Selective β1-Antagonism with Bisoprolol Is Associated with Fewer Postoperative Strokes than Atenolol or Metoprolol

Association of migraine treatments with reduced ischemic stroke risk: Evidence from two large-scale real-world data analyses

OBJECTIVE

To compare the risk of ischemic stroke in patients with migraine treated with first-line medications, including valproate, topiramate, metoprolol, timolol, or propranolol, versus those not receiving these treatments, using data from two large electronic health records datasets.

BACKGROUND

The impact of first-line migraine medications on ischemic stroke risk in patients with migraine remains uncertain, highlighting the need for further investigation.

METHODS

We conducted a retrospective case-control study using data from Vanderbilt University Medical Center (VUMC) and the All of Us Research Program. Cases were patients with a primary ischemic stroke diagnosis after their first migraine diagnosis, while controls had no ischemic stroke following their initial migraine diagnosis.

RESULTS

In the VUMC database, 356 cases and 15,231 controls were identified; the All of Us database included 256 cases and 6590 controls. Propranolol was the only medication significantly associated with a reduced risk of ischemic stroke in female patients with migraine (VUMC: adjusted odds ratio [aOR] 0.55, 95% confidence interval [CI] 0.33-0.86, p = 0.013; All of Us: aOR 0.41, 95% CI 0.19-0.77, p = 0.010), particularly in those with migraine without aura (VUMC: aOR 0.53, 95% CI 0.29-0.90, p = 0.027; All of Us: aOR 0.28, 95% CI 0.10-0.62, p = 0.006). The Cox model showed lower ischemic stroke rates in propranolol-treated female patients with migraine at 10 years in the VUMC data (adjusted hazard ratio [aHR] 0.45, 95% CI 0.24-0.83; p = 0.011, log-rank p < 0.001) and 10 years in the All of Us data (aHR 0.29, 95% CI 0.09-0.87; p = 0.048, log-rank p = 0.003).

CONCLUSIONS

Among various migraine treatments, propranolol was notably associated with a significant reduction in ischemic stroke risk among female patients with migraine, particularly those without aura. These findings suggest a potential dual benefit of propranolol in managing migraine and reducing stroke risk, highlighting the need for further prospective studies to confirm these results and potentially inform clinical practice.

Clinical outcome in hypertensive patients treated with amlodipine plus bisoprolol or plus valsartan

OBJECTIVE

Several guidelines do not recommend beta-blocker as the first-line treatment for hypertension because of its inferior efficacy in stroke prevention. Combination therapy with beta-blocker is commonly used for blood pressure control. We compared the clinical outcomes in patients treated with amlodipine plus bisoprolol (A + B), a ß1-selective beta-blocker and amlodipine plus valsartan (A + V).

METHODS

A population-based cohort study was performed using data from the Taiwan National Health Insurance Research Database. From 2012 to 2019, newly diagnosed adult hypertensive patients who received initial amlodipine monotherapy and then switched to A + V or A + B were included. The efficacy outcomes included all-cause death, atherosclerotic cardiovascular disease (ASCVD) event (cardiovascular death, myocardial infarction, ischemic stroke, and coronary revascularization), hemorrhagic stroke, and heart failure. Multivariable Cox proportional hazards model was used to evaluate the relationship between outcomes and different treatments.

RESULTS

Overall, 4311 patients in A + B group and 10980 patients in A + V group were included. After a mean follow-up of 4.34 ± 1.79 years, the efficacy outcomes were similar between the A + V and A + B groups regarding all-cause death (adjusted hazard ratio [aHR] 0.99, 95% confidence interval [CI] 0.83-1.18), ASCVD event (aHR 0.97, 95% CI 0.84-1.12), and heart failure (aHR 1.06, 95% CI 0.87-1.30). The risk of hemorrhagic stroke was lower in A + B group (aHR 0.70, 95% CI 0.52-0.94). The result was similar when taking death into consideration in competing risk analysis. The safety outcomes were similar between the 2 groups.

CONCLUSIONS

There was no difference of all-cause death, ASCVD event, and heart failure in A + B vs. A + V users. But A + B users had a lower risk of hemorrhagic stroke.

Bilateral nephrectomy impairs cardiovascular function and cerebral perfusion in a rat model of acute hemodilutional anemia

Anemia and renal failure are independent risk factors for perioperative stroke, prompting us to assess the combined impact of acute hemodilutional anemia and bilateral nephrectomy (2Nx) on microvascular brain Po2 (PBro2) in a rat model. Changes in PBro2 (phosphorescence quenching) and cardiac output (CO, echocardiography) were measured in different groups of anesthetized Sprague-Dawley rats (1.5% isoflurane, n = 5-8/group) randomized to Sham 2Nx or 2Nx and subsequently exposed to acute hemodilutional anemia (50% estimated blood volume exchange with 6% hydroxyethyl starch) or time-based controls (no hemodilution). Outcomes were assessed by ANOVA with significance assigned at P < 0.05. At baseline, 2Nx rats demonstrated reduced CO (49.9 ± 9.4 vs. 66.3 ± 19.3 mL/min; P = 0.014) and PBro2 (21.1 ± 2.9 vs. 32.4 ± 3.1 mmHg; P < 0.001) relative to Sham 2Nx rats. Following hemodilution, 2Nx rats demonstrated a further decrease in PBro2 (15.0 ± 6.3 mmHg, P = 0.022). Hemodiluted 2Nx rats did not demonstrate a comparable increase in CO after hemodilution compared with Sham 2Nx (74.8 ± 22.4 vs. 108.9 ± 18.8 mL/min, P = 0.003) that likely contributed to the observed reduction in PBro2. This impaired CO response was associated with reduced fractional shortening (33 ± 9 vs. 51 ± 5%) and increased left ventricular end-systolic volume (156 ± 51 vs. 72 ± 15 µL, P < 0.001) suggestive of systolic dysfunction. By contrast, hemodiluted Sham 2Nx animals demonstrated a robust increase in CO and preserved PBro2. These data support the hypothesis that the kidney plays a central role in maintaining cerebral perfusion and initiating the adaptive increase in CO required to optimize PBro2 during acute anemia.NEW & NOTEWORTHY This study has demonstrated that bilateral nephrectomy acutely impaired cardiac output (CO) and microvascular brain Po2 (PBro2), at baseline. Following acute hemodilution, nephrectomy prevented the adaptive increase in CO associated with acute hemodilution leading to a further reduction in PBro2, accentuating the degree of cerebral tissue hypoxia. These data support a role for the kidney in maintaining PBro2 and initiating the increase in CO that optimized brain perfusion during acute anemia.

