The Effect of Intravenously Administered 2-Chloroprocaine upon Uterine Artery Blood Flow Velocity in Gravid Guinea Pigs

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Abstract
The purpose of the present study was to assess the effect of intravenously administered 2-chloroprocaine upon uterine artery blood flow velocity (UBFV) in gravid guinea pigs. Ten experiments were performed in ten chronically instrumented animals between 0.7 and 0.9 of timed gestation. Each animal received four solutions of 2-chloroprocaine in random order: 1) 0.67 mg/kg; 2) 1.34 mg/kg; 3) 2.0 mg/kg; and 4) 1.34 mg/kg, with epinephrine 0.2 .mu.g/kg. Six animals received a fifth solution, 0.2 ml of saline control. 2-Chloroprocaine 1.34 mg/kg significantly increased maternal mean arterial pressure (MMAP) at 30 s after injection, and 2-chloroprocaine 2.0 mg/kg significantly increased MMAP through 2 min. 2-Chloroprocaine 1.34 mg/kg, with epinephrine 0.2 .mu.g/kg, also significantly increased MMAP through 2 min. No other solution significantly altered MMAP. 2-Chloroprocaine 2.0 mg/kg significantly decreased UBFV at 30 s after injection. 2-Chloroprocaine 1.34 mg/kg, with epinephrine 0.2 .mu.g/kg, significantly decreased UBFV through 2 min. No other solution significantly altered UBFV. The authors conclude that iv administration of 2-chloroprocaine with epinephrine significantly decreased UBFV in pregnant guinea pigs. In contrast, only the largest dose (i.e., 2.0 mg/kg) of 2-chloroprocaine alone transiently decreased UbFV. These data suggest that, in doses up to 1.34 mg/kg, 2-chloroprocaine alone may not decrease uterine blood flow when used as a marker for intravenous injection in obstetric patients.