Prevention of maternal hypotension after regional anaesthesia for caesarean section. Curr Opin Anaesthesiol. 2010;23:304-309. [PMID: 20173633 DOI: 10.1097/aco.0b013e328337ffc6]

Postspinal Anesthesia Hypotension in Caesarean Delivery: A Narrative Review

Anesthesiologists frequently deal with spinal hypotension when administering spinal anesthesia (SA) for a Caesarean section (C-section). The physiological changes that occur during pregnancy necessitate modifications to anesthesia and analgesia procedures to provide safe and efficient care for the expectant patient. It is believed that giving the patient SA during a C-section will increase their degree of comfort and pain management both during and after the surgical process. It is less expensive, easier to give, and delivers a consistent anesthetic onset, early ambulation, and the start of breastfeeding. As C-section is a very common operation performed in every healthcare unit, dealing with postspinal hypotension is a daily situation faced by anesthetists with variable levels of experience. However, understanding and addressing hypotension induced by SA is crucial as it affects the mother and the fetus negatively. This review aims to contribute to enhancing patient care and safety in the context of C-sections by identifying hypotension timely and managing it effectively. It is advised to healthcare workers to leverage the insights from the review to improve patient outcomes in routine practice.

Non-Invasive Monitoring during Caesarean Delivery: Prevalence of Hypotension and Impact on the Newborn

BACKGROUND

The aim of our study was to investigate the prevalence of perioperative hypotension after spinal anesthesia for cesarean section using non-invasive continuous hemodynamic monitoring and its correlation with neonatal well-being.

METHODS

We included 145 patients. Spinal anesthesia was performed with a combination of hyperbaric bupivacaine 0.5% (according to a weight/height scheme) and fentanyl 20 μg. Hypotension was defined as a mean arterial pressure (MAP) < 65 mmHg or <60 mmHg. We also evaluated the impact of hypotension on neonatal well-being.

RESULTS

Perioperative maternal hypotension occurred in 54.5% of cases considering a MAP < 65 mmHg and in 42.1% with the more conservative cut-off (<60 mmHg). Severe neonatal acidosis occurred in 1.4% of neonates, while an Apgar score ≥ 9 was observed in 95.9% at 1 min and 100% at 5 min.

CONCLUSIONS

Continuous non-invasive hemodynamic monitoring allowed an early detection of maternal hypotension leading to a prompt treatment with satisfactory results considering neonatal well-being.

Effects of Hyperbaric and Isobaric Bupivacaine on Hemodynamic Profiles and Block Characteristics Among Parturients Undergoing Elective Cesarean Section Under Spinal Anesthesia: A Randomized Controlled Trial

Background

Cesarean section (CS) is a surgical procedure where the baby is delivered through incisions made in the abdomen and uterus. Bupivacaine is a widely recognized local anesthetic available in different baricity and it is frequently used for spinal anesthesia. The baricity of bupivacaine impacts hemodynamic profiles and block characteristics.

Objective

To compare the effects of hyperbaric and isobaric bupivacaine on hemodynamic profiles and block characteristics among parturients undergoing elective cesarean section under spinal anesthesia at Dilla University Referral Hospital.

Methods

64 pregnant mothers scheduled for elective cesarean section under spinal anesthesia were randomly assigned to two groups: Group A received a dose of 12.5 mg of isobaric bupivacaine (n = 32), Group B received a dose of 12.5 mg of hyperbaric bupivacaine (n = 32). Prior to conducting the study, the necessary ethical approvals were obtained. For comparing numerical variables between the two groups, the independent Sample t-test or Mann-Whitney U-test was employed as needed. Repeated measurements were analyzed using mixed ANOVA. Categorical variables were assessed using either the chi-square test or Fisher's exact test. Statistical significance was set at P < 0.05, with a power of 90%.

Results

The mean Systolic Blood Pressure (SBP), Diastolic Blood pressure (DBP), and Mean Arterial Blood Pressure (MAP) showed significant decrement in the group receiving isobaric spinal anesthesia compared to those receiving hyperbaric bupivacaine. The decrement was observed from the 6th to 30th minute (p<0.05). Furthermore, the hyperbaric group had a faster onset time for achieving the maximum sensory block, with a median time of 3 (1) min compared to 4 (2) mins in the isobaric group (p<0.001).

Conclusion and Recommendation

We conclude that hyperbaric bupivacaine provides stable intraoperative hemodynamic parameters and an earlier onset of block than isobaric bupivacaine. Therefore, we recommend clinicians to use hyperbaric bupivacaine for cesarean delivery.

Efficacy of fixed-dose phenylephrine bolus for treating post-spinal hypotension: Comparison between pre-eclamptics and normotensives

Background and Aims

Pre-eclamptic parturients may have an exaggerated response to vasopressors. This study compares the efficacy of a 50 μg fixed bolus of phenylephrine for treatment of post-spinal hypotension in pre-eclamptic versus normotensive parturients.

Material and Methods

After written informed consent and ethics committee approval, 30 normotensive and 30 pre-eclamptic parturients between 18 and 40 years with singleton term pregnancy about to undergo cesarean section (CS) under spinal anesthesia were included. Post-spinal hypotension was treated with a 50 μg fixed bolus of phenylephrine. The cumulative dose of phenylephrine, the number of boluses, and the median dose required to treat the first hypotensive episode, total number of hypotensive episodes, maternal side effects, neonatal appearance, pulse, grimace, activity, and respiration (APGAR) scores, and umbilical arterial cord blood pH were noted. Statistical analysis was done using Student's t-test, Mann-Whitney U-test, Chi-square test/Fisher's exact test as appropriate. A P <0.05 was considered significant.

Results

The cumulative dose and number of boluses of phenylephrine required to treat post-spinal hypotension were comparable. The median dose required to treat the first episode of post-spinal hypotension was also similar (p = 0.792). The time to develop the first hypotensive episode was significantly earlier for group N (p = 0.002). The efficacy of a single fixed bolus of 50 μg phenylephrine was similar in both groups (p = 1.000). Neonatal median APGAR scores at 1 min after birth were significantly higher for group N (p = 0.016).

Conclusion

A fixed-dose bolus of 50 μg phenylephrine is safe and effective in treating post-spinal hypotension in pre-eclampsia. The efficacy of phenylephrine is comparable in pre-eclamptic and normotensive parturients.

