A national survey into the peri‐operative anaesthetic management of patients presenting for surgical correction of a fractured neck of femur

We read with interest the survey by Dr Sandby-Thomas et al. [1] concluding that spinal anaesthesia was performed 75.8% of the time as the regional technique of choice for the correction of a fractured neck of femur. The discussion suggested that the spinal injectate solution should consist of local anaesthetic and morphine. We can sympathise that only 5.9% of respondents regularly add intrathecal morphine to their spinal solution as the risk of delayed respiratory depression is of concern in an elderly population returning to a general surgical ward. As a hydrophilic opioid, morphine is retained within the central nervous system after intrathecal injection [2] with a maximum concentrated in the medulla oblongata after 6 h [3]. Slow cephalad migration of morphine within the cerebrospinal fluid is thought to lead to late depression of the respiratory centres on the floor of the fourth ventricle [4], the true incidence of which, is unknown [5]. Abouliesh et al. published work of a prospective study of 856 obstetric patients undergoing caesarean section who were given 0.2 mg intrathecal morphine [6]. They found that only eight patients had respiratory depression which they defined as oxygen saturation less than or equal to 85% and/or respiratory rate ten breaths per minute or less. Murphy et al. [7] suggested that a dose of 100 μg of intrathecal morphine provided the best balance between analgesic efficacy and side effects in elderly patients undergoing hip arthroplasty. Other predisposing factors to respiratory depression are the concomitant administration of local anaesthetic [8], or central nervous system depressants [9] and reduced ventilatory capacity all of which can be present in this population. Clearly each hospital requires a comprehensive system in place for the postoperative monitoring of elderly patients if intrathecal opioids are to be used, to ensure potential respiratory depression is recognised and appropriately managed.