Karl Gunnar Engström

Postoperative atrial fibrillation is associated with late mortality after coronary surgery, but not after valvular surgery

BACKGROUND Numerous studies have attempted to determine the etiology and prophylactic measures concerning atrial fibrillation (AF) after cardiac surgery. However, limited data are available analyzing the association between postoperative AF and late mortality. We sought to determine if AF after cardiac surgery affects postoperative survival. METHODS All cardiac surgery patients (n = 9,495) undergoing cardiac surgery between January 1994 and December 2004 were studied. The study population comprised coronary artery bypass graft surgery (CABG [n = 7,621]), valvular surgeries (n = 995), and their combination (n = 879). Patients affected by postoperative AF were identified, and long-term survival was obtained from Swedish population registry and evaluated using Cox proportional hazards methods to adjust for baseline differences. RESULTS The overall AF incidence was 26.7%, subdivided into 22.9%, 39.8%, and 45.2% for CABG, valve surgery, and combined procedures, respectively. The median follow-up for the entire study population was 7.9 years (maximum, 13.4). Postoperative AF independently affected long-term survival in CABG patients (hazard ratio 1.22; 95% confidence interval: 1.08 to 1.37). For isolated valvular surgery or combined procedures, AF was not significantly associated with long-term survival (hazard ratio 1.21, 95% confidence interval: 0.92 to 1.58; and hazard ratio 1.15, 95% confidence interval: 0.90 to 1.46, respectively). CONCLUSIONS Postoperative AF increases late mortality after isolated CABG surgery only. This finding was not statistically confirmed after isolated or combined valvular procedures. Our results draw the attention to possible AF recurrence after hospital discharge, indicating a strict postoperative surveillance.

Delirium after Coronary Bypass Surgery Evaluated by the Organic Brain Syndrome Protocol

Objective : The aim was to evaluate symptoms of delirium from a psychogeriatric perspective occurring postoperative to coronary bypass surgery. Design : Patients, S 60 years, scheduled for coronary bypass surgery ( n = 52) were enrolled in a prospective descriptive study. The patients were evaluated before and several times after surgery by the Organic Brain Syndrome scale, and delirium was diagnosed according to psychiatric codes. Results : Of the 52 patients, 23% presented delirium. These patients were older than the control group, 73.5 - 4.2 and 69.3 - 5.9 years, respectively (mean - SD, p < 0.01), and had more frequently a history of previous stroke ( p < 0.05). Emotional delirium was seen in 83%, hyperactive delirium in about 40%, and 25% were classified to have a psychotic delirium. A major finding was a 58% frequency of hallucinations and illusions among patients with delirium, and a similar rate among those without delirium. Conclusion : Delirium is common after cardiac surgery in particular in older patients, but is often under-diagnosed. Hallucinations were common in both delirious and non-delirious patients.

The inflammatory response to recycled pericardial suction blood and the influence of cell-saving

Objective--To investigate the inflammatory and cellular response attributed to conventional cardiotomy suction vs cell-saver during cardiac surgery. Design--Thirty-three (n = 33) low-risk patients admitted for routine coronary artery bypass grafting were randomly assigned to two groups: cardiotomy suction or cell-saver for salvage of pericardial blood. The groups were compared with reference to proinflammatory cytokines, complement activation, leukocyte pattern, and haemolysis during and after cardiopulmonary bypass. Results--Pericardial suction blood contained significantly increased concentrations of free plasma haemoglobin, C3a, IL-6, IL-8, TNF-α, eosinophils and basophils compared with the systemic circulation. No differences were found for the terminal complement complex and lymphocytes, whereas overall concentrations of leukocytes, platelets and haemoglobin were decreased. Recycling of pericardial suction blood gave no systemic effects except from that of free plasma haemoglobin, which increased significantly. The cell-saver eliminated plasma haemoglobin, but no other effects could be demonstrated. Conclusion--Cardiotomy suction is a major cause of haemolysis, but contributes insignificantly to the systemic inflammatory response. Treatment of shed mediastinal blood with a cell-saver reduces haemolysis and may lower the dose load of inflammatory components.

