Comparison of potency of ephedrine and mephentermine for prevention of post-spinal hypotension in caesarean section

Techniques for preventing hypotension during spinal anaesthesia for caesarean section

BACKGROUND

Maternal hypotension is the most frequent complication of spinal anaesthesia for caesarean section. It can be associated with nausea or vomiting and may pose serious risks to the mother (unconsciousness, pulmonary aspiration) and baby (hypoxia, acidosis, neurological injury).

OBJECTIVES

To assess the effects of prophylactic interventions for hypotension following spinal anaesthesia for caesarean section.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (9 August 2016) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials, including full texts and abstracts, comparing interventions to prevent hypotension with placebo or alternative treatment in women having spinal anaesthesia for caesarean section. We excluded studies if hypotension was not an outcome measure.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study quality and extracted data from eligible studies. We report 'Summary of findings' tables using GRADE.

MAIN RESULTS

We included 125 studies involving 9469 women. Interventions were to prevent maternal hypotension following spinal anaesthesia only, and we excluded any interventions considered active treatment. All the included studies reported the review's primary outcome. Across 49 comparisons, we identified three intervention groups: intravenous fluids, pharmacological interventions, and physical interventions. Authors reported no serious adverse effects with any of the interventions investigated. Most trials reported hypotension requiring intervention and Apgar score of less than 8 at five minutes as the only outcomes. None of the trials included in the comparisons we describe reported admission to neonatal intensive care unit. Crystalloid versus control (no fluids) Fewer women experienced hypotension in the crystalloid group compared with no fluids (average risk ratio (RR) 0.84, 95% confidence interval (CI) 0.72 to 0.98; 370 women; 5 studies; low-quality evidence). There was no clear difference between groups in numbers of women with nausea and vomiting (average RR 0.19, 95% CI 0.01 to 3.91; 1 study; 69 women; very low-quality evidence). No baby had an Apgar score of less than 8 at five minutes in either group (60 babies, low-quality evidence). Colloid versus crystalloid Fewer women experienced hypotension in the colloid group compared with the crystalloid group (average RR 0.69, 95% CI 0.58 to 0.81; 2009 women; 27 studies; very low-quality evidence). There were no clear differences between groups for maternal hypertension requiring intervention (average RR 0.64, 95% CI 0.09 to 4.46, 3 studies, 327 women; very low-quality evidence), maternal bradycardia requiring intervention (average RR 0.98, 95% CI 0.54 to 1.78, 5 studies, 413 women; very low-quality evidence), nausea and/or vomiting (average RR 0.89, 95% CI 0.66 to 1.19, 14 studies, 1058 women, I² = 29%; very low-quality evidence), neonatal acidosis (average RR 0.83, 95% CI 0.15 to 4.52, 6 studies, 678 babies; very low-quality evidence), or Apgar score of less than 8 at five minutes (average RR 0.24, 95% CI 0.03 to 2.05, 10 studies, 730 babies; very low-quality evidence). Ephedrine versus phenylephrine There were no clear differences between ephedrine and phenylephrine groups for preventing maternal hypotension (average RR 0.92, 95% CI 0.71 to 1.18; 401 women; 8 studies; very low-quality evidence) or hypertension (average RR 1.72, 95% CI 0.71 to 4.16, 2 studies, 118 women, low-quality evidence). Rates of bradycardia were lower in the ephedrine group (average RR 0.37, 95% CI 0.21 to 0.64, 5 studies, 304 women, low-quality evidence). There was no clear difference in the number of women with nausea and/or vomiting (average RR 0.76, 95% CI 0.39 to 1.49, 4 studies, 204 women, I² = 37%, very low-quality evidence), or babies with neonatal acidosis (average RR 0.89, 95% CI 0.07 to 12.00, 3 studies, 175 babies, low-quality evidence). No baby had an Apgar score of less than 8 at five minutes in either group (321 babies; low-quality evidence). Ondansetron versus control Ondansetron administration was more effective than control (placebo saline) for preventing hypotension requiring treatment (average RR 0.67, 95% CI 0.54 to 0.83; 740 women, 8 studies, low-quality evidence), bradycardia requiring treatment (average RR 0.49, 95% CI 0.28 to 0.87; 740 women, 8 studies, low-quality evidence), and nausea and/or vomiting (average RR 0.35, 95% CI 0.24 to 0.51; 653 women, 7 studies, low-quality evidence). There was no clear difference between the groups in rates of neonatal acidosis (average RR 0.48, 95% CI 0.05 to 5.09; 134 babies; 2 studies, low-quality evidence) or Apgar scores of less than 8 at five minutes (284 babies, low-quality evidence). Lower limb compression versus control Lower limb compression was more effective than control for preventing hypotension (average RR 0.61, 95% CI 0.47 to 0.78, 11 studies, 705 women, I² = 65%, very low-quality evidence). There was no clear difference between the groups in rates of bradycardia (RR 0.63, 95% CI 0.11 to 3.56, 1 study, 74 women, very low-quality evidence) or nausea and/or vomiting (average RR 0.42, 95% CI 0.14 to 1.27, 4 studies, 276 women, I² = 32%, very-low quality evidence). No baby had an Apgar score of less than 8 at five minutes in either group (130 babies, very low-quality evidence). Walking versus lying There was no clear difference between the groups for women with hypotension requiring treatment (RR 0.71, 95% CI 0.41 to 1.21, 1 study, 37 women, very low-quality evidence). Many included studies reported little to no information that would allow an assessment of their risk of bias, limiting our ability to draw meaningful conclusions. GRADE assessments of the quality of evidence ranged from very low to low. We downgraded evidence for limitations in study design, imprecision, and indirectness; most studies assessed only women scheduled for elective caesarean sections. External validity also needs consideration. Readers should question the use of colloids in this context given the serious potential side effects such as allergy and renal failure associated with their administration.

