Friederike Compton

Performance of a minimally invasive uncalibrated cardiac output monitoring system (Flotrac™/Vigileo™) in haemodynamically unstable patients†

BACKGROUND Early haemodynamic assessment is of particular importance in the evaluation of haemodynamically compromised patients, but is often precluded by the invasiveness and complexity of the established cardiac output (CO) monitoring techniques. The FloTrac/Vigileo system allows minimally invasive CO determination based on the arterial pressure waveform derived from any standard arterial catheter, and the algorithm underlying CO calculation was recently modified to allow a more precise estimate of aortic compliance. METHODS Using the new software, we studied 25 haemodynamically unstable patients who had a radial artery catheter and underwent invasive haemodynamic monitoring with the PiCCO system. PiCCO-derived transpulmonary thermodilution and pulse contour CO (reference-CO) were compared with the CO values obtained with the FloTrac/Vigileo system (AP-CO). Reported CO values are indexed to body surface area. Agreement between reference-CO and AP-CO recorded during routine clinical care was assessed using Bland-Altman statistics. RESULTS Overall bias between the reference-CO and the AP-CO (n=324) was 0.68 litre min(-1) m(-2) with a high percentage error of +/- 58.8% (95% limits of agreement +/- 1.94 l min(-1) m(-2)). There was a significant difference (P<0.001) between the radial and the femoral mean arterial pressures, and bias was significantly larger for a mean pressure difference of >5 mm Hg (0.93 vs 0.57 litre min(-1) m(-2), P=0.032). No connection was found between the norepinephrine dose and the CO agreement. CONCLUSIONS Despite the updated algorithm, AP-CO still showed a limited agreement with the reference-CO and systematically underestimated the CO so that the method is not suitable to replace invasive CO monitoring at present.

Effect of the venous catheter site on transpulmonary thermodilution measurement variables

Objective:Transpulmonary thermodilution is increasingly used for hemodynamic monitoring of critically ill patients. Injection of a cold saline bolus in the central venous circulation is a prerequisite for transpulmonary thermodilution measurements. Superior vena cava access is typically used for injection. This access, however, is not feasible or available in all intensive care patients (e.g., in burn victims or due to contraindications for Trendelenburg position). The present study investigates whether femoral vein access can be used to obtain clinically acceptable values. Design:Open prospective trial performed between September 2005 and April 2006. Settings:Medical intensive care unit at a university hospital. Patients:Eleven critically ill patients monitored by transpulmonary thermodilution. Interventions:None. Measurements and Main Results:A total of 44 measurements in 11 intensive care patients were performed with the Pulsion PICCO Plus device to compare cardiac output, extravascular lung water index, and global end-diastolic volume index after central venous injection of the cold saline bolus via femoral and jugular venous access. Bland–Altman analysis revealed that catheter insertion site does not relevantly influence cardiac output and extravascular lung water index. The bias between femoral and jugular injection was +0.16 L/min for cardiac output and +0.23 mL/kg for extravascular lung water index. Global end-diastolic volume index values, however, show a constant overestimation of +140.73 mL/m2 after femoral injection, as obtained by Bland–Altman analysis. This overestimation can be explained by a longer mean transit time due to a longer distance of catheter tip and right atrium for a femoral catheter. Conclusions:Transpulmonary thermodilution measurements with a cold saline bolus via a femoral catheter provide clinically reliable cardiac output and extravascular lung water index values. Concerning global end-diastolic volume index, there is a good correlation as well, but in the interpretation of the results, an overestimation has to be taken into account.

Impact of Atrial Fibrillation on the Accuracy of Oscillometric Blood Pressure Monitoring

The introduction of automated oscillometric blood pressure monitors was the basis for today’s widespread use of blood pressure self-measurement. However, in atrial fibrillation, there is a controversial debate on the use of oscillometry because there is a high variability of heart rate and stroke volume. To date, the accuracy of oscillometric blood pressure monitoring in atrial fibrillation has only been investigated using auscultatory sphygmomanometry as reference method, which may be biased by arrhythmia as well. We performed a cross-sectional study in 102 patients (52 sinus rhythm, 50 atrial fibrillation) assessing the accuracy of an automated and validated oscillometric upper arm (M5 Professional, Omron) and wrist device (R5 Professional, Omron) to invasively assessed arterial pressure. Blood pressure values were calculated as the mean of 3 consecutive measurements. Systolic and diastolic blood pressure did not significantly differ in patients with sinus rhythm and atrial fibrillation, independent of the method of measurement (P>0.05 each). The within-subject variability of the oscillometric measurements was higher in patients with atrial fibrillation compared with sinus rhythm (P<0.01 each). The biases of systolic and diastolic blood pressure, however, did not significantly differ in presence or absence of atrial fibrillation in Bland-Altmann analysis (P>0.05 each). In conclusion, atrial fibrillation did not significantly affect the accuracy of oscillometric measurements, if 3 repeated measurements were performed.

