Frequently Asked Questions
1. What is the science underlying the LiDCOplus Hemodynamic Monitor?
The plus Hemodynamic Monitor hosts the complementary LiDCO & PulseCO softwares and collectively provides a real time and comprehensive assessment of a patient's hemodynamic status.
The LiDCO System is a bolus indicator dilution method of measuring cardiac output and calibrating the PulseCO software. A small dose of lithium chloride is injected via a central or peripheral venous line; the resulting arterial lithium concentration-time curve is recorded by withdrawing blood past a lithium sensor attached to the patient's existing arterial line. In terms of accuracy, clinical studies have demonstrated that the LiDCO System method is at least as accurate as thermodilution over a wide range of cardiac outputs and in patients with varying cardiac outputs.1,4-8 The dose of lithium marker needed (0.15 - 0.3 mmol for an average adult) is very small and has no known pharmacological effects.2,3
The PulseCO System software calculates continuous beat-to-beat cardiac stroke volume, stroke volume variation & cardiac output by analysis of the arterial blood pressure trace following calibration with an indicator dilution cardiac output measurement. This system has been shown to be accurate and reliable in the peri-operative and ICU settings. It has also been shown that a check on the calibration is required only every 8 hours and that the software can track changes in cardiac output even in the presence of moderately damped arterial lines.10-14
2. What are the primary indications for use of the LiDCOplus Hemodynamic Monitor?
The LiDCOplus Hemodynamic Monitor is intended for monitoring continuous blood pressure and cardiac output in patients with pre- existing peripheral arterial line access. The system is safe, accurate and easy to use.10-14 In acute care settings, where information on real time hemodynamic changes are required, the LiDCOplus Monitor can be set up in five to ten minutes by a trained nurse or doctor. It can be used on a conscious patient and used in pre-inter-and post-operative situations. The primary indications for use include: peri operative care of cardiac surgery and high risk surgical patients, acute heart failure, sepsis, drug intoxication, acute renal failure, severe hypovolemia, fluid shifts, complex circulatory situations & medical emergencies.
3. What are the common secondary indications for its use?
The LiDCOplus Hemodynamic Monitor provides a rapid response 'Early Warning' of a significant change in the hemodynamic status. Thus in patients who are conventionally indicated for invasive arterial blood pressure monitoring, the device is intended as a more sensitive way of displaying continuous hemodynamic data. In addition to arterial blood pressure parameters and cardiac output, the LiDCOplus Hemodynamic Monitor calculates a number of other parameters: Body Surface Area, Systolic Pressure Variation, Pulse Pressure Variation, Cardiac Index, Stroke Volume, Stroke Volume Index, Stroke Volume Variation, Systemic Vascular Resistance, Systemic Vascular Resistance Index. It has been shown that for fluid management the measurements of pulse pressure variation and stroke volume variation can be most useful in closed chest mechanically ventilated patients.15-37 These 'preload' measurements benefit from being dynamic, real time and available in a minimally invasive manner. One recent paper in Anaesthesia and Analgesia showed that "a SVV value of 9.5% or more, will predict an increase in the SV of at least 5% in response to a 100ml volume load, with a sensitivity of 79% and specificity of 93%." 22
4. What are the efficacy data to support its use?
The LiDCOplus Hemodynamic Monitor has been shown to be accurate and reliable in various clinical settings.10-14 These studies include cardiac surgery patients undergoing bypass and off-pump procedures where cardiac output is rapidly changing and has ranged from 2.7 - 21.3 litres.13 Data has also been presented validating its use in the medical intensive care unit with patients having a variety of diagnoses and the cath lab.14,9 It is clear that this system provides no incremental risk to the patient and could reduce the requirement for more invasive monitoring in many risk patients.10-14
5. Are there any appropriate outcome data available?
There is a growing volume of evidence to suggest that optimising flow (cardiac output) and oxygen delivery (DO2) can lead to improved outcomes in terms of mortality and morbidity in suitable patients.38-41 The LiDCOplus Hemodynamic Monitor allows the patients hemodynamics to be 'optimised' in a safe, accurate and timely manner. In particular the ability to use the product in a non-ventilated and conscious patient facilitates the implementation of peri operative optimisation protocols in high risk surgical patients.
