Interscalene block is contraindicated in patients with which condition due to the risk of diaphragmatic paralysis and reduced pulmonary function?

Interscalene block is contraindicated in patients with which condition due to the risk of diaphragmatic paralysis and reduced pulmonary function?

• A. Normal pulmonary function
• B. Borderline pulmonary function
• C. Asthma
• D. Hypertension

Answer: (B)

Interscalene brachial plexus block frequently causes ipsilateral diaphragmatic paralysis because the phrenic nerve lies close to the injection site. When the phrenic nerve is affected, the diaphragm on that side stops moving, which reduces lung volumes—especially inspiratory capacity and functional residual capacity. Most people with normal lungs can tolerate this temporary diaphragmatic dysfunction, but those with limited pulmonary reserve may experience significant drops in ventilation and gas exchange. Therefore, patients with borderline pulmonary function are at higher risk of respiratory compromise from this block, making it relatively contraindicated in that group. Asthma and hypertension don’t directly entail diaphragmatic weakness, so they’re not the primary concern here. Normal pulmonary function is typically tolerated, while borderline function represents the scenario where the risk becomes clinically meaningful.

Interscalene brachial plexus block frequently causes ipsilateral diaphragmatic paralysis because the phrenic nerve lies close to the injection site. When the phrenic nerve is affected, the diaphragm on that side stops moving, which reduces lung volumes—especially inspiratory capacity and functional residual capacity. Most people with normal lungs can tolerate this temporary diaphragmatic dysfunction, but those with limited pulmonary reserve may experience significant drops in ventilation and gas exchange. Therefore, patients with borderline pulmonary function are at higher risk of respiratory compromise from this block, making it relatively contraindicated in that group. Asthma and hypertension don’t directly entail diaphragmatic weakness, so they’re not the primary concern here. Normal pulmonary function is typically tolerated, while borderline function represents the scenario where the risk becomes clinically meaningful.