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- Hedberg, Magnus, 1981-
(författare)
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Stroke during cardiac surgery : risk factors, mechanisms and survival effects
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Neurological complications and stroke in association with cardiac surgery is a serious problem. The stroke event can occur during surgery (early stroke) or in the postoperative period with a symptom free interval (delayed stroke). Particle embolization due to aortic manipulation during surgery has been suspected as a mechanism for early stroke. The present thesis address mechanisms and survival effects of stroke both clinically (I-III) and experimentally (IV-V). Methods: Study I) Within a cohort of 2641 consecutive cases, a group of cardiac surgery patients with stroke and evaluated by computed tomography (CT) were studied (n=77). CT-findings were analyzed in relation to stroke symptoms. Study II) Data from 9122 patients undergoing coronary surgery were analyzed. 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%). Early and delayed stroke were evaluated separately. Independent risk factors for stroke were analyzed by logistic regression and survival by Cox regression (9.3 years median follow-up). Study III) Patients with early (n=223) and delayed stroke (n=116) were identified among 10809 patients undergoing cardiac and aortic surgery, both groups exposed to cardiopulmonary bypass. Stroke patients were subdivided by the hemispheric location of lesions. Subgroups were compared and their associated pre- and peroperative variables and survival were analyzed. Study IV) Aortic cross-clamp manipulation was studied in a human cadaveric perfusion model. The pressurized aorta was repeatedly cross-clamped and washout samples were collected before and after clamp maneuvers. Particles in the washout samples were evaluated by microscopy and by digital image analysis. Study V) Pig aortas were pressurized and cannulated. Washout samples were collected before and after cannulation (n = 40). Particles were deposited onto a 10-μm filter to be evaluated by microscopy and digital image analysis. Results: Study I) In the group of patients exposed to routine cardiac surgery (i.e., clamping and cannulation) and with early stroke, right-hemispheric lesions were more frequent than of the contra-lateral side (P=0.005). Patients with aortic dissections had a strong dominance of bilateral findings, which was different from the unilateral pattern in the routine-surgery group (P<0.001). Study II) Early and delayed stroke did not share any risk factors. Both early and delayed stroke explained mortality in the early postoperative period (P<0.001, P<0.001 respectively) but also at long term follow-up (P=0.008, P<0.001 respectively). For patients surviving their first postoperative year, delayed but not early stroke influenced long-term mortality (P=0.001 and P=0.695, respectively). Study III) Stroke lesions in association to cardiac surgery were near exclusively ischemic. Early stroke had a preponderance for right-hemispheric lesions (P=0.009). In contrast, patients with early stroke that had undergone surgery of the aorta with circulatory arrest showed a pattern with more bilateral lesions compared to ‘cardiac-type’ operations (P<0.001). Patients with bilateral lesions had a dramatically impaired survival compared to those with unilateral lesions (P<0.001). Study IV) In the cadaveric perfusion model, cross-clamping produced a significant output of particles, which was seen for size intervals of 1 mm and smaller (P=0.002 to P=0.022). In all size intervals the particle output correlated with the degree of overall aortic calcification (P =0.002 to P=0.025). Study V) At cannulation of the pig aorta, more particles were noted after cannulation compared to before the maneuver (P<0.001). This increase included small (<0.1 mm, P<0.001) and intermediate-size particles (0.1-0.5 mm, P< 0.001). Particles above 0.5 mm were few and were not associated with cannulation. Conclusions: The influence of stroke on mortality was devastating, for both early and delayed stroke. These two stroke groups had obvious differences in both their risk factors and their hemispheric distribution. It is here emphasized that early and delayed stroke should be considered as two separate entities with suggested mechanistic differences. Ischemic lesions accounted for near all stroke events seen in association to cardiac surgery. For early stroke, these were mostly located within the right hemisphere. Results from the experimental studies underscore microembolic risks associated with aortic manipulation.
