Massive pulmonary embolism and respiratory failure in pregnancy — structured SAQ (15 marks)

(a) Diagnosis, thrombolysis and parallel preparation (6 marks)

One mark for the diagnosis, two for the thrombolytic agent and dose, one for the empiric reasoning, two for the parallel haemorrhage preparation and supportive care. ^[3][11]

• Diagnosis: high-risk (massive) pulmonary embolism — haemodynamic instability with echocardiographic right ventricular strain (dilatation, septal shift) in a high-risk postpartum woman.^[3]
• Thrombolysis: empiric systemic alteplase (recombinant tissue plasminogen activator) — 100 mg over two hours for high-risk PE with shock. I would give it now, on clinical and echocardiographic grounds, without waiting for computed tomography, because she is too unstable to transfer and the delay kills.^[3][11]
• Parallel preparation: the massive haemorrhage protocol must be running before the lytic goes in, because bleeding — uterine atony, wound ooze, generalised ooze — predictably follows successful lysis in the peripartum woman. Have blood products, uterotonics, tranexamic acid and balloon tamponade ready.^[11]
• Supportive care: high-flow oxygen, intravenous access, vasopressor (norepinephrine) for the hypotension, left lateral uterine displacement, and senior obstetric, anaesthetic and intensive care involvement.^[3][6]

(b) Rapid desaturation and ventilation settings (4 marks)

Two marks for the physiology, two for the ventilation settings. ^[1][7]

• Why she desaturates fast: pregnancy elevates the diaphragm and reduces the functional residual capacity by about 20 percent, while raising oxygen consumption to meet fetal and maternal demand. The combination — a smaller oxygen reservoir and higher demand — means the pregnant patient desaturates within seconds of apnoea, which is why every intubation begins with rigorous preoxygenation, a rapid sequence, a small endotracheal tube and a senior operator.^[6][7]
• Ventilation settings: lung-protective ventilation — tidal volume 6 mL per kilogram of predicted body weight (not actual body weight), plateau pressure held under 30 cm H₂O, positive end-expiratory pressure titrated, and permissive hypercapnia within limits, with head-up and lateral positioning and left uterine displacement.^[1][6]

(c) Perimortem interaction and post-thrombolysis anticoagulation (5 marks)

Two marks for the parallel perimortem sequence, one for the haemorrhage caveat, two for the anticoagulation plan. ^[3][5]

• Perimortem interaction: if she arrests, resuscitative hysterotomy (perimortem caesarean) and the thrombolysis run in parallel — neither waits for the other. Emptying the uterus relieves aortocaval compression and improves venous return during compressions, while the lytic addresses the obstructed pulmonary circulation. The published cases show survival after prolonged resuscitation with this combined approach.^[11][3]
• Haemorrhage caveat: after successful lysis in the peripartum woman, expect profuse bleeding and have the massive haemorrhage protocol, uterotonics and balloon tamponade ready — sometimes hysterectomy is required for control.^[11]
• Post-thrombolysis anticoagulation: if she survives, start low-molecular-weight heparin once the bleeding risk permits (typically when haemostasis is secure), dosed by weight in pregnancy, and continue for at least three to six months postpartum, transitioning to an oral anticoagulant with contraception counselling and a documented plan for the next pregnancy.^[5]