Cardiovascular responses to static muscle contraction in patients with brachial plexus injury treated with intercostal nerve transfer.

Pressor response is carried in afferent fibers of somatic nerves to increase blood pressure (BP) and heart rate (HR) during static exercise in humans. However, there is no information that peripheral responses restore muscle contraction with nerve transfer operation. In this study, we aimed to assess isometric exercise-induced pressor responses in patients with brachial plexus injury (BPI) after intercostal nerve transfer (ICNT) to restore elbow flexor muscles. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and HR during 2-min sustained isometric muscle contraction of elbow flexors at 20% and 35% of maximal voluntary contraction (MVC) on the unaffected side and the ICNT side, were measured in seven subjects with BPI treated with ICNT. SBP, DBP, and HR during 2-min sustained isometric muscle contraction of elbow flexors at 20% of MVC on the unaffected side were similar to those recorded before and after the exercise. However, the same variables increased significantly (p<0.001) during a similar type of exercise at 35% MVC on the unaffected side. On the ICNT side, no significant differences were noted in elbow flexors at 20% and 35% MVC. Isometric static exercise at 35% of MVC did not induce pressor and HR changes on the ICNT side. The difference in the responses between the two sides could have been caused by incomplete recovery of afferent nerve function following nerve repair, despite the restoration of efferent nerve function. Alternatively, the HR and BP responses to static contraction may depend upon the active muscle mass.