Non Invasive Haemodynamic Monitoring. Nick Harrison BACCN May 2015

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1 Non Invasive Haemodynamic Monitoring Nick Harrison BACCN May 2015

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3 Hemodynamic monitoring is a cornerstone of care for the hemodynamically unstable patient, but it requires a manifold approach and its use is both context and disease specific. One of the primary goals of hemodynamic monitoring is to alert the health care team to impending cardiovascular crisis before organ injury ensues.

4 Does it matter which haemodynamic monitor to use? Finally, no monitoring tool, no matter how accurate, by itself has improved patient outcome. Pinskey et al (2005)

5 Adolf Fick The principle: " the total uptake of (or release of) a substance by the peripheral tissues is equal to the product of the blood flow to the peripheral tissues and the arterial-venous concentration difference (gradient) of the substance." It is the blood flow we are interested in: this is cardiac output.

6 Fick The True Gold Standard VO 2, the oxygen consumption, is simply the difference between the inspired and expired O 2. You can measure it with an exhaled gas collection bag. You can also estimate it. Conventionally, resting metabolic consumption of oxygen is 3.5 ml of O 2 per kg per minute, or 125ml O 2 per square meter of body surface area per minute. Lets say the meaty pinkish lump below is the patient.

7 Fick teaches us that VO 2 (oxygen extraction) is determined by the following equation: We can rearrange that to form an equation which calculates cardiac output on the basis of oxygen extraction: So, in a normal person, with a body surface area of 2m 2 and thus with a VO 2 of 250ml per minute, CO = 250ml / (200ml 150ml) = 250 / 50 = 5 L/min

8 Where are we Now? Bolus thermodilution Transpulmonary thermodilution Lithium dilution Doppler technique Pulse contour analysis Carbon dioxide rebreathing Bioimpedence / Bioreactance Echocradiography Peripheral pulse variation

9 Choices, Choices

10 Things to consider Theoretical considerations for choosing among hemodynamic monitoring tools Hardware considerations for choosing among hemodynamic monitoring tools Patient-bound considerations for tailoring hemodynamic monitoring Slagt et al. Critical Care 2010, 14:208

11 The New Gold Standard

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13 Problems Extreme level invasiveness Advanced training for placement Incorrect parameter interpretation Complications Arrhythmias Pulmonary rupture Air embolism Most studies focusing on the PAC and outcome have shown no positive association between PAC use for fluid management and survival in the ICU. Wheeler et al. N Engl J Med 2006, 354:

14 Doppler Technology Prof Mervyn Singer is Professor of Intensive Care Medicine at University College First described in mid 1970 s and gained popularity in the 1990 s (Gan and Arrowsmith) Measures blood flow velocity in the descending aorta using flexible ultrasound probe ( 4-5MHz). Measurement combined with estimated cross sectional area of aorta, age, height and weight give haemodynamic variables

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16 Values Stroke Distance: Distance in cm column of blood moves along aorta with every ventricular beat Changes in SD directly related to stroke volume Stroke Volume Amount of blood ejected by heart each beat Flow time Corrected (FTc) Is the duration of flow during systole corrected for the heart rate ( ms) Peak Velocity Highest blood velocity during systole Age dependent - Age 20yrs 50yrs 70yrs PV cm/s cm/s 50-80cm/s

17 Minimally invasive Minimal technical skill required for insertion Good correlation with PAC. Recommended for use in high risk surgery (NICE) Remember Cross section must be accurate Ultrasound beam must be directed parallel to the blood flow Beam direction must NOT undergo any major alterations between measurements (King and Lim (2004), Kauffamn (2000), Prentice and Sonna (2006), Lavdaniti (2008), Tomlin (1975), NICE 2011)

18 Transpulmonary Thermodilution and Pulse Contour Cardiac Output Systems can be divided into 3 categories: Pulse contour analysis requiring and an indicator dilution CO measurement to calibrate the pulse contour (LiDCO, PiCCO, Volumeview ) Pulse contour analysis requiring patient demographic and physical characteristics for arterial impudence estimation (FloTrac, NextFin, Radical 7). Pulse contour analysis that does not require calibration or preloaded data (Most Care System)

19 Pulse Contour Analysis The origin of the pulse contour method of measuring cardiac output is derived from variations in the pulse pressure waveform. In general, the greater the stroke volume, the greater is the amount of blood that must be accommodated in the arterial tree with each heartbeat and, therefore, the greater the pressure rise and fall during systole and diastole, thus causing a greater pulse pressure. The pulse pressure is proportional to stroke volume and inversely related to vascular compliance. Aortic pulse pressure is proportional to SV and is inversely related to aortic compliance. (Chest 2002)

20 Stroke Volume (Pulse pressure ~ Stroke Volume) Aortic Compliance (As the compliance of the vasculature is difficult to measure directly, this is calculated based on age, sex, ethnicity and body mass index (BMI)) Brumfield AMPhysiol Meas 2005;26: Vascular Tone (clinical condition and therapeutic approach)

21 LiDCO First described in Combines pulse power analysis with lithium dilution technique Requires a venous line and arterial catheter Lithium is injected via vein and arterial concentration sampled across a lithium electrode at a rate of 4mls/min. Provides an accurate calibration and corrects for arterial compliance and variation among individuals.

