A new method for the assessment of endothelial function with peripheral arterial volume.

BACKGROUND: Currently, many methodological approaches have been developed to assess peripheral endothelial function. However, a development of the noninvasive and automated technique for routinely assessing endothelial function is still required. We evaluated the potential value of a new method to measure peripheral endothelial function with reactive hyperemia peripheral arterial volume (RH-PAV) in patients with chest pain. METHODS: We used a novel oximeter-like probe to detect the peripheral arterial volume (PAV) of the finger and compared it with brachial flow-mediated dilation (FMD) performed in 93 consecutive patients with chest pain. The RH-PAV index was defined as the ratio of the digital pulse volume during reactive hyperemia relative to the baseline. RESULTS: Ninety-three patients (53 men, 58 ± 5 years) completed the study, and 53 patients demonstrated coronary artery disease (CAD) following scheduled coronary angiography. There was a moderate linear relationship between PAV and FMD (r = 0.69, p < 0.01). Similar to FMD, PAV was more impaired in patients who have more cardiovascular risk factors (CRFs). The subjects with CAD had lower PAV and FMD, compared with those without CAD (1.05 ± 0.23 VS. 1.41 ± 0.37, p < 0.01; 6.7% ± 2.9% VS. 10.4% ± 2.9%, p < 0.01, respectively), and the relationships between FMD and PAV were also significant in both CAD (r = 0.54, p < 0.01) and non-CAD (r = 0.62, p < 0.01) patients. CONCLUSIONS: Endothelial function of digital artery assessed with the novel PAV method demonstrated a profile similar to that of brachial artery measured with FMD. The hyperemia PAV was decreased by factors which were considered to impair endothelial function, suggesting that PAV has the potential to be a novel method to study endothelial function.

Sensitivity of blood volume monitoring for fluid status assessment in hemodialysis patients.

BACKGROUND/AIMS: This study investigates the use of blood volume monitoring (BVM) markers for the assessment of fluid status. METHODS: Predialysis fluid overload (FO) and BVM data were collected in 55 chronic hemodialysis patients in 317 treatments. Predialysis FO was measured using bioimpedance spectroscopy. The slope of the intravascular volume decrease over time normalized by ultrafiltration rate (Slope4h) was used as the primary BVM marker and compared against FO. RESULTS: Average relative blood volume curves were well separated in different FO groups between 0 and 5 liters. Receiver-operating characteristics analysis revealed that the sensitivity of BVM was moderate in median FO ranges between 1 and 3 liters (AUC 0.60-0.65), slightly higher for volume depletion of FO <1 liter (AUC 0.7) and highest for excess fluid of FO >3 liters (AUC 0.85). CONCLUSION: Devices that monitor blood volume are well suited to detect high FO, but are not as sensitive at moderate or low levels of fluid status.

Sensors and hybrid therapies: a new approach with automated citrate anticoagulation.

BACKGROUND: Hybrid therapies use intermittent hemodialysis (IHD) machines adapted to provide prolonged intermittent or continuous renal replacement therapy in the intensive care unit (ICU). Despite the low cost, hybrid therapy use is limited warranting a novel approach. METHODS: The literature was reviewed for limitations of hybrid protocols, use of regional citrate anticoagulation (RCA) on hybrid systems and sensors for IHD and hybrid therapy. The novel hybrid program in the authors' institution is presented as a plausible future direction for the modality. RESULTS: Hybrid therapies are limited by access flow and clotting alarms. Technology limitations render many IHD sensors inoperable at low dialysate flow. A synergy with RCA allows a novel, safe approach with low blood flows and high dialysate flows with alarm- and clotting-free operation and all commercial IHD sensors functional. CONCLUSION: The low cost, ease of use, safety and efficacy of hybrid therapy with near-automated RCA may lead to rapid expansion of this form of ICU renal support.

[Assessment of cardiac output and intrathoracic blood volume by means of transpulmonary thermodilution and ultrasound dilution: similarities and differences].

UNLABELLED: The aim of the study is to compare results of the assessment of cardiac output and intrathoracic blood volume by two methods--transpulmonary (TTD) and ultrasound (UTD) thermodilution. MATERIALS AND METHODS: The prospective study included 58 patients (sepsis, septic shock, acute respiratory distress syndrome, intracranial haemorrhages), which underwent femoral artery catheterization with "Pulsiocath" 5Fr catheter (PICCO technology). For the means of ultrasound the catheter was connected to the central venous catheter by an arteriovenous loop. Sensors on arterial and venous ends of the loop registered the time and the volume of the indicator, blood properties and the ultrasound curve. Cooled (0 to 8 C) 5% glucose solution was used as an indicator for TTD, while heated (up to 37C) 0.9% NaCl solution was used as an indicator for the ultrasound. The cardiac output (CO) was measured by TTD and UTD, the global end diastolic volume (GEDV) by TTD, its analogue total end diastolic volume (TEDV) by UTD, intrathoracic blood volume (ITBV) by TTD and central blood volume (CBV) by UTD. 218 pairs of measurements were conducted. Oscillations of CO (TTD) were 2.76-16.3 l/min (8.6 +/- 2.48 l/min) and of CO (UTD)--2.92-18.1 l/min (8.72 +/- 2.65 l/min). There was a strong correlation between CO (TTD) and CO (UTD). The systematic mistake was 0.12 l/min, percentage based mistake--20.9%. ITBV correlated with CBV. There was a big systematic mistake found, which measured as much as 323 ml, the percentage based mistake was 36.5%. The correlation between GEDV and TEDV was (r = 0.70, p < 0.01). The TTD ejection fraction (23.2 +/- 5.6%) was lower (p < 0.01), than by UTD (57.8 +/- 15.2%). RESULTS: Both methods demonstrate close values of CO. GEDV was higher than TEDV and physiological heart volume. The absolute values of GEDV and ITBV measured by TTD are higher than the actual ones, although they reflect the changes of blood volume and can be used as dynamic preload parameters.

