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Legal case

Causation and material contribution in birth injury claims — a victory for claimants?

CNZ v Royal Bath Hospitals NHS Foundation Trust (1) and The Secretary of State for Health and Social Care (2)

This is an important decision which will potentially have a significant impact on the approach to birth injury claims. A note of caution is that this is a first instance decision and the first defendant will be mounting an appeal.

The claimant in CNZ was a second twin born in 1996 and subsequently diagnosed with profound disabilities due to acute profound hypoxia. The claimant’s mother had a significant obstetric history. She had stated her preference not to have either artificial rupture of the membranes (ARM) or an epidural and the claimant alleged that she was refused an elective Caesarean Section (ECS) in the antenatal period. Following the vaginal delivery of twin one, the claimant’s mother requested a Caesarean Section (CS) but the junior doctor in attendance, following a discussion with the consultant, planned to proceed with ARM in theatre. After further discussions and the claimant’s mother insisting on a CS, this was agreed. Mr Justice Ritchie found that the junior doctor (a registrar) recommended ARM to the consultant without reciting the parents’ choice for no ARM and the unavailability of epidural anaesthesia, that she omitted to mention an attempted and failed EA and ultimately the consultant was not adequately informed. After the discussion with the consultant, the parents were informed that the plan was for ARM and the registrar failed to explain the procedure of high ARM to the parents including the risks, failed to recommend CS and failed to agree to the parents’ choice of CS. In addition to these failures in care, Ritchie J found that the registrar acted slowly and with no sense of urgency.

An interesting feature of the judgment is that the claimant succeeded on liability (on a traditional Bolam negligence and ‘but for’ causation basis), but the judgment goes considerably beyond this. Some parts of the judgment are therefore “obiter” and not binding. In particular, the claimant succeeded with her claim that there was a delay in delivery of the claimant following the delivery of the first twin and that this led to avoidable harm.

Extending Montgomery

The decision in Montgomery v Lanarkshire in 2015 was itself hailed as a landmark which changed the approach to informed consent. Montgomery redefined the standard for informed consent moving this firmly away from the well-established principles set out in Bolam to focus on material risk. Montgomery also marked a shift from the more paternalistic doctor-based approach to a patient-based standard of care.

Montgomery may have been decided in 2015 but was based on events that went back to 1999 and so logically the standard would apply at least as far back as this. Indeed it is a common law principle that the courts do not make the law but apply it and therefore this and other decisions apply irrespective of when the events occurred.  Ritchie J in CNZ considered just how far back the decision should be taken and concluded that the Montgomery principles applied in 1996but linked this to the rise of the internet and patient autonomy suggesting that it might not apply in the 1960s or 1970s. It was not necessary for the court to consider whether Montgomery has the potential to extend to treatment prior to 1996, but this cannot be ruled out and the door is open to test how far back it could extend. For birth injury claims, in particular, where limitation is often open ended, the implications are potentially significant.

Though it was argued in CZC that elective Caesarean Section (ECS) was not a reasonable treatment option for twins in 1996 and not ‘standard management’, this was rejected by Ritchie J who was troubled by the apparent contradiction where it was also accepted that, had the claimant’s mother insisted on ECS (which she did not), the first defendant would have eventually agreed to this. Ritchie J referred to the ‘inherent illogicality’ of this situation. On the facts he found that there was a discussion with the claimant’s mother which included ECS and she was consented for induction, so this part of the claim ultimately failed but the judgment is nevertheless relevant and is likely to give clinical negligence lawyers pause for thought.

