Neurological dysfunction after cardiac surgery and cardiac intensive care admission: A narrative review part 1: The problem; nomenclature; delirium and postoperative neurocognitive disorder; and the role of cardiac surgery and anesthesia

Effects of Midazolam and Dexmedetomidine on Cognitive Dysfunction Following Open-Heart Surgery: A Comprehensive Review

PURPOSE

Patients undergoing open-heart surgery often face significant challenges in postoperative cognitive dysfunction (POCD). There has been growing interest in understanding how anesthesia medications, such as dexmedetomidine (DEX) and midazolam, impact cognitive function in these patients.

METHOD

This comprehensive review aims to detail the effect of DEX and midazolam on cognitive outcomes following open-heart surgery.

FINDINGS

Midazolam, a highly selective and commonly used benzodiazepine for preoperative anxiolytics and sedation has been associated with POCD. However, evidence regarding its impact on cognitive function is vague; some studies suggest a potential link between midazolam administration and cognitive impairment, while others report no effect or even an improvement in cognitive abilities. DEX is a potential neuroprotective agent in cardiac surgery. The effects of DEX on cognitive function, including a reduction in POCD incidence and severity, have been reported in several studies. It modulates the inflammatory responses, attenuates oxidative stress, and preserves cerebral perfusion. Although DEX and midazolam show promising results, their effects on cognitive function following open-heart surgery are yet to be elucidated.

CONCLUSION

Various factors, including patient characteristics, perioperative management, and surgical procedures, may influence these outcomes, highlighting the need for further research to better understand the roles of these agents in cognitive function following open-heart surgery.

Jugular Venous Oxygen and Lactate Parameters for Predicting Early Cognitive Dysfunction after Off-Pump Coronary Artery Bypass Grafting: A Prospective Observational Study

BACKGROUND AND OBJECTIVES

The quality of life may be negatively impacted by postoperative cognitive dysfunction (POCD) following off-pump coronary artery bypass grafting (OPCAB). It is still unclear how useful the jugular venous lactate and oxygen parameters are in predicting POCD following OPCAB.

METHODS

This prospective observational study was conducted over a period of 15 months and included 54 individuals. It sought to determine the sensitivity and specificity of jugular venous lactate and oxygen parameters for early POCD prediction in patients undergoing OPCAB. Neuropsychological tests were conducted to assess baseline cognitive function. Under ultrasound guidance, the jugular bulb was cannulated. The jugular venous lactate and oxygen parameters were measured at the time of surgery, following each graft, and 6 and 24 h later. Confusion assessment method-intensive care unit score was assessed on the third postoperative day for postoperative delirium (POD). POCD was defined as a composite Z score ≥1.96 or two Z scores in individual tests at 1 week. The jugular venous lactate and oxygen parameters of the Decline (D) group were compared to those of the Normal (N) group. Receiver operating characteristic curves were used to assess the diagnostic efficacy of derived variables.

RESULTS

The incidence of POD and POCD was 18.5% and 11.1%, respectively. At T3, all derived variables showed a significant increase, although the arterio-jugular venous lactate difference (AJDL) and modified lactate oxygen index (mLOI) were substantially greater at T3 in group D compared to group N. When predicting POCD, mLOI demonstrated the highest sensitivity at 72.22%, while AJDL showed the highest specificity at 90.7%.

CONCLUSIONS

For prediction of early POCD in patients undergoing elective OPCAB, mLOI had highest sensitivity, while AJDL had high specificity.

Altered Microvascular Reactivity During a Skin Thermal Challenge Is Associated With Organ Dysfunction and Slow Recovery After Cardiac Surgery

OBJECTIVES

To assess microvascular reactivity during a skin thermal challenge early post-cardiac surgery and its association with outcomes.

DESIGN

Noninvasive physiological study.

SETTING

Thirty-five-bed department of intensive care.

PARTICIPANTS

Patients admitted to the intensive care unit post-cardiac surgery.

INTERVENTIONS

Thermal challenge.

