Last week, actor Bill Paxton died as a the result of an ischemic stroke during heart-valve surgery. Every surgery has a risk of stroke, and every heart surgery has an even higher risk of stroke, but it’s still unusual to see an otherwise healthy 61-year-old die in the course of a heart valve surgery. As a recent study in Britain found, even among patients over 65-years-old, long-term survival is “excellent.” Patients over 65 who underwent aortic valve replacement generally had no difference in mortality at all for the first 8 years after surgery.

So what happened in Bill Paxton’s surgery? We deal with these issues all the time as medical malpractice lawyers.

Technically, a stroke during or immediately after a surgery is “perioperative stroke.” Perioperative strokes are one of the most common complications of all surgeries. In non-cardiac, non-neurological, non-major vascular surgery, up to 2% of patients suffer a perioperative ischemic stroke. Most of those patients have a complicating risk factor, like advanced age, a history of renal failure, or a history of stroke. In high-risk cardiovascular surgery, researchers have found that between 2% and 10% of patients suffer a stroke of some degree, with the highest risks found in mitral valve surgery and double or triple valve surgery.

For aortic valve surgery, which appears to be the type Bill Paxton was having, roughly 5% of patients suffer a stroke. But most of the patients who suffer a stroke during cardiac surgery have some other risk factor, like a high blood transfusion requirement, a history of cerebrovascular disease, a perioperative infection, an urgent surgery, or cardiopulmonary bypass lasting more than two hours. We don’t have too many details on Bill Paxton, but from what we do know, it doesn’t seem any of those were issues, either.

Indeed, the most shocking part about Bill Paxton’s case is that he apparently died during surgery. Only 5-15% of perioperative strokes occur during surgery (“intraoperatively”) or in the period immediately after surgery. Most of the time, postoperative strokes happen at least 24 hours after surgery. (See this study in Anesthesiology or this study in Anesthesia and Analgesia.) That leaves us with a lot of questions about the surgical management.

We start with the pre-operative issues. Most of the time, these issues involve pre-existing conditions, but it doesn’t seem Bill Paxton had any. Thus, the major question is: should he have been on anticoagulant or antiplatelet therapy? As a medical review in 2016 suggested,

In general, the risk of excessive perioperative bleeding is weighed against the risk of thromboembolism, though a clear, diametric clinical distinction is not always present. For patients on anticoagulation for conditions such as atrial fibrillation, the ACC/AHA Guidelines recommend discontinuation of anticoagulation for ≥ 48 hours for major surgery. The American College of Chest Physicians (ACCP) recommends continued perioperative anticoagulation for patients at high risk for venous thromboembolism. At this point, it is unclear if aggressive perioperative anticoagulation would reduce the risk of postoperative stroke, and further investigation would be of benefit for clinical decision-making. With regards to antiplatelet therapy, both observational and interventional data have demonstrated a cerebroprotective effect of aspirin in cardiac surgery patients.

That’s the sort of wishy-washy recommendation that’s typical of medical reviews, but in practice the question is usually a lot clearer. Patients who don’t have risk factors for excessive bleeding should generally be put on some sort of anticoagulant or antiplatelet therapy, even if just aspirin for cardiac surgery patients.

Moving on to the intraoperative issues, “hemodynamic stability” is key. That’s just a fancy way of saying that blood flow, pressure, and even glucose levels should be kept in check. Studies have shown that hypotension, like allowing arterial blood pressure to fall too far below the norm, increases the risk of stroke. Some studies suggest this happens when blood pressure falls 30%, others suggest it happens even with a fall of just 20%.

It doesn’t seem Bill Paxton made it to the “postoperative” period, when most strokes occur. In that period, the problems often relate to basic nursing. Did the patient become hypoglycemic? Did they receive appropriate anticoagulants or antiplatelets? Or, if a stroke happened, was it recognized and treated soon enough? When a person suffers a stroke outside the hospital, it’s often a challenge to get them the clot-busting drugs (like Alteplase IV r-TPA, the tissue plasminogen activator) or to perform a mechanical thrombectomy soon enough, but that shouldn’t be a problem in a hospital.

So how, exactly, did Bill Paxton get a stroke? We can’t know that without his medical records. Sometimes it’s hard to know that without an autopsy. But we can guess from the most likely possibilities. If his blood pressure went too low, then he could have suffered from hypoxia, or the reduced blood pressure could have made a clot more likely. As another possibility, air could have entered the blood stream, creating an air embolism, which functions the same as a clot. Or, he could have had a build-up of calcium or plaque in his aorta, and the surgery dislodged it, after which it traveled to his brain.