European Journal of Cardiovascular Medicine

The first priority to be considered during planning of anaesthesia for Caesarean section is maternal and foetal well-being. Generally regional anaesthesia (RA) is more commonly used technique than general anaesthesia (GA) because mother is awake and can hear the cry of her baby and interact immediately

The choice of anaesthesia for a Caesarean section depends on several factors, including the urgency of the procedure, the underlying reason for the operation, the mother’s preferences and any existing medical conditions. General anaesthesia may be indicated in various situations such as when regional anaesthesia fails, when regional techniques are contraindicated, when requested by the mother or in cases of severe foetal distress where there isn’t enough time to administer a regional anesthetisia.¹

Postpartum haemorrhage (PPH) remains one of the leading causes of maternal morbidity and mortality worldwide with uterine atony being identified as the primary cause in approximately 50% of all cases². Uterine atony refers to the failure of the uterus to contract effectively after childbirth resulting in excessive bleeding. The most common interventions to prevent and manage PPH include the administration of uterotonic agents which stimulate uterine contractions and help to control bleeding. Among these agents’ oxytocin is the most widely used and considered the gold standard for prophylaxis and treatment of PPH.³

Oxytocin remains a cornerstone of PPH prevention due to its proven effectiveness in promoting uterine contractions and reducing bleeding. However, healthcare providers must be vigilant in monitoring for and managing potential side effects particularly hypotension and reflex tachycardia, to ensure the safety and well-being of the mother following childbirth.³

Phenylephrine is a directly acting α-1 adrenergic agonist and is considered the first-line vasopressor for managing maternal hypotension, particularly during spinal anaesthesia in parturient⁴. Its rapid onset of action with peak effects typically seen within one minute, helps maintain mean arterial pressure (MAP) and ensures adequate uteroplacental blood flow—both of which are critical for the health of the mother and foetus during procedures like caesarean sections.⁵

One of the primary advantages of phenylephrine over other vasopressors is that it does not cause foetal acidosis making it safer for the foetus ⁶. Additionally, it helps to avoid tachycardia a common side effect with other vasopressors like ephedrine, by inducing a baroreceptor-mediated reflex bradycardia. This reflex slows the heart rate and reduces cardiac output which can be beneficial when tachycardia is undesirable particularly in patients with cardiac concerns.⁵

In practice phenylephrine is often administered in titrated doses alongside oxytocin, a uterotonic agent used to prevent postpartum haemorrhage. Oxytocin, while effective, can lead to hypotension and reflex tachycardia and phenylephrine helps mitigate these effects ensuring stable maternal hemodynamic during labour and delivery. This combination makes phenylephrine a valuable tool in obstetric anaesthesia offering both safety and efficacy for managing maternal blood pressure.⁵

There is limited research on the minimum effective dose of phenylephrine necessary for co-administration with oxytocin to counteract the cardiovascular effects of oxytocin.

Therefore, the objective of the current study was to compare two different doses of phenylephrine to determine the most effective dose for preventing adverse hemodynamic changes caused by oxytocin in parturient undergoing a Caesarean section under spinal anaesthesia.

This prospective study was done with evaluation of patients undergoing LSCS referred to Rohilkhand Medical College and Hospital, Bareilly (U.P.) The study was done for one year from 1^stAugust, 2023 to 31^stJuly, 2024 taking into account of total 64 patients coming for LSCS. Our study was done with approval from Institutional Ethical Committee.

Inclusion Criteria:

• Patients who give informed consent.
• ASA Grade II 
• Age group 20- 40yrs

Exclusion Criteria:

• ASA Grade III or IV
• Patients with obstetrical complications like: -
• antepartum haemorrhage
• pregnancy induced hypertension
• cord complications (nuchal cord or cord prolapse)
• foetal malformations
• Polyhydramnios
• Any contraindication to spinal anaesthesia presents in patient.

Sample Size: In our study a total of 32 patients were taken in each group, which is statistically calculated by using the software Power and sample size program⁷.

A sum total of 64 adult females in age ranged 20- 40 years with elective and emergency lower segment caesarean section were recruited for this randomized prospective study. Institutional Ethics Committee approval and informed consent was taken prior to conducting this study.

Procedure: Thorough pre-anaesthetic check-up was done prior to surgery and after carefully explaining the procedure informed and written consent was obtained.

Patients were randomly divided into two groups using a computer-generated randomization approach.

