The impact of local anesthetic distribution on block onset in ultrasound-guided interscalene block.

BACKGROUND: Recent investigations of local anesthetic distribution in the lower extremity have revealed that completely surrounding the sciatic nerve with local anesthetic provides the advantage of more rapid and complete anesthesia in the territory served by the nerve. We hypothesized that a pattern of distribution that entirely envelops the targeted nerve roots during interscalene block would provide similar benefits of more rapid anesthesia onset. METHODS: During interscalene block guided by ultrasound with nerve stimulator confirmation, the pattern of local anesthetic distribution was recorded and later classified as complete or incomplete envelopment of the visible nerve elements in 50 patients undergoing ambulatory shoulder arthroscopic surgery. The pattern was then compared with the extent of block setup at pre-determined intervals, as well as to post-operative pain levels and block duration. RESULTS: Twenty-two patients (44%) had complete envelopment of the nerves in the plane of injection during ultrasound imaging of the interscalene block. There was no difference in the fraction of blocks that were fully set-up at 10 min with regards to complete or incomplete envelopment of the nerves by local anesthetic. All of the patients had complete setup of the block by 20 min. In addition, the post-operative pain levels and duration of block did not vary among the two groups with complete vs. incomplete local anesthetic distribution around the nerves. CONCLUSION: The presence or absence of complete envelopment of the nerve elements in the interscalene groove by local anesthetic did not determine the likelihood of complete block effect at pre-determined time intervals after the procedure.

Process analysis in outpatient knee surgery: effects of regional and general anesthesia on anesthesia-controlled time.

BACKGROUND: The performance of anesthetic procedures before operating room entry (e.g., with either general or regional anesthesia [RA] induction rooms) should decrease anesthesia-controlled time in the operating room. The authors retrospectively studied the associations between anesthesia techniques and anesthesia-controlled time, evaluating one surgeon performing a single procedure over a 3-yr period. The authors hypothesized that, using the anesthesia care team model, RA would be associated with reduced anesthesia-controlled time compared with general anesthesia (GA) alone or combined general-regional anesthesia (GA-RA). METHODS: The authors queried an institutional database for 369 consecutive patients undergoing the same procedure (anterior cruciate ligament reconstruction) performed by one surgeon over a 3-yr period (July 1995 through June 1998). Throughout the period of study, anesthesia staffing consisted of an attending anesthesiologist medically directing two nurse anesthetists in two operating rooms. Anesthesia-controlled time values were compared based on anesthesia techniques (GA, RA, or GA-RA) using one-way analysis of variance, general linear modeling using time-series and seasonal adjustments, and chi-square tests when appropriate. P < 0. 05 was considered significant. RESULTS: RA was associated with the lowest anesthesia-controlled time (11.4 +/- 1.3 min, mean +/- 2 SEM). GA-RA (15.7 +/- 1.0 min) was associated with lower anesthesia-controlled time than GA used alone (20.3 +/- 1.2 min). CONCLUSIONS: When compared with GA without an induction room for outpatients undergoing anterior cruciate ligament reconstruction, RA with an induction room was associated with the lowest anesthesia- controlled time. Managers must weigh the costs and time required for anesthesiologists and additional personnel to place nerve blocks or induce GA preoperatively in such a staffing model.