Delirium after cardiac surgery: incidence and risk factors †

OBJECTIVES Delirium after cardiac surgery is a problem with consequences for patients and healthcare. Preventive strategies from known risk factors may reduce the incidence and severity of delirium. The present aim was to explore risk factors behind delirium in older patients undergoing cardiac surgery with cardiopulmonary bypass. METHODS Patients (≥70 years) scheduled for routine cardiac surgery were included (n = 142). The patients were assessed and monitored pre-/postoperatively, and delirium was diagnosed from repeated assessments with the Mini-Mental State Examination and the Organic Brain Syndrome Scale, using the DSM-IV-TR criteria. Variables were analysed by uni-/multivariable logistic regression, including both preoperative variables (predisposing) and those extracted during surgery and in the early postoperative period (precipitating). RESULTS Delirium was diagnosed in 78 patients (54.9%). Delirium was independently associated with both predisposing and precipitating factors (P-value, odds ratio, upper/lower confidence interval): age (0.036, 1.1, 1.0/1.2), diabetes (0.032, 3.5, 1.1/11.0), gastritis/ulcer problems (0.050, 4.0, 1.0/16.1), volume load during operation (0.001, 2.8, 1.5/5.1), ventilator time in ICU (0.042, 1.2, 1.0/1.4), highest temperature recorded in ICU (0.044, 2.2, 1.0/4.8) and sodium concentration in ICU (0.038, 1.2, 1.0/1.4). CONCLUSIONS Delirium was common among older patients undergoing cardiac surgery. Both predisposing and precipitating factors contributed to delirium. When combined, the predictive strength of the model improved. Preventive strategies may be considered, in particular among the precipitating factors. Of interest, delirium was strongly associated with an increased volume load during surgery.

Early and delayed stroke after coronary surgery — an analysis of risk factors and the impact on short- and long-term survival

OBJECTIVE Stroke is a serious complication to cardiac surgery, and is generally considered as a uniform disease regardless of its temporal relationship to surgery. Our hypothesis suggests that stroke, in association with surgery, reflects other characteristics than stroke occurring with a free interval. This issue was here explored for risk factors and survival effects. METHODS Data were collected from 7839 procedures of isolated coronary artery bypass grafting (CABG), 297 off-pump CABG, and 986 combined CABG and valve procedures. Records of patients with any signs of neurological complications were reviewed to extract 149 subjects with stroke at extubation (early, 1.6%) versus 99 patients having a free interval (delayed, 1.1%). Survival data were complete, with a median follow-up time of 9.3 years (maximum 16.3 years). Independent risk factors were analyzed by logistic regression and survival by Cox regression. RESULTS Risk factors for early stroke were advanced age, high preoperative creatinine level, extent of aortic atherosclerosis, and long cardiopulmonary bypass time (all P<0.001). Factors associated with delayed stroke were female gender (P<0.001), unstable angina (P=0.003), previous cerebrovascular disease (P=0.009), inotropic support requirement (P<0.001), and postoperative atrial fibrillation (P<0.001). Stroke explained mortality not only in the early postoperative period (P<0.001), but also at long-term follow-up (P<0.001). Early and delayed stroke were associated with mortality hazard ratios (HRs) of 1.44 and 1.85 (P=0.008, P<0.001), respectively. However, for patients surviving their first postoperative year, early stroke did not influence long-term mortality (HR 1.07, P=0.695). This was in contrast to delayed stroke (HR 1.71, P=0.001). CONCLUSIONS Early and delayed stroke differed in their related risk factors. The influence of stroke on short-term mortality was obvious and devastating. Mortality in association with early stroke mainly presented itself in the acute period, whereas for delayed stroke survival continued to be impaired also in the long-term perspective. Our report emphasizes that early and delayed stroke should be considered as two separate entities.

Embolic material generated by multiple aortic crossclamping: a perfusion model with human cadaveric aorta

BACKGROUND Atherosclerosis of the ascending aorta and use of aortic crossclamping are risk factors for neurologic injury during cardiac surgery. OBJECTIVES Repeated aortic manipulation is part of the surgical approach to most cardiac operations. The aim of this study was to assess the amount and size of particulate matter that is dislodged from the aortic wall as a function of repeated aortic crossclamping. METHODS In 10 subjects undergoing autopsy the aorta was dissected and mounted in a perfusion model. The ascending aorta was crossclamped and washed out 10 times, with the perfusate collected in aliquots (1 to 10). The aliquots were examined by computerized image processing, both macroscopically and under the microscope for calcified and cellular material. RESULTS Aortic crossclamping produced substantial output of particulate matter. After repeated aortic crossclamping the number of particles decreased (P =.012) and approached the baseline for aliquots 6 to 10. The average particle diameter was 0.63 +/- 0.03 mm, with a maximum of 4.74 mm. Similar variability in particle outputs were recorded microscopically, with findings of both calcified and cellular material. Nine of 10 aortas had calcifications seen during simple visual inspection. CONCLUSIONS The washouts of dislodge material at aortic crossclamping had embolic potential. During the initial aortic crossclamping procedures the amount of particles was substantial, both macroscopically and microscopically. On the microscopic scale noncalcified cellular debris represents a significant pool of embolic material. Repeated aortic crossclamping reduced the amount of particles. These findings question surgical techniques associated with repeated aortic crossclamping.