22 Power pulse analysis the magnitude in change of pressure is equal to the magnitude of change in stroke volume The heart rate is calculated by drawing an imaginary line through the arterial waveform. Cardiac output in PulseCo is an estimated figure due to assumption of aortic compliance (Remington et al 1948) uses accepted figure of 250mls. People vary so necessary to calibrate: ΔV / Δbp = calibration x 250 x e k.bp

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24 Advantages Any arterial site can be used. Damping effects of the transducer system is reduced. Safe and accurate (Hett & Jones 2003) Can be calibrated with any form of CO measurement Good correlation with PAC (Costa et al 2008)

25 Calibration can be time consuming Expense Not recommended in first trimester of pregnancy Under 40kgs Patients receiving NMB can cause delay Aortic valve regurgitation

26 Transpulmonary Thermodilution and Pulse Contour Analysis (TPCO) PiCCO and VolumeView Requires a central vein catheterisation and arterial catheter (femoral preferable) Continuous pulse contour SV is calculated from the area under systolic portion of the arterial waveform Shape of arterial waveform, arterial compliance, SVR These devices use the same basic principles of dilution to estimate the cardiac output as with PAC thermodilution

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28 PediaSa t Catheter EV1000 Clinical Platform Vigileo Monitor Critical Care Educatio n Product Catalog Request Informat ion Home / Products / Advanced Hemodynamic Monitoring / VolumeView Set / VolumeView System Set Up Advance d Hemody namic Monitori ng Volu mevi ew Syste m Set Up VolumeVie w sensor VolumeVie w femoral arterial catheter VolumeVie w thermistor manifold CVC standard TruWave pressure transducer EV1000 clinical platform Rear view of databox Product DetailsBro chure Models Paramete rs Set Up The Set Education al Materials Quick Guide 2nd Edition Technolog y Overview Video Physiologi c Implication s of Appropriat e Resuscitati on Fluid Responsive ness in the Critically Ill Patient elearning Module Related ProductsE V1000 Clinical Platform PreSep Catheter Experience the Edwards Critical Care System MICROSITE VolumeView sensor VolumeView femoral arterial catheter VolumeView thermistor manifold CVC standard TruWave pressure transducer EV1000 clinical platform Hemodynamic Parameters CO - Calibrated Cardiac Output SV - Calibrated Stroke Volume SVR - Systemic Vascular Resistance SVV - Stroke Volume Variation SVI - Stroke Volume Index Volumetric Parameters EVLW - Extravascular Lung Water PVPI - Pulmonary Vascular Permeability Index GEDV - Global End Diastolic Volume GEF - Global Ejection Fraction

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30 Advantages Continuous cardiac output monitoring Good accuracy Disadvantages Can be complicated to set up Needs specific femoral artery catheter Remains significantly invasive Can be effected by arrhythmias

31 Vigileo Each of these systems contains a proprietary algorithm for converting a pressure-based signal into a flow measurement. Needs no external calibration Use the equation SV = SD AP x (Khi)ᵡ Analyses the area under the systolic portion of the arterial pressure waveform from the end diastole phase to the end of the ejection phase corresponds to SV.

32 The pulse pressure is obtained by the complete analysis of the arterial waveform and through the calculation of the standard deviation (sd) at each sample points. (sampling rate of 100Hz results in 2000 data points) sd(ap) ~ Pulse Pressure ~ Stroke Volume The SV value is updated every 20 seconds

33 The variations or changes in the vascular tone are integrated in a continuous calibration factor (Khi x ) obtained from a multivariate equation of two major elements : APCO algorithm Biometric variables : age, sex, height (Langewouters et al.) Shape variables : analysis of the different characteristics of the arterial pressure waveform. Skewness (Dissymmetry coefficient) Kurtosis (Flattening coefficient) Pulsatility

34 Advantages Easy to set up Needs no external calibration

35 Areas of Concern Outdated and superseded Over the past 5 years and many software updates much research has identified the Vigileo as inaccurate at determining haemodynamic variables within a host of critical care patients. Poor accuracy with arrhythmia. SVV only reliable in mechanically ventilated patients Requires specific arterial pressure sensor Cannot track changes in large vasomotor swings..

36 Partial CO 2 Rebreathing Uses the Fick principle with CO 2 as the marker gas (Berton & Chorley 2002) System distributed is called NICO (Philips) The CO 2 partial rebreathing technique compares end-tidal carbon dioxide partial pressure obtained during a nonrebreathing period with that obtained during a subsequent rebreathing period. The ratio of the change in end-tidal carbon dioxide and CO 2 elimination after a brief period of partial rebreathing (usually 50 seconds) provides a non-invasive estimate of the CO.

