Dose-Response Relationships for Hemidiaphragmatic Paresis Following Ultrasound-Guided Supraclavicular Block

With traditional landmark-based or nerve-stimulator techniques, the incidence of HDP following supraclavicular blocks is approximately 50-67%. Ultrasound-guided techniques are thought to enhance precision while reducing the volume of anesthetic used, but even then HDP incidence is nearly 60%. To date, no trials have studied the dose-response relationship between local anesthetic volume and degree of HDP.

Patient Selection

30 eligible patients undergoing right upper extremity surgery and eligible for supraclavicular blocks will be recruited at NewYork-Presbyterian/Weill Cornell Medical Center.

Evaluation of HDP

Baseline M-mode recordings of diaphragm function will be made by an anesthesiologist. Patients will perform "voluntary sniff" (VS) tests, or forceful nasal inhales, immediately preceding the brachial plexus blockade, and again at 15 minutes and 30 minutes after the block.

Diaphragmatic excursion from baseline will be measured in centimeters; three measurements will be made and averaged. Hemidiaphragmatic paresis will be defined as greater than or equal to 60% reduction in diaphragmatic excursion, no movement, or paradoxical movement in the VS test.

Evaluation of Pulmonary Function

A bedside negative inspiratory force (NIF) meter will be used to measure negative inspiratory force prior to the block and 30 minutes after the block.

Evaluation of Supraclavicular Block

At the 15- and 30-minute marks, the investigators will assess sensory blockade and motor block in the axial, musculocutaneous, radial, median, and ulnar distributions. Both will be judged on 3-point scales. The investigators will also apply a 0-10 point verbal rating scale to assess dyspnea at 30 minutes. Oxygen saturation will be measured off of supplemental oxygen before the block and 30 minutes after the block.

Following the assessments, patients will have surgery using brachial plexus blockade as the primary anesthetic.

Inclusion criteria

• Undergoing right upper extremity surgery with supraclavicular block as the primary anesthetic
• Age greater than or equal to 18 years of age
• American Society of Anesthesiologists (ASA) physical status 1 to 3
• Able to give informed consent

Exclusion criteria

• Patient refusal for supraclavicular block
• Inability to give informed consent
• Allergy to local anesthetics
• Hemidiaphragmatic dysfunction, suspected or known pulmonary disease
• Neuromuscular disease
• Obstructive or restrictive pulmonary disease
• Medical or anatomic contraindication to supraclavicular blockade as judged by clinician
• Pregnancy