Prophylactic Phenylephrine Infusion Research Articles

Prophylactic phenylephrine infusion versus treatment with vasopressor bolus as needed during non-urgent cesarean delivery and neonatal acidemia: a retrospective cohort study (2016–2021)

IntroductionProphylactic vasopressor administration reduces spinal hypotension during cesarean delivery, however the effects of vasopressor administration on neonatal acidemia remain uncertain. We examined the occurrence of neonatal acidemia in the setting of non-urgent cesarean delivery and compared outcomes between cases receiving prophylactic phenylephrine infusion versus cases treated with boluses of phenylephrine. MethodsRetrospective cohort study with ethical approval, comparing non-urgent cesarean delivery cases performed under spinal anesthesia (2016 to 2021), receiving either prophylactic phenylephrine infusion or boluses as needed.Data were collected from anesthesia and labor ward electronic medical records. Records with missing pH or missing blood pressure data were excluded. The independent variable was prophylactic phenylephrine administration, a strategy implemented following international recommendations in 2018. The main outcome was neonatal acidemia, defined as umbilical artery pH < 7.1. The secondary outcome was maternal hypotension, defined as at least one systolic blood pressure (SBP) measurement below 100 mmHg or below 80% baseline. ResultsA total of 4392 patients were included in the final analysis; 1318 (30.0%) received prophylactic phenylephrine infusion. Neonatal acidemia (umbilical artery pH < 7.1) occurred in 28 (2.1%) cases receiving prophylactic phenylephrine versus 50 (1.6%) treated with boluses as needed (p = 0.188). Prophylactic phenylephrine infusion was not associated with occurrence of neonatal acidemia (aOR 0.83; 95% CI 0.52 to 1.33, p = 0.435). Prophylactic phenylephrine infusion was associated with a reduced spinal hypotension rate when defined as SBP < 100 mmHg (OR 0.47; 95% CI 0.37 to 0.57; p < 0.001), with similar results when hypotension was defined as a drop below 80% or 90% of baseline SBP. ConclusionIn this pragmatic study, prophylactic phenylephrine infusion was associated with a reduction in maternal spinal hypotension, but not reduced neonatal acidemia.

Norepinephrine versus phenylephrine affects prethrombotic response in patients undergoing cesarean section under spinal anesthesia: a randomized, double-blind, controlled study.

Venous thromboembolism (VTE) is one of the most common and serious complications of cesarean section in parturients. Norepinephrine (NE) has been shown to activate coagulation. The aim of this study was to compare the effect of a fixed-rate prophylactic norepinephrine infusion and a fixed-rate prophylactic phenylephrine（PHE） infusion under spinal anesthesia for caesarean section on the prethrombotic response. Sixty-six women undergoing cesarean section under spinal anesthesia were randomly assigned to the NE group or PHE group, starting simultaneously with the administration of the subarachnoid solution, a "study drug" solution containing either NE or PHE was pumped intravenously at a constant rate of 15 ml/h until the end of the operation. Plasma coagulation factor VIII activity (FVIII: C), Fibrinogen, and D-dimer levels were measured in blood samples obtained on admission to the operating theatre and at the end of the procedure. Compared with preoperative levels, there were no significant differences in postoperative fibrinogen and D-dimer levels in the NE group, except for a decrease in FVIII: C levels (P = 0.003). However, postoperative levels of FVIII: C (P = 0.009), fibrinogen (P = 0.035) and D-dimer (P = 0.025) were increased in the NE group compared with postoperative levels in the PHE group. NE does not affect the maternal prethrombotic response and can be safely used in cesarean sections. Compared with PHE infusion, NE infusion increased the level of coagulation molecules, suggesting that NE maybe more beneficial for women with high intraoperative bleeding requiring hemostasis.

Comparison of Prophylactic Phenylephrine Infusion and Rescue Bolus Administration for Maintaining Blood Pressure During Spinal Anaesthesia for Caesarean Delivery in Obese Parturient: A Randomised Control Trial.

