Dysphagia Diagnosed by Fiberoptic Endoscopy Is Common and Transient in Critical Illness Polyneuropathy: Are There Any Clinical Implications?* Andrea Kleindienst, MD, PhD Francisco Marin, MD Department of Neurosurgery Klinikum Amberg Friedrich-Alexander-University Erlangen-Nürnberg Erlangen, Germany Frank Dodoo-Schittko, PhD Department of Epidemiology and Preventive Medicine University of Regensburg Regensburg, Germany

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ritical illness polyneuropathy (CIP) was described for the first time by Bolton et al (1) in 1984 and is a complication in the ICU occurring in about two thirds of patients with a systemic inflammatory response syndrome (2), associated with an increased ICU stay, prolonged recovery, and an overall mortality rate of 30–70% (3). CIP is diagnosed by the clinical presentation of a progressive, generalized, symmetric muscle weakness resulting in a difficulty of weaning from the ventilator and electrophysiological findings. Underlying structural changes in critical illness neuropathy and myopathy include axonal nerve degeneration, muscle myosin loss, and muscle necrosis. An acquired sodium channelopathy causing reduced muscle membrane and nerve excitability is a possible unifying mechanism underlying the clinical presentation (4). The clinical relevance of dysphagia in the ICU is profoundly affecting more than half of the patients across all medical and surgical diagnostic categories (5). Dysphagia is a known predictor of worse outcome and increases morbidity and mortality substantially since swallowing difficulties are a risk factor for aspiration and pneumonia as well as dehydration and malnutrition (6). Oropharyngeal dysphagia is usually either a primary abnormality related to structural aberrations of the oropharynx or a secondary manifestation of a neuromuscular disease. Possible mechanisms of ICU-acquired swallowing

*See also p. 365. Key Words: critical illness polyneuropathy; dysphagia; fiberoptic evaluation of swallowing; intensive care unit; mechanical ventilation Dr. Kleindienst received grant support from Otsuka Pharma. She is employed by the Klinikum Amberg. Dr. Marin is employed by the Klinikum Amberg. Dr. Dodoo-Schittko has disclosed that he does not have any potential conflicts of interest. Copyright © 2015 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins DOI: 10.1097/CCM.0000000000000783

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disorders include a direct trauma caused by endotracheal or tracheostomy tubes, muscular weakness due to nerve and muscle damage (critical illness neuropathy and myopathy), loss of normal sensation in the oropharynx and larynx, or a generally impaired sensorium (reduced consciousness due to sedation, brain injury, stroke, and delirium). Fiberoptic endoscopic evaluation of swallowing (FEES) has been shown to be safe and effective for assisting in swallowing evaluation, is easy to use, is economic, is very well tolerated, and allows bedside examination (7). In this issue of Critical Care Medicine, Ponfick et al (8) present a prospective observational study evaluating dysphagia in CIP utilizing fiberoptic endoscopy. FEES was performed in 22 patients on days 3, 14, and 28 after admission to the rehabilitation center. Dysphagia was graded with the penetration-aspiration scale by Rosenbek et al (9) and the secretion severity rating scale by Murray et al (10). Functional outcome after rehabilitation was assessed using the functional independence measure (11) and muscle strength by the British Medical Research Council (MRC) scale (12). Pathological swallowing was found in 91% and hypaesthesia of laryngeal structures in 77% of patients during the first FEES. Over the 4-week follow-up period, laryngeal hypaesthesia resolved in 75% and swallowing function recovered completely in 95% of patients. The authors conclude that dysphagia is highly prevalent in CIP due to “learned nonuse” of swallowing muscles and that swallowing function recovered nearly completely within 4 weeks. The presented study provides evidence for the frequent occurrence of dysphagia in patients suffering from critical illness neuropathy. For this purpose, the prevalence of swallowing dysfunction at admission to the rehabilitation center (51 ± 33 days after the onset of the patient’s hospitalization) was determined. Due to the small number of enrolled patients, particularly with regard to epidemiological issues and limited external validity as a result of the treatment in only one neurological rehabilitation unit providing certain specific rehabilitative modalities, a generalization of the presented data is rather difficult. Going above and beyond these descriptive data, only a statistical inference approach may allow predictions for a larger population based on the analyzed dataset and may thus justify the implementation of a change in organizational policy. An inference statistical approach requires the translation of an empirical statement into a statistical hypothesis. What is the empirical statement of the article by Ponfick et al (8), what are possible predictors, and what are the outcome February 2015 • Volume 43 • Number 2