Can Hypotension Episodes that were not Identified in the Non-Invasive Blood Pressure be Detected during Cesarean Section? A Randomized Controlled Trial

Background:

Aims:

Study Design:

Methods:

Results:

Conclusion:

Prophylactic Phenylephrine Increases the Dose Requirement of Oxytocin to Treat Uterine Atony During Cesarean Delivery: A Double-Blinded, Single-Center, Randomized and Placebo-Controlled Trial

Purpose: Studies involving mouse models and human uterine smooth muscle cells have shown that phenylephrine inhibits uterine contractions in non-pregnant mice and human in vitro cell via cyclic adenosine monophosphate (cAMP) signaling. However, there has been no limited exploration to date of the effect of phenylephrine on uterine contractions in clinical practice. This study aimed to compare the dose requirement of oxytocin with or without the infusion of prophylactic phenylephrine to prevent post spinal hypotension during cesarean delivery under combined spinal and epidural anesthesia.

Methods: This was a double-blinded, single-center, randomized, control study. One hundred and sixty pregnant patients provided informed consent and were randomly allocated to the phenylephrine (phenylephrine infusion) and control (saline infusion) groups. Patients randomized to the phenylephrine group received an intravenous prophylactic phenylephrine infusion at a fixed rate of 0.5 μg/kg/min. The control group received a saline placebo at the same rate and used the same apparatus for delivery. After neonatal delivery and clamping of the umbilical cord, patients received a standard institutional oxytocin protocol. The primary outcome measure was the total dose of oxytocin administered during CD. Secondary outcomes including the proportion (%) of patients requiring a secondary uterotonic agent and estimated blood loss (EBL) in the first 24 h after surgery.

Results: The median oxytocin dose administered was significantly higher in the phenylephrine group than in the control group [6.9 ± 2.5 international standardized units (IU) vs. 5.4 ± 2.4 IU, p = 0.0004]. The number of patients that required a secondary uterotonic agent was significantly higher in the phenylephrine group than in the control group (24.2% vs. 9.1%; p = 0.034). The EBL in the first 24-h postoperatively was similar between the two groups (467 ± 47 ml vs. 392 ± 38 ml; p = 0.22).

Conclusions: Prophylactic infusion of phenylephrine used to prevent post-spinal hypotension during CD was associated with a higher dose of oxytocin. This has important clinical implications, as the suboptimal use of oxytocin is associated with an increased risk of postpartum hemorrhage and increased maternal morbidity and mortality. Further studies are now needed to confirm these findings.

A randomised double-blind comparison of phenylephrine and norepinephrine for the management of postspinal hypotension in pre-eclamptic patients undergoing caesarean section

BACKGROUND

Studies comparing phenylephrine and norepinephrine for the treatment of postspinal hypotension in pre-eclamptic patients are limited.

OBJECTIVE

To compare bolus doses of phenylephrine and norepinephrine for treating hypotension in pre-eclamptic mothers undergoing caesarean section under spinal anaesthesia. It was hypothesised that norepinephrine and phenylephrine use would be associated with similar neonatal outcome.

DESIGN

Randomised controlled study.

SETTING

Single centre, tertiary care, university teaching hospital, from December 2018 to March 2020.

PATIENTS

A total of 86 women with pre-eclampsia and a singleton pregnancy who developed postspinal hypotension during caesarean section.

INTERVENTIONS

Patients received intravenous phenylephrine (50 μg) or norepinephrine (4 μg) for treatment of hypotension, defined as a fall in baseline systolic BP by ≥ 20% or an absolute value < 100 mmHg.

MAIN OUTCOME MEASURES

The primary outcome was umbilical artery pH. Secondary outcomes included Apgar scores, the number of hypotensive episodes, vasopressor requirements, the incidence of tachycardia/bradycardia/arrhythmias/hypertension and maternal complications.

RESULTS

Umbilical artery pH was not different between the phenylephrine and norepinephrine groups (7.26 ± 0.06 and 7.27 ± 0.06, respectively; P = 0.903). The median [IQR] number of hypotensive episodes was higher in the norepinephrine than the phenylephrine group: 2 [1 to 3] vs 1 [1 to 2], respectively; P = 0.014. Apgar scores, total number of vasopressor boluses required, systolic BP trends and the incidence of maternal complications were comparable in the two groups. Heart rate (HR) values were lower in phenylephrine group (P = 0.026), and one patient in phenylephrine group and none in the norepinephrine group developed bradycardia (HR < 50 bpm), P = 1.000.

CONCLUSIONS

In women with pre-eclampsia undergoing caesarean section, bolus doses of phenylephrine (50 μg) and norepinephrine (4 μg) used to treat hypotension after spinal anaesthesia are equally effective with similar neonatal and maternal outcomes.

TRIAL REGISTRATION

CTRI/2018/11/016478.

Efficacy of bolus-dose epinephrine to manage hypotension in the prehospital setting

PURPOSE

Hypotension in the Emergency Department (ED) and the prehospital setting has been associated with significant morbidity and mortality. Limited literature exists exploring the utilization of intravenous (IV) bolus-dose epinephrine (BDE) by Emergency Medical Services (EMS).

METHODS

A retrospective review evaluated patients transported to an academic medical center who had received IV BDE by a single urban EMS system from 2016 to 2020. The primary outcome was to assess the influence IV BDE had on systolic blood pressure (SBP). Secondary objectives were to assess changes in heart rate (HR), the impact of dose variability on SBP, and the incidence of severe hypertension (SBP > 220 mmHg).

RESULTS

A total of 55 patients who received 96 administrations of IV BDE were included in the analysis. The most common individual dose was 10 μg (76.0%) and 45.5% received multiple doses. The median weight-based dose of BDE was 0.14 μg/kg. A significant increase in SBP (median 14.0 mmHg) was noted among all patients following BDE administration compared with baseline (p < 0.001). No significant difference was found in HR following BDE compared with baseline (p = 0.375). Those that received a BDE dose >10 μg were noted to have a significantly greater rise in SBP than those that received 10 μg (30.0 mmHg vs. 11.0 mmHg; p = 0.022). Similarly, patients that received a dose ≥0.2 μg/kg had a significantly greater increase in SBP compared with those that received <0.2 μg/kg (30.0 mmHg vs. 10.0 mmHg; p = 0.048). There were no incidences of severe hypertension following therapy.

CONCLUSION

The utilization of IV BDE in the prehospital setting for acute hypotension resulted in a significant rise in SBP. A dose-response relationship was noted both in terms of a flat-based dose and a weight-based dose, with higher doses yielding a greater change in SBP. Additional investigations are necessary to further explore the most appropriate dose of this agent in this setting and its influence, if any, on clinical outcomes.

