The inferior vena cava diameter is a useful ultrasound finding for predicting postpartum blood loss

Predictive accuracy of the shock index for severe postpartum hemorrhage in high-income countries: A systematic review and meta-analysis

AIM

The shock index has been suggested as a screening tool for predicting postpartum hemorrhage (PPH); however, there is little comprehensive evidence regarding its predictive accuracy. This systematic review and meta-analysis aim to investigate the predictive accuracy of the shock index for severe PPH in high-income countries.

METHODS

A comprehensive search was conducted on MEDLINE, Cochrane Central Register of Controlled Trials, and Web of Science (from inception to June 2021). Studies assessing the predictive performance of the shock index for PPH in high-income countries were included. Two or more reviewers independently extracted the data and assessed the risk of bias and applicability concerns using the modified Quality Assessment of Diagnostic Accuracy Studies 2 tool. PPH requiring higher-level care, such as blood transfusions, were considered as primary analyses. We described the hierarchical summary receiver-operating characteristic curve for data synthesis.

RESULTS

Nine studies were included after the eligibility assessment. All studies were considered to either have a high risk of bias or high applicability concerns. The sensitivity of the four studies that defined severe PPH as PPH requiring blood transfusion ranged from 0.51 to 0.80, whereas their specificity ranged from 0.33 to 0.92.

CONCLUSIONS

This review shows that the predictive performance of the shock index for severe PPH is inconsistent. Therefore, the evidence for using the shock index alone as a screening tool for PPH in high-income countries is insufficient.

STUDY REGISTRATION

This review was prospectively registered with the University Hospital Medical Information Network Clinical Trials Registry (UMIN000044230).

Latest advances in postpartum hemorrhage management

Hemorrhage is the leading cause of maternal mortality worldwide. A maternal health priority is improving how healthcare providers prevent and manage postpartum hemorrhage (PPH). Because anesthesiologists can help facilitate how hospitals develop approaches for PPH prevention and anticipatory planning, we review the potential utility of PPH risk-assessment tools, bundles, and protocols. Anesthesiologists rely on clinical and diagnostic information for initiating and evaluating medical management. Therefore, we review modalities for measuring blood loss after delivery, which includes visual, volumetric, gravimetric, and colorimetric approaches. Point-of-care technologies for assessing changes in central hemodynamics (ultrasonography) and coagulation profiles (rotational thromboelastometry and thromboelastography) are also discussed. Anesthesiologists play a critical role in the medical and transfusion management of PPH. Therefore, we review blood ordering and massive transfusion protocols, fixed-ratio vs. goal-directed transfusion approaches, coagulation changes during PPH, and the potential clinical utility of the pharmacological adjuncts, tranexamic acid, and fibrinogen concentrate.

Decreased inferior vena cava diameter as an early marker in postpartum hemorrhage

OBJECTIVES

To examine the association between inferior vena cava (IVC) diameter and postpartum blood loss and assess whether IVC diameter is a useful marker in the evaluation of intravascular volume status in women with postpartum hemorrhage (PPH).

METHODS

This was a prospective case-control study conducted in a university medical teaching center in Afula, Israel, between November 2018 and March 2020. The study cohort consisted of women with a singleton pregnancy who delivered vaginally at term. The PPH group included women diagnosed with PPH based on visually estimated blood loss of 1000 mL or more at the time of enrolment. Hemodynamically unstable women or women with major bleeding at the time of diagnosis were not included. The control group consisted of women with an uneventful fourth stage of labor. IVC diameter was measured using transabdominal ultrasonography during inspiration (IVCi diameter) and expiration (IVCe diameter), and the collapsibility index was calculated ((IVCe - IVCi)/IVCe × 100). The primary outcome was the percentage difference in IVC diameter and collapsibility index between the PPH group and controls. The performance of the IVC collapsibility index in the prediction of the need for blood transfusion in women with PPH was assessed. In order to demonstrate a difference of 20% with a power of 80% and alpha of 0.05, 108 women, at a ratio of 1:2 in the study and control groups, respectively, were needed.