Editorials

measures? Three different types of predictors could be considered: 1) variables linked to the acute ICU or rehabilitative management of CIP (e.g., type of airway protection, invasiveness of ventilation, duration and method of weaning, type and interval of starting feeding, sedation), 2) severity of CIP (MRC score and electrophysiological findings), and 3) patient characteristics (e.g., comorbidities, age). Unfortunately, the authors record several of these variables but fail to perform adequate statistical analysis. The authors emphasize the existence of mechanical ventilation, the presence of a tracheal tube, and the patient’s comorbidities as confounding factors. As a consequence, these confounding or moderating factors should be taken into account in further research. The authors report 21 of 22 patients (95%) recovered completely from dysphagia by week 4 after admission to the rehabilitation center. Hence, their specific treatment of swallowing dysfunction appears to be very effective and would deserve a closer look in terms of a randomized controlled trial. On the other hand, eight of 22 patients (36%) could not be weaned from mechanical ventilation. Based on the underlying structural changes in critical illness neuropathy and myopathy, one would expect respiratory insufficiency and dysphagia to occur simultaneously. A comparison between the time course of weaning and recovery of swallowing function could help to elucidate the pathophysiology of CIP and offer adequate modalities of diagnosis and treatment. The “learned nonuse” of swallowing muscles is the authors’ preferred explanation for the occurrence of dysphagia in critical illness neuropathy. Since the authors are affiliated to a neurological rehabilitation unit, a group comparison with patients suffering from neurological disorders would be suitable confirming their hypothesis. What are the clinical implications of dysphagia diagnosed by fiberoptic endoscopy? The conclusion that swallowing dysfunction is a common and transient complication of CIP does not help to reduce morbidity, mortality, or treatment costs in these patients. What is the underlying pathophysiology of dysphagia in critical illness neuropathy? Is there anything to improve in the acute ICU setting? Shall we avoid tracheostomy or reintubation in order to avoid trauma to the oropharynx,

Critical Care Medicine

larynx, and trachea? Are there any ventilation variables to be improved? Is there an optimal approach to start early swallowing training? Although FEES is a simple and low cost method of visualizing the extent of dysphagia, the survey by Ponfick et al (8) raises a lot of questions to be answered by further studies.

REFERENCES

1. Bolton GC, Allen GD, Filer CW, et al: Absorption, metabolism and excretion studies on clavulanic acid in the rat and dog. Xenobiotica 1984; 14:483–490 2. Johnson KL: Neuromuscular complications in the intensive care unit: Critical illness polyneuromyopathy. AACN Adv Crit Care 2007; 18:167–180; quiz 181 3. Kane SL, Dasta JF: Clinical outcomes of critical illness polyneuropathy. Pharmacotherapy 2002; 22:373–379 4. Latronico N, Bolton CF: Critical illness polyneuropathy and myopathy: A major cause of muscle weakness and paralysis. Lancet Neurol 2011; 10:931–941 5. El Solh A, Okada M, Bhat A, et al: Swallowing disorders post orotracheal intubation in the elderly. Intensive Care Med 2003; 29:1451–1455 6. Zielske J, Bohne S, Axer H, et al: [Dysphagia management of acute and long-term critically ill intensive care patients]. Med Klin Intensivmed Notfmed 2014; 109:516–525 7. Nacci A, Ursino F, La Vela R, et al: Fiberoptic endoscopic evaluation of swallowing (FEES): Proposal for informed consent. Acta Otorhinolaryngol 2008; 28:206–211 8. Ponfick M, Linden R, Nowak DA: Dysphagia—A Common, Transient Symptom in Critical Illness Polyneuropathy: A Fiberoptic Endoscopic Evaluation of Swallowing Study. Crit Care Med 2015; 43:365–372 9. Rosenbek JC, Robbins JA, Roecker EB, et al: A penetration-aspiration scale. Dysphagia 1996; 11:93–98 10. Murray J, Langmore SE, Ginsberg S, et al: The significance of accumulated oropharyngeal secretions and swallowing frequency in predicting aspiration. Dysphagia 1996; 11:99–103 11. Dodds TA, Martin DP, Stolov WC, et al: A validation of the functional independence measurement and its performance among rehabilitation inpatients. Arch Phys Med Rehabil 1993; 74:531–536 12. Compston A: Aids to the investigation of peripheral nerve injuries. Medical Research Council: Nerve Injuries Research Committee. His Majesty’s Stationery Office: 1942; pp. 48 (iii) and 74 figures and 7 diagrams; with aids to the examination of the peripheral nervous system. By Michael O’Brien for the Guarantors of Brain. Saunders Elsevier: 2010; pp. [8] 64 and 94 Figures. Brain 2010; 133:2838–2844

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Dysphagia diagnosed by fiberoptic endoscopy is common and transient in critical illness polyneuropathy: are there any clinical implications?

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