Maternal heart rate responses in the supine position and their relationship with hypotension and phenylephrine requirements during elective caesarean delivery using spinal anaesthesia: An observational study

BACKGROUND

Hypotension is the main side effect of spinal anaesthesia (SA) for elective caesarean delivery (CD). An increased in heart rate in response to inferior vena cava (IVC) compression has been reported to be predictive of hypotension and vasopressor requirements in this setting. The objective of the study was to evaluate the prevalence of an increase in heart rate in response to IVC compression and its potential effect on hypotension and phenylephrine requirements.

METHODS

Healthy parturients scheduled for elective CD under SA were preoperatively investigated for a positive supine stress test (SST). It was defined as an increase in heart rate (HR) > 10 beats/min after 5 min of supine position. A crystalloid coload and prophylactic phenylephrine infusion were systematically used to maintain systolic arterial pressure (SAP) between 90-100% of baseline. Hypotension was defined as SAP < 80% of baseline.

RESULTS

Among 100 women, 26% had a positive SST. There was no significant difference in the incidence of hypotension: 38% versus 24.3% (p = 0.17) in women with positive SST or without, respectively. The cumulative dose of phenylephrine (450 µg [325-625] versus 350 µg [250-500], p = 0.09) was not significantly different between the two groups. Incidences of reactive hypertension, bradycardia, nausea or vomiting and neonatal outcomes were comparable.

CONCLUSIONS

A positive SST to IVC compression was found in a quarter of term women scheduled for elective CD under SA. This condition has no significant impact on hypotension and phenylephrine requirements when using a crystalloid coload and a phenylephrine infusion targeted at maintaining SAP close to baseline.

Blood pressure measurement during cesarean delivery: Evaluation of a beat-to-beat noninvasive device (NexfinTM)

Early detection of arterial hypotension during cesarean delivery under spinal anesthesia is important. This study aims to compare the validity of NexfinTM as beat-to-beat noninvasive blood pressure monitoring with conventional intermittent oscillometric measurement of blood pressure during elective cesarean delivery.This open prospective observational bicentric study was performed between January 2013 and December 2015. We simultaneously recorded arterial blood pressure with both techniques in pregnant women undergoing elective cesarean delivery under spinal anesthesia. The primary outcome was a Bland-Altman analysis of systolic blood pressure measurement comparing NexfinTM and a conventional method. The secondary outcomes were the time to detect the first relevant hypotensive episode and the comparison of both devices using a four-quadrant graph.One hundred and seventy-four parturients completed the study, and 2640 pairs of systolic blood pressure measurements were analyzed. Bias was -10 mmHg with upper and lower limits of agreement of -61 and +41 mmHg. In 73.9% of the cases, the two techniques provided the same information (normotension or hypotension), but the conventional method missed 20.8% of measurements, with NexfinTM detecting 16.2% more hypotensive measurements. The median [25-75 percentiles] duration to detect the first hypotensive measurement was 331 [206-480] seconds for NexfinTM and 440 [300-500] s for intermittent oscillometry (P < .001).The agreement between NexfinTM and an intermittent method for the measurement of systolic blood pressure was not in an acceptable range during cesarean delivery, although NexfinTM may detect hypotension earlier than the standard method.Trial registration: Clinicaltrials.gov identifier: NCT01732133; November 22, 2012.

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

Purpose: Prophylactic infusion of a vasopressor is preferred as a rational choice in clinical practice in Cesarean delivery. Metaraminol is one of most common vasopressors used in obstetric clinical practice. However, the dose-response of metaraminol has not been fully determined and the optimal infusion dose is unknown. Therefore, this study aimed to determine the median effective dose (ED50) and 90% effective dose (ED90) of weight-based fixed-rate metaraminol infusions for preventing spinal-anesthesia-induced hypotension in patients having combined spinal-epidural anesthesia for elective Caesarean delivery.

Methods: One hundred and seventeen patients with singleton pregnancies were enrolled and randomly allocated into one of five groups in this study. Patients received prophylactic metaraminol infusion at a fixed rate of 0, 0.25, 1.0, 1.75 or 2.5 μg/kg/min in each group immediately after induction with intrathecal 10 mg of hyperbaric bupivacaine mixed with 5 μg of sufentanil. An effective prophylactic dose was defined as no occurrence of hypotension during the period of spinal introduction and neonatal delivery. Values for ED50 and ED90 of prophylactic infusion of metaraminol were calculated using probit regression. Characteristics of spinal anesthesia and side effects were recorded.

Results: The ED50 and ED90 values of weight-based fixed rate of metaraminol infusion were 0.64 (95% CI, 0.04–1.00) μg/kg/min and 2.00 (95% CI, 1.58–2.95) μg/kg/min respectively. The incidence of hypotension decreased with an increased infusion rate of metaraminol in the five groups (test for trend, p < 0.001). The incidence of hypotension was similar between group 0 and 0.25, but significant higher than other groups; the incidence of hypotension was also similar between group 1.0 and 1.75, but higher than group 2.5. The incidence of reactive hypertension was significantly higher in group 2.5 compared to the other groups. Physician interventions were more frequent in group 0, 0.25 and 2.5 than in group 1.0 and 1.75 (adjusted p < 0.001). No difference was found in neonatal outcomes, including Apgar score and pH value of the umbilical artery.

Conclusion: In summary, we have compared four different prophylactic weight-based infusion doses of metaraminol for preventing post-spinal hypotension in Cesarean delivery. The ED₅₀ and ED₉₀ values of metaraminol infusion for preventing spinal anesthesia-induced hypotension were 0.64 μg/kg/min and 2.00 μg/kg/min, respectively. This finding may be helpful for guiding clinical practice and further research.

Management of spinal-induced hypotension for elective caesarean section: A survey of practices among anesthesiologists from a developing country

Background

In developing countries, more than half of the anesthesia-related maternal deaths are related to spinal hypotension.

Objective

To explore the practices of management of spinal induced hypotension with respect to fluid and vasopressor administration among anesthesiologists from a developing country.

Methods

After approval from institutional ethics committee, an online questionnaire was sent to anesthesiologists registered with Pakistan Society of Anesthesiologists between July and August 2018 to determine management strategies for prevention and treatment of spinal-induced hypotension.

Results

The response rate was 36% (156/433), majority from academic institution (62.8%) with equal representation from attending and trainee anesthesiologist. For prophylaxis 39.1% respondents did not use vasopressors, 32.7% used fluid preloading with crystalloids (54.7%) as fluid of choice followed by combination of co-loading and vasopressor(22.4%). Phenylephrine was the vasopressor of choice for both prophylaxis (33.1%) and treatment (57%). Attending anesthesiologist used a combination of fluid co-loading and vasopressors for prophylaxis as compared to trainee anesthesiologists (37.2% vs. 17.9%; P=0.035) and selected vasopressors according to patient's heart rate (33.3% vs. 19.5%; p=0.05). Prophylactic phenylephrine was used more by respondents from the academic institution (p=0.023). Fluid co-loading was used more by respondents with <30 % compared to those with > 30% of clinical responsibility to obstetric anesthesia (P<0.05).