Risk factors for postoperative acute ischemic stroke in advanced-aged patients with previous stroke undergoing noncardiac surgery: a retrospective cohort study

BACKGROUND

The current study aimed to investigate the incidence and risk factors for postoperative acute ischemic stroke (PAIS) in advanced-aged patients (≥ 75 years) with previous ischemic stroke undergoing noncardiac surgery.

METHODS

In this single-center retrospective cohort study, all advanced-aged patients underwent noncardiac surgery from 1 January, 2019, to 30 April, 2022. Data were extracted from hospital electronic medical records. Multivariable logistic regression analysis was performed to determine predictors of PAIS. Multivariable linear or logistic regression analysis was performed to determine predictors of outcomes due to PAIS.

RESULTS

Twenty-four patients (6.0%) of the 400 patients developed PAIS. Carotid endarterectomy (CEA), length of surgery and preoperative Modified Rankin scale (mRS) ≥ 3 were significant predictors of PAIS. CEA was associated with increased risk of PAIS (OR 4.14; 95%CI, 1.43-11.99). Each additional minute in length of surgery had slightly increased the risk of PAIS (OR, 1.01; 95%CI, 1.00-1.01). Compared with reference (mRS < 3), mRS ≥ 3 increased odds of PAIS (OR, 4.09;95%CI, 1.12-14.93). Surgery type and length of surgery were found to be significant predictors of in-hospital expense (P < 0.001) and hospital stays (P < 0.05).

CONCLUSIONS

CEA, length of surgery and preoperative mRS ≥ 3 may increase the development of PAIS in advanced-aged patients (≥ 75 years) with previous stroke undergoing noncardiac surgery. PAIS increased in-hospital mortality and prolonged hospital stay.

Importance of assessing biomarkers and physiological parameters of anemia-induced tissue hypoxia in the perioperative period

Anemia is associated with increased risk of Acute Kidney Injury (AKI), stroke and mortality in perioperative patients. We sought to understand the mechanism(s) by assessing the integrative physiological responses to anemia (kidney, brain), the degrees of anemia-induced tissue hypoxia, and associated biomarkers and physiological parameters. Experimental measurements demonstrate a linear relationship between blood Oxygen Content (C_aO₂) and renal microvascular PO₂ (y = 0.30x + 6.9, r² = 0.75), demonstrating that renal hypoxia is proportional to the degree of anemia. This defines the kidney as a potential oxygen sensor during anemia. Further evidence of renal oxygen sensing is demonstrated by proportional increase in serum Erythropoietin (EPO) during anemia (y = 93.806*10^-0.02, r² = 0.82). This data implicates systemic EPO levels as a biomarker of anemia-induced renal tissue hypoxia. By contrast, cerebral Oxygen Delivery (DO₂) is defended by a profound proportional increase in Cerebral Blood Flow (CBF), minimizing tissue hypoxia in the brain, until more severe levels of anemia occur. We hypothesize that the kidney experiences profound early anemia-induced tissue hypoxia which contributes to adaptive mechanisms to preserve cerebral perfusion. At severe levels of anemia, renal hypoxia intensifies, and cerebral hypoxia occurs, possibly contributing to the mechanism(s) of AKI and stroke when adaptive mechanisms to preserve organ perfusion are overwhelmed. Clinical methods to detect renal tissue hypoxia (an early warning signal) and cerebral hypoxia (a later consequence of severe anemia) may inform clinical practice and support the assessment of clinical biomarkers (i.e., EPO) and physiological parameters (i.e., urinary PO₂) of anemia-induced tissue hypoxia. This information may direct targeted treatment strategies to prevent adverse outcomes associated with anemia.

Carbon Dioxide, Blood Pressure, and Perioperative Stroke: A Retrospective Case-Control Study

BACKGROUND

The relationship between intraoperative physiology and postoperative stroke is incompletely understood. Preliminary data suggest that either hypo- or hypercapnia coupled with reduced cerebrovascular inflow (e.g., due to hypotension) can lead to ischemia. This study tested the hypothesis that the combination of intraoperative hypotension and either hypo- or hypercarbia is associated with postoperative ischemic stroke.

METHODS

We conducted a retrospective, case-control study via the Multicenter Perioperative Outcomes Group. Noncardiac, nonintracranial, and nonmajor vascular surgical cases (18 yr or older) were extracted from five major academic centers between January 2004 and December 2015. Ischemic stroke cases were identified via manual chart review and matched to controls (1:4). Time and reduction below key mean arterial blood pressure thresholds (less than 55 mmHg, less than 60 mmHg, less than 65 mmHg) and outside of specific end-tidal carbon dioxide thresholds (30 mmHg or less, 35 mmHg or less, 45 mmHg or greater) were calculated based on total area under the curve. The association between stroke and total area under the curve values was then tested while adjusting for relevant confounders.

