Letson, Hayley L., and Dobson, Geoffrey P. (2011) Small volume 7.5% NaCl With 6% dextran-70 or 6% and 10% hetastarch are associated with arrhythmias and death after 60 minutes of severe hemorrhagic shock in the rat in vivo. Journal of Trauma, 70 (6). pp. 1444-1452.

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Abstract

Background: Hypertonic saline solutions in combination with colloids may have some applications in critically ill patients. Our aim was to examine the effects of small volumes (0.7–1 mL/kg intravenous) of 7.5% NaCl with different colloids on cardiac stability, hemodynamics, and mortality after severe hemorrhagic shock.

Methods: Male fed Sprague-Dawley rats (300–450 g, n = 48) were anesthetized and randomly assigned to one of six groups: (1) untreated (bleed only), (2) 7.5% NaCl, (3) 7.5% NaCl/6% dextran-70, (4) 7.5% NaCl/6% hetastarch (HES), (5) 6% HES alone, and (6) 7.5% NaCl/10% HES. Hemorrhagic shock was induced by phlebotomy until the mean arterial pressure (MAP) was 35 mm Hg to 40 mm Hg and continued for 20 minutes until ~40% blood loss. Animals were left in shock for 60 minutes at 34°C. 0.3 mL (<4% of shed blood) was injected as a 10 seconds bolus into the femoral vein. Lead II electrocardiogram, blood pressures, MAP, and heart rate were monitored.

Results: Untreated rats were highly arrhythmogenic with 38% mortality. 7.5% NaCl increased MAP from 39 mm Hg to 44 mm Hg with no severe arrhythmias or mortality. Dextran-70 increased MAP from 38 mm Hg to 49 mm Hg, transiently increased QRS amplitude (1.5 times) and was arrhythmogenic affecting 50% of animals with no deaths. Addition of 6% HES to hypertonic saline resulted in aberrant arrhythmias and 38% mortality. Six percent HES alone was proarrhythmic and led to 38% mortality. 7.5% NaCl with 10% HES resulted in 100% mortality (p < 0.05) from arrhythmias within 5 minutes of resuscitation.

Conclusions: Small volumes of 7.5% NaCl led to fewer arrhythmias and a 2.6 times survival benefit over untreated rats, and a partial resuscitation of MAP into the "permissive range." Dextran-70 or HES in 7.5% NaCl were proarrhythmic and HES led to increased mortality (p < 0.05). Because optimal heart function is critical for successful resuscitation, care should be exercised when using dextran-70 or 6 and 10% HES in small volume hypertonic saline solutions for early hypotensive resuscitation.

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