Postpartum hemorrhage (PPH) is the most common and dangerous complication of childbirth1. According to the World Health Organization (WHO), PPH is a visual estimate of greater than 500 milliliters of blood that is lost within 24 hours of birth 2, 3.  Bleeding within the first 24 hours following birth is known as primary postpartum hemorrhage, and bleeding between 24 and 12 weeks postpartum is known as secondary postpartum hemorrhage 4, 5.  Among the obstetrical complications, the most common one is PPH which affects up to 28.8% of deliveries6.

Metabolic acidosis, hypovolemic shock, multiple organ dysfunction (MODS), and mortality among mothers can occur within 2–6 hours of untreated PPH, based on the amount of blood loss and other variables such as previous anemia. Therefore, early detection and treatment of PPH in women are essential for maternal survival 7. Traditional diagnosis and severity of PPH are based on the visual estimation of blood loss as specified by the WHO. The identification of an efficient supplementary tool to identify women who are more likely to experience postpartum hemorrhage is therefore of great interest. To help identify these women, variations in vital signs throughout the postpartum period, including the shock index (SI), have been studied as a simple, accessible, and reasonably priced diagnostic tool 8. Shock index (SI) is a proposed indicator of early hypovolemia requiring blood transfusion. It is determined by dividing the systolic blood pressure by the heart rate 9.

Different shock index (SI) cut-off values have been taken to predict different adverse outcomes after delivery8, 9.  In one study 1.32 was taken as cut off value to predict post-partum hemorrhage after sensitivity was 90.91%, the precision was 89.74%, the favorable predicted value was 71.4%, the adverse predictive value was 97.2%, and the diagnostic accuracy was 91.8% when delivery involves a hysterectomy as the gold standard 7, 9. With immediate hysterectomy as the gold standard, the purpose of this study is to ascertain the diagnostic accuracy of the shock index in determining the cause of postpartum hemorrhage. The decision to begin therapy and/or move women to a top-tier facility before it's too late may be influenced by the availability of SI and vital sign evaluation. In low- and middle-income countries (LMICs), the bulk of maternal deaths from bleeding occurs, this will assist in identifying patients who are in danger, as prompt intervention can save the patient's life.

This study was designed as a cross-sectional validation study conducted in the Department of Gynecology and Obstetrics (Moula Baksh Hospital), Dr.Faisal Masood Teaching Hospital Sargodha from August 3, 2023 February 2, 2024. The patients were recruited using a non-probability sequential sampling technique. The sample size was calculated using a sensitivity and specificity calculator keeping a 95% confidence level, 7% precision, prevalence of PPH of 28.8%, 10 sensitivity of 90.9%, and specificity of 89.7%, the sample size was 226 patients 11. Inclusion Criteria encompassed women aged 20 years to 40 years with singleton pregnancy. Patients with gestational age 35-42 weeks. Patients undergoing normal vaginal delivery or LSCS were enrolled in the labor room. Patients were excluded if they were diagnosed with pre-eclampsia, eclampsia, or septic shock, as recorded in their medical files, or if they were unwilling to participate in the study.  Following ethics board clearance, patients who met the inclusion criteria were admitted to the labor room. After the study's goal was explained, formal informed consent was obtained. Demographic information about gestational age and age was recorded. All patients undergoing delivery were kept in the recovery room for vital monitoring. Pulse and blood pressure were taken every 1 hour. Shock index was calculated at 1 hour after delivery. For PPH management blood and fluid replacement was done. Bimanual compression and external uterine massage were employed as the first treatments for PPH. These compression methods promote uterine contractions, which help to expel clots or retained placenta and prevent atony. Misoprostol was administered to patients who were not responding. Depending on the patient's state, uterine tamponade, manual placenta removal, manual clot removal, and embolization of uterine arteries are among the procedures performed in PPH therapy. In non-responding cases, an emergency hysterectomy was done. The patient was followed for 24 hours to observe for PPH and the need for an emergency hysterectomy.

STATISTICAL ANALYSIS

Data entry and analysis were done using SPSS version 22.0. The mean and variation for quantitative variables, such as age and gestational age were calculated. For categorical factors such as the requirement for a hysterectomy and diagnosis by shock index, frequency as well as percentage were computed. Using the necessity of an emergency hysterectomy as the gold standard, the following parameters were calculated: positive predictive value, negative predictive value, and diagnostic accuracy were computed by building a 2x2 table. Effect modifiers like age and gestational age were addressed through data stratification. Post-stratification diagnostic accuracy was calculated and a p-value ≤0.05 was taken as statistically significant.

The mean age of the 226 female participants in our research was 30.63±5.6 years. 38.7±2.3 weeks was the average gestational age. Shock index diagnosed postpartum hemorrhage in 30.5% of females. Hysterectomy was done in 27.4% of females due to postpartum hemorrhage.

