A Randomized Double-Blinded Dose-dependent Study of Metaraminol for Preventing Spinal-Induced Hypotension in Caesarean Delivery

Effects of metaraminol and norepinephrine on hemodynamics and kidney function in a miniature pig model of septic shock

Objective

To compare the effects of metaraminol and norepinephrine on hemodynamics and kidney injury in the treatment of septic shock, and calculate the conversion dose ratio between the two vasopressors.

Methods

This randomized controlled study was performed on 15 Guizhou miniature pigs. Septic shock was induced by fecal peritonitis in 10 animals, and 5 were used as a sham-operated group (shams). Fluid resuscitation and vasopressors were initiated 30 min after the onset of septic shock. The septic shock pigs were randomly assigned to receive one of the two drugs to restore and maintain mean arterial pressure (MAP) ≥ 65 mmHg for 3 h. Hemodynamics and heart rate were continuously monitored.

Results

There was no significant difference in MAP, heart rate, cardiac output (CO) and central venous pressure (CVP) between the two groups after treatment. No arrhythmias such as atrial fibrillation and ventricular fibrillation presented during continuous monitoring. After septic shock, the animals showed obvious kidney injury. In addition, compared with norepinephrine, the creatinine at 3 h was significantly lower with metaraminol. According to propensity score matching, the ratio of 6: 1 was considered appropriate for the dose equivalence calculation of metaraminol (μg·kg-1·min-1): norepinephrine (μg·kg-1·min-1).

Conclusion

Metaraminol has a similar pressor effect to norepinephrine in septic shock; it does not increase heart rate and aggravate kidney injury after shock compared with norepinephrine. And our research may provide some laboratory evidence for the clinical usage of metaraminol.

Effect of Weight-Adjusted Phenylephrine, Norepinephrine, and Metaraminol for Elective Cesarean Delivery on Neonatal Acid–Base Status: A Randomized Controlled Trial

Purpose

Many previous trials have compared the effects of different vasoactive drugs on cesarean section patients, but their infusion rate is based on experience rather than high-quality evidence. It is difficult to judge whether the effect of vasoactive drug comes from the better choice or a more appropriate at rates of vasoactive drugs. The effect of vasoactive drugs at the rates of the 90% effective dose needs to be verified and compared.

Patients and Methods

Women undergoing elective caesarean delivery under combined spinal-epidural anaesthesia were randomized to receive phenylephrine or norepinephrine or metaraminol infusion at the rate that was assumed to be the 90% effective dose. Anesthetic management was standardized and included fluid loading with 10 mL/kg of Ringer. The primary outcome was the umbilical artery pH.

Results

78 patients were included. The umbilical artery pH was not significantly different among the three groups (phenylephrine group: 7.33 ± 0.03 vs norepinephrine group: 7.33 ± 0.04 vs metaraminol group: 7.33 ± 0.04, P = 0.99). There were no significant differences in the incidence of hypotension, hypertension, bradycardia, and nausea and vomiting among the three groups. The SBP of the phenylephrine group was significantly higher than that of the metaraminol group (adjustive P value = 0.005).

Conclusion

Phenylephrine (0.54 μg/kg/min) or metaraminol (2 μg/kg/min) or norepinephrine (0.08 μg/kg/min) administered to healthy patients with elective cesarean section after spinal anesthesia has no significant effect on the acid-base balance of the fetus.