by Karen M. Wildman, Virginia K. Mohl, Jane H. Cassel, Robert E. Houston, David A. Allerheiligen
Intrathecal analgesia is a highly effective technique for pain relief in the first stage of labor. It is a technically simple procedure that can be easily learned by family physicians currently performing diagnostic lumbar puncture. Its effectiveness, simplicity, and low incidence of serious complications make it especially applicable to the practices of physicians delivering babies in areas where continuous epidural anesthesia is not available.
The goals of obstetrical management are twofold: to ensure the best possible medical outcomes for mother and infant, and to optimize the birth experience for the mother and family. Pain management is often a critical component in meeting these goals. Providing adequate pain relief can be problematic, especially in areas where choices are dictated by personnel or facility limitations. Injection of small doses of opiates into the dural space (intrathecal analgesia) can provide effective pain relief for first stage labor. Because this procedure has a low incidence of serious side effects and is an easy technique to learn, it is being used by physicians in a wide variety of practice situations, particularly in areas where limited nursing or physician services make continuous epidural anesthesia impractical.
The low dose of narcotics used with intrathecal injection avoids some side effects seen with larger doses of intravenous narcotics. Infants experience no depression of respiratory effort or neurobehavior, and there is no loss of variability on fetal monitoring strips due to intrathecal narcotics.
Intrathecal analgesia may be an ideal pain management option in situations where epidural anesthesia is not available. In many rural and community hospitals, the only choices for pain relief in labor are relaxation techniques and intravenous narcotics. Often this is because of limited nursing or physician resources. Intrathecal injection is a simple technique that can be learned by most physicians. Continuous physician presence is not required after the injection because of the low incidence of serious side effects. The nursing care and patient monitoring needed after intrathecal injection is within the scope of most hospitals providing obstetrical care.
DISADVANTAGES
Complications
Major complications are rare with intrathecal analgesia. Spinal headache occurs in 1% to 5% of patients, varying with operator technique and equipment used.[4,6,8] treatment options include a blood patch, or conservative management with bed rest, fluids, analgesics, and caffeine. Other rare complications directly related to the dural puncture include meningitis and spinal nerve injury. The risk of these is approximately the same as with diagnostic lumbar puncture.
Maternal respiratory depression, allergic reaction, hypotension, and transient fetal bradycardia are other potentially serious complications. Although these are rare, they are unpredictable, and protocols must be in place to treat them if they should arise. Fetal bradycardia is usually of a moderate degree (fetal heart rate 80 to 100 beats per minute) and transient,[6,9] and responds well to fluids, repositioning the mother, and other first-line actions. Maternal hypotension and allergic reaction are rare and are seen in the first few minutes after the injection.[10] Intravenous fluids given before the injection may help decrease the frequency and severity of hypotension.[2,9] Ephedrine should be immediately available to treat severe hypotension, and epinephrine and antihistamines to treat allergic reaction.
Maternal respiratory depression is another rare but particularly worrisome complication. Respiratory depression is caused by the central effect of narcotics on the respiratory center, and remains a risk for as long as the narcotics are exerting an effect (up to 24 hours for morphine).[5,11] Although respiratory depression has been seen less than 1 hour after injection, it is less likely to be a problem during active labor, when the patient is closely monitored and respiratory drive is normally increased. The danger arises after delivery, when the patient is resting and less closely watched. Close patient monitoring must continue until the effects of the narcotic are gone, and additional intravenous narcotics should be avoided during this time to avoid increasing the risk of respiratory depression. Some protocols call for continuous pulse oximetry during this time, others for hourly or more frequent measurement of mental status and vital signs. Treatment for respiratory depression consists of intravenous naloxone, oxygen, and respiratory support. Naloxone may need to be repeated frequently, as it is relatively short acting. Oral naltrexone (25 to 50 mg) given prophylactically after delivery may decrease the risk of respiratory depression.