Are current smokers paradoxically protected against atrial fibrillation after cardiac surgery

BACKGROUND The hyperadrenergic condition following surgical stress and inotropic drugs have been identified as leading causes for postoperative atrial fibrillation (AF). Smokers are characterized by higher catecholamine levels and tolerance. We tested the hypothesis that smoking patients are less prone to develop postoperative AF. METHODS A total of 3,245 coronary artery bypass and valvular procedures were reviewed. Predictors of AF and interaction between variables were explored by multivariable logistic regression. AF-predictive scores were created and validated for goodness of fit, and receiver operating characteristic curves were created. RESULTS Postoperative AF occurred in 26% of patients. Smokers accounted for 15% of the study population and demonstrated a reduced incidence of postoperative AF compared with nonsmoking individuals (20% vs. 27%, p < .001). Multivariate analysis revealed a significant interaction between smoking status and inotropic support requirement. The AF-protective effect of smoking was confounded by inotropic drugs. However, when we excluded from analysis the patients with inotropic support, smoking conferred a 46% risk reduction of AF (odds ratio [OR] = 0.54, 95% CI = 0.34-0.87, p = .011). In addition, age, valvular surgery, and hypertension were independently associated with AF. Postoperative AF increased the length of hospitalization, without affecting hospital mortality. AF was associated with an increased 1-year mortality (p = .002). DISCUSSION Current smokers are less prone to develop AF after cardiac surgery. Our data support the hypothesis that hyperadrenergic state and catecholamines are key mechanisms in the pathophysiology of postoperative AF.

Cerebrovascular accidents after cardiac surgery: an analysis of CT scans in relation to clinical symptoms.

There is a link between aortic manipulation, particle embolization, and cerebrovascular accidents (CVA) in cardiac surgery. The present aim was to study hemispheric side differences of CVA. Cardiac-surgery patients with CVA and with computer tomography (CT) performed (n = 77) were analyzed within a total group of 2641 consecutive cases. CT data were reviewed for hemispheric and vascular distribution, and compared with CVA-symptom data of immediate and delayed type. Of the included patients, 66% had positive CT. In the group of ‘cardiac-type’ operations (e.g., routine clamping and cannulation) and having immediate CVA, right-hemispheric lesions were more frequent than of the contra-lateral side (p = 0.005). Patients with aortic dissections had strong dominance of bilateral findings, which was different from the unilateral pattern of ‘cardiac-type’ operations (p = 0.001). The middle-cerebral artery territory dominated, and when involved showed a significant (p = 0.022) right-sided distribution. Both CT and clinical symptoms confirmed that CVA after cardiac surgery has a right-hemispheric predominance. These observations may imply that aortic manipulation directs embolic material towards the brachiocephalic trunk.

Fat reduction in pericardial suction blood by spontaneous density separation: an experimental model on human liquid fat versus soya oil

Pericardial suction blood (PSB) contains mediastinal liquid wound fat with an embolic potential to cause brain damage after cardiopulmonary bypass (CPB). The aims were to measure how fat separates spontaneously from blood by density and how temperature and fat surface adhesion affect the results under experimental conditions. Human liquid fat was heat-extracted from retrieved pericardial fat tissue of coronary artery bypass graft (CABG) patients ( n =10). Human fat or soya oil, 5% and 10%, respectively, were mixed with postoperatively shed mediastinal blood ( n =20). The mixture was loaded into a temperature-controlled (37°C, 20°C, 10°C) vertical separation column. At 1, 2.5, 5 and 10 minutes, the blood was collected in five fractions, representing layers of density separation, followed by centrifugation. Human fat solidified at 8°C. Soya oil remained liquid below 0°C. Soya oil separated fast in water, but was slower in blood. At 10 minutes and 37°C 73±6% of added soya oil was found in the top 20% fraction. Human fat at 37°C behaved similarly to soya oil, with 58-2% separation at 10 minutes. However, at lower temperatures the density separation became less efficient ( p <0.001), whereas human fat more effectively adhered to the walls of the column, which added to the removal. In total, 66%-78% of the human fat was removed, depending on temperature. In conclusion, fat in PSB can be reduced by simple density separation and surface adhesion while it is temporarily retained from the CPB circuit.

The embolic potential of liquid fat in pericardial suction blood, and its elimination:

Diffuse brain damage is a complex problem in cardiac surgery postoperatively. Liquid fat from recycled pericardial suction blood (PSB) is an embolic source. PSB can be discarded, but the recycling can be life saving, and methods have been developed to remove the fat. Blood washing by centrifugation is suggested to be the most effective method. In retained PSB, fat also separates without centrifugation, which is a novel and simple approach. Alternatively, inline fat filtration is easily accomplished but its effectiveness has been questioned. The present study aimed to investigate this phenomenon. Fat was heat extracted from retrieved pericardial fat tissue of coronary artery bypass graft (CABG) patients (n= 6), and was mixed, 1.25%, with postoperative mediastinal-shed blood. The mixture was filtered using a LipiGuard SB at constant flow rate. The filtration was scaled down to 3 mL and performed under temperature control, 37°C, 20°C and 10°C. At these temperatures fat removal was 46.9±6.1%, 61.5±7.0% and 76.8±5.0%, respectively, with a statistical difference of P=0.001. The improved fat removal at low temperature dramatically increased filtration pressures (p<0.001) and caused haemolysis (P=0.018). It is concluded that fat filtration is technically difficult. Cooling of blood increases fat extraction, but with negative side effects due to filter occlusion.