Phenylephrine (PE) is one of the vasopressor used to treat hypotension during anaesthesia. The primary aim of this study was to compare the effect of prophylactic infusion and rescue bolus of PE on the haemodynamic changes during spinal anaesthesia (SA) for Caesarean section (CS) in obese parturients. A total of 74 obese parturients scheduled for elective CS under SA were randomised into two groups; Group A (n = 37) received prophylactic PE infusion starting at 50 μg min-1 and adjusted according to the given algorithm and Group B (n = 37) received 100 μg PE bolus to treat hypotension. The measured parameters were systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), the total requirement of PE and neonatal Apgar score. Six patients were excluded from the analysis due to missing data and only 68 were analysed. Group A showed significantly higher SBP, DBP and MAP than Group B (P < 0.05). The requirement of PE was higher in Group A than Group B [817.7 (265.7) μg versus 360.6 (156.0) μg; P = < 0.05]. Both groups had no difference in terms of the neonatal Apgar score. Prophylactic PE infusion provided better haemodynamic control than therapeutic boluses in obese parturients undergoing CS under SA.

Effect of intravenous palonosetron on hypotension induced by spinal anesthesia for cesarean section: A randomized controlled trial.

The aim of this study was to evaluate the impact of intravenous palonosetron compared to ondansetron on hypotension induced by spinal anesthesia in women undergoing cesarean section. Fifty-four women scheduled for elective cesarean section were, randomly allocated to ondansetron group (n = 27) or palonosetron group (n = 27). Ten minutes prior to the administration of spinal anesthesia, participants received an intravenous injection of either ondansetron or palonosetron. A prophylactic phenylephrine infusion was initiated immediately following the intrathecal administration of bupivacaine and fentanyl. The infusion rate was titrated to maintain adequate blood pressure until the time of fetal delivery. The primary outcome was total dose of phenylephrine administered. The secondary outcomes were nausea or vomiting, the need for rescue antiemetics, hypotension, bradycardia, and shivering. Complete response rate, defined as the absence of postoperative nausea and vomiting and no need for additional antiemetics, were assessed for up to 24 hours post-surgery. No significant differences were observed in the total dose of phenylephrine used between the ondansetron and palonosetron groups (387.5 μg [interquartile range, 291.3-507.8 μg versus 428.0 μg [interquartile range, 305.0-507.0 μg], P = 0.42). Complete response rates also showed no significant differences between the groups both within two hours post-spinal anesthesia (88.9% in the ondansetron group versus 100% in the palonosetron group; P = 0.24) and at 24 hours post-surgery (81.5% in the ondansetron group versus 88.8% in the palonosetron group; P = 0.7). In addition, there was no difference in other secondary outcomes. Prophylactic administration of palonosetron did not demonstrate a superior effect over ondansetron in mitigating hemodynamic changes or reducing phenylephrine requirements in patients undergoing spinal anesthesia with bupivacaine and fentanyl for cesarean section.

Hemodynamics following Prophylactic Phenylephrine Infusion in patients undergoing Cesarean Section under Spinal Anesthesia

Introduction: Phenylephrine is considered the vasopressor of choice in hypotension associated with obstetric spinal anesthesia. But the dose and mode of administration that is effective yet safe in mother as well as fetus remains controversial. We studied the hemodynamics of parturients who received prophylactic infusion of phenylephrine 50µg/min following spinal anesthesia. Methods: Patients posted for elective cesarean section received a prophylactic phenylephrine infusion of 50µg/min immediately after spinal anesthesia for 30 minutes. Parturients were also co-loaded with lactated Ringer’s solution 1litre. Blood pressure and heart rate was monitored at an interval of 3min initially and after the delivery of baby interval was increased to 5min. Episodes of hypotension, reactive hypertension and bradycardia in mother were recorded. Neonatal APGAR score at 1 and 5min was also recorded. Results: One hundred and forty parturients were included in the study. Twenty patients (14.28%) developed hypotension. Out of 20 patients who developed hypotension, 3 patients (15%) had a single episode, 11 patients (55%) had 2 episodes and 6 patients (30%) had 3 episodes of hypotension. Three patients (2.14%) had reactive hypertension. None of the patients had bradycardia. There was no episode of hypotension induced nausea vomiting. Mean APGAR score at 1min and 5min was 8 and 9 respectively. Conclusion: The prevalence of hypotension with prophylactic phenylephrine infusion was low. We found minimal episodes of reactive hypertension, no episodes of bradycardia and no adverse effect on fetus. It can be regarded a safe means to minimize hypotension in obstetric spinal anesthesia.