Though it has been suggested that the judgment also extends the scope of Montgomery to ‘imminent delivery’ cases where the existing approach has been to treat the subject of informed consent as distinct from antenatal consent, we are not sure this was the court’s intention or indeed that this is the conclusion to take away from the judgment. Ritchie J quotes Martin Spencer J from his judgment in ML v Guys and St Thomas [2012] EWHC 2010:

“However, the situation seems to me to be quite different where a woman is in labour and in extreme pain. …such a request is frequently heard and is more a cry for help because of the pain. In those circumstances, the appropriate response, as here, is to deal with the pain and then review the matter and see whether the request was or was not "serious". By that I do not intend to suggest that any request for a caesarean section is not serious but an obstetrician or a midwife would be failing in their duty to both mother and baby if they simply took every such request at face value without exploring and addressing the underlying reason. I regard it as significant that, in her statement of 1 November 2010, SL referred to feeling "Much more coherent" after she had been given the epidural. This is a tacit admission that, before the epidural and given the pain she was in, she was less than coherent and I suspect this will be the case for many women undergoing labour for the first time or, indeed, not for the first time. It would in fact be impossible to have the kind of discussion of risk and benefit envisaged ….with a woman who is not wholly coherent and thinking straightforwardly and logically because of the extreme pain she was in and it could be regarded as irresponsible for a midwife or obstetrician to attempt to have such a discussion with a woman before her pain had been addressed. It seems to me that this situation is qualitatively different to the situation in the ante-natal clinic where a request for a caesarean section is made.”

Ritchie J found that the difference between CNZ and ML is that in CNZ, the claimant’s father was in the delivery room and able to speak for the claimant’s mother and they both chose CS. In addition, the claimant’s mother clearly wanted CS as she made clear just 9 minutes later. This does not so much extend the scope of informed consent to imminent delivery, but it does mean that the merits of a claim will require a careful analysis of the facts on a case by case basis and it is progress for claimants.

Causation and material contribution — A further victory for claimants?

Ritchie J has considered in some detail in his judgment the law as it has evolved in relation to material contribution and causation. However, having heard all the evidence on the matter, he determined that the duration of the acute profound hypoxic ischaemia was a likely 16 minutes of which 6.5 minutes was avoidable. On the conventional analysis, since the first 10 minutes would be non-damaging, all of the injury was caused by the negligent hypoxia and on the conventional ‘but for’ causation analysis, the claimant is entitled to 100% damages.

Ritchie J did not stop there though…..

Every minute really does count in birth injury

But what if some but not all of the damaging hypoxia had been avoided? On the conventional analysis, acute profound hypoxic ischaemia only starts to cause damage after 10 minutes. In CNZ, the claimant should have been delivered in this non-damaging window. Ritchie J went on to consider what his conclusion would have been if the claimant had been born earlier but beyond the 10 minute ‘cut off’ and he found that every minute does count. The agreed expert evidence was that every minute of acute profound hypoxia over the first 10 minutes caused increasing or incremental brain cell deaths and that the damage minute by minute was ‘more than de minimis’. In addition, each minute caused increased functional outcome disability and injury.

However, to assess quantum, this required an analysis of what the functional outcome would have been but for the negligent hypoxia. The paediatric neurologists could not answer this question. The claimant’s expert gave evidence that it is not possible to advise on the functional outcome with any scientific accuracy. The first defendant’s expert advised that it was possible but only by using 5 minute aliquots. Ritchie J was troubled by this dilemma because the first defendant (or any defendant) should only be liable for the damage it has caused, but there are evidential challenges to that approach.

Redefining material contribution

This leads on to consideration of material contribution. If the claimant can prove that the breach made a material contribution to the claimant’s injury which was more than de minimis, damages are to be awarded. Material contribution and divisible and indivisible injuries is an often-ill-understood concept in clinical negligence. It is best understood in the context of disease as explained in Sienkiewicz v Grief (UK) Ltd [2011]: many diseases are caused by invasion of the body by an outside agent. The disease has a single trigger and is indivisible. Other diseases can be dose-related. Ingestion of the agent that causes the disease operates cumulatively so that after a threshold is passed, it causes the onset of the disease. An example is lung cancer caused by smoking where the disease itself is indivisible. The severity of the disease once it has been initiated is not related to the degree of exposure to cigarette smoke. More commonly, diseases where the contraction is dose-related are divisible. The agent ingested operates cumulatively first to cause the disease and then to progress the disease. Thus, the severity of the disease is related to the quantity of the agent that is ingested. Asbestosis and silicosis are examples of such diseases.