Conclusion

Phenylephrine as the vasopressor of choice indicates growing awareness of management strategies among anesthesiologists from developing countries but there is a need to increase its use for prophylaxis. Some variation in practice according to the level of anesthesiologist, practice type and responsibilities to obstetric anesthesia are evident.

Prevention of hypotension during elective cesarean section with a fixed-rate norepinephrine infusion versus a fixed-rate phenylephrine infusion. Α double-blinded randomized controlled trial

BACKGROUND

Spinal anesthesia for cesarean section can be complicated by hypotension, with untoward effects for both the mother and fetus. Frequently used phenylephrine can lead to baroreceptor-mediated reflex bradycardia. The aim of the present study was to compare a fixed-rate prophylactic norepinephrine infusion to a fixed-rate prophylactic phenylephrine infusion during elective cesarean section under combined spinal-epidural anesthesia.

MATERIALS AND METHODS

Eighty-two parturients were randomized to either norepinephrine 4 μg/min or phenylephrine 50 μg/min fixed-rate infusions, starting simultaneously with the administration of the subarachnoid solution. The primary endpoint was the incidence of maternal bradycardia. Maternal hemodynamics at specific timepoints, the incidence of hypotension or hypertension, the requirement for ephedrine or atropine bolus administration as well as the acid-base status and Apgar score of the neonate were recorded.

RESULTS

The incidence of bradycardia as well as the requirement for atropine administration was lower in the norepinephrine group (4.8% vs. 31.7%, p = 0.004 and 2.4% vs. 24.3%, p = 0.01, respectively). Fetal pH, and fetal blood glucose concentration were higher in the norepinephrine group (p = 0.027 and 0.019, respectively). No difference in the occurrence of hypotension, hypertension, in the requirement for bolus vasoconstrictive medication or in Apgar scores was demonstrated.

CONCLUSIONS

A fixed-rate infusion of norepinephrine is as effective in the management of hypotension during regional anesthesia for cesarean section as a fixed-rate infusion of phenylephrine, with the avoidance of phenylephrine-induced bradycardia. The more favourable neonatal acid-base profile of noradrenaline might be due to better maintenance of placental blood flow in the noradrenaline group due to its beta action, while the higher fetal glucose concentration in the same group might result from a catecholamine-stimulated glucose metabolism increase and a β-receptor mediated insulin decrease.

Control of Spinal Anesthesia-Induced Hypotension in Adults

Spinal anesthesia-induced hypotension (SAIH) occurs frequently, particularly in the elderly and in patients undergoing caesarean section. SAIH is caused by arterial and venous vasodilatation resulting from the sympathetic block along with a paradoxical activation of cardioinhibitory receptors. Bradycardia after spinal anesthesia (SA) must always be treated as a warning sign of an important hemodynamic compromise. Fluid preloading (before initiation of the SA) with colloids such as hydroxyethyl starch (HES) effectively reduces the incidence and severity of arterial hypotension, whereas crystalloid preloading is not indicated. Co-loading with crystalloid or colloid is as equally effective to HES preloading, provided that the speed of administration is adequate (ie, bolus over 5 to 10 minutes). Ephedrine has traditionally been considered the vasoconstrictor of choice, especially for use during SAIH associated with bradycardia. Phenylephrine, a α₁ adrenergic receptor agonist, is increasingly used to treat SAIH and its prophylactic administration (ie, immediately after intrathecal injection of local anesthetics) has been shown to decrease the incidence of arterial hypotension. The role of norepinephrine as a possible alternative to phenylephrine seems promising. Other drugs, such as serotonin receptor antagonists (ondansetron), have been shown to limit the blood pressure drop after SA by inhibiting the Bezold–Jarisch reflex (BJR), but further studies are needed before their widespread use can be recommended.

Comparing the Effect of Bupivacaine and Ropivacaine in Cesarean Delivery with Spinal Anesthesia

Background

Spinal anesthesia is the most common technique used for cesarean delivery due to some advantages compared to regional anesthesia. It is easily performed and provides a rapid onset of block. Though bupivacaine is a generally used long-acting amide type local anesthetic drug for spinal anesthesia, ropivacaine may sometimes be selected.

Objectives

This prospective, randomized, double-blinded study was aimed at comparing clinical efficacy and safety between ropivacaine and bupivacaine during cesarean section.

Methods

After getting ethical committee approval and written informed consent, 65 women who referred to Imam Khomeini Hospital of Ahvaz, Iran in 2018 were chosen for elective cesarean delivery under spinal anesthesia. They were randomly allocated to receive either ropivacaine 1% (n = 33) or bupivacaine 0.5% (n = 32). Afterwards, the differences in the anesthetic efficacy, vital signs, and hemodynamics of participants between the two groups were recorded.

Results

Duration of sensory block was shorter in the ropivacaine group than bupivacaine group (132.5 ± 21.6 min vs. 175.8 ± 26.2 min; P < 0.001). Ropivacaine also produced a shorter duration of motor blockade than bupivacaine (124.8 ± 20.2 min vs. 168.2 ± 21.7 min; P < 0.001). There is no difference between the two groups in terms of systolic and diastolic blood pressure, but the heart rate of patients in the bupivacaine group is significantly higher than the ropivacaine group.

Conclusions

The results suggest that ropivacaine and bupivacaine are two efficient drugs in anesthesia in the cesarean section, ropivacaine is a better choice due to little influence on the hemodynamics and shorter duration of sensory block and motor block which are useful for the recovery and also safe to the patients.

Comparison of the ED50 and ED95 of Intrathecal Bupivacaine in Parturients Undergoing Cesarean Delivery With or Without Prophylactic Phenylephrine Infusion: A Prospective, Double-Blind Study

BACKGROUND AND OBJECTIVES

While prophylactic phenylephrine infusions during cesarean delivery are often used to counteract the sympathectomy associated with spinal anesthesia, their use has been associated with decreased rostral spread of local anesthetic. The purpose of this study was to determine the median effective dose (ED50) and 95% effective dose (ED95) of intrathecal hyperbaric bupivacaine for cesarean delivery in the presence and absence of prophylactic phenylephrine infusion.

