Monitorización del acceso vascular: parámetros convencionales frente a flujo intraacceso / Vascular access monitoring: conventional parameters versus intra-access flow

Mantener la permeabilidad de los accesos vasculares es un objetivo capital en el paciente en hemodiálisis. Los parámetros clásicos de monitorización del acceso vascular son en general tardíos para la detección de estenosis. El cálculo del flujo intraacceso es un método de segunda generación que permite conocer el flujo sanguíneo máximo del acceso así como detectar estenosis ante una disminución del mismo. El objetivo de este estudio es valorar la eficacia de la medición y vigilancia del flujo intraacceso frente a los parámetros clínicos de primera generación. Mensualmente se realiza monitorización del acceso vascular registrando variables del examen físico y del examen dinámico. La determinación de flujo intraacceso se realiza trimestralmente en FAV y mensualmente en PPTFE. Se indica realización de fistulografía si el flujo intraacceso es menor de 500ml/min o disminución en un 20% confirmado en dos tomas consecutivas, si hay variaciones en la exploración física y disminución ≥ 25% de Kt, flujo sanguíneo o aumento de presiones venosas o recirculación. Se realizan 61 fistulografías. Se hallan diferencias significativas por método de valoración (p<0,001) así como diferencias significativas en falsos positivos (fistulografía blanca o estenosis < 50%) (p=0,024). La monitorización del flujo intraacceso es un método altamente sensible de detección de disfunción del acceso vascular. La combinación de parámetros clínicos, clásicos y el flujo intraacceso en un programa de monitorización del acceso vascular permite detectar más del 80% de los casos confirmados por fistulografía (AU)

It is a major goal in hemodialysis patient to maintain permeable vascular access. Classic parameters for monitoring the vascular access are generally slow to detect stenosis. Intra-access flow calculation is a second-generation method that allows knowing the maximum access blood flow and to detect stenosis when there is a decreased flow. The aim of this study is to assess the efficacy of the measurement and monitoring of intra-access flow compared to first-generation clinical parameters. Vascular access monitoring is done monthly, recording the physical and dynamic examination variables. The determination of intra-access flow is performed quarterly in AVF and monthly in PTFE. Fistulography is recommended if the intra-access flow is less than 500 ml / min or a decrease by 20% confirmed on two consecutive measurements, or if there are variations in the physical examination and Kt decreased by over 25%, blood flow or increased venous pressure or recirculation. 61 fistulographies were performed. Significant differences by valuation method (p <0.001) and in false positives (stenosis <50%) (p = 0.024) was found. Intra-access flow monitoring is a highly sensitive method for detection of vascular access dysfunction. The combination of clinical, classical parameters and intra-access flow in a monitoring program for vascular access, can detect more than 80% of confirmed cases by fistulography (AU)

Nurse-determined assessment of cardiac output. Comparing a non-invasive cardiac output device and pulmonary artery catheter: a prospective observational study.

BACKGROUND: The accurate measurement of Cardiac output (CO) is vital in guiding the treatment of critically ill patients. Invasive or minimally invasive measurement of CO is not without inherent risks to the patient. Skilled Intensive Care Unit (ICU) nursing staff are in an ideal position to assess changes in CO following therapeutic measures. The USCOM (Ultrasonic Cardiac Output Monitor) device is a non-invasive CO monitor whose clinical utility and ease of use requires testing. OBJECTIVES: To compare cardiac output measurement using a non-invasive ultrasonic device (USCOM) operated by a non-echocardiograhically trained ICU Registered Nurse (RN), with the conventional pulmonary artery catheter (PAC) using both thermodilution and Fick methods. DESIGN: Prospective observational study. SETTING AND PARTICIPANTS: Between April 2006 and March 2007, we evaluated 30 spontaneously breathing patients requiring PAC for assessment of heart failure and/or pulmonary hypertension at a tertiary level cardiothoracic hospital. METHODS: SCOM CO was compared with thermodilution measurements via PAC and CO estimated using a modified Fick equation. This catheter was inserted by a medical officer, and all USCOM measurements by a senior ICU nurse. Mean values, bias and precision, and mean percentage difference between measures were determined to compare methods. The Intra-Class Correlation statistic was also used to assess agreement. The USCOM time to measure was recorded to assess the learning curve for USCOM use performed by an ICU RN and a line of best fit demonstrated to describe the operator learning curve. RESULTS: In 24 of 30 (80%) patients studied, CO measures were obtained. In 6 of 30 (20%) patients, an adequate USCOM signal was not achieved. The mean difference (+/-standard deviation) between USCOM and PAC, USCOM and Fick, and Fick and PAC CO were small, -0.34+/-0.52 L/min, -0.33+/-0.90 L/min and -0.25+/-0.63 L/min respectively across a range of outputs from 2.6L/min to 7.2L/min. The percent limits of agreement (LOA) for all measures were -34.6% to 17.8% for USCOM and PAC, -49.8% to 34.1% for USCOM and Fick and -36.4% to 23.7% for PAC and Fick. Signal acquisition time reduced on average by 0.6 min per measure to less than 10 min at the end of the study. CONCLUSIONS: In 80% of our cohort, USCOM, PAC and Fick measures of CO all showed clinically acceptable agreement and the learning curve for operation of the non-invasive USCOM device by an ICU RN was found to be satisfactorily short. Further work is required in patients receiving positive pressure ventilation.

