24.3 Obstetric & Genitourinary Emergencies and the Physiology of Pregnancy
Key Takeaways
Normal pregnancy produces a compensated respiratory alkalosis with a PaCO2 of about 28 to 32 mmHg, so a PaCO2 of 40 mmHg in a breathless pregnant patient indicates impending respiratory failure.
Magnesium sulfate is given for seizure prophylaxis in preeclampsia with severe features and for treatment of eclamptic seizures, with loss of deep tendon reflexes as the earliest sign of toxicity.
Resuscitative cesarean delivery should begin by about 4 minutes into maternal cardiac arrest, aiming for delivery within 5 minutes, and it improves maternal hemodynamics.
After 20 weeks of gestation, manual left uterine displacement is used during CPR rather than a left lateral tilt, which degrades compression quality.
Obstructed, infected upper urinary tract requires urgent decompression with a ureteral stent or percutaneous nephrostomy; antibiotics alone do not control the source.
Physiologic Changes That Change ICU Decisions
| System | Change by the third trimester | Implication |
|---|---|---|
| Cardiovascular | Cardiac output up 30% to 50%, heart rate up 15 to 20 bpm, systemic vascular resistance down, blood pressure slightly lower | A "normal" blood pressure of 140/90 mmHg is hypertension; aortocaval compression after 20 weeks reduces venous return when supine |
| Blood | Plasma volume up about 50% with a smaller red cell mass increase: dilutional anemia; a hypercoagulable state | Blood loss is tolerated until late, then decompensation is abrupt; venous thromboembolism risk rises several-fold |
| Respiratory | Minute ventilation up 30% to 50%, PaCO2 about 28 to 32 mmHg with a compensated respiratory alkalosis (bicarbonate around 18 to 22 mEq/L), functional residual capacity down about 20%, oxygen consumption up | Rapid desaturation during apnea; a PaCO2 of 40 mmHg in a dyspneic patient means impending failure; difficult airway from edema and increased Mallampati grade |
| Renal | GFR up about 50%; creatinine normally 0.4 to 0.6 mg/dL | A creatinine of 1.0 mg/dL is abnormal |
| Gastrointestinal | Lower esophageal sphincter tone reduced, delayed emptying | High aspiration risk: rapid-sequence intubation with cricoid pressure considered, smaller tube sizes for edematous airways |
Intubation in pregnancy calls for optimal preoxygenation, a smaller endotracheal tube (6.5 to 7.0 mm), video laryngoscopy, the most experienced operator, and preparation for a difficult airway.
Hypertensive Disorders of Pregnancy
- Preeclampsia with severe features: systolic 160 mmHg or more or diastolic 110 mmHg or more, thrombocytopenia, kidney injury, elevated transaminases, pulmonary edema, or new cerebral or visual symptoms. Proteinuria is not required for diagnosis when severe features are present.
- Treatment:
- Blood pressure control with IV labetalol, hydralazine, or oral immediate-release nifedipine, targeting a systolic below 160 mmHg and a diastolic below 110 mmHg while avoiding precipitous drops that compromise placental perfusion.
- Magnesium sulfate (4 to 6 g load, then 1 to 2 g/h) for seizure prophylaxis in severe features, and for treating eclamptic seizures. Monitor reflexes, respirations, and urine output; loss of deep tendon reflexes is the earliest sign of toxicity, and calcium gluconate is the antidote. Reduce the dose in kidney impairment.
- Delivery is the definitive treatment; timing depends on gestational age and severity, with corticosteroids for fetal lung maturity when appropriate.
- Avoid ACE inhibitors, ARBs, and nitroprusside (fetal cyanide risk).
- HELLP syndrome: Hemolysis, Elevated Liver enzymes, Low Platelets. Watch for hepatic subcapsular hematoma and rupture, disseminated intravascular coagulation, and acute kidney injury. Treatment is delivery with supportive transfusion; corticosteroids improve laboratory values but not clinical outcomes.
- Eclampsia: magnesium is the treatment for seizures (superior to phenytoin and diazepam), with delivery and airway protection. Consider PRES and intracranial hemorrhage if seizures recur or focal signs appear.
- Postpartum presentations: preeclampsia and eclampsia can occur up to 6 weeks postpartum, so do not dismiss severe headache or hypertension in a recently delivered patient.
- Acute fatty liver of pregnancy: third-trimester nausea, jaundice, hypoglycemia, coagulopathy, and kidney injury; the treatment is urgent delivery and supportive care, including glucose.
Hemorrhage and Other Obstetric Emergencies
- Postpartum hemorrhage: the four Ts:
- Tone (uterine atony, which is the most common): uterine massage, oxytocin, then misoprostol, methylergonovine (avoid in hypertension), and carboprost (avoid in asthma); tranexamic acid within 3 hours (the WOMAN trial reduced death from bleeding); intrauterine balloon tamponade, uterine artery embolization, compression sutures, and hysterectomy.
- Trauma (lacerations, uterine rupture, inversion): repair and reposition.
- Tissue (retained placenta, placenta accreta spectrum): removal, with planned multidisciplinary delivery for accreta.
- Thrombin (coagulopathy, including amniotic fluid embolism and abruption): targeted blood product therapy with early fibrinogen.
- Placental abruption: painful bleeding with a tense uterus, often with disseminated intravascular coagulation and fetal distress.
