When Should a Combined Spinal–Epidural Be Used?




Introduction


The combined spinal–epidural (CSE) technique produces reliable and rapid onset of spinal anesthesia combined with the flexibility to extend the height and duration of a block provided by continuous epidural anesthesia. CSE has become a popular technique in both obstetrics and orthopedic surgery. CSE was originally described in 1979 as a double-segment technique with the epidural and spinal procedures performed at different interspaces of the lumbar spine. Advances in needle design led to the more popular and practical single-segment technique (SST) in use today. In 1981 clinicians described the use of the SST for lower limb surgery and in 1982 for cesarean section.


The SST involves locating the epidural space with either a standard or a specialized epidural needle using the loss of resistance technique. Once the epidural space has been identified, a small-gauge spinal needle is introduced via the epidural needle into the cerebrospinal fluid. A spinal dose of opioid or local anesthetic (or both) is given through the spinal needle, and then the spinal needle is removed. An epidural catheter is then inserted through the epidural needle to the appropriate depth. The technique can be performed in the sitting or lateral position.




Options/Therapies


The CSE technique is widely used for labor analgesia, anesthesia for cesarean section, lower-extremity orthopedic surgery, and urologic procedures. Once popular, the role of CSE in lower-extremity vascular procedures has declined secondary to the use of antithrombotic and antiplatelet therapies for the treatment of vascular disease.


CSE produces a rapid onset of analgesia for the woman in advanced labor while simultaneously maintaining the maternal ability to push during the second stage. In early labor, an initial dose of intrathecal opioid alone maintains maternal mobility and may increase the speed of cervical dilation. Concurrent placement of the epidural catheter enables additional doses of local anesthetic with or without opioid to produce prolonged labor analgesia or cesarean section anesthesia.


CSE for cesarean section provides the benefit of a quick onset of neuraxial blockade with the ability to use the epidural if the spinal block recedes or the surgery is unexpectedly prolonged. Secondarily, the epidural can be used to provide postoperative analgesia with both low-dose local anesthetics and epidural opioids.


In orthopedic procedures, the CSE technique is used in lower-extremity surgeries, such as total hip and total knee arthroplasties. The technique can be as efficient as a general anesthetic, may reduce the incidence of postoperative deep vein thrombosis, and can be used for postoperative analgesia in the absence of antithrombotic therapy.


The low-dose sequential CSE technique is a modification of the original technique that uses a deliberately subanesthetic intrathecal dose with the expectation of extending the block height by the subsequent epidural injection of either local anesthetic or saline. This technique has been shown to enhance cardiovascular stability in high-risk cases, including pregnant women with severe pre-eclampsia.




Contraindications


Patients receiving a CSE must be appropriate candidates for a neuraxial technique. Contraindications include patient refusal, coagulopathy, and some infections. American Society of Regional Anesthesia and Pain Medicine (ASRA) guidelines recommend that a patient have normal coagulation status before undergoing instrumentation of the neuraxis. Aspirin or nonsteroidal antiinflammatory agent therapy is not a contraindication; however, other antiplatelet therapies such as clopidogrel require cessation 7 days before undergoing the procedure. Patients taking warfarin should go 5 days without therapy or have a current normal prothrombin time (PT) and international normalized ratio (INR). Patients receiving prophylactic doses of low-molecular-weight heparin (LMWH), such as 30 to 40 IU enoxaparin or 5000 IU dalteparin every 24 hours, must wait 12 hours after the last dose before undergoing neuraxial blockade. Patients receiving therapeutic doses of LMWH, such as 1 mg/kg enoxaparin every 12 hours, 1.5 mg/kg enoxaparin daily, 120 U/kg dalteparin every 12 hours, 200 U/kg dalteparin daily, or 175 U/kg tinzaparin daily, must wait 24 hours from the last dose before receiving a neuraxial block. Direct thrombin inhibitors such as argatroban are contraindicated until more data are available. Subcutaneous heparin is not a contraindication to regional anesthesia.