RESULTS

In total, 1,244,881 cases were analyzed. Among the cases that screened positive for stroke (n = 1,702), 126 were confirmed and successfully matched with 500 corresponding controls. Total area under the curve was significantly associated with stroke for all thresholds tested, with the strongest combination observed with mean arterial pressure less than 55 mmHg (adjusted odds ratio per 10 mmHg-min, 1.17 [95% CI, 1.10 to 1.23], P < 0.0001) and end-tidal carbon dioxide 45 mmHg or greater (adjusted odds ratio per 10 mmHg-min, 1.11 [95% CI, 1.10 to 1.11], P < 0.0001). There was no interaction effect observed between blood pressure and carbon dioxide.

CONCLUSIONS

Intraoperative hypotension and carbon dioxide dysregulation may each independently increase postoperative stroke risk.

EDITOR’S PERSPECTIVE

Effects of short-term bisoprolol on perioperative myocardial injury in patients undergoing non-cardiac surgery: a randomized control study

The protective role of preoperative beta-blocker in patients undergoing non-cardiac surgery is unknown. We aimed to evaluate the effects of beta-blocker on perioperative myocardial injury in patients undergoing non-cardiac surgery. We consecutively enrolled 112 patients undergoing non-cardiac surgery. They were randomly allocated to receive bisoprolol or placebo given at least 2 days preoperatively and continued until 30 days after surgery. The primary outcome was incidence of perioperative myocardial injury defined by a rise of high-sensitive troponin-T (hs-TnT) more than 99th percentile of upper reference limit or a rise of hs-TnT more than 20% if baseline level is abnormal. Baseline characteristics were comparable between bisoprolol and placebo in randomized cohort Mean age was 62.5 ± 11.8 years and 76 (67.8%) of 112 patients were male. Among 112 patients, 49 (43.8%) underwent vascular surgery and 63 (56.2%) underwent thoracic surgery. The median duration of assigned treatment prior to surgery was 4 days (2-6 days). We did not demonstrate the significant difference in the incidence of perioperative myocardial injury [52.6% (30 of 57 patients) vs. 49.1% (27 of 55 patients), P = 0.706]. In addition, the incidence of intraoperative hypotension was higher in bisoprolol group than placebo group in patients undergoing non-cardiac surgery [70.2% (40 of 57 patients) vs. 47.3% (26 of 55 patients), P = 0.017]. We demonstrated that there was no statistically significant difference in perioperative myocardial injury observed between patients receiving bisoprolol and placebo who had undergone non-cardiac surgery.

Perioperative Care of Patients at High Risk for Stroke During or After Non-cardiac, Non-neurological Surgery: 2020 Guidelines From the Society for Neuroscience in Anesthesiology and Critical Care

Perioperative stroke is associated with considerable morbidity and mortality. Stroke recognition and diagnosis are challenging perioperatively, and surgical patients receive therapeutic interventions less frequently compared with stroke patients in the outpatient setting. These updated guidelines from the Society for Neuroscience in Anesthesiology and Critical Care provide evidence-based recommendations regarding perioperative care of patients at high risk for stroke. Recommended areas for future investigation are also proposed.

Acute Ischemic Stroke

Anesthesiologists provide care to acute and subacute ischemic stroke (IS) patients and stroke survivors in interventional radiology, intensive care, and operating rooms. These encounters will become more frequent following studies that have extended the treatment window from last known well time for fibrinolytic and endovascular thrombectomy (EVT). The number of stroke centers certified to quickly and effectively initiate treatment of IS patients and the number of patients connected to them by telehealth continue to grow. This article reviews IS pathophysiology, assessment, treatment, pathology, and complications; anesthetic management during EVT; perioperative stroke management; and how anesthesia has an impact on patients with prior stroke.

Disease Mechanisms of Perioperative Organ Injury

Despite substantial advances in anesthesia safety within the past decades, perioperative mortality remains a prevalent problem and can be considered among the top causes of death worldwide. Acute organ failure is a major risk factor of morbidity and mortality in surgical patients and develops primarily as a consequence of a dysregulated inflammatory response and insufficient tissue perfusion. Neurological dysfunction, myocardial ischemia, acute kidney injury, respiratory failure, intestinal dysfunction, and hepatic impairment are among the most serious complications impacting patient outcome and recovery. Pre-, intra-, and postoperative arrangements, such as enhanced recovery after surgery programs, can contribute to lowering the occurrence of organ dysfunction, and mortality rates have improved with the advent of specialized intensive care units and advances in procedures relating to extracorporeal organ support. However, no specific pharmacological therapies have proven effective in the prevention or reversal of perioperative organ injury. Therefore, understanding the underlying mechanisms of organ dysfunction is essential to identify novel treatment strategies to improve perioperative care and outcomes for surgical patients. This review focuses on recent knowledge of pathophysiological and molecular pathways leading to perioperative organ injury. Additionally, we highlight potential therapeutic targets relevant to the network of events that occur in clinical settings with organ failure.

Renal microvascular oxygen tension during hyperoxia and acute hemodilution assessed by phosphorescence quenching and excitation with blue and red light

PURPOSE

The kidney plays a central physiologic role as an oxygen sensor. Nevertheless, the direct mechanism by which this occurs is incompletely understood. We measured renal microvascular partial pressure of oxygen (P_kO₂) to determine the impact of clinically relevant conditions that acutely change P_kO₂ including hyperoxia and hemodilution.

