Best practice & research. Clinical anaesthesiology
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Perioperative anaemia is a common clinical entity. It is usually due to combination of various mechanisms, including: pre-existing anaemia prior to surgery; anaemia due to impaired erythropoiesis, including alterations of metabolism of iron and erythropoietin (EPO); anaemia due to increased destruction of red blood cells (RBCs); and anaemia due to iatrogenic causes. ⋯ Iatrogenic causes, notably excessive phlebotomies, remain a major cause of perioperative anaemia. With increasing emphasis on restrictive blood transfusion strategies, understanding these mechanisms is important for the clinician.
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Best Pract Res Clin Anaesthesiol · Dec 2012
ReviewEffects of perioperative fasting on haemodynamics and intravascular volumes.
Maintaining cardiac preload throughout the perioperative period is a generally accepted target. As perioperative fasting is believed to cause intravascular hypovolaemia it traditionally triggers aggressive preemptive intravenous fluid infusion. Physiology suggests that extracellular losses via urinary output and evaporation decrease the extracellular compartment. ⋯ Nevertheless, an intravenous colloid challenge can increase stroke volume after induction of anaesthesia in the majority of surgical patients. While perioperative stroke volume maximisation in high-risk surgery probably improves outcome, the implication of this observation for the routine patient remains unclear. It appears as though there are two important targets to preserve cardiac preload: normovolaemia and vasotension.
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Best Pract Res Clin Anaesthesiol · Dec 2012
ReviewImpact of intravascular volume replacement and transfusion on outcome: where are we now?
Intravenous fluid administration is often required to counteract haemodynamic instability during emergency and elective surgeries, as well as in the intensive care unit. However, the best type and the amount of fluid required are controversial. A recent meta-analysis suggested that there is no difference among different types of colloids on outcome. ⋯ Nevertheless, the macrocirculation and clinical parameters have to be considered as well. Given that red blood cells remain the most important oxygen carriers, recent evidence regarding blood age may stimulate new studies according to the actual range for blood storage. Artificial oxygen carriers may play a role in specific situations, where the transfusion is indicated but the access to blood is problematic, but there is doubt that they may replace blood transfusion.
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Hemodynamic monitoring is the cornerstone of perioperative anesthetic monitoring. In the unconscious patient, hemodynamic monitoring not only provides information relating to cardiac output, volume status and ultimately tissue perfusion, but also indicates depth of anesthesia and adequacy of pain control. ⋯ No single device provides a complete assessment of hemodynamic status, and the use of all devices in every situation is neither practical nor appropriate. This article aims to provide the reader with an overview of the devices currently available, and the information they provide, to assist anesthesiologists in the selection of the most appropriate devices for any given situation.
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Anemia is associated with perioperative mortality and morbidity. Since the presence of anemia and blood transfusion often go hand in hand, it can be difficult to separate the effects of anemia from the effects of perioperative transfusion. The role for blood transfusion in mitigating the mortality and morbidity associated with anemia is unclear. ⋯ Further research is warranted in patients with the acute coronary syndrome, as there is insufficient evidence to make recommendations for this patient population. Additional multi-center randomized controlled trials need to be conducted in perioperative and critically ill patients with large enough sample sizes to examine differences in mortality and major complications between liberal and restrictive transfusion strategies. Further trials need to incorporate current practices in improved blood storage and leukoreduction techniques.