How to Evaluate Patients Before Performing Brachial Plexus Block: A Comprehensive Preoperative Guide

Brachial plexus block is a regional anesthesia technique commonly used for upper limb surgeries. While it offers effective pain control with fewer systemic side effects compared to general anesthesia, proper patient evaluation prior to the procedure is essential for safety and optimal outcomes. A comprehensive pre-anesthetic assessment includes routine diagnostic tests such as blood biochemistry panels, electrocardiograms (ECG), and chest X-rays. These evaluations help anesthesiologists understand the patient's overall health status, ensuring that anesthesia is tailored not only to the surgical site but also to the individual's physiological condition.

Key Laboratory Tests and Systemic Assessments

Blood work plays a critical role in identifying underlying conditions that could complicate anesthesia. Basic metabolic panels assess kidney function, electrolyte balance, and glucose levels—factors that influence how the body processes anesthetic agents. Liver function tests are equally important, as most local anesthetics are metabolized hepatically. Impaired liver function can lead to prolonged drug action and increased risk of toxicity.

In addition to organ function, coagulation status must be carefully evaluated. Platelet count and clotting parameters, including PT, aPTT, and INR, should be reviewed to minimize the risk of hematoma formation at the injection site. Since brachial plexus blocks involve needle placement near major nerve bundles and vascular structures, even minor bleeding can result in serious complications such as nerve compression or airway compromise due to expanding neck hematomas—especially in interscalene or supraclavicular approaches.

Respiratory Considerations and Nerve-Specific Risks

One of the most significant concerns during brachial plexus blockade is its potential impact on respiration. The phrenic nerve, which innervates the diaphragm, often lies in close anatomical proximity to the brachial plexus—particularly in interscalene and supraclavicular techniques. As a result, unintended phrenic nerve block is common, leading to hemidiaphragmatic paralysis and reduced pulmonary function.

Special Attention for High-Risk Patients

This becomes particularly dangerous in elderly patients or those with pre-existing respiratory conditions such as COPD, emphysema, or restrictive lung disease. In these individuals, a drop in forced vital capacity (FVC) or peak expiratory flow rate can precipitate respiratory insufficiency or failure. Therefore, thorough pulmonary evaluation—including spirometry when indicated—is strongly recommended before proceeding with certain types of brachial plexus blocks.

To mitigate this risk, alternative approaches like the axillary brachial plexus block may be preferred. This technique targets the distal branches of the plexus below the clavicle and carries virtually no risk of phrenic nerve involvement, making it a safer option for patients with compromised respiratory function.

Individualized Anesthesia Planning Based on Patient Profile

Beyond coagulation and respiratory function, the anesthesiologist must consider the patient's full medical history, including cardiac, renal, and neurological status. Patients with chronic kidney disease, for example, may have altered protein binding and delayed clearance of local anesthetics, increasing susceptibility to systemic toxicity—even at standard doses.

Local anesthetic systemic toxicity (LAST) is a rare but life-threatening complication characterized by seizures, arrhythmias, and cardiovascular collapse. To prevent this, dosage adjustments are crucial in patients with hepatic or renal impairment. Using lower concentrations, combining shorter-acting agents, or opting for ultrasound-guided precise delivery can enhance safety without sacrificing efficacy.

In summary, successful brachial plexus block begins long before the needle touches the skin. A meticulous pre-procedure evaluation encompassing coagulation profiles, organ function, respiratory capacity, and individual risk factors allows clinicians to select the safest and most effective approach. By personalizing the anesthetic plan, healthcare providers can maximize pain relief while minimizing complications—delivering better outcomes and improved patient satisfaction.