METHODS

We utilized two-wavelength excitation (red and blue spectrum) of the intravascular phosphorescent oxygen sensitive probe Oxyphor PdG4 to measure renal tissue PO₂ in anesthetized rats (2% isoflurane, n = 6) under two conditions of altered arterial blood oxygen content (C_aO₂): 1) hyperoxia (fractional inspired oxygen 21%, 30%, and 50%) and 2) acute hemodilutional anemia (baseline, 25% and 50% acute hemodilution). The mean arterial blood pressure (MAP), rectal temperature, arterial blood gases (ABGs), and chemistry (radiometer) were measured under each condition. Blue and red light enabled measurement of P_kO₂ in the superficial renal cortex and deeper cortical and medullary tissue, respectively.

RESULTS

P_kO₂ was higher in the superficial renal cortex (~ 60 mmHg, blue light) relative to the deeper renal cortex and outer medulla (~ 45 mmHg, red light). Hyperoxia resulted in a proportional increase in P_kO₂ values while hemodilution decreased microvascular P_kO₂ in a linear manner in both superficial and deeper regions of the kidney. In both cases (blue and red light), P_kO₂ correlated with C_aO₂ but not with MAP.

CONCLUSION

The observed linear relationship between C_aO₂ and P_kO₂ shows the biological function of the kidney as a quantitative sensor of anemic hypoxia and hyperoxia. A better understanding of the impact of changes in P_kO₂ may inform clinical practices to improve renal oxygen delivery and prevent acute kidney injury.

Management of Acute Ischemic Stroke-Specific Focus on Anesthetic Management for Mechanical Thrombectomy

Acute ischemic stroke is a neurological emergency with a high likelihood of morbidity, mortality, and long-term disability. Modern stroke care involves multidisciplinary management by neurologists, radiologists, neurosurgeons, and anesthesiologists. Current American Heart Association/American Stroke Association (AHA/ASA) guidelines recommend thrombolytic therapy with intravenous (IV) alteplase within the first 3-4.5 hours of initial stroke symptoms and endovascular mechanical thrombectomy within the first 16-24 hours depending on specific inclusion criteria. The anesthesia and critical care provider may become involved for airway management due to worsening neurologic status or to enable computerized tomography (CT) or magnetic resonance imaging (MRI) scanning, to facilitate mechanical thrombectomy, or to manage critical care of stroke patients. Existing data are unclear whether the mechanical thrombectomy procedure is best performed under general anesthesia or sedation. Retrospective cohort trials favor sedation over general anesthesia, but recent randomized controlled trials (RCT) neither suggest superiority nor inferiority of sedation over general anesthesia. Regardless of anesthesia type, a critical element of intraprocedural stroke care is tight blood pressure management. At different phases of stroke care, different blood pressure targets are recommended. This narrative review will focus on the anesthesia and critical care providers' roles in the management of both perioperative stroke and acute ischemic stroke with a focus on anesthetic management for mechanical thrombectomy.

Perioperative Stroke

PURPOSE OF REVIEW

This review overviews perioperative stroke as it pertains to specific surgical procedures.

RECENT FINDINGS

As awareness of perioperative stroke increases, so does the opportunity to potentially improve outcomes for these patients by early stroke recognition and intervention. Perioperative stroke is defined to be any stroke that occurs within 30 days of the initial surgical procedure. The incidence of perioperative stroke varies and is dependent on the specific type of surgery performed. This chapter overviews the risks, mechanisms, and acute evaluation and management of perioperative stroke in four surgical populations: cardiac surgery, carotid endarterectomy, neurosurgery, and non-cardiac/non-carotid/non-neurological surgeries.

Cochrane Corner: Perioperative beta-blockers for preventing surgery-related mortality and morbidity

Randomized controlled trials have yielded conflicting results regarding the impact of beta-blockers on perioperative cardiovascular morbidity and mortality. This Cochrane systematic review assessed the impact of this intervention on mortality and cardiovascular events. Eighty-eight randomized controlled trials with 19 161 participants were included (53 trials on cardiac surgery and 35 trials on non-cardiac surgery). In cardiac surgery perioperative beta-blockers had a protective effect against supraventricular and ventricular arrhythmias but had no significant effect on mortality or on the occurrence of acute myocardial infarction (AMI), stroke, heart failure, hypotension or bradycardia. In non-cardiac surgery, beta-blockers had a protective effect against AMI and arrhythmias, but this was counterbalanced by an increased risk of death and stroke. In conclusion, perioperative use of beta-blockers appears overall to be beneficial in cardiac surgery. However, in non-cardiac surgery the substantial reduction in rhythm disturbances and AMI appears to be offset by an increase in mortality and stroke, and so the systematic use of beta-blockers in this setting is not recommended.

Cost-Effectiveness Analysis of Landiolol, an Ultrashort-Acting Beta-Blocker, for Prevention of Postoperative Atrial Fibrillation for the Germany Health Care System

OBJECTIVES

Landiolol is an ultrashort-acting beta-blocker with high beta-1 receptor affinity and less blood pressure-lowering properties than other beta-blockers available for intravenous use in Germany. The present analysis aimed to determine whether perioperative treatment with landiolol in cardiac surgical patients is cost-effective under the conditions of the German Diagnosis-Related Groups health cost reimbursement system.

DESIGN

On the basis of clinical outcome data from a meta-analysis that included 622 patients from 7 randomized controlled trials, a decision-model was developed to determine the cost-effectiveness of landiolol versus standard-of-care (SoC).

SETTING

Hospital setting.

PARTICIPANTS

Hospital patients undergoing a representative mix of cardiac surgical procedures (MIX-CS) and isolated coronary artery bypass grafting (CABG).

INTERVENTIONS

Landiolol versus SoC in prevention of atrial fibrillation immediately after cardiac surgery.

