Differential Effect of Targeted Temperature Management Between 32 °C and 36 °C Following Cardiac Arrest According to Initial Severity of Illness: Insights From Two International Data Sets

BACKGROUND

Recent guidelines have emphasized actively avoiding fever to improve outcomes in patients who are comatose following resuscitation from cardiac arrest (ie, out-of-hospital cardiac arrest). However, whether targeted temperature management between 32 °C and 36 °C (TTM32-36) can improve neurologic outcome in some patients remains debated.

RESEARCH QUESTION

Is there an association between the use of TTM32-36 and outcome according to severity assessed at ICU admission using a previously derived risk score?

STUDY DESIGN AND METHODS

Data prospectively collected in the Sudden Death Expertise Center (SDEC) registry (France) between May 2011 and December 2017 and in the Resuscitation Outcomes Consortium Continuous Chest Compressions (ROC-CCC) trial (United States and Canada) between June 2011 and May 2015 were used for this study. Severity at ICU admission was assessed through a modified version of the Cardiac Arrest Hospital Prognosis (mCAHP) score, divided into tertiles of severity. The study explored associations between TTM32-36 and favorable neurologic status at hospital discharge by using multiple logistic regression as well as in tertiles of severity for each data set.

RESULTS

A total of 2,723 patients were analyzed in the SDEC data set and 4,202 patients in the ROC-CCC data set. A favorable neurologic status at hospital discharge occurred in 728 (27%) patients in the French data set and in 1,239 (29%) patients in the North American data set. Among the French data set, TTM32-36 was independently associated with better neurologic outcome in the tertile of patients with low (adjusted OR, 1.63; 95% CI, 1.15-2.30; P = .006) and high (adjusted OR, 1.94; 95% CI, 1.06-3.54; P = .030) severity according to mCAHP at ICU admission. Similar results were observed in the North American data set (adjusted ORs of 1.36 [95% CI, 1.05-1.75; P = .020] and 2.42 [95% CI, 1.38-4.24; P = .002], respectively). No association was observed between TTM32-36 and outcome in the moderate groups of the two data sets.

INTERPRETATION

TTM32-36 was significantly associated with a better outcome in patients with low and high severity at ICU admission assessed according to the mCAHP score. Further studies are needed to evaluate individualized temperature control following out-of-hospital cardiac arrest.

Air-splint pressure effect on soleus muscle alpha motoneuron reflex excitability in subjects with spinal cord injury

OBJECTIVE

This study investigated circumferential pressure effect on soleus motoneuron reflex excitability in subjects with spinal cord injury (SCI).

SETTING

A university neuromuscular research laboratory.

SUBJECTS

Six men with SCI, clinical level above L1. OUTCOME MEASURES AND INTERVENTION: Soleus motoneuron reflex excitability was assessed by measuring the average change in the peak-to-peak amplitude of 10 H-reflexes before (baseline), during (1, 3, and 5min) and after (1, 3, and 5min) pressure application. Pressure was applied to the lower leg by manually inflating an air-splint to a maintained range of 36.7 to 40.8mmHg for 5 minutes, after which it was deflated.

DESIGN

Repeated measures, planned comparison. Dependent variables compared with baseline values only in post hoc tests.

RESULTS

A one-way analysis of variance for repeated measures demonstrated significant difference (F6,30 = 4.03; p = .004) in the H-reflex amplitude across test conditions. Post hoc t tests (with Bonferroni's correction for multiple comparisons, p < or = .008) revealed a significant H-reflex amplitude reduction at 1, 3, and 5 minutes of pressure application when measurements were compared with the baseline value. Postpressure measurements returned to baseline; however, the third minute measurement was significantly greater than baseline values.

CONCLUSIONS

Circumferential pressure applied to the lower leg decreased soleus muscle alpha motoneuron reflex excitability in subjects with SCI. This inhibition lasted only as long as the pressure was applied. Circumferential pressure application may be useful when a temporary decrease in muscle activity is a therapeutic goal in patients with SCI.

