"Eyeball test" of thermographic patterns for predicting a successful lateral infraclavicular block.

PURPOSE: Increased distal skin temperature can be used to predict the success of lateral infraclavicular (LIC) block. We hypothesized that an "eyeball test" of specific infrared thermographic patterns after LIC block could be used to determine block success. METHODS: In this observational study, five observers trained in four distinct thermographic patterns independently evaluated thermographic images of the hands of 40 patients at baseline and at one-minute intervals for 30 min after a LIC block. Sensitivity, specificity, and predictive values of a positive and a negative test were estimated to evaluate the validity of specific thermographic patterns for predicting a successful block. Sensory and motor block of the musculocutaneous, radial, ulnar, and median nerves defined block success. Fleiss' kappa statistics of multiple interobserver agreements were used to evaluate reliability. RESULTS: As a diagnostic test, the defined specific thermographic patterns of the hand predicted a successful block with increasing accuracy over the 30-min observation period. Block success was predicted with a sensitivity of 92.4% (95% confidence interval [CI], 86.8 to 96.2) and with a specificity of 84.0% (95% CI, 70.3 to 92.4) at min 30. The Fleiss' kappa for the five observers was 0.87 (95% CI, 0.77 to 0.96). CONCLUSION: We conclude that visual evaluation by an eyeball test of specific thermographic patterns of the blocked hands may be useful as a valid and reliable diagnostic test for predicting a successful LIC block.

Blinded observer evaluation of distal skin temperature for predicting lateral infraclavicular block success.

BACKGROUND: Changes in digit skin temperature may be used to predict and determine upper limb nerve block success. We investigated whether a temperature difference between the blocked and the nonblocked hands, simply registered by touching the skin of the 5th and 2nd digit was valid and reliable as a diagnostic test for predicting a successful lateral infraclavicular block. METHODS: Blinded observers investigated temperature difference between the blocked and the nonblocked hands of 40 patients. Sensitivity, specificity, and predictive values of a positive and a negative test were estimated for evaluating the validity of a temperature difference for predicting a successful lateral infraclavicular block defined by sensory and motor block of all 4 major nerves (musculocutaneous, radial, ulnar, and median nerves). κ statistics of interobserver agreement were used for evaluating the reliability of the test. RESULTS: As a stand-alone test, a temperature difference between the corresponding 2nd and 5th digits of the blocked and the nonblocked hands predicted a successful block with a sensitivity of 92% (95 % confidence interval (CI), 83%-97%) and with a predictive value of a positive test of 95% (CI, 86%-98%). Fleiss κ for multiple observers was 0.74, (CI, 0.61-0.87) for the 5th digit and 0.87 (CI, 0.73-0.998) for the 2nd digit, respectively. CONCLUSIONS: We found that a qualitative difference in skin temperature between the blocked and nonblocked hands, measured distally on the 2nd and 5th digits, was a valid and reliable diagnostic test for predicting successful lateral infraclavicular block.

Distal infrared thermography and skin temperature after ultrasound-guided interscalene brachial plexus block: a prospective observational study.

BACKGROUND: Increases in skin temperature may be used as an early predictor of the success of interscalene brachial plexus block (IBPB), but we lack detailed information on the thermographic response. OBJECTIVE: To investigate and characterise the thermographic response after IBPBs. DESIGN: Prospective observational study. SETTING: University hospital and private hospital. PATIENTS: Twenty-nine male and 17 female patients scheduled for ambulatory shoulder surgery. Exclusion criteria were age less than 18 years, body weight more than 120 kg and any coagulation abnormality. INTERVENTIONS: Infrared thermographic imaging of the hand before and at 1 min intervals for 30 min after an ultrasound-guided IBPB with 20 ml ropivacaine 7.5 mg ml. Cooling of both hands was performed to standardise measurements. MAIN OUTCOME MEASURES: Thermographic changes in skin temperature on the dorsum of the hand. RESULTS: Forty-four blocks were successful and two were failures. Four thermographic patterns were observed after successful blocks: the increase in skin temperature was restricted to the thumb (n = 5); increase in skin temperature of the thumb and the second digit (n = 11); increase in skin temperature of the thumb, the second and fifth digits (n = 4); and an increase in skin temperature in all parts of the hand (n = 24). All successful blocks demonstrated a significant (P < 0.0001) increase in median (range) of distal skin temperature of the thumb of 6.6°C (0.7 to 17.2) by 30 min, which was already significant (P < 0.0001) by 5 min. By contrast, skin temperature decreased significantly (P < 0.0001) in the hand after failed blocks and in the contra-lateral non-blocked hand by -1.5°C (-6.2 to 4.2). CONCLUSION: Successful IBPB resulted in four thermographic patterns. Skin temperature always increased on the thumb within 30 min and this increase achieved statistical significance at 5 min after the block.