Treatment with a platelet-activating factor receptor antagonist improves hemodynamics and reduces epinephrine requirements, in a lethal rodent model of anaphylactic shock

BACKGROUND: In some cases, anaphylactic shock (AS) is still lethal, despite rapid use of epinephrine. High doses of epinephrine are associated with severe complications. Platelet-activating factor (PAF) is secreted in massive amounts during AS, and a high plasma level is correlated with increased AS severity.

OBJECTIVE: To assess the effect of ABT-491, a PAF-receptor antagonist and possible adjunct treatment, alone or in combination with epinephrine during AS.

METHODS: AS was induced by intravenous injection of 1 mg ovalbumin into ovalbumin-sensitized rats. Rats were then randomly assigned to 5 groups (n = 10 per group): SHAM (vehicle only), SHOCK (no treatment), ABT (ABT-491 1 mg/kg), EPI (epinephrine 5 µg as a bolus then 10 µg kg-1 min-1 by continuous infusion, followed by a reducing protocol) and EPI-ABT (both treatments).

RESULTS: Ovalbumin injection resulted in a severe decrease in mean arterial pressure, left ventricular inotropy (max dP/dt) and left ventricular shortening fraction (LVSF). All rats from the ABT group survived until the end of the experiment. ABT-491 prevented the LVSF decrease observed in the SHOCK group (at T15: ABT 50% ± 11% vs SHOCK 36% ± 9%, P = .01), significantly reduced the dose of epinephrine needed to treat anaphylactic shock (EPI-ABT 314 ± 67 µg/kg vs EPI 475 ± 69 µg/kg, P < .001) and reduced the time to restore basal MAP (ABT 23 ± 7 minutes vs EPI-ABT 13 ± 5 minutes, P < .01).

CONCLUSIONS AND CLINICAL RELEVANCE: AS was characterized by early cardiac dysfunction in our model. Treatment with ABT-491 allowed survival until the end of the experiment and reduced cardiac dysfunction. Use of the PAF-R antagonist had a synergistic effect with epinephrine and allowed a significant reduction in epinephrine consumption. Use of PAF-R antagonists during AS could reduce epinephrine-related complications and improve the treatment of epinephrine refractory cases.