title: Shock index: an effective predictor of outcome in postpartum haemorrhage?
abstract: OBJECTIVE
  To compare the predictive value of the shock index (SI) with conventional vital signs in postpartum haemorrhage (PPH), and to establish 'alert' thresholds for use in low-resource settings.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  UK tertiary centre.
  
  
  METHODS
  Women with PPH ≥ 1500 ml (n = 233).
  
  
  METHODS
  Systolic blood pressure (BP), diastolic BP, mean arterial pressure, pulse pressure, heart rate (HR) and SI (HR/systolic BP) were measured within the first hour following PPH. Values measured at the time of highest SI were selected for analysis. The area under the receiver operating characteristic curve (AUROC) for each parameter, used to predict admission to an intensive care unit and other adverse outcomes, was calculated. Sensitivity, specificity and negative/positive predictive values determined thresholds of the best predictor.
  
  
  METHODS
  Intensive care unit (ICU) admission, blood transfusion ≥ 4 iu, haemoglobin level <7 g/dl, and invasive surgical procedures.
  
  
  RESULTS
  Shock index has the highest AUROC to predict ICU admissions (0.75 for SI [95% CI 0.63-0.87] compared with 0.64 [95% CI 0.44-0.83] for systolic BP). SI compared favourably for other outcomes: SI ≥ 0.9 had 100% sensitivity (95% CI 73.5-100) and 43.4% specificity (95% CI 36.8-50.3), and SI ≥ 1.7 had 25.0% sensitivity (95% CI 5.5-57.2) and 97.7% specificity (CI 94.8-99.3), for predicting ICU admission.
  
  
  CONCLUSIONS
  Shock index compared favourably with conventional vital signs in predicting ICU admission and other outcomes in PPH, even after adjusting for confounding; SI <0.9 provides reassurance, whereas SI ≥ 1.7 indicates a need for urgent attention. In low-resource settings this simple parameter could improve outcomes. It was not possible to adjust for resuscitative measures administered following vital sign measurement that may have influenced the outcome.
authors.affiliation: Women's Health Academic Centre, King's College London, London, UK.
authors.forename: H L
authors.initials: HL
authors.lastname: Nathan
authors.forename: A
authors.initials: A
authors.lastname: El Ayadi
authors.forename: N L
authors.initials: NL
authors.lastname: Hezelgrave
authors.forename: P
authors.initials: P
authors.lastname: Seed
authors.forename: E
authors.initials: E
authors.lastname: Butrick
authors.forename: S
authors.initials: S
authors.lastname: Miller
authors.forename: A
authors.initials: A
authors.lastname: Briley
authors.forename: S
authors.initials: S
authors.lastname: Bewley
authors.forename: A H
authors.initials: AH
authors.lastname: Shennan
mesh_terms: D000328:Adult; D019540:Area Under Curve; D062186:Arterial Pressure; D001803:Blood Transfusion; D005260:Female; D006339:Heart Rate; D006801:Humans; D007362:Intensive Care Units; D010343:Patient Admission; D006473:Postpartum Hemorrhage / Q000503:physiopathology* / Q000628:therapy*; D011237:Predictive Value of Tests; D012372:ROC Curve; D012016:Reference Values; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012769:Shock / Q000175:diagnosis* / Q000628:therapy*; D016896:Treatment Outcome
keywords: Hypovolaemic shock; postpartum haemorrhage; shock index