Cradiac Output Monitoring Flashcards

Question

What is the Cardiac Index?

Answer 1

CI = CO referenced against bodyweight (ml/min/kg) or body surface area (ml/min/m2)

Answer 2

dogs: 125-200 ml/kg/min cats: 120 ml/kg/min

Answer 3

- Fick method (Oxygen consumption or CO2 rebreathing) - Indicator dilution (thermodilution, lithium dilution) - pulse contour analysis - echocardiography - transthoracic Doppler - Pulse wave transit time

Answer 4

based on the notion that tissue oxygen consumption (VO2) will be dictated by the product of CO and the difference between arterial (CaO2) and venous oxygen (CvO2) content. CO=VO2 /(CaO2 xCvO2) VO2: measuring oxygen concentration difference between inhaled and exhaled air in the amount of oxygen inhaled over a period of time (typically 3 minutes) Downsides: - Patient needs to be intubated - arterial sampling (ideally from the pulmonary artery, but cranial VC also acceptable) - no real-time assessment of CO - major intracardiac or intrapulmonary shunting of blood will result in changes to the measured variables compares well to indicator dilution techniques in dogs and cats

Answer 5

CxO2 =1.36 x [Hb] x SO2 + 0.003 x PO2

Answer 6

- based on CO2 production - amount of CO2 expired is a function of cellular metabolism and CO driving blood from the tissues to the lungs - ETCO2 reflects changes in perfusion (CO) relative to changes in inspired CO2 - also considers pulmonary shunt fraction by comparing inspired oxygen to arterial oxygen saturation CO=Difference in CO2 elimination and end-tidal CO2 Difference in ETCO2 between rebreathing and non-rebreathing Downsides: - need to be intubated - more accureacte if on MV - volume of the rebreathing circuit limits the size of patient on which it can be used Gunkel et al (JVECC 2004) ound good agreement and correlation using this method when compared with an indicator dilution technique Yamashita et al (J Vet Med Sci 2007) found significant bias

Answer 7

- injection of a known quantity of a marker (cold saline, lithium) at one location and subsequent measurement at a remote location - curve is generated reflecting the change in concentration over time - area under that curve is inversely proportional to CO, as a higher CO state will result in faster dilution of the indicator and a smaller curve 2 possibilites: - measurement in the pulmonary artery after injection into the RA - transpulmonary: injection in venous circulation with detec- tion downstream in the arterial circuit

Answer 8

Swan Ganz catheter is placed through the jugular vein and has a therm- istor tip that terminates in the pulmonary artery fixed amount of cold saline is injected through the proximal port that will mix in the RA and eventually pass through the PA to be detected by the thermistor conflicting evidence whether the use of PACs in clinical decision making has any beneficial impact on patient outcome

Answer 9

1. fluoroscopy 2. detection of pulmonary artery pressure waveform

Answer 10

- pulmonary thromboembolism - pneumothorax - blood- stream infections

Answer 11

- indicator: temperature - administering cold saline into venous circulation, with detection by a thermistor-tipped arterial catheter (femoral artery) - comparable CO determination compared with PAC in humans and lithium dilution in dogs

Answer 12

- indiator: lithium - administering lithium into a central or peripheral vein and then measuring arterial lithium levels (e.g., dorsal metatarsal) and using a peristaltic pump to draw blood across the lithium sensor - good correlation between lithium dilution and thermodilution, even in circumstances of varying hemody- namic states Limitations: - cost of equipment - lithium accumulation (especially in smaller patients) - amount of blood needed to be withdrawn across the lithium sensor

Answer 13

- beat-to-beat CO assessment - utilize area under the pressure waveform and mathematical models to account for differences in vascular compliance to calculate CO - some sytems require repeated calibration with lithium dilution (PulseCO) or transpulmonary thermodilution (PiCCO) - reasonable correlation between thermodilution and PiCCO - femoral arterial catheter necesssary for PiCCO - other studies failed to show good correlation or trending between CO measured by thermodilution or lithium dilution and any of these systems (tendency to overestimate CO in low output states + underestimate in high output states - algorithms are based on people)

Answer 14

- blind assessment of aortic or pulmonic flow velocity waveforms across the chest via Doppler ultrasound --> in conjunction with the vessel cross-sectional area --> determination of SV --> multiplied by HR = CO USCOM: continuous-wave spectral Doppler probe is placed over the thoracic inlet (for aortic flow) or below the xyphoid (for pul- monary artery flow) device has an algorithm (based on people) to provide vessel cross-sectional area relative to body surface area animals: direct determination of this value must be made using echocardiography + manually entered - CO measurements exceeded the limits of agreement, but overall trended with hemodynamic changes when compared to thermodilution

Answer 15

1. measurement of flow velocity in the RV outflow track and aortic diameter --> product of these two = SV --> multiplied by HR = CO 2. determination of LVEDV and LVESV --> difference between these two values = SV --> multiplied by HR = CO - strong correlation when compared with CO determined by thermodilution or cardiac MRI Limitations: - extensive training - no real-time assessment

Answer 16

- based on notion that the time from cardiac contraction to the generation of a pulse is inversely related to CO (the longer the time, the smaller the CO) - PWTT can be measured as the time from the electrocardiogram R-wave peak to the rise point of the pulse oximeter waveform (the point at which 30% of the peak height is achieved) - proprietary software necessary - needs to be calibrated against another CO measurement (e.g. lithium or thermodilution) - PWTT has shown the ability to detect changes in CO, though limits of agreement in comparison to reference CO measurement were beyond acceptable range