An Update on Postoperative Cognitive Dysfunction Following Cardiac Surgery

Postoperative cognitive dysfunction is extremely prevalent following cardiac surgery. The increasing patient age and comorbidity profile increases their susceptibility to cognitive impairment. The underlying pathophysiological mechanisms leading to cognitive impairment are not clearly elucidated. Using the contemporary literature (2015-present), this narrative review has three aims. Firstly, to provide an overview of postoperative cognitive impairment. Secondly, to analyse the predominant pathophysiological mechanisms leading to cognitive dysfunction following cardiac surgery such as inflammation, cerebral hypoperfusion, cerebral microemboli, glycaemic control and anaesthesia induced neurotoxicity. Lastly, to assess the current therapeutic strategies of interest to address these pathophysiological mechanisms, including the administration of dexamethasone, the prevention of prolonged cerebral desaturations and the monitoring of cerebral perfusion using near-infrared spectroscopy, surgical management strategies to reduce the neurological effects of microemboli, intraoperative glycaemic control strategies, the effect of volatile vs. intravenous anaesthesia, and the efficacy of dexmedetomidine.

Changes in intraocular pressure during coronary artery bypass graft surgery: an observational study

Background

In this study, the effects of pulsatile and non-pulsatile on-pump Coronary Artery Bypass Graft surgery (CABG) and off-pump CABG techniques on the intraocular pressure were investigated.

Methods

Forty-five patients who planned to elective coronary artery bypass surgery with on-pump pulsatile (n = 15), non-pulsatile (n = 15), or off-pump (n = 15) were included. Intraocular Pressure (IOP) measurements were performed on both eyes at nine time-points: 1) Before the operation, 2) After anesthesia induction, 3) 3 minutes after heparin administration Left Internal Mammary Artery (LIMA) harvesting, 4) End of the first anastomosis, 5) End of LIMA anastomosis, 6) 3 minutes after protamine administration, 7) End of the operation, and 8) Second hour in Intensive Care Unit (ICU), 9) Fifth hour in ICU. Mean Arterial Pressure (MAP) and Central Venous Pressure (CVP) were also recorded at the same time points as IOP.

Results

In Cardiopulmonary Bypass (CPB) groups (pulsatile or non-pulsatile CPB) with the beginning of CPB, there were significant decreases in IOP values when compared to baseline (p = 0.012). This decrease was more prominent in the non-pulsatile group when compared to the pulsatile group (T₄ IOP values: pulsatile, 9.7 ± 2.6; non-pulsatile, 6.8 ± 1.9; p = 0.002; T₅ IOP values: pulsatile, 9.5 ± 1.9; non-pulsatile, 6.7 ± 2.1; p = 0.004). At the end of the surgery (T₇), IOP values returned to the baseline and stayed stable at the remaining time-points. In-off pump group, IOP values significantly increased with a head-down position (T₄ IOP values: off-pump surgery, 19.7 ± 5.2; p = 0.015). IOP values remained high until the normalization of head-down position (T₆) and stayed stable through the rest of all remaining time-points.

Conclusion

During cardiac surgery regardless of the technique (on-pump CABG, off-pump CABG), intraocular pressures remain in the normal ranges. It should be kept in mind that patients should be avoided from long and extreme Trendelenburg position, low CVP, and MAP levels during cardiac surgery to prevent eye-related complications.

N-acetylcysteine use among patients undergoing cardiac surgery: A systematic review and meta-analysis of randomized trials

Background

Cardiac surgeries are complex procedures aiming to re-establish coronary flow and correct valvular defects. Oxidative stress, caused by inflammation and ischemia-reperfusion injury, is associated with these procedures, increasing the risk of adverse outcomes. N-acetylcysteine (NAC) acts as an antioxidant by replenishing the glutathione stores, and emerging evidence suggests that NAC may reduce the risk of adverse perioperative outcomes. We conducted a systematic review and meta-analysis to investigate the addition of NAC to a standard of care among adult patients undergoing cardiac surgery.