Noninvasive Cardiac Output Determination: Broadening the Applicability of Hemodynamic Monitoring:

Although cardiac output (CO) monitoring is usually only used in intensive care units (ICUs) and operating rooms, there is increasing evidence that CO should be determined and optimized as early as possible, even before admission to the ICU, in the care of hemodynamically compromised patients. A variety of different minimally or noninvasive CO determination techniques have been developed, but not all of them are suitable for early hemodynamic monitoring outside the ICU. In this review, the different available methods for CO monitoring are presented and their potential for early hemodynamic assessment is discussed.

Noninvasive cardiac output determination using applanation tonometry-derived radial artery pulse contour analysis in critically ill patients

Conventional thermodilution cardiac output (CO) monitoring is limited mainly to intensive care units and operating rooms because it requires the use of invasive techniques. To reduce the potential for complications and to broaden the applicability of hemodynamic monitoring, noninvasive methods for CO determination are being sought. Applanation tonometry allows noninvasive CO estimation through pulse contour analysis, but the method has not been evaluated in critically ill patients. We therefore performed noninvasive radial artery applanation tonometry in 49 critically ill medical intensive care unit patients and compared CO estimates to invasive CO measurements obtained using a pulmonary artery catheter or the PiCCO® transpulmonary thermodilution system. One-hundred-sixteen measurements were performed, and patients were receiving vasopressor support during 78 measurements. When the data were analyzed with bias and precision statistics, a large bias of 2.03 L · min−1 · m−2 and a high percentage error of 85% were found between the invasive measurements and applanation tonometry-derived CO estimates, with the noninvasive CO results being significantly lower than the invasive ones (P < 0.001). There was no significant difference in bias between the patients who were receiving vasopressor support and those who were not (P = 0.874) or between patients with good and poor applanation tonometry pressure waveform signal quality (P = 0.071). Whereas a significant increase in the invasively determined CO was observed when a fluid bolus was administered (n = 7, P = 0.016), these changes were not reflected by the noninvasive method. We conclude that radial artery applanation tonometry is not suitable to determine CO in critically ill hemodynamically unstable patients.

Volumetric hemodynamic parameters to guide fluid removal on hemodialysis in the intensive care unit

Estimation of removable excess body fluid is difficult in critically ill patients with renal failure. Volumetric hemodynamic parameters are increasingly being used to guide fluid therapy in the intensive care unit, but their suitability to monitor fluid removal with hemodialysis in critically ill patients is not known. Changes in the extravascular lung water index (EVLWI) and intrathoracic blood volume index (ITBVI) measured with transpulmonary thermodilution immediately before and after hemodialysis were analyzed from 39 hemodialysis sessions of 9 patients consecutively treated in the medical intensive care unit of a German University Hospital. Additional hemodynamic, ventilation, and oxygenation‐related parameters were recorded at the same time. Online relative blood volume (RBV) monitoring was performed in 29 sessions. Comparisons of pre and postdialysis values showed a significant reduction of the EVLWI with fluid removal (p=0.009), with only a slight nonsignificant decrease in the ITBVI. The cardiac index (CI) also decreased significantly (p=0.010), whereas blood pressure remained stable. Oxygenation improved significantly (p=0.005), and the hematocrit increased significantly with dialysis (p=0.039). There was no correlation between hematocrit changes and RBV measurements. Significant correlations existed between ITBVI and CI changes (p<0.001), but not to EVLWI reduction. The removal of excess body fluid on hemodialysis is reflected by the EVLWI reduction, whereas the preservation of cardiac preload is shown by ITBVI stability. Volumetric hemodynamic parameters could be useful to guide fluid removal with hemodialysis in the intensive care unit.

