NeuroscienceCharacteristics, incidence, and outcome of patients admitted to the intensive care unit with myasthenia gravis
Introduction
Myasthenia gravis (MG) is an autoimmune condition characterised by skeletal muscle weakness that increases with repetitive muscle use [1] and caused by antibodies to acetylcholine receptors and other relevant targets [1] in the postsynaptic membrane of the neuromuscular junction. Its annual incidence has been reported between 8 and 10 cases per million with a prevalence of 150 to 250 cases per million in the USA [2].
Severe exacerbations of MG can lead to respiratory failure necessitating non-invasive or invasive mechanical ventilation [[1], [2], [3]]. Such exacerbations occur in ~15–20% of patients during their lifetime [4] and typically require admission to an Intensive Care Unit (ICU). However, there are limited data on the characteristics, incidence, and mortality of patients with MG admitted to the ICU. With respect to the mortality rates of such patients, the only data available come from the UK [5] with an in-hospital mortality for this condition of 22%. Such a high mortality makes it important for perception, prognostication, and family discussions to better understand the outcomes of patients with MG requiring ICU admission and, in particular, to confirm this finding [5] or determine its relevance only to UK patients [6]. Accordingly, we studied the epidemiology, characteristics and outcome of patients with MG in Australian and New Zealand (ANZ) Intensive Care Units. We hypothesized that the observed mortality rates in ANZ ICUs would be significantly lower than previously reported.
Section snippets
Methods
This study was approved as a low-risk project by the Ethics Committee of The Alfred Hospital in Melbourne, Australia (number 423/16) which waived the need for informed consent.
We performed a retrospective observational, cross sectional study using data from the ANZ Intensive Care Society (ANZICS) Centre for Outcome and Resource Evaluation (CORE) Adult Patient Database (APD). The ANZICS CORE APD is a high quality binational database containing data from >90% of ANZ ICUs [5]. Patients admitted
Identification of study patients
A total of 712,557 adult patients were admitted to contributing ICUs between 2005 and 2015 with 245 admitted with the primary diagnosis of MG. The total number of deaths was 13 out of 245 (5.3%).
Patient characteristics
Patients' characteristics and differences between survivors and non-survivors are shown in Table 1. Mean age was 60 years and as expected, the ANZROD and APACHE III scores were higher in non-survivors (P < 0.01 for all) as were other markers of comorbidities and physiological abnormalities. Overall, 113
Key findings
We report the characteristics, incidence, and outcome of ICU admissions with the primary diagnosis of (MG) over a decade, using data from the bi-national database for ANZ ICUs. We found that MG was an uncommon primary admission diagnosis; mean age was approximately 65 years, and the yearly population incidence of ICU admission ranged between 0.7 and 2.7 cases per million over the decade, with a significant increase over time. Despite more than a third of patients receiving ventilation, overall
Conclusions
We have conducted the largest epidemiological study of the characteristics, incidence and outcome of patients with MG admitted to ICU in ANZ. We have found that the mortality rate of patients with MG admitted to ICU is low and much lower than previous reported. These findings are important for perception and prognostication and for family discussions in this setting.
Declaration of interests
All authors declare no conflict of interests.
Funding
This study was supported by the Austin Hospital Intensive Care Trust Fund. The Medical Research Institute of New Zealand is supported by Independent Research Organisation Funding from the Health Research Council of New Zealand. This research was conducted during the tenure of a Health Research Council of New Zealand Clinical Practitioner Fellowship held by Dr. Paul Young.
Acknowledgements
MB had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis, including and especially any adverse effects.
DW, MB, DP, GL, LW. PY and RB contributed substantially to the study design, data analysis and interpretation, and the writing of the manuscript.
References (17)
- et al.
Development and implementation of a high-quality clinical database: the Australian and New Zealand Intensive Care Society Adult Patient Database
J Crit Care
(2006) - et al.
Risk prediction of hospital mortality for adult patients admitted to Australian and New Zealand intensive care units: development and validation of the Australian and New Zealand Risk of Death model
J Crit Care
(2013) - et al.
The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies
Int. J. Surg. (London, England)
(2014) Myasthenia gravis
N Engl J Med
(2016)- et al.
Incidence and mortality rates of myasthenia gravis and myasthenic crisis in US hospitals
Neurology
(2009) Myasthenia gravis: management of myasthenic crisis and perioperative care
Semin Neurol
(2004)- et al.
On the concept of myasthenic crisis
J Clin Neuromuscul Dis
(2002) - et al.
Systemic inflammatory response syndrome criteria in defining severe sepsis
N Engl J Med
(2015)