Feasibility and diagnostic accuracy of early electrophysiological recordings for ICU-acquired weakness: an observational cohort study.

BACKGROUND: An early diagnosis of ICU-acquired weakness (ICU-AW) is difficult because disorders of consciousness frequently preclude muscle strength assessment. In this study, we investigated feasibility and accuracy of electrophysiological recordings to diagnose ICU-AW early in non-awake critically ill patients. METHODS: Newly admitted patients, mechanically ventilated ≥2 days and unreactive to verbal stimuli, were included in this study. Electrophysiological recordings comprised nerve conduction studies (NCS) of three nerves and, if coagulation was normal, myography in three muscles. Upon awakening, strength was assessed (ICU-AW: average Medical Research Council score <4), blinded for electrophysiological recordings. Feasibility was expressed as the percentage of recordings that were both possible and had sufficient technical quality. Diagnostic accuracy of feasible (i.e., feasibility >75 %) recordings was analyzed based on cut-off values from healthy controls and from critically ill patients with and without ICU-AW. RESULTS: Thirty-five patients were included (17 with ICU-AW). Recordings were obtained on day 4 (IQR: 3-6). Feasibility was acceptable for ulnar and peroneal nerve recordings, and low for sural recordings and myography. Diagnostic accuracy based on cut-off values from healthy controls was low. When using cut-off values from critically ill patients with and without ICU-AW, the peroneal compound muscle action potential amplitude and ulnar sensory nerve action potential amplitude had good diagnostic accuracy. CONCLUSION: Nerve conduction studies of the ulnar and peroneal nerve are feasible in critically ill patients. The diagnostic accuracy is low using cut-off values from healthy controls. Cut-off values validated specifically for discrimination between critically ill patients with and without ICU-AW may improve diagnostic accuracy.

Hypothermia after CPR prolongs conduction times of somatosensory evoked potentials.

BACKGROUND: To investigate the effect of mild hypothermia on conduction times and amplitudes of median nerve somatosensory evoked potentials (SEP) in patients after cardiopulmonary resuscitation (CPR). METHODS: Patients treated with hypothermia after CPR who underwent SEP recording during hypothermia and after rewarming were selected from a prospectively collected database. Latencies and amplitudes of N9 (peripheral conduction time, PCT), N13, and N20 were measured. The central conduction time (CCT) was defined as peak-peak latency N13-N20. Recordings of 25 patients were assessed by a second observer to determine the intraclass correlation coefficient (ICC). RESULTS: A total of 115 patients were included. The mean body temperature at SEP during hypothermia was 33.1 °C (SD 0.8) and after rewarming 37.1 °C (SD 0.8). Mean latencies of N9, N13, and N20 and mean CCT were longer during hypothermia. There were no consistent differences in amplitudes. There was an almost perfect ICC for assessment of latencies and amplitudes. CONCLUSIONS: This study showed that PCT and CCT of median nerve SEP were prolonged during treatment with hypothermia after CPR compared with after rewarming. Amplitudes did not differ consistently.

Acute posthypoxic myoclonus after cardiopulmonary resuscitation.

BACKGROUND: Acute posthypoxic myoclonus (PHM) can occur in patients admitted after cardiopulmonary resuscitation (CPR) and is considered to have a poor prognosis. The origin can be cortical and/or subcortical and this might be an important determinant for treatment options and prognosis. The aim of the study was to investigate whether acute PHM originates from cortical or subcortical structures, using somatosensory evoked potential (SEP) and electroencephalogram (EEG). METHODS: Patients with acute PHM (focal myoclonus or status myoclonus) within 72 hours after CPR were retrospectively selected from a multicenter cohort study. All patients were treated with hypothermia. Criteria for cortical origin of the myoclonus were: giant SEP potentials; or epileptic activity, status epilepticus, or generalized periodic discharges on the EEG (no back-averaging was used). Good outcome was defined as good recovery or moderate disability after 6 months. RESULTS: Acute PHM was reported in 79/391 patients (20%). SEPs were available in 51/79 patients and in 27 of them (53%) N20 potentials were present. Giant potentials were seen in 3 patients. EEGs were available in 36/79 patients with 23/36 (64%) patients fulfilling criteria for a cortical origin. Nine patients (12%) had a good outcome. A broad variety of drugs was used for treatment. CONCLUSIONS: The results of this study show that acute PHM originates from subcortical, as well as cortical structures. Outcome of patients admitted after CPR who develop acute PHM in this cohort was better than previously reported in literature. The broad variety of drugs used for treatment shows the existing uncertainty about optimal treatment.

The influence of rewarming after therapeutic hypothermia on outcome after cardiac arrest.

INTRODUCTION: Treatment with hypothermia has been shown to improve outcome after cardiac arrest (CA). Current consensus is to rewarm at 0.25-0.5 °C/h and avoid fever. The aim of this study was to investigate whether active rewarming, the rate of rewarming or development of fever after treatment with hypothermia after CA was correlated with poor outcome. METHODS: This retrospective cohort study included adult patients treated with hypothermia after CA and admitted to the intensive care unit between January 2006 and January 2009. The average rewarming rate from end of hypothermia treatment (passive rewarming) or start active rewarming until 36 °C was dichotomized in a high (≥ 0.5 °C/h) or normal rate (<0.5 °C/h). Fever was defined as >38 °C within 72 h after admission. Poor outcome was defined as death, vegetative state, or severe disability after 6 months. RESULTS: From 128 included patients, 56% had a poor outcome. Actively rewarmed patients (38%) had a higher risk for poor outcome, OR 2.14 (1.01-4.57), p<0.05. However, this effect disappeared after adjustment for the confounders age and initial rhythm, OR 1.51 (0.64-3.58). A poor outcome was found in 15/21 patients (71%) with a high rewarming rate, compared to 54/103 patients (52%) with a normal rewarming rate, OR 2.61 (0.88-7.73), p = 0.08. Fever was not associated with outcome, OR 0.64 (0.31-1.30), p = 0.22. CONCLUSIONS: This study showed that patients who needed active rewarming after therapeutic hypothermia after CA did not have a higher risk for a poor outcome. In addition, neither speed of rewarming, nor development of fever had an effect on outcome.

