Dose of prophylactic intravenous ephedrine during spinal anesthesia for cesarean section

STUDY OBJECTIVE: To compare the incidence of maternal hypotension associated with spinal anesthesia for cesarean section when 10-, 15-, or 20-mg prophylactic boluses of intravenous (IV) ephedrine are used. DESIGN: Prospective observational study. SETTING: Teaching hospital. Patients: 108 women admitted for elective cesarean section. INTERVENTIONS: Spinal anesthesia was performed using hyperbaric bupivacaine 10 mg, sufentanil 2 microg, and morphine 0.2 mg (volume 4 mL). Ephedrine (10, 15, or 20 mg) was administered 2 minutes after the intrathecal injection. Maternal blood pressure was checked every 2 minutes. Hypotension was promptly treated with 5-mg ephedrine boluses. MAIN RESULTS: Incidence of hypotension was significantly higher in women receiving a 10-mg prophylactic dose of ephedrine than in those receiving either a 15-mg or a 20-mg prophylactic dose of ephedrine [23/36 in the 10-mg ephedrine group vs. 13/36 and 10/36 in the 15-mg and 20-mg ephedrine groups, respectively (p< 0.05)]. CONCLUSION: In the conditions of this study, a single bolus of IV ephedrine with doses of either 15 or 20 mg decreased significantly the incidence of maternal hypotension as compared to a single 10-mg bolus of ephedrine.     

Comparison of metaraminol and ephedrine infusions for maintaining arterial pressure during spinal anesthesia for elective cesarean section

BACKGROUND: Although ephedrine is usually recommended as the first-line vasopressor in obstetrics, its superiority over other vasopressors has not been proven in humans. METHODS: In a double-blind study, the authors randomized women having elective cesarean section with spinal anesthesia to receive an intravenous infusion of ephedrine, starting at 5 mg/min (n = 25), or metaraminol, starting at 0.25 mg/min (n = 25), titrated to maintain systolic arterial pressure in the target range 90-100% of baseline. Umbilical cord gases, maternal hemodynamics, uterine artery puLsatility index, and Apgar scores were compared. RESULTS: Systolic arterial pressure was maintained more closely in the target range in the metaraminol group compared with the ephedrine group. In the metaraminol group, umbilical arterial pH was greater (median and interquartile range, 7.31 and 7.31-7.33 vs. 7.24 and 7.14-7.29; P < 0.0001), and umbilical venous pH was greater (7.36 and 7.35-7.38 vs. 7.33 and 7.26-7.34; P < 0.0001) compared with the ephedrine group. No patient in the metaraminol group had umbilical arterial pH less than 7.2, compared with nine patients (39%) in the ephedrine group (P = 0.0005). Apgar scores were similar between groups. Changes in uterine artery pulsatility index were similar between groups. CONCLUSIONS: When used by infusion to maintain arterial pressure during spinal anesthesia for cesarean section, metaraminol was associated with less neonatal acidosis and more closely controlled titration of arterial pressure compared with ephedrine.     

Different preloading protocols with constant ephedrine infusion in the prevention of hypotension for elective cesarean section under spinal anesthesia

Ninety ASA I or II parturients were randomly allocated to three groups: group 10RL, 15RL and 20RL to receive 10, 15 and 20 mL/kg of Ringer's lactate (RL) respectively within 15 minutes (min) before the spinal block. Spinal anesthesia was performed with hyperbaric bupivacaine 12 mg, morphine 100 microg and fentanyl 10 microg. The operating table was tilted to the left and an IV infusion of ephedrine of 3 mg/min was immediately started and continued until umbilical cord clamping in all groups. Hypotension was defined as a drop in mean arterial pressure (MAP) of more than 20% from baseline : this was treated with 10 mg ephedrine IV. The incidence of hypotension was 60%, 36.7% and 13.4% in group 10RL, 15RL and 20RL, respectively (p<0.05). Additional ephedrine dose was the lowest in group 20RL compared to the other groups (p<0.05). The total amount of ephedrine was 49.9 +/- 13.5, 46.4 +/- 13.4 and 38.4 +/- 8.5 mg in group 10RL, 15RL and 20RL, respectively (p <0.05). The incidence of nausea and vomiting in group 20RL was significantly less than in group 10RL (p = 0.02). It was concluded that preloading with 20 mL/kg of RL prior to spinal anesthesia followed by constant ephedrine infusion 3 mg/min after spinal block reduced the incidence of hypotension and of nausea and vomiting and decreased the total amount of ephedrine.     