Skin temperature as a noninvasive marker of haemodynamic and perfusion status in adult cardiac surgical patients: an observational study.

OBJECTIVE: Foot temperature has long been advocated as a reliable noninvasive measure of cardiac output despite equivocal evidence. The aim of this pilot study was to investigate the relationship between noninvasively measured skin temperature and the more invasive core-peripheral temperature gradients (CPTGs), against cardiac output, systemic vascular resistance, serum lactate, and base deficit. RESEARCH METHODOLOGY: The study was of a prospective, observational and correlational design. Seventy-six measurements were recorded on 10 adults postcardiac surgery. Haemodynamic assessments were made via bolus thermodilution. Skin temperature was measured objectively via adhesive probes, and subjectively using a three-point scale. SETTING: The study was conducted within a tertiary level intensive care unit. RESULTS: Cardiac output was a significant predictor for objectively measured skin temperature and CPTG (p=.001 and p=.004, respectively). Subjective assessment of skin temperature was significantly related to cardiac output, systemic vascular resistance, and serum lactate (p<.001, respectively). CONCLUSIONS: These results support the utilisation of skin temperature as a noninvasive marker of cardiac output and perfusion. The use of CPTG was shown to be unnecessary, given the parallels in results with the less invasive skin temperature parameters. A larger study is however required to validate these findings.

Monitorización hemodinámica: sistema PiCCO(R) / Hemodynamic monitoring: PiCCO(R) system

La monitorización del gasto cardíaco (GC) en lospacientes críticos tiene como objetivo el mantener yoptimizar la función cardíaca con el objetivoprimordial de obtener una adecuada perfusión tisular.Dicha monitorización se ha realizado, desde haceaños, mediante el empleo del catéter de arteriapulmonar, el cual, cada vez suscita mayorcontroversia. Desde hace algunos años lamonitorización del GC ha ido evolucionando con laaparición de nuevos sistemas de monitorización tantode manera invasiva como no invasiva. En estecapítulo repasamos algunos aspectos de lamonitorización del GC mediante el empleode termodilución transpulmonar con el sistemaPiCCO®. Dicho sistema se basa en la inyecciónde un bolo de suero salino por vía central. Untermistor situado en la punta de un catéter arterial,normalmente femoral, mide los cambios detemperatura sanguíneos creando una curvade termodilución, que tras su análisis nos informará delos parámetros hemodinámicos

Cardiac output (CO) is monitored in critically illpatients to maintain and improve cardiac functionwith the primary goal of adequate tissue perfusion.For a long time, this monitoring has been doneusing the pulmonary arterial catheter, which hasbeen provoking increasing controversy. For someyears, monitoring of CO has been evolving with theappearance of new invasive and non-invasivemonitoring systems. In this chapter we review someaspects of CO monitoring with the PiCCO® systembased on transpulmonary thermodilution. Thissystem is based on the injection of a cold fluidbolus centrally in the vein. A thermistor located inthe tip of the arterial catheter, usually femoral, isused to measure blood temperature changes.A thermodilution curve is created and the hemodynamic parameters obtained after itsanalysis

Arterial pressure-based stroke volume and functional hemodynamic monitoring.

Arterial pressure-based methods are less-invasive methods used to measure stroke volume and to predict fluid responsiveness. An understanding of the assumptions of the measurements and clinical factors that affect their accuracy and ability to predict fluid responsiveness is imperative when deciding when and how to use these new technologies. Frequently asked questions about these technologies and the data provided are addressed.

