervation / Q000473:pathology; D008297:Male; D010276:Parasympatholytics / Q000494:pharmacology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex; D012774:Shock, Traumatic / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D014628:Vagotomy; D014630:Vagus Nerve / Q000503:physiopathology*
D010276:Parasympatholytics; D001285:Atropine