Prognosis of coma after therapeutic hypothermia: a prospective cohort study.

OBJECTIVE: This study was designed to establish the reliability of neurologic examination, neuron-specific enolase (NSE), and median nerve somatosensory-evoked potentials (SEPs) to predict poor outcome in patients treated with mild hypothermia after cardiopulmonary resuscitation (CPR). METHODS: This multicenter prospective cohort study included adult comatose patients admitted to the intensive care unit (ICU) after CPR and treated with hypothermia (32-34°C). False-positive rates (FPRs 1 - specificity) with their 95% confidence intervals (CIs) were calculated for pupillary light responses, corneal reflexes, and motor scores 72 hours after CPR; NSE levels at admission, 12 hours after reaching target temperature, and 36 hours and 48 hours after collapse; and SEPs during hypothermia and after rewarming. The primary outcome was poor outcome, defined as death, vegetative state, or severe disability (Glasgow Outcome Scale 1-3) after 6 months. RESULTS: Of 391 patients included, 53% had a poor outcome. Absent pupillary light responses (FPR 1; 95% CI, 0-7) or absent corneal reflexes (FPR 4; 95% CI, 1-13) 72 hours after CPR, and absent SEPs during hypothermia (FPR 3; 95% CI, 1-7) and after rewarming (FPR 0; 95% CI, 0-18) were reliable predictors. Motor scores 72 hours after CPR (FPR 10; 95% CI, 6-16) and NSE levels were not. INTERPRETATION: In patients with persisting coma after CPR and therapeutic hypothermia, use of motor score or NSE, as recommended in current guidelines, could possibly lead to inappropriate withdrawal of treatment. Poor outcomes can reliably be predicted by testing brainstem reflexes 72 hours after CPR and performing SEP.

Predictive value of neurological examination for early cortical responses to somatosensory evoked potentials in patients with postanoxic coma.

Bilateral absence of cortical N20 responses of median nerve somatosensory evoked potentials (SEP) predicts poor neurological outcome in postanoxic coma after cardiopulmonary resuscitation (CPR). Although SEP is easy to perform and available in most hospitals, it is worthwhile to know how neurological signs are associated with SEP results. The aim of this study was to investigate whether specific clinical neurological signs are associated with either an absent or a present median nerve SEP in patients after CPR. Data from the previously published multicenter prospective cohort study PROPAC (prognosis in postanoxic coma, 2000-2003) were used. Neurological examination, consisting of Glasgow Coma Score (GCS) and brain stem reflexes, and SEP were performed 24, 48, and 72 h after CPR. Positive predictive values for predicting absent and present SEP, as well as diagnostic accuracy were calculated. Data of 407 patients were included. Of the 781 SEPs performed, N20 s were present in 401, bilaterally absent in 299, and 81 SEPs were technically undeterminable. The highest positive predictive values (0.63-0.91) for an absent SEP were found for absent pupillary light responses. The highest positive predictive values (0.71-0.83) for a present SEP were found for motor scores of withdrawal to painful stimuli or better. Multivariate analyses showed a fair diagnostic accuracy (0.78) for neurological examination in predicting an absent or present SEP at 48 or 72 h after CPR. This study shows that neurological examination cannot reliably predict absent or present cortical N20 responses in median nerve SEPs in patients after CPR.

Induced hypothermia and determination of neurological outcome after CPR in ICUs in the Netherlands: results of a survey.

INTRODUCTION: Induction of hypothermia is generally accepted to increase survival of out-of-hospital cardiac arrest, but lack of initiation of this treatment has been frequently reported. When patients remain in coma after treatment with hypothermia, determination of prognosis is difficult. Furthermore, little is known about the methods used in clinical practice to predict outcome after cardiopulmonary resuscitation (CPR). The aim of the present survey was to evaluate self-reported implementation of hypothermia after CPR and the methods used to predict neurological outcome at Intensive Care Units (ICUs) in the Netherlands. METHODS: Between April 2008 and July 2008 an e-mail-invitation for an anonymous web-based 22-question survey was sent to one physician of each ICU in the Netherlands. RESULTS: Of the 97 physicians surveyed, 74 (76%) responded. Thirty-seven (50%) responders always treated patients with hypothermia after CPR, 31 (42%) only when CPR fulfilled several criteria. The most important reason for not using hypothermia (six ICUs) was lack of equipment. Haemodynamic instability was the most cited reason for discontinuing treatment. Neurological outcome was predicted by clinical neurological examination (92%), cortical N20 responses of median nerve somatosensory evoked potentials (SSEP) (94%), an electroencephalogram (56%) or serum levels of neuron-specific proteins (5%). CONCLUSIONS: In the Netherlands, the use of therapeutic hypothermia after CPR is reported by 92% of ICUs which, compared to previous reports, is an exceedingly high percentage. Neurological outcome is reported to be predicted mainly by neurological examination and SSEP or a combination of these and other assessments. The method used varies substantially between ICUs.