METHODS

One hundred healthy parturients undergoing elective cesarean delivery under combined spinal-epidural anesthesia were enrolled in this randomized, double-blind, dose-finding study to determine ED50 and ED95. Subjects were randomly assigned to receive prophylactic phenylephrine or control (saline) infusion with injection of 6, 7.5, 9, 10.5, or 12 mg intrathecal hyperbaric bupivacaine. An effective dose was defined as achieving a T5 sensory level within 10 minutes of intrathecal drug administration without the need for epidural supplementation.

RESULTS

The ED50 of intrathecal hyperbaric bupivacaine was 10.0 mg (95% confidence interval [CI], 5.9-11.4 mg) with prophylactic phenylephrine infusion and 7.9 mg (95% CI, 2.3-9.4 mg) in the control group. The ED95 of intrathecal hyperbaric bupivacaine was 14.1 mg (95% CI, 12.3-37.6 mg) with prophylactic phenylephrine infusion and 11.7 mg (95% CI, 9.9-22.8 mg) in the control group.

CONCLUSIONS

The administration of prophylactic phenylephrine infusion results in higher intrathecal hyperbaric bupivacaine dosing requirements in parturients undergoing cesarean delivery.

CLINICAL TRIAL REGISTRATION

This study was registered at the Chinese Clinical Trial Registry, identifier ChiCTR-TRC-16008938.

ED50 and ED95 of intrathecal hyperbaric ropivacaine for parturients undergoing cesarean section with prophylactic infusion of phenylephrine: A Prospective dose-finding Study

BACKGROUND

Studies have reported that the ED50 of intrathecal ropivacaine was increased when using prophylactic infusion of phenylephrine to prevent spinal-induced hypotension. However, ED95 is more meaningful to clinical practice than ED50. Therefore, we conducted this study to determine the 95% effective dose (ED95) of intrathecal hyperbaric ropivacaine for cesarean section in parturients receiving prophylactic infusion of phenylephrine to prevent spinal-induced hypotension.

METHODS

A hundred of healthy parturients undergoing elective cesarean section under combined spinal-epidural anesthesia (CSEA) were enrolled in this randomized, double-blinded, dose-ranging study. Patients were randomly assigned to receive 7, 9, 11, 13 or 15 mg intrathecal hyperbaric ropivacaine respectively. The prophylactic phenylephrine infusion (50 μg/min) was initiated immediately at the same time of spinal injection. Successful spinal anesthesia was defined as a T5 sensory level achieved within 10 min after intrathecal drug administration and no epidural supplement was required during the surgery. The ED95 was calculated with Probit analysis.

RESULTS

The ED95 of intrathecal ropivacaine with 5 μg sufentanil for successful anesthesia was 15.2 mg (95%CI, 13.5-18.8 mg), when receiving prophylactic infusion of phenylephrine.

CONCLUSION

Under the conditions of the present study, the ED95 of intrathecal hyperbaric ropivacaine for successful spinal anesthesia for cesarean section in healthy parturient receiving prophylactic infusion of phenylephrine was 15.2 mg.

The dose response of sufentanil as an adjuvant to ropivacaine in cesarean section for relief from somato-visceral pain under epidural anesthesia in parturients with scarred uterus

Visceral pain is common during epidural anesthesia with mini dose local anesthetics in parturients during cesarean section. To reduce or avoid this complication caused by traction on the abdominal viscera, this study aimed to determine the 50% effective dose (ED50) and 95% effective dose (ED95) of epidural sufentanil as an adjuvant combination with local anesthetics for relief visceral pain in parturients with scarred uterus undergoing elective cesarean section.One hundred parturients with scarred uterus undergoing elective cesarean section under epidural anesthesia were enrolled in this randomized, double-blinded, dose-ranging study. Parturients received 5, 10, 15, 20, and 25 μg epidural sufentanil as an adjuvant with 10 mL of 0.65% ropivacaine. Successful epidural anesthesia was defined as a sixth thoracic vertebra (T6) sensory level achieved within 20 minutes after epidural drugs administration and/or no visceral pain by traction on the abdominal viscera during the cesarean section. The ED50 and ED95 were calculated with a logistic regression model.ED50 and ED95 of epidural sufentanil for successful of the pain-free from visceral pain were 10.7 μg [95% confidence interval (CI): 2.4-14.4 μg) and 28.1 μg (95% CI: 19.4-44.0 μg), respectively. The onset time to sensory block, maximum Bromage scale and duration of motor block were significant different with dose of sufentanil >20 μg (P < .05, compared with the other dose groups). With the dose of epidural sufentanil >20 μg could result in an increase of incidence of maternals' adverse effects. Compared with a different dose of sufentanil, epidural administed sufentanil between 15 μg and 20 μg can maximize parturients' satisfaction.Our study showed that sufentanil could be used in combination with ropivacaine for relief from somato-visceral pain in patients with scarred uterus during elective cesarean section during epidural anesthesia, and that maximized parturients' satisfaction could be achieved when the use of sufentanil with the dose between 15 μg and 20 μg for epidural anesthesia.

Effect of Glucose Containing Crystalloid Infusion on Maternal Hemodynamic Status After Spinal Anesthesia for Cesarean Section

Background

Despite preventive strategies, hypotension is the most common complication of spinal anesthesia in cesarean section.

Objectives

The aim of this study was to assess the effect of glucose-containing crystalloid infusion on maternal hemodynamic status after spinal anesthesia for cesarean section.

Methods

In this prospective, randomized, double-blind clinical trial, 80 parturients undergoing elective cesarean section with spinal anesthesia were studied. In group A (n = 40) ringer with 1% glucose solution (10 gr glucose in 1000 mL ringer) and in group B (n = 40) only ringer solution infused before and after spinal anesthesia. Demographic data, hemodynamic change, complications and their treatments, maternal blood sugar level and neonatal APGAR (appearance, pulse, grimace, activity and respiration) score, intraoperative fluid, duration of surgery, and anesthesia were recorded in the two groups.

Results

The incidence of hypotension in group A was significantly lower than group B (27.5% vs 75%) (P = 0.002). Other complications (sustained hypotension, nausea, pallor, and shivering were significantly lower in parturients of the group A (P < 0.05). Maternal blood sugar (BS), before and after surgery, was not significantly different in the two groups (P = 0.207 and P = 0.239, respectively). There was no statistically significant difference in the APGAR score of neonates at the 1st and 5th minutes of the birth between the two groups (P = 0.076).

Conclusions

It seems that adding 1% glucose to crystalloid solution improves the hemodynamic status and decreases post-spinal anesthesia complications without significant changes in the maternal blood sugar level and APGAR score of neonates.

