Best practice & research. Clinical anaesthesiology
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Hypovolaemia is a common cause of circulatory failure in the perioperative period. However, only 50% of critically ill patients respond to volume expansion with an adequate increase in cardiac output. ⋯ The concept of fluid responsiveness has been recognized for more than 20 years, and several studies have shown the superiority of these dynamic variables compared to static filling pressures. However, the usefulness of dynamic variables in critically ill patients is limited by several factors that the clinician needs to know for proper interpretation.
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Best Pract Res Clin Anaesthesiol · Jun 2009
ReviewRelevance of non-albumin colloids in intensive care medicine.
Current guidelines on initial haemodynamic stabilization in shock states suggest infusion of either natural or artificial colloids or crystalloids. However, as the volume of distribution is much larger for crystalloids than for colloids, resuscitation with crystalloids alone requires more fluid and results in more oedema, and may thus be inferior to combination therapy with colloids. This chapter describes the currently available synthetic colloid solutions [i.e., dextran, gelatin and hydroxyethyl starch (HES)] in detail, and critically discusses their specific effects including potential adverse effects. ⋯ When considering the efficacy and risk/benefit profile of synthetic colloids, modern tetrastarches appear to be most suitable for intensive care medicine, given their high volume effect, low anaphylactic potential and predictable pharmacokinetics. However, the impact of tetrastarch solutions on mortality and renal function in septic patients has not been fully determined, and further comparison with crystalloids in prospective, randomized studies is required. Such studies are currently ongoing and their results should be awaited before drawing final conclusions on the HES preparations.
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Best Pract Res Clin Anaesthesiol · Jun 2009
ReviewIsotonic and hypertonic crystalloid solutions in the critically ill.
Disorders of fluid and electrolyte balance in the critically ill are volume-related, compositional, or both. Targeting 'normal' values for plasma volume, osmolality and electrolytes might not be optimal in conditions as diverse as intracranial trauma/haemorrhage, hepatic encephalopathy, abdominal hypertension, or major surgery, because a hyperosmolar state seems to favourably affect tissue (brain and intestinal) oedema formation. ⋯ Crystalloid resuscitation is superior to vasopressors in shock associated with blunt trauma, and is at least not inferior to colloids in septic shock. Traditional rules of thumb indicating the need for three to four times the amount of crystalloids for the plasma volume to be replaced are probably erroneous and might have contributed to association of overly aggressive crystalloid resuscitation with poor outcome.
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Peri-operative fluid therapy continues to be an exercise in empiricism, with nagging questions about efficacy and complications. Pharmacokinetics is used for studying the time dependency of administered drugs. ⋯ This could possibly allow for more rational design of intravenous fluid paradigms to improve clinical fluid therapy. This chapter briefly summarizes currently accepted principles of fluid therapy, discusses the general approach to kinetic analysis of fluid therapy, reviews currently available data defining kinetic responses to fluid therapy, and speculates about future applications of this approach.