Reliability of delivered dialysate sodium concentration

BACKGROUND: The results of studies investigating the effects of hyponatraemic dialysates have been mixed, with some reporting positive effects including reduction in blood pressure and inter-dialytic weight gains, whereas others have not been able to demonstrate any effect. These studies assume that setting a lower dialysate sodium results in the delivery of a hyponatraemic dialysate. We therefore measured delivered sodium to determine reliability. METHODS: We measured dialysate sodium in 10 BBraun Dialog+® and 6 Fresenius 4008H dialysis machines, which had been set up to deliver a sodium of 136 mmol/L, using flame photometry and indirect ion selective electrode (ISE) methods. RESULTS: Dialysate conductivity was 13.85 ± 0.05 mS/cm, but dialysate sodium measured by flame photometry was 141.8 ± 2.9 mmol/L, and 142.5 ± 2.4 mmol/L by ISE. Both dialysis machines delivered a dialysate sodium in excess of the 136 mmol/L set, with a mean bias of 7.0 ±2.1 mmol/L for the Dialog+®, and 3.7 ± 2.6 for the 4008 with the flame photometer method, and a mean bias of 6.3 ± 1.3 mmol/L for the Dialog+®, and 6.8 ± 3.7 for the 4008 by ISE. CONCLUSION: It is assumed when setting a dialysate sodium concentration that this sodium concentration is delivered. However we found that the dialysate sodium concentration delivered was greater than that set, despite the dialysis machines reporting a conductivity measurement in keeping with a lower sodium dialysate. Trials of lowered dialysate sodium therefore need to measure dialysate sodium concentrations to ensure what has been set is delivered

The anion study: effect of different crystalloid solutions on acid base balance, physiology, and survival in a rodent model of acute isovolaemic haemodilution

Background: Commercially available crystalloid solutions used for volume replacement do not exactly match the balance of electrolytes found in plasma. Large volume administration may lead to electrolyte imbalance and potential harm. We hypothesised that haemodilution using solutions containing different anions would result in diverse biochemical effects, particularly on acid-base status, and different outcomes. Methods: Anaesthetised, fluid-resuscitated, male Wistar rats underwent isovolaemic haemodilution by removal of 10% blood volume every 15 min, followed by replacement with one of three crystalloid solutions based on acetate, lactate, or chloride. Fluids were administered in a protocolised manner to achieve euvolaemia based on echocardiography-derived left ventrical volumetric measures. Removed blood was sampled for plasma ions, acid-base status, haemoglobin, and glucose. This cycle was repeated at 15-min intervals until death. The primary endpoint was change in plasma bicarbonate within each fluid group. Secondary endpoints included time to death and cardiac function. Results: During haemodilution, chloride-treated rats showed significantly greater decreases in plasma bicarbonate and strong ion difference levels compared with acetate- and lactate-treated rats. Time to death, total volume of fluid administered: chloride group 56 (3) ml, lactate group 62 (3) ml, and acetate group 65 (3) ml; haemodynamic and tissue oxygenation changes were, however, similar between groups. Conclusions: With progressive haemodilution, resuscitation with a chloride-based solution induced more acidosis compared with lactate- and acetate-based solutions, but outcomes were similar. No short-term impact was seen from hyperchloraemia in this model

A prolonged run-in period of standard subcutaneous microdialysis ameliorates quality of interstitial glucose signal in patients after major cardiac surgery

