Neuronal Injury After Repeated Brief Cardiac Arrests During Internal Cardioverter Defibrillator Implantation Is Associated With Deterioration of Cognitive Function

Single tests of implantable cardioverter defibrillators can be performed in selected patients at a low risk of neuronal damage

BACKGROUND

Defibrillator testing (DFT) is still used in selected patients to ensure adequate therapy. To do so, ventricular fibrillation is induced and terminated by the implanted cardioverter defibrillator (ICD). Studies have shown increases in neuronal damage markers without a measurable clinical effect in patients after defibrillator threshold testing with multiple shocks.

OBJECTIVE

The aim of this study was to measure clinical outcomes, neuronal damage parameters (NSE and S100), and intraoperative cerebral perfusion (Doppler, near infra-red spectroscopy [NIRS]) in patients undergoing single DFT after transvenous ICD implantation and comparing them to untested patients.

METHOD

We included 23 patients. Nine underwent surgery with a single DFT, 14 were not tested. Cognitive impairment was tested using the Mini-Mental-Status Test (MMST) and the DEMTECt 24 h prior and postsurgery. We also measured S100 and Neuron-Specific Enolase (NSE) at these timepoints. During surgery we measured medial cerebral artery velocity and cerebral tissue oxygen saturation (rSO₂ ).

RESULTS

We found no significant differences between the patient groups except for a significant increase in mean arterial blood pressure and an increase in rSO₂ after testing. One patient with cerebral vasculopathy had a significant increase in his NSE values without showing clinical symptoms. This patient also had low rSO₂ measurements and a decrease in medial cerebral artery velocity after DFT, other than the other patients.

CONCLUSION

Single DFT did not lead to signs of neuronal damage or cognitive impairment except in one case with pre-existing cerebral vasculopathy. Therefore, our results support the use of DFT in carefully selected patients.

Prediction of cognitive dysfunction after resuscitation - a systematic review

Cardiac arrest (CA) due to cardiovascular disease is the leading cause of death in developed countries. It is estimated that over 350,000 people in Europe suffer from out-of-hospital cardiac arrest. According to the literature, the longer the episode of cardiac arrest, the greater the risk of cognitive impairment, especially short-term memory, as well as immediate and delayed recall. Other common dysfunctions include attention deficits and executive function disorders. The aim of this systematic review was to summarize current research on cognitive impairment in patients after sudden cardiac arrest. The electronic databases PubMed/MEDLINE, OVID, Web of Science, and EBSCO were searched using the following key words: 'sudden cardiac arrest', 'out-of-hospital cardiac arrest', 'cognitive function', 'cognitive impairment', 'functional outcome', 'cardiopulmonary resuscitation'. The most recent studies from the last 7 years (2011-2018) were included. Cognitive disorders occurred in a broad range of cases: from 13% to even 100%. In one study, cognitive deficits did not occur at all. Amongst the reviewed articles only two studies were carried out on a large group of patients. The remaining studies were conducted on a small group of respondents; therefore there was no possibility to generalize the results to the entire population. The areas in which the most cognitive impairment occurred were memory, executive functions and visual-motor skills. One of the conclusions derived from the reviewed literature is the importance of continuous training of cognitive functions, especially for people with cardiovascular risk.

Cognitive impairment after sudden cardiac arrest

Aim

To evaluate the incidence and severity of the impairment of selected cognitive functions in patients after sudden cardiac arrest (SCA) in comparison to patients after myocardial infarction without SCA and healthy subjects and to analyze the influence of sociodemographic and clinical parameters and the duration of cardiac arrest on the presence and severity of the described disorders.

Material and methods

The study group comprised 30 cardiac arrest survivors, the reference group comprised 31 survivors of myocardial infarction without cardiac arrest, and the control group comprised 30 healthy subjects. The Mini-Mental State Examination (MMSE), the Digit Span test from the Wechsler Adult Intelligence Scale, Lauretta Bender’s Visual-Motor Gestalt Test, and the Benton Visual Retention Test (BVRT) were used to assess the presence of cognitive impairment. An original questionnaire developed by the author was used for overall mental state assessment.

Results

The Bender test demonstrated a significant difference in the presence and severity of visual-motor skills between the study group and the control group, while BVRT and MMSE revealed increased incidence of cognitive impairment in the study group. The Bender and BVRT (D/D)/SS (version D, method D, scaled score) scales indicated cognitive impairment in 53.3% of these patients, while the BVRT (C/A)/SS test indicated cognitive impairment in 40%. For the reference group, the values were 32.3% and 12.9%, respectively. No correlation was found between the severity of cognitive impairment and the duration of cardiac arrest.

Conclusions

Impairment of visual-motor skills, short-term visual memory, concentration, and visual-motor coordination occurs much more frequently and is more severe in individuals after SCA than in healthy individuals. Impairment of memory trace storage and recall after delay occurs more frequently in patients after SCA than in patients after myocardial infarction without cardiac arrest and in healthy individuals. SCA duration did not have any influence on the severity of the described disorders.

Prolonged burst as a new method for cardioverter-defibrillator testing

AIM

To find out whether it is possible to anaesthetize patients safely without analgesia and sedation, using burst pacing prolonged until the patient becomes unconscious.

METHODS

One hundred and four patients undergoing implantation or reimplantation of a cardioverter-defibrillator were included. Patients randomized into Group B underwent prolonged burst pacing without analgesia and sedation. Patients in Group T underwent a T-wave shock under analgesia and sedation. Blood samples for measurement of serum neuron-specific enolase were taken before surgery and 6, 24, and 48 h after the procedure.

