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Frequently Asked Questions


How easy is it to use ODM?

The majority of new ODM users find the product easy to handle, place and manipulate the probes. Evidence suggests it takes up to 12 probe insertions to become competent, The manufacturer’s surveillance reports show that in more than 90% of cases, it takes less than two minutes to get a first good signal. In a typical major operation, of 3-4 hours duration, the total time spent interfacing with the monitor and probe is between three and four minutes.

Does ODM lead to excessive or inadequate fluid?

Individualised Doppler guided fluid management tailors the amount of fluid to the individual patient at any given time under various anaesthetic or sedation strategies. The goal is to ensure the patient receives the correct volume of intravascular fluids at the correct time.

Is the ODM safe?

ODM has been used in over 400,000 patients worldwide. To date, there have been no serious adverse events associated with ODM. In all, eight potential adverse incidents have been reported, however after investigation none of the eight were attributed to ODM use. The manufacturer’s instructions for use lists the contraindications. In summary, particular care should be taken in patients known to have existing oesophageal disease or injury or where multiple devices are placed in the oesophagus at the same time.

Can ODM be used in Paediatrics?

Yes. There are dedicated paediatric probes available (KDP), suitable for children of 3kg and above. A paediatric specific nomogram is integrated into the ODM and ODM+ monitors. The Adult nomogram should not be used for children.

Are the probes reusable?

No. The DPn and I2n range of probes are all Single Patient Use and are labelled accordingly.

Can ODM be used in awake patients?

The I2n range of probes are designed to be placed in unconscious patients (both anaesthetized and sedated) and then left in position after they wake up, providing the option to conduct post-operative fluid optimization. Experienced users also find these probes are well tolerated by fully conscious or lightly sedated patients. However, patients who are likely to attempt to dislodge other invasive devices, may also try to remove the ODM probe.

Can ODM be used at the same time as…?

  • Insufflation of the abdomen? Yes: ODM is unaffected by insufflation, however, changes in abdominal pressure and consequently venous return cause changes in blood flow in the descending aorta and therefore caution should be taken in interpreting these changes. Similar caution should be applied in the event of major positional change while awaiting the outcome of a fluid challenge (eg Trendelenburg).
  •  NG tubes? Yes: occasionally when using ODM with a nasogastric (NG) tube, you may notice a somewhat diminished intensity of signal. If it is in the path of the Doppler transmission, air in the NG tube can diminish the intensity of the Doppler signal (muted colours on screen). To avoid this, insert the probe before the NG tube, position the probe to the left of the already inserted NG tube, and/or flush the NG tube with saline.
  • Epidurals? Yes: however epidurals and spinal blocks cause different levels of vasodilation around the body and this may cause the derived values of stroke volume and cardiac output to change disproportionately. However, ODM’s ability to report changes and trends accurately and in the right direction is unaffected. If in doubt, manage the patient’s haemodynamics using Stroke Distance.
  • Diathermy/electro-cautery? Yes: certain models of diathermy equipment emit noise that can intermittently interfere with ODM probe, and may cause loss of signal on the monitor. If the noise is prolonged, then the average cycles per calculations can be reduced to maximize the data capture opportunity between the periods of diathermy.
  • Ultrasonic scalpels? Yes: no interference reported to date.
  • Vasopressors or vasodilators? Yes: ODM responds instantly to the effects of vasoactive agents.
  • MRI scanner? No: the probes contain a metal spring.
  • Defibrillators? Yes: ODM is insulated to protect both patient and machine. Best practice is to remove or disconnect the probe during defibrillation.