PiCCO

OVERVIEW

  • PiCCO

COMPLICATIONS

  • usual arterial line complications
  • cold fluid in haemodynamically unstable patients – volume and temperature effects

OTHER INFORMATION

  • Inaccurate measurements if the following are present:
  • intracardiac shunts
  • aortic aneurysm
  • aortic stenosis
  • pneumonectomy
  • in the presence of a balloon pump and in unstable arrhythmias
  • Need to calibrate in unstable patients and after changes to management occur that could affect haemodynamics.

USE

  • haemodynamic monitoring

DESCRIPTION

  • PiCCO catheter = arterial line with a thermistor on the end
  • provides complete haemodynamic monitoring by combining  pulse contour analysis to provide a continuous display of cardiac output using a modified version of Wesseling’s algorithm combined with a transpulmonary thermodilution technique.
  • pressure transducer
  • PiCCO Monitor

METHOD OF INSERTION/ USE

  • insert a central line
  • place PiCCO into a large artery, usually the femoral (axillary is an alternative)
  • attach PiCCO via a pressure transducer to the PiCCO monitor
  • enter patient details prior to calibration
  •  administer a known volume of cold normal saline via central line injection port
  • PiCCO detects temperature difference and generates a dissipation curve to which the Stewart Hamilton equation is applied to calculate CO.
  • Other measures generated include:
    —  preload: global end-diastolic blood volume (GEDV) and intrathoracic blood volume (ITBV)
    — extravascular lung water (EVLW) which is a sensitive indicator of pulmonary oedema.
    — arterial BP, HR, stroke volume (SV), systemic vascular resistance (SVR), and cardiac function index (CI).
  • decision trees is provided with PiCCO to help interpret these parameters in terms of haemodynamic status

Thermodilution

  • calibration technique
  • cold or room temperature saline bolus -> measured by arterial thermister
  • temperature change vs time plotted
  • parameters derived:

Cardiac output (Q) and cardiac index (CI)
Global end-diastolic volume (GEDV) – all four chambers
Global ejection fraction – ratio of 4 stroke volumes divided by GEDV (can detect ventriclular dysfunction)
Intrathoracic blood volume (ITBV) – volume in heart + pulmonary vessels
Extravascular lung water (EVLW) – water content in lungs

Arterial pulse contour analysis

  • ongoing measurement -> providing continuous beat-by-beat parameters obtained from shape of arterial pressure wave.
  • parameters derived:

Pulse continuous cardiac output (PCCO)
SVR
Stroke volume variation (SVV) – sensitivity of heart to cyclic changes in preload induced by respiration.
dPmax – slope of pressure vs time trace = closely approximates contractility of LV

Central Venous Oximetry

  • measures ScvO2 by spectrophotometry
  • displayed continuously

OTHER INFORMATION

Summary of useful values and normal ranges

Q = SV x HR

SV – preload, afterload and contractility

Preload

Global end-diastolic index (GEDI) – 680-800mL/m2
Intra-thoracic blood index (ITBI) – 850-1000mL/m2
Stroke volume variation (SVV) – 3.0 L/min/m2

Afterload

Systemic vascular resistance index (SVRI) – 1700-2400 dyn.sec.cm-5.m2

Heart function/Contractility

Cardiac index (CI)/Pulse contour cardiac index (PCCI) – 3.0-5.0L/min/m2

Global ejection fraction (GEF) – 25-35%

Lung Function

Extra vascular lung water index (ELWI) – 3-7mL/kg

Oxygen Delivery

ScvO2 – 70-80%

Summary of Haemodynamic Goals

  • CI > 3.0 L/min/m2
  • appropriate preload: GEDI of 700-800mL/m2 or ITBI of 850-1000mL/m2 or SVV < 10%
  • minimal extra vascular lung water: ELWI 3-7mL/kg
  • ScvO2 70-80%

Advantages of PiCCO

  • transpulmonary thermodilution (vs only right sided thermodilution)
  • less invasive
  • dynamic continuous measurement
  • also measures extra-vascular lung water
  • can stay in patient for up to 10 days (unlike PAC – 72 hours)
  • no CXR required
  • claimed to be cheaper
  • patients usually already require a CVL and arterial line
  • ITBV and GEDV are better indicators or preload than CVP and PCWP and not influenced by mechanical ventilation
  • EVLW shown to have clear correlation in severity of ARDS, number of ventilator days, ICU duration and mortality

Disadvantages of PiCCO

  • cannot be used with an intra-aortic balloon pump
  • should be recalibrated with changes in position, therapy or condition to account for compliance of vascular bed.
  • in obese patients, EVLW underestimated as related to weight of patient (use IBW)
  • EVLW only measured in parts of the lung that are perfused (underestimated post-pneumonectomy)
  • AAA raises GEDV and ITBB
  • severe AR may result in an inaccurate thermodilution wash out curve

Evidence

PiCCO vs Physician – Critical Care 2007 11 (suppl 2), page 283

  • EVLW and GEDV vs clinical exam, CVP and CXR -> leg oedema and increased CVP does not exclude underfilling and is a poor predictor of EVLWI

-> EVLW associated with audible crepitations
-> ELW underestimated by CXR

PiCCO vs PAC – Uchino and Bellomo – Critical Care 2006, 10: R174

  • MRCT
  • 4 countries
  • 342 catheters (PiCCO 192, PAC 150)

-> PiCCO associated with greater positive fluid balance and fewer ventilator-free days
-> no major influence on outcomes
-> positive fluid balance significant predictor of hospital mortality (independent of type of monitoring used)

References and Links

  • Alex Psirides’ Presentation (2011)
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