The influence of labetalol on arterial blood gas data, pulmonary haemodynamics and pulmonary shunting

Beta-blocker treatment in the critically ill: a systematic review and meta-analysis

BACKGROUND

Critical illness may lead to activation of the sympathetic system. The sympathetic stimulation may be further increased by exogenous catecholamines, such as vasopressors and inotropes. Excessive adrenergic stress has been associated with organ dysfunction and higher mortality. β-Blockers may reduce the adrenergic burden, but they may also compromise perfusion to vital organs thus worsening organ dysfunction. To assess the effect of treatment with β-blockers in critically ill adults, we conducted a systematic review and meta-analysis of randomized controlled trials.

MATERIALS AND METHODS

We conducted a search from three major databases: Ovid Medline, the Cochrane Central Register for Controlled Trials and Scopus database. Two independent reviewers screened, selected, and assessed the included articles according to prespecified eligibility criteria. We assessed risk of bias of eligible articles according to the Cochrane guidelines. Quality of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

RESULTS

Sixteen randomized controlled trials comprising 2410 critically ill patients were included in the final review. A meta-analysis of 11 trials including 2103 patients showed a significant reduction in mortality in patients treated with β-blockers compared to control (risk ratio 0.65, 95%CI 0.53-0.79; p < .0001). There was no significant difference in mean arterial pressure or vasopressor load. Quality of life, biventricular ejection fraction, blood lactate levels, cardiac biomarkers and mitochondrial function could not be included in meta-analysis due to heterogenous reporting of outcomes.

CONCLUSIONS

In this systematic review we found that β-blocker treatment reduced mortality in critical illness. Use of β-blockers in critical illness thus appears safe after initial hemodynamic stabilization. High-quality RCT's are needed to answer the questions concerning optimal target group of patients, timing of β-blocker treatment, choice of β-blocker, and choice of physiological and hemodynamic parameters to target during β-blocker treatment in critical illness.KEY MESSAGESA potential outcome benefit of β-blocker treatment in critical illness exists according to the current review and meta-analysis. Administration of β-blockers to resuscitated patients in the ICU seems safe in terms of hemodynamic stability and outcome, even during concomitant vasopressor administration. However, further studies, preferably large RCTs on β-blocker treatment in the critically ill are needed to answer the questions concerning timing and choice of β-blocker, patient selection, and optimal hemodynamic targets.

The role of serotonin blockers in cardiac anesthesia

In the complex setting of cardiac surgery and cardiopulmonary bypass, several potent mediators are released that by interacting may cause clinical syndromes like coronary ischemia, systemic hypertension, pulmonary hypertension, and renal failure. One of the mediators is serotonin, released from aggregating platelets, and causing vasoconstriction by activating S2-serotonergic receptors, particularly in patients with an impaired endothelial function, as in atherosclerosis. The most important available specific S2-serotonergic receptor antagonist is ketanserin. If administered during or after cardiac surgery, ketanserin lowers systemic and pulmonary blood pressure, and improves peripheral and pulmonary perfusion without causing reflex tachycardia or an increase in pulmonary shunt fraction.

Labetalol attenuates the negative effects of deliberate hypotension induced by isoflurane

The effect of labetalol on deliberate hypotension was studied in 24 adult patients undergoing middle-ear surgery. Hypotension was induced in Group I (12 patients) with isoflurane 3.0 vol% in inspiratory gas, and in Group II (12 patients) with labetalol 0.5 mg.kg-1 i.v., in addition to isoflurane. The induction time of hypotension was 4.9 +/- 1.0 (s.e.mean) min in Group I, and 1.8 +/- 0.2 min in Group II (P less than 0.01). The mean isoflurane concentration in inspiratory gas for the maintenance of hypotension was 1.4 +/- 0.2 vol% in Group I, and 0.7 +/- 0.1 vol% in Group II (P less than 0.01). There were no differences in urine flow rates (UF) between the groups during any phase, though UF decreased in Group I from the prehypotensive value 0.58 +/- 0.12 ml.min-1 to 0.07 +/- 0.02 ml.min-1 during hypotension (P less than 0.01) and increased to 1.28 +/- 0.17 ml.min-1 after anaesthesia (P less than 0.05). UF in Group II were 0.56 +/- 0.17, 0.25 +/- 0.10 and 0.56 +/- 0.06 ml.min-1, respectively. Creatinine clearances per 1.73 m2 body surface area (CCreat) in Group I were 78 +/- 14 ml.min-1, and in Group II 78 +/- 11 ml.min-1 before hypotension. During hypotension, CCreat were lower in Group I (8 +/- 1 ml.min-1) than in Group II (33 +/- 8 ml.min-1) (P less than 0.01). After anaesthesia, there was no difference in CCreat between the groups (Group I: 110 +/- 17 ml.min-1 and Group II: 120 +/- 17 ml.min-1).(ABSTRACT TRUNCATED AT 250 WORDS)