Endogenous
opiate peptides are released in early
hemorrhagic shock and may mediate
hypotension during
hypovolemia. We compared the effects of
naloxone alone versus incomplete volume
resuscitation on survival and splanchnic blood flow. Dogs were bled to a MAP of 35 mm Hg for 2 hours. In eight dogs, shed blood was returned; eight dogs received
naloxone (2 mg/kg bolus and 2 mg/kg/hr in 0.5 ml/kg/hr
normal saline) with no shed blood returned. Seven dogs received
normal saline alone without shed blood or
naloxone and served as untreated controls. Untreated dogs survived a mean of 18.6 minutes. All other dogs survived for 180 minutes.
Naloxone and shed blood were equally effective in improving hepatic and renal blood flow; gastric, intestinal, pancreatic, and splenic blood flow remained unchanged from
shock values in both groups. These data indicate that in the face of
hypovolemia naloxone improves survival and blood flow (ml/min/gm) to splanchnic organs despite no return of shed blood.