Comparison of Prophylactic Infusion of Phenylephrine and Ephedrine for the Prevention of Hypotension in Elective Lower Segment Caesarean Section Under Spinal Anesthesia.

Comparison of Prophylactic Infusion of Phenylephrine and Ephedrine for the Prevention of Hypotension in Elective Lower Segment Caesarean Section Under Spinal Anesthesia.

Oxytocin infusion for maintenance of uterine tone under prophylactic phenylephrine infusion for prevention of post-spinal hypotension in cesarean delivery: a prospective randomised double-blinded dose-finding study

BackgroundPrior studies have shown that, when administered as an intravenous bolus to prevent uterine atony, prophylactic phenylephrine infusion increased the dose requirement of oxytocin and second-line uterotonics. For the prevention of uterine atony, oxytocin should be delivered by continuous infusion. Here, we aimed to determine the ED50 and ED90 parameters (the effective doses for 50 and 90% patients without uterine atony) of oxytocin for co-infusion with prophylactic phenylephrine during cesarean delivery.MethodsIn this prospective randomized double-blinded dose-finding study, one hundred patients were divided into four groups to receive 2.5, 5.0, 7.5, or 10 IU/h oxytocin infusion, after the umbilical cord was clamped during the study period. The uterine tone was evaluated and defined as either adequate or inadequate. Probit regression analysis was applied to calculate the ED50 and ED90 of oxytocin infusion. Uterine tone, the percentage of patients who needed additional oxytocin bolus, second-line uterotonics, side effects, estimated blood loss, and neonatal outcomes were monitored.ResultsThe estimated ED50 and ED90 values of the oxytocin infusion doses for the prevention of uterine atony were 1.9 IU/h (95% CI -4.6-3.8) IU/h and 9.3 IU/h (95% CI 7.3–16.2) IU/h, respectively. Across groups, there was a significant linear trend between the infusion dose and the percentage of patients who required additional oxytocin (p-value = 0.002). No differences were observed in the incidence of side effects and neonatal outcomes.ConclusionUnder the conditions of this study, the ED90 of oxytocin infusion for the prevention of uterine atony was 9.3 IU/h, which is higher than the current recommendation. This finding is helpful for clinical practice, because of the routine use of phenylephrine in cesarean delivery. Further studies are needed to determine the appropriate initial bolus of oxytocin after neonatal delivery.Trial registrationThe study was registered on the Chinese Clinical Trial Register (register no. ChiCTR2200059556).

A Prospective Single-Center Brazilian Study Investigating the Efficacy and Safety of Prophylactic Phenylephrine Infusion for the Management of Hypotension During Cesarean Section Under Spinal Anesthesia.

Background Maternal hypotension occurs in up to 80% of parturients during cesarean section (CS) under spinal anesthesia. Phenylephrine, a direct-acting α-1 agonist, has been widely recommended for the prevention of hypotension. We evaluated the efficacy and safety of phenylephrine infusion to prevent hypotension in obese and non-obese patients during cesarean section. Methods One hundred forty-one patients were included in this single-arm study. Patients received prophylactic phenylephrine infusion at a rate of 50 μg/min-1 immediately after spinal local anesthetic injection until delivery.Hypotension was defined as a systolic blood pressure <100 mmHg or <20% of baseline. The primary outcome was the incidence of hypotension. Results The incidence of hypotension was 17%. The median and interquartile range (IQR) of the number of hypotensive episodes was 0 (0-0). It was observed that 79.1% of the patients had hypotension in the first six minutes. Reactive hypertension and bradycardia occurred in 20.5 and 12.7% of the patients, respectively. In addition, there was a higher incidence of bradycardia in pregnant women with a body index mass of < 30 kg/m-2.Patients with baseline systolic blood pressure <120 mmHg had a threefold increased risk of hypotension. The incidence of nausea and vomiting was 13.4 and 2.8%, respectively. The incidence of an Apgar score <7 at the first minute was 2.8%, and no neonates presented an Apgar score <7 at the fifth minute. A pH of <7.2 occurred in 6.3% of the neonates.All neonates had no sequelae and were discharged together with their mothers. Conclusion The prophylactic infusion of phenylephrine 50 μg/min-1 is safe and demonstrates efficacy in reducing maternal hypotension providing adequate maternal hemodynamic stability during CS under spinal anesthesia.

