AXO v Salisbury NHS Foundation Trust

In a claim involving an indivisible medical injury, the claimant must establish on the balance of probabilities that the defendant’s breach made a material contribution to the injury. The claimant need not prove the precise mechanism of causation, but must prove a causal connection rather than rely on temporal association alone. A significant deterioration occurring after a negligent drug overdose may have alternative explanations, including the patient’s underlying condition and other treatment. Where the evidence does not show that the overdose caused or materially contributed to damaging hypotension or a subsequent hypoxic episode, causation is not established.

The claimant, a child born prematurely, developed cerebral palsy after receiving a tenfold overdose of pancuronium bromide shortly after birth. The defendant admitted negligent administration of the overdose, but disputed that it caused or materially contributed to the claimant’s periventricular leukomalacia and resulting neurological injury.

The claim focused on two alleged damaging episodes: hypotension recorded after the overdose and a further episode around the claimant’s transfer to another hospital, including accidental extubation. The central issue was whether either episode was causally linked to the overdose.

1. Applicable test. The injury was indivisible. The applicable question was whether the pancuronium overdose made a material contribution to the development of the condition, applying Bailey v Ministry of Defence [2009] 1 WLR 1052. The claimant had to prove causation on the balance of probabilities. Proof of the precise mechanism was unnecessary, but the evidence had to establish that the overdose probably contributed to the injury.
2. First episode. The court found that the significant fall in blood pressure from 28 to 22 occurred between midnight and 01.00, after the overdose might have been administered, but the timing did not establish causation. The claimant’s proposed physiological mechanism was undermined by the evidence that a therapeutic dose would ordinarily produce complete paralysis. Other explanations included severe respiratory distress syndrome, difficulty ventilating the claimant, prematurity and the contemporaneous administration of Curosurf. The product data and temporal association were insufficient to establish that the overdose caused or materially contributed to the hypotension.
3. Second episode. A further damaging event occurred around the transfer, as shown particularly by the step-change in metabolic acidosis. However, the hypotension had begun before the accidental extubation, dobutamine had already been commenced, and the extubation was rapidly and skilfully managed without a further fall in blood pressure. The evidence did not establish that this episode was caused or materially contributed to by the overdose.
4. Conclusion. The claimant’s neurological injury was more probably explained by prematurity, severe respiratory distress syndrome and the perinatal course. Causation was not established. The claim was dismissed.