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Cardiac Stroke Volume (cardiac + stroke_volume)
Selected AbstractsModelflow estimates of cardiac output compared with Doppler ultrasound during acute changes in vascular resistance in womenEXPERIMENTAL PHYSIOLOGY, Issue 4 2010Kenneth S. Dyson We compared Modelflow (MF) estimates of cardiac stroke volume (SV) from the finger pressure-pulse waveform (Finometer®) with pulsed Doppler ultrasound (DU) of the ascending aorta during acute changes in total peripheral resistance (TPR) in the supine and head-up-tilt (HUT) postures. Twenty-four women were tested during intravenous infusion of 0.005 or 0.01 ,g kg,1 min,1 isoprenaline, 10 or 50 ng kg,1 min,1 noradrenaline and 0.3 mg sublingual nitroglycerine. Responses to static hand-grip exercise (SHG), graded lower body negative pressure (LBNP, from ,20 to ,45 mmHg) and 45 deg HUT were evaluated on separate days. Bland,Altman analysis indicated that SVMF yielded lower estimates than SVDU during infusion of 0.01 ,g kg,1 min,1 isoprenaline (SVMF 92.7 ± 15.5 versus SVDU 104.3 ± 22.9 ml, P= 0.03) and SHG (SVMF 78.8 ± 12.0 versus SVDU 106.1 ± 28.5 ml, P < 0.01), while larger estimates were recorded with SVMF during ,45 mmHg LBNP (SVMF 52.6 ± 10.7 versus SVDU 46.2 ± 14.5 ml, P= 0.04) and HUT (SVMF 59.3 ± 13.6 versus SVDU 45.2 ± 11.3 ml, P < 0.01). Linear regression analysis revealed a relationship (r2= 0.41, P < 0.01) between the change in TPR from baseline and the between-methods discrepancy in SV measurements. This relationship held up under all of the experimental protocols (regression for fixed effects, P= 0.46). These results revealed a discrepancy in MF estimates of SV, in comparison with those measured by DU, during acute changes in TPR. [source] The hypoxic threshold for maximum cardiac performance in rainbow trout Oncorhynchus mykiss (Walbaum) during simulated exercise conditions at 18° CJOURNAL OF FISH BIOLOGY, Issue 3 2007L. M. Hanson Perfused rainbow trout Oncorhynchus mykiss hearts exposed to simulated exercise conditions (hypoxia, hyperkalemia and acidosis) at 18° C experienced complete failure of maximum cardiac performance at oxygen tensions <5·6 kPa and partial failure at <6·7 kPa. This hypoxic threshold, which occurred in the presence of maximal adrenergic stimulation (500 nM adrenaline), is unusually high compared with previous results at a colder acclimation temperature. Cardiac failure was primarily due to significant decreases (P < 0·05) in heart rate rather than cardiac stroke volume at all hypoxia levels tested. [source] Stroke volume averaging for individualized goal-directed fluid therapy with oesophageal DopplerACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 1 2009C. C. JØRGENSEN Background: An individualized fluid optimization strategy, based on maximization of cardiac stroke volume (SV) with colloid boluses (goal-directed therapy), improves outcome after surgery. Oesophageal Doppler (OD) is used for SV maximization in most randomized studies, but evidence-based guidelines for the SV maximization procedure are lacking and variation in SV may influence the indication for fluid administration. We measured beat-to-beat OD SV before and after fluid optimization in order to estimate the number of heartbeats for which SV needs to be averaged to provide an acceptable accuracy for goal-directed therapy with this technology. Methods: Twenty patients scheduled for surgery were anaesthetized, followed by OD SV assessment. Thirty seconds of beat-to-beat data were recorded before and after volume optimization performed by successive boluses of 200 ml colloid until SV did not increase ,10%. SV variability was assessed before and after the volume optimization when SV was measured beat to beat and when it was averaged over 2,10 heartbeats. Results: Nineteen (95%) and 17 (85%) patients demonstrated an SV variability ,10% before and after volume optimization, respectively, when SV was measured beat to beat. However, when SV was averaged over 10 heartbeats, only two (10%) and one (5%) of the patients demonstrated an SV variability ,10% before and after optimization, respectively (P<0.0001). Conclusion: OD SV variability is significantly reduced and reaches an acceptable level when SV is averaged over 10 heartbeats. The use of a shorter averaging period for SV may lead to incorrect volume administration in goal-directed fluid management. [source] Normovolemia defined according to cardiac stroke volume in healthy supine humansCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 5 2010Morten Bundgaard-Nielsen Summary Background:, Both hypovolemia and a fluid overload are detrimental for outcome in surgical patients but the effort to establish normovolemia is hampered by the lack of an operational clinical definition. Manipulating the central blood volume on a tilt table demonstrates that the flat part of the Frank-Starling curve is reached when subjects are supine and that finding may be applicable for a clinical definition of normovolemia. However, it is unknown whether stroke volume (SV) responds to an increase in preload induced by fluid administration. Methods:, In 20 healthy subjects (23 ± 2 years, mean ± SD), SV was measured by esophageal Doppler before and after fluid administration to evaluate whether SV increases in healthy, non-fasting, supine subjects. Two hundred millilitres of a synthetic colloid (hydroxyethyl starch, HES 130/0·4) was provided and repeated if a ,10% increment in SV was obtained. Results:, None of the subjects increased SV ,10% following fluid administration but there was a minor increase in mean arterial pressure (92 ± 15 to 93 ± 12 mmHg, P = 0·01), while heart rate (HR) (66 ± 12 beats min,1; P = 0·32), cardiac output (4·8 ± 1·1 l min,1; P = 0·25) and the length of the systole corrected to a HR of 60 beats/min (corrected flow time; 344 ± 24 ms; P = 0·31) did not change. Conclusion:, Supporting the proposed definition of normovolemia, non-fasting, supine, healthy subjects are provided with a preload to the heart that does not limit SV suggesting that the upper flat part of the Frank-Starling relationship is reached. [source] | ||||||||||