title: 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.
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.
authors.affiliation: Heart Research Laboratory, Department of Physiology and Pharmacology, School of Biomedical Sciences, James Cook University, Queensland, Australia.
authors.forename: Hayley L
authors.initials: HL
authors.lastname: Letson
authors.forename: Geoffrey P
authors.initials: GP
authors.lastname: Dobson
mesh_terms: 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
chemical_list: D003911:Dextrans; D006895:Hydroxyethyl Starch Derivatives; D012462:Saline Solution, Hypertonic