Propofol-sparing and hemodynamic effects of guaifenesin in sheep

Objective: To evaluate the propofol-sparing and hemodynamic effects of guaifenesin administered for co-induction of anesthesia in sheep. Study design: Prospective, blinded, two-way crossover experimental study. Animals: Thirteen healthy adult female sheep. Methods: Anesthesia was induced without premedication with intravenous (IV) guaifenesin 5% at 100 mg kg^–1 (GGE) or an equivalent volume of physiologic saline (SAL), followed by IV propofol at a controlled rate (1 mg kg^–1 min^–1). Heart rate (HR), respiratory rate and oscillometric noninvasive arterial blood pressure (NIBP) were recorded at baseline after co-induction administration, following endotracheal intubation and every 2 minutes thereafter for 10 minutes. Propofol doses required to achieve intubation after each co-induction treatment were compared by independent Student's t-test. Values of p < 0.05 were considered statistically significant. Results: The propofol dose required (mean ± standard deviation) to achieve intubation was significantly lower (p = 0.001) in the GGE treatment (3.40 ± 0.74 mg kg^–1) than in the SAL treatment (5.94 ± 1.09 mg kg^–1). HR was increased after anesthetic induction compared with baseline in both treatments. HR was generally lower in the GGE treatment than in the SAL treatment. NIBP did not vary between GGE and SAL treatments. Conclusions and clinical relevance: Guaifenesin, when administered as a co-induction agent with propofol in sheep, reduces propofol dose requirements and maintains hemodynamic variables within a clinically acceptable range.