The ancient Greeks were the first to describe the use of narcotics. However, not until the turn of the 20th century did reports of the first epidural anesthetics appear. In the mid-1970s an understanding of the mode of action of narcotics was developed. When discovered, endorphins (endogenous opioid-like compounds) were thought to modulate the transmission of pain by acting on spinal cord opioid receptors. The substantia gelatinosa, an area of the spinal cord found to be rich in opioid receptors, was recognized as a key feature in pain transmission. Then, in the 1980s, intrathecal opioids were initially used in the treatment of intractable cancer pain, an event that led to the eventual widespread postoperative use of spinal opioids [2]. Today, epidural analgesia is an alternative to traditional pain management methods in a variety of clinical settings.

The arachnoid mater, the middle layer, is a thin and transparent covering. Located between the arachnoid and pia mater is the subarachnoid or intrathecal space. The subarachnoid space extends from the cranium to the sacrum and contains cerebrospinal fluid (CSF) and nerve roots. The dura mater is the outermost meningeal layer. Between the dura mater and the vertebrae is a ligament called the ligamentum flavum, which lines the vertebral canal. Between the dura mater and the ligamentum flavum is the epidural space. As a potential space, it also extends from the base of the skull to the coccyx. It contains fatty and connective tissue, lymph and blood vessels, and spinal nerve roots. The epidural space functions as a fatty pad that surrounds the spinal cord and is a potential depot for lipid-soluble narcotics [2,3].

In contrast, the intrathecal space is usually accessed for a one-time administration of a narcotic bolus. The intrathecal route is used most often in anesthesia practice and for patients who require pain relief for a short duration. The main advantages of this route are its speed and reliability; however, additional doses cannot be given. Because intrathecal narcotic doses are approximately one-tenth of those used with the epidural route, the catheter is removed after administration to prevent infection or accidental overdose. Therefore, a larger volume and higher dose of narcotic is needed when utilizing the epidural route for pain management [2,4].

Pain can be classified in various ways. For instance, there are somatic, visceral, and neuropathic types of pain, each of which is associated with different etiologies. Somatic pain results from activation of nociceptors by thermal, mechanical, or chemical stimuli in the superficial or deep tissues. As peripheral receptors are activated, the pain perception is transmitted to the spinal cord and higher cerebral cortex, where pain is perceived. Usually constant and well-localized, somatic pain is often described as sharp, aching, or throbbing. By contrast, visceral pain results from some type of organ damage or dysfunction. Depending upon the exact etiology, visceral pain may have many different descriptions, such as deep, dull, aching, boring, or pressure-like. Lastly, neuropathic pain, originating in the nervous system, is often described as a burning, tingling, or numbing sensation.

Epidural analgesia is indicated in the management of both acute and chronic pain. Acute postoperative populations that may benefit from epidural analgesia include [2,4,6,7,8,9]:

Thoracic procedures (e.g., thoracotomy, bilateral lung volume reduction, lung transplant)

Upper abdominal procedures (e.g., esophagogastrectomy, abdominal aortic aneurysm resections, liver resection)

Orthopedic procedures (e.g., laminectomy, hip replacement)

Peripheral vascular procedures

Gynecologic/urologic procedures (e.g., vaginal deliveries, cesarean section)

Just as there are several indications for epidural analgesia in the acute care setting, several contraindications also exist. The first absolute contraindications for epidural analgesia are patient refusal and a history of true allergic reaction to a narcotic class. In the case of allergy, which is very rare, another opioid class may be utilized in place of the original drug. Patients who have abnormal hemostasis (e.g., thrombocytopenia, abnormal prothrombin time/partial thromboplastin time values) or who are receiving anticoagulants such as heparin, warfarin, aspirin, or enoxaparin are also contraindicated due to the increased risk of developing an epidural hematoma at the catheter insertion site. Patients who have a systemic infection or a localized infection at the puncture site are contraindicated due to the increased risk of developing an epidural abscess or meningitis [7,23].

The last two contraindications for epidural analgesia are related to neurologic status. Patients who have undergone a recent laminectomy with opening of the dura are contraindicated due to the risk of catheter migration into the subarachnoid space and accidental overdose. Increased intracranial pressure also poses considerable risk. In the event that the dura is inadvertently nicked during catheter placement, the loss of CSF could cause cerebellar or tentorial herniation [7].

The actual site for catheter placement is determined by the dermatome innervating the area of pain. With thoracic procedures, the catheter is placed between T2–T8, depending upon whether the upper or lower lobes of the lung are affected. Mund et al. reported that the majority of epidural catheters in lung transplant patients were inserted at the level of T9 (with a range from T4–L4) [18]. Similarly, with upper abdominal, orthopedic and peripheral vascular procedures, catheters are placed between T4–L1, T10–L3, and L4–L5, respectively. In the case of trauma, the epidural catheter is placed directly at the site of injury [8]. Selecting the proper dermatome level is even more important when the patient will receive epidural local anesthetics (compared to opioids) as these agents block both afferent and efferent nerve fibers [5,24].

The rate of narcotic diffusion across the epidural space is affected by lipid solubility. In other words, the more lipid-soluble the drug, the more rapidly it diffuses across the epidural space to the opioid receptors in the spinal cord. With rapid diffusion, less drug is available to migrate to higher brain centers via the CSF or systemic circulation. Even though small amounts of epidural narcotics do reach the supraspinal levels, analgesia is provided with fewer side effects than seen with the systemic route [6,7].