Método de Termodilución Transpulmonar (PiCCO) para la monitorización hemodinámica del paciente crítico / Transpulmonary Thermodilution Method, also known as induced contour cardiac output (PiCCO) for haemodynamic monitoring of critical patients

La monitorización hemodinámica es esencial para el adecuadomanejo del paciente crítico. Una monitorización eficazdebe mostrar los datos referentes al estado hemodinámicodel paciente que permitan la toma de decisiones paraevitar el deterioro circulatorio realizando un adecuado tratamiento.Son numerosos los métodos que existen para monitorizarel estado hemodinámico del paciente, entre ellos,los más utilizados son el Catéter de Arteria Pulmonar (CAP)o de Swan-Ganz y el gasto cardiaco por análisis de la curvade pulso arterial (en inglés, Pulse-induced Contour CardiacOutput-PiCCO).Este método supone, comparativamente, una monitorizaciónmucho menos invasiva que el tradicional Swan-Ganz,además de ofrecer una serie de parámetros adicionales muyútiles y únicamente disponibles con este sistema PiCCO,como son el volumen sanguíneo intratorácico, el agua pulmonarextravascular, el índice de función cardiaca y la variaciónde volumen sistólico. El interés de estos parámetrosradica en su especificidad para valorar la contractilidady la precarga cardiaca y el edema pulmonar, siendo unosbuenos indicadores globales del funcionamiento cardiaco.El propósito de este trabajo es facilitar a la enfermera los conocimientosnecesarios para el manejo eficaz del PiCCOen el contexto de las Unidades de Cuidados Intensivos (UCI)

Haemodynamic monitoring is essential for adequate managementof the critical patients. Effective monitoring mustshow data concerning the patient’s haemodynamic statusand it will enable decision making to avoid circulatory deteriorationby instituting the proper treatment. Several methodsexists to monitor the patient´s haemodynamic status;among these the most widely use ones are the pulmonaryartery catheter (PAC) or Swan-Ganz method and the pulseinducedcontour cardiac output (PiCCO).This method involves a comparative much less invasivemonitoring approach than the conventional Swan-Ganzmethod. Furthermore, it offers a series of additional very usefulparameters only available with the PiCCO system, suchas intrathoracic blood volume, extravascular pulmonarywater, cardiac function index and variation in systolic volume.The utility of these parameters lies with their specificityto assess the contractility and cardiac precharge and pulmonarydeem, being one of the best overall indicators ofcardiac function. The purpose of this paper is to providethe nurse with the necessary knowledge to effectively managePiCCO within the context of Intensive Care Units (ICUs)

Non-invasive cardiac output monitoring.

Outcomes in the management of critically ill patients may be improved using goal-directed peri-operative haemodynamic monitoring. A conservative approach may no longer be acceptable but in view of the significant morbidity associated with balloon tipped flow directed pulmonary artery catheters a non-invasive approach would be preferable. In this review we consider the different non-invasive techniques available and discuss the advantages and disadvantages of each technique.

Timing of hemodynamic pressure measurements on derived hemodynamic parameters.

The purpose of this study was to examine the difference between hemodynamic pressures and parameters obtained pre- compared to post-thermodilution CO measurements. A repeated measures within subject design was conducted with a cardiac surgical cohort. Three measures of hemodynamic pressures and parameters were determined pre- and post-CO measurements (Set 1) and repeated in 30 minutes (Set 2). The sequence was duplicated in four hours (Sets 3 and 4). Hemodynamic pressures lower pre-CO were PAS at Sets 1 and 3, and SBP, DBP, and MAP at Set 3. Hemodynamic parameters lower pre-CO were PVRI at Set 1 and SVRI at Set 3. These pre-post CO differences did not vary by greater than 10%. As the CO injectate volume had minimal effect, hemodynamic pressures may be obtained pre- or post-CO to derive hemodynamic parameters.

Thermodilution: an advanced technique for measuring continuous cardiac output.

A thermodilution method of obtaining continuous cardiac outputs represents an improvement in the assessment and treatment of critically ill patients. The critical care nurse assists in placement of the pulmonary artery catheter, which includes a thermal filament for continuous readings of cardiac output, and uses the continuous cardiac output readings to make assessment decisions and trouble-shoot the equipment.

Issues in methods and measurement of thermodilution cardiac output.