AUTHORS' CONCLUSIONS

While interventions such as crystalloids, colloids, ephedrine, phenylephrine, ondansetron, or lower leg compression can reduce the incidence of hypotension, none have been shown to eliminate the need to treat maternal hypotension in some women. We cannot draw any conclusions regarding rare adverse effects associated with use of the interventions (for example colloids) due to the relatively small numbers of women studied.

Techniques for preventing hypotension during spinal anaesthesia for caesarean section

BACKGROUND

Maternal hypotension is the most frequent complication of spinal anaesthesia for caesarean section. It can be associated with nausea or vomiting and may pose serious risks to the mother (unconsciousness, pulmonary aspiration) and baby (hypoxia, acidosis, neurological injury).

OBJECTIVES

To assess the effects of prophylactic interventions for hypotension following spinal anaesthesia for caesarean section.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (9 August 2016) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials, including full texts and abstracts, comparing interventions to prevent hypotension with placebo or alternative treatment in women having spinal anaesthesia for caesarean section. We excluded studies if hypotension was not an outcome measure.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study quality and extracted data from eligible studies. We report 'Summary of findings' tables using GRADE.

MAIN RESULTS

We included 126 studies involving 9565 participants. Interventions were to prevent maternal hypotension following spinal anaesthesia only, and we excluded any interventions considered active treatment. All the included studies reported the review's primary outcome. Across 49 comparisons, we identified three intervention groups: intravenous fluids, pharmacological interventions, and physical interventions. Authors reported no serious adverse effects with any of the interventions investigated. Most trials reported hypotension requiring intervention and Apgar score of less than 8 at five minutes as the only outcomes. None of the trials included in the comparisons we describe reported admission to neonatal intensive care unit. Crystalloid versus control (no fluids)Fewer women experienced hypotension in the crystalloid group compared with no fluids (average risk ratio (RR) 0.84, 95% confidence interval (CI) 0.72 to 0.98; 370 women; 5 studies; low-quality evidence). There was no clear difference between groups in numbers of women with nausea and vomiting (average RR 0.19, 95% CI 0.01 to 3.91; 1 study; 69 women; very low-quality evidence). No baby had an Apgar score of less than 8 at five minutes in either group (60 babies, low-quality evidence). Colloid versus crystalloidFewer women experienced hypotension in the colloid group compared with the crystalloid group (average RR 0.68, 95% CI 0.58 to 0.80; 2105 women; 28 studies; very low-quality evidence). There were no clear differences between groups for maternal hypertension requiring intervention (average RR 0.64, 95% CI 0.09 to 4.46, 3 studies, 327 women;very low-quality evidence), maternal bradycardia requiring intervention (average RR 0.99, 95% CI 0.55 to 1.79, 6 studies, 509 women; very low-quality evidence), nausea and/or vomiting (average RR 0.83, 95% CI 0.61 to 1.13, 15 studies, 1154 women, I² = 37%; very low-quality evidence), neonatal acidosis (average RR 0.83, 95% CI 0.15 to 4.52, 6 studies, 678 babies; very low-quality evidence), or Apgar score of less than 8 at five minutes (average RR 0.24, 95% CI 0.03 to 2.05, 11 studies, 826 babies; very low-quality evidence). Ephedrine versus phenylephrineThere were no clear differences between ephedrine and phenylephrine groups for preventing maternal hypotension (average RR 0.92, 95% CI 0.71 to 1.18; 401 women; 8 studies; very low-quality evidence) or hypertension (average RR 1.72, 95% CI 0.71 to 4.16, 2 studies, 118 women, low-quality evidence). Rates of bradycardia were lower in the ephedrine group (average RR 0.37, 95% CI 0.21 to 0.64, 5 studies, 304 women, low-quality evidence). There was no clear difference in the number of women with nausea and/or vomiting (average RR 0.76, 95% CI 0.39 to 1.49, 4 studies, 204 women, I² = 37%, very low-quality evidence), or