INFLUENCE OF HYPERTONIC SALINE SOLUTION INFUSION ON DEFIBRILLATION EFFICACY

Hypertonic saline solution may enhance cardiac conduction via the fast inward sodium channel and alter transmembrane Ca++ conductance via th e sodium-calcium exchanger, Evidence suggests that both Ca++ conductan ce and myocardial conduction velocity may affect ventricular defibrill ation, Since hypertonic saline solution solutions (ie, sodium bicarbon ate) may be administered to patients who have conditions that often re quire ventricular defibrillation (ie, cardiac arrest or hypovolemic sh ock), we studied the effect of hypertonic saline solution on the defib rillation threshold (DFT) in 16 pentobarbital-anesthetized domestic fa rm swine (20 to 30 kg). Defibrillation was performed using two interfa ced epicardial electrode patches. DFTs were determined at baseline and during treatment phase, Pigs were randomly assigned to treatment cons isting of either hypertonic saline solution (6 mmol/kg load, 2.0 to 3. 0 mmol/kg infusion) to maintain serum sodium concentrations 10 to 15 m mol/L above baseline or control (D5W given in equal volume), DFT value s (joules) that predicted 50% success were modeled from a best-fit his togram, Hypertonic saline solution did not change DFT values from base line values (10.2+/-4.3 vs 10.8+/-7.0, respectively). Likewise, placeb o (D5W) did not change DFT values from baseline values (10.1+/-4.5 vs 11.3+/-4.3). During treatment phase, DFT values were 99+/-28% of basel ine values in the hypertonic saline solution group and 116+/-23% of ba seline values in the D5W groups (p=0.21). The administration of hypert onic saline solution also did not affect ventricular conduction veloci ty, right ventricular action potential duration, or right ventricular effective refractory period, These data indicate that hypertonic salin e solution does not appreciably affect defibrillation efficacy or elec trical treatment of ventricular fibrillation.