Women with severe preeclampsia have remarkably diminished intravascular volumes compared with unafected gravidas (Zeeman, 2009). Conversely, extravascular volume is increased because of the capillary leak caused by endothelial cell activation (Chap. 40, p. 717). his imbalance is manifested as pathological peripheral edema, proteinuria, ascites, and total lung water. For all of these reasons, aggressive volume replacement increases the risk for pulmonary edema, especially in the irst 72 hours postpartum. In one study, Hogg and associates (1999) reported that 3.5 percent of women with severe preeclampsia developed pulmonary edema when preloaded without a protocol limitation to volume. Importantly, this risk can be reduced or obviated with judicious prehydration-usually with 500 to 1000 mL of crystalloid solution. Speciically, in the study by Lucas and colleagues (2001), there were no instances of pulmonary edema among the women in whom the crystalloid preload was limited to 500 mL. Moreover, vasodilation produced by epidural blockade is less abrupt if the analgesia level is achieved slowly with dilute solutions of local anesthetic agents. This allows maintenance of blood pressure while simultaneously avoiding infusion of large crystalloid volumes.
he combination of spinal and epidural techniques has increased in popularity and may provide rapid and efective analgesia for labor and for cesarean delivery. An introducer needle is irst placed in the epidural space. A small-gauge spinal needle is then introduced through the epidural needle into the subarachnoid space-this is called the needle-throughneedle technique (see Fig. 25-3). A single bolus of an opioid, sometimes in combination with a local anesthetic, is injected into the subarachnoid space. The spinal needle is withdrawn, and an epidural catheter is then placed through the introducer needle. A subarachnoid opioid bolus results in the rapid onset of profound pain relief with virtually no motor blockade. he epidural catheter permits repeated analgesia dosing. Miro and associates (2008) compared epidural analgesia with combined spinal-epidural analgesia for labor in 6497 women and found the overall outcomes and complications to be similar for the two techniques. In a randomized comparison, however, Abrao and colleagues (2009) reported that combined spinal-epidural analgesia was associated with a greater incidence of fetal heart rate abnormalities related to uterine hypertonus. Beamon and coworkers (2014) reported similar results .
here is emerging interest in continuous spinal analgesia for relief of labor pain. Arkoosh (2008) randomized 429 laboring women to either continuous spinal or conventional epidural analgesia. Complication rates between these two neuraxial techniq ues did not difer. Tao and colleagues (2015) reported their experiences with 113 women. With a dilute bupivacaine solution for analgesia, they found no cases of peripheral nerve injury and a headache rate of2.6 percent. he utility of continuous spinal analgesia in labor and delivery remains to be further studied.
A local block is occasionally useful to augment an inadequate or "patchy" regional block that was given emergently. Rarely, local iniltration may be needed to perform an emergent cesarean delivery to save the life of a fetus in the absence of anesthesia support (Young, 2012).
In one technique, the skin is iniltrated along the proposed incision, and the subcutaneous, muscle, and rectus sheath layers are injected as the abdomen is opened. Up to a total of 70 mL of 0.5-percent lidocaine with 1 :200,000 epinephrine is prepared for iniltration. Injection of large volumes into the fatty layers, which are relatively devoid of nerve supply, is avoided to limit the total dose of local anesthetic needed.