Pre-anaesthetic preparation and premedication: For patients undergoing LSCS, before having surgery, the patients were kept nil per oral as per ASA Guidelines. The night before the procedure and coming morning, a tablet of ranitidine 150 mg was given orally with sip of water.

Anaesthetic technique: On day of surgery IV access was secured in and patient was preloaded with Intravenous Ringer lactate solution at 10 ml/kg and vitals monitors were attached. Under all aseptic precautions spinal anaesthesia was administered with a 25G Quincke's Needle at L3-L4 intervertebral space in sitting position. After CSF confirmation a dose of 2ml of Hyperbaric Inj. Bupivacaine was given.

The patients were divided into two groups using a computer-generated program. In Group 1, patients received a combination of 5 IU of oxytocin and 50 mcg of phenylephrine, each diluted to 10 cc with normal saline and administered over 1 minute. In Group 2, patients were given 5 IU of oxytocin and 75 mcg of phenylephrine, also diluted to 10 cc and delivered over 1 minute.

At 2,4,6,8 and10 minutes after the administration of Oxytocin and co-administration of Phenylephrine, heart rate, systolic, diastolic, mean blood pressure and oxygen saturation were recorded. Also, the patient was observed for any adverse effects like hypertension, bradycardia, nausea and vomiting.

Bradycardia is defined as heart rate that is below 50 beats per minute in adults. If persistent bradycardia was seen then Inj. Atropine 0.6mg IV was given

Hypertension is defined as having a 20% increase from

If an incidence of Nausea or Vomiting occurs then, Inj. Ondansetron 4mg IV was given.

Out of a total of 64 participants, 32 were assigned to Group 1, representing 50% of the participants and 32 were assigned to Group 2, also making up 50% of the total.

In Group 1, 81.25% (26 out of 32) of participants were aged 20-30 years, while 18.75% (6 out of 32) were in the 30-40-year age range. For Group 2, 78.13% (25 out of 32) were in the 20-30-year age group, and 21.88% (7 out of 32) were aged 30-40 years. The p-value of 0.756 suggests there is no significant difference in age distribution between the two groups, as the p-value is greater than 0.05. A Chi-square test was used to analyse this data.

In both the Group 1 and Group 2, all 32 participants were female, which accounts for 100% of the participants in each group. No p-value is provided here since the groups are homogeneous in terms of gender.

Table 1: ASA Grade Distribution by Group

signifies significant p value<0.05

Both Group 1 and Group 2 consist entirely of participants classified as ASA Grade II, with 100% in each group. The absence of a p-value indicates no variability between the groups in terms of ASA grade.

Table 2: Age and Weight Comparison Between Groups

The mean age of participants in the Group 1 is 27.31 ± 4.01 years, while in the Group 2, the mean age is 27.75 ± 4.84 years. The p-value of 0.695 indicates no significant difference in age between the two groups, as the value is greater than 0.05. Regarding weight, the mean weight in Group 1 is 62.28 ± 10.05 kg, while Group 2 has a mean weight of 66.56 ± 8.54 kg. The p-value of 0.071 suggests a trend toward a difference, though it is not statistically significant as it is greater than 0.05. The data were analysed using a student’s t-test.

Table 3: Heart Rate Comparison Between Groups at Various Time Points

Test used: Student's t test

*Signifies significant p value<0.05

This table presents the comparison of heart rate (measured in beats per minute, bpm) between Group 1 and Group 2 at various time points. At pre-op, the heart rate in Group 1 was 86.38 ± 9.35 bpm, while in Group 2, it was 84.72 ± 6.82 bpm, with a p-value of 0.421, indicating no significant difference. Similarly, no significant differences were observed in measurements after taking patient inside operation theatre, before and after the subarachnoid block (SAB), before cord clamping and at the time of cord clamping, as the p-values for all time points were greater than 0.05. However, at later time points, including 2 minutes, 4 minutes, 6 minutes, 8 minutes, and 10 minutes after cord clamping, the heart rate in Group 1 was significantly higher compared to Group 2, with p-values ranging from 0.028 to 0.001, indicating statistically significant differences. These differences suggest a more pronounced heart rate increase in Group 1 over time. The data were analysed using a student’s t-test, and values with a p-value less than 0.05 are considered statistically significant.

