OBJECTIVE
Critical illness polyneuropathy (CIPN) is frequent and important complication in intensive care unit (ICU) patients. Prolonged mechanical ventilation has been associated with the prevalence of CIPN. Phrenic nerve conduction results are highly relevant to the date of weaning from the ventilator. However, there are few studies on the occurrence of CIPN and phrenic nerve conduction study (NCS) in case of critically ill surgical patients. In addition, it is hard to perform a full electrophysiologic study for CIPN diagnosis in critically ill patients. The aim of this study is to investigate the incidence of CIPN and to recognize the correlation between the CIPN and patient’s prognosis when simplified diagnostic criteria are applied. In addition, we investigate the characteristics of phrenic NCS in critically ill patients and investigate the association between the results and patient’s prognosis.
METHODS
This study was performed between November 2016 and May 2018 in surgical ICU of our hospital. Critically ill patients over 18 years of age, who were mechanically ventilated for ≥3 weeks were included. At 3 weeks of mechanical ventilation on ICU patients, they were subjected to the NCS in upper, lower extremities including phrenic nerve and tested muscle strength by using the Medical Research Council (MRC) scale. We employed three versions of the diagnostic criteria depending on the MRC scale and NCS result. (Table 1). We used ventilator-free days at 40 days — defined as days alive and free from mechanical ventilation — to compare patient’s prognosis. Ventilator-free days were then calculated post-nerve conduction study. A ventilator-free day ≥ 1 day was defined as a good prognosis and 0 day was defined as a bad prognosis. Then, we evaluate the correlation between the prevalence of CIPN and patient’s prognosis.
RESULTS
A total of 50 patients were enrolled in the study — the diagnosis of CIPN yielded as the following: 7 of 50 according to criteria A; 13 of 50 according to criteria B; 16 of 50 according to criteria C. As the authors diagnose CIPN on patients by criteria A, B, and C, respectively, the results bring forth the following: CIPN patients according to criteria A yields an odds ratio of 12.1, regarding the prognosis detrimental to patients; an odds ratio of 24.0 by criteria B, and an odds ratio of 12.4 by criteria C. Furthermore, when the amplitude of phrenic nerve compound muscle action potential(CMAP) divided into more than 0.3mV and less than 0.3mV, the prognosis was better in more than 0.3 mV group, though it was not statistically significant.
CONCLUSION
Our results suggest that CIPN is common in critically ill patients and the diagnostic criteria of MRC in conjunction with the tibial and sural nerve conduction study show the most predictive value on the patient’s prognosis. Although there is no statistical significance, it seems like the low value of phrenic CMAP amplitude might be correlated with the poor prognosis. |
