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ABPS Anesthesiology (BCA) study materials
ABPS Anesthesiology (BCA) study resources

Sudden ETCO2 Collapse During Laparoscopic Nephrectomy

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Sudden ETCO2 Collapse During Laparoscopic Nephrectomy

A 58-year-old woman (BMI 27) is undergoing laparoscopic donor nephrectomy under general anesthesia with desflurane and a 14-gauge right internal jugular central line placed after induction. Ventilation: tidal volume 500 mL, PEEP 6 cmH2O, FiO2 0.5; baseline ETCO2 36 mmHg, SpO2 99%, BP 118/70 mmHg, HR 72. During hilar dissection with CO2 insufflation at 15 mmHg, the ETCO2 suddenly falls to 12 mmHg over 30 seconds, then to 8 mmHg. SpO2 falls to 88%, BP to 74/42 mmHg, and HR rises to 128. Peak airway pressure is unchanged at 22 cmH2O, and the capnogram still shows a normal rectangular shape that is simply much smaller. The surgeon reports no major bleeding and has just opened the renal vein.

1. What is your differential, and what are your first five actions?

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Differential, in order of likelihood:

  1. Venous gas embolism (CO2 or air) through the opened renal vein
  2. Acute hemorrhage or caval compression causing low cardiac output
  3. Pulmonary embolism
  4. Anaphylaxis (unlikely without rash, wheeze, or airway pressure change)
  5. Tension pneumothorax or bronchospasm (argued against by an unchanged peak pressure and a normal waveform)

A circuit disconnect or obstruction would abolish or distort the waveform, so the preserved rectangular shape points to reduced pulmonary blood flow.

First five actions:

  1. Tell the surgeon to stop insufflation, flood the field with saline, and compress the renal vein; release pneumoperitoneum.
  2. Switch to 100% oxygen and hand-ventilate to assess compliance.
  3. Aspirate the central line (right atrium) while starting vasopressors and a fluid bolus.
  4. Call for help and bring in a TEE probe and a second large-bore IV.
  5. Check the ECG for right heart strain, send an arterial blood gas, and look for a source of bleeding.

Keep the patient supine; avoid raising intra-abdominal pressure further. If arrest occurs, begin CPR and prepare for prolonged resuscitation because CO2 emboli are resorbable.

2. How would you confirm the diagnosis intraoperatively, and how do the available monitors help?

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Confirmation:

  • TEE: the most useful tool; it can show air in the right atrium or ventricle, right ventricular dilation, and reduced left ventricular filling, and it can guide aspiration.
  • Precordial Doppler: sensitive for small volumes of air but nonspecific and often unavailable.
  • Sudden fall in ETCO2 with a preserved waveform plus hypoxemia and hypotension is the classic triad; a fall in ETCO2 without hypotension suggests a smaller embolus.
  • Arterial blood gas: increased dead space with a rising PaCO2–ETCO2 gradient and hypoxemia.
  • Central venous pressure: a rise is described but is unreliable; do not wait for it.

What does not help: a chest radiograph is slow and insensitive; pulmonary artery catheter placement is impractical in this crisis.

Distinguishing from pulmonary thrombus embolism: both cause a fall in ETCO2, but the temporal link to opening the renal vein, the suddenness, and TEE findings favor gas embolism. Hemorrhage would show a falling ETCO2 with tachycardia and a falling CVP, and the surgical field would show blood. Anaphylaxis would raise airway pressure. Reassess the surgical field and the monitor trend together rather than relying on a single number.

3. If the patient deteriorates to cardiac arrest, how should resuscitation be modified?

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Standard ACLS with these additions:

  • 100% oxygen, stop insufflation, and release pneumoperitoneum to improve venous return
  • Chest compressions supine; do not attempt full left lateral positioning during compressions, as it compromises CPR quality. A slight left tilt may be used if it does not impair compressions.
  • Aspirate the central line again; if a multiorifice catheter is in the right atrium, it can retrieve a meaningful volume of gas
  • Give epinephrine early for right ventricular failure and consider an infusion; avoid excessive fluid that distends the failing right ventricle
  • Use TEE if available to confirm gas in the right heart and to guide management
  • Be prepared for a prolonged resuscitation: CO2 emboli dissolve, and good-quality CPR can bridge to recovery

After return of circulation: ICU care, echocardiography, lung-protective ventilation, neurological assessment, and a discussion with the surgical team about the donor kidney and the timing of any further procedure. Debrief the team about the rapid sequence of recognition and decompression.