MEASUREMENTS AND MAIN RESULTS

A total of 46 patients were included; 14 needed vasoactive or ventilatory support for at least 48 hours (slow recovery), and 32 had a more rapid recovery. Skin blood flow (SBF) was measured on the anterior proximal forearm using skin laser Doppler. A thermal challenge was performed by abruptly increasing local skin temperature from 37°C to 43°C while monitoring SBF. The ratio between SBFs at 43°C and 37°C was calculated to measure microvascular reactivity. SBF at 37°C was not significantly different in patients with a slow recovery and those with a rapid recovery, but SBF after 9 minutes at 43°C was lower (48.5 [17.3-69.0] v 85.1 [45.2-125.7], p < 0.01), resulting in a lower SBF ratio (2.8 [1.5-4.7] v 4.8 [3.7-7.8], p < 0.01). Patients with lower SBF ratios were more likely to have dysfunction of at least one organ (assessed using the sequential organ dysfunction score) 48 hours post-cardiac surgery than those with higher ratios: 88% versus 40% versus 27% (p < 0.01), respectively, for the lowest, middle, and highest tertiles of SBF ratio. In multivariable analysis, a lower SBF ratio was an independent risk factor for slow recovery.

CONCLUSIONS

Early alterations in microvascular reactivity, evaluated by a skin thermal challenge, are correlated with organ dysfunction. These observations may help in the development of new, simple, noninvasive monitoring systems in postoperative patients.

Clinical investigation into risk factors for delirium post-cardiac surgery and its implications for nursing intervention guided by behavior change theory

BACKGROUND

This study explores the factors contributing to the occurrence of delirium following cardiac surgery and devises nursing strategies rooted in behavior change theory.

METHODS

A cohort of 320 cardiac surgery patients was selected, categorized into two groups: 93 cases where postoperative delirium (POD) was anticipated, and 227 cases where it was not. Preoperative, intraoperative, and postoperative factors of POD were scrutinized using single-factor analysis, while binary logistic regression analysis was employed to pinpoint risk factors.

RESULTS

Among the 320 patients, 93 displayed POD symptoms post-surgery, yielding an incidence of 29.06%. Preoperative univariate analysis disclosed significant differences in gender, age, smoking, hypertension, and diabetes (P < 0.05). Intraoperatively, significant differences were noted in the American Society of Anesthesiologists (ASA) anesthesia grade (II, III, and IV), surgery time, cardiopulmonary bypass duration, and aortic occlusion duration (P < 0.05). Post-surgery, significant differences were observed in the duration of Intensive Care Unit (ICU) stay, mechanical ventilation time, and visual analogue scale (VAS) scores (P < 0.05). Multivariate Logistic regression identified surgery time (OR = 2.334, P < 0.001), ICU admission duration (OR = 1.457, P < 0.001), mechanical ventilation time (OR = 1.235, P = 0.004), and VAS scores (OR = 2.986, P < 0.001) as independent risk factors for POD. ROC curve analysis indicated higher sensitivity and specificity in predicting POD with surgery time, ICU stay duration, mechanical ventilation time, and VAS scores.

CONCLUSION

Irrespective of the surgical intervention type, surgery time, ICU stay duration, mechanical ventilation time, and VAS scores are recognized as risk factors for POD in cardiac surgery patients. Hence, continuous patient monitoring and early intervention tailored to specific risk factors are essential in clinical practice to mitigate POD incidence.

Comparison of Propofol-Based Total Intravenous Anesthesia versus Volatile Anesthesia with Sevoflurane for Postoperative Delirium in Adult Coronary Artery Bypass Grafting Surgery: A Prospective Randomized Single-Blinded Study

OBJECTIVES

To compare the incidence of delirium and early (at 1 week) postoperative cognitive dysfunction (POCD) between propofol-based total intravenous anesthesia (TIVA) and volatile anesthesia with sevoflurane in adult patients undergoing elective coronary artery bypass graft surgery (CABG) with cardiopulmonary bypass (CPB).

DESIGN

This was a prospective randomized single-blinded study.

SETTING

The study was conducted at a single institution, the Sree Chitra Tirunal Institute for Medical Sciences and Technology, a tertiary care institution and university-level teaching hospital.

PARTICIPANTS

Seventy-two patients undergoing elective CABG under CPB participated in this study.

