Medical Negligence: the causation challenge

It can be a challenge proving a causal link between a breach of duty and harm in personal injury cases. In medical negligence cases it can be a much more complex issue.

Even where the defendant admits negligence/breach of duty, if the claimant cannot prove on balance that the harm resulted directly from that breach – the claim is bound to fail. In other words, if the harm (or death) would have happened anyway in the absence of negligence, the claim will not succeed.

The ‘but for’ test as established in the 1969 case of Barnett has, for the most part, stood the test of time and is still relied on by the courts. That is to say, ‘but for’ the negligence/breach – would the claimant have suffered the pain and injuries complained of? Invariably, expert medical evidence – often, from a number of different experts – will be required to prove a causal link.

Three particular cases of note illustrate some of the challenges arising in clinical negligence claims where the issue of establishing a causal link is in issue.

The claimant in Marshall v Schrembi [2019] EWHC 283 was the husband of the deceased, Doreen, who died the morning after visiting her GP. Doreen had a history of pulmonary embolism and went to her GP who did not refer to the hospital. He sent her home saying she had probably pulled a muscle causing her chest pains. She collapsed the following morning and died soon after.

The GP admitted breaching his duty of care in that he should have referred her directly to the hospital, but he denied this caused Doreen’s death. The court said though the burden is on the claimant to prove causation, he did not have to prove the specific train of events or mechanism necessary to achieve Doreen’s survival – it was only necessary to prove she would have survived had she been sent to the hospital.

It ruled that had she been treated with thrombolysis (clot-busting treatment) by around three hours before she collapsed, she probably would have survived. Further, on the evidence the court concluded that at the time when Doreen should have presented at hospital, anybody rating her chances of survival would have put them at being very high. The husband’s claim was therefore successful.

The trial in AXO v Salisbury NHS Foundation Trust [2019] EWHC 1454 related to an injury claim on behalf of a prematurely born boy. Soon after his birth in 2008, he was negligently given an overdose of a muscle relaxant (of 10 times the normal dose) which is used to facilitate mechanical ventilation. This, it was claimed, caused brain damage leading to in cerebral palsy.

Breach of duty was not in issue but the defendant argued that the neurological injury was unrelated to the overdose itself. The court made clear that all the claimant had to prove was that the overdose was likely to have made a material contribution to the outcome. The fact that it might not be possible to prove exactly how it did so was not fatal to establishing causation.

Here, the court could not conclude that the overdose caused a greater reduction in the muscle tone than would have been caused by the therapeutic dose (the amount needed to treat a disease).

Mrs Justice Yip found that though rare, the particular type of brain damage here (PVL) can occur in premature neonates without any failing in care. On its full findings, she ruled that it appears that the boy’s PVL was more likely linked to the general complications associated with his premature delivery.

The evidence did not establish the necessary causal connection between the two, rather, the boy’s neurological injury is explained by his prematurity and “perinatal course”.

Finally, another case worth noting is Pomphrey v Secretary of State for Health and Anor [2019] 4 WLUK 483 in which the claimant suffered serious complications following spinal surgery. Causation was somewhat of a side issue but it came to the fore during the course of case.

Here, a breach of duty of care was not admitted, but the issue of causation arose particularly in relation to the applicability of the principle in Chester v Afshar (2004). The judge found that there was a breach of duty in respect of the delay between the claimant seeing the consultant neurosurgeon and the date on which the actual operation took place. The allegedly negligent period of delay was found to be 10 days.

The claimant then argued unsuccessfully that had the surgery been earlier, on the balance of probabilities, the same complication would not have occurred. But the judge said the surgery would have taken place at the same surgery in the same hospital and with the same surgeon - the only difference being 10 days.

The judge stated that “a general risk of a particular complication which is based on the statistical cohort of a large number of different surgeons (and usually containing a range of different causes and circumstances) must yield to more refined evidence of the risk of the complication arising from the technique of the particular surgeon undertaking the same operation on different days. So the focus must be on the particular operation in question”.

This was different to Chester which concerned a patient not being advised by the surgeon about the 1 per cent chance of being permanently paralysed. As the defendant had argued, the risk that the claimant would sustain the injury concerned was a risk inherent in that surgery. The 10-day delay in operating did not alter the magnitude of the risk; the injury was liable to occur whenever the surgery was performed.

The judge said the delay was effectively an “irrelevant detail” having no bearing on the probability of that injury occurring (unless the claimant’s condition had deteriorated in that period).



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