Anestesia e Pesquisa Clínica
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Patient Susceptibility & Technical Factors Associated with Persistent Diaphragmatic Paralysis after Interscalene Nerve Block

Matthew R Kaufman, Ryan Fields, John Cece, Catarina P Martins, Kameron Rezzadeh, Andrew I Elkwood and Reza Jarrahy

Background and objectives: Interscalene nerve blocks (ISB) have been associated with the rare complication of persistent diaphragmatic paralysis. Little is known regarding patient susceptibility or technical factors that may contribute to the development of this debilitating adverse reaction. Methods: An observational study was performed between 2009 and 2014 to compare two groups of patients who received ISB for upper extremity surgery. Patient demographic factors, co-morbidities, and technical aspects of the nerve block were reviewed and compared in two groups: 50 consecutive patients receiving ISB without consequence at a university-based hospital and affiliated outpatient surgery center (Group I); 29 patients with persistent diaphragmatic paralysis after ISB evaluated and treated at a tertiary referral center (Group II). We analyzed the following patient factors between groups: age, sex, BMI, laterality, history of peripheral or diabetic neuropathy, prior nerve blocks, and underlying cervical spondylosis. An assessment of technical aspects of the nerve block was also performed. Results: In Group I there was 26 females and 24 males with an average age of 55, whereas in Group II there were 4 females and 25 males with an average age of 58. There was no significant difference between groups for BMI (mean=36 vs. 30) or laterality (Left=38% vs. 31%), however there were a significantly higher proportion of males in Group II (p<0.01). No difference was demonstrated between groups for peripheral or diabetic neuropathy, whereas prior ipsilateral blocks and cervical spondylosis were significantly more prevalent in Group II (p<0.01 & p<0.01, respectively). In Group I, 86% of patients received blocks performed with either nerve stimulator (64%) or ultrasound (22%) guidance, and 10% using both modalities. This contrasts to 79% of patients in Group II whose blocks were performed using either nerve stimulator (24%) or ultrasound (55%) guidance, and 6% in combination. Conclusion: Both patient factors and technical aspects of ISB may impact occurrence of persistent diaphragmatic paralysis. Use of ultrasound and nerve stimulator guidance can improve accuracy and reduce associated tissue inflammation, and there should be a redoubling of efforts to ensure technical expertise with these modalities in clinical practice.