By Michael Rubin, MD
Professor of Clinical Neurology, Weill Cornell Medical College
Dr. Rubin reports no financial relationships relevant to this field of study.
SYNOPSIS: Following cardiac surgery, about 6% of patients will suffer a peripheral nerve injury, mostly due to compression, traction,
or nerve ischemia. Proper patient positioning can prevent most of these injuries.
SOURCE: Gavazzi A, et al. Prevalence of peripheral nervous system complications after major heart surgery. Neurol Sci 2016;37:205-209.
Following cardiac surgery, up to 30% of patients may experience diaphragmatic paralysis due to phrenic nerve injury, while up to 15% of patients sustain peripheral nerve injury affecting the arm, usually demyelinating in nature and resolving within weeks. What is the complete spectrum of neuropathy following open-heart surgery, what are the risk factors, and what is its prevalence?
Among 374 consecutive patients admitted to the Cardiac Rehabilitation Unit in Multimedica Hospital, Castellanza, Italy, and examined neurologically after coronary artery bypass grafting, cardiac valvular surgery, or ascending aortic aneurysm repair, patients with suspected peripheral nerve complications underwent nerve conduction studies, needle electromyography, or evoked potential studies. Comorbid conditions included renal failure, diabetes, thyroidopathy, peripheral arterial disease, prior history of peripheral nerve dysfunction, and occurrence of sepsis or respiratory failure postoperatively. Critical illness polyneuropathy was diagnosed if a generalized axonal neuropathy was found, as demonstrated by low compound motor action potential amplitudes and fibrillation potentials on needle examination. Compression neuropathy was diagnosed by standard criteria. Statistical analysis comprised student t-test and chi-square test, with P < 0.05 considered significant.
Only 6.1% (n = 23) demonstrated new peripheral nerve complications, with no correlation found between the type of cardiac surgery and occurrence or type of nerve injury. Diabetes was the sole medical risk factor for developing a peripheral nerve adverse event (P = 0.002), whereas age, gender, and duration of surgery did not play a role. Critical illness polyneuropathy was seen in five patients (1.3%), while three patients with pre-existing peripheral neuropathy experienced worsening, one with diabetic neuropathy and two with idiopathic polyneuropathy. Mononeuropathies were seen in the remainder, including ulnar neuropathy at the elbow (6), carpal tunnel syndrome (4) or brachial plexopathy (4), peroneal neuropathy at the knee (3), lower cranial neuropathy involving the vagus (2), glossopharyngeal (1) or hypoglossal nerve (1), and median neuropathy at Struthers ligament (2) or meralgia paresthetica (2). Injury to the superior laryngeal branch of the vagus resulted in hoarseness and vocal cord and soft palate paralysis, whereas dysphagia and loss of taste and gag reflex resulted from glossopharyngeal nerve injury. In all cases, symptoms and electrodiagnostic abnormalities continued for at least 1 month following surgery, with persistent symptoms particularly in diabetic patients. Patients with critical illness polyneuropathy fared well. Excluding carpal tunnel syndrome from the mix, due to its high prevalence in the general population, 5.8% experienced peripheral nerve complications following surgery, similar to the known prevalence of central nervous system complications following cardiac surgery, and diabetes remained the sole risk factor.
COMMENTARY
Brachial plexus injuries following cardiac surgery last an average of 2-3 months, usually resolve within 1 year, and may be the result of positioning, retractor use and placement, and duration of surgery and cardiopulmonary bypass. Sternal retractors rotate the first rib superiorly, pushing the clavicles posteriorly, compressing the plexus, and typically injuring the medial cord and its major branch, the ulnar nerve. Prolonged cardiopulmonary bypass may result in prolonged nerve ischemia contributing to this injury. Proper patient positioning is central to preventing compression injuries, and padding is essential. Central venous catheter placement may result in hematoma formation, which can also compress the plexus. Radial artery harvesting, in lieu of the saphenous vein, may result in sensory abnormalities in up to 34%, resolving within 3-6 months in almost all, but thumb weakness has been reported in 6%, with decreased grip strength and dexterity. Vasopressor use, particularly dopamine and norepinephrine, may result in digital ischemia, often requiring amputation, but the most common cause of arm ischemia is thromboembolism due to atrial fibrillation, often requiring surgical thrombectomy and anticoagulation.1
REFERENCE
- Dineen HA, et al. Upper extremity complications and concerns in patients with cardiac disease. J Hand Surg Am 2016;41:470-472. http://dx.doi.org/10.1016/j.jhsa.2015.11.023.
Following cardiac surgery, about 6% of patients will suffer a peripheral nerve injury, mostly due to compression, traction, or nerve ischemia. Proper patient positioning can prevent most of these injuries.
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