Why bother with pre-assessment? Let’s CRAC-ON

“I take a simple view of life: Keep your eyes open and get on with it.” – Laurence Olivier

Complete relinquishing of anaesthetic conscientiousness, optimisation & nuance (CRAC-ON) trial. N Chrimes. Anaesthesia DOI: 10.1111/anae.13715

This paper was the inaugural Christmas special study published by the journal Anaesthesia and was presented at our Journal Club Christmas edition.

The study is a single centre, quadruple-blinded, randomised control trial assessing the need for a pre-operative assessment in patients presenting for elective surgery at a tertiary Australian hospital. The basis for the study was that with the safety of modern anaesthesia, the rarity of ‘can’t intubate, can’t ventilate’ scenarios coupled with productivity concerns: is pre-assessment really needed?

Over a 3 week period patients were randomly allocated to one of 2 groups:

  • Pre-assessed: These were pre-assessed by the most fastidious anaesthetist, undergoing all investigations and interventions felt necessary prior to presenting for surgery.
  • Non-assessment: These patients presented on the day of surgery and underwent a standard anaesthetic (100mcg fentanyl, 200mg propofol 40mg atracurium and 10mg morphine) and were ventilated with an O2/air and sevoflurane mix via a size 8 ETT using volume control ventilation (700ml/breath at 10breaths/minute)

The paper was the first to utilise a novel quadruple blinding approach, blinding investigators to group allocations, the patients to whether they had attended a real pre-assessment with the use of a sham appointment conducted by an actress, the anaesthetists performing anaesthesia by literally blindfolding them and also the ethics committee to the study actually occurring. Children were excluded to minimise the risk of massive overdose in the non-assessed group although the author expressed his concerns that this “sissy approach” itself was potentially causing bias by perpetuating the need for the pre-assessment ritual.

There was a large difference in the number of patients anaesthetised between the groups; 0 from the fastidious group but 472 anaesthetics in the non-assessment group. It was noted that this was greater than the number of patients as presumably due to blindfolding it included several patient relatives and a theatre technician in the wrong place at the wrong time. The study sadly reported an unreported number of deaths in this arm, however this was not statistically significant as no statistical testing was performed.

The authors conclusion was both sage and apt; ‘there is probably a happy medium between the two approaches.’

There were a number of limitations in the design of study, including definitions of fastidious and children, with the risk of bias at several levels, however the authors attempted to minimise these by combining both quadruple blinding with a lack of statistical analysis in order to reach their conclusion.

Summary by Dr Timothy Snow.

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