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.
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.
Letson
Hayley L
HL
Heart Research Laboratory, Department of Physiology and Pharmacology, School of Biomedical Sciences, James Cook University, Queensland, Australia.
Dobson
Geoffrey P
GP
D000704:Analysis of Variance; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000401:mortality* / Q000503:physiopathology*; D003911:Dextrans / Q000008:administration & dosage / Q000494:pharmacology*; D004195:Disease Models, Animal; D005440:Fluid Therapy / Q000009:adverse effects / Q000379:methods*; D006439:Hemodynamics; D006895:Hydroxyethyl Starch Derivatives / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage / Q000494:pharmacology*; D012771:Shock, Hemorrhagic / Q000401:mortality* / Q000503:physiopathology / Q000628:therapy*; D018709:Statistics, Nonparametric; D015996:Survival Rate
D003911:Dextrans; D006895:Hydroxyethyl Starch Derivatives; D012462:Saline Solution, Hypertonic