Donald E. Griesdale

Clinical review: Guyton--the role of mean circulatory filling pressure and right atrial pressure in controlling cardiac output.

Arthur Guytons concepts of the determinative role of right heart filling in cardiac output continue to be controversial. This paper reviews his seminal experiments in detail and clarifies the often confusing concepts underpinning his model. One primary criticism of Guytons model is that the parameters describing venous return had not been measured in a functioning cardiovascular system in humans. Thus, concerns have been expressed in regard to the ability of Guytons simplistic model, with few parameters, to model the complex human circulation. Further concerns have been raised in regard to the artificial experimental preparations that Guyton used. Recently reported measurements in humans support Guytons theoretical and animal work.

Effect of early achievement of physiologic resuscitation goals in septic patients admitted from the ward on the kidneys.

PURPOSE The aim of the study was to evaluate if early achievement of physiologic goals of resuscitation in critically ill septic patients admitted from the ward may prevent acute kidney injury (AKI). MATERIALS AND METHODS Patients admitted to the intensive care unit (ICU) with a diagnosis of sepsis were retrospectively identified. Mean arterial pressure greater than 65 mm Hg, central venous pressure greater than 8 mm Hg, and central venous oxygenation greater than 70% achieved within 6 hours after ICU consultation at the ward was considered early achievement. Acute kidney injury was defined by the RIFLE criteria. RESULTS Of 85 patients, 29% achieved all goals within 6 hours, 42% had late or no achievement of goals, and 28% had incomplete documentation of goals. Of these, 52% developed AKI. Patients who eventually developed AKI had a significantly higher creatinine level at ICU consultation before resuscitation. Delay in achievement of goals results in a 3.4% creatinine level rise per hour in multivariate analysis (P = .03). The development of AKI was significantly influenced by delayed achievement of physiologic goals on the ICU (P = .02). CONCLUSIONS Although most of AKI occurred before ICU consultation, early physiologic resuscitation and achievement of hemodynamic goals on the ICU is associated with a decrease in development of AKI of septic patients admitted from the ward.

Individualized perfusion targets in hypoxic ischemic brain injury after cardiac arrest

Secondary injury is a major determinant of outcome in hypoxic ischemic brain injury (HIBI) after cardiac arrest and may be mitigated by optimizing cerebral oxygen delivery (CDO2). CDO2 is determined by cerebral blood flow (CBF), which is dependent upon mean arterial pressure (MAP). In health, CBF remains constant over the MAP range through cerebral autoregulation. In HIBI, the zone of intact cerebral autoregulation is narrowed and varies for each patient. Maintaining MAP within the intact autoregulation zone may mitigate ischemia, hyperemia and secondary injury. The optimal MAP in individual patients can be determined using real time autoregulation monitoring techniques.