Continuously assessed right ventricular end-diastolic volume as a marker of cardiac preload and fluid responsiveness in mechanically ventilated cardiac surgical patients

INTRODUCTION: Assessing cardiac preload and fluid responsiveness accurately is important when attempting to avoid unnecessary volume replacement in the critically ill patient, which is associated with increased morbidity and mortality. The present clinical trial was designed to compare the reliability of continuous right ventricular end-diastolic volume (CEDV) index assessment based on rapid response thermistor technique, cardiac filling pressures (central venous pressure [CVP] and pulmonary capillary wedge pressure [PCWP]), and transesophageal echocardiographically derived evaluation of left ventricular end-diastolic area (LVEDA) index in predicting the hemodynamic response to volume replacement. METHODS: We studied 21 patients undergoing elective coronary artery bypass grafting. After induction of anesthesia, hemodynamic parameters were measured simultaneously before (T1) and 12 min after volume replacement (T2) by infusion of 6% hydroxyethyl starch 200/0.5 (7 ml/kg) at a rate of 1 ml/kg per min. RESULTS: The volume-induced increase in thermodilution-derived stroke volume index (SVI(TD)) was 10% or greater in 19 patients and under 10% in two. There was a significant correlation between changes in CEDV index and changes in SVI(TD )(r(2 )= 0.55; P < 0.01), but there were no significant correlations between changes in CVP, PCWP and LVEDA index, and changes in SVI(TD). The only variable apparently indicating fluid responsiveness was LVEDA index, the baseline value of which was weakly correlated with percentage change in SVI(TD )(r(2 )= 0.38; P < 0.01). CONCLUSION: An increased cardiac preload is more reliably reflected by CEDV index than by CVP, PCWP, or LVEDA index in this setting of preoperative cardiac surgery, but CEDV index did not reflect fluid responsiveness. The response of SVI(TD )following fluid administration was better predicted by LVEDA index than by CEDV index, CVP, or PCWP

Evaluation of a new arterial pressure-based cardiac output device requiring no external calibration

<p>Abstract</p> <p>Background</p> <p>Several techniques have been discussed as alternatives to the intermittent bolus thermodilution cardiac output (CO_PAC) measurement by the pulmonary artery catheter (PAC). However, these techniques usually require a central venous line, an additional catheter, or a special calibration procedure. A new arterial pressure-based cardiac output (CO_AP) device (FloTrac™, Vigileo™; Edwards Lifesciences, Irvine, CA, USA) only requires access to the radial or femoral artery using a standard arterial catheter and does not need an external calibration. We validated this technique in critically ill patients in the intensive care unit (ICU) using CO_PACas the method of reference.</p> <p>Methods</p> <p>We studied 20 critically ill patients, aged 16 to 74 years (mean, 55.5 ± 18.8 years), who required both arterial and pulmonary artery pressure monitoring. CO_PACmeasurements were performed at least every 4 hours and calculated as the average of 3 measurements, while CO_APvalues were taken immediately at the end of bolus determinations. Accuracy of measurements was assessed by calculating the bias and limits of agreement using the method described by Bland and Altman.</p> <p>Results</p> <p>A total of 164 coupled measurements were obtained. Absolute values of CO_PACranged from 2.80 to 10.80 l/min (mean 5.93 ± 1.55 l/min). The bias and limits of agreement between CO_PACand CO_APfor unequal numbers of replicates was 0.02 ± 2.92 l/min. The percentage error between CO_PACand CO_APwas 49.3%. The bias between percentage changes in CO_PAC(ΔCO_PAC) and percentage changes in CO_AP(ΔCO_AP) for consecutive measurements was -0.70% ± 32.28%. CO_PACand CO_APshowed a Pearson correlation coefficient of 0.58 (<it>p </it>< 0.01), while the correlation coefficient between ΔCO_PACand ΔCO_APwas 0.46 (<it>p </it>< 0.01).</p> <p>Conclusion</p> <p>Although the CO_APalgorithm shows a minimal bias with CO_PACover a wide range of values in an inhomogeneous group of critically ill patients, the scattering of the data remains relative wide. Therefore, the used algorithm (V 1.03) failed to demonstrate an acceptable accuracy in comparison to the clinical standard of cardiac output determination.</p

Zielgerichtete Volumentherapie durch Optimierung von Schlagvolumen (variation) bei Hochrisikoeingriffen:eine randomisierte kontrollierte Multicenter Pilotstudie