INTERVENTIONS

This study was conducted on 72 adult patients (>18 years) undergoing elective CABG under CPB who were randomized to receive propofol or sevoflurane. Anesthetic depth was monitored to maintain the bispectral index between 40 and 60. Delirium was assessed using the Confusion Assessment Method for the Intensive Care Unit. Early POCD was diagnosed when there was a reduction of >2 points in the Montreal Cognitive Assessment score compared to baseline. Cerebral oximetry changes using near-infrared spectroscopy (NIRS), atheroma grades, and intraoperative variables were compared between the 2 groups.

MEASUREMENTS & MAIN RESULTS

Seventy-two patients were randomized to receive propofol (n = 36) or sevoflurane (n = 36). The mean patient age was 59.4 ± 8.6 years. The baseline and intraoperative variables, including atheroma grades, NIRS values, hemoglobin, glycemic control, and oxygenation, were comparable in the 2 groups. Fifteen patients (21.7%) patients developed delirium, and 31 patients (44.9%) had early POCD. The incidence of delirium was higher with sevoflurane (n = 12; 34.2%) compared to propofol (n = 3; 8.8%) (odds ratio [OR], 1.72; 95% confidence interval [CI], 1.13-2.62; p = 0.027)*. POCD was higher with sevoflurane (n = 20; 57.1%) compared to propofol (n = 11; 32.3%) (OR, 1.63; 95% CI, 1.01-2.62; p = 0.038)*. In patients aged >65 years, delirium was higher with sevoflurane (7/11; 63.6%) compared to propofol (1/7; 14.2%) (p = 0.03)*.

CONCLUSIONS

Propofol-based TIVA was associated with a lower incidence of delirium and POCD compared to sevoflurane in this cohort of patients undergoing CABG under CPB. Large-scale, multicenter randomized trials with longer follow-up are needed to substantiate the clinical relevance of this observation.

Electroencephalography Monitoring for Preventing Postoperative Delirium and Postoperative Cognitive Decline in Patients Undergoing Cardiothoracic Surgery: A Meta-Analysis

Background

Patients undergoing cardiothoracic surgery frequently encounter perioperative neurocognitive disorders (PND), which can include postoperative delirium (POD) and postoperative cognitive decline (POCD). Currently, there is not enough evidence to support the use of electroencephalograms (EEGs) in preventing POD and POCD among cardiothoracic surgery patients. This meta-analysis examined the importance of EEG monitoring in POD and POCD.

Methods

Cochrane Library, PubMed, and EMBASE databases were searched to obtain the relevant literature. This analysis identified trials based on the inclusion and exclusion criteria. The Cochrane tool was used to evaluate the methodological quality of the included studies. Review Manager software (version 5.3) was applied to analyze the data.

Results

Four randomized controlled trials (RCTs) were included in this meta-analysis, with 1096 participants. Our results found no correlation between EEG monitoring and lower POD risk (relative risk (RR): 0.81; 95% CI: 0.55-1.18; p = 0.270). There was also no statistically significant difference between the EEG group and the control group in the red cell transfusions (RR: 0.86; 95% CI: 0.51-1.46; p = 0.590), intensive care unit (ICU) stay (mean deviation (MD): -0.46; 95% CI: -1.53-0.62; p = 0.410), hospital stay (MD: -0.27; 95% CI: -2.00-1.47; p = 0.760), and mortality (RR: 0.33; 95% CI: 0.03-3.59; p = 0.360). Only one trial reported an incidence of POCD, meaning we did not conduct data analysis on POCD risk.

Conclusions

This meta-analysis did not find evidence supporting EEG monitoring as a potential method to reduce POD incidence in cardiothoracic surgery patients. In the future, more high-quality RCTs with larger sample sizes are needed to validate the relationship between EEG monitoring and POD/POCD further.

