Axillary block by "selective" injections at the nerves involved in surgery using a peripheral nerve stimulator: a comparison with a "standard" triple-injection technique.

BACKGROUND AND OBJECTIVES: A triple-injection technique (injections at the median, musculocutaneous, and radial nerves) for axillary block affords a high incidence of complete block (all the nerves below the elbow). However, in certain surgeries, only 1 or 2 nerves are involved in the surgical field. The aim of this prospective randomized study was to test the effectiveness of surgical anesthesia of a "selective" approach in which only the nerves involved in surgery were electrically located and injected. METHODS: Three types of surgery were selected. Type 1 included surgery on the fifth finger, type 2 included superficial surgery (without bone involvement) on the palm or on the dorsum of the hand, and type 3 included any surgery on the first 3 fingers. For each type, 138 patients were enrolled and divided into 2 groups: group SEL in which only the nerves involved in the surgical field (1 or 2) were located and injected and group TNS in which a standard triple-nerve stimulation technique was used. RESULTS: A lower rate of surgical anesthesia (84% vs 92%; P G 0.05)was recorded in group SEL considered as a whole: this was mainly due to the significant difference recorded in type 2 surgery (75% vs 93%;P G 0.05). More patients needed intravenous administration of fentanyl for tourniquet pain (18% vs 8%; P G 0.005) and of midazolam for intraoperative anxiety (20% vs 8%; P G 0.005) in group SEL considered as a whole. In type 1, improved patient comfort at block performance(P G 0.05), a 7-min saving on total anesthetic time (P G 0.001), and a higher need for midazolam administration (P G 0.05) were recorded in group SEL. In type 2, a higher need for midazolam administration(P G 0.05) was recorded in group SEL. In type 3, no clinically significant differences between the groups were recorded. CONCLUSIONS: A standard triple-nerve stimulation technique seems to be preferable to the selective approach even when a limited number of nerves are involved in the surgical field.

A comparison of proximal and distal radial nerve motor responses in axillary block using triple stimulation.

BACKGROUND AND OBJECTIVES: Stimulation of the radial nerve at the axilla may cause either a proximal movement (forearm extension) or distal movements (supination, wrist or finger extension). In the most recent studies on axillary block, only a distal twitch was accepted as valid. However, this approach was based only on clinical experience. The aim of this study was to verify if a proximal motor response can be considered a satisfactory endpoint. METHODS: This was a prospective, randomized, double-blinded study. One hundred fifty patients received a triple-injection axillary brachial plexus block in which the radial nerve was located by a proximal (group PROX) or a distal motor response (group DIST). Patients were assessed for sensory and motor block of the branches of the radial nerve by a blinded investigator at 5-minute intervals over 30 minutes. RESULTS: An 81% success rate for anesthetizing the sensory distal branches of the radial nerve was seen in group PROX; a significantly higher success rate was recorded in group DIST (95%). The onset time of sensory block for the distal branches of the radial nerve was significantly shorter in group DIST (9.9 +/- 6 v 15.4 +/- 7 minutes). The time to perform the block was slightly shorter and the localization of the nerve simpler in group PROX. The overall block success rate was not significantly different in the 2 groups. CONCLUSIONS: Local anesthetic injection at the proximal radial twitch significantly reduces the efficacy and prolongs the onset time of the radial nerve block. Searching for distal response is significantly more difficult and time consuming than searching for proximal response. However, it does not significantly increase patient discomfort or adverse effects.

The effect of exogenous epinephrine on the incidence of hypotensive/bradycardic events during shoulder surgery in the sitting position during interscalene block.

UNLABELLED: Sudden hypotensive and/or bradycardic events (HBE) have been reported in 13%-28% of patients undergoing shoulder surgery in the sitting position during interscalene block. The Bezold-Jarisch reflex is the most likely mechanism for these events. It has been hypothesized that exogenous epinephrine might be a key component to the occurrence of HBE. We conducted this prospective, randomized study to verify this hypothesis. Patients received a local anesthetic solution with (Group E; n = 55) or without (Group P; n = 55) epinephrine for interscalene block; no further exogenous epinephrine was administered. Blood pressure control was achieved with IV urapidil, a peripheral vasodilator, as needed. The incidence of HBE was 11% in Group P versus 29% in Group E (P = 0.015). Increased intraoperative heart rate and arterial blood pressure were recorded in Group E (P = 0.000). Urapidil was administered to 13% of Group P and to 31% of Group E patients (P = 0.018). Urapidil administration induced a HBE in 4% of Group P and in 5% of Group E patients. We conclude that exogenous epinephrine is involved in the development of HBE in this setting. IMPLICATIONS: Sudden hypotensive and/or bradycardic events occur during shoulder surgery in the sitting position during interscalene block. In this study, we demonstrated that the presence of epinephrine in the local anesthetic mixture significantly increases the incidence of these events.

Four-injection brachial plexus block using peripheral nerve stimulator: a comparison between axillary and humeral approaches.

UNLABELLED: We conducted this prospective, randomized study to compare the success rate, performance time, and onset time of surgical anesthesia of a four-injection brachial plexus block performed at the axillary (Group Axillary; n = 50) or at the humeral (Group Humeral; n = 50) level using a peripheral nerve stimulator. All patients received 40 mL of a mixture of equal parts of 0.5% bupivacaine and 2% lidocaine. Four patients in Group Axillary and two in Group Humeral were excluded from the study because all of the four nerves were not localized in the allotted time. The incidence of complete block (91% versus 89%), defined as block of all the sensory areas below the elbow, and the onset time of sensory block (15 +/- 6 min versus 16 +/- 7 min) were not different between the groups. The performance time was shorter in Group Humeral (7 +/- 2 min versus 8 +/- 2 min; P < 0.005). Block performance pain was lower in Group Axillary patients (16 +/- 9 min versus 23 +/- 12 min; P < 0.005). For four-injection brachial plexus block, we conclude that both the axillary and the humeral approaches provide a high success rate and a rapid onset of sensory anesthesia; the differences found between the groups could be considered clinically unimportant. IMPLICATIONS: Two methods of brachial plexus block using a nerve-stimulator were compared in a prospective study. A four-injection technique was performed at the axillary or at the humeral level. Both approaches provided a fast onset and a high success rate. The differences found between the groups could be considered clinically unimportant.