A dose-response meta-analysis of prophylactic intravenous ephedrine for the prevention of hypotension during spinal anesthesia for elective cesarean delivery

We systematically reviewed available studies to determine the dose-response characteristics of prophylactic i.v. ephedrine for the prevention of hypotension during spinal anesthesia for cesarean delivery. We searched for randomized controlled trials (RCTs) or cohort studies-obtained through MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, and reference lists of published articles-in which two or more different doses of prophylactic i.v. ephedrine were used to prevent hypotension during spinal anesthesia for cesarean delivery. Four RCTs and one cohort study were found (total n = 390). There was a significant dose-response relationship in the RCTs pooled for hypotension (slope = -0.0128; 95% confidence interval [CI], -0.0213 to -0.0044), hypertension (slope = 0.0563; 95% CI, 0.0235 to 0.0892), and umbilical arterial pH (slope = -0.03; 95% CI, -0.05 to 0.00). The efficacy of ephedrine for preventing hypotension was small. At 14 mg, the number-needed-to-treat was only 7.6 (95% CI, 4.8-21.1), and this was the same as the number-needed-to-harm (7.6; 95% CI, 3.7-23.4). At larger doses, the likelihood of causing hypertension was actually more than that of preventing hypotension, and there was also a minor decrease in umbilical arterial pH. IMPLICATIONS: The authors performed a systematic review of dose-response studies of i.v. bolus ephedrine for preventing hypotension during spinal anesthesia for cesarean delivery. Prophylactic ephedrine cannot be recommended. The efficacy is poor at smaller doses, whereas at larger doses, the likelihood of causing hypertension is actually more than that of preventing hypotension.     

Sevoflurane anesthesia for elective cesarean section

Sevoflurane anesthesia was given to sixteen women who had been scheduled for elective cesarean section. The maternal systolic blood pressure significantly decreased during the anesthesia induction. Both the anesthesia induction and emergence were smooth and rapid. These findings were supported partially by the pharmacokinetic analysis of sevoflurane concentration in the maternal artery and expired gas mixture. Spontaneous uterine contractions were good in 12 patients, fair in two and poor in two. The measured blood loss was 752 ± 257ml including amniotic fluid. No blood transfusion was given to any patient. The median value of the Apgar score at one minute was seven (range three to nine). No neonate was intubated for resuscitation. No abnormal maternal laboratory data were found, including liver and kidney function tests and blood cell counts one week after the operation. No adverse effect of sevoflurane on the neonate was found one week after the delivery and three months after the discharge.(Asada A, Fujimori M, Tomoda S et al.: Sevoflurane Anesthesia for elective cesarean section. J Anesth 4: 66–72, 1990)     

Colloid vs. crystalloid preloading to prevent maternal hypotension during spinal anesthesia for elective cesarean section

Background:  Hypotension associated with spinal anesthesia for cesarean section is still a clinical problem. Colloid solutions seem preferable to crystalloid solutions for preloading. In most studies the overall rate of hypotension is reported. Few studies have, however, investigated the maternal and neonatal consequences of different levels of maternal hypotension.
Methods:  In this randomized, double-blinded study 110 patients presenting for elective cesarean section received either 1000 ml acetated Ringer's solution or 1000 ml 3% dextran 60 solution immediately before spinal anesthesia. The effect on overall hypotension, clinically significant hypotension (hypotension associated with maternal discomfort defined as nausea, retching/vomiting, dizziness or chest symptoms) and severe hypotension (systolic arterial pressure <80 mmHg) was studied.
Results:  Dextran reduced the incidence of overall hypotension from 85 to 66% ( P =  0.03), reduced the incidence of clinically significant hypotension from 60 to 30% ( P =  0.002) and reduced the incidence of severe hypotension from 23 to 3.6% ( P =  0.004) compared to Ringer's solution. There were neither differences in neonatal outcome between treatment groups nor between neonates grouped after severity of maternal hypotension.
Conclusion:  Clinically significant hypotension seems to be a more suitable outcome variable than overall hypotension. The protective effect of the colloid solution increased with increased severity of hypotension.     

