2026 Volume 79 Issue 8 Pages e199-e205
The use of protamine in open-heart surgery involving a cardiopulmonary bypass may induce hypotension after administration, although the mechanism for this remains unclear. This study investigated possible factors associated with protamine-induced hypotension (PIH) in dogs. In Study 1, the dose dependency of PIH was evaluated by comparing a group of dogs that received 4 mg/kg (n＝6) and a group that received 2 mg/kg (n＝6). In Study 2, the same 12 dogs received 1 mg/kg of protamine to assess potential allergic involvement. Mean arterial pressure, the number of PIH events, and the time to PIH onset were measured. Although no significant difference was detected (P＝0.221), PIH occurred more frequently in the higher-dose group (3/6 vs. 1/6), and most cases (77.8%) developed within 10 minutes of administration. No significant difference in anti-heparin activity was observed between the 4 mg/kg and 2 mg/kg groups (P＝0.552). These findings suggest a there was higher incidence of PIH in the higher-dose group, but the association between dose and PIH remains unclear. Allergic involvement could neither be confirmed nor excluded (P＝0.558).
