Paravertebral Blockade for Minor Breast Surgery

A comparison of regional versus general anesthesia for ambulatory anesthesia: a meta-analysis of randomized controlled trials

Both regional anesthesia and general anesthesia have been proposed to provide optimal ambulatory anesthesia. We searched MEDLINE and other databases for randomized controlled trials comparing regional anesthesia and general anesthesia in ambulatory surgery patients for meta-analysis. Only major conduction blocks were considered to be regional anesthesia. Regional anesthesia was further separated into central neuraxial block and peripheral nerve block. Fifteen (1003 patients) and 7 (359 patients) trials for central neuraxial block and peripheral nerve block were included in the meta-analysis. Both central neuraxial block and peripheral nerve block were associated with increased induction time, reduced pain scores, and decreased need for postanesthesia care unit analgesics. However, central neuraxial block was not associated with decreased postanesthesia care unit bypass or time or reduced nausea despite reduced analgesics, and it was associated with a 35-min increase in total ambulatory surgery unit time. In contrast, peripheral nerve block was associated with decreased postanesthesia care unit need and decreased nausea but, again, not with decreased ambulatory surgery unit time. This meta-analysis indicates potential advantages for regional anesthesia, such as decreased postanesthesia care unit use, nausea, and postoperative pain. Although these factors have been proposed to reduce ambulatory surgery unit stay, neither central neuraxial block nor peripheral nerve block were associated with reduced ambulatory surgery unit time. Other factors, such as unsuitable discharge criteria and limitations of meta-analysis, may explain this discrepancy.

Peripheral Nerve Block Techniques for Ambulatory Surgery

Peripheral nerve blocks (PNBs) have an increasingly important role in ambulatory anesthesia and have many characteristics of the ideal outpatient anesthetic: surgical anesthesia, prolonged postoperative analgesia, and facilitated discharge. Critically evaluating the potential benefits and supporting evidence is essential to appropriate technique selection. When PNBs are used for upper extremity procedures, there is consistent opioid sparing and fewer treatment-related side effects when compared with general anesthesia. This has been demonstrated in the immediate perioperative period but has not been extensively investigated after discharge. Lower extremity PNBs are particularly useful for procedures resulting in greater tissue trauma when the benefits of dense analgesia appear to be magnified, as evidenced by less hospital readmission. The majority of current studies do not support the concept that a patient will have difficulty coping with pain when their block resolves at home. Initial investigations of outpatient continuous peripheral nerve blocks demonstrate analgesic potential beyond that obtained with single-injection blocks and offer promise for extending the duration of postoperative analgesia. The encouraging results of these studies will have to be balanced with the resources needed to safely manage catheters at home. Despite supportive data for ambulatory PNBs, most studies have been either case series or relatively small prospective trials, with a narrow focus on analgesia, opioids, and immediate side effects. Ultimately, having larger prospective data with a broader focus on outcome benefits would be more persuasive for anesthesiologists to perform procedures that are still viewed by many as technically challenging.

The number of injections does not influence local anesthetic absorption after paravertebral blockade

PURPOSE

The aims of this study are to determine if the injection of a single large dose of local anesthetics into the paravertebral space increases the risks of inducing toxicity compared with multiple small injections and to describe ropivacaine plasma concentrations resulting from paravertebral blockade.

METHODS

Paravertebral blockade was performed using a solution of 10 mL ropivacaine 0.75%, 10 mL lidocaine CO2 2% plus 0.1 mL epinephrine 1:1000 either by a single injection at T3 or T4 (Group S, n = 6) or by five injections of 4 mL each at T2 to T6 (Group M, n = 8). Blood samples were taken at zero, five, ten, 15, 20, 30, 45, 60 and 90 min and at two, three, four, five, six and eight hours. Ropivacaine and lidocaine plasma concentrations were measured by high performance liquid chromatography.

RESULTS

Maximal plasma concentrations were comparable for lidocaine: 2.6 +/- 1.3 (S) vs 2.6 +/- 0.8 microg x mL(-1) (M) and for ropivacaine: 1.3 +/- 0.2 (S) vs 1.3 +/- 0.1 microg x mL(-1) (M). Area under the plasma concentration-time curve was higher in Group M for lidocaine: 577.6 +/- 146.1 vs 401.7 +/- 53.2 mg x min(-1) x mL(-1) (P = 0.04) but similar for ropivacaine: 381.1 +/- 95.4 (M) vs 363.1 +/- 85.3 mg x min(-1) x L(-1) (S).

CONCLUSIONS

The injection of a single large bolus of local anesthetics into the paravertebral space does not increase its absorption. Maximal ropivacaine plasma concentrations resulting from paravertebral blockade are similar to those reported with equivalent doses of bupivacaine.