Abstract P227: Cardiac Arrhythmias, Hemodynamic Instability and Death Following Low Volume 7.5% NaCl With 6% Dextran-70 or 10% Hetastarch Resuscitation in the vivo Rat Model of Hemorrhagic Shock
Objective: Small volumes of hypertonic solutions in combination with colloids are popular on the battlefield to resuscitate soldiers from hemorrhagic shock, and in some civilian trauma care units. The aim of the study was to examine the individual and combined effects of 7.5% NaCl, 6% dextran-70 or 10% hetastarch on ventricular arrhythmias, QRS amplitudes and hemodynamics following 60 min of hemorrhagic shock.
Methods: Male fed Sprague-Dawley rats (300–400g, n=32) were anaesthetized and randomly assigned to one of four groups:
control (bleed only),
7.5% NaCl/6% Dextran-70,
7.5% NaCl/10% hetastarch.
Hemorrhagic shock was induced by removal of up to 50% blood volume over 20 min until mean arterial pressure (MAP) decreased to 35–40 mmHg. Animals were left in shock at 32°C for 60 min. Resuscitation was commenced with small bolus’s (0.3 ml or ~3% of shed blood) injected into the femoral vein and Lead II ECG, MAP and heart rate (HR) were monitored.
Results: 0.3 ml of 7.5% saline at resuscitation led to a drop in MAP to about 10 mmHg lasting for 4 min, increased to around 60 mmHg and then slowly declined to 40 mmHg over the next hour. No arrhythmias were detected. Curiously, 0.3 ml of 7.5% NaCl/6% Dextran-70 led to a 1.5 fold increase in the QRS amplitude, ventricular arrhythmias and cardiac instability after 10 min, and an increase in HR of 20 to 40 bpm. The MAP initially fell then quickly returned to 35–38 mmHg for ~4 min, increased to above 55 mmHg and stabilized at around 50 mmHg for 60 min. 0.3 ml of 7.5% NaCl/10% hetastarch resulted in a 63% mortality (5 of the 8 rats died from ventricular fibrillation 5 min post-bolus). Arrhythmias were prominent in all animals that survived and MAP increased to around 70 mmHg and slowly decreased to 45 to 50 mmHg at 60 min recovery. No change in QRS amplitude occurred, and HR did not change significantly.
Conclusion: Small volumes of 7.5% NaCl/6% Dextran-70 in the rat model of hemorrhagic shock led to increased QRS amplitude and ventricular arrhythmias, and 7.5% NaCl/10% hetastarch led to a 63% mortality and severe arrhythmias. Though hetastarch has been reduced to 6% in commercially available Hextend (7.5% NaCl/6% hetastarch), caution may still have to be exercised when using bolus injections on the battlefield or trauma care units.