Delirium after Cardiac Surgery-A Narrative Review

Postoperative delirium (POD) after cardiac surgery is a well-known phenomenon which carries a higher risk of morbidity and mortality. Multiple patient-specific risk factors and pathophysiologic mechanisms have been identified and therapies have been proposed to mitigate risk of delirium development postoperatively. Notably, cardiac surgery frequently involves the use of an intraoperative cardiopulmonary bypass (CPB), which may contribute to the mechanisms responsible for POD. Despite our greater understanding of these causative factors, a substantial reduction in the incidence of POD remains high among cardiac surgical patients. Multiple therapeutic interventions have been implemented intraoperatively and postoperatively, many with conflicting results. This review article will highlight the incidence and impact of POD in cardiac surgical patients. It will describe some of the primary risk factors associated with POD, as well as anesthetic management and therapies postoperatively that may help to reduce delirium.

Association Between Risk of Stroke and Delirium After Cardiac Surgery and a New Electroencephalogram Index of Interhemispheric Similarity

OBJECTIVES

Neurologic complications after surgery (stroke, delirium) remain a major concern despite advancements in surgical and anesthetic techniques. The authors aimed to evaluate whether a novel index of interhemispheric similarity, the lateral interconnection ratio (LIR), between 2 prefrontal electroencephalogram (EEG) channels could be associated with stroke and delirium following cardiac surgery.

DESIGN

Retrospective observational study.

SETTING

Single university hospital.

PARTICIPANTS

A total of 803 adult patients without documentation of a previous stroke, who underwent cardiac surgery with cardiopulmonary bypass (CPB) between July 2016 and January 2018.

INTERVENTIONS

The LIR index was calculated retrospectively from the patients' EEG database.

MEASUREMENTS AND MAIN RESULTS

LIR was analyzed intraoperatively every 10 seconds and compared among patients with postoperative stroke, patients with delirium, and patients without documented neurologic complications, during 5 key periods, each lasting10 minutes: (1) surgery start, (2) before CPB, (3) on CPB, (4) after CPB, and (5) surgery end. After cardiac surgery, 31 patients suffered from stroke; 48 patients were diagnosed with delirium; and 724 had no documented neurologic complications. Patients with stroke demonstrated a decrease in LIR index between the start of surgery and the postbypass period of 0.08 (0.01, 0.36 [21]; median and [interquartile range {IQR}]; valid EEG samples); whereas there was no similar decrease in the no-dysfunction group (-0.04 [-0.13, 0.04; {551}], p < 0.0001). Patients with delirium showed a decrease in LIR index between the start of surgery and the end of the surgery by 0.15 (0.02, 0.30 [12]), compared with no such decrease in the no-dysfunction group (-0.02 [-0.12, 0.08 {376}], p ≈ 0.001).

CONCLUSIONS

After improvement of SNR, it might be of value to further study the index decrease as an indication for risk for brain injury after surgery. The timing of decrease (after CPB or end of surgery) may provide hints regarding the injury pathophysiology and its onset.

NLRP3 inflammasome activation contributes to the cognitive decline after cardiac surgery

BACKGROUND

Perioperative neurocognitive disorders (PND) are a common complication of cardiac surgery in elderly patients. The etiopathogenesis of PND is not clear. Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, a macromolecular protein complex, regulates inflammation by inducing the release of proinflammatory cytokines interleukin (IL)-1β and IL-18. Studies have demonstrated a close link between the NLRP3 inflammasome and central nervous system diseases. Nevertheless, the involvement of NLRP3 inflammasome in the causation of PND occurring after cardiac surgery is unclear. This study aimed to investigate the association of serum NLRP3 level with PND.

METHODS

We performed a retrospective study, enrolled 75 patients undergoing elective cardiac surgery and evaluated their cognitive functions one day before and 7 days after surgery. PND were determined according to the International Study of Postoperative Cognitive Dysfunction studies. Demographics and perioperative parameters were recorded. Perioperative serum NLRP3 protein, IL-1β, and IL-18 levels were monitored.

RESULTS

The PND incidence in our cohort was 33.33%. NLRP3 protein levels were significantly increased in all patients at each postoperative time-point after general anesthesia and cardiac surgery under cardiopulmonary bypass. Patients showing cognitive dysfunction had higher serum NLRP3 protein, caspase-1, IL-1β, and IL-18 levels immediately after the operation. Variables associated with the incidence of early PND were included in the regression models. After adjusting for confounding variables, high serum NLRP3 protein level at the end of the operation and old age were identified as independent predictors of PND.

