Hypotension is a very common complication of spinal anesthesia for cesarean delivery, and can have unwanted side effects on both mother and fetus if not treated promptly. Phenylephrine has been the drug of choice to treat this spinal-induced hypotension. Although phenylephrine is safe to use for this indication, it has been associated with reflex bradycardia and a reduction in cardiac output. Norepinephrine is a potent vasopressor used to treat hypotension in the critical care setting. Recent studies have looked at norepinephrine's use in the obstetric setting, and have shown that it can be used safely and also has favourable hemodynamic properties when compared to phenylephrine, with less bradycardia and less depression of cardiac output. The investigators recently conducted a study to determine the ED90 of norepinephrine, and now plan to compare bolus doses of phenylephrine to norepinephrine for treating hypotension following spinal anesthesia for cesarean section. The investigators hypothesize that norepinephrine, when given as a bolus to prevent post spinal hypotension, will result in around 70% relative decrease in the rate of bradycardia when compared to phenylephrine in patients undergoing elective cesarean delivery under spinal anesthesia.
Norepinephrine is a potent vasopressor used to treat hypotension in the critical care setting. Recent studies have looked at norepinephrine's use in the obstetric setting, and have shown that it can be used safely and also has favourable hemodynamic properties when compared to phenylephrine, with less bradycardia and less depression of cardiac output. These studies have been limited to using norepinephrine as an infusion and there is limited data with it being used as a bolus to prevent hypotension. A recent study was undertaken at Mount Sinai hospital to determine the ED90 of norepinephrine to treat post spinal hypotension. Secondary outcome data from this trial showed that the incidence of bradycardia associated with this treatment is approximately 7.5%, several times less when compared to the reported 30% with phenylephrine. It would therefore be prudent at this stage to undertake a randomized trial comparing the hemodynamic profile of phenylephrine (our standard practice) and norepinephrine used as intermittent boluses to prevent hypotension and avoid decrease in heart rate during cesarean delivery.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
QUADRUPLE
Enrollment
112
Norepinephrine diluted in 5% dextrose solution to a concentration of 6mcg/mL
Phenylephrine diluted in 0.9% normal saline solution to a concentration of 100mcg/mL
Mount Sinai Hospital
Toronto, Ontario, Canada
Bradycardia: Heart rate less than 50 bpm
Heart rate less than 50 bpm, from induction of spinal anesthesia
Time frame: 30 minutes
Hypotension: Systolic blood pressure less than 80% of baseline
Systolic blood pressure below 80% of baseline, from induction of spinal anesthesia to delivery of the fetus.
Time frame: 30 minutes
Number of hypotensive episodes
The number of times the systolic blood pressure measures below 80% of baseline, from induction of spinal anesthesia to delivery of the fetus.
Time frame: 30 minutes
Hypertension: Systolic blood pressure at or above 120% of baseline
Systolic blood pressure at or above 120% of baseline, from induction of spinal anesthesia to delivery of the fetus.
Time frame: 30 minutes
Tachycardia: Heart rate greater than 30% of baseline
Heart rate greater than 30%, from induction of spinal anesthesia to delivery of the fetus.
Time frame: 30 minutes
Presence of nausea
Presence of nausea in patients from induction of spinal anesthesia to delivery of the fetus.
Time frame: 30 minutes
Number of episodes of nausea
The number of episodes of nausea experienced by patients from induction of spinal anesthesia to delivery of the fetus.
Time frame: 30 minutes
Presence of vomiting
Presence of vomiting in patients from induction of spinal anesthesia to delivery of the fetus.
Time frame: 30 minutes
Number of episodes of vomiting
The number of episodes of vomiting experienced by patients from induction of spinal anesthesia to delivery of the fetus.
Time frame: 30 minutes
Total dose of study drug given
Total dose of study drug given from induction of spinal anesthesia to delivery of the fetus.
Time frame: 30 minutes
Apgar scores
The Apgar scores of the infant at 1 and 5 minutes post delivery.
Time frame: 1 minute and 5 minutes
Umbilical artery pH
Umbilical artery pH
Time frame: 24 hours
Umbilical artery partial pressure of carbon dioxide
Umbilical artery partial pressure of carbon dioxide
Time frame: 24 hours
Umbilical artery partial pressure of oxygen
Umbilical artery partial pressure of oxygen
Time frame: 24 hours
Umbilical artery bicarbonate (mmol/L)
Umbilical artery bicarbonate
Time frame: 24 hours
Umbilical artery base excess (mmol/L)
Umbilical artery base excess
Time frame: 24 hours
Umbilical vein pH
Umbilical vein pH
Time frame: 24 hours
Umbilical vein partial pressure of carbon dioxide
Umbilical vein partial pressure of carbon dioxide
Time frame: 24 hours
Umbilical vein partial pressure of oxygen
Umbilical vein partial pressure of oxygen
Time frame: 24 hours
Umbilical vein bicarbonate (mmol/L)
Umbilical vein bicarbonate
Time frame: 24 hours
Umbilical vein base excess (mmol/L)
Umbilical vein base excess
Time frame: 24 hours
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