Crystalloid Coload Reduced the Incidence of Hypotension in Spinal Anesthesia for Cesarean Delivery, When Compared to Crystalloid Preload: A Meta-Analysis

Objective

To determine whether crystalloid infusion just after intrathecal injection (coload) would be better than infusion before anesthesia (preload) for hypotension prophylaxis in spinal anesthesia for cesarean delivery.

Methods

We searched PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and other databases for randomized controlled trials comparing coload of crystalloid with preload in parturients receiving spinal anesthesia for cesarean delivery. Primary outcome was intraoperative incidence of hypotension. Other outcomes were intraoperative need for vasopressors, hemodynamic variables, neonatal outcomes (umbilical artery pH and Apgar scores), and the incidence of maternal nausea and vomiting. We used RevMan 5.2 and STATA 12.0 for the data analyses.

Results

Ten studies with 824 cases were included. The incidence of hypotension was significantly higher in the preload group compared with the coload group (57.8% versus 47.1%, odds ratio [OR] = 1.62, 95% confidence interval [CI] = 1.11–2.37, and P = 0.01). More patients needed intraoperative vasopressors (OR = 1.71, 95% CI = 1.07–2.04, and P = 0.02) when receiving crystalloid preload. In addition, the incidence of nausea and vomiting was higher in the preload group (OR = 3.40, 95% CI = 1.88–6.16, and P < 0.0001). There were no differences in neonatal outcomes between the groups.

Conclusions

For parturients receiving crystalloid loading in spinal anesthesia for cesarean delivery, coload strategy is superior to preload for the prevention of maternal hypotension.

Peri-operative management of caesarean section for the occasional obstetric anaesthetist – an aide memoire

Anaesthesia practice for caesarean section (CS) has evolved in the past 20 years. This article aims to update occasional obstetric anaesthesiologists, obstetricians and clinicians involved in the management of pregnant women on the latest guidelines and recommendations for anaesthesia management, including pre-operative evaluation, informed consent, intra-operative and postoperative management for CS. In addition, this article will also summarise the management of CS associated emergencies such as difficult intubation, obstetric major postpartum haemorrhage, local anaesthetic toxicity and (pre-) eclampsia. At the end of the article, a charted summary will be provided as an aide memoire.

Comparison of Phenylephrine and Ephedrine in Treatment of Spinal-Induced Hypotension in High-Risk Pregnancies: A Narrative Review

Purpose

To compare maternal and fetal effects of intravenous phenylephrine and ephedrine administration during spinal anesthesia for cesarean delivery in high-risk pregnancies.

Source

An extensive literature search was conducted using the US National Library of Medicine, MEDLINE search engine, Cochrane review, and Google Scholar using search terms “ephedrine and phenylephrine,” “preterm and term and spinal hypotension,” “preeclampsia and healthy parturients,” or “multiple and singleton gestation and vasopressor.” Society of Obstetric Anesthesia and Perinatology meeting abstracts for the past 4 years were also searched for relevant studies.

Principle findings

Both phenylephrine and ephedrine can be safely used to counteract hypotension after spinal anesthesia in patients with uteroplacental insufficiency, pregnancy-induced hypertension, and in non-elective cesarean deliveries. Vasopressor requirements before delivery in high-risk cesarean sections are reduced compared to healthy parturients. Among the articles reviewed, there were no statistically significant differences in umbilical arterial pH, umbilical venous pH, incidence of fetal acidosis, Apgar scores, or maternal hypotension when comparing maternal phenylephrine and ephedrine use.

Conclusion

From the limited existing data, phenylephrine and ephedrine are both appropriate selections for treating or preventing hypotension induced by neuraxial blockade in high-risk pregnancies. There is no clear evidence that either medication is more effective at maintaining maternal blood pressure or has a superior safety profile in this setting. Further investigations are required to determine the efficacy, ideal dosing regimens, and overall safety of phenylephrine and ephedrine administration in high-risk obstetric patients, especially in the presence uteroplacental insufficiency.

Sufentanil and Bupivacaine Combination versus Bupivacaine Alone for Spinal Anesthesia during Cesarean Delivery: A Meta-Analysis of Randomized Trials

Objective

The addition of lipophilic opioids to local anesthetics for spinal anesthesia has become a widely used strategy for cesarean anesthesia. A meta-analysis to quantify the benefits and risks of combining sufentanil with bupivacaine for patients undergoing cesarean delivery was conducted.

Methods

A comprehensive literature search without language or date limitation was performed to identify clinical trials that compared the addition of sufentanil to bupivacaine with bupivacaine alone for spinal anesthesia in healthy parturients choosing cesarean delivery. The Q and I² tests were used to assess heterogeneity of the data. Data from each trial were combined using relative ratios (RRs) for dichotomous data or weighted mean differences (WMDs) for continuous data and corresponding 95% confidence intervals (95% CIs) for each trial. Sensitivity analysis was conducted by removing one study a time to assess the quality and consistency of the results. Begg’s funnel plots and Egger’s linear regression test were used to detect any publication bias.

Results

This study included 9 trials containing 578 patients in the final meta-analysis. Sufentanil addition provided a better analgesia quality with less breakthrough pain during surgery than bupivacaine alone (RR = 0.10, 95% CI 0.06 to 0.18, P < 0.001). Sensory block onset time was shorter and first analgesic request time was longer in sufentanil added group compared with the bupivacaine-alone group (WMD = −1.0 min, 95% CI −1.5 to −0.58, P < 0.001 and WMD = 133 min, 95% CI 75 to 213, P < 192, respectively). There was no significant difference in the risk of hypotension and vomiting between these two groups. But pruritus was more frequentely reported in the group with sufentanil added (RR = 7.63, 95% CI 3.85 to 15.12, P < 0.001).

Conclusion

Bupivacaine and sufentanil combination is superior to that of bupivacaine alone for spinal anesthesia for cesarean delivery in analgesia quality. Women receiving the combined two drugs had less breakthrough pain, shorter sensory block onset time, and longer first analgesic request time. However, the addition of sufentanil to bupivacaine increased the incidence of pruritus.

Ephedrine versus ondansetron in the prevention of hypotension during cesarean delivery: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Maternal hypotension is common after spinal anesthesia for cesarean delivery. We compared the effects of prophylactic ephedrine with ondansetron on post-spinal blood pressure.

METHODS

One hundred and sixty-eight term, singleton parturients were enrolled in this prospective, double-blind, placebo-controlled trial. Patients were randomized to receive either prophylactic intravenous ephedrine 10mg (Group E), ondansetron 8mg (Group O) or normal saline (Group P) immediately after spinal anesthesia. The primary outcome was maternal blood pressure between spinal block and delivery; secondary outcomes were nausea and vomiting scores, Apgar scores, numbers requiring intraoperative vasoconstrictors and the dose of vasoconstrictors required.

