Nadia Krueger-Young examines complex causation issues in medical negligence claims.

In the well-known case of Chester v Afshar [2004] UKHL 41, the claimant’s risk of suffering cauda equina syndrome during the surgery she underwent was 1-2%. If she had had the surgery, say, three months later, the risk would have been the same. It was therefore held by a majority in the House of Lords that Miss Chester could not show that the risk of the injury would have been any different had the operation been carried out on a different occasion. Even though the risk of injury was so small, it was held that it would have occurred regardless of when the surgery had taken place. In other words, the change in the date of the surgery had not increased the risk of injury. This meant ‘but for’ causation would fail.

To allow the claimant to succeed, a ‘modest departure’ from traditional causation principles was needed. This was achieved by the House of Lords finding an ‘intimate connection’ between the surgeon’s breach of duty in failing to warn of the risk of cauda equina syndrome, and the fact that Miss Chester’s injury resulted from the eventuation of that very risk.

Subsequently, some claimants argued that Chester established a free-standing principle entitling injured parties to compensation where the injury was intimately involved with the duty to warn, and the injury was the product of the very risk the patient should have been warned about when they gave their consent. However, the Court of Appeal confirmed in Duce v Worcestershire Acute Hospitals NHS Trust [2018] EWCA Civ 1307 that this would amount to a wholesale disapplication of conventional causation principles in consent cases. To succeed, the claimant must establish that they would not have undergone the operation or treatment at the time they did, and that the relevant risk was the same or less at a later time.

Crossman v St George’s Healthcare NHS Trust

In 2016, Stewarts acted for the claimant in Crossman v St George’s Healthcare NHS Trust [2016] EWHC 2878 (QB), on those very principles (alongside Anna Beale of counsel, now Anna Beale KC). In that case, the claimant had been warned of the risks of nerve injury occurring during foraminotomy surgery (which was later converted to a laminectomy) in the order of 1%. However, importantly, surgery was to be deferred until after physiotherapy had taken place. The admitted negligence in the case was that, instead of surgery being deferred and physiotherapy taking place, the claimant was, in error, put on a waiting list for surgery straight away.

Although the operation was not performed negligently, the claimant sustained a nerve root injury, causing permanent weakness to his right arm, which was devastating to his job as a plumber. It was agreed that if he had had the surgery three months later, after physiotherapy, the risk would have been the same. The circumstances were, therefore, as in Chester v Afshar. The case was not, however, won on the ‘modest departure’ of the ‘but for’ position as in Chester. Instead, it was won on conventional ‘but for’ causation principles. It was found that the combination of causes that led to the nerve root injury probably would not have occurred in the same way on a different occasion. Therefore, the risk was not more likely than not to have been realised on a different date. The claim was won on conventional ‘but for’ causation, and for the same reason that conventional ‘but for’ causation in Chester v Afshar failed.

A more recent case study

Almost 10 years later, the same legal team, Nadia Krueger-Young of Stewarts and Anna Beale KC of Cloisters, applied a similarly complex ‘but for’ causation argument to succeed in a claim involving the risk of suffering an intraoperative stroke.

The claimant in this case suffered a stroke during re-do aortic valve surgery, which caused him a severe brain injury with near complete loss of eyesight, and short-term memory and cognitive difficulties. The stroke occurred, the claimant’s team alleged, because of a delay in diagnosis of infective endocarditis. This delay, they argued, worsened the infection and led to the development of an aortic valve root abscess.

The background to the case was that the claimant was born with a bicuspid aortic valve. Aortic valves usually have three flaps that prevent blood from flowing backwards into the heart. When an aortic valve has only two flaps, it increases the risk of blood flowing backwards into the heart, a condition known as aortic valve regurgitation. Aortic valve regurgitation can cause the heart to become enlarged and to work harder, potentially causing heart failure.

