Postpartum haemorrhage in a woman on enoxaparin with an unexpectedly normal shock index

Shock index = heart rate ÷ systolic BP = 118 ÷ 152 = 0.78, which sits below the usual 0.9 threshold and looks reassuring.

It is misleading because the systolic pressure is not her normal. Her baseline is 110/70, and she is now hypertensive at 152/94 - most likely from pain, anxiety and sympathetic drive, possibly with a pre-eclampsia component. That vasoconstriction holds the systolic up while she is already significantly hypovolaemic; a 'normal' or high blood pressure in an actively bleeding postpartum woman is a warning, not reassurance. The tachycardia of 118 and the narrow pulse pressure are closer to the truth. Trend the shock index against her own baseline, not against the population cut-off.

Characterisation: this is a primary postpartum haemorrhage, ongoing and not controlled, with estimated loss already 1,300 mL plus ongoing loss - well beyond 1,000 mL, and in a woman of average body habitus that is approaching 25% of blood volume, i.e. a major haemorrhage with haemodynamic compromise (tachycardia, pallor, dizziness, Hb drop of 3.6 g/dL). The likely cause is uterine atony (large infant, prolonged second stage, high parity, overdistended uterus, possibly oxytocin receptor desensitisation), but tone, trauma (episiotomy, vacuum), tissue (retained fragments/placenta) and thrombin (she is anticoagulated) must all be considered. Hypertension also flags possible pre-eclampsia, which limits which uterotonics you can use.

Work in parallel - call for help and start the PPH protocol while assessing.

1. Resuscitation: two large-bore IVs, oxygen, continuous monitoring, bloods including full count, coagulation, fibrinogen, chemistry, crossmatch 4 units and a massive transfusion protocol if loss continues. Give warmed balanced crystalloid cautiously and start blood products early; in ongoing major haemorrhage give red cells and consider fibrinogen replacement/FFP as per protocol. Keep her warm.
2. Mechanical: bimanual uterine massage and compression, empty the bladder (indwelling catheter), inspect the perineum, vagina and cervix for tears with good lighting, and remove retained clots.
3. Tranexamic acid 1 g IV over 10 minutes as soon as possible - it reduces death from bleeding when given within 3 hours of birth. Being on prophylactic enoxaparin does not justify withholding it in a woman who is actively bleeding; record the timing of the last dose and inform the physician and haematology. A second 1 g dose may be given if bleeding continues after 30 minutes.
4. Uterotonics: continue/optimise oxytocin infusion as prescribed; add a second-line agent. Avoid ergometrine/methylergometrine because she is hypertensive - it causes vasoconstriction. Misoprostol 800 micrograms sublingually is an option; carboprost is effective but is avoided in asthma. The choice must be prescribed and documented.
5. Enoxaparin: withhold further doses, tell the team when the last dose was given, and let the physician weigh partial reversal with protamine (only partly effective for LMWH) or factor concentrates against thrombosis risk. Do not delay uterotonics or TXA for this decision.

Escalation triggers - she has already met them: continuing bleeding despite massage, oxytocin, TXA and a second-line uterotonic; an atonic uterus that does not respond; haemodynamic compromise; and transfusion started. Additional triggers would be estimated loss beyond about 1,500–2,000 mL, persistent tachycardia, oliguria, falling Hb despite transfusion, lactate rising, or coagulopathy (fibrinogen low, INR prolonged).

Next steps are mechanical and surgical, not more of the same drug: intrauterine balloon tamponade, vacuum-induced bleeding control, uterine artery embolisation in a stable patient, or laparotomy with compression sutures, vessel ligation or hysterectomy. That means escalate to the senior obstetrician and anaesthetist immediately, alert the blood bank and theatre, move to a high-dependency or operating theatre environment, and involve haematology about the anticoagulation.

Documentation: estimated blood loss with the method used and cumulative total; time-stamped observations including BP, HR, shock index and urine output; the uterine findings at each assessment; every drug with dose and route (TXA, uterotonics), every transfusion product with unit numbers and times; the time of the last enoxaparin dose; the names and times of clinicians informed and their instructions; the patient's own words and her family's involvement; and the debrief plan.

After stabilisation: check Hb/ferritin, plan iron or transfusion, thromboprophylaxis restart decision, and a documented plan for future pregnancies and delivery.