Why Perfusionists Get Sued: Air Embolism, the Clotted Circuit, and the Under-Perfused Brain

By John Mahoney · July 2026 · 9 min read

Perfusionists are almost never a household name in a med-mal file, and the specialty produces very few claims — there are relatively few practitioners, and they work inside a cardiac-surgery team where the surgeon and anesthesiologist absorb most of the litigation. But the perfusionist runs the cardiopulmonary bypass circuit that keeps a patient alive with a stopped heart, and when that circuit fails, the injury is immediate, global, and often catastrophic: an arterial air bolus to the brain, a clotted circuit throwing emboli, a period of inadequate flow that infarcts the brain or kidneys. Perfusion is the definition of a low-frequency, maximum-severity specialty, and the files that reach it tend to involve death or profound neurologic injury. This guide explains where perfusion liability actually lives, the cannot-miss failures behind it, and what separates a strong case from a weak one — for plaintiff and defense med-mal attorneys.

Disclaimer: This article is for informational purposes only and does not constitute legal advice. Perfusion practice is governed by consensus standards and by institution-specific protocols, and responsibility on bypass is shared among the perfusionist, surgeon, and anesthesiologist; treat the patterns below as directional, verify against the controlling jurisdiction and the applicable perfusion standards, and value any individual case on its own record.

The Allegations

Perfusion claims cluster into a circuit-catastrophe group, driven by an acute failure of the bypass system, and a management group, driven by how the run was conducted and monitored:

• Arterial air embolism — the signature perfusion catastrophe, where air enters the arterial line and reaches the brain, causing stroke or death, typically traced to a low reservoir level, a missed bubble detector, a reversed line, or an unrecognized circuit-integrity problem.
• Inadequate anticoagulation and circuit thrombosis — failure to maintain the activated clotting time in range, allowing clot to form in the circuit and embolize, or a heparin/protamine timing or reversal error.
• Inadequate perfusion — low flow or low pressure — a run conducted at flows or pressures that under-perfuse the brain and organs, producing watershed stroke, hypoxic-ischemic injury, or acute kidney injury.
• Oxygenation and gas-exchange failure — an oxygenator problem, gas-line error, or ventilation failure on bypass causing hypoxia or hypercarbia that was not recognized and corrected.
• Temperature-management errors — cooling and, especially, rewarming errors, where over-rapid or overshoot rewarming is associated with neurologic injury.
• Cardioplegia and equipment-response failures — inadequate delivery of myocardial-protection solution, or failure to recognize and respond to a pump, line, or device malfunction, and medication errors delivered through the circuit.

The structural point is that perfusion is almost entirely a maximum-severity field, but liability is deeply shared. Nearly every claim is really about whether the perfusionist's conduct, as opposed to the surgeon's, the anesthesiologist's, or the patient's own physiology, caused the injury — so an intake must be triaged first on the mechanism and then on whose hands controlled it.

The Cannot-Miss Failures

The failures that drive perfusion litigation are:

• Massive arterial air embolism. The most feared complication: air pumped into the arterial circulation and delivered to the brain. The recurring failures are a reservoir allowed to run low, a bubble-detector or level-sensor safety device disabled or ignored, a line connected in reverse, or a failure to de-air the circuit — all events the safety architecture is designed to prevent.
• Loss of anticoagulation and circuit clot. If the activated clotting time is not monitored and kept in range, clot forms in the circuit and can embolize or consume the coagulation system. Failing to check or act on the ACT is a recurring, high-consequence lapse.
• Inadequate flow or perfusion pressure. Running the pump at flows or pressures that fail to perfuse the brain and organs — or failing to respond when pressure drops — produces global ischemic injury, watershed stroke, and kidney failure that appear after the case.
• Unrecognized oxygenator, pump, or line failure. A device or circuit malfunction that is not detected and corrected quickly enough — the standard of care is not perfection of equipment but timely recognition and response.
• Rewarming and temperature errors. Over-rapid rewarming or hyperthermic overshoot, associated with neurologic injury, where the temperature record shows the trajectory.
• Cardioplegia delivery failure. Inadequate or mis-delivered myocardial-protection solution, contributing to poor cardiac protection and post-bypass ventricular dysfunction.

The single most actionable screening question is what the perfusion record — the pump-run sheet — shows minute by minute: the flows, pressures, ACTs, blood gases, temperatures, reservoir levels, and alarms, and whether a deviation was recognized and corrected or allowed to persist. Perfusion is unusually well-instrumented, and the record is the case.

What Separates a Strong Case from a Weak One

The same factors grade the file, and the framing is useful to both sides. Perfusion cases live in an unusually objective record: the pump-run sheet with its serial flows, pressures, ACTs, and blood gases; the temperature log; the alarm and event entries; the checklist and safety-device documentation; and the anesthesia and operative records that run in parallel. Because responsibility is shared, causation is the battleground — whether the injury flowed from a perfusion deviation or from the surgery, the patient's disease, or a decision made by another member of the team.

What makes a perfusion case strong (plaintiff) / dangerous (defense)

• A documented arterial air event — a low reservoir, a disabled or ignored bubble detector, a reversed line — followed by stroke or death consistent with cerebral air.
• An ACT that ran out of range without correction, or a heparin/protamine error, followed by a thromboembolic injury.
• A run at flows or pressures the standard would not accept, or a prolonged low-pressure interval, followed by watershed stroke or acute kidney injury.
• An equipment or circuit malfunction that the record shows was recognizable earlier than it was addressed.
• A rewarming curve showing over-rapid or overshoot rewarming preceding neurologic injury.

What makes a perfusion case weak (plaintiff) / defensible (defense)

• A pump run documenting in-range ACTs, adequate flow and pressure, appropriate gases, controlled temperature, and functioning safety devices, with the injury attributable to the disease or the surgery.
• A completed pre-bypass checklist and functioning bubble detector and level sensor, framing any air as vanishingly unlikely to be the mechanism.
• A prompt, documented recognition and correction of any deviation, showing the perfusionist responded within the standard.
• A causation picture where the neurologic or renal injury is better explained by embolic disease, hypotension outside the perfusionist's control, or a surgical event.
• An objective, contemporaneous perfusion record consistent with standard practice and the applicable consensus guidelines.

Perfusion rewards a fast triage. Because the specialty is almost purely maximum-severity, the file lives or dies on the pump-run record and on the causation allocation — whether the injury traces to a perfusion deviation the record captures, or to the surgery and the patient's physiology. Whichever side you are on, grading the file means reading the run minute by minute and pressure-testing the expert — a perfusionist, alongside cardiac-surgery and anesthesiology experts — who will carry it.

Bottom Line

Perfusionists get sued rarely, but almost every claim that reaches them is a death or a devastating neurologic injury, because they control the machine that substitutes for the heart and lungs. The catastrophes are specific and mechanism-driven: air to the brain from a low reservoir or a defeated safety device, a clotted circuit from lost anticoagulation, a brain or kidneys starved by inadequate flow, an unrecognized equipment failure, and a rewarming curve that injured the brain. The cannot-miss facts are the out-of-range ACT never corrected, the low reservoir and ignored bubble detector, the sustained low-flow interval, and the deviation the pump-run record shows was recognizable. Whether you are screening these cases for the plaintiff or defending them, triage first on the mechanism and the causation allocation, and grade the file on the perfusion record and the safety-device documentation, not on the tragic outcome alone.

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