Prophylactic Fixed-Rate Phenylephrine Versus Norepinephrine Infusion in the Prevention of Post-spinal Anesthesia Hypotension During Cesarean Delivery.

Background Maternal hypotension following spinal anesthesia can be actively countered by the use of vasopressors. Prophylactic infusion of vasopressors with a rescue bolus dosing was observed to be more effective for hemodynamic stability when compared to administering a bolus dose alone. Although phenylephrine is the recommended drug to treat spinal hypotension, many recent studies have focussed on the role of norepinephrine infusions during cesarean section. In this study, we compared prophylactic fixed-rate intravenous infusions of phenylephrine and norepinephrine during cesarean delivery under spinal anesthesia and the requirement of intraoperative provider-administered rescue bolus of phenylephrine needed to overcome post-spinal anesthesia hypotension. Methodology A total of 208 patients undergoing elective cesarean section under spinal anesthesia were randomly assigned to two groups (group P and group N). Group N included 104 patients who received norepinephrine infusion at a rate of 2.5 μg/minute (0.04 μg/kg/minute), and group P included 104 patients who received phenylephrine infusion at a rate of 50 μg/minute (0.8 μg/kg/minute)to treat spinal hypotension. The primary outcome of our study was to compare the reduction in the number and total dose of intraoperative provider-administered rescue bolus of phenylephrine needed to maintain systolic blood pressure. The secondary outcome of our study was to compare the neonatal outcome using umbilical venous blood gas sampling and Apgar score at one and five minutes. Results The total number of phenylephrine rescue bolus required to treat hypotension was significantly lower in group N (p = 0.0005) compared to group P. The neonatal outcome was similar between the two groups. Conclusions Prophylactic norepinephrine infusion when compared to prophylactic phenylephrine infusion is associated with a lesser requirement of rescue phenylephrine boluses.

A survey in the West Midlands of the United Kingdom of current practice in managing hypotension in lower segment caesarean section under spinal anaesthesia

BackgroundSpinal anaesthesia, the most common form of anaesthesia for caesarean section, leads to sympathetic blockade and profound maternal hypotension resulting in adverse maternal and neonatal outcomes. Hypotension, nausea and vomiting remain common but until the publication of the National Institute of Health and Care Excellence (NICE) 2021 guidance, no national guideline existed on how best to manage maternal hypotension following spinal anaesthesia for caesarean section. A 2017 international consensus statement recommended prophylactic vasopressor administration to maintain a systolic blood pressure of >90% of an accurate pre-spinal value, and to avoid a drop to <80% of this value.This survey aimed to assess regional adherence to these recommendations, the presence of local guidelines for management of hypotension during caesarean section under spinal anaesthesia, and the individual clinician’s treatment thresholds for maternal hypotension and tachycardia. MethodsThe West Midlands Trainee-led Research in Anaesthesia and Intensive Care Network co-ordinated surveys of obstetric anaesthetic departments and consultant obstetric anaesthetists across 11 National Health Service Trusts in the Midlands, England. ResultsOne-hundred-and-two consultant obstetric anaesthetists returned the survey and 73% of sites had a policy for vasopressor use; 91% used phenylephrine as the first-line drug but a wide range of recommended delivery methods was noted and target blood pressure was only listed in 50% of policies. Significant variation existed in both vasopressor delivery methods and target blood pressures. ConclusionsAlthough NICE has since recommended prophylactic phenylephrine infusion and a target blood pressure, the previous international consensus statement was not adhered to routinely.

