QUANTITATIVE-ANALYSIS OF RESPIRATORY, MOTOR, AND SENSORY FUNCTION AFTER SUPRACLAVICULAR BLOCK

The incidence and clinical significance of hemidiaphragmatic paresis a fter supraclavicular block of the brachial plexus is unknown. Eight he althy volunteers received a supraclavicular block with a standard tech nique using 30 mL of 1.5% lidocaine. Respiratory function was assessed with ultrasound of the diaphragm, respiratory inductive plethysmograp hy (RIP), and pulmonary function tests (PFT) every 20 min. Sensory blo ck was assessed with pinprick and motor block with isometric force dyn amometry every 20 min. Four of eight subjects demonstrated hemidiaphra gmatic paresis on both ultrasound and RIP. No subject experienced chan ges in PFT values or subjective symptoms of respiratory difficulty. Mo tor and sensory blockade outlasted hemidiaphragmatic paresis. These re sults are contrasted to the often symptomatic, 100% incidence of hemid iaphragmatic paresis seen after interscalene block. In this study of h ealthy volunteers, supraclavicular block was associated with a 50% inc idence (95% confidence interval 14-86) of hemidiaphragmatic paresis th at was not accompanied by clinical evidence of respiratory compromise. Implications: Interscalene block is always associated with diaphragma tic paralysis and respiratory compromise. The significance of these si de effects after supraclavicular block is unknown. Using sensitive mea sures of respiratory function, we determined that diaphragmatic paraly sis occurs less often with the supraclavicular approach and is not ass ociated with respiratory difficulties in healthy subjects.