Epidural local anesthetic: GI effect
Anatomy, Basic, Clinical Sciences: Anesthesia Procedures, Methods, and Techniques
Postoperative ileus is almost universal following major abdominal surgery. Nearly 100 years ago, Cannon and Murphy demonstrated that opening the peritoneal cavity and manipulating the intestines resulted in significant inhibition of GI tract contractile function in dogs. It has been suggested that epidural analgesia can shorten the duration of postoperative ileus and thereby decrease morbidity, length of hospital stay, and annual expense on ileus (approximately $750 million per year).
The autonomic nervous system certainly plays a large role in regulating GI motility. Tonic inhibitory sympathetic control (T6-L2 ) predominates, but parasympathetic activation increases contractile activity. Therefore, sympathectomy induced by epidural or spinal analgesia results in increased gut motility or inhibition of ileus development. This has been borne out by multiple studies, especially those involving epidural catheter placement at T12 or higher.
Additionally, the use of epidural analgesia with local anesthetic and/or opioid decreases or eliminates need for systemic opioids by minimizing postoperative pain. It is well known that the use of systemic narcotics prolongs the duration of an ileus. Less pain also translates into reduced release of catecholamines which promotes better gut contraction. Local anesthetics, either neuraxial or systemically given, have also been shown to improve intestinal perfusion as well as reduce GI tract irritation through their anti-inflammatory properties. These are additional mechanisms by which epidural analgesia reduces the duration of postoperative ileus.
Several studies have been performed comparing the GI effects of epidural local anesthetics to epidural opioids. In all studies with an epidural catheter above T12, GI motility was greater with the use of epidural local anesthetics alone compared with epidural opioids alone . Studies with lumbar epidural catheters did not demonstrate this consistently. Nevertheless, it appears that local anesthetics and local anesthetic-opioid mixtures are more effective and have better side-effect profiles than epidural narcotics alone.
Note that nausea is a common complication of neuraxial anesthesia , although the etiology is unknown
Local Epidural and GI Effect
- Sympathectomy (T6-L2): results in relative increase in parasympathetic tone
- Decreased Release of Catecholamines
- Nausea: etiology unknown