Comparison of Carbetocin as a Bolus or Infusion With Prophylactic Phenylephrine on Maternal Heart Rate During Cesarean Delivery Under Spinal Anesthesia: A Double-Blinded Randomized Controlled Trial

(Can J Anesth/J Can Anesth. 2022:69:715–725) Carbetocin is used in elective cesarean deliveries to reduce the risk of postpartum hemorrhage, and the current practice is to administer the drug as a bolus injection. Side effects of carbetocin include low blood pressure and elevated or irregular heart rate. For some patients, this may lead to hemodynamic alterations and raises the question of potential benefits to heart rate and other hemodynamic factors by administering carbetocin via a 10-minute infusion. This study compared a bolus injection to a 10-minute infusion, both with a prophylactic infusion of phenylephrine, to understand if there are significant and clinically applicable differences in heart rate. This study primarily examined variation in heart rate within 20 minutes of drug administration, but also examined other hemodynamic factors such as blood pressure and stroke volume.

A Randomized Controlled Trial Comparing the Effect of Phenylephrine by Intramuscular Route With Intravenous Infusion in Maintaining Haemodynamic Stability During Elective Lower Segment Caesarean Section Under Spinal Anaesthesia.

Background Hypotension is a commonly encountered side effect in patients undergoing spinal anaesthesia, particularly in patients undergoing caesarean section. Phenylephrine is a widely used drug to treat spinal-induced hypotension and to maintain hemodynamic stability. Our aim is to evaluate the effectiveness of phenylephrine given through two different routes prophylactically in prevention of post-spinal hypotension in patients undergoing caesarean section. Methods A total of 150 healthy pregnant women undergoing elective caesarean section were randomly allocated into three groups: Group M (prophylactic intramuscular use of 2 mg phenylephrine), group V (prophylactic intravenous infusion of 30 mcg phenylephrine per minute), and group P (no prophylaxis), rescue phenylephrine 30 mcg IV and atropine 0.6 mg IV were used intraoperatively to treat bradycardia and hypotension in all three groups. The primary outcome was maternal hemodynamic changes. Results There was an insignificant difference in demographic data between the groups. Maternal systolic and diastolic blood pressure were more stable in group M compared to group V and group P. Heart rate was significantly lower only in group V. We did not observe any statistical difference between the groups in the APGAR score or the fetal arterial blood gas values. The incidence of nausea and vomiting was more in group P. Conclusion Preventive intramuscular phenylephrine exhibited a more stable maternal hemodynamics when compared with the prophylactic intravenous infusion of phenylephrine and placebo in elective caesarean under spinal anaesthesia.

Determination of the Relative Potency of Norepinephrine and Phenylephrine Given as Infusions for Preventing Hypotension During Combined Spinal-Epidural Anesthesia for Cesarean Delivery: A Randomized Up-And-Down Sequential Allocation Study.

Purpose: The relative potency of norepinephrine and phenylephrine given as boluses to treat hypotension during spinal anesthesia for cesarean delivery has been reported but few data are available for infusions. This study aimed to determine the relative potency of norepinephrine and phenylephrine when given by infusion for preventing hypotension during combined spinal-epidural anesthesia for cesarean delivery. Methods: This was a prospective, randomized, double-blind, up-and-down sequential allocation study. Patients were randomly allocated to receive a prophylactic infusion of norepinephrine or phenylephrine started immediately after induction of anesthesia. The first patients received either norepinephrine 0.1 μg/kg/min or phenylephrine 0.5 μg/kg/min. An effective infusion rate was defined when no hypotension occurred before delivery. For each subsequent patient, the norepinephrine infusion rate was decreased or increased by 0.01 μg/kg/min or the phenylephrine infusion rate was decreased or increased by 0.05 μg/kg/min according to whether the infusion was effective or ineffective respectively in the previous patient. Values for the infusion rate that was effective in preventing hypotension in 50% of patients (ED50) for norepinephrine and phenylephrine were estimated using up-and-down sequential analysis and relative potency was estimated. Probit regression was used as a backup and sensitivity analysis. Results: The ED50 values for norepinephrine and phenylephrine calculated by the up-and-down method were 0.061 (95% CI 0.054–0.068) μg/kg/min and 0.368 (95% CI 0.343–0.393) μg/kg/min respectively. The estimated relative potency ratio for ED50 for norepinephrine to phenylephrine was 6.03:1 (95% CI 5.26:1 to 6.98:1). Conclusion: Under the conditions of this study, norepinephrine given by infusion was about 6 times more potent than phenylephrine. This information is useful for clinical practice and further comparative studies of norepinephrine versus phenylephrine. Clinical Trial Registration: http://www.chictr.org.cn/showproj.aspx, identifier [ChiCTR2200056237]