Table 4: Systolic Blood Pressure (SBP) Comparison Between Groups

Test used: Student's t test 

This table compares the systolic blood pressure (SBP) of participants in the Group 1 and Group 2 at various time points. At pre-op, the mean SBP for Group 1 was 122.31 ± 15.23 mm Hg, while Group 2 had a mean of 120.19 ± 12.85 mm Hg, with a p-value of 0.548, indicating no significant difference between the groups. Similarly, no significant differences were found at other time points such as after taking patient inside operation theatre, before SAB, during the first 8 minutes after SAB, just before cord clamping and during cord clamping. However, from 2 minutes post-cord clamping onward, Group 2 showed higher SBP values compared to the Group 1, with p-values ranging from 0.019 to <0.001, indicating a statistically significant or highly significant difference at these later time points. These results suggest that Group 2 tends to maintain higher SBP values compared to Group 1. A Student’s t-test was used to analyse the data, and values with p < 0.05 are considered statistically significant, while p < 0.001 is considered highly significant.

Table 5: Diastolic Blood Pressure (DBP) Comparison Between Groups

Test used: Student's t test

This table presents the comparison of diastolic blood pressure (DBP) between Group 1 and Group 2 at various time points. At pre-op, the mean DBP for Group 1 was 79.56 ± 6.77 mm Hg, and for Group 2, it was 78.88 ± 6.07 mm Hg, with a p-value of 0.670, indicating no significant difference between the groups. The comparison remains non-significant at other time points such as after taking patient inside operation theatre, before SAB, during the first 8 minutes after SAB, just before cord clamping and at the time of cord clamping. However, from 2 minutes after cord clamping onward Group 2 consistently showed higher DBP values than Group 1. These differences became significant at 2,4, 6-, 8-, and 10-minutes post cord clamping, with p-values ranging from <0.001 to 0.020. These findings suggest that Group 2 may lead to a more sustained increase in DBP compared to Group 1. The data were analysed using a student’s t-test, with p-values less than 0.05 indicating statistical significance and p-values less than 0.001 indicating highly significant differences.

Table 6: Mean Arterial Pressure (MAP) Comparison Between Groups

Test used: Student's t test

This table compares the mean arterial pressure (MAP) between Group 1 and Group 2 at various time points. In pre-op, the MAP for Group 1 was 67.29 ± 6.30 mm Hg and for Group 2 was 66.35 ± 5.48 mm Hg, with no significant difference (p = 0.528). No significant differences were observed at other time points such as after taking patient inside operation theatre, before SAB, during the first 8 minutes after SAB, just before cord clamping and at the time of cord clamping. However, significant differences began to emerge starting from 2 minutes after cord clamping, where Group 2 showed a higher MAP than Group 1(p = 0.010). The differences continued to be significant at 2,4, 6-, 8-, and 10-minutes post cord clamping with p-values ranging from 0.002 to 0.003, indicating a progressively higher MAP in Group 2. These findings suggest that Group 2 has a more sustained effect on increasing MAP compared to Group 1. A Student’s t-test was used, with p-values <0.05 considered significant and p-values <0.001 considered highly significant.

Table 7: Oxygen Saturation (SpO2) Comparison Between Groups

This table presents the comparison of oxygen saturation (SpO2) between the Group1 and Group 2 at various time points. In pre-op, the mean SpO2 for Group1 was 97.94 ± 0.95%, and for Group 2, it was 98.31 ± 1.12%, with no significant difference (p = 0.153). Similarly, no significant differences were observed in intraoperative, pre-SAB, or post-SAB SpO2 levels between the two groups. The p-values for these comparisons ranged from 0.153 to 1.000, indicating that there were no significant effects of Group1 vs. Group 2 on SpO2 at any time point. The data were analysed using a Student’s t-test, and none of the comparisons showed statistically significant differences.

This study showed no adverse event i.e. hypertension, bradycardia, nausea and vomiting in either of the two groups of Phenylephrine at 50mcg and 75mcg. This suggests that the drug was safe and well tolerated. The absence of adverse effects in this study could be attributed to factors such as low sample size, demographic variance and study techniques employed. Larger sample sizes, broader demographic representation and refined methodologies are necessary to draw more definitive conclusions about the safety of low dosage Phenylephrine groups.

Postpartum haemorrhage (PPH) is a major cause of maternal mortality, with uterine atony responsible for approximately 50% of the cases. By using uterotonic drugs properly, it can be decreased. The most often utilised uterotonic substance is oxytocin. The risk of PPH can be decreased by up to 40% by regularly utilising oxytocin as a prophylactic measure.