CONCLUSIONS

High serum NLRP3 protein level at the completion of cardiac surgery was associated with a higher risk of PND seven days after surgery.

TRIAL REGISTRATION

The study was registered at Clinicaltrials.gov (registration number: NCT04191642).

Influences of remote ischemic preconditioning on postoperative delirium and cognitive dysfunction in adults after cardiac surgery: a meta-analysis of randomized controlled trials

Background

Remote ischemic preconditioning (RIPC) has been suggested to confer neuroprotective effect. However, influences of RIPC on postoperative delirium (POD) and cognitive dysfunction (POCD) in adults after cardiac surgery are less known. We performed a meta-analysis of randomized controlled trials (RCTs) to evaluate the effects of RIPC on POD and POCD.

Methods

Relevant studies were obtained by search of PubMed, Embase, and Cochrane’s Library databases. A random-effect model was used to pool the results.

Results

Ten RCTs including 2303 adults who received cardiac surgery were included. Pooled results showed that RIPC did not significantly affect the incidence of POD (six RCTs, odds ratio [OR] 1.07, 95% confidence interval [CI] 0.81 to 1.40, P = 0.65) with no significant heterogeneity (I² = 0%). In addition, combined results showed that RIPC did not significantly reduce the incidence of POCD either (six RCTs, OR 0.64, 95% CI 0.37 to 1.11, P = 0.11) with moderate heterogeneity (I² = 44%). Sensitivity analysis by excluding one RCT at a time showed consistent results (P values all > 0.05).

Conclusions

Current evidence from RCTs did not support that RIPC could prevent the incidence of POD or POCD in adults after cardiac surgery. Although these findings may be validated in large-scale RCTs, particularly for the results of POCD, based on these findings, RIPC should not be routinely used as a preventative measure for POD and POCD in adult patients after cardiac surgery.

Is Perioperative Dexmedetomidine Associated With a Reduced Risk of Perioperative Neurocognitive Disorders Following Cardiac Surgery? A Systematic Review and Meta-Analysis With Trial Sequential Analysis of Randomized Controlled Trials

Background: To assess the effect of dexmedetomidine on the reducing risk of perioperative neurocognitive disorders (PNDs) following cardiac surgery.

Methods: A systematic review and meta-analysis with trial sequential analysis (TSA) of randomized controlled trials were performed. PubMed, Embase, Cochrane Library, and CNKI databases (to August 16, 2020) were searched for relevant articles to analyze the incidence of PND for intraoperative or postoperative dexmedetomidine administration after cardiac surgery. PND included postoperative cognitive dysfunction (POCD) and postoperative delirium (POD).

Results: A total of 24 studies with 3,610 patients were included. Compared with the control group, the incidence of POD in the dexmedetomidine group was significantly lower (odds ratio [OR]: 0.59, 95% CI: 0.43–0.82, P = 0.001), with firm evidence from TSA. Subgroup analyses confirmed that dexmedetomidine reduced the incidence of POD with firm evidence following coronary artery bypass grafting surgery (OR: 0.45, 95% CI: 0.26–0.79, P = 0.005), and intervention during the postoperative period (OR: 0.48, 95% CI: 0.34–0.67, P < 0.001). Furthermore, the incidence of POD in the dexmedetomidine group was also decreased in mixed cardiac surgery (OR: 0.68, 95% CI: 0.47–0.98, P = 0.039). Irrespective of whether “Confusion Assessment Method/Confusion Assessment Method for intensive care unit” or “other tools” were used as diagnostic tools, the results showed a decreased risk of POD in the dexmedetomidine group. There was no significant difference in the incidence of POCD (OR: 0.47, 95% CI: 0.22–1.03, P = 0.060) between the two groups, but this result lacked firm evidence from TSA.

Conclusion: The administration of dexmedetomidine during the perioperative period reduced the incidence of POD in patients after cardiac surgery, but there was no significant benefit in the incidence of POCD. The effect of dexmedetomidine on the incidence of POD or POCD following different types of surgery and the optimal dose and timing of dexmedetomidine warrant further investigation.