babies with neonatal acidosis (average RR 0.89, 95% CI 0.07 to 12.00, 3 studies, 175 babies, low-quality evidence). No baby had an Apgar score of less than 8 at five minutes in either group (321 babies; low-quality evidence). Ondansetron versus controlOndansetron administration was more effective than control (placebo saline) for preventing hypotension requiring treatment (average RR 0.67, 95% CI 0.54 to 0.83; 740 women, 8 studies, low-quality evidence), bradycardia requiring treatment (average RR 0.49, 95% CI 0.28 to 0.87; 740 women, 8 studies, low-quality evidence), and nausea and/or vomiting (average RR 0.35, 95% CI 0.24 to 0.51; 653 women, 7 studies, low-quality evidence). There was no clear difference between the groups in rates of neonatal acidosis (average RR 0.48, 95% CI 0.05 to 5.09; 134 babies; 2 studies, low-quality evidence) or Apgar scores of less than 8 at five minutes (284 babies, low-quality evidence). Lower limb compression versus controlLower limb compression was more effective than control for preventing hypotension (average RR 0.61, 95% CI 0.47 to 0.78, 11 studies, 705 women, I² = 65%, very low-quality evidence). There was no clear difference between the groups in rates of bradycardia (RR 0.63, 95% CI 0.11 to 3.56, 1 study, 74 women, very low-quality evidence) or nausea and/or vomiting (average RR 0.42 , 95% CI 0.14 to 1.27, 4 studies, 276 women, I² = 32%, very-low quality evidence). No baby had an Apgar score of less than 8 at five minutes in either group (130 babies, very low-quality evidence). Walking versus lyingThere was no clear difference between the groups for women with hypotension requiring treatment (RR 0.71, 95% CI 0.41 to 1.21, 1 study, 37 women, very low-quality evidence).Many included studies reported little to no information that would allow an assessment of their risk of bias, limiting our ability to draw meaningful conclusions. GRADE assessments of the quality of evidence ranged from very low to low. We downgraded evidence for limitations in study design, imprecision, and indirectness; most studies assessed only women scheduled for elective caesarean sections.External validity also needs consideration. Readers should question the use of colloids in this context given the serious potential side effects such as allergy and renal failure associated with their administration.

AUTHORS' CONCLUSIONS

While interventions such as crystalloids, colloids, ephedrine, phenylephrine, ondansetron, or lower leg compression can reduce the incidence of hypotension, none have been shown to eliminate the need to treat maternal hypotension in some women. We cannot draw any conclusions regarding rare adverse effects associated with use of the interventions (for example colloids) due to the relatively small numbers of women studied.

Comparison of phenylephrine hydrochloride and mephentermine sulphate for prevention of post spinal hypotension

This study compared the effects of intravenous infusions of phenylephrine and mephentermine on the prevention of maternal hypotension and neonatal outcome in patients receiving spinal anaesthesia for caesarean section. Sixty ASA 1-2 patients with term, uncomplicated singleton pregnancy undergoing caesarean section under spinal anaesthesia were randomly divided into two groups of 30 each, to receive a prophylactic intravenous infusion of either phenylephrine or mephentermine. The incidence of hypotension was statistically similar in the two groups. However, in patients receiving phenylephrine, 7 (23%) developed bradycardia and 6 (20%), reactive hypertension. Neonatal outcome, in terms of Apgar scores and umbilical artery pH, was similar in both the groups. To conclude, phenylephrine and mephentermine infusions are equally effective in preventing post spinal hypotension in patients undergoing caesarean section and are associated with a similar neonatal outcome.

Vasopressor choice for hypotension in elective Cesarean section: ephedrine or phenylephrine?

INTRODUCTION

Hypotensive episodes are a common complication of spinal anesthesia during Cesarean section. The purpose of this study was to compare the effectiveness and the side effects of vasopressors, ephedrine and phenylephrine, administered for hypotension during elective Cesarean section under spinal anesthesia.

