Late administration of methylprednisolone does not enhance naloxone effect in hypovolemic shock

The late addition of methylprednisolone (MP) in our canine hypovolemic shock protocol was evaluated to determine whether any hemodynamic enhancement of the naloxone (NAL) effect might be present. Thirty-four dogs were bled to a mean arterial pressure (MAP) of 40-45 mm Hg and held there for 45 minutes. All animals were then treated (T = 0) with 0.9% NaCl (NS) or NAL. In two groups of animals, MP (30 mg/kg) was given as an IV bolus 30 minutes after initiating NS or NAL therapy. At 60 minutes, the infusions were stopped and the shed blood was returned. Animals treated with NAL with or without MP showed improvement in MAP, maximal left ventricular contractility (LVdP/dt max), and cardiac output (CO) compared to NS. We found little hemodynamic improvement with the addition of MP at T = 30 for either the NAL or NS. Plasma endorphinlike activity (PELA) values decreased during treatment in the groups receiving NAL. Survival was improved in all groups except those receiving NS, but survival was statistically better only in the group that received NAL.