Evaluating the coagulation status of the obstetric patient can present a special challenge. Pregnancy may be complicated by conditions that lower the platelet count or inhibit platelet function such as pre-eclampsia, eclampsia, or the syndrome of hemolysis, elevated liver enzymes, and low platelets (HELLP syndrome). Given the hypercoaguable condition of pregnancy, the absolute platelet count is less concerning than the trend in platelet numbers. There is no evidence for a specific platelet count below which neuraxial techniques are contraindicated in the obstetric patient. Thus it would seem, as a practical matter, that a risk–benefit assessment should be undertaken for any pregnant woman with a platelet count of less than 75,000/mm 3 or with a sudden, substantial drop from her baseline, and an individualized decision should be reached regarding the safety of a neuraxial technique. Patients with a platelet count less than 75,000/mm 3 should be examined for stigmata of coagulopathy (easy bruising, petechiae, bleeding from the intravenous site or Foley catheter) before instrumentation. A PT, a partial thrombin time, and a platelet count should be reviewed before proceeding. If any of the aforementioned test results are abnormal, a fibrinogen level and a d-dimer level are useful in assessing the patient for the presence of disseminated intravascular coagulation.


Obstetric patients may be receiving anticoagulation therapy for a variety of obstetric or nonobstetric indications. Ideally, women taking long-acting anticoagulants (e.g., for deep vein thrombosis prophylaxis or prosthetic heart valves) should be converted from their long-acting therapies (e.g., LMWH) to subcutaneous heparin at 36 weeks of gestational age. A patient taking therapeutic LMWH who is in labor must wait a minimum of 24 hours from the last dose before undergoing CSE analgesia or anesthesia.


Patients with infection at the needle insertion site, suspected meningitis (bacterial or viral), or sepsis should not undergo neuraxial blockade. Patients with suspected chorioamnionitis can receive regional anesthesia after the administration of appropriate intravenous antibiotics. Parturients with a primary herpes simplex outbreak are at increased risk of herpetic meningitis with neuraxial techniques. Human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) is not a contraindication to CSE.




Evidence Favoring the Use of Combined Spinal–Epidural Technique


Combined Spinal–Epidural Technique for Labor Analgesia


The benefits of CSE for labor analgesia have been described in comparison with either traditional epidural or modern low-dose epidural analgesia. These benefits include faster onset of analgesia, better pain relief in advanced labor, improved maternal mobility, and less chance of an instrumented vaginal delivery. Because no standard drug regimen exists for CSE, traditional, or low-dose epidural analgesia, it is difficult to compare and contrast studies. Nonetheless, a Cochrane Systematic Review, which included data from 19 randomized trials (2658 laboring women), has attempted to assess the evidence behind some of the stated benefits of CSE. This analysis found that analgesic onset is faster with CSE compared with low-dose epidural analgesia, and the likelihood of patient comfort at 10 minutes was nearly twice as high in patients receiving CSE. This finding is important to the laboring woman rapidly approaching the second stage of labor, for whom both comfort and maintenance of adequate motor strength to push are important therapeutic goals.


Two studies have suggested that the CSE technique has no negative influence on obstetric outcome when administered in very early labor. The first, a randomized study of the combination of intrathecal sufentanil and bupivacaine compared with epidural bupivacaine for early (cervical dilation less than 5 cm) analgesia, demonstrated a faster rate of cervical dilation in parturients receiving CSE analgesia (2.1 cm/hr versus 1 cm/hr; p = 0.0008). The parturients receiving CSE analgesia also had a quicker analgesic onset and superior pain scores for 110 minutes compared with the women with epidural analgesia. There was no difference in the rate of cesarean section or instrumental delivery between the two groups. A randomized trial of intrathecal fentanyl (25 mcg) compared with systemic hydromorphone (1 mg intravenously and 1 mg intramuscularly) for early (median cervical dilation, 2 cm) labor analgesia followed by epidural analgesia in both groups demonstrated that the CSE group experienced superior analgesia, shorter analgesic onset, and a shorter interval to complete cervical dilation (295 versus 385 minutes; p = 0.001) and gave birth to infants with higher Apgar scores ( p < 0.01). There was no difference in the rate of cesarean section or instrumental delivery between the two groups. The Cochrane analysis compared the likelihood of an instrumental vaginal delivery in patients receiving CSE, traditional epidural analgesia, and low-dose epidural analgesia. There was no difference between CSE and low-dose epidurals, but the relative risk of 0.82 (95% confidence interval, 0.67 to 1.00) was at the border of favoring CSE over traditional epidurals.