Contraindications
In certain circumstances, intrathecal injection may be contraindicated. It should not be used if there is a skin infection overlying the area of injection, in patients with increased intracranial pressure, if there is an allergy to the narcotic being injected, or in the presence of fetal distress. It should be used with great caution, if at all, in the presence of a known coagulation defect. The use of intrathecal narcotics in chronic narcotic users is problematic. The medications may be less effective because of patient tolerance, and treatment for side effects with narcotic antagonists may precipitate narcotic withdrawal. Other options for pain relief should be considered in this patient population.
A maternal history of herpes labialis should be considered a relative contraindication to the procedure. Several reports have linked recurrences of herpes labialis to intrathecal and epidural narcotics. It is unclear whether a recurrence is due to the narcotics or to the side effect of the pruritus associated with the narcotics. Because a mother with a recurrence of oral herpes may pass that infection to her newborn, the physician should inquire about a history of recurrent herpes labialis before proceeding with an intrathecal inflection.
Side Effects
Although the incidence of serious complications with intrathecal narcotics is low, the incidence of side effects is high. They are caused by the effects of the narcotics on the central nervous system. They can be bothersome, but not usually medically serious. Pruritus is quite common, happening in 50% or more of patients. This can be severe, but usually responds well to treatment of intravenous naloxone, given in small boluses (0.1 mg, may be repeated at frequent intervals up to five times) or in a continuous infusion (0.2 mg per hour).12 The analgesic effect is not affected by this treatment. Because the itching is not related to histamine release, antihistamines usually do not help with this side effect.
Nausea and vomiting occur in 30% to 50% of patients which can be treated with antiemetics or metoclopramide. Urinary retention can also occur after intrathecal analgesia, and should be treated with intermittent catheterization as needed. It is seen in approximately 30% of patients. Maternal somnolence is seen in 40% to 60% of patients, but is generally mild and does not require treatment. If treatment becomes necessary, naloxone may be given in the dosages described above. After delivery, narcotic antagonists (naloxone or oral naltrexone) remain effective for treatment for side effects. The side effects usually do not last longer than the period of analgesic effectiveness.
In our experience, these side effects are generally acceptable to patients because treatment for side effects is so effective, and because of the benefit the patient receives from the pain relief. For maximal patient satisfaction, treatment for itching and nausea should be given early and aggressively, sometimes even when the patient perceives them as an annoyance rather than a complaint. These side effects tend to progress in severity, and do not respond as wen to treatment when they are severe.
OTHER CONSIDERATIONS
Pain in the first stage of labor originates from the force of uterine contractions, ligamentous stretching, and cervical dilation and effacement. Intrathecal analgesia is very effective for this type of pain. Pain in the second stage of labor originates from the descent and passage of the infant through the birth canal and introitus. Intrathecal analgesia does not alter sensation in the vagina and perineum, and is not as useful for pain relief in this stage.[7] In clinical experience, however, women who have received intrathecal injections in the first stage seem to have an easier second stage.[2,3] This may be because they are still getting relief from uterine pain, or perhaps because they are less fatigued from the first stage of labor. For additional pain relief in the lower genital tract, a pudendal block or local anesthetic on the perineum may be used.
One of the physician's goals should be to time the injection so that the patient has adequate pain relief through to delivery. Familiarity with the various medications and their durations of action help with this decision. If the analgesic effect has diminished before delivery, however, additional pain relief can be problematic. Additional intravenous narcotics should be avoided because the risk of postpartum respiratory depression can be increased. In clinical practice, some physicians report good results with a second intrathecal injection of a short-acting narcotic, or with intravenous administration of a mixed narcotic agonist-antagonist, eg, butorphanol, nalbuphine, or buprenorphine. These practices, however, have not been well studied as to effectiveness or safety. As an alternative, some anesthesiologists perform a combination intrathecal-epidural, in which an epidural catheter is placed at the time of intrathecal injection. This catheter may be used later if additional pain relief or an operative delivery becomes necessary." This option allows the intrathecal narcotic to be used for pain relief earlier in labor, but is feasible only in facilities where epidural anesthesia is used.
COPYRIGHT 1997 Dowden Health Media, Inc.
COPYRIGHT 2004 Gale Group
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