Explain the historical context of spinal anaesthesia in the ambulatory setting. Describe the ideal characteristics of an ambulatory spinal anaesthetic. Recognise the central role of prilocaine and 2chloroprocaine in the ambulatory setting. Select the right drug for the right patient and the right procedure. Ambulatory surgery places high demands on anaesthetic technique. In this setting, rapid onset and offset of anaesthesia, rapid recovery of protective reflexes, mobility and micturition, and good control of postoperative pain and nausea are required. Since the inception of ambulatory surgery, the favoured anaesthetic technique has been general anaesthesia with short-acting drugs. Concerns about the time to perform spinal anaesthesia and the risks of prolonged motor block and urinary retention have limited its use. Whilst in the UK, 'ambulatory surgery' refers solely to patients being discharged from the hospital shortly after surgery, in the USA this term may also apply to admissions for up to 23 h. In this article, we will consider ambulatory surgery to mean that the patient is discharged home before midnight on the day of surgery. Spinal anaesthesia has become increasingly popular for inpatient surgery, but, until recently, its use has been limited in ambulatory surgery by the lack of a safe, licensed short-acting local anaesthetic agent. An ideal intrathecal agent for ambulatory surgery should have a rapid onset of motor and sensory blockade, predictable regression within an acceptable time frame, and a low incidence of adverse effects. Historically, lidocaine was the preferred agent in this setting, providing a dense block with rapid recovery, but the identification of a high incidence of transient neurologic symptoms (TNS) has effectively excluded it from use. 1,2 Until recently, the only local anaesthetic preparations licensed for intrathecal use have been hyperbaric William Rattenberry FRCA is a specialty trainee in anaesthesia whose interests include quality improvement and regional anaesthesia.

We have recorded the threshold concentration of inhaled ammonia vapour required to elicit reflex glottic closure (NH3TR) in 102 healthy, nonsmoking volunteers (39 female) aged 17-96 yr in order to assess the effect of age upon upper airway reflex sensitivity. A single measurement of sensitivity was made in each subject using a system delivering small concentrations of ammonia vapour for single intermittent breaths to the upper airway and recording glottic closure using an inspiratory pneumotachograph. We found a strong positive correlation between age and NH3TR, indicating a decrease in upper airway reflex sensitivity with increasing age.

In two studies we have compared the upper airway reflex sensitivity (UARS) of chronic cigarette smokers with that of non-smokers and also the effect of different periods of abstinence on UARS in the smoking groups. UARS was measured by recording the threshold concentration of dilute ammonia vapour required to stimulate reflex glottic closure. The first study compared UARS in 20 non-smokers with 20 smokers, followed by another measurement in the smoking group after 24 h of abstinence. In study two, we measured UARS repeatedly over a period of 3-4 weeks in 16 smokers, half of whom had stopped smoking on day 0. Chronic cigarette smokers were found to have significantly greater UARS compared with non-smokers; the sensitivity was unaltered after 24 h of abstinence but was found to reduce over several days, the change commencing between 24 and 48 h, with most achieving a consistent change within 10 days.

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