Letson, Hayley L., and Dobson, Geoffrey P. (2010) 7.5% NaCl with adenosine, lidocaine and Mg2+(ALM) improves hypotensive resuscitation in the pressure-controlled rat model of severe hemorrhagic shock. Circulation, 122 (21). 5. A5-A5.

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Abstract

Much controversy exists over the fluid composition for hypotensive resuscitation. Previously we showed that a small volume of 7.5% NaCl/6% Dextran-70 (RescueFlow®) or 7.5% NaCl/hydroxyethyl starch (HES) led to cardiac instability and mortality (HES). Our aim was to examine the early resuscitative effects of 7.5% NaCl with adenosine, lidocaine and magnesium (AdenocaineTM) (ALM) on mortality and hemodynamics in the rat model of severe hemorrhagic shock.

Methods: Male fed Sprague-Dawley rats (300–450g, n=48) were anesthetized and randomly assigned to one of six groups: 1) Untreated 2) 7.5% saline, 3) 7.5% NaCl/Mg2+ (M), 4) 7.5% NaCl with adenosine/Mg2+(AM), 5) 7.5% NaCl with lidocaine/Mg2+ (LM), 6) 7.5% NaCl with ALM. Hemorrhagic shock was induced by phlebotomy until MAP was 35–40 mmHg and continued for 20 min (∼40% blood loss). Animals were left in shock for 60 min at 34°C. 0.3 ml (∼ 3.5% of shed blood) was injected as a 10 sec intravenous (IV) bolus. Lead II ECG, arterial blood pressures, MAP, heart rate and rate-pressure product (RPP) were monitored.

Results: Untreated rats experienced severe arrhythmias and 38% mortality. There were no deaths in any treatment group. 7.5% NaCl alone failed to maintain MAP after 5 min. Interestingly, the presence of Mg2+ had a “colloid-like” effect, and at 60 min the MAP was 48±2 mmHg vs. 36±5 mmHg for the 7.5% NaCl group (P<0.05). In addition, the Mg2+ group showed a 25% higher RPP than 7.5% NaCl alone. 7.5% NaCl with ALM led to further increases in MAP and was significantly higher than all other treatment groups (MAP was 60 mmHg at 60 min; P<0.05). This higher MAP was associated with a twofold increase in diastolic pressure compared with 7.5% NaCl alone or AM or LM groups. Both 7.5% NaCl with AM or LM were mildly bradycardic but not when combined as ALM. A few arrhythmias occurred in 7.5% NaCl group with or without Mg2+, but no arrhythmias occurred in the other treatment groups.

Conclusions: 7.5% NaCl with ALM led to a significantly higher MAP (P<0.05), higher diastolic rescue, higher RPP and a more electrically stable heart compared with other treatment groups. Ultra-small (<1ml/kg) intravenous bolus of 7.5% NaCl with ALM may have clinical applications in the early treatment of hemorrhagic shock on the battlefield or in out-of-hospital environments.

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