Clinical trial NCT01309360: Ultrasound-guided Axillary Plexus Block - Dose Reduction of Prilocaine
Official title: Ultrasound-guided Block of the Brachial Plexus Using Prilocaine: Effects of Local-anesthetic Dose Reduction on Parameters of Block Quality and Adverse Effects in Outpatients
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: PHASE4
Conditions: Other Surgical Procedures
Keywords: ultrasound
methaemoglobin
prilocaine
regional anesthesia
ASA risk groups I-II
adult outpatients
surgical spectrum covered procedures
distal forearm
hand
Lead sponsor: Helios Research Center
Sponsor class: OTHER
First posted: 2011-03-07
Enrollment: 120
Sex: ALL
Minimum age (years): 18
Maximum age (years): 75
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Allocation: NON_RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

Brief summary: Clinical aim: Does reducing the dose of local anesthetic in ultrasound-guided axillary plexus anesthesia have any effect on the success rate and additional parameters of block quality? Methodology: In this prospective cohort study three groups of 40 outpatients each were administered dosages of 1% prilocaine of either 40mL, 30mL or 20mL for axillary plexus anesthesia. Met-Hb was measured prior to administration of the block and then hourly until the Met-Hb concentration fell. Parameters of block quality and any adverse effects were recorded. The level of significance was defined with α ≤ 0.05.

Detailed description: Background

With the availability of high resolution portable ultrasound equipment, the use of sonography in the field of anesthesia has become more widespread in recent years. The investigators would like to draw attention to a meta-analysis of prospective randomized studies by Abrahams et al. as being representative of the numerous publications available. Compared to nerve stimulation, ultrasound-guided nerve blocks have a higher success rate with significantly fewer vascular punctures and shorter procedure times. However, the administration of ultrasound-guided regional anesthesia necessitates considerable equipment acquisition and training expenses. Nevertheless, the suggested benefits resulting from savings in time and local anesthetic, increased patient satisfaction and avoidance of complications should be considered in addition to the results from Abrahams et al.

The aim of the present work was to investigate whether an ultrasound-guided block combined with a reduced dose of the local anesthetic prilocaine altered the success rate or other parameters of block quality. Any adverse effects and the methaemoglobin concentration were also recorded.

Methodology

After receiving ethics committee approval and after informing patients, ultrasound-guided axillary plexus anesthesia was carried out on 120 adult outpatients in ASA risk groups I-II. The surgical spectrum covered procedures on the distal forearm or the hand (carpal tunnel syndrome, ganglion extirpation, removal of material, etc.). Provision of information and inclusion in the study was done in the anesthesia outpatients' clinic as part of the standard preoperative preparation. Prior to administering the regional anesthesia the investigators administered midazolam as a premedication by mouth (3,75-7,5mg) or intravenously (2-3mg). Application of the local anesthesia was done prospectively and single blind in 3 cohorts with decreasing dosage. The patients received either 400mg (group A), 300mg (group B) or 200mg (group C) of prilocaine 1%. The block was performed under sterile conditions using a portable ultrasound device (Sonosite S-Nerve) and a 24 G short bevel cannula with flexible tubing. The block was performed using combined out-of-plane (n. musculocutaneous) and in-plane techniques (n.radialis, n.medianus, n.ulnaris), usually from a single puncture site. The outpatients were cared for in the anesthesia care unit preoperatively and postoperatively until their discharge. NIBP, pulse oxymetry and ECG were continuously monitored. The discharge criteria were widespread regression of the block with a subjective feeling of well-being including adequate analgesia and stable vital signs with methemoglobin (Met-Hb) concentrations ≤ 5%. Met-Hb levels were measured using spectrophotometry prior to the anesthesia (baseline value) and then hourly after performing the block until a clear decrease became apparent. A complete sensory block of all 4 nerves within 60 minutes of administration of the local anesthetic was rated as a successful block.

For the statistical analysis the investigators selected distribution-free, nonparametric test methods. The Mann-Whitney U test was used when comparing 2 groups and the Kruskal-Wallis test or Fisher's exact test was used when comparing more than 2 groups. The level of significance was defined with α ≤ 0.05. With multiple paired comparisons the significance level was adjusted using the Bonferroni correction. The Bravais-Pearson correlation coefficient rho describes the relationship between the maximum Met-Hb value and the weight-based prilocaine dose in mg/kg.

Eligibility criteria: Inclusion Criteria:

* elective surgery on the distal forearm or the hand
* adult outpatients, age 18-75 years old
* ASA-risk groups I-II (American Society of Anesthesiologists)
* Body Mass Index 17-35
* informed consent

Exclusion Criteria:

* severe coagulopathy
* local or systemic inflammatory response
* ASA-risk groups ≥ Grad III
* severe anemia
* heart failure
* manifest shock
* other drugs with influence on methaemoglobinemia (nitrates, sulfonamides etc.)
* domestic care after surgery not ensured
* drug allergy : local anesthetics
* severe polyneuropathy
* pregnancy, lactation period
* participation in other studies
* non-cooperative patients
* addiction to drugs or alcohol

Primary outcomes:
measure: Number of Participants With Complete Sensory Block
timeFrame: 60 minutes after administration of the local anesthetic
measure: Number of Participants With Complete Motor Blocks
timeFrame: Within 60 minutes after administration of the local anesthetic
measure: Onset Time.
timeFrame: within 60 minutes after administration of the local anesthetic
Secondary outcomes:
measure: Maximum Concentrations of Methemoglobin
timeFrame: 0,1,2,3,4 hours post-dose
measure: Number of Participants With Objective Adverse Events as a Measure of Safety and Tolerability
timeFrame: Outpatients were followed for the duration of hospital stay, an average of six hours.
measure: Number of Participants With Subjective Adverse Events as a Measure of Safety and Tolerability.
timeFrame: Outpatients were followed for the duration of hospital stay, an average of six hours.
Other outcomes:
Locations:
Study officials:
affiliation: Klinik für Anästhesiologie und Intensivtherapie, Helios Kliniken Schwerin, Wismarsche Strasse 393-7, DE-19049 Schwerin
name: Ronald Seidel, Dr. med.
role: PRINCIPAL_INVESTIGATOR
affiliation: Klinik für Anästhesiologie und Intensivtherapie, Helios Kliniken Schwerin, Wismarsche Strasse 393-7, DE-19049 Schwerin
name: Georg Rehmert, Dr.med.
role: STUDY_DIRECTOR
References: