Beta-blockers in intensive care medicine: potential benefit in acute brain injury and acute respiratory distress syndrome.

Sympathetic activation is a well-known phenomenon after acute brain injury and in critical illness. In this review we describe pathophysiological considerations that may help in elucidating the potential role of beta (ß)-adrenergic antagonists to block some of the adverse sympathetic effects in acute brain injury (subarachnoid hemorrhage and traumatic brain injury) and the acute respiratory distress syndrome. In acute brain injury cardiac dysfunction has been studied most extensively but its pathophysiology is only partly elucidated in man. Further, several adverse consequences of sympathetic activation on the brain itself may occur. Clinical and preclinical studies are described in this review that lend support to the idea that ß blockers may have beneficial effects on both cardiac, cerebral and other adverse consequences of sympathetic overactivation after acute brain injury. Second, the acute respiratory distress syndrome (ARDS) may also respond to ß blocker therapy, albeit through a different mechanism than in acute brain injury. Some studies reported on beneficial effects of these drugs on ARDS through the mitigation of pulmonary blood flow, without a decrease in systemic hemodynamics. However, in both acute brain injury and ARDS further studies are needed to distinguish those patients who are most likely to benefit from ß blockers from those more likely to be harmed by them. Furthermore, recent patents of ß blockers relevant to the content of this paper are referenced.

Intra-operative assessment of human pulmonary alveoli in vivo using Sidestream Dark Field imaging: a feasibility study.

BACKGROUND: In vivo videomicroscopy has been used for years to visualize subpleural alveoli in animal studies. This has led to a better understanding of alveolar physiology. We tested the hypothesis whether a novel handheld videomicroscope could be used for intraoperative detection of alveoli in surgical patients during mechanical ventilation. MATERIAL/METHODS: Using Sidestream Dark Field imaging, we observed 6 patients (3 adults and 3 children) who underwent elective cardiac surgery. In each patient, the tip of the microscope was placed on the visceral pleural surface of the left upper pulmonary lobe after weaning from cardiopulmonary bypass. The acquired images were converted into digital signals and captured on a computer. RESULTS: Although cardiac motion artifacts were present, visceral pleural microvascular blood flow could be observed in adults and infants. In infants, sub-pleural cavities (alveoli) were observed. These alveoli were remarkably similar in dimension and structure to those identified previously as true alveoli in animal studies. Quantification of these alveoli demonstrated that mean alveolar diameter, perimeter and area increased with age among the investigated infants (all parameters p<0.001). CONCLUSIONS: High-quality images of visceral pleural microvessels as well as subpleural cavities, reflecting superficial alveoli, could be obtained in infants. These findings create the opportunity to begin human intervention studies, which should investigate alveolar dynamics during mechanical ventilation in cardio-thoracic surgery in more detail.

Volume of activity and occupancy rate in intensive care units. Association with mortality.

OBJECTIVE: Mortality after many procedures is lower in centers where more procedures are done. It is controversial whether this is true for intensive care units, too. We examined the relationship between the volume of activity of intensive care units (ICUs) and mortality by a measure of risk-adjusted volume of activity specific for ICUs. DESIGN: Prospective, multicenter, observational study. SETTING: Eighty-nine ICUs in 12 European countries. PATIENTS: During a 4-month study period, 12,615 patients were enrolled. INTERVENTIONS: Demographic and clinical statistics, severity at admission and a score of nursing complexity and workload were collected. RESULTS: Total volume of activity was defined as the number of patients admitted per bed per year, high-risk volume as the number of high-risk patients admitted per bed per year (selected combining of length of stay and severity of illness). A multi-step risk-adjustment process was planned. ICU volume corresponding both to overall [odds ratio (OR) 0.966] and 3,838 high-risk (OR 0.830) patients was negatively correlated with mortality. Relative mortality decreased by 3.4 and 17.0% for every five extra patients treated per bed per year in overall volume and high-risk volume, respectively. A direct relationship was found between mortality and the ICU occupancy rate (OR 1.324 and 1.351, respectively). CONCLUSIONS: Intensive care patients, whatever their level of risk, are best treated where more high-risk patients are treated. Moreover, the higher the ICU occupancy rate, the higher is the mortality.