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| 2. |
- Holm, Jonas, 1971-
(författare)
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Markers of hemodynamic state and heart failure as predictors for outcome in cardiac surgery : with special reference to mixed venous oxygen saturation and natriuretic peptides
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Postoperative heart failure or low cardiac output syndrome is the major cause for morbidity and mortality in cardiac surgery. Unfortunately commonly used methods to assess hemodynamic state and heart failure are not well documented with regard to outcome. The aim for this dissertation was to study the predictive values of postoperative Mixed Venous Oxygen saturation (SvO2) and preoperative NT-proBNP for outcomes related to postoperative heart failure.SvO2 was studied retrospectively in two cohorts of patients, one cohort operated with isolated Aortic Valve Replacement (AVR) for aortic stenosis, (n=396) and one operated with isolated Coronary Artery Bypass Grafting (CABG), (n=2755). SvO2 measured early after surgery, on admission to the intensive care unit (ICU), predicted postoperative morbidity and mortality. Our results suggest that, on admission to ICU SvO2 < 55 - 60% after AVR and SvO2 < 60% after CABG merits increased attention.Preoperative NT-proBNP was studied in a cohort of patients with acute coronary syndrome (ACS) undergoing CABG with or without concomitant procedure. These patients (n=383) were included prospectively and evaluated with regard to mortality and severe circulatory failure postoperatively by an end-points committee blinded to NT-proBNP results. Preoperative NT-proBNP ≥ 1028 ng/L independently predicted increased risk for severe circulatory failure postoperatively in patients with ACS undergoing isolated CABG. Preoperative NT-proBNP provided additional prognostic information to EuroSCORE II in this cohort, particularly in patients at intermediate risk. Preoperative NT-proBNP appears to be markedly higher in patients having CABG with concomitant procedures than in patients undergoing isolated CABG. Further studies are warranted to identify preoperative NTproBNP risk thresholds for different heart conditions and surgery-specific cohorts.In conclusion this dissertation shows that:Postoperative SvO2 on admission to ICU is a prognostic marker for morbidity and mortality after AVR and CABG.Preoperative NT-proBNP ≥ 1028 ng/L independently predicts severe circulatory failure postoperatively in patients undergoing isolated CABG and provides additional prognostic information to EuroSCORE II.The high negative predictive value of the identified cutoff levels for preoperative NTproBNP and postoperative SvO2 could be useful for pre and postoperative decisionmaking.
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| 3. |
- Olsson, Christian, 1973-
(författare)
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Thoracic Aortic Surgery : Epidemiology, Outcomes, and Prevention of Cerebral Complications
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The mortality of thoracic aortic diseases (mainly aneurysms and dissections) is high, even with surgical treatment. Epidemiology and long-term outcomes are incompletely investigated. Stroke is a major complication contributing to mortality, morbidity, and possibly to reduced quality of life. Study I Increasing incidence of thoracic aortic diseases 1987 – 2002 was demonstrated (n=14229). Annual number of operations increased eight-fold. Overall long-time survival was 92%, 77%, and 57% at 1, 5, and 10 years. Risk of operative and long-term mortality was reduced across time. Study II 2634 patients operated on the proximal thoracic aorta (Swedish Heart Surgery register) were examined. Aortic valve replacement, coronary revascularization, emergency operation, and age were independently associated with surgical death. Long-term mortality was similar for aneurysms and dissections. Operative mortality was reduced (13.7% vs 7.2%) for aneurysms but remained unchanged (22.3% vs 22.4%) for dissections across time. Study III 65 patients underwent selective antegrade cerebral perfusion (SACP) uni- or bilaterally. Stroke was significantly more common after unilateral SACP (29% vs 8%, p=0.045), confirmed by propensity score-matched analysis. Subclavian artery cannulation with Seldinger-technique entailed vascular complication in one case (1.5%). Study IV Near-infrared spectroscopy (NIRS) was used to monitor cerebral tissue saturation (rSO2) during SACP in 46 patients. Lower rSO2 were encountered (1) in patients suffering a stroke (2) with unilateral SACP, and (3) in the affected hemisphere of stroke victims. A decrease of rSO2 by 14 – 21% from baseline increased the risk of stroke significantly. Study V Quality of life (QoL) in 76 survivors of thoracic aortic surgery was examined with the SF-36 health questionnaire. Except for pain, QoL was reduced in all dimensions. QoL was not affected by acuity of operation. Tendencies of lower QoL after descending aortic operations, after major complications, and with persistent dysfunction were non-significant.
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