The association of maternal obesity with fetal pH in parturients undergoing cesarean delivery under spinal anesthesia

Objective The aim of this study was to examine the relationship between maternal obesity and fetal umbilical arterial pH in a cohort of parturients that received a prophylactic phenylephrine infusion for management of spinal anesthesia induced hypotension during cesarean delivery. Methods This was a retrospective cohort study of cesarean deliveries at a single academic tertiary care institution between January 2012 and March 2019. All scheduled nonlaboring cesarean deliveries of singleton live neonate performed under spinal anesthesia between 37 and 41weeks gestational age were included. The primary outcome was umbilical arterial pH. Multiple regression models were used to test the relationship between umbilical arterial pH, and maternal body mass index (BMI), race, dose of phenylephrine, baseline systolic blood pressure, maximum decrease in systolic blood pressure, induction of anesthesia to delivery time and uterine incision to delivery time. Results Seven hundred and sixty-one mother neonate pairs were included in the study. The univariate analysis showed a decrease in mean umbilical arterial pH with increasing maternal BMI (p = <0.01). A multivariate regression model indicated that maximum decrease in systolic blood pressure, induction of anesthesia to delivery time, and uterine incision to delivery time accounted for 11% of the variance in the outcome, R2 = 0.11. BMI was not a significant predictor of low umbilical arterial pH (p = 0.36). The significant predictors of low umbilical arterial pH in the model were maximum decrease in systolic blood pressure (p < 0.001), induction of anesthesia to delivery time (p = 0.04), and uterine incision to delivery time (p < 0.001). Conclusions Maternal BMI is not associated with lower umbilical arterial pH in women having scheduled cesarean delivery under spinal anesthesia. Severity of spinal anesthesia induced hypotension is greater with increasing BMI and may be responsible for the observed decrease in umbilical arterial pH.

Comparison of Prophylactic Phenylephrine Infusion Versus Intravenous Ondansetron on Hypotension During Spinal Anesthesia for Cesarean Section

Multiple methods have been proposed to prevent the incidence of hypotension in women undergoing cesarean section under spinal anesthesia. This study was conducted to compare the efficacy of phenylephrine (50 μg.min-1) versus ondansetron (8 mg) in the prevention of such complications. We included a total of 184 full-term pregnant women who were randomly divided into two groups: Group P included 92 cases who were commenced on phenylephrine infusion (50 μg.min-1 given after puncture) and Group O included the other 92 cases who were administered ondansetron (8 mg given 5 min before puncture). Demographic data were not significantly different between the two groups. Maternal hypotension was significantly more encountered in the ondansetron group (51.6% vs. 22%) and ephedrine was used more significantly in that group (19.8% vs. 8.8%). In addition, nausea and skin flushing were more commonly encountered in the same group. The incidence of vomiting and patient discomfort was not significantly different between the two study groups. Phenylephrine is markedly superior to ondansetron in the prevention of maternal hypotension and vasopressor need during cesarean section under spinal anesthesia.

Comparison of carbetocin as a bolus or an infusion with prophylactic phenylephrine on maternal heart rate during Cesarean delivery under spinal anesthesia: a double-blinded randomized controlled trial.