Epidural analgesia is associated with several clinical benefits. These advantages include [2,4,7]:

Drug benefits: Longer duration and lower total doses

Response benefits: Improved analgesia, less sedation, earlier ambulation, and reduced morbidity from lessened complications, such as pulmonary problems or effects from the metabolic stress response

Outcome benefits: Improved pulmonary and gastrointestinal function and shortened length of hospital stay

In contrast, fentanyl is a synthetic narcotic that is 100 times more potent than morphine. As a highly lipid-soluble drug, it diffuses quickly to opioid receptors, with an onset of 10 to 15 minutes. Another main advantage of fentanyl's lipophilicity is that it leaves less drug available for rostral spread, which results in fewer narcotic-related side effects. Fentanyl has a relatively short duration (one hour or less) and is used when analgesia is needed for a short time. Respiratory depression occurs in more than 10% of patients but is more common in elderly patients [47]. Therefore, monitoring for respiratory depression periodically throughout the duration of the initial dose is necessary.

Continuous infusions deliver epidural drugs at a constant rate by means of an infusion pump, avoiding the peaks and valleys associated with the intermittent technique. This method of administration provides more consistent analgesia due to a constant blood level of the prescribed opioid and also allows a lower total volume of drug to be infused at one time. As a result, fewer side effects, such as respiratory depression, occur with continuous infusions. In addition, the rate of the infusion may be titrated to the patient's response, providing the optimal level of analgesia. The major disadvantage of this route is reliance on an infusion pump and the potential for equipment malfunction [7].

Implantable ports or infusion pumps are the last option for delivering epidural narcotics. Implantable devices are used for patients requiring long-term pain management, such as oncology populations. With implantable ports, the epidural catheter is surgically placed at the indicated interspace and then tunneled subcutaneously around the patient's trunk. The catheter exits on an accessible location of the abdomen so the injection port can be accessed for either intermittent or continuous infusions [6]. Nonprogrammable fixed-rate infusion pumps deliver a predetermined constant rate of infusion and allow for a change in the dose by changing the drug concentration in the reservoir. Programmable pumps (i.e., variable delivery rate pumps) allow for alterations to the dose, single doses, timed-specific doses, or changes in the continuous infusion rate [8].

Another intervention to improve safety with administration of epidural medications is the use of dual verification. Dual verification, the independent verification by a person competent to administer the medication, is necessary with medications like epidural narcotic infusions because of their high risk of adverse patient outcomes should an error occur. Consider dual verifications on all initial epidural pump set-ups and programming changes (i.e., dose or concentration changes). A well-conducted dual verification includes:

Order detail (drug, dose, concentration, and route)

Medication label

Protocol, if applicable

Programming and any calculations (weight, body surface area, age if applicable, and dilution and syringe volume)

Monitoring of vital signs is imperative in patients with epidural catheters. Heart rate, blood pressure, and respiratory rate should be monitored hourly for the duration of analgesia. Specifically, vital signs should be monitored for 8 hours in patients receiving fentanyl and for 24 hours in patients receiving morphine [47].

At least every four hours, the catheter site should be checked for intactness or the presence of wetness and for signs of infection. Mild erythema and tenderness at the catheter site are considered normal findings due to bruising and trauma during catheter insertion. However, the physician should be notified if drainage, increasing redness or warmth, or fever is present so that the catheter may be removed. In addition, assess for other neurologic signs that may indicate the development of meningitis, such as headache, persistently high fevers, and nuchal rigidity [5,23,28,29].

Pruritus is the most frequently reported narcotic-related side effect of epidural analgesia. The incidence ranges from 28% to 100%, occurring with both acute and chronic administration [2]. Pruritus tends to increase during pregnancy and with co-administration of steroids. The greater intensity of pruritus with epidural narcotics may occur from altered cutaneous sensation or from the effect of the narcotic on the central mechanism located in the medulla [46]. While pruritus is not dose-related, it may continue for the duration of the narcotics' effect. However, some reports identify that pruritus may abate in 48 to 72 hours in patients receiving continuous morphine administration [6,7].

Occlusion of the epidural catheter may be due to various causes. The most common causes include the development of a blood or fatty clot within the catheter, contact of the tip of the catheter against an epidural vein, or kinking of the catheter [7]. Some epidural catheters are virtually kink-resistant due to the coil housed within the lumen of the catheter. If the epidural catheter does become occluded, the patient will not receive analgesia and will complain of returning pain [7]. In this situation, reassessment of catheter patency and placement is warranted.

9. Knowledge deficit related to use of epidural analgesia as a method of pain control

Expected Outcome

Patient/family will understand purpose of epidural analgesia, including risks and benefits.

Nursing Interventions

Inform the patient/family about the procedure used to insert the epidural catheter.

Teach the patient how to use the pain rating scale and to inform the nurse of decreased levels of analgesia.

Explain the onset and duration of analgesia that may be expected.

Teach the patient/family that epidural analgesia will control pain and not totally eliminate pain (unless epidural anesthetics are used).

Inform the patient to tell the nurse if side effects are experienced at the onset (e.g., nausea/vomiting, pruritus, bladder distention).

If the epidural catheter is intended for long-term use, teach the patient/family about home care.