6. What are the costs of using the technology?
In order to use the technology, a monitor (LiDCOplus) and single patient use lithium dilution sensor and associated disposables are required. It is designed to work with any of the commonly used arterial catheter systems. The indicator dilution calibration method does not require the use of special catheters, introducer trays or a subsequent x-ray for catheter position verification. Savings can usually be realised against the costs associated with the use of more invasive continuous technologies.
7. Are there any contraindications for the use of this technology?
The LiDCOplus Hemodynamic Monitor is suitable for patients who have arterial and venous catheters (peripheral or central) inserted and who require hemodynamic monitoring. Patients undergoing treatment with lithium salts, patients who are less than 40kg (88lb) in weight and patients in the first trimester of pregnancy are contraindicated for calibration with the lithium chloride indicator. Performance of the continuous waveform analysis PulseCO software may be compromised in patients with severe peripheral arterial vasoconstriction, those undergoing treatment with aortic balloon pumps and in the case of aortic valve regurgitation.
8. What is the current status of this technology?
The technology has FDA clearance and CE mark approval and has been actively marketed since July 2001 in the USA and UK. In continental Europe lithium approval (as an in vivo diagnostic) was received for Germany, Italy, Spain, Holland, Belgium and Austria in January 2003. The use of minimally invasive hemodynamic monitoring is receiving widespread acceptance in the market place with over 70 key institutions in the US and UK now routinely using the LiDCO technology.
9. Do muscle relaxants prevent me from using the LiDCOplus?
No you can use the LiDCOplus as long as the calibration is performed prior to paralysis or after waiting for a short time after their use (see below).
10. How do muscle relaxants interact with the LiDCOplus?
Muscle relaxants only impact the Lithium Chloride indicator dilution determination of the LiDCOplus. Depolarising and non-depolarising muscle relaxants have a positively charged ion (quaternary ammonia ion) that can be detected by the LiDCO lithium sensor.
11. How does this affect the LiDCOplus?
The presence of this ion may result in a greater overall response by the sensor and/or potentially reduce its operating range.
12. Will the LiDCOplus detect this?
The software is designed to eliminate a certain amount of background signal and/or drift that is caused by muscle relaxants. The impact on accuracy depends on the particular muscle relaxant used and how recently it was given.
In some cases the LiDCO will calculate the cardiac output, however, if the drift is large the CO may be overestimated. Likewise, if the sensor operating range is reduced a lower signal value is received and again the CO may be overestimate. It is best to match the LiDCO with a compatible muscle relaxant and follow the recommendations below.
13. Which muscle relaxants are compatible with the LiDCOplus?
Wait 5-10 minutes to perform a LiDCO calibration following a bolus
Wait 15 minutes to perform a LiDCO calibration following a bolus
Wait 15-30 minutes to perform a LiDCO calibration following a bolus. For constant infusion patients, the LiDCO calibration has been reported to have been successful
Note: liver or renal failure may increase the wait time.
14. Which muscle relaxants are NOT compatible with the LiDCOplus?
Anecdotal experience with constant infusion of Atracurium has resulted in successful calibration. Atracurium is a member of the Benzyl family that includes Cisatracurium, Doxacurium and Mivacurium, all of which may work better with the LiDCOplus (see below).
Rocoruonium is a member of the aminosteroids family that includes pancuronium and vecuronium, both of which will work after sufficient delay (15-30min).
Note: Both these usually cause problems with drift due to large doses given and plasma concentration required for paralysis – plasma levels can also take a long time to fall following infusions. This time may be increased by liver or renal impairment.
15. Are there other muscle relaxants to consider?
Yes, the following have not been tested specifically, however, you should be aware of them.
Dose and pharmacokinetics suggest that this may be usable with the sensor. Possibly the muscle relaxant of choice for chronic paralysis in the ICU due to its low dose & Hoffman elimination
This looks like it may be a good candidate for intra operative use via bolus administration
Possibly could be used as a constant infusion