MEASUREMENTS AND MAIN RESULTS

The model benefit was expressed in a reduction of postoperative atrial fibrillation (POAF) episodes and reduced complications. The model calculated total inpatient costs over the hospital length of stay. Costs from published sources were used for the German hospital perspective. SoC was associated with POAF rates of 36.0% to 39.2% and 24.4% to 30.1% in the MIX-CS and CABG populations, respectively. Patients with POAF had a higher morbidity and mortality. Estimated total costs for SoC patients in the MIX-CS and CABG groups were 28.792 € and 25.630 €, respectively. Landiolol reduced the incidence of POAF to 12.6% in the MIX-CS and 12.1% in the CABG groups. This was associated with a cost reduction of 2.209 € and 1.470 €.

CONCLUSIONS

This analysis suggests that preventing POAF with landiolol is highly cost-effective. Additional studies are needed to assess whether a comparable reduction in POAF and associated cost savings may be achieved using conventional intravenous beta-blockers or amiodarone.

Contemporary personalized β-blocker management in the perioperative setting

Beta-adrenergic blockers (β-blockers) are clearly indicated for the long-term treatment of patients with systolic heart failure and post-acute myocardial infarction. Early small-scale studies reported their potential benefits for perioperative use; subsequent randomized controlled trials, however, failed to reproduce earlier findings. Furthermore, their role in reducing major postoperative cardiac events following noncardiac and cardiac surgery remains controversial. This case-based review presents an overview of contemporary literature on perioperative β-blocker use with a focus on data available since 2008 when the PreOperative ISchemic Evaluation (POISE) trial was published. Our review suggests that studies should determine the effects of situational-based guidelines on perioperative β-blocker use on the risk of cardiac adverse events and mortality in the perioperative period.

Beta-blockers in noncardiac surgery: Did observational studies put us back on safe ground?

Based on landmark trials, international guidelines had for years promoted the use of beta-blockers in the setting of non-cardiac surgery. In 2011, concerns were raised regarding the integrity of some of the landmark trials, as the Dutch Erasmus Medical Center found some of them to be scientifically incorrect. Based on the remaining studies that were to be trusted, investigations showed that, in contrast to prior beliefs, the widespread use of perioperative beta-blockers might be harmful. A call for further investigations into the matter ushered in several observational studies evaluating the safety of perioperative beta-blocker therapy in specific patient subgroups. Within this review, we discuss important aspects for making these decisions, and compare the major observational studies and specific estimates of risk in subgroups of interest. We conclude that patients at high risk with heavy co-morbidities, such as heart failure, may benefit from beta-blocker therapy, whereas low-risk patients, such as patients with uncomplicated hypertension, may be at increased risk with beta-blocker therapy. We provide a critical review of current perioperative guidelines in view of the new observational data, suggesting that the recommended schematics, such as the Revised Cardiac Risk Index, for risk stratification of patients in this setting may be suboptimal. Further, we provide discussions of other aspects, including risk of sepsis, type of beta-blocker, and the potential of perioperative beta-blocker withdrawal, which may be important in guiding future studies. Summarising the current evidence, we argue that, after a precarious decade, we may just now, be back on safe ground.

Functional and anatomical evidence of cerebral tissue hypoxia in young sickle cell anemia mice

Cerebral ischemia is a significant source of morbidity in children with sickle cell anemia; however, the mechanism of injury is poorly understood. Increased cerebral blood flow and low hemoglobin levels in children with sickle cell anemia are associated with increased stroke risk, suggesting that anemia-induced tissue hypoxia may be an important factor contributing to subsequent morbidity. To better understand the pathophysiology of brain injury, brain physiology and morphology were characterized in a transgenic mouse model, the Townes sickle cell model. Relative to age-matched controls, sickle cell anemia mice demonstrated: (1) decreased brain tissue pO₂ and increased expression of hypoxia signaling protein in the perivascular regions of the cerebral cortex; (2) elevated basal cerebral blood flow , consistent with adaptation to anemia-induced tissue hypoxia; (3) significant reduction in cerebrovascular blood flow reactivity to a hypercapnic challenge; (4) increased diameter of the carotid artery; and (5) significant volume changes in white and gray matter regions in the brain, as assessed by ex vivo magnetic resonance imaging. Collectively, these findings support the hypothesis that brain tissue hypoxia contributes to adaptive physiological and anatomic changes in Townes sickle cell mice. These findings may help define the pathophysiology for stroke in children with sickle cell anemia.

Experimental assessment of oxygen homeostasis during acute hemodilution: the integrated role of hemoglobin concentration and blood pressure

Background

Low hemoglobin concentration (Hb) and low mean arterial blood pressure (MAP) impact outcomes in critically ill patients. We utilized an experimental model of “normotensive” vs. “hypotensive” acute hemodilutional anemia to test whether optimal tissue perfusion is dependent on both Hb and MAP during acute blood loss and fluid resuscitation, and to assess the value of direct measurements of the partial pressure of oxygen in tissue (P_tO₂).

Methods

Twenty-nine anesthetized rats underwent 40% isovolemic hemodilution (1:1) (or sham-hemodilution control, n = 4) with either hydroxyethyl starch (HES) (n = 14, normotensive anemia) or saline (n = 11, hypotensive anemia) to reach a target Hb value near 70 g/L. The partial pressure of oxygen in the brain and skeletal muscle tissue (P_tO₂) were measured by phosphorescence quenching of oxygen using G4 Oxyphor. Mean arterial pressure (MAP), heart rate, temperature, arterial and venous co-oximetry, blood gases, and lactate were assessed at baseline and for 60 min after hemodilution. Cardiac output (CO) was measured at baseline and immediately after hemodilution. Data were analyzed by repeated measures two-way ANOVA.