- Amniotic fluid embolism: sudden collapse with coagulopathy (see the nonthrombotic embolism section).
- Peripartum cardiomyopathy and pulmonary embolism in pregnancy: the leading cardiovascular causes of maternal death; diagnostic imaging (CT pulmonary angiography or perfusion scanning) should not be withheld because of pregnancy.
- Sepsis in pregnancy: chorioamnionitis, endometritis, septic abortion, pyelonephritis (common and often severe), and group A streptococcal infection. Thresholds for ICU admission should be low, given the physiologic reserve masking deterioration.
Cardiac Arrest in Pregnancy
- High-quality CPR with hands in the standard position.
- Manual left uterine displacement after 20 weeks of gestation (or when the uterus is at or above the umbilicus), rather than a left lateral tilt, which degrades compressions.
- Early airway management because of hypoxemia risk and aspiration.
- Standard drugs and defibrillation energies; do not withhold or reduce them.
- Resuscitative (perimortem) cesarean delivery: prepare immediately and begin by about 4 minutes if there is no return of spontaneous circulation, aiming to deliver within 5 minutes. It relieves aortocaval compression and improves maternal hemodynamics; it is a maternal resuscitation intervention and is performed where the patient lies, not in an operating room.
- Search for specific causes: hemorrhage, amniotic fluid embolism, pulmonary embolism, magnesium toxicity, local anesthetic toxicity (give lipid emulsion), eclampsia, sepsis, and anaphylaxis.
- Magnesium toxicity causing arrest is treated with calcium gluconate.
Genitourinary Emergencies
| Condition | Features | Management |
|---|---|---|
| Obstructive uropathy with infection | Flank pain, fever, sepsis, hydronephrosis from stone, tumor, or stricture | Urgent decompression with a ureteral stent or percutaneous nephrostomy plus antibiotics; antibiotics alone do not achieve source control |
| Emphysematous pyelonephritis | Gas in the renal parenchyma, usually in diabetes | Antibiotics plus drainage; nephrectomy for extensive disease |
| Fournier gangrene | Necrotizing fasciitis of the perineum; pain out of proportion, crepitus, rapid progression | Immediate wide surgical debridement, broad-spectrum antibiotics with clindamycin or linezolid for toxin suppression, and resuscitation |
| Renal infarction | Sudden flank pain with a very high LDH and hematuria, often with atrial fibrillation | Anticoagulation; endovascular therapy in selected cases |
| Renal and bladder trauma | Hematuria after blunt or penetrating injury | Most renal injuries are managed nonoperatively; intraperitoneal bladder rupture requires surgical repair, extraperitoneal usually catheter drainage |
| Urinary retention and post-obstructive diuresis | Massive diuresis after relief of chronic obstruction | Monitor and replace volume and electrolytes; avoid overcorrection |
| Priapism | Ischemic (low-flow) priapism is a compartment syndrome of the penis, often from sickle cell disease or drugs | Urgent aspiration and irrigation with phenylephrine; urology involvement |
| Testicular torsion | Acute scrotal pain with a high-riding testis and absent cremasteric reflex | Immediate surgical exploration; the window is about 6 hours |
| Rhabdomyolysis with compartment syndrome | Limb pain, pressures above 30 mmHg | Fasciotomy, aggressive fluid, monitoring for kidney injury |
Note
Two rules from this section recur on examinations: an infected obstructed kidney needs drainage, not just antibiotics, and in pregnancy, a normal PaCO2 is an abnormal finding.
A 31-year-old woman at 33 weeks of gestation is admitted with status asthmaticus. She is tiring, with a respiratory rate of 32 breaths/min and arterial blood gas showing pH 7.36, PaCO2 41 mmHg, and PaO2 76 mmHg on 6 L/min of oxygen. Which interpretation and action are correct?
These gases are normal for pregnancy; continue current therapy and reassess in 2 hours
This represents respiratory failure for a pregnant patient; prepare for intubation with an experienced operator
This is a compensated metabolic alkalosis; give acetazolamide to correct the bicarbonate
This indicates hyperventilation; apply a rebreathing mask to raise the PaCO2 further
A 27-year-old woman at 36 weeks of gestation suffers a witnessed cardiac arrest in the emergency department. CPR is started and the airway is secured. Two minutes into the resuscitation there is no return of spontaneous circulation. Which action is most appropriate?
Place the patient in a 30-degree left lateral tilt to relieve aortocaval compression
Reduce defibrillation energy by half to protect the fetus
Apply manual left uterine displacement and prepare for resuscitative cesarean delivery by about 4 minutes
Transfer the patient to the operating room before any surgical intervention
A 66-year-old man with diabetes presents with fever of 39.2 °C, left flank pain, a blood pressure of 84/50 mmHg, and a lactate of 4.1 mmol/L. CT shows an 8 mm obstructing left ureteral stone with hydronephrosis and perinephric stranding. He receives fluids, norepinephrine, and piperacillin-tazobactam. What is the most important next intervention?
Urgent decompression with a ureteral stent or percutaneous nephrostomy
Medical expulsive therapy with tamsulosin and analgesia
Immediate extracorporeal shock wave lithotripsy to fragment the stone
Continuing antibiotics alone with repeat imaging in 48 hours
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