We have previously shown that ��VpeakBA measured by HCUS mirrors the respiratory Erlotinib manufacturer changes in arterial blood pressure transduced through a radial artery catheter [11], and suggested that this might serve as a non-invasive parameter for gauging fluid responsiveness. Monge Garc��a and colleagues have confirmed and extended this work by directly correlating ��VpeakBA to the impact of a fluid challenge [1]. Subjects had a regular cardiac rhythm, lacked respiratory efforts (assured by examination of ventilator waveforms and, if signs of effort were seen, by neuromuscular blockade), were ventilated with tidal volumes of 8 to 10 cm3/kg ideal body weight, and were judged fluid responsive if the stroke volume index increased by at least 15% after 500 cm3 colloid.

The primary finding was that ��VpeakBA >10% predicted fluid responsiveness with a sensitivity of 74% and a specificity of 95%.Three additional findings deserve comment. First, as others have shown, radial artery pulse pressure variation quite accurately predicted the response to fluid, with a value >10% being both sensitive and specific (95% and 95%). Second, the mean arterial blood pressure increased 13 mmHg in the nonresponders, confirming that this simple vital sign cannot serve as a surrogate for changes in perfusion. Finally, the central venous pressure performed poorly (area under the receiver operator characteristic curve only 0.64).Dynamic predictors (especially pulse pressure variation) are clearly superior to static pressures, but the role of ��VpeakBA is less certain. First, a screening test demands high sensitivity (not specificity).

For the clinician to withhold a fluid challenge, the predictor must identify nearly all patients capable of responding, otherwise too many patients will be denied a potentially life-saving therapy. A sensitivity of 74% does not meet this test. Second, a rapid, non-invasive monitor such as HCUS might have greatest application in the field or very early in resuscitation, before invasive lines are placed. Yet the risk-benefit dilemma posed by fluid bolus is rare in the field-renal failure is not established and the likelihood of responding to fluid is surely much higher than the 50% range typical of intensive care unit patients.While the study of Monge Garc��a and colleagues corroborates the view that fluid responsiveness is best predicted dynamically, further work is needed before ��VpeakBA finds arole in clinical practice.Abbreviations��VpeakBA: variation in brachial artery peak flow velocity; Entinostat HCUS: hand-carried ultrasound.Competing interestsThe author declares that they have no competing interests.NotesSee related research by Monge Garc��a et al., http://ccforum.