Epidural Anesthesia: Effects on Analgesia and other Clinical Outcomes

Overview: 

Effects on Nociception

Epidural anesthesia is a type of neuraxial anesthesia: Local anesthetic with or without opioids are injected into the epidural space with the goal of a complete or partial blockade of nociceptive input (pain signaling from injured tissue) at the spinal cord level. Blocked or reduced transmission of nociception then result in anesthesia or analgesia respectively. Epidural anesthesia is used as surgical anesthesia for abdominal, pelvic, and lower extremity procedures and, less commonly, thoracic procedures. Epidurals may supplement generalanesthesia for painful thoracic, abdominal, and pelvic procedures with the option to allow continuouspostoperative epidural analgesia following these procedures.

The placement of an epidural catheter into the epidural space allows the continuous infusion of local anesthetic, resulting in a long-lasting reduction of nociceptive input. The coverage follows a dermatomal distribution: a band of reduced sensation is produced. The more local anesthetic is injected, the more coverage can be achieved. The blockade of nociceptive input at the nerve root level results in very potent pain reduction.

Sympatholysis

TThe other important effect of epidural analgesia using local anesthetic is sympatholysis via blockade of the sympathetic chain, also in a dermatomal distribution. This mechanism is responsible for some of the benefits effects such as the reduction of the stress response associated with trauma and surgery as well as of the side effects such as hypotension due to vasodilation that are associated with epidural analgesia.

Analgesia

Epidural analgesia is the gold standard for painful thoracic, abdominal,  pelvic, and lower extremity  procedures. It can provide excellent pain control that can be difficult or impossible to achieve with other analgesic modalities.

Other Clinical Outcomes

In addition to superior pain control, epidural analgesia has also been associated with the following beneficial outcomes:

  • Decreased Mortality after Surgery

A systematic review investigating the effects of epidural analgesia on mortality and morbidity identified 10 trials (2201 patients; 87 deaths) that reported on mortality as a primary or secondary endpoint. The risk of death was decreased with epidural analgesia by about 40%: (3.1% vs 4.9%; odds ratio, 0.60; 95% confidence interval, 0.39-0.93). This striking effect that was also seen in earlier reviews and can be explained by the following effects on perioperative morbidity.

  • Attenuation of the stress response after surgery

The ‘stress response’ results from activation of neural, metabolic and endocrine pathways. Epidural analgesia has shown to decrease this response thus reducing the initiation of coagulation and inflammatory mechanisms.

  • Pulmonary Function

Epidural infusions have been shown to reduce the incidence of postoperative atelectasis and pulmonary infection and improve postoperative oxygenation. Improved pain control reduces splinting and patients breathe better. In addition, airway reflexes potentially resulting in bronchospasm are suppressed.

  • Cardiovascular Effects

Postoperative epidural analgesia reduces the incidence of postoperative myocardial infarction. Epidural analgesia also significantly decreased the risk of atrial fibrillation, supraventricular tachycardia, deep vein thrombosis and potentially subsequent pulmonary embolization. These effects are mostly attributable to a reduction of the sympathetic activity and a reduced thrombotic tendency.

  • Gastrointestinal Function

Pain, sympathetic activity and systemic opioids all contribute to the maintenance of postoperative ileus. Epidural analgesia, by limiting systemic opioid use and improving intestinal motility by blocking nociceptive and sympathetic reflexes, reduces the duration of postoperative ileus, improves recovery of bowel function and decreases postoperative nausea and vomiting.

  • Chronic Pain

The perioperative use of epidural anesthesia has been associated with a reduced incidence of persistent postsurgical pain (the development of chronic pain caused by the surgery).​

References: 

Popping DM, Elia N, Van Aken HK, Marret E, Schug SA, Kranke P, Wenk M, Tramer MR.  Impact of epidural analgesia on mortality and morbidity after surgery: systematic review and meta-analysis of randomized controlled trials. Annals of Surgery 2014; 259(6): 1056-1067.

Susan M Nimmo. Benefit and outcome after epidural analgesia, Continuing Education in Anaesthesia Critical Care & Pain, Volume 4, Issue 2, April 2004, Pages 44–47

Author: 
Matthias Behrends