Trial registration: PROSPERO registration number: CRD42020203980. Registered on September 13, 2020.

Validation of E-PRE-DELIRIC in cardiac surgical ICU delirium: A retrospective cohort study

BACKGROUND

The early prediction model for delirium in intensive care units (ICUs)-E-PRE-DELIRIC-has been created to predict delirium development during the length of stay in ICUs. However, there have been few early predictive models for delirium in the cardiac surgical ICU (CSICU), and the predictive ability of the E-PRE-DELIRIC among patients following cardiac surgeries is still unknown.

AIMS AND OBJECTIVES

To validate the performance of E-PRE-DELIRIC in CSICU.

DESIGN

A retrospective cohort study.

METHODS

Data were retrospectively extracted from the electronic records for patients admitted in CSICU from January 2018 to December 2018 in a tertiary teaching hospital in China. Adult patients were included following the criteria of the E-PRE-DELIRIC model. Predictors, including age, history of cognitive impairment, history of alcohol abuse, urgent admission, use of corticosteroids, respiratory failure, blood urea nitrogen, and mean arterial pressure, at the time of ICU admission were retrieved, and delirium was assessed twice a day using the Confusion Assessment Method for the ICU. The performance of the E-PRE-DELIRIC model was evaluated by area under receiver operator characteristic curve, precision-recall curve (AUPRC), Hosmer-Lemeshow (HL) test, and calibration belt.

RESULTS

Of the 725 patients included, 120 (16.6%) developed delirium. The AUROC was 0.54 (95% confidence interval [CI], 0.48-0.59), and the AUPRC was 0.18 (95% CI, 0.12-0.20). The HL test showed a significant difference between predicted probability and delirium occurrence (χ² = 17.326, P = .027), and the overestimation chance of the E-PRE-DELIRIC score was 0.24 to 0.43.

CONCLUSION

The E-PRE-DELIRIC model has poor-to-fair predictive value in this study; thus, its application among the CSICU patients is limited. Development of reliable and validated tools for early prediction of delirium in CSICU is required.

RELEVANCE TO CLINICAL PRACTICE

Early prediction of delirium risk at CSICU admission is of vital importance and could provide timely information to caregivers. However, the E-PRE-DELIRIC model should be applied cautiously in the CSICU because of the significant probability of over-estimating the risk of developing delirium.

The relationship between aortic calcification on chest radiograph and neurocognitive impairment after coronary artery bypass grafting

Background

In this study, we aimed to investigate the possible relationship between aortic calcification as detected by preoperative chest radiography and postoperative neurocognitive impairment in patients undergoing coronary artery bypass grafting.

Methods

A total of 124 patients (101 males, 23 females; mean age: 59.9±8.8 years; range, 34 to 84 years) who underwent coronary artery bypass grafting in our clinic between January 2019 and July 2019 were included. Of these patients, 35 whose preoperative chest radiography revealed aortic calcification in the aortic knuckle were included as the patient group. The control group consisted of 89 patients without aortic calcification. The patients with aortic calcification underwent additional imaging with thoracic computed tomography angiography and ascending aorta and aortic arch calcium scores were calculated. Neurocognitive dysfunction was assessed using the Standardized Mini-Mental State Examination. Postoperative delirium was evaluated by confusion assessment method in the intensive care unit. Both groups were compared for demographic, operative and postoperative data.

Results

Of all patients included in the study, the overall cerebrovascular event incidence was 3.2%. Although not statistically significant, the number of patients with neurocognitive decline was higher in the patient group than the control group (48.6% vs. 34.8%, respectively; p=0.157). Both Standardized Mini-Mental State Examination score decline and percentage decline were significantly higher in the patients with high aortic arch calcium scores (>2,250 AU). Carotid artery stenosis was 3.2 times higher in the patient group. In the patients with carotid artery stenosis, the aortic arch calcium scores were also higher (p=0.042).

Conclusion

Aortic calcification detectable on chest radiography with high calcium scores may be associated with neurocognitive impairment and carotid artery stenosis in patients undergoing coronary artery bypass grafting.