When dealing with an injury which is divisible, a defendant is only liable for the negligent injury. Medical science cannot always explain, however, the extent to which a breach of duty has contributed to the outcome of a divisible injury. Where a defendant is found to have caused or contributed to an indivisible injury, they will be held liable in full even where there may be other contributing causes.

In CNZ Ritchie J similarly made a distinction between trigger injuries and dose-related injuries. Brain damage caused by acute profound hypoxic ischaemia is not, he said, a trigger disease. It is dose-related and thus a divisible injury and one to which material contribution applies. However, the symptoms and / or functional outcome from the exposure to the hypoxia may be indivisible and may apply to the functional outcome caused by one or more minutes of acute profound hypoxic ischaemia.

Ritchie J considered whether the functional outcome in CNZ could be divided and if it were possible to say what level of injury would have been suffered in any event. If so, should this be apportioned? While he found himself agreeing that apportionment would be the fair approach, that is to apportion damages on a percentage-based approach (taking the relative durations of the hypoxia caused by the breach compared with that which would have been suffered in any event), he accepted that in practical terms, such an apportionment would likely be impossible. On that basis he concluded that in law, if there is a scientific gap making proof of causation of functional outcome and quantification impossible (this must truly be impossible as opposed to merely difficult), the claimant will recover 100% of the damage they have suffered so long as the claimant can prove that the breach made a material contribution to the functional outcome. This is relevant not only to birth injury claims but to any claim where the degree of exposure to damaging effects is likely to lead to a worse outcome (i.e. cauda equina, sepsis).

Aliquots — a thing of the past?

The Aliquot theory is a method of applying disability using the duration of the hypoxic insult as the yardstick i.e., a person exposed to 10 – 15 minutes of acute profound hypoxic ischaemia will have mild to moderate disability; 15 – 20 minutes exposure means the disability will be more severe. Dr Rosenbloom, paediatric neurologist for the first defendant, has used this for many years and it is a theory many other experts have followed and quoted in their own reports. However, the claimant’s expert was uncomfortable with this ‘best fit’ approach because functional ability is not predictable and every person with cerebral palsy is a unique individual. Why would parties need to instruct 10 or more experts to assess the claimant’s needs in every cerebral palsy claim if we can predict their prognosis based on the duration of exposure to damaging hypoxia?

Dr Rosenbloom gave evidence that the court could and should apportion damages if the court were to find that that part of the profound hypoxic ischaemic damage was caused by negligence and part would have arisen in any event. However, he was also clear that his Aliquot theory only works if the court takes chunks of 5 minutes, not less. In chunks of less than 5 minutes, apportionment is impossible. Ritchie J considered that on a logical analysis the Aliquot theory falls apart. Where the total duration of hypoxia is 20 minutes (10 of which were damaging) and the negligent hypoxia is 5 minutes, using the Aliquot theory, the claimant would be in the moderate category and the damages would be assessed on the difference between the actual symptoms and the symptom pattern set out in the mild category. However, if the negligent hypoxic exposure was only 3 minutes, that would still make a material contribution to the extent and severity of the claimant’s brain injury but apportionment would not be possible in relation to functional outcome so recovery would be 100%, which is illogical.

Ritchie J further rejected the Aliquot theory because there was simply not enough evidence (for example, a cerebral palsy database) to support the theory. It is perhaps of interest though that he was nevertheless happy to accept the conventional analysis that no harm will come from 10 minutes of exposure to acute profound hypoxic ischaemia!

Conclusion

This is an important judgment for claimants and defendants alike. It has the potential to change the approach to birth injury claims where delivery could have been achieved as little as 1-2 minutes sooner and extends the scope for informed consent, making it absolutely clear that in claims where the court is judging the standard to be applied from 1993 onwards, Montgomery applies and not Bolam. It is, however, a first instance decision and we await any further guidance from the Court of Appeal if an appeal is allowed.

For further information or any queries regarding clinical negligence you can contact your usual Weightmans contact or our health and care solicitors.

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