Results

Following “normotensive” hemodilution with HES, Hb was reduced to 66 ± 6 g/L, CO increased (p < 0.05), and MAP was maintained. These conditions resulted in a reduction in brain P_tO₂ (22.1 ± 5.6 mmHg to 17.5 ± 4.4 mmHg, p < 0.05), unchanged muscle PO₂, and an increase in venous oxygen extraction. Following “hypotensive” hemodilution with saline, Hb was reduced to 79 ± 5 g/L and both CO and MAP were decreased (P < 0.05). These conditions resulted in a more severe reduction in brain P_tO₂ (23.2 ± 8.2 to 10.7 ± 3.6 mmHg (p < 0.05), a reduction in muscle P_tO₂ (44.5 ± 11.0 to 19.9 ± 12.4 mmHg, p < 0.05), a further increase in venous oxygen extraction, and a threefold increase in systemic lactate levels (p < 0.05).

Conclusions

Acute normotensive anemia (HES hemodilution) was associated with a subtle decrease in brain tissue P_tO₂ without clear evidence of global tissue hypoperfusion. By contrast, acute hypotensive anemia (saline hemodilution) resulted in a profound decrease in both brain and muscle tissue P_tO₂ and evidence of inadequate global perfusion (lactic acidosis). These data emphasize the importance of maintaining CO and MAP to ensure adequacy of vital organ oxygen delivery during acute anemia. Improved methods of assessing P_tO₂ may provide an earlier warning signal of vital organ hypoperfusion.

Pharmacological treatment of vascular risk factors for reducing mortality and cardiovascular events in patients with abdominal aortic aneurysm

BACKGROUND

Pharmacological prophylaxis has been proven to reduce the risk of cardiovascular events in individuals with atherosclerotic occlusive arterial disease. However, the role of prophylaxis in individuals with abdominal aortic aneurysm (AAA) remains unclear. Several studies have shown that despite successful repair, those people with AAA have a poorer rate of survival than healthy controls. People with AAA have an increased prevalence of coronary heart disease and risk of cardiovascular events. Despite this association, little is known about the effectiveness of pharmacological prophylaxis in reducing cardiovascular risk in people with AAA. This is an update of a Cochrane review first published in 2014.

OBJECTIVES

To determine the long-term effectiveness of antiplatelet, antihypertensive or lipid-lowering medication in reducing mortality and cardiovascular events in people with abdominal aortic aneurysm (AAA).

SEARCH METHODS

For this update the Cochrane Vascular Information Specialist (CIS) searched the Cochrane Vascular Specialised Register (14 April 2016). In addition, the CIS searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2016, Issue 3) and trials registries (14 April 2016) and We also searched the reference lists of relevant articles.

SELECTION CRITERIA

Randomised controlled trials in which people with AAA were randomly allocated to one prophylactic treatment versus another, a different regimen of the same treatment, a placebo, or no treatment were eligible for inclusion in this review. Primary outcomes included all-cause mortality and cardiovascular mortality.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies for inclusion, and completed quality assessment and data extraction. We resolved any disagreements by discussion. Only one study met the inclusion criteria of the review, therefore we were unable to perform meta-analysis.

MAIN RESULTS

No new studies met the inclusion criteria for this update. We included one randomised controlled trial in the review. A subgroup of 227 participants with AAA received either metoprolol (N = 111) or placebo (N = 116). There was no clear evidence that metoprolol reduced all-cause mortality (odds ratio (OR) 0.17, 95% confidence interval (CI) 0.02 to 1.41), cardiovascular death (OR 0.20, 95% CI 0.02 to 1.76), AAA-related death (OR 1.05, 95% CI 0.06 to 16.92) or increased nonfatal cardiovascular events (OR 1.44, 95% CI 0.58 to 3.57) 30 days postoperatively. Furthermore, at six months postoperatively, estimated effects were compatible with benefit and harm for all-cause mortality (OR 0.71, 95% CI 0.26 to 1.95), cardiovascular death (OR 0.73, 95% CI 0.23 to 2.39) and nonfatal cardiovascular events (OR 1.41, 95% CI 0.59 to 3.35). Adverse drug effects were reported for the whole study population and were not available for the subgroup of participants with AAA. We considered the study to be at a generally low risk of bias. We downgraded the quality of the evidence for all outcomes to low. We downgraded the quality of evidence for imprecision as only one study with a small number of participants was available, the number of events was small and the result was consistent with benefit and harm.

AUTHORS' CONCLUSIONS

Due to the limited number of included trials, there is insufficient evidence to draw any conclusions about the effectiveness of cardiovascular prophylaxis in reducing mortality and cardiovascular events in people with AAA. Further good-quality randomised controlled trials that examine many types of prophylaxis with long-term follow-up are required before firm conclusions can be made.

Perioperative β-Blockade in Noncardiac Surgery: A Cautionary Tale of Over-reliance on Small Randomized Prospective Trials

PURPOSE

Our aim was to analyze the current scientific literature relevant to the use of β-adrenergic receptor antagonists for the prevention of cardiovascular morbidity and mortality in patients undergoing noncardiac surgery.

METHODS

A PubMed search was conducted for the following concepts: pre- or perioperative, β-adrenergic receptor antagonist, treatment outcome, and cardiovascular complication. Randomized clinical trials measuring the effect of β-adrenergic blocking agents against that of placebo on cardiovascular outcomes after noncardiac surgery were included in the review.

FINDINGS

Two small randomized controlled trials published in 1996 and 1999 reported associations between perioperative β-blockade and significant reductions in long-term and 30-day cardiac mortality, respectively. These 2 studies prompted guideline changes in 2002 encouraging perioperative β-blockade in subsets of noncardiac surgery patients. However, subsequent trials failed to validate these results. In 2008, the first large randomized controlled trial on the topic was published and found an association between perioperative β-blockade and an increase in perioperative mortality. Furthermore, in 2011, the lead author of the 1999 study was dismissed from his academic position for scientific misconduct, casting doubt on the validity of guidelines based on his work. Existing studies are highly heterogeneous, making comparisons difficult. Current literature does not support initiating perioperative β-blockade in noncardiac surgery patients not already receiving these medications.