Carbetocin, an oxytocin analog, given as a postpartum hemorrhage prophylaxis in elective Cesarean deliveries, frequently causes tachycardia and hypotension. Phenylephrine infusion has been shown to prevent spinal anesthesia-induced hypotension. The goal of this study was to evaluate if a slow infusion of carbetocin would reduce maternal heart rate variation and hemodynamic disturbances compared with a rapid bolus in parturients receiving a prophylactic phenylephrine infusion during elective Cesarean delivery. In this double-blinded randomized controlled trial, 70 healthy parturients were allocated to either a bolus group or an infusion group. At cord clamping, participants in the bolus group received carbetocin 100 µg as a rapid intravenous bolus, while participants in the infusion group received carbetocin 100 µg over 10 min. The primary outcome was the variation in maternal heart rate from baseline during the 20 min following cord clamping. Secondary outcomes included blood pressure, cardiac output, and stroke volume variations during the study period, measured with the ClearSight™ hemodynamic monitor. Maximum heart rate variation was not different between the groups: bolus group, mean (standard deviation) 29.8 (25.2)% vs infusion group, 27.2 (23.3)%; P = 0.67. The increase in heart rate occurred significantly earlier in the bolus group than in the infusion group (median [interquartile range] time, 105 [69-570] sec vs 485 [255-762] sec; P = 0.02; group × time interaction: two-way repeated measures ANOVA, P = 0.04). There was no significant difference in maximum variations for the other hemodynamic parameters between the groups. Carbetocin infused over ten minutes did not reduce the magnitude of maternal heart rate variation but delayed its occurrence. This finding could be relevant to the anesthesiologist caring for parturients in whom a slight increase in maternal heart rate is clinically undesirable. www. gov (NCT03404544); registered 19 January 2018.

Comparison of prophylactic infusion of phenylephrine with ephedrine for prevention of hypotension in elective lower segment caesarian section under spinal anasthesia

Introduction: Hypotension is the most important complication following spinal anesthesia for caesarian delivery, which can produce adverse maternal symptoms and neonatal acid-base effects. Prompt effective treatment is considered essential to prevent fetal academia. Ephedrine and phenylephrine are two drugs known to prevent the hypotension following spinal anesthesia. Aim &amp; Objective: Comparative evaluation of effect of prophylactic infusion of phenylephrine and ephedrine as a vasopressor therapy in spinal anesthesia in patients undergoing caesarian section and their effect on neonatal outcome. Observation: ephedrine and phenylephrine both maintained systolic, diastolic and mean arterial pressure, but ephedrine group required more additional bolous than phenylephrine group (p value &lt;0.001). Phenylephrine group had acceptable pH value and lower acidosis than ephedrine group (p value &lt;0.05). Conclusion: prophylactic Phenylephrine in a dose of 15 mcg/min is more efficacious in Comparision to Ephedrine 1.5 mg/min in maintaining arterial blood pressure following spinal anesthesia for caesarian section and has less neonatal acidosis.

Effect of low dose phenylephrine infusion on shivering and hypothermia in patients undergoing cesarean section under spinal anesthesia: a randomized clinical trial

BackgroundShivering is a common complication of spinal anesthesia. Phenylephrine, due to its peripheral vasoconstrictive effect, may limit the core to periphery redistribution of body temperature following spinal anesthesia, and reduce hypothermia and shivering. We hypothesized that prophylactic phenylephrine infusion would reduce shivering and hypothermia in women undergoing cesarean section under spinal anesthesia. MethodsA two-arm randomized, double-blind, placebo-controlled trial in term pregnant patients undergoing cesarean section. In the phenylephrine group (n=75) prophylactic phenylephrine infusion was administered at 25 µg/min immediately after initiation of spinal anesthesia and continued until the end of the operative period. In the placebo group (n=75) a normal saline infusion was administered during the same period. The primary outcome was the incidence of shivering; secondary outcomes were severity of shivering, changes in nasopharyngeal (core) temperature, and incidence of hypotension and bradycardia. ResultsThe incidence of shivering in the phenylephrine and control groups was 24.0% (95% CI 14.3% to 33.7%) and 53.3% (95% CI 42.0% to 64.6%), respectively. The severity of shivering was greater in the control group (P=0.002) and the mean (±SD) end of surgery core temperature was significantly higher in the phenylephrine group (35.84°C ± 0.60) compared with controls (35.61°C ± 0.48) (P=0.009). The incidence of hypotension was higher in controls (53.4% vs. 2.7%; P <0.001) but bradycardia more frequent in group P (P=0.023). ConclusionThe incidence of shivering and degree of hypothermia were significantly reduced by a prophylactic phenylephrine infusion during cesarean section under spinal anesthesia.