Criterion-related validity of the thermodilution cardiac output technique for cardiac output measurement has to have a high correlation (r = .91 to .98) with the direct Fick method, the gold standard of cardiac output measurement. Issues that can affect validity of the measurements include the position of the pulmonary artery catheter, the rate of injection of the indicator solution, the volume and temperature of the injectate, the timing of the injection of indicator solution during the respiratory cycle, the position of the subject, and the presence of concomitant infusions. Variation in measurement can be limited by considering the delivery system for the indicator solution, by recording time-temperature cardiac output curves, and by considering normal biologic variations.

Effects of iced and room temperature injectate on cardiac output measurements in critically ill patients with low and high cardiac outputs.

OBJECTIVE: To determine the effect of injectate temperature (iced or room temperature) on cardiac output values in critically ill adults with low and high cardiac outputs. DESIGN: Quasi-experimental. SETTINGS: Two multidisciplinary intensive care units in two large, metropolitan, private, nonprofit hospitals in Texas. SUBJECTS: A convenience sample of 21 critically ill men and women who averaged 61 years of age (range 31 to 82 years) and whose most recent cardiac output measured with room temperature injectate was low (< or = 3.5 L/min) or high (> or = 8.0 L/min). INTERVENTION: Iced injectate and room temperature injectate (randomly ordered) were used to measure cardiac output in each subject. OUTCOME MEASURES: Cardiac output value with iced injectate versus cardiac output value with room temperature injectate. RESULTS: We found significant differences between cardiac output measurements with room temperature and those with iced injectate in eleven critically ill patients with low cardiac outputs (< or = 3.5 L/min) and in ten critically ill patients with high cardiac outputs (> or = 8.0 L/min). In the low cardiac output group, cardiac outputs using room temperature injectate averaged 0.37 L/min (range 0.1 to 1.10 L/min) higher than cardiac outputs using iced injectate (p = 0.001). In the high cardiac output group, measurements with room temperature injectate averaged 1.17 L/min L/min (range 0.3 to 3.0 L/min) higher than cardiac outputs with iced injectate (p = 0.005). Percent differences between room temperature and iced injectate values averaged 13% (range 3% to 27%) in patients with low cardiac outputs and 11% (range 3% to 29%) in patients with high cardiac outputs. Seven (77%) of the patients in the low cardiac output group and four (40%) of the patients in the high cardiac group had a 10% or greater difference--which many clinicians describe as a clinically significant difference--between room temperature and iced injectate cardiac output values. CONCLUSION: Although research is clearly needed to substantiate these findings, we suggest that nurses use iced injectate in patients with low and high cardiac outputs (< or = 3.5 L/min or > or = 8.0 L/min) to ensure accurate measurement of cardiac output.

Comparability of the thermodilution cardiac output method: proximal injectate versus proximal infusion lumens.

In this study we examined the relationship between cardiac output (CO) measurements obtained from the proximal injectate lumen and the proximal infusion lumen of a thermodilution pulmonary artery catheter. The research was predicated on the belief that a strongly significant relationship would provide the clinician with an alternative lumen for measuring CO. Twenty-one subjects were selected by using a nonprobability convenience sampling method. With ice temperature injectate, four injections were performed into one lumen followed by four injections into the alternate lumen. CO values were computed with installed data management physiologic monitors. A Pearson's Product-Moment Correlation Coefficient was calculated, and the result verified a strong positive correlation between CO values (r = 0.96, p = less than 0.0001). Results of a paired t test demonstrated no statistically significant differences between CO means. These findings lend direction for minimizing the potential risk of catheter contamination associated with the manipulation of intravenous lines containing vasoactive medications. It also may save time for the critical care clinician who is trying to balance tasks such as CO measurements and titration of vasoactive or inotropic medications.

Sterility and efficiency of two methods of cardiac output determination: closed loop and capped syringe methods.

A prospective randomized study was done to compare the fluid contamination rates of two methods used to determine cardiac output by thermodilution under in-use conditions. Fifty patients were randomly assigned to have cardiac output measured by the capped syringe or closed loop method, and were followed with quantitative cultures of fluid and catheter. The two treatment groups (n = 25 each) were comparable in terms of age, sex, intensive care unit location, underlying diagnosis, and mean number of cardiac output determinations performed in the first 24 hours after placement of the catheter line. No differences in the rates of fluid contamination were seen at any time between the two groups. The overall fluid contamination rate was 2/124 cultures (1.8% with 95% confidence interval +/- 4.1%) with one colony of Staphylococcus epidermidis from a closed loop sample and one colony of Pseudomonas maltophilia in a capped syringe sample. Although no difference in contamination rates was documented, the closed loop system required less nursing time and effort.