IMPLICATIONS

Future research on the topic should account for the influence individual genetic variation can have on outcomes and β-blocker metabolism. Additionally, the relationship between outcomes and the β-1 selectivity of different β-blockers should be explored.

ADRB2 gly16gly Genotype, Cardiac Output, and Cerebral Oxygenation in Patients Undergoing Anesthesia for Abdominal Aortic Aneurysm Surgery

BACKGROUND

Gly16arg polymorphism of the adrenergic β2-receptor is associated with the elevated cardiac output (Q) in healthy gly16-homozygotic subjects. We questioned whether this polymorphism also affects Q and regional cerebral oxygen saturation (SCO2) during anesthesia in vascular surgical patients.

METHODS

One hundred sixty-eight patients (age 71 ± 6 years) admitted for elective surgery were included. Cardiovascular variables were determined before and during anesthesia by intravascular pulse contour analysis (Nexfin) and SCO2 by cerebral oximetry (INVOS 5100C). Genotyping was performed with the TaqMan assay.

RESULTS

Before anesthesia, Q and SCO2 were 4.7 ± 1.2 L/min and 66% ± 8%, respectively, and linearly correlated (r = 0.35, P < .0001). In patients with the gly16gly genotype baseline, Q was approximately 0.4 L/min greater than in arg16 carriers (CI95: 0.0-0.8, Pt test = .03), but during anesthesia, the difference was 0.3 L/min (Pmixed-model = .07). Post hoc analysis revealed the change in SCO2 from baseline to the induction of anesthesia to be on average 2% greater in gly16gly homozygotes than in arg16 patients when adjusted for the change in Q (P = .03; CI95: 0.2-4.0%).

CONCLUSIONS

This study suggests that the β2-adrenoceptor gly16gly genotype is associated with the elevated resting Q. An interesting trend to greater frontal lobe oxygenation at induction of anesthesia in patients with gly16gly genotype was found, but because of insufficient sample size and lack of PCO2 control throughout the measurements, the presented data may only serve as the hypothesis generating for future studies. The confidence limits indicate that the magnitude of the effects may range from clinically insignificant to potentially important.

Current Approaches in Hip and Knee Arthroplasty Anaesthesia

Risk assesment, preoperative drug regulation, the anesthesia and analgesia techniques are very important and the effectivity on success of surgery is great. So, these topics in arthroplasty were reviewed under current knowledge.

Visual Complications in Patients with Biopsy-proven Giant Cell Arteritis: A Population-based Study

OBJECTIVE

To study the clinical and laboratory characteristics of patients with biopsy-proven giant cell arteritis (GCA) with visual complications, and to evaluate the incidence rate of visual complications in GCA compared to the background population.

METHODS

Data from 840 patients with GCA in the county of Skåne, Sweden, diagnosed between 1997 and 2010, were used for this analysis. Cases with visual complications were identified from a diagnosis registry and confirmed by a review of medical records. The rate of visual complications in patients with GCA was compared with an age- and sex-matched reference population.

RESULTS

There were 85 patients (10%) who developed ≥ 1 visual complication after the onset of GCA. Of the patients, 18 (21%) developed unilateral or bilateral complete visual loss. The mean age at diagnosis was 78 years (± 7.3); 69% were women. Compared with patients without visual complications, those with visual complication had lower C-reactive protein levels at diagnosis and were less likely to have headache, fever, and palpable abnormal temporal artery. The use of β-adrenergic inhibitors was associated with visual complications. The incidence of visual complications among patients with GCA was 20.9/1000 person-years of followup compared to 6.9/1000 person-years in the reference population, resulting in a rate ratio of 3.0 (95% CI 2.3-3.8).

CONCLUSION

Ten percent of patients with GCA developed visual complications, a rate substantially higher than that of the general population. Patients with GCA who had visual complications had lower inflammatory responses and were more likely to have been treated with β-adrenergic inhibitors compared with patients without visual complications.

Association between Intraoperative Hypotension and Myocardial Injury after Vascular Surgery

BACKGROUND

Postoperative myocardial injury occurs frequently after noncardiac surgery and is strongly associated with mortality. Intraoperative hypotension (IOH) is hypothesized to be a possible cause. The aim of this study was to determine the association between IOH and postoperative myocardial injury.

METHODS

This cohort study included 890 consecutive patients aged 60 yr or older undergoing vascular surgery from two university centers. The occurrence of myocardial injury was assessed by troponin measurements as part of a postoperative care protocol. IOH was defined by four different thresholds using either relative or absolute values of the mean arterial blood pressure based on previous studies. Either invasive or noninvasive blood pressure measurements were used. Poisson regression analysis was used to determine the association between IOH and postoperative myocardial injury, adjusted for potential clinical confounders and multiple comparisons.

RESULTS

Depending on the definition used, IOH occurred in 12 to 81% of the patients. Postoperative myocardial injury occurred in 131 (29%) patients with IOH as defined by a mean arterial pressure less than 60 mmHg, compared with 87 (20%) patients without IOH (P = 0.001). After adjustment for potential confounding factors including mean heart rates, a 40% decrease from the preinduction mean arterial blood pressure with a cumulative duration of more than 30 min was associated with postoperative myocardial injury (relative risk, 1.8; 99% CI, 1.2 to 2.6, P < 0.001). Shorter cumulative durations (less than 30 min) were not associated with myocardial injury. Postoperative myocardial infarction and death within 30 days occurred in 26 (6%) and 17 (4%) patients with IOH as defined by a mean arterial pressure less than 60 mmHg, compared with 12 (3%; P = 0.08) and 15 (3%; P = 0.77) patients without IOH, respectively.