However, since oxytocin interacts with oxytocin receptors in the heart and major blood vessels, it can lead to undesirable effects like hypotension and reflex tachycardia. To manage this hypotension several vasopressors including Ephedrine, Mephentermine, and Phenylephrine can be used. Among these, Phenylephrine has shown to provide faster control of blood pressure during hypotension caused by spinal anaesthesia.

Phenylephrine a fast-acting alpha agonist can be given either as a bolus or continuous infusion with adjusted doses to manage hypotension caused by oxytocin.

Phenylephrine co-administration has been found to reduce the effects of oxytocin on cardiac output, heart rate and systemic vascular resistance. At higher doses Phenylephrine can cause reflex bradycardia along with decreased cardiac output.

In our study we divided the parturient into 2 groups:

Group 1: Patients were administered oxytocin 5 IU and phenylephrine 50 mcg, both diluted to 10 cc with normal saline and given over 1 minute. 

Group 2: Patients received oxytocin 5 IU and phenylephrine 75 mcg, each diluted to 10 cc and administered over 1 minute.

Our data was compared in both groups in term of observing changes at 2,4,6,8 and 10 minutes after the administration of Oxytocin and co-administration of Phenylephrine, heart rate, systolic, diastolic, mean blood pressure and oxygen saturation were recorded.

The selection of doses was informed by several studies. The study concluded that co-administering phenylephrine 75 mcg with oxytocin 3U significantly reduced the incidence of oxytocin-induced hypotension compared to phenylephrine 50 mcg with oxytocin 3U during caesarean sections under spinal anaesthesia.

In Group 1, patients received a combination of 5 IU of oxytocin and 50 mcg of phenylephrine, each diluted to 10 cc with normal saline and administered over 1 minute. In Group 2, patients were given 5 IU of oxytocin and 75 mcg of phenylephrine, also diluted to 10 cc and delivered over 1 minute. At 2,4,6,8 and 10 minutes after the administration of Oxytocin and co-administration of Phenylephrine, heart rate, systolic, diastolic, mean blood pressure and oxygen saturation were recorded. Also, the patient was observed for any adverse effects like hypertension, bradycardia, nausea and vomiting. It was observed that Group 2 with Phenylephrine dose of 75mcg gave an overall better hemodynamic stability.

Demographic Profile:

In our study, the pregnant females undergoing caesarean section were divided into 2 groups i.e. Group 1 & Group 2 of 32 each. Age and Weight: The mean age of participants in Group 1 is 27.31 ± 4.01 years, while in Group 2, the mean age is 27.75 ± 4.84 years. p-value > 0.05 Regarding weight, the mean weight in Group 1 is 62.28 ± 10.05 kg, while Group 2 has a mean weight of 66.56 ± 8.54 kg. (p-value > 0.05). Nisha et al⁸ observed that the demographic profile including various intraoperative time inter­vals and other patient variables such as gestational age, fluid till delivery, phenylephrine dosage and time of the last dose before delivery, spinal to cord clamp interval, and base­line hemodynamic parameters were comparable in the two groups

Hemodynamic Parameters:

Heart Rate: In pre-op, the heart rate in Group 1 was 86.38 ± 9.35 bpm, while in Group 2, it was 84.72 ± 6.82 bpm, with a p-value > 0.05.  Similarly, no significant differences were observed after taking patient inside operation theatre, before SAB, during the first 8 minutes after SAB, just before cord clamping and at the time of cord clamping as the p-value > 0.05 However, at later time points including 2 minutes, 4 minutes, 6 minutes, 8 minutes, and 10 minutes after cord clamping, the heart rate in Group 1 was significantly higher compared to Group 2, with p-values ranging from 0.028 to 0.001, indicating statistically significant differences. These differences suggest a more pronounced heart rate increase in Group 1 over time. Comparing to Syed et al⁹, in his study he saw that there was increase in heart rate in placebo group and a significant reduction in HR was observed in phenylephrine group. Emmannuel et al¹⁰ found in his study that in terms of pulse rate, patients in the ephedrine group showed a slight increase in pulse rate whereas patients in the phenylephrine group showed a significant reduction in pulse rate over time.

This minor variance in percentage could be due to difference in study techniques, drug doses, sample size and demographic variation.