37 Partial CO 2 rebreathing (NICO ) *minimal tidal volume = 200ml

38 There are several limitations to this device including: The need for intubation and mechanical ventilation with fixed ventilator settings and minimal gas exchange abnormalities. Gueret G et al Eur J Anaesthesiology (2006), 23: Variations in ventilator settings, mechanically assisted spontaneous breathing, the presence of increased pulmonary shunt fraction, and hemodynamic instability have been associated with decreased accuracy. Tachibana K et al Anaesthesiology (2003), 98: Considering the limitations of this technology and the potential inaccuracies, the routine use of the CO 2 rebreathing technique to guide fluid and vasopressor therapy cannot be recommended.

39 Thoracic Electrical Bioimpedance impedance = measure of opposition to alternating current (AC) How it works: superficial electrodes applied to chest that both measure and apply voltage current is transmitted through the chest via the path of least resistance (aorta) portion of initial (known) voltage that reaches a distant sensing electrode is measured baseline impedance to the current is recorded with each heartbeat, blood volume and velocity in the aorta change corresponding change in impedance change in impedance used to calculate stroke volume and cardiac output according to algorithm based on changes in thoracic blood volume

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41 Bioimpedance / Bioreactance Developed since the 1960 s (NASA) 4 electrodes in pairs each pair comprises transmitting and sensing properties High frequency current of known amplitude and frequency across the chest measures changes in voltage. Ratios between voltage and current amplitudes = impedance (Zo), and varies in proportion of amount of fluid in the chest. Changes in impedance correlates with SV:

42 Cheetah NICOM

43 CAPTURES (14 ) PARAMETERS In Real Time TPR : Dynes (MAP / CO)*80 TPR : mmhg * min./liters (MAP / CO) TFCd : % Change in TFC over 15 mins. Vs. baseline TFC CP: MAP*CO/451 CPI: SVR CP/BSA MAP-CVP / CO CO CI SV SVV SVI HR TPR VET MAP NIBP TFC Cardiac Output Cardiac Index Stoke Volume Stroke Volume Variance Stroke Volume Index Heart Rate Total Peripheral Resistance Ventricular Ejection Time Mean Arterial Pressure Non Invasive Blood Pressure Thoracic Fluid Content TFCd % Directional Change in TFC/Time CP CPI Cardiac Power Cardiac Power Index

44 Limitations However, a poor correlation between derived CO and that determined by thermodilution in the setting of a cardiac catheterization laboratory was reported. In the Bioimpedance CardioGraphy (BIG) substudy of the ESCAPE heart failure study, there was a poor agreement among TEB and invasively measured hemodynamic profiles. Kamath et al (2009) Heart J 158: Bioimpedance has been found to be inaccurate in the intensive care unit and other settings in which significant electric noise and body motion exist and in patients with increased lung water. Gujjar et al (2008) J Clin Monit Comput 22: Furthermore, this technique is sensitive to the placement of the electrodes on the body, variations in patient body size, and other physical factors that impact on electric conductivity between the electrodes and the skin (eg, temperature and humidity)

45 This device provides a non-invasive estimation of cardiac output in two steps For this purpose, the device includes an inflatable cuff that is wrapped around a finger. It also includes a photoplethysmographic device that measures the diameter of the finger arteries. At each systole, the photoplethysmographic device senses the increase of the finger arteries diameter. A fast servo controlled system immediately inflates the cuff in order to keep the arteries diameter constant. Therefore, cuff pressure reflects the arterial pressure. Its continuous measurement allows estimation of the arterial pressure curve. The second step is to estimate cardiac output from the non-invasive arterial pressure curve. For this purpose, the Nexfin device includes pulse contour analysis software that computes cardiac output from the arterial pressure curve

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47 Stroke Volume 10 % Lower PVI = Less likely to respond to fluid administration 24 % 0 0 Maxime Cannesson, MD, PhD Preload

48 Pleth variability index (PVI) is a new algorithm allowing automated and continuous monitoring of respiratory variations in the pulse oximetry plethysmographic waveform amplitude. PVI can predict fluid responsiveness noninvasively in mechanically ventilated patients during general anesthesia

49 Echocardiogram Although echocardiography traditionally is not considered a monitoring device, both transthoracic and transesophageal echocardiography provide invaluable information on both left and right ventricular function, which is crucial in the management of hemodynamically unstable patients. Levitov et al (2012) Cardiol Res Pract: Salem et al (2008) Curr Opin Crit Care 14:

50 Choose wisely.

51 Algorithms

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54 Remember. Treat the patient Don t treat the monitors Depending on the clinical setting, adequate monitoring can definitely help the clinician to better treat his patient and improve the final outcome.

55 Maybe in the Future our patients will look like this!! Oxygenation Perfusion

56 Any Questions