MORTALITY

No contemporary RCTs are designed primarily to assess differences in mortality after regional anesthesia versus GA for THA or TKA. Because death is such a rare occurrence in modern anesthetic practice, prohibitively large numbers of patients would be required for study to determine the effects of anesthetic technique on patient mortality. In a widely cited meta-analysis of 141 clinical trials (almost 10,000 patients in total) comparing CNB or GA for a variety of surgery types (mostly orthopedic), Rodgers and colleagues²⁵ found that overall mortality was reduced by one third (odds ratio [OR], 0.70; 95% confidence interval [CI], 0.54–0.90) in patients allocated to CNB. Furthermore, Rodgers and colleagues²⁵ demonstrated that overall mortality was reduced regardless of whether neuraxial blockade was continued after surgery.²⁵ For epidural analgesia after THA, Wu and colleagues²⁶ similarly found no reduction in mortality compared with systemic analgesia after reviewing a random sample of 23,136 patients from a national Medicare claims database between 1994 and 1999. It may be that any observed reduction in mortality conferred by regional anesthesia is due to the surgical anesthetic rather than postoperative analgesia.

DEEP VENOUS THROMBOSIS AND PULMONARY EMBOLISM

It has long been thought that CNB can decrease the incidence of deep venous thrombosis (DVT) rates by enhancing lower extremity venous blood flow,³³ and perhaps “washing out” the thrombogenic load accumulated during surgery. In addition, epidural analgesia and CPNB each facilitate postoperative rehabilitation after THA and TKA,^14–16 which may indirectly prevent DVT formation. Mauermann and colleagues²⁸ reported a meta-analysis of 10 studies examining the incidences of DVT and pulmonary embolism (PE) in patients randomized to CNB or GA for THA. The pooled data revealed a significantly lower risk for DVT (OR, 0.27; 95% CI, 0.17–0.42) and PE (OR, 0.26; 95% CI, 0.12–0.56) for patients who received CNB in comparison with those who received GA.

Importantly, among the 10 RCTs included in Mauermann and colleagues’²⁸ meta-analysis, 8 were carried out before 1990 when routine thromboprophylaxis was not commonplace. In only 1 of these 10 trials did patients receive heparin thromboprophylaxis. However, after the introduction of routine thromboprophylaxis, there appears to be no significant difference in the incidence of DVT and PE for patients undergoing THA (see Table 79-1). For TKA, only two studies^21,34 currently reviewed showed a decreased incidence of DVT in favor of regional anesthesia, and these without chemical thromboprophylaxis. Furthermore, none of the TKA studies indicated that the incidence of PE is affected by anesthetic technique (see Table 79-2). It therefore remains questionable whether regional anesthesia offers any additive effect in reducing DVT and PE when used in combination with modern routine thromboprophylaxis.

BLOOD LOSS

In a meta-analysis investigating the effects of CNB on surgical blood loss, Joanne Guay³⁵ found that CNB for THA significantly reduced the likelihood of transfusion by three fourths (OR, 0.25; 95% CI, 0.11–0.53). Peripheral vasodilation most likely accounts for any observed blood-sparing effects of CNB for THA. By contrast, however, we found conflicting results in the contemporary literature for intraoperative bleeding and transfusion requirements in patients receiving regional anesthesia either alone or in combination with GA for THA (see Table 79-1). For TKA, the contemporary literature demonstrates no significant difference in intraoperative blood loss with regional anesthesia compared with GA, and this lack of effect is most likely due to the use of an intraoperative tourniquet.

DURATION OF SURGERY

Mauermann and colleagues’²⁸ meta-analysis demonstrated a modest, but significant, decrease in surgical time with CNB compared with GA for THA. This difference may be a reflection of the reduction in bleeding afforded by CNB and, by extension, a “drier” operative field. Among the studies currently reviewed, the duration of surgery was not influenced by the type of anesthetic for THA or TKA (see Tables 79-1 and 79-2). However, none of these studies considered the total operating room time that includes anesthetic intervention. Endless efforts to improve operating room efficiency have spawned modifications of how anesthetic services are delivered, such as the introduction of a “block room” or anesthesia induction room where regional techniques are performed before operating room entry. These models have been shown to reduce the anesthesia-related operating room time when compared with GA^22,36 and may prove cost-saving in the future.³⁷

PAIN

Choi and colleagues’²⁴ meta-analysis examines the efficacy of postoperative lumbar epidural analgesia compared with systemic analgesia after THA or TKA. These authors hesitantly conclude that epidural analgesia affords superior pain relief for up to 6 hours after surgery compared with conventional systemic analgesia. One important limitation of this meta-analysis is that all patients, whether THA or TKA, were analyzed in aggregate despite important differences between these surgical procedures, especially concerning the severity of postoperative pain.

Our review identified only four recently published RCTs that investigated regional anesthesia versus systemic analgesia for THA (see Table 79-1). It appears that the analgesic benefit of regional anesthesia is short-lived and does not confer extended benefit once the local anesthetic recedes or the infusion ceased. However, in one THA study, there was a significant reduction in morphine consumption beyond the expected duration of action of the local anesthetic, possibly suggesting a pre-emptive analgesic effect of regional anesthesia. For TKA, epidural analgesia, single-injection femoral nerve block (FNB), and continuous catheter-based FNB can each improve postoperative pain control compared with systemic analgesia (see Table 79-2).^{14,15,38–45}