Invasive Haemodynamic Monitoring

Invasive haemodynamic monitoring is used in every critical care environment and as such the practitioner must have clear information, knowledge and understanding of the devices and how to use them safely. We can help you with this, just read on. Don’t forget to look at our other healthcare resources on our site.

How to assist in setting up for any invasive haemodynamic monitoring

Like all tasks in the workplace workplace safety needs to be adhered to with regards to invasive haemodynamic monitoring as follows:

  • Cleaning hands;
  • Putting personal protective equipment on, such as goggles, apron and gloves;
  • Ensuring that the patient is as the same height as the practitioner to reduce the risk of a workplace injury.

The invasive haemodynamic monitoring equipment needs to be set up correctly:

  • A bag of saline or mildly heparinised saline (for example 500 units in 500mls) should be hung with a transducer set spiked into the bag;
  • A pressure bag needs to be placed around the bag of saline / heparinised saline and inflated to a pressure around 300mmHg (this is done to overcome the systolic blood pressure and to stop blood traveling up the transducer line);
  • The fluid needs to be primed to the end of the transducer line, ready for connection to the patient.

How to set up the monitoring on the patient:

  • Once connected, the transducer needs to be zeroed to atmospheric pressure, which is done by turning the three way tap off to the patient and opening the air-port or bung to air;
  • Pressing “zero” on the monitor will accept the zero reference;
  • The bung can now be replaced and the three way tap turned off to the bung;
  • An invasive haemodynamic monitoring pressure reading should now display on the monitor.

Where should the invasive haemodynamic monitoring transducers be?

The level for keeping the transducer for the invasive haemodynamic monitoring is different for many lines:

  • An arterial line, central line, pulmonary artery catheter / pulmonary artery flotation catheter / swan-ganz catheter is kept at the phlebostatic axis, 4th intercostal space, mid axilla point, roughly at the middle of the heart;
  • For a neurological extraventricular drain (EVD) the transducer is kept at the tragus in line with the foramen of munro.

What are the normal values for invasive haemodynamic lines?

The normal values of invasive haemodynamic monitoring lines are flexible, but are roughly:

A couple of common invasive haemodynamic monitoring waveforms

A central venous or right atrial invasive haemodynamic monitoring waveform looks like this:

central venous invasive haemodynamic monitoring pressure tracing

  • The A wave represents atrial contraction;
  • The C wave represents the additional pressure placed on the right atrium from the tricuspid valve during right ventricular systole.
  • The X wave represents atrial relaxation.
  • The V wave shows the rise in the atrial pressure prior to the tricuspid valve opening
  • The Y wave shows the lowering of atrial pressure as the blood is emptied into the right ventricle.

Central venous lines or right atrial catheters are useful in assessing the patients fluid status along with a total patient assessment.

An arterial invasive haemodynamic monitoring pressure waveform looks like this:

arterial pressure invasive haemodynamic waveform

  • The A wave is the anacrotic limb, which is represents the left ventricular systole;
  • The B point is the arterial systolic blood pressure reading;
  • The C point represents the aortic valve closing;
  • The D point represents arterial diastole.

Complications of invasive haemodynamic monitoring

All lines have potential risks and invasive haemodynamic monitoring lines have greater risks due to their place to residence. Arterial line complications and risks include:

  • Reduced circulation to the distal limb;
  • Sepsis;
  • Haemorrhage;
  • Pain on insertion and during manipulation;
  • Nerve damage during insertion;
  • Thrombosis / emboli;
  • Inadvertent injection of intravenous medications.

Central lines, right atrial and right ventricular invasive haemodynamic monitoring lines have similar complications and risks:

  • Sepsis;
  • Haemorrhage;
  • Pain on insertion and during manipulation;
  • Thrombosis / emboli;
  • Air emblous.

Pulmonary artery catheter / pulmonary artery flotation catheter / swan-ganz catheter have similar complications / risks as the other invasive haemodynamic monitoring lines:

Pulmonary artery invasive haemodynamic catheter

  • Sepsis;
  • Haemorrhage;
  • Pain on insertion and during manipulation;
  • Thrombosis / emboli;
  • Air emblous;
  • Balloon rupture;
  • Pulmonary capillary necrosis.

Care needs to be taken with any invasive haemodynamic monitoring line with regards to the dressings and ensuring they stay intact and clean. They need to be cleaned aseptically as not to introduce any infection to the patient. Bleeding needs to be observed and attended to by either changing the dressings, applying pressure or additional suturing. Routine recording of the patients’ coagulation profile is also necessary in the presence of excessive bleeding from the site.

All of the invasive haemodynamic monitoring lines should be regularly re-zeroed to ensure that the calibration remains accurate and once the zero has been performed a close watch needs to be placed upon the placement of the transducers to ensure that the readings are accurate.

A mean arterial pressure of at least 60mmHg should generally be achieved to ensure perfusion to the kidneys, brain and other vital organs.

Should the pressures on the invasive haemodynamic monitoring alter significantly, troubleshooting should be undertaken and the figures themselves should not necessarily be believed without checking the position of the transducers, any kinking of the lines. A non-invasive blood pressure reading may help the clinician to establish if the arterial blood pressure reading is being inaccurate. Also a revision of the patients’ medications should also be undertaken to ensure that the drop or rise in blood pressure is not iatrogenic or caused by the clinician.

Further information and a free resource on arterial blood gas interpretation can be found here. Other healthcare resources are available on our site, please have a look and further increase your knowledge and patient care.

References
  1. Edwards Lifesciences LLC > Normal Hemodynamic Parameters – Adult 2009.
  2. Physiology (1999), Control of Systemic Circulation, Physiology, 10:3.
  3. Steiner LA, Andrews PJ (2006). “Monitoring the injured brain: ICP and CBF”. British Journal of Anaesthesia 97 (1): 26–38.
  4. Understanding blood pressure readings”. American Heart Association. 11 January 2011. Retrieved 30 March 2011.

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