Table 1: Frequency of patients with PPH diagnosed by SI and hysterectomy

The shock index has a sensitivity of 90.3%, specificity of 92.1%, positive predictive value of 81.2%, negative predictive value of 96.2%, and diagnostic accuracy of 91.5% in diagnosing postpartum hemorrhage, taking the need for hysterectomy as the gold standard.

Table 2: Diagnostic accuracy of SI in predicting PPH taking hysterectomy as gold standard

The data was stratified for age and gestational age. The diagnostic accuracy SI for age 20-30 was 96% with Sensitivity and specificity of 93.8%, 97.1% with PPV and NPV of 93.8% and 97.1% respectively. The diagnostic accuracy SI for ages 31-40 was 91% with Sensitivity and specificity of 88.7%, 88.5% with PPV and NPV of 70.3% and 95.5%

Table 3: Data stratification for diagnostic accuracy of SI and age groups

The diagnostic accuracy SI for gestational age equal to or less than 38 weeks was 96% with sensitivity and specificity of 94.4%, 97% with PPV and NPV of 94.4% and 97% respectively.  The diagnostic accuracy SI for gestational age >38 weeks was 879% with sensitivity and specificity of 84.6%, 88.8% with PPV and NPV of 66.7% and 95.7% respectively.

Table 4: Data stratification for diagnostic accuracy of SI and gestational age groups

Postpartum hemorrhage (PPH) is a leading cause of maternal mortality worldwide12, responsible for over 70,000 deaths annually. Maternal anemia greatly increases the risk of PPH13. Despite the existence of some risk assessment instruments and prognosis models for PPH, their therapeutic usefulness in the broader obstetric community has not been adequately established. About 60% of women who suffer from PPH have no risk factors, while just 1.8% to 7.3% of women who meet risk stratification criteria as high-risk also suffer from PPH 14. Timely identification of PPH and suitable early therapy are critical for its effective management in basic maternal care facilities when obstetric care personnel and blood products are limited.

Several organizations, such as the Japan Society of Obstetrics and Gynecology, the Royal College of Obstetricians and Gynecologists, and the International Federation of Gynecology and Obstetrics, have suggested standard protocols for managing the symptoms of PPH to lower PPH-related maternal mortality and morbidity 14. By identifying gradual changes in vital signs, particularly the Shock Index (SI) and associated symptoms (such as tachypnea, chilly and clammy skin, and oliguria), which indicate a state of shock, these methods emphasize the early detection of PPH. The Shock Index, which is calculated by dividing the heart rate by systolic blood pressure, is said to be a crucial sign of hypovolemia and hemodynamic instability in medical situations. SI can assess the therapeutic impact of different therapies and calculate the total blood loss in obstetric situations like severe bleeding. To predict the probability of PPH-associated morbidities, SI is better than traditional vital signs and is therefore regarded as an early surrogate indication of PPH. The goal of this study was to ascertain the diagnostic accuracy of

SI in predicting PPH, with hysterectomy serving as the gold standard.

In our study, 226 females were enrolled with a mean age of 30.63±5.6 years. The mean gestational age was 38.7±2.3 weeks. Shock index diagnosed postpartum hemorrhage in 30.5% of females. Hysterectomy was done in 27.4% of females due to postpartum hemorrhage. Shock index has a sensitivity of 90.3%, specificity of 92.1%, positive predictive value of 81.2%, negative predictive value: of 96.2%, and diagnostic accuracy of 91.5% in diagnosis of postpartum hemorrhage taking need for hysterectomy as gold standard.

Varying results were seen in previous studies. In one study 1.32 was taken as cut off value to predict post-partum hemorrhage after delivery taking the need for hysterectomy as the gold standard, sensitivity was 90.91%, specificity was 89.74%, positive predictive value was 71.4%, negative predictive value was 97.2% and diagnostic accuracy was 91.8%11.

In one study different parameters were used to compare SI and specificity was low in all cases with good sensitivity. Taking clinical diagnosis of PPH as gold standard SI showed 31% sensitivity and 95% specificity, taking estimated blood loss ≥ 500 ml as gold standard SI showed 27% sensitivity and 97% specificity, taking peripartum Hb drop ≥ 10% as gold standard SI showed 31% sensitivity and 85% specificity, taking peripartum Hb drop ≥ 20 g/L as gold standard SI showed 14% sensitivity and 97% specificity and taking Postpartum uterotonics as gold standard as SI showed38% sensitivity and 72% specificity15.

There were 270 women in all in another research. 570.66 ± 360.04 mL of blood were lost on average within 24 hours following vaginal birth. Within two hours, 91% of women had lost 90% of the total blood loss, with 73% of the 24-hour total occurring in the first 40 minutes. Heart rate (HR) and SI changes were statistically significant predictors of postpartum hemorrhage (P≤0.05). Using a SI index of 1.3 at two hours, the sensitivity is 70.4% and the specificity is 69.8% 16.

According to our study, the shock index has a high sensitivity as well as specificity for predicting postpartum hemorrhage. The diagnostic accuracy of the SI cut-off points of 1.3 at 60 minutes after birth is good.

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