Echocardiographic assessment of left ventricular filling during elective cesarean section under spinal anesthesia

Canadian Journal of Anesthesia/Journal canadien d'anesthésie -     

A sequential compression mechanical pump to prevent hypotension during elective cesarean section under spinal anesthesia

BackgroundSpinal anesthesia is a standard technique for cesarean section but can cause hypotension which may be related to venous pooling secondary to progesterone-induced decreases in vascular tone. This study investigated the use of a sequential compression mechanical pump with thigh-high sleeves with compression cycles timed to venous refilling. We hypothesized that this would recruit pooled venous blood from the lower limbs, maintain the central blood volume and thus decrease the incidence of hypotension.MethodsOne hundred parturients scheduled for elective cesarean section under spinal anesthesia were recruited and randomly assigned to use of either a mechanical pump (Group M) or control (Group C). A standardized protocol for co-hydration and anesthesia was followed. Hypotension, defined as a decrease in systolic blood pressure by >20% from baseline, was treated with 6-mg boluses of intravenous ephedrine. The incidence of hypotension was defined as the primary outcome. Median ephedrine requirement was taken as a measure of the severity of hypotension.ResultsHypotension occurred in 12 of 47 (25.5%) patients in Group M compared to 27 of 45 (60%) in Group C (P = 0.001). The median [range] ephedrine dose was greater in Group C (12 [0–24] mg) compared to Group M (0 [0–12] mg) (P < 0.001). There was no difference between groups in the time to onset of hypotension.ConclusionThe use of a sequential compression mechanical pump that detects venous refilling and cycles accordingly, reduced the incidence and severity of hypotension after spinal anesthesia for cesarean section.     

A dose-response study of prophylactic intravenous ephedrine for the prevention of hypotension during spinal anesthesia for cesarean delivery

We performed a randomized, double-blinded dose-finding study of IV ephedrine for prophylaxis for hypotension in 80 women who received an IV crystalloid preload and spinal anesthesia for elective cesarean delivery. One minute after the intrathecal injection, patients were given saline control or ephedrine 10, 20, or 30 mg IV for 30 s. Systolic arterial pressure (SAP) in the first 12 min after the spinal injection was greater in the 30-mg group compared with other groups (P < 0.05). Hypotension occurred in 7 patients (35%) in the 30-mg group compared with 19 (95%), 17 (85%), and 16 (80%) patients in the control and 10- and 20-mg groups, respectively (P < 0.0001). Maximum decrease in SAP was smaller in the 30-mg group (mean lowest SAP 87% of baseline, range 58%-105%) compared with other groups (P < 0.01). Reactive hypertension occurred in 9 patients (45%) in the 30-mg group (mean highest SAP 120% of baseline, range 104%-143%) compared with 2 (10%), 1 (5%), and 5 (25%) patients in the other groups (P = 0.009). Heart rate changes, total ephedrine requirement, incidence of nausea and vomiting, and neonatal outcome were similar among groups. The proportion of patients with umbilical arterial pH < 7.2 was 10.5%, 25%, 42%, and 22% in the control, 10-, 20-, and 30-mg groups, respectively (P = 0. 12). We conclude that the smallest effective dose of ephedrine to reduce the incidence of hypotension was 30 mg. However, this dose did not completely eliminate hypotension, nausea and vomiting, and fetal acidosis, and it caused reactive hypertension in some patients. Implications: We investigated different doses of IV ephedrine as prophylaxis for hypotension during spinal anesthesia for cesarean delivery and found that the smallest effective dose was 30 mg. However, this dose did not completely eliminate hypotension, caused reactive hypertension in some patients, and did not improve neonatal outcome.     