Comparison of prophylactic phenylephrine and norepinephrine infusion on umbilical arterial pH and maternal blood pressure during spinal anaesthesia for caesarean delivery.

Background and Aims:Spinal anaesthesia induced maternal hypotension in parturients undergoing caesarean delivery may lead to neonatal acidosis and fall in umbilical artery pH. The aim of this study was to compare low dose norepinephrine infusion with phenylephrine to see the effect on umbilical arterial pH and maternal blood pressure during spinal anaesthesia for caesarean delivery.Methods:In a randomised, double-blind study, 60 parturients belonging to American Society of Anesthesiologists grade II, age 18–35 years with singleton term pregnancy were divided into the phenylephrine group and norepinephrine group. Participants received prophylactic phenylephrine and norepinephrine infusion after spinal anaesthesia till the delivery of the baby at a fixed rate of 50 μg/min and 2.5 μg/min, respectively. The primary outcome was umbilical artery pH. Neonatal Apgar score, incidence of bradycardia and hypotension, number of boluses of vasopressor required and reactive hypertension were also compared.Results:The umbilical arterial pH was comparable between the groups (p = 0.38). Apgar scores were comparable (p = 0.17). Incidence of bradycardia was higher in phenylephrine group without reaching statistical significance (43.3% vs. 20%, P = 0.052). Incidence of hypotension was more but not significant in norepinephrine group compared to phenylephrine group (16.7% vs. 10%, P = 0.44). Number of vasopressor boluses and reactive hypertension episodes were comparable between both groups (p = 0.09).Conclusion:Low dose (2.5 μg/min) intravenous infusion of norepinephrine is a suitable alternative to phenylephrine in the maintenance of umbilical arterial pH and maternal blood pressure.

Effect of maternal body mass index on the prophylactic dose of phenylephrine for preventing hypotension in parturients after spinal anaesthesia

BackgroundTo compare the median effective dose (ED50) of phenylephrine for prophylactic continuous infusion in parturients with different body mass indices (BMIs) during combined spinal-epidural anaesthesia for caesarean section and to investigate the impact of maternal BMI on the prophylactic dose of phenylephrine. MethodsParturients receiving combined spinal-epidural anaesthesia for elective caesarean section were divided into a standard group (Group S, BMI < 30 kg/m2) and an obesity group (Group O, BMI > 30 kg/m2), each with 30 patients. A sequential allocation design was used to administer the prophylactic infusion of phenylephrine after the completion of a spinal anaesthetic injection to prevent hypotension (defined as a reduction of systolic blood pressure ≥ 20% of the baseline value or systolic blood pressure < 90 mmHg), with an initial infusion rate of 50 μg/min for the first parturient subsequent adjusted up or down by 10 μg/min depending on whether the previous parturient developed hypotension or not during the study period. The Dixon and Massey method and the isotonic regression method were used to calculate and compare the ED50 and 95% confidence interval (CI) of phenylephrine between the two groups. ResultsThe results were 21.92 μg/min (95% CI, 14.90–28.94 μg/min) for Group S and 42.14 μg/min (95% CI, 24.58–59.70 μg/min) for Group O. The ratio of relative potency of Group O to Group S is 1.92 (95% CI 1.09–3.14), P = 0.034. ConclusionsThe dose of phenylephrine for the prevention of hypotension after spinal anaesthesia for caesarean section is dependent on maternal BMI. Therefore, a weight-based phenylephrine dose is reasonable.