The effect of topical anesthetics on skin sensation and soleus motoneuron reflex excitability

The effect that topical anesthetics has on cutaneous sensation and on soleus motoneuron reflex excitability was studied in a healthy population. Data were obtained from 16 volunteers (7 men and 9 women) between 20 and 47 years of age. The experiment consisted or recording H-reflexes and Achilles tendon reflexes (ATR) before and after administration of a 20% benzocaine spray or a placebo to the skin of the posterior calf. In addition, a sensory evaluation was conducted to determine objectively the actual quality of anesthesia obtained. Subjects served as their own controls, randomly receiving both the active medication and a placebo. The study was conducted in a single blind fashion with only the experimenter being aware of what medication (active/placebo) was being applied during a given experiment. H-reflex amplitudes increased significantly following the application of benzocaine and the placebo spray compared to control (p < .01). This increase was similar whether the active drug or placebo was administered. No significant difference was shown between active benzocaine and the placebo application. The ATR was not significantly affected by any of the treatment techniques used in this study, although some reduction in reflex amplitude was noted. No change in skin sensibility could be attributed to the topical anesthetic in any subject in this study. It was concluded that benzocaine spray did not have an effect on skin sensation and that the increased motoneuron reflex excitability was more likely in response to a stimulatory action upon cutaneous receptors from the spray technique. It is further suggested that topical anesthetics applied to intact skin may not permeate cutaneous tissue in large enough quantities to have a desensitizing effect.

Effect of air-splint application on soleus muscle motoneuron reflex excitability in nondisabled subjects and subjects with cerebrovascular accidents

We investigated the effect of air-splint pressure on soleus muscle motoneuron reflex excitability in 18 nondisabled subjects with no history of neurological disease and 8 subjects with cerebrovascular accidents (CVAs). Motoneuron reflex excitability was assessed by measuring the percentage of amplitude (peak-to-peak measurement) change in the Hoffman reflex (H-reflex). Pressure was applied for 5 minutes, after which the air-splint was deflated. Ten H-reflexes were recorded and averaged for each subject before pressure application to obtain a baseline value. H-reflexes were also recorded at set intervals during and after pressure application. Two-way analyses of variance for repeated measures were used to compare each group's pressure and postpressure measurements with the baseline value. Significant F tests were followed by post hoc t tests. Analyses of variance were used to compare the nondisabled subjects' H-reflex recordings with those obtained for the subjects with CVAs. The nondisabled subjects demonstrated reductions of 55% at 1 minute, 52% at 3 minutes, and 40% at the fifth minute of pressure application. The postpressure measurements showed increases in the reflex amplitude at 1 and 3 minutes postpressure; however, by the fifth minute, the amplitude was not different from the baseline value. The subjects with CVAs demonstrated reductions of 41% at 1 minute, 48% at 3 minutes, and 52% at 5 minutes of pressure application. None of the postpressure measurements, however, were statistically different from the baseline value. A statistically significant difference was demonstrated between the nondisabled subjects and the subjects with CVAs at the first minute of pressure release.(ABSTRACT TRUNCATED AT 250 WORDS)

Motoneuron excitability modulation after desensitization of the skin by iontophoresis of lidocaine hydrochloride

Soleus motoneuron excitability was monitored after skin desensitization by iontophoresis of lidocaine hydrochloride in able-bodied subjects. Motoneuron excitability was measured by plotting H-reflex recovery curves before and after the application of lidocaine hydrochloride or a placebo. Significant H-reflex augmentation between 50 and 1,000 msec resulted after both iontophoretic application of the drug and the placebo (p less than .05). In addition, H-reflex initial recovery decreased by 20 to 30 msec in 75% of the subjects tested (p less than .05). H-reflex recovery curve facilitation lasted 30 minutes and returned to control values 45 minutes post-iontophoresis. H-reflex facilitation was not significantly different between the drug and the placebo treatments. It was concluded from these results that low-voltage, galvanic electric stimulation associated with iontophoresis predominantly caused the increase in motoneuron excitability, although other peripheral facilitatory factors may have been involved. Furthermore, cutaneous desensitization appeared not to have an effect on motoneuron excitability. This conclusion was based on the observation that similar H-reflex amplitude augmentation resulted after administration of a placebo as well as an active drug.