Analgesics epidural

Grass, J.A. Sufentanil clinical use as postoperative analgesic - epidural/intrathecal route, J. Pain Symptom. Manage. 1992, 7, 271-286. 

Grass JA. Fentanyl clinical use as postoperative analgesic-epidural/intrathecal route. / Pain Symptom Manage 1992 7 419-430. 

Epidural analgesia is frequently used for lower extremity procedures and pain (e.g., knee surgery, labor pain, and some abdominal procedures). Intermittent bolus or continuous infusion of preservative-free opioids (morphine, hydromorphone, or fentanyl) and local anesthetics (bupivacaine) may be used for epidural analgesia. Opiates given by this route may cause pruritus that is relieved by naloxone. Adverse effects including respiratory depression, hypotension, and urinary retention may occur. When epidural routes are used in narcotic-dependent patients, systemic analgesics must also be used to prevent withdrawal since the opioid is not absorbed and remains in the epidural space. Doses of opioids used in epidural analgesia are 10 times less than intravenous doses, and intrathecal doses are 10 times less than epidural doses (i.e., 10 mg of IV morphine is equivalent to 1 mg epidural morphine and 0.1 mg of intrathecally administered morphine).45... 

Epidural/Intrathecal Management of pain not responsive to nonnarcotic analgesics. For treatment of intractable chronic pain Infumorph only). 

Epidural analgesic - For epidural administration as an analgesic combined with low-dose bupivacaine, usually 12.5 mg per administration, during labor and vaginal delivery. 

Epidural/Intrathecal administration Limit epidural or intrathecal administration of preservative-free morphine and sufentanil to the lumbar area. Intrathecal use has been associated with a higher incidence of respiratory depression than epidural use. Asthma and other respiratory conditions The use of bisulfites is contraindicated in asthmatic patients. Bisulfites and morphine may potentiate each other, preventing use by causing severe adverse reactions. Use with extreme caution in patients having an acute asthmatic attack, bronchial asthma, chronic obstructive pulmonary disease or cor pulmonale, a substantially decreased respiratory reserve, and preexisting respiratory depression, hypoxia, or hypercapnia. Even usual therapeutic doses of narcotics may decrease respiratory drive while simultaneously increasing airway resistance to the point of apnea. Reserve use for those whose conditions require endotracheal intubation and respiratory support or control of ventilation. In these patients, consider alternative nonopioid analgesics, and employ only under careful medical supervision at the lowest effective dose. 

After epidural injection, an opioid may transfer into the cerebrospinal fluid (CSF), into the blood or bind to epidural fat, the extent depending on their lipophilicity. After epidural administration, morphine passes slowly into the CSF. Sufentanil, which is highly lipid soluble, can be detected in the plasma within 2-5 minutes after epidural injection and part of the analgesic effect of the more lipid soluble opioids may be due to a supraspinal action amplifying the direct spinal action. Epidural fentanyl and sufentanil produce a more consistent and intense analgesia than morphine, with a faster onset. Flowever, the duration is short but this can be overcome by giving them by continuous epidural infusions. 

Therapeutic doses of the opioid analgesics produce flushing and warming of the skin accompanied sometimes by sweating and itching CNS effects and peripheral histamine release may be responsible for these reactions. Opioid-induced pruritus and occasionally urticaria appear more frequently when opioid analgesics are administered parenterally. In addition, when opioids such as morphine are administered to the neuraxis by the spinal or epidural route, their usefulness may be limited by intense pruritus over the lips and torso. 

Because of their direct action on the superficial neurons of the spinal cord dorsal horn, opioids can also be used as regional analgesics by administration into the epidural or subarachnoid spaces of the spinal column. A number of studies have demonstrated that long-lasting analgesia with minimal adverse effects can be achieved by epidural administration of... 

Medico-technical instruments such as infusion pumps can be used in PCA (patient-controlled analgesia, Fig. 1) to provide patient-orientated and therapy as required, e.g. with morphine injection solutions. Depending on the patients perception of pain, they may add small doses of analgesics to the basic infusion by means of an electrically controlled infusion pump. The physician specifies the basic dose, which is infused independent of patient demands, the boluses that can be demanded, an hourly maximum dose and a refractory time that cannot be reduced between two doses. The infusion may be given intravenously, subcutaneously, epidurally or intraspinally. 

FIGURE 17-3 T Schematic illustration of PCA spinal delivery. The catheter delivers the analgesic into either the epidural or intrathecal [subarachnoid] space. Catheters for long-term use are tunneled under the skin (dashed line) and can either be connected directly to an implanted PCA pump, or exit the anterior-lateral flank for connection to an external pump. 

Opioid analgesics can also be used at low doses by the epidural and spinal routes of administration to produce excellent postoperative analgesia. 

The analgesic efficacy of the addition of clonidine to an epidural solution of bupivacaine plus fentanyl has been subjected to a randomized, double-blind study in 61 parturients who received bupivacaine plus fentanyl with or without clonidine (median dose 28micrograms/hour). There was no difference between the groups in pruritus or nausea score, but those given clonidine had less shivering and better analgesia (25). 

In another randomized, double-blind study, 84 parturients requesting epidural analgesia were given either bupivacaine 20 ml only, followed by intravenous fentanyl 60 pg or bupivacaine 20 ml with fentanyl 60 pg followed by intravenous saline (27). The minimum local analgesia concentration (MLAC) of bupivacaine + intravenous fentanyl was 0.064% w/v and the MLAC of bupivacaine + epidural fentanyl was 0.034% w/v. The epidural fentanyl solution significantly increased the analgesic potency of bupivacaine by a factor of 1.88 compared with intravenous fentanyl. This was associated with increased pruritus with epidural fentanyl. 

There was no difference in analgesic efficacy or the incidence of adverse effects when fentanyl 100 pg was compared with sufentanil 20 pg in women in labor who requested epidural analgesia (36). 

In view of the popularity of fentanyl as an epidural analgesic in labor, its site of action is of some... 

PoUey LS, Columb MO, Naughton NN, Wagner DS, Dorantes DM, van de Ven CJ. Effect of intravenous versus epidural fentanyl on the minimum local analgesic concentration of epidural bupivacaine in labor. Anesthesiology 2000 93(l) 122-8. 

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