Different effects of fluid loading with saline, gelatine, hydroxyethyl starch or albumin solutions on acid-base status in the critically ill.

INTRODUCTION:Fluid administration in critically ill patients may affect acid-base balance. However, the effect of the fluid type used for resuscitation on acid-base balance remains controversial. METHODS:We studied the effect of fluid resuscitation of normal saline and the colloids gelatine 4%, hydroxyethyl starch (HES) 6%, and albumin 5% on acid-base balance in 115 clinically hypovolemic critically ill patients during a 90 minute filling pressure-guided fluid challenge by a post-hoc analysis of a prospective randomized clinical trial. RESULTS:About 1700 mL was infused per patient in the saline and 1500 mL in each of the colloid groups (P<0.001). Overall, fluid loading slightly decreased pH (P<0.001) and there was no intergroup difference. This mildly metabolic acidifying effect was caused by a small increase in chloride concentration and decrease in strong ion difference in the saline- and HES-, and an increase in (uncorrected) anion gap in gelatine- and albumin-loaded patients, independent of lactate concentrations. CONCLUSION:In clinically hypovolemic, critically ill patients, fluid resuscitation by only 1500-1700 mL of normal saline, gelatine, HES or albumin, resulted in a small decrease in pH, irrespective of the type of fluid used. Therefore, a progressive metabolic acidosis, even with increased anion gap, should not be erroneously attributed to insufficient fluid resuscitation. TRIAL REGISTRATION:ISRCTN Registry ISRCTN19023197

Assessing breathing effort in mechanical ventilation: physiology and clinical implications

Recent studies have shown both beneficial and detrimental effects of patient breathing effort in mechanical ventilation. Quantification of breathing effort may allow the clinician to titrate ventilator support to physiological levels of respiratory muscle activity. In this review we will describe the physiological background and methodological issues of the most frequently used methods to quantify breathing effort, including esophageal pressure measurement, the work of breathing, the pressure-time-product, electromyography and ultrasound. We will also discuss the level of breathing effort that may be considered optimal during mechanical ventilation at different stages of critical illness

Vitamin C: should we supplement?

PURPOSE OF REVIEW: Hypovitaminosis C and vitamin C deficiency are very common in critically ill patients due to increased needs and decreased intake. Because vitamin C has pleiotropic functions, deficiency can aggravate the severity of illness and hamper recovery. RECENT FINDINGS: Vitamin C is a key circulating antioxidant with anti-inflammatory and immune-supporting effects, and a cofactor for important mono and dioxygenase enzymes. An increasing number of preclinical studies in trauma, ischemia/reperfusion, and sepsis models show that vitamin C administered at pharmacological doses attenuates oxidative stress and inflammation, and restores endothelial and organ function. Older studies showed less organ dysfunction when vitamin C was administered in repletion dose (2-3 g intravenous vitamin C/day). Recent small controlled studies using pharmacological doses (6-16 g/day) suggest that vitamin C reduces vasopressor support and organ dysfunction, and may even decrease mortality. SUMMARY: A short course of intravenous vitamin C in pharmacological dose seems a promising, well tolerated, and cheap adjuvant therapy to modulate the overwhelming oxidative stress in severe sepsis, trauma, and reperfusion after ischemia. Large randomized controlled trials are necessary to provide more evidence before wide-scale implementation can be recommended

Acid-base balance and electrolytes.

<p>Acid-base balance and electrolytes.</p

Sodium-chloride differences and (un)corrected anion gaps in various fluid types.

<p>(A) Mean (error bars represent +/- standard deviation) of sodium-chloride differences (Na⁺-Cl^-) at baseline and after 90 minutes loading of various fluid types. For sodium-chloride difference: P = 0.032 T = 90 vs T = 0, P<0.001 for change between groups and P<0.001 for change in gelatine or albumin vs saline and hydroxyethyl starch (HES). (B) Mean of uncorrected anion gaps at baseline and after 90 minutes loading of various fluid types. P<0.001 for change between groups, P = 0.027 or lower for change in gelatine vs saline and hydroxyethyl starch (HES) and change in albumin vs saline and HES. P<0.001 for change in HES vs gelatine and albumin. (<b>C)</b> Mean of corrected anion gaps (AG) at baseline and after 90 minutes loading of various fluid types. P<0.001 for change between groups, P<0.001 for change in gelatine vs saline, hydroxyethyl starch (HES), and albumin.</p

Patient population flow chart.

<p>N; number. HES; hydroxyethyl startch.</p