We evaluated a standard subcutaneous microdialysis technique for glucose monitoring in two critically ill patient populations and tested whether a prolonged run-in period improves the quality of the interstitial glucose signal. 20 surgical patients after major cardiac surgery (APACHE II score: 10.1 ± 3.2) and 10 medical patients with severe sepsis (APACHE II score: 31.1 ± 4.3) were included in this investigation. A microdialysis catheter was inserted in the subcutaneous adipose tissue of the abdominal region. Interstitial fluid and arterial blood were sampled in hourly intervals to analyse glucose concentrations. Subcutaneous adipose tissue glucose was prospectively calibrated to reference arterial blood either at hour 1 or at hour 6. Median absolute relative difference of glucose (MARD), calibrated at hour 6 (6.2 (2.6; 12.4) %) versus hour 1 (9.9 (4.2; 17.9) %) after catheter insertion indicated a significant improvement in signal quality in patients after major cardiac surgery (p < 0.001). Prolonged run-in period revealed no significant improvement in patients with severe sepsis, but the number of extreme deviations from the blood plasma values could be reduced. Improved concurrence of glucose readings via a 6-hour run-in period could only be achieved in patients after major cardiac surgery

Consensus on circulatory shock and hemodynamic monitoring. Task force of the European Society of Intensive Care Medicine.

OBJECTIVE: Circulatory shock is a life-threatening syndrome resulting in multiorgan failure and a high mortality rate. The aim of this consensus is to provide support to the bedside clinician regarding the diagnosis, management and monitoring of shock. METHODS: The European Society of Intensive Care Medicine invited 12 experts to form a Task Force to update a previous consensus (Antonelli et al.: Intensive Care Med 33:575-590, 2007). The same five questions addressed in the earlier consensus were used as the outline for the literature search and review, with the aim of the Task Force to produce statements based on the available literature and evidence. These questions were: (1) What are the epidemiologic and pathophysiologic features of shock in the intensive care unit ? (2) Should we monitor preload and fluid responsiveness in shock ? (3) How and when should we monitor stroke volume or cardiac output in shock ? (4) What markers of the regional and microcirculation can be monitored, and how can cellular function be assessed in shock ? (5) What is the evidence for using hemodynamic monitoring to direct therapy in shock ? Four types of statements were used: definition, recommendation, best practice and statement of fact. RESULTS: Forty-four statements were made. The main new statements include: (1) statements on individualizing blood pressure targets; (2) statements on the assessment and prediction of fluid responsiveness; (3) statements on the use of echocardiography and hemodynamic monitoring. CONCLUSIONS: This consensus provides 44 statements that can be used at the bedside to diagnose, treat and monitor patients with shock

NADH monitoring in shock states

Shock is defined as inadequate delivery or utilization of oxygen by the body tissues. Currently measured cardiorespiratory variables however, indicate decompensation only when patients become (near) shocked. Belated intervention often fails to reverse injury, leading to organ dysfunction and failure. Precise monitoring of the adequacy of tissue perfusion thus represents a major deficiency in clinical practice, particularly in the critically ill. As mitochondria utilize >90% of the oxygen consumed by the body, predominantly for ATP production, there is an obvious logic in targeting this organelle for monitoring the adequacy of tissue perfusion. Within mitochondria, NADH transfers electrons from the Krebs’ cycle to Complex I of the electron transport chain. In doing so, NADH is oxidized to NAD+. A rise in NADH:NAD+ ratio (redox state) will occur with a downstream block in the chain, e.g. due to lack of oxygen. As NADH (but not NAD+) fluoresces in response to UV light excitation (340nm), with an intensity relating to its concentration, and as most of the NADH signal represents changes in mitochondrial NADH, this property may be utilized for non-invasive assessment of tissue hypoperfusion. I validated the technique in vitro, and investigated its utility in rat shock models. During graded or abrupt decreases in the constituent parts of tissue oxygen delivery (cardiac output, haemoglobin and oxyhaemoglobin saturation), as well as during resuscitation, I assessed the relationship between skeletal muscle NADH fluorescence intensity, organ perfusion and oxygenation. I compared these against measures of global haemodynamics and tissue perfusion routinely measured in critically ill patients. With each graded insult, NADH fluorescence demonstrated increases reflecting severity of the insult, with improvements upon resuscitation. A persisting rise in NADH fluorescence >50% above baseline foretold death within the following 30-45 minutes, in advance of the other monitored variables. My results indicate that NADH fluorescence may be used for monitoring tissue hypoperfusion in shock states, and as a guide to the timing and adequacy of therapeutic interventions