Implantable hemodynamic monitors: Can be conductance catheter system successfully implemented?

Successful management of cardiac heart failure requires a multifactorial approaching. It has been suggested that implantable hemodynamic long-term monitoring can improve patient care. This paper presents an analysis of the hemodynamic parameters commonly recorded, the most used implantable devices and their associated clinical trials. Newly implantable miniaturized sensors and devices are revisited. Finally, a newly implantable conductance-catheter based system is presented. The feasibility to realise volume and pressure measurements in the human left ventricular cavity using an implantable conductance-catheter based system is evaluated. It has the advantage to obtain LV signals continuously. In addition, it allows to realise maneuvers such as calibration and LV function by telemetry being avoiding patient hospitalizations. The rapid advances in device monitoring capabilities could change the new paradigm of the heart disease management.

Assessment of dry weight by monitoring changes in blood volume during hemodialysis using Crit-Line.

BACKGROUND: Routine assessment of dry weight in chronic hemodialysis patients relies primarily on clinical evaluation of patient fluid status. We evaluated whether measurement of postdialytic vascular refill could assist in the assessment of dry weight. METHODS: Twenty-eight chronic, stable hemodialysis patients were studied during routine treatment sessions using constant dialysate temperature and dialysate sodium concentration, and relative changes in blood volume were monitored using Crit-Line III monitors throughout this study. The study was divided into three phases. Phase 1 studies evaluated the time-dependence of vascular compartment refill after completion of hemodialysis. Phase 2 studies evaluated the relationships in patient subgroups between intradialytic changes in blood volume and the presence of postdialytic vascular compartment refill during that last 10 minutes of hemodialysis after stopping ultrafiltration. Phase 3 studies evaluated the extent of dry weight changes following the application of a protocol for blood volume reduction, postdialytic vascular compartment refill, and correlation with clinical evidence of intradialytic hypovolemia and/or postdialytic fatigue. Phase 3 included anywhere from three to five treatments. RESULTS: Phase 1 studies demonstrated that despite interpatient variability in the magnitude of postdialytic vascular compartment refill, when significant refill was evident, it always continued for at least 30 minutes. However, the majority of refill took place within 10 minutes postdialysis. Phase 2 studies identified 3 groups of patients: those who exhibited intradialytic reductions in blood volume but not postdialytic vascular compartment refill (group 1), those who exhibited intradialytic reductions in blood volume and postdialytic vascular compartment refill (group 2), and those whose blood volume did not change substantially during hemodialysis treatment (group 3). In phase 3 studies, use of an ultrafiltration protocol for blood volume reduction and monitoring of postdialytic vascular compartment refill combined with clinical assessment of hypovolemia and postdialytic fatigue demonstrated that patients often had a clinical dry weight assessment which was too low or too high. In all 28 patients studied, dry weight was either increased or decreased following use of this protocol. CONCLUSION: Determination of the extent of both intradialytic decreases in blood volume and postdialytic vascular compartment refill, combined with clinical assessment of intradialytic hypovolemia and postdialytic fatigue, can help assess patient dry weight and optimize volume status while reducing dialysis associated morbidity. The number of hospital admissions due to fluid overload may be reduced.

Assessment of cerebral blood flow by means of blood-flow-volume measurement in the internal carotid artery: comparative study with a 133xenon clearance technique.

BACKGROUND AND PURPOSE: We sought to evaluate a new, angle-independent ultrasonic device for assessment of blood flow volume (BFV) in the internal carotid artery (ICA). METHODS: Nineteen patients and 4 healthy volunteers were enrolled in a comparative study conducted in the Care Unit of the Division of Neurosurgery at UCLA Medical Center. All patients had been admitted because of severe brain injury: 15 patients with severe head trauma (Glasgow Coma Scale score< or =8) and 4 patients with subarachnoid hemorrhage due to aneurysm rupture. In all patients and subjects, cerebral blood flow (CBF) values obtained with the 133xenon-clearance technique were compared with BFV measurements in the ipsilateral ICA. RESULTS: Hemispheric CBF values showed a close and linear correlation with BFV measurements (r=0.76, P<0.0001). Global CBF values showed a higher correlation with the total BFV value obtained from both ICAs (r=0.84, P<0.0001). With 37 mL x min(-1) x 100 g(-1) as a cutoff value for the ischemic range, a BFV value of 220 mL/min would yield a positive predictive value of 91.7% and a negative predictive value of 82.6% (sensitivity 73.3%, specificity 95%). Conversely, BFV sensitivity and specificity were 60% and 96%, respectively, for the hyperemic range defined by a CBF value >55 mL x min(-1) x 100 g(-1) (positive predictive value of 85.7% and negative prediction value of 85.7%). CONCLUSIONS: BFV measurements with this new technology proved to accurately correlate with CBF values evaluated by the 133xenon-clearance technique. These results support the implementation of this technique for bedside assessment of cerebral hemodynamics in critically ill neurosurgical patients.