Methods

We searched four databases (PubMed, EMBASE, CENTRAL, LILACS) from inception to October 2018 and the grey literaure for randomized controlled trials (RCTs) investigating the effect of NAC on pre-defined outcomes including mortality, acute renal insufficiency (ARI), acute cardiac insufficiency (ACI), hospital length of stay (HLoS), intensive care unit length of stay (ICULoS), arrhythmia and acute myocardial infarction (AMI). Reviewers independently screened potentially eligible articles, extracted data and assessed the risk of bias among eligible articles. We used the GRADE approach to rate the overall certainty of evidence for each outcome.

Results

Twenty-nine RCTs including 2,486 participants proved eligible. Low to moderate certainty evidence demonstrated that the addition of NAC resulted in a non-statistically significant reduction in mortality (Risk Ratio (RR) 0.71; 95% Confidence Interval (CI) 0.40 to 1.25), ARI (RR 0.92; 95% CI 0.79 to 1.09), ACI (RR 0.77; 95% CI 0.44 to 1.38), HLoS (Mean Difference (MD) 0.21; 95% CI -0.64 to 0.23), ICULoS (MD -0.04; 95% CI -0.29 to 0.20), arrhythmia (RR 0.79; 95% CI 0.52 to 1.20), and AMI (RR 0.84; 95% CI 0.48 to 1.48).

Limitations

Among eligible trials, we observed heterogeneity in the population and interventions including patients with and without kidney dysfunction and interventions that differed in route of administration, dosage, and duration of treatment. This observed heterogeneity was not explained by our subgroup analyses.

Conclusions

The addition of NAC during cardiac surgery did not result in a statistically significant reduction in clinical outcomes. A large randomized placebo-controlled multi-centre trial is needed to determine whether NAC reduces mortality.

Registration

PROSPERO CRD42018091191.

Differences of early immunological responses in on-pump versus off-pump cardiac surgery

INTRODUCTION

Cardiopulmonary bypass surgery is accompanied by an inflammatory response and pulmonary dysfunction that renders patients vulnerable to postoperative complications. The majority of studies investigating the inflammatory response in cardiopulmonary bypass focus on cytokine measurements. This study investigated the early response of peripheral blood cell types and early changes in lung tissue in on-pump versus off-pump cardiopulmonary bypass surgery.

METHODS

Landrace pigs were assigned to the following groups (n = 6 per group): 1. off-pump cardiopulmonary bypass, 2. conventional cardiopulmonary bypass, 3. heparin-coated cardiopulmonary bypass, 4. surface-reduced cardiopulmonary bypass, and 5. surface-reduced cardiopulmonary bypass plus lung perfusion. Surgery was performed under mild hyperthermia (32°C), with 90-minute ischemia and 180-minute reperfusion. Histological and flow cytometric analyses were performed.

RESULTS

Lung water content increased during reperfusion in heparin-coated (84.63 ± 2.99%) compared to conventional cardiopulmonary bypass (76.33 ± 4.56%, p = 0.04). Alveolar septal thickness increased during ischemia at heparin-coated (p < 0.01) and surface-reduced cardiopulmonary bypass plus lung perfusion (p = 0.05). Tumor necrosis factor expression increased significantly (p < 0.01) in peribronchial, perivascular, and peripheral lung areas in all on-pump groups, but not in off-pump cardiopulmonary bypass. The usage of heparin-coated cardiopulmonary bypass led to increased percentages of CD3⁺CD4⁺ (p = 0.03) and CD3⁺CD8⁺ (p = 0.01) T cells compared to an uncoated device. Natural killer and mature B lymphocytes decreased at conventional and surface-reduced cardiopulmonary bypass plus lung perfusion. Activated granulocytes and macrophages increased at conventional cardiopulmonary bypass and heparin-coated cardiopulmonary bypass.

CONCLUSION

Off-pump cardiopulmonary bypass induces less immunological response and lung injury than on-pump surgery. The reduction of cardiopulmonary bypass surface reduces the inflammatory immune response induced by cardiopulmonary bypass. Lung perfusion of surface-reduced cardiopulmonary bypass diminished the extravasation caused by surface reduction of the cardiopulmonary bypass.

Effects of Glucose Variability on Short-Term Outcomes in Non-Diabetic Patients After Coronary Artery Bypass Grafting: A Retrospective Observational Study

BACKGROUND

Postoperative hyperglycaemia has been shown to have adverse effects on patients after coronary artery bypass grafting surgery (CABG). However, whether glucose variability has an effect on patients' outcomes is still uncertain. The aim of this study is to explore the effects of glucose variability on short-term outcomes in non-diabetic patients undergoing coronary artery bypass grafting.

