Serum uric acid as a novel marker for uterine atony and post-spinal vasopressor use during cesarean delivery

Risk Factors for Atonic Postpartum Hemorrhage: A Systematic Review and Meta-analysis

OBJECTIVE

To identify and quantify risk factors for atonic postpartum hemorrhage.

DATA SOURCES

PubMed, CINAHL, EMBASE, Web of Science, and and ClinicalTrials.gov databases were searched for English language studies with no restrictions on date or location. Studies included randomized trials, prospective or retrospective cohort studies, and case-control studies of pregnant patients who developed atonic postpartum hemorrhage and reported at least one risk factor.

METHODS OF STUDY SELECTION

Title, abstract, and full-text screening were performed using the Raayan web application. Of 1,239 records screened, 27 studies were included in this review. Adjusted or unadjusted odds ratios (ORs), relative risks, or rate ratios were recorded or calculated. For each risk factor, a qualitative synthesis of low and moderate risk of bias studies classifies the risk factor as definite, likely, unclear, or not a risk factor. For risk factors with sufficiently homogeneous definitions and reference ranges, a quantitative meta-analysis of low and moderate risk of bias studies was implemented to estimate a combined OR.

TABULATION, INTEGRATION, AND RESULTS

Forty-seven potential risk factors for atonic postpartum hemorrhage were identified in this review, of which 15 were judged definite or likely risk factors. The remaining 32 assessed risk factors showed no association with atonic postpartum hemorrhage or had conflicting or unclear evidence.

CONCLUSION

A substantial proportion of postpartum hemorrhage occurs in the absence of recognized risk factors. Many risk factors for atonic hemorrhage included in current risk-assessment tools were confirmed, with the greatest risk conferred by prior postpartum hemorrhage of any etiology, placenta previa, placental abruption, uterine rupture, and multiple gestation. Novel risk factors not currently included in risk-assessment tools included hypertension, diabetes, and ethnicity. Obesity and magnesium were not associated with atonic postpartum hemorrhage in this review.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, CRD42020157521.

Association of Maternal Hyperuricemia with Post-Spinal Hypotension in Pre-Eclamptic Parturients Undergoing Emergency Cesarean Delivery: a Prospective Observational Study

Pre-eclampsia is commonly associated with higher serum uric acid levels, which is known to increase vascular tone. A previous retrospective study established a positive correlation between raised serum uric acid levels and reduced incidence of post-spinal hypotension. However, until date, this correlation has not been prospectively evaluated in exclusively pre-eclamptic women. Pre-eclamptic parturients undergoing emergency cesarean delivery under subarachnoid block were included. Sample for measuring serum uric acid level was obtained prior to shifting patients for cesarean delivery. Following spinal anesthesia, we recorded episodes of hypotension (fall of mean arterial pressure more than 20% from baseline values), use of vasopressors, and intraoperative blood loss. Our primary objective was to study the association between maternal hyperuricemia and incidence of post-spinal hypotension. Our secondary objectives included amount of vasopressors administered to maintain targeted mean arterial pressure before delivery of the baby, intraoperative blood loss, and immediate neonatal outcome. A total of 95% parturients had hyperuricemia, with mean serum uric acid level being 6.94 ± 0.9 mg/dl. Incidence of post-spinal hypotension was significantly lower in women who had hyperuricemia as compared with those with normal serum uric acid levels (21% vs 75%; p = 0.015). Mean serum uric acid levels were significantly high (p = 0.001) in patients not requiring any vasopressors (7.2 ± 1.2 mg/dl) than in those requiring moderate (5.70 ± 0.79 mg/dl) to high dose (5.75 ± 0.77 mg/dl) of vasopressors. There is a high incidence of hyperuricemia in pre-eclamptic parturients. In these patients, elevated serum uric acid levels is associated with lower incidence of post-spinal hypotension and reduced need of vasopressors to maintain maternal blood pressure within a normal range.

Maternal hyperuricemia as a marker of post-spinal hypotension and uterine tone during cesarean delivery: a prospective observational study

PURPOSE

Raised serum uric acid, a marker of oxidative stress, is known to increase vascular tone and depress myometrial contractility. A rise in serum uric acid levels has also been reported during labor, warranting its correlation with post-spinal hypotension and uterine tone.

METHODS

Serum UA sample was drawn from enrolled healthy, laboring parturients. Of these, 100 women who required emergency cesarean delivery were re-sampled prior to surgery. Following spinal anesthesia we recorded episodes of hypotension (MAP < 80% of baseline), use of vasopressors and supplemental uterotonics. The primary outcome was maternal hyperuricemia (1SD > appropriate for gestation age) and its correlation with post-spinal hypotension. Secondary outcomes were total vasopressors used, duration of labor and its effect on uric acid levels, uterine tone and neonatal outcome.

RESULTS

Hyperuricemia was observed in 33% of parturients. On comparing with women showing normal uric acid levels, hyperuricemic parturients experienced significantly lower incidence of post-spinal hypotension (45.5% vs. 67.2%; p value = 0.04) and lower vasopressor usage (p value = 0.06). Clinically, an increased use of supplemental uterotonics in these parturients was noted (p = 0.20). The duration of labor had no impact on uric acid levels. Neonatal outcome was unaffected.

CONCLUSIONS

In healthy, normotensive parturients undergoing emergency cesarean delivery, maternal hyperuricemia is associated with lower incidence of post-spinal hypotension and reduced need of vasopressors. Elevated serum uric acid levels may also be associated with decreased uterine tone, necessitating greater requirement of supplemental uterotonics. However, further prospective trials are needed to strongly establish this association.

Immediate breastfeeding and skin-to-skin contact during cesarean section decreases maternal oxidative stress, a prospective randomized case-controlled study

OBJECTIVE

Immediate skin-to-skin contact (ISSC) and early breastfeeding are recommended for the wellbeing of the neonate. In this study, we aimed to evaluate the effect of ISSC and early breastfeeding on maternal oxidative stress and postoperative pain.

METHODS

A total of 90 patients were randomized into two groups based on the timing of skin-to-skin contact and breastfeeding. Group 1 (n = 45) was provided ISSC and breastfeeding in the operating room during the cesarean section (C/S). Group 2 (n = 45) breastfed their babies 1 h after the C/S. As markers of oxidative stress, maternal serum levels of total antioxidant status (TAS), total oxidant status (TOS) and oxidative stress indices (OSI) were evaluated. Maternal oxytocin levels and the relation between these parameters and postoperative pain were also evaluated.

RESULTS

The postoperative TAS levels were significantly higher, whereas TOS and OSI levels were lower in Group 1 than Group 2. Negative correlations between oxytocin level and postoperative TOS and OSI were observed, as was a positive correlation between oxytocin level and postoperative TAS.

CONCLUSIONS

The effect of ISSC and early breastfeeding on mothers was documented for the first time in this study. Our results demonstrated ISSC and early breastfeeding during C/S reduce maternal oxidative stress.