Subject: Perioperative hemodynamic optimization reduces the incidence of postoperative complications in patients after high-risk interventions. We investigated the influence of a targeted, individualized intraoperative volume therapy, based on measurements of stroke volume variation (SVV) and stroke volume (SV), on the postoperative patient outcome. Material, Methods: 52 high-risk patients (ASA 3 or 4) were treated with the consent of the respective ethics committee randomized either to a control group (group K, n = 26) or a targeted therapy group (group T, n = 26). Patients with cardiac arrhythmias or a tidal volume <7 ml / kg under mechanical ventilation were excluded. SVV and SV were measured continuously (FloTrac / Vigileo, Edwards Lifesciences, Irvine, USA). Patients of the therapie group received colloidal fluid (200 ml 6% HAES130 / 0.4) until a plateau is reached on the Frank-Starling curve (SVV <10% and SV increase <10% after volume release). On the intensive care unit organ dysfunction (SOFA score) and therapy intensity (TISS score) detected. Patients were postoperative over a period of 28 days is observed. Results: Both groups were similar in terms of ASA status, comorbidity, type and duration of the procedure (275 vs. 280 min), heart rate, blood pressure, and CVP to OP start. However, patients in group T were younger than in group K (68 vs. 73 years, p <0.05). Intraoperatively, patients of the therapy group received more colloids (1589 vs. 927 ml, p <0.05) and the SVV decreased significantly in the therapy group (from 9.0 to 8.0%, p <0.05), but not in the control group. The number of postoperative wound infections was also significantly lower in the therapy group (0 vs. 7, p <0.01). In addition, the proportion of patients with at least one complication (46 vs. 62%), the number of postoperative complications per patient (0.65 vs. 1.40), the maximum SOFA score (5.9 vs. 7,2) and the cumulative TISS score (69 vs. 83) were also lower in the therapy group. Conclusions: This pilot study suggests that targeted intraoperative volume therapy reduces the incidence of postoperative wound infections and organdy functions and thus the consumption of resources. this is the first multicenter study, which shows a positive effect on patient outcome by the perioperative use of extended hemodynamic monitoring. Courtesy of Edwards Lifesciences, Irvine, USA

Goal-directed intraoperative fluid therapy guided by stroke volume and its variation in high-risk surgical patients:a prospective randomized multicentre study

<p>Perioperative hemodynamic optimisation improves postoperative outcome for patients undergoing high-risk surgery (HRS). In this prospective randomized multicentre study we studied the effects of an individualized, goal-directed fluid management based on continuous stroke volume variation (SVV) and stroke volume (SV) monitoring on postoperative outcomes. 64 patients undergoing HRS were randomized either to a control group (CON, n = 32) or a goal-directed group (GDT, n = 32). In GDT, SVV and SV were continuously monitored (FloTrac/Vigileo) and patients were brought to and maintained on the plateau of the Frank-Starling curve (SVV <10 % and SV increase <10 % in response to fluid loading). Organ dysfunction was assessed using the SOFA score and resource utilization using the TISS score. Patients were followed up to 28 days for postoperative complications. Main outcome measures were the number of complications (infectious, cardiac, respiratory, renal, hematologic and abdominal post-operative complications), maximum SOFA score and cumulative TISS score during ICU stay, duration of mechanical ventilation, length of ICU stay, and time until fit for discharge. 12 patients had to be excluded from final analysis (6 in each group). During surgery, GDT received more colloids than CON (1,589 vs. 927 ml, P <0.05) and SVV decreased in GDT (from 9.0 to 8.0 %, P <0.05) but not in CON. The number of postoperative wound infections was lower in GDT (0 vs. 7, P <0.01). Although not statistically significant, the proportion of patients with at least one complication (46 vs. 62 %), the number of postoperative complications per patient (0.65 vs. 1.40), the maximum sofa score (5.9 vs. 7.2), and the cumulative TISS score (69 vs. 83) tended to be lower. This multicentre study shows that fluid management based on a SVV and SV optimisation protocol is feasible and decreases postoperative wound infections. Our findings also suggest that a goal-directed strategy might decrease postoperative organ dysfunction.</p>

Implantation and testing of subretinal film electrodes in domestic pigs

By definition, an electronic subretinal visual prosthesis requires the implantation of stimulation electrodes in the subretinal space of the eye. Polyimide film electrodes with flat contacts were implanted subretinally and used for electrical stimulation in acute experiments in anaesthetised domestic pigs. In two pigs, the film electrode was inserted through a sclerostomy into the vitreous cavity and, subsequently, via a retinotomy into the subretinal space around the posterior pole (ab interno approach). In three other pigs the sclera and pigment epithelium were opened for combined ab interno and transscleral positioning of the subretinal electrode. In all cases, perfluorocarbon liquid (PFCL) was used to establish a close contact between the film electrode and the outer retina. After cranial preparations of three pigs for epidural recording of visual cortex responses, retinal stimulation was performed in one pig with a film electrode implanted ab interno and in two pigs with film electrodes implanted by the ab interno and transscleral procedure. The five subretinal implantations were carried out successfully and each polyimide film electrode tip was positioned beneath the outer retina of the posterior pole. The retina was attached to the stimulation electrode in all cases. Epidural cortical responses to light and electrical stimulation were recorded in three experiments. Initial cortical responses to Ganzfeld light and to electrical stimuli occurred about 40 and 20 ms, respectively, after stimulation onset. The stimulation threshold was approximately 100 microA and, like the cortical response amplitudes, depended both on the correspondence between retinal stimulation and cortical recording sites and on the number of stimulation electrodes used simultaneously. Our results in a domestic pig model demonstrate that polyimide film electrodes can be implanted subretinally and tested by recording cortical responses to electrical stimulation. These findings suggest that the domestic pig could be an appropriate animal model for basic testing of subretinal implants