METHODS

This is a retrospective observational study utilising data collected after patients had left the hospital. This study was performed on 137 non-diabetic patients undergoing coronary artery bypass grafting from January 2011 to June 2013. Blood glucose at 72hours post operation was obtained and glucose variability was measured by mean postoperative blood glucose and mean of daily difference (MODD). Short-term outcomes included duration of intensive care unit (ICU) stay, mechanical ventilation time, length of hospital stay, and occurrence of arrhythmia. Patients with mean postoperative blood glucose ≥7.00mmol/L were defined as hyperglycaemic, and patients with MODD ≥1.40mmol/L were considered to be abnormal. Outcome variables were compared between patients in euglycaemic and hyperglycaemic groups, and between patients in normal and abnormal groups.

RESULTS

In our study, patients with hyperglycaemia spent more time staying in ICU (p<0.01), and patients with large glucose variability (abnormal MODD) had higher incidences of arrhythmia (23% vs 4.2%, p<0.05). Regression analysis showed that MODD can affect occurrence of arrhythmia (p=0.004) and that mean postoperative blood glucose levels can affect duration of ICU stay (p<0.001).

CONCLUSIONS

Patients' postoperative glucose variability after CABG is an important predictor of the negative outcomes regarding duration of ICU stay and occurrence of arrhythmia. Large glucose variability can have negative effects on short-term outcomes in patients.

Effect of the type of cardiopulmonary bypass pump flow on postoperative cognitive function in patients undergoing isolated coronary artery surgery

OBJECTIVE

Pulsatile flow, generated by a pump during cardiopulmonary bypass, has been accepted as more physiological in coronary artery bypass grafting surgery (CABG). Therefore, we aimed to investigate the effects of pulsatile and nonpulsatile flow on postoperative cognitive function and to review relationship with the biomarkers S100ß and neuron-specific enolase (NSE).

METHODS

Patients who underwent isolated CABG were included this prospective, randomized, double-blind study, which was performed between March 2010 and December 2010. Patients were divided into two groups: pulsatile (Group I, n=20) and nonpulsatile (Group II, n=20) flow. Blood samples were collected 1 day before surgery and in the sixth postoperative hour for the analysis of S100ß and NSE. In addition, Mini-Mental State Examination (MMSE) was performed during preoperative period and on third postoperative day. Outcomes were determination of effects of pump flow type on cognitive function and relationships with concentrations of S100ß and NSE.

RESULTS

Forty patients were included. No differences were observed between the groups with respect to complications, mortality, S100ß (Group I: 1.9±0.2 µ/L; Group II: 2.0±0.2 µ/L), NSE (Group I: 12.5±0.8 µ/L; Group II: 12.4±0.7 µ/L), MMSE scores [Group I: 25 (23-27); Group II: 25 (23-27)], and postoperative cognitive dysfunction (POCD) (p>0.05). No correlation was observed between MMSE scores and concentrations of S100ß (r=-0.032) and NSE (r=-0.423) (p>0.05).

CONCLUSION

There was no difference between types of pump flow for POCD and no relationship between cognitive dysfunction and S100ß and NSE concentrations. Pump flow type does not affect NSE concentrations.

Plasma cytokine levels in dogs undergoing cardiopulmonary bypass

Currently, there are no reports of inflammatory responses to CPB in dogs. We investigated the time course of pro- and anti-inflammatory cytokine levels during and after CPB.

ANIMALS

The study group included 11 dogs that underwent mitral valve repair with CPB, and the control group included 7 healthy dogs that underwent ovariohysterectomy.

METHODS

Blood samples from the study group dogs were collected before, during and after surgery and analyzed for plasma levels of interleukin-6 (IL-6), tissue necrosis factor-α (TNF-α), interleukin-10 (IL-10), white blood cells (WBC), and C-reactive protein (CRP). Each inflammatory parameter was also compared with that of the control group dogs.

RESULTS

After CPB, plasma levels of IL-6, WBC counts, and CRP levels were significantly higher than preoperative levels, and IL-6 levels in the study group were significantly higher than those in the control group.

CONCLUSIONS

CPB induces a systemic inflammatory response in dogs.