CONCLUSIONS

In elderly vascular surgery patients, IOH defined as a 40% decrease from the preinduction mean arterial blood pressure with a cumulative duration of more than 30 min was associated with postoperative myocardial injury.

Effectiveness of platelet inhibition on major adverse cardiac events in non-cardiac surgery after percutaneous coronary intervention: a prospective cohort study

BACKGROUND

Platelet inhibition is mandatory therapy after percutaneous coronary intervention (PCI). Withdrawal of oral antiplatelet agents has been linked to increased incidence of postoperative adverse cardiac events in post-PCI patients having non-cardiac surgery (NCS). There is limited knowledge of temporal changes in platelet inhibition in this high-risk surgical population. We therefore performed a multicentre prospective cohort study evaluating perioperative platelet function and its association with postoperative major adverse cardiac events (MACE).

METHODS

In 201 post-PCI patients having NCS, we assessed the association between platelet function and postoperative MACE. We performed perioperative platelet function testing using a platelet mapping assay (PMA). Troponin-I was measured every 8 h for 2 days, then daily until day 5. Myocardial infarction was assessed using the third universal definition. We used multivariable logistic regression to assess the association between platelet inhibition and MACE.

RESULTS

Major adverse cardiac events occurred in 40 patients within 30 days of surgery. Thirty-two of these events were non-ST-elevation myocardial infarction, four ST-elevation myocardial infarction, and four exacerbation of congestive heart failure. We were unable to show an association between platelet inhibition and MACE. The PMA showed declining levels of platelet inhibition the longer the antiplatelet therapy was withheld before surgery. Logistic regression did not show an association between preoperative platelet function or the type of stent and MACE. We found an increased cardiac risk of MACE after surgery within 6 weeks of PCI.

CONCLUSIONS

The incidence of MACE in patients undergoing NCS after previous PCI is high in spite of adequate perioperative antiplatelet therapy.

CLINICAL TRIAL REGISTRATION

NCT 01707459 (registered at http://www.clinicaltrials.gov).

Perioperative stroke

PURPOSE

Perioperative stroke is associated with significant morbidity and mortality, with an incidence that may be underappreciated. In this review, we examine the significance, pathophysiology, risk factors, and evidence-based recommendations for the prevention and management of perioperative stroke.

SOURCE

This is a narrative review based on literature from the PubMed database regarding perioperative stroke across a broad surgical population. The Society for Neuroscience in Anesthesiology and Critical Care recently published evidence-based recommendations for perioperative management of patients at high risk for stroke; these recommendations were analyzed and incorporated into this review.

PRINCIPAL FINDINGS

The incidence of overt perioperative stroke is highest in patients presenting for cardiac and major vascular surgery, although preliminary data suggest that the incidence of covert stroke may be as high as 10% in non-cardiac surgery patients. The pathophysiology of perioperative stroke involves different pathways. Thrombotic stroke can result from increased inflammation and hypercoagulability; cardioembolic stroke can result from disease states such as atrial fibrillation, and tissue hypoxia from anemia can result from the combination of anemia and beta-blockade. Across large-scale database studies, common risk factors for perioperative stroke include advanced age, history of cerebrovascular disease, ischemic heart disease, congestive heart failure, atrial fibrillation, and renal disease. Recommendations for prevention and management of perioperative stroke are evolving, though further work is needed to clarify the role of proposed modifiable risk factors such as perioperative anticoagulation, antiplatelet therapy, appropriate transfusion thresholds, and perioperative beta-blockade.

CONCLUSIONS

Perioperative stroke carries a significant clinical burden. The incidence of perioperative stroke may be higher than previously recognized, and there are diverse pathophysiologic mechanisms. There are many opportunities for further investigation of the pathophysiology, prevention, and management of perioperative stroke.

Universal tranexamic acid therapy to minimize transfusion for major joint arthroplasty: a retrospective analysis of protocol implementation

PURPOSE

Tranexamic acid (TXA) therapy can reduce red blood cell (RBC) transfusion; however, this therapy remains underutilized in many surgical patient populations. We assessed whether implementation of a protocol to facilitate universal administration of TXA in patients undergoing total hip or knee arthroplasty would reduce the incidence of RBC transfusion without increasing adverse clinical outcomes.

METHODS

We implemented a quality of care policy to provide universal administration of intravenous TXA at a dose of 20 mg·kg(-1) iv to all eligible patients undergoing total hip or knee arthroplasty from October 21, 2013 to April 30, 2014. We compared data from an equal number of patients before and after protocol implementation (n = 422 per group). The primary outcome was RBC transfusion with secondary outcomes including postoperative hemoglobin concentration (Hb) and length of hospital stay. Adverse events were identified from the electronic medical records. Data were analyzed by a Chi square test and adjusted logistic and linear regression analysis.

RESULTS

Implementation of the protocol resulted in an increase in TXA utilization from 45.8% to 95.3% [change 49.5%; 95% confidence interval (CI), 44.1 to 54.5; P < 0.001]. This change was associated with a reduction in the rate of RBC transfusion from 8.8% to 5.2%, (change -3.6%; 95% CI, -0.1 to -7.0; P = 0.043). Pre- and post-protocol mean [standard deviation (SD)] Hb values were similar, including the nadir Hb prior to RBC transfusion [72 (8) g·L(-1) vs 70 (8) g·L(-1), respectively; mean difference -1 g·L(-1); 95% CI, -3 to 5; P = 0.569]. Length of stay was not altered, and no increase in adverse events was observed.

CONCLUSIONS

Implementation of a perioperative TXA protocol was associated with both an increase in TXA use and a reduction in RBC transfusion following hip or knee arthroplasty. Adverse events and length of hospital stay were not influenced by the protocol.