MATERIAL AND METHODS

The study consisted of 100 selected ASA I/II females scheduled for elective Cesarean section under spinal anesthesia. Each patient was randomly assigned to one of the two double-blind study groups. Group E received 1 ml ephedrine (5 mg/ml) with normal saline if hypotension was present (n=50). Group P received 1 ml phenylephrine (100 µg/ml) with normal saline if hypotension developed (n=50). Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) were compared within and between groups to basal levels at time increments of 0, 2, 4, 6, 8, 10, 15, 20, 25, 30, 45, and 60 min from start of surgery. Incidence of side effects and neonatal outcomes were studied between groups.

RESULTS

All patients required vasopressor therapy for hypotension. Administration of phenylephrine was associated with significant drop in HR. Changes in SBP, DBP, and MAP were similar in both groups for most observed times. The incidences of nausea/vomiting and tachycardia were significantly higher in the ephedrine group.

CONCLUSIONS

Phenylephrine and ephedrine are acceptable choices to combat maternal hypotension related to spinal anesthesia in elective Cesarean section. Complications of intra-operative nausea and vomiting, tachycardia and bradycardia should be considered when choosing a vasopressor, suggesting phenylephrine may be more appropriate when considering maternal well-being.

Potency of mephentermine for prevention of post-spinal hypotension

This study was designed to determine the minimum effective dose (ED50) of mephentermine for prevention of post-spinal hypotension in women undergoing elective caesarean section. Dixon's up-down method of sequential allocation was used to determine the patient's dose of vasopressor drug. In our previous study, mephentermine appeared to be much more potent than ephedrine, so the present study was conducted using a lower initial dose and smaller dose interval for this vasopressor. Following administration of spinal anaesthesia, a prophylactic infusion of mephentermine was started with 5 mg infused over a period of 30 minutes as the initial dose and a dose interval of 1 mg. The ED50 of mephentermine of 3.7 mg (95% confidence interval 2.4 to 5.7 mg) was much less than that of ephedrine, as calculated in our previous study using the same methodology. Using these values gives a potency ratio of ephedrine to mephentermine of 1:6.8 (95% confidence interval 6.0 to 7.5).

Techniques for preventing hypotension during spinal anaesthesia for caesarean section

BACKGROUND

Maternal hypotension, the most frequent complication of spinal anaesthesia for caesarean section, can be associated with severe nausea or vomiting which can pose serious risks to the mother (unconsciousness, pulmonary aspiration) and baby (hypoxia, acidosis and neurological injury).

OBJECTIVES

To assess the effects of prophylactic interventions for hypotension following spinal anaesthesia for caesarean section.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (November 2005).

SELECTION CRITERIA

Randomised controlled trials comparing interventions to prevent hypotension with placebo or alternative treatment in women having spinal anaesthesia for caesarean section.

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed eligibility and methodological quality of studies, and extracted data.

MAIN RESULTS

We included 75 trials (a total of 4624 women). Crystalloids were more effective than no fluids (relative risk (RR) 0.78, 95% confidence interval (CI) 0.60 to 1.00; one trial, 140 women, sequential analysis) and colloids were more effective than crystalloids (RR 0.68, 95% CI 0.52 to 0.89; 11 trials, 698 women) in preventing hypotension following spinal anaesthesia at caesarean section. No differences were detected for different doses, rates or methods of administering colloids or crystalloids. Ephedrine was significantly more effective than control (RR 0.51, 95% CI 0.33 to 0.78; seven trials, 470 women) or crystalloid (RR 0.70, 95% CI 0.50 to 0.96; four trials, 293 women) in preventing hypotension. No significant differences in hypotension were seen between ephedrine and phenylephrine (RR 0.95, 95% CI 0.37 to 2.44; three trials, 97 women) and phenylephrine was more effective than controls (RR 0.27, 95% CI 0.16 to 0.45; two trials, 110 women). High rates or doses of ephedrine may increase hypertension and tachycardia incidence. Lower limb compression was more effective than control (no leg compression) (RR 0.69, 95% CI 0.53 to 0.90; seven trials, 399 women) in preventing hypotension, although different methods of compression appeared to vary in their effectiveness. No other comparisons between different physical methods such as position were shown to be effective, but these trials were often small and thus underpowered to detect true effects should they exist.

AUTHORS' CONCLUSIONS

While interventions such as colloids, ephedrine, phenylephrine or lower leg compression can reduce the incidence of hypotension, none have been shown to eliminate the need to treat maternal hypotension during spinal anaesthesia for caesarean section. No conclusions can be drawn regarding rare adverse effects due to the relatively small numbers of women studied.