24 Oct 07
Posted in Acid-Base disorders, Sepsis at 18:02 by Laci
By E O’Dell, SM Tibby, A Durward, I A Murdoch
Critical Care Medicine 2007;35:2390-2394
Metabolic acidosis is common in septic shock, yet few data exist on its etiological temporal profile during resuscitation; this is partly due to limitations in bedside monitoring tools (base excess, anion gap). Accurate identification of the type of acidosis is vital, as many therapies used in resuscitation can themselves produce metabolic acidosis.
Design
Retrospective, cohort study.
Setting
Multidisciplinary pediatric intensive care unit with 20 beds.
Patients
A total of 81 children with meningococcal septic shock.
Interventions
None.
Measurements and Results
Acid-base data were collected retrospectively on 81 children with meningococcal septic shock (mortality, 7.4%) for the 48 hrs after presentation to the hospital. Base excess was partitioned using abridged Stewart equations, thereby quantifying the three predominant influences on acid-base balance: sodium chloride, albumin, and unmeasured anions (including lactate). Metabolic acidosis was common at presentation (mean base excess, -9.7 mmol/L) and persisted for 48 hrs. However, the pathophysiology changed dramatically from one of unmeasured anions at admission (mean unmeasured anion base excess, -9.2 mmol/L) to predominant hyperchloremia by 8-12 hrs (mean sodium-chloride base excess, -10.0 mmol/L). Development of hyperchloremic acidosis was associated with the amount of chloride received during intravenous fluid resuscitation (r2 = .44), with the base excess changing, on average, by -0.4 mmol/L for each millimole per kilogram of chloride administered. Hyperchloremic acidosis resolved faster in patients who 1) manifested larger (more negative) sodium chloride-partitioned base excess, 2) maintained a greater urine output, and 3) received furosemide; and slower in those with high blood concentrations of unmeasured anions (all, p < .05).
Conclusions
Hyperchloremic acidosis is common and substantial after resuscitation for meningococcal septic shock. Recognition of this entity may prevent unnecessary and potentially harmful prolonged resuscitation.
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Posted in Acid-Base disorders, Sepsis at 18:01 by Laci
By H Morimatsu
Critical Care Medicine 2007;35:2456-2457
Fluid resuscitation is a vital part of critical care. We use massive amounts of fluids in our daily critical care practice. Almost all of these fluids contain strong ions (such as sodium and chloride) and, sometimes, weak acids (such as albumin). Thus, it is easy to imagine that massive fluid resuscitation can result in metabolic changes that alter a patient’s acid-base status. Saline-induced metabolic acidosis has been well described; it has been explained by so-called dilution of the bicarbonate concentration. Recently, however, the Stewart methodology has been applied to critical care medicine; it has revealed that this acidosis is primarily due to a decreased strong ion difference (SID) induced by hyperchloremia.
According to Stewart’s concept, neither bicarbonate nor hydrogen ion is an independent determinant of the acid-base status, whereas strong ion difference and total weak acid (ATOT) are independent variables. Thus, the balance between strong ions and weak acids, including albumin, phosphate, and unmeasured anions, plays an important role in acid-base physiology. Using this methodology, studies have shown that metabolic acid-base disorders have a complex etiology, which could not be previously understood using bicarbonate-oriented methodology.
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Posted in Acid-Base disorders, Sepsis at 17:57 by Laci
By E O’Dell, SM Tibby, A Durward, I A Murdoch
Critical Care Medicine 2007;35:2390-2394
Metabolic acidosis is common in septic shock, yet few data exist on its etiological temporal profile during resuscitation; this is partly due to limitations in bedside monitoring tools (base excess, anion gap). Accurate identification of the type of acidosis is vital, as many therapies used in resuscitation can themselves produce metabolic acidosis.
Design
Retrospective, cohort study.
Setting
Multidisciplinary pediatric intensive care unit with 20 beds.
Patients
A total of 81 children with meningococcal septic shock.
Interventions
None.
Measurements and Results
Acid-base data were collected retrospectively on 81 children with meningococcal septic shock (mortality, 7.4%) for the 48 hrs after presentation to the hospital. Base excess was partitioned using abridged Stewart equations, thereby quantifying the three predominant influences on acid-base balance: sodium chloride, albumin, and unmeasured anions (including lactate). Metabolic acidosis was common at presentation (mean base excess, -9.7 mmol/L) and persisted for 48 hrs. However, the pathophysiology changed dramatically from one of unmeasured anions at admission (mean unmeasured anion base excess, -9.2 mmol/L) to predominant hyperchloremia by 8-12 hrs (mean sodium-chloride base excess, -10.0 mmol/L). Development of hyperchloremic acidosis was associated with the amount of chloride received during intravenous fluid resuscitation (r2 = .44), with the base excess changing, on average, by -0.4 mmol/L for each millimole per kilogram of chloride administered. Hyperchloremic acidosis resolved faster in patients who 1) manifested larger (more negative) sodium chloride-partitioned base excess, 2) maintained a greater urine output, and 3) received furosemide; and slower in those with high blood concentrations of unmeasured anions (all, p < .05).
Conclusions
Hyperchloremic acidosis is common and substantial after resuscitation for meningococcal septic shock. Recognition of this entity may prevent unnecessary and potentially harmful prolonged resuscitation.
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Posted in Anesthesia, Pre-operatie evaluation at 17:51 by Laci
By Magdy Selim
N Engl J Med 2007;356:706-713
Stroke is one of the most feared complications of surgery. to provide adequate preventive and therapeutic measures, physicians need to be knowledgeable about the risk factors for stroke during the perioperative period. In this article, I review the pathophysiology of perioperative stroke and provide recommendations for the stratification of risk and the management of risk factors.
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