Air Bubble Alert: When Kidney Stone Removal Goes Wrong
"A rare complication during a common procedure highlights the dangers of paradoxical air embolisms and the importance of vigilance."
Kidney stones, a common ailment, often require percutaneous nephrolithotomy (PCNL), a minimally invasive procedure to remove them. While generally safe, PCNL carries rare but serious risks. One such risk is paradoxical air embolism, a condition where air bubbles enter the bloodstream and travel to the heart and brain, potentially causing life-threatening complications.
A recent case highlights the importance of awareness and preparedness for this rare event. A 76-year-old man undergoing PCNL for a kidney stone experienced a paradoxical air embolism, leading to a cascade of complications, including a myocardial infarction (heart attack).
This article delves into the details of this case, exploring the causes, symptoms, diagnosis, and management of paradoxical air embolism during PCNL, emphasizing the need for vigilance and prompt intervention to ensure patient safety.
How Rare Is Air Embolism?
A study of 164 patients who underwent percutaneous nephrolithotomy (PCNL) reported that seven patients (4.25%) required more than one tract for complete stone removal; that figure is not an air-embolism rate. The study describes using an air pyelogram for initial access, while another report notes that air embolism and migration of stone fragments through the venous system causing pulmonary embolism have been reported rarely in the literature. The available figures therefore describe the procedure cohort and related outcomes, not the incidence of air embolism. (Reference URL 1; Reference URL 2)
Evolution of Percutaneous Stone Removal
A historical review reports that Rupel and Brown removed the first kidney stone through a surgical nephrostomy tract in 1941. Fernström and Johansson developed a percutaneous tract in 1976 specifically to remove kidney stones through the mature tract, and Smith and colleagues later developed reliable methods for percutaneous entry to the renal pelvis and ureter. Subsequent development of lithotripsy devices and introduction of the holmium laser improved stone fragmentation and clearance, while wider clinical use of PCNL enabled characterization of stone-free rates and complications.
What Happened? A Step-by-Step Breakdown
The patient was positioned prone, and access to the right kidney's collecting system was achieved using fluoroscopic guidance. Air was insufflated to visualize the collecting system, but despite repeated attempts, visualization remained inadequate. A total of 240 mL of air was introduced.
- Right-to-Left Shunt: This occurs when blood flows from the right side of the heart to the left, bypassing the lungs. In this case, it was likely due to a previously undiagnosed patent foramen ovale (PFO), a small opening between the heart's upper chambers that usually closes after birth.
- Air Embolism: The air introduced during the PCNL procedure entered the venous system and traveled to the right side of the heart. Due to the PFO, the air crossed over to the left side of the heart and then to the systemic circulation, potentially affecting the brain and heart.
- Myocardial Infarction: The patient subsequently experienced a self-limited ventricular tachycardia (rapid heart rate) and electrocardiogram changes indicative of a heart attack.
How Air May Enter the Circulation
A PCNL case report says vascular air embolism usually occurs after pyelography using air, identifying this as the most relevant factor in those cases. It also proposes that a holmium laser can create cavitation during stone ablation: high laser power lowers fluid pressure and may release air dissolved in the fluid. In a comparative study of air versus contrast pyelograms for initial puncture access, the authors reported no air-embolism or cardiopulmonary complication in their own study, while noting that a few earlier studies had reported such complications in the air-pyelogram group.
Air Embolism Across Procedures
A report on venous air embolism describes it during PCNL with air pyelography, during transurethral resection of the prostate, and rarely during holmium laser enucleation of the prostate. That report presents a rare case during retrograde intrarenal surgery (RIRS), showing that the complication has also been documented in a different kidney-stone procedure. Another publication reports a paradoxical air embolism during PCNL in a patient with a patent foramen ovale and describes it as the first such report known to its authors.
The Takeaway: Vigilance and Preparedness are Key
This case underscores the importance of being aware of the potential for paradoxical air embolism during PCNL, particularly in patients with risk factors such as a PFO. Although rare, this complication can have serious consequences.
Expert Perspective on Dialysis Air Embolism
A UK nephrology and acute-medicine expert-witness resource discusses clinical negligence claims involving air embolism during haemodialysis. Its stated focus includes breach of duty, causation, and standards of care. The source description does not provide case counts, clinical outcome data, or a specific conclusion about the standard of care.
Symptoms of air embolism can include sudden drops in blood pressure, decreased end-tidal CO2, tachycardia, and neurological changes. Prompt recognition and intervention, including immediate termination of the procedure, resuscitation, and TEE, are crucial for successful management.
While hyperbaric oxygen therapy can be beneficial, this patient was successfully managed with supportive care in the ICU. This case serves as a reminder to healthcare professionals to maintain vigilance and be prepared to manage this potentially fatal complication effectively.