Cardiac Output Monitoring FCCNC 2018 Hajni Hideg Practice Educator St George’s Hospital Cardiothoracic Intensive Care Unit

Learning objectives By the end of the session learners will be able to: State the indications for invasive flow monitoring in the critically ill patient. Define the determinants of blood pressure and describe how these factors are interpreted and optimized to support the cardiovascular system. Name 3 equipment types used for flow monitoring. Explain the definition of oxygen delivery, oxygen consumption, SvO2 and ScvO2.

How CO monitoring helps us? The aim of haemodynamic monitoring and support is to optimise oxygen delivery and provide adequate perfusion to the tissues. Oxygen delivery is determined by CO (flow)  need to maintain flow not just BP! Inadequate flow leads to organ dysfunction, multiple organ failure and death Early detection of this is vital CO monitoring allows us to assess flow of blood to the tissues, and provides information on how best to support a failing circulation. (Alhashemi JA, et al.: Cardiac output monitoring: an integrative perspective. Critical Care 2011, 15:214.)

Indications/use of CO monitoring Early detection of problems Provision of additional information (Can measure CO,CI,SV, SVR, DO2, SVO2) Diagnosis To guide or limit therapeutic interventions Check response to treatment Deterioration, new cardiovascular instability

Pressure, Volume & Flow Combination of all 3 ensure perfusion to all areas! Blood pressure Cardiac output or index - flow CO = Stroke volume x HR Determinants of Blood pressure: BP=CO x SVR

Cardiac Output Cardiac Output Heart Rate Stroke Volume Preload Afterload Contractility

Approaches & Devices LiDCO (Lithium Dilution Cardiac Output) Oesophageal Doppler PAC (Pulmonary Artery Catheter) There are more!

Lithium Dilution Cardiac Output (LIDCO) Uses a small dose of Lithium as an indicator to directly measure CO as the device is calibrated. PulseCo uses pulse pressure analysis of the arterial waveform to derive CO, this is adjusted for the individuals physiology when the device is calibrated Lithium can be injected into peripheral vein via a large bore cannula or CVC

PulseCO Monitor Beat-to-beat changes CO/CI Mean Arterial Pressure SVR & SVRI Stroke Volume Heart Rate DO2 & DO2I

The PA catheter: the ‘gold standard’ ? Dr HJ Swan & Dr W Ganz N Engl J Med (1970) 283: 447-451 Syringe (plunger withdraws only to 1.5ml) introducer with side port (acts as a rapid infuser) Sliding locking device Markings designating distance from tip (each broad mark represents 10cm) Connectors to monitor 8 French PVC yellow catheter Lumens Temperature sensitive wire with thermistor bead Balloon surrounding tip-containing lumen in end

Where it sits?

PA catheter Cont. cardiac output monitoring, measurement of SV, SVR, PVR (all values indexed) Central/core temperature monitoring measurement of PA pressure (can also measure RA and RV pressures during insertion) measurement of mixed venous saturations (SvO2) estimation of diastolic filling of left heart (normal PCWP 2-12mmHg) Settings it is commonly used are: RV/LV failure pulmonary hypertension weaning failure of cardiac origin post-cardiac surgery

Normal values CO 4-8 L/min SV 60-130 ml PA Syst 15-25 mmHg PA Diast 6-12 mmHg PAOP 4-12 mmHg SVR 770-1500 dyne/sec/cm-5 PVR 20-120 LVSW 58-104 gm/beat RVSW 8-16 gm/beat DO2 900-1000 mlO2/min VO2 200-290 mlO2/min CI 2.5-4.2 L/min/m2 SVI 30-65 ml/beat/m2 SVRI 1680-2580 PVRI 69-177 LVSWI 50-62 RVSWI 5-10 DO2I 550-650 VO2I 115-160 SvO2 65-75% Darovic G (2004) Handbook of Haemodynamic Monitoring Saunders (Elsevier)

Trans-oesophageal Doppler The Doppler probe is passed into the oesophagus (approx 35cm from lips) The probe is rotated until the transducer faces the descending aorta and a characteristic waveform is seen. By using an ultrasound probe to visualise directional blood flow, the phase shift This, together with the cross-sectional area of the blood vessel being observed can be used to determine flow.

Perfusion / Oxygen Transport A primary function of cardiopulmonary system is to provide sufficient oxygen delivery to maintain normal tissue and organ function O2 Delivery (DO2) The amount of O2 (ml) pumped out by the heart & available to the body per minute Depends on: Pulmonary gas exchange, Hb levels, Binding of O2 to Hb, CO O2 Consumption (VO2) The total amount of O2 consumed by the body per minute Function of: cellular demand of oxygen, adequacy of O2 delivery, ability of cell to extract O2 from blood

SvO2 / ScvO2? In simple terms, it is the oxygen saturation of the blood returning to the right side of the heart. The amount of oxygen “left” after the tissues utilize what they need What? SvO2 = Mixed oxygen saturation, measured in PA ScvO2 = Central venous oxygen, measured in SVC When? SvO2 = used with a PA catheter ScvO2 = use CVC

SvO2/ ScvO2 Rise Drop Causes: VO2 DO2 Stress Pain Fever Shivering  PaO2  Hb  Cardiac output  DO2 VO2  PaO2  Hb  Cardiac output Hypothermia Sedation