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PAIN MANAGEMENT IN THE OBSTETRIC PATIENT 

EPIDURAL ANALGESIA

Continuous epidural infusion with LA has many advantages over intermittent bolus injection epidural, spinal anesthesia, anesthesia in labor. It maintains a stable level of analgesia and reduces the need for bolus injections. Hemodynamic disturbances are thus reduced, and fetal and neonatal outcome are improved. The risks of infection and intrathecal and intravascular migration of the epidural catheter are reduced, and safety is increased epidural, spinal anesthesia, anesthesia in labor. A combination of LA and epidural opioids produces good analgesia with rapid onset and longer duration of action and fewer side effects than LA alone. Parturients receiving epidural infusions of LA and opioids receive less bupivacaine, with reduced motor block at delivery. Continuous epidural infusion of bupivacaine is safe and does not cause hemodynamic changes or result in accumulation of LA in the mother or fetus.

The most commonly used LA is bupivacaine, at a standard concentration of 0.25% for bolus injections with an infusion of 0.125%, with fentanyl as the opioid at a rate of 8 to 12 mL/hr. Pain varies among parturients, so the bolus injections and rate of infusion must be varied greatly for adequate pain relief. Recent literature suggests an increased incidence of instrumental delivery rate related to epidural use in laboring women, but this conclusion is disputed. The result of this debate has been a surge of interest in the use of dilute concentrations of LA with opioids. Ultra-low concentrations of bupivacaine with opioids have been used with resulting good pain relief. These low concentrations produce minimal or no motor block and let the mother remain able to walk.

Carefully titrated continuous epidural analgesia to a T10 sensory level provides satisfactory analgesia for labor and delivery. Epidural analgesia with appropriate monitoring would be useful for labor analgesia in most critically ill parturients providing there are no contraindications to placement of an epidural catheter. Uterine displacement must be maintained at all times to avoid aortocaval compression. Decreases in blood pressure must be corrected.

INTRATHECAL OPIOIDS

When compared with LA, spinally administered opioids produce selective analgesia. Intrathecal opioids do not produce motor block, sympathectomy, hypotension, or adverse effects on uterine contractility. When given in small doses, they produce no adverse fetal or neonatal effects. Intrathecal morphine (0.5-2.0 mg) has been shown to provide good analgesia in the early first stage of labor, which lasts up to 11 hours. It takes 30 to 60 minutes for the parturient to experience significant pain relief with intrathecal morphine, and side effects can last.

Side Effects

Side effects of intrathecal fentanyl and intrathecal sufentanil appear to be mild and do not require treatment. Intrathecal sufentanil, being more potent and lipid soluble than intrathecal fentanyl, can cause respiratory depression and apnea, and the parturient should be monitored carefully for at least 1 hour after injection.

COMBINED SPINAL-EPIDURAL ANALGESIA

A combined spinal-epidural (CSE) anesthesia technique provides rapid onset of analgesia with drugs administered via a small-gauge pencil-point spinal needle into the intrathecal space. An epidural catheter placed simultaneously provides flexibility of epidural analgesia. Pain relief can be provided later with the epidural catheter.

CONTINUOUS SPINAL ANALGESIA

The development of small-bore catheters produced an interest in continuous spinal analgesia techniques for labor. The catheter overcomes some of the drawbacks of single opioid injections. Reports of cauda equina syndrome after widespread use of small-gauge spinal catheters led to withdrawal of the catheter from the market.

PATIENT-CONTROLLED EPIDURAL ANALGESIA

Pain varies greatly among parturients during labor and even within the same parturient during the course of labor. Some parturients like to participate more actively in all aspects of intrapartum care, including pain relief. The advantages of patient-controlled epidural analgesia (PCEA) are control of pain relief by the parturient.