RESULTS

Fifty-six patients were recruited to each group, but two in Group P were excluded from the analysis owing to protocol violations. There were no significant differences between the groups in maternal systolic, diastolic or mean arterial pressures, or the proportion of patients experiencing hypotension. The proportion of patients in Group E requiring intraoperative ephedrine or any vasoconstrictor (ephedrine and/or norepinephrine) was significantly lower than that in Group P (P=0.023 and 0.034, respectively). The proportion of patients in Group O requiring intraoperative norepinephrine was significantly lower than that in Group P (P=0.02). There was no difference in the proportions of patients in Groups E and O requiring any vasoconstrictors (P=0.34).

CONCLUSIONS

There was no significant difference in maternal blood pressure in women administered prophylactic ephedrine or ondansetron after spinal anesthesia for cesarean delivery compared with placebo. Ephedrine reduced the proportion of patients requiring a rescue vasoconstrictor before delivery.

Randomized double-blind comparison of ephedrine and phenylephrine for management of post-spinal hypotension in potential fetal compromise

BACKGROUND

Most studies comparing phenylephrine and ephedrine have been conducted during elective caesarean sections in healthy mothers with no fetal compromise. The effect of vasopressors on fetal outcome may differ between healthy and compromised fetuses. There has been little research into the effect of phenylephrine and ephedrine, when used for management of post-spinal hypotension in the presence of potential fetal compromise.

METHODS

Healthy women with a singleton pregnancy undergoing emergency caesarean section for fetal compromise under spinal anaesthesia were studied. One-hundred-and-six consecutive subjects, who developed hypotension after spinal anaesthesia, were randomly allocated to two groups of 53 each, to receive either phenylephrine (Group P) or ephedrine (Group E). For every systolic blood pressure reading <100mmHg patients received phenylephrine 100μg or ephedrine 8mg depending on group allocation. Umbilical blood gas parameters and Apgar scores were recorded.

RESULTS

There was no statistically significant difference in umbilical arterial pH (P=0.79), umbilical venous pH (P=0.98), other blood gas parameters, incidence of fetal acidosis (P=1.00) and Apgar scores. The number of hypotensive episodes, vasopressor doses for treatment of the first hypotensive episode and the total number of doses used during the study period were comparable. The median [IQR] total number of doses of phenylephrine and ephedrine used before delivery were 2 [1-2] and 2 [1-2], respectively (P=0.67). More patients receiving ephedrine (24.5%) developed tachycardia than those receiving phenylephrine (3.8%) (P=0.004). Bradycardia was more common with phenylephrine, with 39.6% of patients in Group P as compared to only 1.9% of patients in Group E developing a heart rate <60beats/min after vasopressor administration (P=0.001).

CONCLUSIONS

Both phenylephrine 100μg and ephedrine 8mg boluses are equally efficacious when treating post-spinal hypotension in the presence of potential fetal compromise. However, phenylephrine may be a better choice in the presence of maternal tachycardia.

Evaluation of antihypotensive techniques for cesarean section under spinal anesthesia: Rapid crystalloid hydration versus intravenous ephedrine

Background:

Spinal anesthesia is a preferred technique over general anesthesia for cesarean delivery. It avoids maternal airway related complications, aspiration and neonatal depression. However hypotension following spinal anesthesia can lead to decrease in uterine blood flow and neonatal hypoxia.

Aims:

We aimed to evaluate the efficacy of 15 mL.kg- 1of crystalloid preloading versus prophylactic intravenous bolus of 10 mg ephedrine as an antihypotensive measure for cesarean section.

Methods:

A prospective randomized double blind study was conducted in hundred ASA grade I/II parturient undergoing cesarean section, allocated to group P (n=50) who received preloading with ringer lactate 15 mL.kg- 1 over 20 minutes before spinal anesthesia and group E (n=50) received intravenous bolus of 10mg ephedrine within one minute of spinal anesthesia with 10mg of hyperbaric bupivacaine 0.5% at L2-3/L3-4 level. They were monitored for incidences of hypotension, need of rescue doses of ephedrine, Apgar score and adverse events. Appropriate statistical tests were applied and P < 0.05 was considered as significant.

Results:

Incidence of hypotension within 20 minutes of spinal anesthesia was significantly less in group E (28%) as compared to group P (58%) and need of rescue doses were more in group P. Adverse events like nausea vomiting and shivering were less in group E. Apgar score were better in group E than in group P delivered babies.

Conclusion:

Prophylactic intravenous bolus of 10mg ephedrine with spinal injection is more effective in maintaining maternal hemodynamic stability and better neonatal outcome as compared to crystalloid preloading during cesarean delivery.

Comparison of the effects of colloid preload, vasopressor administration and leg compression on hemodynamic changes during spinal anesthesia for lumbar disc surgery in knee-chest position

BACKGROUND

Hypotension is a serious and the most common adverse effect of spinal anesthesia. Many studies have focused on prevention of hypotension due to spinal anesthesia. The aim of this study was to compare the efficacy of three different methods of using colloid, ephedrine and wrapping of extremities on the incidence of hypotension and bradycardia following spinal anesthesia in patients undergoing elective lumbar disc surgery in knee-chest position.

MATERIALS AND METHODS

A total of 180, ASA (I-II), adult patients candidate of lumbar disc surgery in one or two levels who met the inclusion criteria were randomly allocated in one of three treatment groups of receiving Voluven (6% hydroxyethyl starch 130/0.4 in 0.9% sodium chloride injection), ephedrine and leg wrapping. After establishment of spinal anesthesia, patients were outsourced and knee-chest position was done. Heart rate and blood pressure of patients were recorded at different times till 60 min after spinal injection. Statistical analyses of data were performed with SPSS (version 20) and by considering groups, values of P < 0.05 were considered statistically significant.

RESULTS

Mean systolic blood pressure (119.5 ± 7.4 mmHg) and mean heart rate (71.7 ± 6.7 b/min) were higher in a group receiving Voluven (P < 0.05). The Voluven group significantly experienced less nausea and vomiting in recovery room in comparing with other groups (P = 0.027). They also received significantly less ephedrine (P = 0.012) and ondansetron [12 (20%)] (P = 0.02). Furthermore, patients receiving elastic bandage had significantly more blood loss than the other groups (P = 0.013).

CONCLUSION

Colloid therapy was the most effective method in keeping hemodynamic stability, prevention of decrease in systolic blood pressure and incidence of side effects during spinal anesthesia for lumbar disc surgery in knee-chest position.