The claimant only realised he had a bicuspid aortic valve when he started to become unusually out of breath when exercising. He was advised to undergo an aortic valve replacement, which he did. However, he was never told that following his valve replacement, he was at an increased risk of developing endocarditis, a serious, often bacterial, infection of the heart’s inner lining or valves. Nor was he informed about the symptoms of endocarditis or what he should do if he developed those symptoms.

When the claimant developed these symptoms (akin to the flu) almost a year later, he assumed he had the flu. His symptoms seemed to get better and then worse. He also developed a swollen and red foot, despite the fact that he had not been exercising or sustained an injury. He attended an NHS walk-in centre, which referred him to vascular doctors, who dismissed his symptoms and diagnosed him with a sprained ankle. Eventually, after becoming more unwell, he was seen again at a different hospital, and investigations confirmed endocarditis. By this time, several months had passed, and investigations showed that the endocarditis had also caused an abscess around the root of his aortic valve.

The claimant required aortic valve replacement surgery (his second such surgery). That second operation was not successful, and a third, to replace the aortic valve, was required. In that third operation, the claimant suffered the stroke that caused his devastating brain injury.

The claimant alleged that the second operation, which would always have been required but would have been much less complicated but for the delay and the abscess formation, would have been successful, and the third further operation would not have been required at that time. If the third operation had not taken place at that time, he would not have suffered the stroke.

The breach of duty arguments were straightforward. The claim against the first defendant was that it failed to explain to the claimant the symptoms of infective endocarditis, which NICE guideline 64 says should be explained to patients undergoing aortic valve replacement. Breach of duty was denied, and no real explanation was provided as to why any reasonable cardiothoracic surgeon and nurse would not take the simple step of explaining the symptoms of this potentially fatal condition. These patients are at greater risk as a result of valve replacement, and it is vital to inform them of the symptoms so that they can seek early treatment if required, which greatly improves their prospects of survival.

The claim against the second defendant was based on the failure to recognise the claimant’s foot embolism, which it was agreed would have resulted in the diagnosis of infective endocarditis at that time. It was agreed that if these alleged breaches had not occurred by either defendant, his infective endocarditis would have been diagnosed earlier, and he would not have developed an aortic valve root abscess.

In relation to factual causation, it was agreed that the claimant would have always needed a third aortic valve replacement. The reason being that a tissue aortic valve, which the claimant had opted for, only lasts for around 10 years before requiring replacement. The key issue in the case, therefore, was whether the claimant could prove he would not have suffered a stroke whenever his third surgery took place.

The risk of the claimant suffering his stroke in the first place was very low, around 1-3%. So, on the balance of probabilities, he should not have suffered his stroke when he did. Therefore, a normal balance of probabilities argument would have failed. The claimant therefore argued that the delay in diagnosis caused a more difficult and friable surgical field and, together with the second and third surgeries being in quick succession, had doubled the risk of injury. The claimant’s cardiothoracic expert confirmed that the risk had probably been increased to 3-5%, from 1-3%, due to the negligence, a bare doubling of the risk.

Most (but not all) of the case law suggests that the risk must be more than doubled in order to succeed on a balance of probabilities assessment. The fallback position was to rely on the arguments, as set out in Crossman above, that it was a combination of causes that led to the stroke, and those probably would not have occurred in the same way on a different occasion.

Ultimately these arguments were not tested in court. Instead, the claim settled just before trial, on a reduced liability basis to reflect the risk on both sides, of the arguments succeeding or failing. The claimant secured compensation with a seven-figure sum, to reflect the severity of his injuries, notwithstanding the liability concessions made.

This case, and those before it, serve as a reminder that, in medical negligence cases, causation is often the most difficult part of the claim to prove. However, it is always worth pushing the boundaries of what conventional ‘but for’ causation means, to achieve the justice our clients deserve.

Nadia Krueger-Young is a partner in the Medical Negligence team at Stewarts.

This article was was originally published by PI Focus.