An institutional-based prospective cohort study was carried out at public hospitals in North Showa Zone, Oromia region, from the seven public hospitals in the North Showa zone, those three hospitals, Salale University Comprehensive Specialized Hospital (SUCSH), Kuyu General Hospital (KGH), and Chancho Hospital, were selected by simple random sampling. SUCSH, which is located 112 km from Addis Ababa, KGH, which is located 43 km from SUCSH and 165 km from Addis Ababa, and Chancho Hospital, which is located 40 km from the capital city of Ethiopia.

Ethical approval for this study was obtained from the ethical review board of Wolaita Sodo University, College of Health Sciences and Medicine, with protocol unique No. CHSM/ERC/03/14. Then, a support letter was obtained from the Medical Director of the hospital to conduct the research, and written informed consent was obtained from study participants. Privacy and confidentiality of the interviews and information gathered was assured at all level of study.

All Parturients who underwent caesarean section delivery under spinal anesthesia at public hospitals in the Oromia Region, North Showa zone served as population’s source. ASA physical status II and III parturients, women over 18 years old, and women carrying a singleton pregnancy were included in the study from February 15 to May 15, 2022. Those who are in active labor, Patients with chronic hypertension, renal, or cardiac disease, diabetes, hypothyroidism, or hyperthyroidism in a parturient, Parturients with placenta abruption, placenta previa, BMI > 35 kg/m2, and adjuvants added to local anesthesia were excluded from the study.

The sample size was calculated using G*power version 3.1.9.7 software and the mean with standard deviation between the two groups were taken from a previous study done in Gondar on the topic of hemodynamic changes after spinal anesthesia in preeclamptic patients undergoing cesarean section [27, 28]. Based on this study, the lowest decrease of DBP in healthy groups is 26.18% ± 4.07 and the lowest decrease of DBP in preeclamptic groups is 23.93% ± 4.79. Using power of 80%, alpha 0.05, and effect size 0.5062319 the sample size was calculated using a prior power analysis with G Power 3.1.9.7 software to be 126. An additional 10% was added to the enrollment to offset potential dropouts, assuming the balanced design. The total sample size increases to 140 participants, with 70 in each group. A consecutive sampling technique was used to select study participants based on our inclusion criteria. The sample size was allocated to the hospitals by proportional to size using situational analysis from last year's performance report from selected hospitals.

Three trained BSc anesthetists used structured check lists and questionnaires developed by reviewing various literature to collect data from patient charts and intraoperative observations. Before the actual data collection, the adapted format was evaluated by an expert researcher. Patients were monitored with non-invasive automated blood pressure cuffs, an ECG, and pulse oximetry. Before any invasive procedure or spinal anesthesia, baseline blood pressure and heart rate were measured. All patients were preloaded with crystalloids (500–1000 ml) 10–15 min prior to SA being given, with oxytocin 10–20 IU, and then 10–12.5 mg of 0.5% isobaric bupivacaine was given between lumbar three and four and lumbar four and five levels. Immediately after spinal anesthesia administration, the parturients were put in a supine position with a pillow inserted under their shoulder, and the maternal hemodynamics parameters (SBP, DBP, MAP, and HR) were recorded. The exposed group was those with a systolic blood pressure (SBP) of greater than 140 mm Hg and a diastolic blood pressure (DBP) of greater than 90 mm Hg using noninvasive automated blood pressure (NIBP) measurement and urine protein dipstick plus one or two, and the controlled group was those with normal blood pressure and no protein urea (trace or negative protein dipstick). All patients selected for the study were asked for their consent, and after a complete sensory (> T10) block, a skin incision was started. Assessments of hemodynamic parameters were made at three-minute intervals, initially for the first twenty minutes, then at five-minute intervals until the end of the procedure. Supervisors checked each questionnaire daily, with a further cross-check by the principal investigator for completeness and consistency of data.

The data was checked for completeness, coded, and entered into Epi Data software version 4.6 before being exported into Statistical Package for the Social Sciences (SPSS) version 25 software, where missing values were checked before analysis.

A mean with a standard deviation was used to summarize data, tables, and figures to display results. The data were tested for normality using the Shapiro–Wilk normality test and histogram inspection, and homogeneity of variance was assessed using Levene’s test for equality of variances of two samples in SPSS version 25 software. Outliers were assessed by box plots. Normal distributed continuous variable was compared by using the independent t test and expressed by mean ± SD. Non normal distributed continuous data was compared using the Mann–Whitney U-test and expressed as the median or interquartile range (IQR).

The Chi-square test, or Fisher exact test, was used to calculate the categorical data between two groups as appropriate. The relative risk (RR) with a 95% confidence interval (CI) was used to determine the incidence of hypotension. A P value of less than 0.05 is considered significant. For repeated measures, homogeneity of covariance was assessed by Box’s M test. Mauchly’s test was used to check for sphericity, and the Greenhouse–Geisser correction was used when the assumption of sphericity was violated for the two-way interaction.

Preeclampsia is defined as a systolic blood pressure (SBP) of greater than 140 mm Hg, a diastolic blood pressure (DBP) of greater than 90 mm Hg using noninvasive automated blood pressure (NIBP) measurement and urine protein dipstick plus one or two, which is recorded from the patient's chart [29].

Severe preeclampsia is defined as systolic blood pressure (SBP) being greater than 160 mm Hg, diastolic blood pressure (DBP) being greater than 110 mm Hg using noninvasive automated blood pressure measurement (NIBP) and urine protein dipstick plus two or more, which is recorded in the patient's chart [29].

Hemodynamic change is defined as blood pressure and heart rate change from baseline by 20%, either an increase or decrease [7, 30, 31].

Mild hypotension: less than 20% decline in mean arterial blood pressure (MAP) below the base line in both groups [32].

Moderate hypotension: Blood pressure reduction of 20% to 30% from the mean arterial blood pressure baseline [32,33,34]

Severe hypotension: more than 30% decline in mean arterial blood pressure below the base line in both groups [32, 33].

The percentage fall in blood pressure and heart rate from base line (SBP, DBP, and MAP and HR) between two measurements is calculated as:

Percentage of hemodynamic change = (baseline value-current value/baseline value) * 100.

Negative (-) values indicate the percent fall of a parameter (SBP, DBP, MAP) from its corresponding baseline value and are higher than baseline values at some intervals after spinal anesthesia.

Normotensive: Having normal blood pressure and have no protein urea (trace or negative protein dipstick) [35].