RESULTS

From the 104 patients, 51 were randomly assigned to Group B and 53 to Group T. Four patients from Group B were switched to Group T (ventricular fibrillation not induced by burst pacing). The clinical characteristics of both groups were similar. The mean total time of cardiac arrest was significantly longer in Group B (23.0 ± 4.4 s, median 22.7) vs. Group T (10.3 ± 3.0 s, median 10.0), P < 0.0001 (Mann-Whitney U-test). The effectiveness of both induction methods was similar (92.1% in Group B and 100% in Group T). The mean neuron-specific enolase levels after 6, 24, and 48 h were similar in Groups B and T (13.1 ± 6.3 and 11.6 ± 5.8 mg/L, 14.5 ± 7.5 and 13.4 ± 6.0 mg/L, and 14.9 ± 5.9 and 12.2 ± 6.0 mg/L, respectively) as were these levels compared with baseline neuron-specificenolase levels (14.0 ± 5.9 and 13.4 ± 4.0 mg/L, respectively), P = NS for all.

CONCLUSION

Despite a longer time of total cardiac arrest, prolonged burst pacing appears to be a safe and effective method for induction of ventricular fibrillation during cardioverter-defibrillator testing, which enables omission of analgesia and sedation or general anaesthesia.

Neurological biomarkers in the perioperative period

The rapid detection and evaluation of patients presenting with perioperative neurological dysfunction is of great clinical relevance. Biomarkers have been defined as biological molecules that can be used as an indicator of new onset or progression of a biological process or effect of treatment. Biomarkers have become increasingly important in this setting to supplement other modalities of diagnosis such as EEG, sensory- or motor-evoked potential, transcranial Doppler, near-infrared spectroscopy, or imaging methods. A number of neuro-proteins have been identified and are currently under investigation for potential to provide insights into injury severity, outcome, and the ability to monitor cellular damage and molecular events that occur during neurological injury. S100B is a protein released by glial cells and is considered a marker of blood-brain barrier dysfunction. Clinical studies in patients undergoing cardiac and non-cardiac surgery indicate that serum levels of S100B are increased intraoperatively and after operation. The neurone-specific enolase has also been extensively investigated as a potential marker of neuronal injury in the context of cardiac and non-cardiac surgery. A third biomarker of interest is the Tau protein, which has been linked to neurodegenerative disorders. Tau appears to be more specific than the previous two biomarkers since it is only found in the central nervous system. The metalloproteinase and ubiquitin C terminal hydroxylase-L1 (UCH-L1) are the most recently researched markers; however, their usefulness is still unclear. This review presents a comprehensive overview of S100B, neuronal-specific enolase, metalloproteinases, and UCH-L1 in the perioperative period.

[Implantation of cardioverter-defibrillators. How much anesthesia is necessary?]

Updated cardiologic guidelines constitute the background for an extended spectrum of indications for the implantation of automatic implantable cardioverter defibrillators (AICDs) and lead to an increasing number of operative implantations of AICDs. Moreover, during implantation of devices for cardiac resynchronization therapy the anesthesiologist is responsible for the most critically ill patients with the longest duration of surgery. As a result anesthesiologists face an increasing number of critically ill patients, whose management contributes to perioperative outcome. Automatic implantable cardioverter defibrillators can be implanted either during general anesthesia, local anesthesia or during a combination of local anesthesia combined with deep conscious sedation accomplished by an anesthesiologist. Besides economic aspects there is an increasing demand for anesthesia with the least cardiovascular side effects and rapid recovery in the often seriously ill patient with preexisting limitations of cardiac and pulmonary functions. Accordingly procedure and anesthesia-associated risks are reviewed and an algorithm for anesthesia management is suggested.

Cerebral desaturation during cardiac arrest: its relation to arrest duration and left ventricular pump function

OBJECTIVE

To determine the impact of brief periods of cardiac arrest (CA) on regional cerebral oxygen saturation (rSO2) in patients with low left ventricular ejection fraction (LVEF <30%).

DESIGN

Prospective observational study.

SETTING

Cardiac surgery room at a university hospital.

PATIENTS

Seventy-seven consecutive patients undergoing elective implantation of a cardioverter/defibrillator in monitored anesthesia care. According to preoperative assessments, left ventricular function was classified as normal (LVEF >50%), moderately impaired (LVEF 30%-50%), or severely reduced (LVEF <30%).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

rSO2 was determined during threshold testing with concomitant induction of CA. In patients with LVEF <30%, mean baseline rSO2 (59%) was already below the lower range of normal despite normal arterial blood pressure, heart rate, and arterial oxygen saturation. rSO2 increased by 6% after 6 L/min oxygen insufflation (p < 0.05) and dropped again in each group after CA, reaching a nadir after successful defibrillation. Patients with LVEF <30% and baseline rSO2 <63% exhibited the lowest values. They also showed the highest incidence (11%) of critical cerebral desaturations (i.e., >20% drop from baseline or rSO2 value <50%). rSO2 in patients with LVEF <30% was always below that determined in patients with LVEF >30% (p < 0.05). There was a strong correlation between rSO2 values before CA and rSO2 nadir (p < 0.05). The drop in rSO2 was only moderately related to the brief CAs (p < 0.05).

CONCLUSION

These findings demonstrate that severely compromised left ventricular pump function is associated with diminished rSO2. As these patients seem to be more susceptible to critical desaturations, they may be prone to severe tissue hypoxemia unless adequate oxygen delivery is reestablished rapidly. This may contribute to the poor neurologic outcome after successful resuscitation in patients with LVEF <30%.