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Cardiovascular responses to neuromuscular blockade in the anemic ovine fetus
1Department of Reproductive Medicine, University of California San Diego, La Jolla, USA.
Currently little is known about the cardiovascular responses of the anemic fetus to neuromuscular blockade. We hypothesized that, despite marked anemia with potentially decreased cardiac reserve, the fetal responses to Pancuronium neuromuscular blockade would differ significantly when compared with neuromuscular blockade with Atracurium (a cardiovascular sparing agent). Ten fetal sheep (137 +/- 1 (SE) days gestation) were divided into three groups (21 experiments): Pancuronium (n = 7), Atracurium (n = 6), and Control (n = 8). Fetal anemia (Hct = 21.8 +/- 0.7%) was produced by serial hemorrhage over 3 days. Fetal arterial (FAP) and venous (FVP) pressures, heart rate (FHR), and arterial pH, pO2, and pCO2 were measured at -20, 0, 10, 20, 30, 60, and 90 minutes relative to neuromuscular blockade. Data were analyzed by three-way ANOVA for repeated measures. Pancuronium neuromuscular blockade increased FHR (15-20 bpm, P < .0001) and decreased FVP (-0.8 mm Hg, P < .0001). Atracurium had no effect on FHR, FAP, or FVP. Fetal pH (0.024, P < .0001) and pO2 (1-2 mm Hg, P = .0001) increased in both neuromuscular-blocked groups. Fetal pCO2 decreased in the Pancuronium-blocked animals (P = .02). We conclude that, in anemic fetuses, neuromuscular blockade with Atracurium produced minimal cardiovascular effects when compared to neuromuscular blockade with Pancuronium. Both agents produced small improvements in fetal pH and blood gases.
Currently little is known about the cardiovascular responses of the anemic fetus to neuromuscular blockade. We hypothesized that, despite marked anemia with potentially decreased cardiac reserve, the fetal responses to Pancuronium neuromuscular blockade would differ significantly when compared with neuromuscular blockade with Atracurium (a cardiovascular sparing agent). Ten fetal sheep (137 +/- 1 (SE) days gestation) were divided into three groups (21 experiments): Pancuronium (n = 7), Atracurium (n = 6), and Control (n = 8). Fetal anemia (Hct = 21.8 +/- 0.7%) was produced by serial hemorrhage over 3 days. Fetal arterial (FAP) and venous (FVP) pressures, heart rate (FHR), and arterial pH, pO2, and pCO2 were measured at -20, 0, 10, 20, 30, 60, and 90 minutes relative to neuromuscular blockade. Data were analyzed by three-way ANOVA for repeated measures. Pancuronium neuromuscular blockade increased FHR (15-20 bpm, P < .0001) and decreased FVP (-0.8 mm Hg, P < .0001). Atracurium had no effect on FHR, FAP, or FVP. Fetal pH (0.024, P < .0001) and pO2 (1-2 mm Hg, P = .0001) increased in both neuromuscular-blocked groups. Fetal pCO2 decreased in the Pancuronium-blocked animals (P = .02). We conclude that, in anemic fetuses, neuromuscular blockade with Atracurium produced minimal cardiovascular effects when compared to neuromuscular blockade with Pancuronium. Both agents produced small improvements in fetal pH and blood gases.