The effects of prophylactic bolus phenylephrine on hypotension during low-dose spinal anesthesia for cesarean section

BackgroundContinuously infused phenylephrine is frequently used to reduce the incidence of hypotension in women undergoing cesarean section under spinal anesthesia, but less is known about the prophylactic bolus method. We evaluated three prophylactic bolus doses of phenylephrine during low-dose spinal anesthesia for cesarean section.MethodsOne-hundred-and-eighty-four patients were randomized to receive 0.9% saline 2 mL (Control Group) or phenylephrine 1.0 μg/kg (PHE1 Group), 1.5 μg/kg (PHE1.5 Group), or 2.0 μg/kg (PHE2 Group) immediately after induction of combined spinal-epidural anesthesia. Maternal blood pressure and heart rate were recorded at 1-min intervals until delivery. Hypotension, defined as systolic blood pressure <80% of baseline, was treated with rescue doses of phenylephrine 100 μg at 1-min intervals until hypotension resolved. The incidence of nausea, vomiting, bradycardia, and hypertension, as well as Apgar scores and umbilical blood gases, were recorded.ResultsThe incidence of hypotension was 71.7% (33/46) in the Control Group, 68.9% (31/45) in the PHE1 Group, 37.0% (17/46) in the PHE1.5 Group and 45.7% (21/46) in the PHE2 Group (P=0.001). The total rescue dose of phenylephrine was greater in the Control Group than those in the PHE1.5 Group (P <0.05) and PHE2 Group (P <0.05). The incidence of hypertension increased as the dose of prophylactic phenylephrine increased (P <0.001) and was highest in the PHE2 group (37%). Other variables did not differ among the four groups.ConclusionsUnder the conditions of this study, prophylactic bolus injection of phenylephrine 1.5 μg/kg was a suitable alternative method for reducing the incidence of hypotension during low-dose spinal anesthesia for cesarean section.     

Accelerated idioventricular rhythm during spinal anesthesia for cesarean section

During cesarean section under regional anesthesia various anomalies of the electrocardiogram are reported such as bradycardia, supraventricular and ventricular premature beats, supraventricular paroxysmal tachicardia, S-T depression non-significant for myocardial ischemia and second degree atrioventricular block. We describe two cases of accelerated idioventricular rhythm in patients undergoing elective cesarean section with spinal anesthesia of which we have not found mention in the literature. This arrhythmia is not dangerous and does not usually evolve into ventricular fibrillation. During spinal anesthesia, however, it can exacerbate hypotension and, if misdiagnosed, a further administration of ephedrine can increase the duration of accelerated idioventricular rhythm. When necessary, for example in symptomatic hypotension or severe bradycardia, atropine is advised in order to inhibit vagal tone and increase the activity of the sino-atrial node, obtaining a pharmacological overdrive. This therapy is appropriate even if the frequency of the accelerated idioventricular rhythm is high.     

Prophylaxis for hypotension during cesarean section under spinal anesthesia: a randomized trial comparing hydroxyethyl starch 130/0.4 to ephedrine

Background and objectiveSpinal anesthesia is the technique of choice for scheduled or emergency cesarean section, but the prevalence of hypotension is high in this setting. Our aim was to compare the efficacy of a colloid (6% hydroxyethyl starch [HES] 130/0.4) to ephedrine for preventing hypotension.Patients and methodsPatients undergoing elective or emergency cesarean section (in non-life-threatening situations) were enrolled. Patients were randomized to 3 groups for prophylaxis. The first ephedrine group received 5 mg of ephedrine intravenously (EPHE-5); the second ephedrine group received 10 mg of the drug intravenously (EPHE-10); and the HES group received 500 mL of HES 130/0.4 in rapid infusion in 15 minutes. We recorded systolic and diastolic blood pressures and heart rate after 10 minutes in the operating room and 2, 5, 10, 15, 20, and 30 minutes after injection of the anesthetic. We also assessed the sensory and motor blockades on both sides 2, 5, 10, 15, 20, and 30 minutes after injection. Neonatal status was assessed by Apgar score and umbilical cord blood gas analysis.ResultsNinety-six patients, 33 in each ephedrine group and 30 in the HES group, were enrolled. Blood pressure decreased similarly in all 3 groups (36% EPHE-5 group, 36% EPHE-10 group and 40% HES group); no significant between-group differences were observed. Nor were there significant differences in the percentages of patients requiring bolus doses of ephedrine to treat hypotension (23% in the HES group vs 33% in the EPHE-5 group and 27% in the EPHE-10 group) or in the cumulative doses of ephedrine. Neonatal status was also similarly satisfactory in all 3 groups.ConclusionsHES 130/0.4 is as useful for hypotension prophylaxis as 5- mg or 10- mg intravenous doses of ephedrine. HES 130/0.4 might be a substitute for sympathomimetic agents if adverse effects are predicted or contraindications to the use of such drugs are present.     

