Best practice & research. Clinical anaesthesiology
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Since its inception, the pulmonary artery catheter has enjoyed widespread use in both medical and surgical critically ill patients. It has also endured criticism and skepticism about its benefit in these patient populations. By providing information such as cardiac output, mixed venous oxygen saturation, and intracardiac pressures, the pulmonary artery catheter may improve care of the most complex critically ill patients in the intensive care unit and the operating room. ⋯ Major complications related to catheter placement are infrequent, but misinterpretation of monitored data is not uncommon and has led many to question the utility of the pulmonary artery catheter. The evidence to date suggests that the use of the catheter does not change mortality in many critically ill patients and may expose these patients to a higher rate of complications. However, additional clinical trials are needed, particularly in the most complex critically ill patients, who have generally been excluded from many of the research trials performed to date.
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Early detection and rapid treatment of tissue hypoxia are important goals. Venous oxygen saturation is an indirect index of global oxygen supply-to-demand ratio. Central venous oxygen saturation (ScvO2) measurement has become a surrogate for mixed venous oxygen saturation (SvO2). ⋯ After results from a single-center study suggested that maintaining ScvO2 values >70% might improve survival rates in septic patients, international practice guidelines included this target in a bundle strategy to treat early sepsis. However, a recent multicenter study with >1500 patients found that the use of central hemodynamic and ScvO2 monitoring did not improve long-term survival when compared to the clinical assessment of the adequacy of circulation. It seems that if sepsis is recognized early, a rapid initiation of antibiotics and adequate fluid resuscitation are more important than measuring venous oxygen saturation.
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Echocardiography has become an indispensable tool in the evaluation of medical and surgical patients. As ultrasound (US) machines have become more widely available and significantly more compact, there has been an exponential growth in the use of transthoracic echocardiography (TTE), transoesophageal echocardiography (TOE) and other devices in the perioperative setting. Here, we review recent findings relevant to the use of perioperative US, with a special focus on the haemodynamic management of the surgical patient.
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The photoplethysmographic (PPG) waveform, also known as the pulse oximeter waveform, is one of the most commonly displayed clinical waveforms. First described in the 1930s, the technology behind the waveform is simple. The waveform, as displayed on the modern pulse oximeter, is an amplified and highly filtered measurement of light absorption by the local tissue over time. ⋯ Research efforts are under way to analyze the PPG using improved digital signal processing methods to develop new physiologic parameters. It is hoped that when these new physiologic parameters are combined with a more modern understanding of cardiovascular physiology (functional hemodynamics) the potential utility of the PPG will be expanded. The clinical researcher's objective is the use of the PPG to guide early goal-directed therapeutic interventions (fluid, vasopressors, and inotropes), in effect to extract from the simple PPG the information and therapeutic guidance that was previously only obtainable from an arterial pressure line and the pulmonary artery catheter.