Combined Spinal–Epidural Technique for Cesarean Section


The CSE technique has been associated with positive outcomes and low failure rates when used as the anesthetic technique for cesarean delivery. A controlled study of intrathecal bupivacaine compared with epidural bupivacaine demonstrated that 100% of the women receiving a CSE anesthetic had adequate anesthesia compared with 74% of women receiving epidural anesthesia. The total dose of bupivacaine used was three times higher in women with epidural anesthesia (125 mg) compared with those using the CSE technique (40 mg). Maternal and fetal blood concentrations of bupivacaine were higher in the women with epidural anesthesia (604 mg and 186 mg, respectively) compared with the women with intrathecal anesthesia (205 mg and 45 mg, respectively). There was no difference in Apgar scores, umbilical cord blood gases, or the neonatal neurobehavioral examination between the two groups.


A randomized, prospective study of 120 women comparing CSE with epidural anesthesia assessed both objective outcomes and subjective maternal experience. The women receiving intrathecal bupivacaine and fentanyl had quicker onset of a T4 level of anesthesia (10 versus 16 minutes), a shorter time to surgical incision (29 versus 36 minutes), and more reliable motor blockade (54% versus 11%) than the women receiving epidural lidocaine with epinephrine and fentanyl. Significantly more women in the CSE group reported no pain, lower anxiety, and greater satisfaction than in the epidural group. There were no significant differences in incidence of hypotension, nausea, pruritus, postdural puncture headache (PDPH), or neonatal outcomes between the two groups.


Hypotension can be an important side effect of spinal anesthesia for cesarean section. The CSE technique enables the successful use of small doses of spinal medication coupled with epidural supplementation, if needed. A recent study compared the spinal administration of 6.5 mg of hyperbaric bupivacaine combined with 2.5 mcg sufentanil versus 9.5 mg of hyperbaric bupivacaine with 2.5 mcg sufentanil for CSE anesthesia for cesarean delivery. Patients in the high-dose group experienced significantly more hypotension than those in the low-dose group (68% versus 16%, p < 0.05), and significantly more patients required treatment. The anesthetic duration was shorter in the low-dose group, which points to the necessity of having an epidural catheter in place.


Combined Spinal–Epidural Technique for Orthopedic Surgery


Patients undergoing orthopedic procedures may also benefit from the CSE technique. A retrospective chart review of 62 total hip arthroplasties found that patients undergoing the CSE technique, single-injection spinal anesthesia, or general anesthesia had the same time interval from anesthesia start to surgical incision (59 minutes), whereas those receiving epidural anesthesia had a longer interval (73 minutes). A randomized controlled study of patients undergoing hip arthroplasty compared time to adequate block and adequacy of muscle relaxation in patients receiving either intrathecal bupivacaine as a single injection, as part of the CSE technique, or through an epidural. Time to adequate block was significantly shorter in the two intrathecal groups: 11 minutes for single-injection spinal and 14 minutes for the CSE technique compared with 36 minutes for the epidural group. Similarly, muscle relaxation was adequate in 100% of those receiving intrathecal bupivacaine compared with 12% of those receiving epidural bupivacaine. Four of the 25 patients receiving epidural bupivacaine were converted to general anesthesia because of inadequate anesthesia, whereas none of the patients receiving intrathecal bupivacaine was. Four of the 25 patients receiving the CSE technique received supplemental bupivacaine via the epidural catheter. There were no differences demonstrated in terms of hemodynamic changes ( p > 0.005) among the three groups.

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Mar 2, 2019 | Posted by in ANESTHESIA | Comments Off on When Should a Combined Spinal–Epidural Be Used?
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