Protamine sulfate (PS), used to neutralize the effect of heparin, is often associated with systemic hypotension. The present study was aimed to investigate the protective effects of CaCl2 on adverse hemodynamic reaction to PS.

Forty-six dogs of three groups were studied. Animals were randomly allocated to receive either; saline 10 ml (controls, n = 26), CaCl2 5 mg/kg (n = 10) or 10 mg/kg (n = 10), added to PS 3 mg/kg given intravenously 5 min after heparin (300 IU/kg, iv). Mean aortic pressure (MAP), mean pulmonary arterial pressure (MPAP), left ventricular end-diastolic pressure (LVEDP), LVdP/dtmax, and -LVdP/dtmin, and pulmonary artery (cardiac output) and left circumflex blood flow (LCX flow) were recorded up to 15 min after PS.

PS caused significant reductions in MAP (-49%), cardiac index (CI, -66%), systemic vascular resistance index (SVRI, -22%), LVEDP (-67%), LVdP/dtmax (-36%), and LVdP/dtmin (-55%), but increased MPAP (39%) and PVRI (3.8 fold), which all increases and reductions peaked 1-3 min after PS injection in the control group. The addition of CaCl2 to PS significantly attenuated reductions of MAP (-35 and -26% in CaCl2 5 and 10 mg/kg treated dogs, respectively), CI (-34 and -37%), LVdP/dtmax (-14, -11% ), and -LVdP/dtmin (-34, -21%), and increases in PVRI (1.8 and 2.4 fold). However, both doses of CaCl2 increased MPAP (48, 82%), but not SVRI (-28, -21%) or LVEDP (-73, -75%). LCX flow increased similarly in all groups (75-137%). CaCl2 5 and 10 mg/kg iv increased plasma Ca2+ by 0.23 and 0.36 mM, respectively.

These results suggest that the simultaneous administration of CaCl2 attenuates the adverse hemodynamic effects of PS, used to reverse heparin anticoagulation in the dog.