Falling after epidural analgesia: lessons from obstetric anesthesia

Abstract

Most upper abdominal and thoracic surgeries produce significant postoperative pain, and patients expect anesthesiologists to provide efficacious postoperative pain relief. Modern epidural analgesia provides significant advantages over opioid-based analgesia, including better pain control at rest as well as during mobilization and coughing; improved cardiovascular, respiratory, and gastrointestinal morbidity endpoints; reduced postoperative mortality; less sedation; and less nausea and vomiting. 1,2 Concerns remain, however, that epidurals may cause lower limb motor weakness and affect proprioception of the legs, which, together with sympathetic blockade-induced postural hypotension, may increase the risk of inpatient postoperative falls. In this month's issue of the Journal, Elsharydah et al. 3 use the Nationwide Inpatient Sample (NIS) datasets to explore the relationship between epidural analgesia in patients undergoing various thoracic or upper abdominal surgeries and the rate of inpatient accidents and falls (IAF). The authors found that, although the rate of inpatient falls increased over a five-year period, postoperative epidural analgesia (thoracic or lumbar) was not associated with the incidence of IAFs. These results are pertinent because they can provide clinicians with further reassurance about the safety of postoperative epidural analgesia in this setting. Nevertheless, the NIS datasets reviewed by the investigators did not provide details about the type, loading dose, and rate of administration of the local anesthetics and opioids used. Furthermore, they did not provide information about the duration of postoperative epidural drug administration and especially any temporal relationship between cessation of the epidural analgesic regimen and the documented fall. The question then arises regarding which epidural regimen can provide pain-free postoperative analgesia for patients while allowing them to walk safely without any increased risk of falling. The greatest insights into providing ambulatory epidural analgesia arose in the early 1990s from the frequent requests by pregnant women wanting to walk during labour. Low-dose epidural mixtures of local anesthetics with opioids were originally developed to reduce the incidence of epidural-related side effects, such as lower limb motor block, and to improve the safety profile of the epidural in case of accidental intravenous or spinal injection. Nevertheless, obstetric anesthesiologists quickly realized that patients could also walk with such epidurals. Over several decades, strategies have been developed to help evolve lumbar epidural analgesia into what is now well known as the ''mobile'' or ''walking epidural''. The success of the low-dose / mobile epidural focuses on one basic principle, i.e., reducing the total dose of local anesthetic infused into the epidural space in order to target only the small myelinated A-delta fibres and unmyelinated C fibres while sparing the larger and myelinated A-alpha motor fibres. It is quite clear from reviews on modern neuraxial labour analgesia that such advances were made possible using the following four strategies: 4,5