Prophylactic phenylephrine infusion for preventing hypotension during spinal anesthesia for cesarean delivery

In a randomized, double-blinded, controlled trial, we investigated the prophylactic infusion of IV phenylephrine for the prevention of hypotension during spinal anesthesia for cesarean delivery. Immediately after intrathecal injection, phenylephrine was infused at 100 microg/min (n = 26) for 3 min. From that point until delivery, phenylephrine was infused at 100 microg/min whenever systolic arterial blood pressure (SAP), measured each minute, was less than baseline. A control group (n = 24) received IV bolus phenylephrine 100 microg after each measurement of SAP <80% of baseline. Phenylephrine infusion decreased the incidence (6 [23%] of 26 versus 21 [88%] of 24; P < 0.0001), frequency, and magnitude (median minimum SAP, 106 mm Hg; interquartile range, 95-111 mm Hg; versus median, 80 mm Hg; range, 73-93 mm Hg; P < 0.0001) of hypotension compared with control. Heart rate was significantly slower over time in the infusion group compared with the control group (P < 0.0001). Despite a large total dose of phenylephrine administered to the infusion group compared with the control group (median, 1260 microg; interquartile range, 1010-1640 microg; versus median, 450 microg; interquartile range, 300-750 microg; P < 0.0001), umbilical cord blood gases and Apgar scores were similar. One patient in each group had umbilical arterial pH <7.2. Prophylactic phenylephrine infusion is a simple, safe, and effective method of maintaining arterial blood pressure during spinal anesthesia for cesarean delivery. IMPLICATIONS: In patients receiving spinal anesthesia for elective cesarean delivery, a prophylactic infusion of phenylephrine 100 microg/min decreased the incidence, frequency, and magnitude of hypotension with equivalent neonatal outcome compared with a control group receiving IV bolus phenylephrine.     

Fetal and maternal effects of phenylephrine and ephedrine during spinal anesthesia for cesarean delivery

BACKGROUND: In our routine practice, we observed a reduced incidence of fetal acidosis (umbilical artery pH < 7.20) at cesarean delivery during spinal anesthesia when a combination of phenylephrine and ephedrine was used as first line vasopressor therapy, compared with using ephedrine alone. METHODS: The study was randomized and double blind. It compared phenylephrine 100 microg/ml (phenylephrine group), ephedrine 3 mg/ml (ephedrine group), and phenylephrine 50 microg/ml combined with ephedrine 1.5 mg/ml (combination group), given by infusion, to maintain maternal systolic arterial pressure at baseline during spinal anesthesia for elective cesarean delivery. RESULTS: Fetal acidosis was less frequent in the phenylephrine group (1 of 48) (P = 0.004) and less frequent in the combination group (1 of 47) (P = 0.005) than in the ephedrine group (10 of 48). The mean systolic arterial pressure was similar for the three groups: Phenylephrine group median 98% (IQR 94-103) of baseline, ephedrine group 100% (96-106) and combination group 101% (97-108) (P = 0.11). The mean heart rate was higher in the ephedrine group (median 107% [IQR 99-118] of baseline) than in the phenylephrine group (88% [82-98]) (P < 0.0001), or the combination group (96% [86-102]) (P < 0.0001). Nausea and vomiting were less frequent in the phenylephrine group (nausea 17%, vomiting 0%) than in the ephedrine group (nausea 66%, vomiting 36%) (P < 0.0001), or the combination group (nausea 55%, vomiting 18%) (P < 0.0001). CONCLUSIONS: Giving phenylephrine alone by infusion at cesarean delivery was associated with a lower incidence of fetal acidosis and maternal nausea and vomiting than giving ephedrine alone. There was no advantage to combining phenylephrine and ephedrine because it increased nausea and vomiting, and it did not further improve fetal blood gas values, compared with giving phenylephrine alone.