American Society of Regional Anesthesia and Pain Medicine May 2015 - (Page 11)

Phrenic Nerve Injury and Interscalene Nerve Block Have We Learned Anything From the Surgical Treatment of Over 150 Cases of Diaphragmatic Paralysis From Multiple Etiologies? D iaphragmatic paralysis tends to be a problematic diagnosis for both the afflicted individual and the treating physician alike. Most patients undergo an extensive cardiac and pulmonary workup as a response to the presenting symptoms, including dyspnea with exertion, orthopnea, chest discomfort, and lethargy.1 Even when there is a possible preceding event or series of events that could be considered likely causes of the paralysis, physicians are often hesitant in their presumptive diagnosis. Compounding the delay and adding to patients' frustration is that many are ultimately told this will be a chronic condition they must learn to live with. Since 2007, we have been treating patients with diaphragmatic paralysis by using a peripheral nerve surgery algorithm. The rationale for this approach is based on the notion that most cases of diaphragmatic paralysis are the result of a phrenic nerve injury. Peripheral nerve injuries throughout the body are readily amenable to repair by using methods originally developed in the 1930s.2 With the advent of microsurgical techniques, the subspecialty of peripheral nerve surgery blossomed owing to the effectiveness of meticulous and delicate repair of nerve injuries.3 Until recently, the primary areas in which these techniques have been applied were limited to nerves of the upper and lower extremities, and facial nerve.4,5 To date, at our tertiary bicoastal referral centers, we have evaluated more than 300 individuals with diaphragmatic paralysis, including over 150 patients who have undergone phrenic nerve surgery. Approximately 30% of those treated have interscalene nerve block (ISB) as their underlying etiology, comprising the most common cause of diaphragmatic paralysis in our patient population.6 include electromyography/nerve conduction studies (EMG/NCS), sniff testing, magnetic resonance imaging (MRI), and pulmonary function testing. Although the sniff test usually confirms the diagnosis, the EMG/ NCS provides quantitative information regarding the phrenic neuropathy. Thus, it is often possible to characterize the severity of the nerve injury by analyzing nerve conduction velocities and motor amplitudes. Matthew R. Kaufman, MD, FACS Intraoperative findings often suggest Codirector, Center for the sequelae of an inflammatory event(s) Treatment of Paralysis and such as compressive adhesions Reconstructive Nerve Surgery, from adjacent vascular or fibrous Jersey Shore University Medical structures and nerve torsion or Center, Neptune, New Jersey displacement from extensive fibrosis Voluntary Clinical Assistant (Figure 1). Alternatively, microscopic Professor of Surgery visualization of segmental atrophy David Geffen UCLA Medical and nerve sheath hyperemia, when Center, Los Angeles, California present as the most significant discernible abnormality, may Section Editor: be indicative of nerve anoxia Steven Orebaugh, MD from other causes (ie, adverse pharmacologic effect) (Figure 2). Another common finding is diffuse (nonsegmental) atrophy that is exemplified by a visible reduction in the diameter of the phrenic nerve throughout its course in the neck, a finding that could suggest an underlying cervical radiculopathy. A combination of microscopic visualization and intraoperative nerve threshold testing provides the most comprehensive manner in which to assess nerve pathology, and we are often able to ascertain whether there is one process or a combination of factors contributing to the absence of diaphragmatic activity. "Perhaps there should be equivalent emphasis placed on patient screening to determine those who may be more susceptible to ISBrelated complications" Presurgical evaluation and operative intervention provide us with a possibility to reverse the paralysis and an opportunity to investigate the pathologic process. Initially, we ask for a detailed history in an attempt to identify possible etiologies, especially the temporal relationship between antecedent event(s) and onset of respiratory symptoms. Review of our extensive database of patients with diaphragmatic paralysis has allowed us to assess whether certain preexisting conditions may be associated with a susceptibility to phrenic nerve injury. Our preoperative evaluations The analysis of our subset of patients with diaphragmatic paralysis after ISB raises several considerations regarding predisposing conditions, the pathologic process, and prospects for treatment. Our prior report (Anesthesiology, August 2013) was a case series of patients with diaphragmatic paralysis after ISB and suggested an inadvertent mechanical or pharmacologic insult to the phrenic nerve.7 Subsequent to this report, we have had the opportunity to exponentially increase our experience with this patient population and intend on updating the original series once outcome data are collected. American Society of Regional Anesthesia and Pain Medicine 2015 11 3

Table of Contents for the Digital Edition of American Society of Regional Anesthesia and Pain Medicine May 2015

President’s Message
Pharmacogenetics in Monitoring of Chronic Pain Patients: Are We There Yet?
Phrenic Nerve Injury and Interscalene Nerve Block: Have We Learned Anything From the Surgical Treatment of Over 150 Cases of Diaphragmatic Paralysis From Multiple Etiologies?
An Exercise in Negotiation: The Success of the Pain Medicine Fellowship Match
Regional Analgesia for Patients with Acute Rib Fractures
Application of Regional Anesthetic Techniques for Cancer Pain

American Society of Regional Anesthesia and Pain Medicine May 2015