Prophylactic Effectiveness of Phenylephrine 100 mcg and Ephedrine 10 mg on the Incidence of Spinal Anesthesia Induced Hypotension in Patients Undergoing Cesarean Section

Introduction: Birth by cesarean section (C-section) has increased significantly, with a high risk of maternal hypotension due to spinal anesthesia.

Objective: This study aims to compare the prophylactic effectiveness of phenylephrine 100 mcg and ephedrine 10 mg in preventing spinal anaesthesia induced hypotension in C-section patients. With a focus on safety and reducing the incidence of fetal acidosis, the results of the study are expected to provide clinical insights that can improve the safety and quality of care for pregnant women undergoing this procedure.

Methods: This study compared the effectiveness of phenylephrine 100 mcg and ephedrine 10 mg in preventing hypotension due to spinal anesthesia in cesarean section patients in four hospitals in Medan, Indonesia. Using a double-blind design, 40 patients aged 18-40 years were randomly selected, and blood pressure and heart rate were measured before and after anesthesia. Data were analyzed using SPSS, and ethical aspects were taken care of through informed consent.

Results: This study found that phenylephrine 100 mcg was more effective than ephedrine 10 mg in preventing spinal anaesthesia induced hypotension in cesarean section, with more stable blood pressure and mean arterial pressure (MAP) at the 5th, 10th, and 15th minutes (p-value < 0.05). Although ephedrine remained above 100 mmHg for systolic blood pressure (SBP), the incidence of nausea and vomiting was slightly higher in the ephedrine group. Results support phenylephrine as the primary choice for hypotensive management.

Conclusion: Phenylephrine 100 mcg is more effective than ephedrine 10 mg in preventing hypotension due to spinal anesthesia, without increasing heart rate. Despite causing nausea, ephedrine has a higher incidence of vomiting. Ephedrine is recommended if phenylephrine is not available, with further studies needed for lower doses of phenylephrine.

INTRODUCTION

Births by cesarean section (C-section) have seen a significant increase in recent decades. In England and Wales, data from the National Sentinel Caesarean Audit shows that C-section rates increased from 4% in the early 1960s to 21% in 2001, accounting for 32,222 births out of a total of 150,139 deliveries (¹). The Indonesian Basic Health Research (Riset Kesehatan Dasar/RISKESDAS) 2018 recorded that the C-section delivery rate was 17.6%, with North Sumatra province recording the highest rate at 23.9% (²).

The safety of anesthesia for C-sections has improved considerably, with a decrease in anesthesia-related maternal mortality. However, the incidence of hypotension remains a significant problem, with the incidence reaching 25-75% in patients undergoing spinal anesthesia, and approximately 60-70% in C-section patients (³,⁴). Maternal hypotension can affect uteroplacental perfusion, potentially leading to serious complications such as fetal asphyxia and impaired acid-base status (⁴,⁵).

Spinal anesthesia is the primary choice for C-section, but side effects such as hypotension need to be well managed. Various approaches have been considered to prevent this problem, including intravenous fluid administration and the use of vasopressors. Ephedrine and phenylephrine are two commonly used vasopressors, each with a different mechanism of action and side effect profile (⁴,⁶). Phenylephrine, in particular, shows better potential in reducing the incidence of foetal acidosis compared to ephedrine, thus, it is increasingly recommended as the first choice in hypotensive management (⁵,⁷).

Some studies suggest that phenylephrine is more effective in preventing hypotension after spinal anesthesia. Research conducted by Veeser et al. found that the use of ephedrine increased the risk of fetal acidosis five-fold compared to phenylephrine (⁸). In addition, the study by Muneer et al. also indicated that phenylephrine has a better safety profile with a lower incidence of fetal acidosis (⁹,¹⁰).

This study aims to compare the effectiveness of phenylephrine 100 mcg prophylaxis with ephedrine 10 mg in preventing the incidence of spinal anesthesia induced hypotension in patients undergoing C-section. The results of the study are expected to provide new insights that are useful in clinical practice and improve the safety and quality of service for pregnant women undergoing C-sections.

METHODS

In this study, a cross-sectional observational analytic design was used. During July to August 2024, this study was conducted to evaluate the relationship between pain assessment with delirium using the critical-care pain observation tool (CPOT) scale and the confusion assessment method for the intensive care unit (CAM-ICU) in intubated patients. The study has been done in the Intensive Care Unit (ICU) of 4 hospitals in Medan, Indonesia, namely H. Adam Malik General Hospital, Prof. Dr. Chairuddin P. Lubis Hospital Medan, Haji Hospital Medan, and Dr. Pirngadi Hospital Medan City, after obtaining ethical clearance from the Universitas Sumatera Utara ethics committee for the implementation of health research No. 811/KEPK/USU//2024 dated 04^thJuly 2024. This study also obtained ethical clearance and research permits from each multi-center institution with the following ethical research permit number information:

1. H. Adam Malik General Hospital, No. DP.04.03/D.XXVIII/6822/2024, dated 01^stAugust 2024
2. Prof. Dr. Chairuddin P. Lubis Hospital, No. 3056/UN5.5.6.D2/PPM/2024, dated 24^thJuly 2024
3. Haji Hospital Medan, No. 196/PSDM/RSUHM/VII/2024, dated 16^thJuly 2024
4. Dr. Pirngadi Hospital Medan City, No. 161/B.LitBang/2024, dated 17^thJuly 2024

The sample was drawn based on the predetermined inclusion and exclusion criteria, and the sample size was calculated using the formula for the relationship test (11). Inclusion criteria were intubated adult patients aged 18-40 years old who underwent elective cesarean section with spinal anesthesia technique and were admitted to the ICU. Exclusion criteria were vegetative patients, patients or patients' families who refused to participate in the study. The sample size estimate is calculated according to the sample formula for the relationship test:

n₁= n₂= 2{ \( \documentclass{article} \usepackage{amsmath} \begin{document} \displaystyle \frac{(1,96 + 0,84)11,32}{117,2 - 106,43} \end{document} \) }²

n₁= n₂= 2 {\( \documentclass{article} \usepackage{amsmath} \begin{document} \displaystyle \frac{31,696}{10,77} \end{document} \)}²

n₁= n₂= 16,82

n₁= n₂= 17

The results of the sample formula calculation obtained n1 = n2 = 17 samples. To anticipate drop out, 10% of the 17 samples needed were added. This resulted in each group requiring 19 samples, with a minimum total sample requirement of 38 samples. The sampling technique was performed using the simple random sampling method, ensuring that all subjects met the specified criteria.

In the course of the study, patients will be randomly divided into two groups: the phenylephrine group, receiving 100 mcg of phenylephrine and ephedrine group, receiving 10 mg of prophylactic ephedrine. The procedure begins with the measurement of blood pressure and heart rate before and after spinal anesthesia, at predetermined times. The data obtained from the measurements will be analyzed using SPSS software version 29, where descriptive and inferential analyses will be performed to assess the differences between the two groups.

The ethical aspects of the study were maintained by providing informed consent to each participant, explaining the purpose, benefits, and risks of the study. During the study, emergency management procedures were also in place to ensure patient safety. The results of this study are expected to provide significant information regarding the effectiveness of both prophylactic drugs in preventing spinal anesthesia induced hypotension.

RESULTS AND DISCUSSION

.....