The sitting position in anaesthesia

Abstract

Editor, The sitting position, first introduced into clinical practice in the early twentieth century, had operations on the posterior fossa/upper cervical spine as textbook indications. Although risks are related to the use of the sitting position, it has enabled surgeons to perform operations, which otherwise could not have been done. United Kingdom surveys conducted in 1981 and 1991 show a gradual decline in the use of the sitting position.1,2 Our telephonic survey of neurosurgical centres in the UK listed on the Society of British Neurosurgeons website enquired about the current use of this position. Table 1 compares the results with historical data.3–6Table 1: Neurosurgical centres that use the sitting positionOnly 27% of UK centres offer the sitting position now, contrasting with countries on the continent. Interestingly, in the UK, the surgeon usually decides about patient positioning, whereas in Japan, with the lowest percentage of hospitals using the sitting position, it was the anaesthetists objecting to the sitting position in 31% of hospitals.3 We telephoned a Consultant Neuroanaesthetist in each of the 11 UK Hospitals using the sitting position in Neurosurgery, to enquire about monitoring used (Table 2). Although a degree of variation exists within departments, the view given is the one deemed to be a fair representation.Table 2: Monitoring used routinely for the sitting position in neurosurgeryPreoperative patent foramen ovale screening was routine in six out of 11 UK centres (55%). In Germany, 45% of centres screened patients preoperatively in 1998, and the percentage is likely to be higher today in line with recommendations. Central venous pressure monitoring is routine for the sitting position in nine out of 11 UK centres, in one centre not always, in a further centre not at all. Two of these centres advance the central venous pressure lines into the right atrium; a further centre uses a long central line to have the option to advance the line if needed. Transthoracic Doppler is used in two centres; in a further centre, most of the anaesthetists make use of this device. Transoesophageal echocardiography for intraoperative monitoring would be available for use in two out of 11 centres (18%), but is not part of the routine monitoring for the sitting position in the UK. Ventilation with a small amount of positive end-expiratory pressure (PEEP) is used in six centres; however, some variation exists within departments with regard to the use of PEEP. An antigravity device (military anti shock trousers) is applied in one centre (9%). Overall, there is a trend towards less invasive monitoring in the UK, contrasting with a different approach on the continent. The least invasive approach is chosen by one UK paediatric centre with no screening for patent foramen ovale; however, selection criteria for suitability are applied. This centre applies invasive arterial blood pressure monitoring, but does not routinely use central lines or Doppler/transoesophageal echocardiography monitoring. Although the use of the sitting position in neurosurgery in the UK is declining, it is still enjoying popularity in other surgical specialties. Shoulder surgery in the beach-chair position shows similar haemodynamic effects in response to the position, with hypotension and neurapraxia observed in up to 30% of patients, but major complications including spinal cord ischaemia, cerebral ischaemia and death are rare.7 Although in the early eighties about half of the anaesthetics for dental chair procedures in the UK used the sitting position with no evidence of increased risk, only a few years later, an emotional faint under general anaesthesia in the sitting position has been discussed as a common cause for morbidity and mortality in the dental chair.8 Revival of the sitting position for lumbar microdiscectomies under regional anaesthesia has been reported. The advantages are described to be good recreation of load conditions, with no major com