RESULTS

Overall, 36 and 72 women were included in the final analysis in the PPH and control groups, respectively. IVCi and IVCe diameters were significantly smaller in the PPH group (0.93 ± 0.30 cm and 1.26 ± 0.32 cm, respectively) than in controls (1.42 ± 0.31 cm and 1.75 ± 0.28 cm, respectively) (P = 0.001 for both). The percentage reductions in IVCi and IVCe diameters in the PPH group compared with controls were 35.0% and 28.0%, respectively. IVC collapsibility index was increased significantly, by 42.9% (26.04 ± 8.67% vs 18.15 ± 5.07%; P = 0.001) in the PPH group compared with controls. IVC collapsibility index was a significant predictor of the need for blood transfusion and correctly predicted 81% of cases. Logistic regression analysis demonstrated that IVC collapsibility index was also a significant predictor of a drop in hemoglobin level of ≥ 2 g/dL (P = 0.001).

CONCLUSIONS

IVC diameter changes in response to postpartum blood loss. Measurement of IVC diameter using transabdominal ultrasonography is an objective and useful non-invasive method for the early evaluation of intravascular volume status in women with PPH and for the prediction of cases that might require blood transfusion. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Can Inferior Vena Cava Diameter and Collapsibility Index Be a Predictor in Detecting Preoperative Intravascular Volume Change in Pediatric Patients?

Background: Inferior vena cava (IVC) ultrasound measurement is a reliable indicator used in the assessment of intravascular volume status. The aim of this study was to evaluate intravascular volume changes in pediatric patients by measuring the IVC diameter and collapsibility index (CI) in children whose oral feeding was restricted preoperatively. Material and Methods: From May 2018 to October 2018, a total of 55 pediatric patients who were scheduled for surgery were included in this prospective, observational, cohort study. Fasting and satiety IVC diameters and CIs of patients were determined by ultrasonographic evaluation twice: in the preoperative preliminary evaluation, when the patients were satiated, and before surgery, during a fasting period of 6–8 hours. Ultra-sonographic data were recorded and compared between fasting and satiety periods. Results: In the grey scale (B-mode), mean IVC diameter was significantly higher when the patients were satiated, compared to the measurements made just before surgery during the fasting period. In the M-mode, the mean IVC diameter was significantly higher only during the inspiratory phase when the patients were satiated, while during the expiratory phase it was detected to be statistically similar. Mean CI was significantly higher in the immediate preoperative period, compared to the assessment made when satiated. Conclusion: Preoperative ultrasound IVC diameter and CI measurement can be a practical and useful method for evaluating preoperative intravascular volume in children.

Comparison of common perioperative blood loss estimation techniques: a systematic review and meta-analysis

Estimating intraoperative blood loss is one of the daily challenges for clinicians. Despite the knowledge of the inaccuracy of visual estimation by anaesthetists and surgeons, this is still the mainstay to estimate surgical blood loss. This review aims at highlighting the strengths and weaknesses of currently used measurement methods. A systematic review of studies on estimation of blood loss was carried out. Studies were included investigating the accuracy of techniques for quantifying blood loss in vivo and in vitro. We excluded nonhuman trials and studies using only monitoring parameters to estimate blood loss. A meta-analysis was performed to evaluate systematic measurement errors of the different methods. Only studies that were compared with a validated reference e.g. Haemoglobin extraction assay were included. 90 studies met the inclusion criteria for systematic review and were analyzed. Six studies were included in the meta-analysis, as only these were conducted with a validated reference. The mixed effect meta-analysis showed the highest correlation to the reference for colorimetric methods (0.93 95% CI 0.91–0.96), followed by gravimetric (0.77 95% CI 0.61–0.93) and finally visual methods (0.61 95% CI 0.40–0.82). The bias for estimated blood loss (ml) was lowest for colorimetric methods (57.59 95% CI 23.88–91.3) compared to the reference, followed by gravimetric (326.36 95% CI 201.65–450.86) and visual methods (456.51 95% CI 395.19–517.83). Of the many studies included, only a few were compared with a validated reference. The majority of the studies chose known imprecise procedures as the method of comparison. Colorimetric methods offer the highest degree of accuracy in blood loss estimation. Systems that use colorimetric techniques have a significant advantage in the real-time assessment of blood loss.