Comparison of maternal and fetal outcomes among patients undergoing cesarean section under general and spinal anesthesia: a randomized clinical trial

CONTEXT AND OBJECTIVE

As the rates of cesarean births have increased, the type of cesarean anesthesia has gained importance. Here, we aimed to compare the effects of general and spinal anesthesia on maternal and fetal outcomes in term singleton cases undergoing elective cesarean section.

DESIGN AND SETTING

Prospective randomized controlled clinical trial in a tertiary-level public hospital.

METHODS

Our study was conducted on 100 patients who underwent cesarean section due to elective indications. The patients were randomly divided into general anesthesia (n = 50) and spinal anesthesia (n = 50) groups. The maternal pre and postoperative hematological results, intra and postoperative hemodynamic parameters and perinatal results were compared between the groups.

RESULTS

Mean bowel sounds (P = 0.036) and gas discharge time (P = 0.049) were significantly greater and 24th hour hemoglobin difference values (P = 0.001) were higher in the general anesthesia group. The mean hematocrit and hemoglobin values at the 24th hour (P = 0.004 and P < 0.001, respectively), urine volume at the first postoperative hour (P < 0.001) and median Apgar score at the first minute (P < 0.0005) were significantly higher, and the time that elapsed until the first requirement for analgesia was significantly longer (P = 0.042), in the spinal anesthesia group.

CONCLUSION

In elective cases, spinal anesthesia is superior to general anesthesia in terms of postoperative comfort. In pregnancies with a risk of fetal distress, it would be appropriate to prefer spinal anesthesia by taking the first minute Apgar score into account.

Low baseline proBNP associated with increased risk of intraoperative hypotension during spinal anaesthesia for cesarean delivery

BACKGROUND AND OBJECTIVES

Brain natriuretic peptide (BNP) has a role in the regulation of body fluid volume and blood pressure (BP). BNP remains within a normal range during spinal anaesthesia (SA) in patients undergoing cesarean delivery. However, the effect of BNP on changes in BP during the perioperative period has not been evaluated. We aimed to investigate the effect of preoperative serum BNP on the risk of hypotension during cesarean delivery with SA.

DESIGN AND SETTINGS

Patients were randomly selected among the patient group who were attending routine clinic visits for pregnancy monitoring. All had a healthy pregnancy and no other acute or chronic disease by their obstetrician. The study design was cross-sectional.

PATIENTS AND METHODS

Patients who had uncomplicated pregnancy process and no known medical dis.ease were selected consecutively during their last outpatient clinical examination. Baseline BP was recorded before SA. Simultaneously, blood samples were drawn for routine biochemistry and BNP. BP, SaO2, and electrocardiography were monitored during surgery. Intraoperative hypotension (IOH) was defined as >=25% decrease in mean arterial pressure (MAP) at the 5th minute of SA.

RESULTS

In 41 term pregnant women, 18 of the 41 patients (43.9%) fulfilled the criteria for IOH, while 23 (56.1%) showed a decrease 13.1 (11.3%) and were classified as normotensive. Baseline BNP was significantly lower in patients with IOH compared with normotensive patients 45.7 (26.9) vs.70.2 (40.5); P=.05. Baseline BNP had no significant correlation MAP at any time point. Age, body mass index, hemoglobin, baseline MAP and heart rate were not different between patients with and without IOH.

CONCLUSION

Those findings suggest that higher baseline BNP levels might have a protective role in development of hypotension in healthy term pregnant women during SA for cesarean delivery.

Co-loading or pre-loading for prevention of hypotension after spinal anaesthesia! a therapeutic dilemma

Neuraxial blockade such as spinal anaesthesia can cause severe hypotension due to pharmacological sympathectomy resulting in potential deleterious consequences for the patient. Prevention of this spinal anaesthesia induced hypotension is of utmost importance especially in pregnant population as the life of mother as well as fetus is at risk. Several techniques and methodologies have been adopted for the prevention of this neuraxial hypotension with varying degree of success. The administration of intravenous fluids to optimize the blood volume during sympathectomy has been the most popular and widely used as the first line of therapy among these techniques. The intravenous fluids can be used both before and during the administration of spinal anaesthesia, the techniques appropriately named as pre-loading and co-loading respectively. Numerous research studies and available literary evidence suggests that both of these techniques can be equally effective in prevention of hypotension. The use of colloids has been observed to be more effective for pre-loading due to their longer half-life in the intravascular compartment. However, it has also been suggested that no technique is efficient in preventing the hypotension alone and has to be coupled with judicious use of vasopressors.

Effect of different phenylephrine bolus doses for treatment of hypotension during spinal anaesthesia in patients undergoing elective caesarean section

The efficacy of phenylephrine might be improved by giving doses higher than that traditionally used (100 µg). This study compared the effects of three initial bolus doses of intravenous phenylephrine; 100 µg (group P100), 125 µg (group P125) and 150 µg (group P150), for the treatment of post-spinal hypotension in patients undergoing elective caesarean delivery. If hypotension was not corrected by this dose, additional boluses of 25 µg were given every minute. Further hypotensive episodes were treated with half the initial bolus dose, followed by 25 µg boluses, as required. Umbilical arterial and venous blood samples were obtained for blood gas analysis and Apgar scores recorded. One hundred and twenty subjects (40 per group) who developed post-spinal hypotension (75%) were included in this randomised, double blind trial. Although systolic blood pressure was higher at certain time-points after 150 µg phenylephrine, there were no statistically significant differences in the effectiveness of the first bolus of phenylephrine to treat hypotension (85%, 95% and 95% in groups P100, P125 and P150, respectively, P=0.215); the additional dose of phenylephrine after the first bolus (P=0.810); the number of additional boluses (P=0.318) or of hypotensive episodes (P=0.118). There were no significant differences in the number of patients developing reactive hypertension or bradycardia, in maternal side-effects or in neonatal outcomes. Although the study may have been underpowered, initial phenylephrine bolus doses of 100 µg, 125 µg and 150 µg did not significantly differ in efficacy to treat post-spinal hypotension in these patients.

Vasopressors in obstetric anesthesia: A current perspective

Vasopressors are routinely used to counteract hypotension after neuraxial anesthesia in Obstetrics. The understanding of the mechanism of hypotension and the choice of vasopressor has evolved over the years to a point where phenylephrine has become the preferred vasopressor. Due to the absence of definitive evidence showing absolute clinical benefit of one over the other, especially in emergency and high-risk Cesarean sections, our choice of phenylephrine over the other vasopressors like mephentermine, metaraminol, and ephedrine is guided by indirect evidence on fetal acid-base status. This review article evaluates the present day evidence on the various vasopressors used in obstetric anesthesia today.