Systolic Blood Pressure: In pre-op, the mean SBP for Group 1 was 122.31 ± 15.23 mm Hg, while Group 2 had a mean of 120.19 ± 12.85 mm Hg, with a p-value > 0.05.  Similarly, no significant differences were found at other time points such as after taking patient inside operation theatre, before SAB, during the first 8 minutes after SAB, just before cord clamping or at the time of cord clamping. However, from 2 minutes post cord clamping onward, Group 2 showed higher SBP values compared to Group 1, with p-values ranging from 0.019 to <0.001, indicating a statistically significant or highly significant difference at these later time points. These results suggest that Phenylephrine 75mcg tends to maintain higher SBP values in the immediate post-operative period compared to Phenylephrine 50mcg.

Syed et al⁸ saw in his study that the reduction in SBP was more in placebo group -8.13±18.02 versus -0.43±8.35 mmHg in phenylephrine group. Muhammad et al¹¹, in his study found that in group-I (phenylephrine)systolic blood pressure (mmHg) decreased by value of 15.34% and31.92% with respect to baseline value.

Diastolic Blood Pressure: In pre-op, the mean DBP for Group 1 was 79.56 ± 6.77 mm Hg, and for Group 2, it was 78.88 ± 6.07 mm Hg, with a p-value > 0.05, indicating no significant difference between the groups. The comparison remains non-significant at other time points such as after taking patient inside operation theatre, before SAB, during the first 8 minutes after SAB, just before cord clamping or at the time of cord clamping. However, from 2 minutes after Cord clamping onward, Group 2 consistently showed higher DBP values than Group 1. These differences became highly significant at 2.4, 6-, 8-, and 10-minutes post cord clamping, with p-values ranging from <0.001 to 0.020. These findings suggest that Phenylephrine 75mcg may lead to a more sustained increase in DBP in the post-operative period compared to Phenylephrine 50mcg. Muhammad et al¹¹ in his study found that in group-I (phenylephrine)diastolic blood pressure (mmHg) decreased by value of 12.60% and 22.10% in group-II (placebo). Emmanuel et al¹⁰ found out in his study that the lowest and highest values of diastolic blood pressure values during the study period was seen in the ephedrine group while the phenylephrine group had lesser variation from baseline values.

Mean Arterial Pressure: In pre-op, the MAP for Group 1 was 67.29 ± 6.30 mm Hg and for Group 2 was 66.35 ± 5.48 mm Hg, with p-value > 0.05. No significant differences were observed at other time points such as after taking patient inside operation theatre, before SAB, during the first 8 minutes after SAB, just before cord clamping and at the time of cord clamping. However, significant differences began to emerge starting from 2 minutes after cord clamping, where Group 2 showed a higher MAP than Group 1(p = 0.071). The differences continued to be significant at 2,4, 6-, 8-, and 10-minutes post cord clamping, with p-values ranging from 0.002 to <0.001, indicating a progressively higher MAP in Group 2. These findings suggest that Phenylephrine 75mcg has a more sustained effect on increasing MAP during the post-operative period compared to Phenylephrine 50mcg. In a study conducted by Nisha et al¹¹., the mean arterial pressure (MAP) before oxytocin infusion was recorded as 81.2, 81.2, and 76.2 in groups I, II, and III, respectively. After oxytocin infusion, the MAP was 65.2, 74.9, and 64.9 in groups I, II, and III, with group II (the intervention group) demonstrating greater hemodynamic stability.

Oxygen Saturation (SpO2):  In pre-op, the mean SpO2 for Group 1 was 97.94 ± 0.95%, and for Group 2, it was 98.31 ± 1.12%, with p-value > 0.05. Similarly, no significant differences were observed at other time points such as after taking patient inside operation theatre, pre-SAB, or post-SAB SpO2 levels between the two groups. The p-values for these comparisons ranged from 0.153 to 1.000, indicating that there were no significant effects of Phenylephrine 50mcg vs. Phenylephrine 75mcg on SpO2 at any time point.

In both the Groups, there were no incidence of Hypertension, Bradycardia, Nausea and Vomiting. This may be attributed to the small sample size, demographic variance and study technique employed.  Both doses were effective in managing hemodynamic parameters during caesarean sections under spinal anesthesia; however, phenylephrine 75mcg exhibited greater efficacy in stabilizing blood pressure. The findings suggest that Group 2 is better suited for ensuring hemodynamic stability during the perioperative period, particularly for blood pressure control. These results provide valuable insights for anesthesiologists in tailoring intraoperative management strategies for caesarean sections under spinal anesthesia.

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