Intraoperative Assessment of Kidney Allograft Perfusion by Laser-Assisted Indocyanine Green Fluorescence Videography

BACKGROUND Kidney allograft function crucially depends on the quality of organ perfusion. Duplex sonography, however, frequently reveals hypoperfused segments that remained undetectable to visual inspection intraoperatively. To date, no imaging system supplementing the surgeons experience has achieved clinical acceptance. The present work examines whether laser-assisted indocyanine green (ICG) fluorescence-videography can be used as a safe and sensitive technique for the intraoperative assessment of renal allograft perfusion. METHODS Intraoperative assessment of organ perfusion by laser-assisted ICG fluorescence videography (IC-VIEW) was performed in 10 consecutive de novo renal transplantations. The IC-VIEW system allows the visualization of graft perfusion by the fluorescein dye ICG that emits infrared light after exposure to laser light. RESULTS Perfusion measurements were successful in all 10 transplant recipients. Fluorescence videography produced brilliant, sharply contrasted images of the organs, allowing the detection of even small perfusion deficits. Remarkably, this technique detected 1 large perfusion defect that had remained imperceptible to visual inspection. Repositioning of the graft led to a homogeneous overall perfusion. There were no complications with the ICG injection or the imaging device. CONCLUSION Laser-assisted ICG fluorescence videography is a feasible and safe technique for the intraoperative assessment of renal allograft perfusion.

Validität der Waterlow-Skala zur Dekubitusrisikoeinschätzung auf der Intensivstation: eine prospektive Untersuchung an 698 Patienten

Patienten von Intensivstationen bilden eine besondere Risikogruppe fur die Entwicklung von Dekubiti. Dennoch existieren fur Intensivpatienten bislang keine ausreichend spezifischen, validierten Ins...

Noninvasive pulse wave analysis for the determination of central artery stiffness

Central artery stiffness predicts cardiovascular structural damage and clinical outcome. It is controversial whether central artery stiffness can be determined by noninvasive measurements. We compared noninvasive determination of central artery stiffness obtained from applanation tonometry of the peripheral radial artery waveform with invasive measurements of the ratio of pulse-pressure-to-stroke-volume. A total of 112 invasive measurements of the ratio of pulse-pressure-to-stroke-volume and noninvasive determinations of central artery stiffness were performed in 49 patients on the intensive care unit. In 13 out of 112 attempts of noninvasive measurements (12%) radial pulse could not be obtained using applanation tonometry because of cardiac arrhythmia or radial pulse could not be detected. These 13 failing noninvasive measurements were attempted in 7 patients. In the remaining cases we found a significant correlation between noninvasively obtained central artery stiffness and invasive measurements of the ratio of pulse-pressure-to-stroke-volume (Spearman r=0.40; p<0.0001). The association between invasive and noninvasive measurements was confirmed using Bland-Altman plots. Furthermore, a norepinephrine-induced increase of arterial stiffness was detected both invasively and noninvasively. Noninvasive determination of central artery stiffness obtained from peripheral radial artery waveform should be useful in clinical practice although it cannot be performed in every patient.

Use of a Nutrition Support Protocol to Increase Enteral Nutrition Delivery in Critically Ill Patients

BACKGROUND Early enteral nutrition is recommended for patients in intensive care units, but nutrition provision is often hindered by a variety of unit-specific problems. OBJECTIVES To evaluate the impact of a nutrition support protocol on nutrition prescription and delivery in the intensive care unit. METHODS Nutrition-related data from 73 patients receiving mechanical ventilation who were treated in an adult medical intensive care unit before introduction of an enteral nutrition support protocol were retrospectively compared with data for 87 patients admitted after implementation of the protocol. RESULTS After implementation of the protocol, enteral nutrition was started significantly earlier (P = .007) and enteral feeding goals were reached significantly faster (6 vs 10 days, P < .001) than before. Prescription of enteral nutrition on the first day of invasive mechanical ventilation increased from 38% before to 54% after (P = .03) implementation of the protocol. Prescribed and delivered nutrition doses on the first 2 days of mechanical ventilation also increased significantly (P < .001) after the protocol was implemented. Nasojejunal feeding tubes were used in 52% of patients before and 56% of patients after protocol implementation P = .63). Jejunal tubes were placed earlier after the protocol was implemented than before (median 5 vs 6.5 days), and when a jejunal tube was in place, feeding goals were reached faster (median 2 vs 3 days, P = .002). CONCLUSION Implementing an enteral nutrition support protocol shortened the time to reach feeding goals. Jejunal feeding tubes were necessary in more than half of the patients, and with a jejunal feeding tube in place, feeding goals were reached rapidly.