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What is Intraoperative Fluid Management (IOFM)?

IOFM is the act of optimising the patient’s fluid balance during surgery. The maintenance of adequate blood volume is essential for the delivery of oxygen to the tissues.

Why is IOFM Important?

Up to 70% of patients may exhibit hypovolaemia (a reduced circulating blood volume) at the beginning of surgery [1].  The body responds to hypovolaemia by reducing blood flow to some organ systems (i.e. the gut). While this ensures adequate supply is maintained to the vital organs (i.e. the heart and brain), decreased blood and oxygen supply to the gut can cause tissue necrosis. In turn this can trigger the leakage of bacteria and toxins from the gut into the bloodstream. These events can result in postoperative complications ranging from nausea and vomiting to multiple organ failure [2,3].

By optimising a patient’s blood flow (called Stroke Volume Optimisation) during surgery, postoperative complications attributed to hypovolaemia may be avoided. Indeed IOFM is a crucial factor for prevention of occult hypovolaemia and subsequent end organ dysfunction.

Can IOFM improve surgical outcomes?

A large evidence base supports IOFM, with outcomes being improved by use of accurate, real-time control over haemodynamic status. Deltex’s ODM and ODM+ systems guide interventions that prevent complications resulting from abnormal or undesired fluid levels (hypovolaemia or hypervolaemia) in the operating theatre and critical care areas.

Oesophageal Doppler technology provides the anaesthestist with the capability to manage an individual patient’s perioperative fluid and cardiovascular status in real time and with unparalleled accuracy. The consequence is fewer complications, reduced morbidity and shorter length of stay.

IOFM is now a vital element of any Enhanced Recovery Programme and is one of six High Impact Innovations as identified by the UK’s NHS in its 2011 Innovation, Health and Wealth initiative.

ODM is the only technology to consistently demonstrate reductions in postoperative complications and length of hospital stay when used to guide IOFM. See the Evidence Table for a summary of IOFM outcome studies.

 1. Bundgaard-Nielson, M. et al, Functional intravascular volume deficit in patients before surgery, Acta Anaesthesiol Scand, 2010. 54(4): p.464-9.
2. Deitch, EA, The role of intestinal barrier failure and bacterial translocation in the development of systemic infection and multiple organ failure, Arch Surg, 1990. 125(3): p.403-4.
3. Fiddian-Green, RG, Splanchnic ischaemia and multiple organ failure in the critically ill, Ann R Coll Surg Engl, 1988. 70(3): p.128-34.


The ODM+ system is designed to allow clinicians to guide fluid and drug administration during major and high risk surgery. The monitors are clinically proven and used to guide Fluid Management, reduce postoperative complications; critical care admissions, critical care stay, length of hospital stay and costs. Deltex Medical’s oesophageal Doppler monitoring is the only fluid management technology to be awarded with UK NICE recommendation (MTG3).

10% Stroke Volume Optimisation

In its simplest form, Stroke Volume Optimisation (SVO) is defined as the administration of fluid, most often a colloid, guided by an algorithm to normalise Stroke Volume without the risk of fluid overload. The 10% SV change algorithm for SVO utilises the Frank-Starling law, which established the relationship between left ventricular stroke volume and left ventricular end diastolic volume.


Above: Treatment algorithm suggested by Professor Mervyn Singer, University Hospital, London.

Only ODM has the precision necessary to guide successfully a 10% Stroke Volume Optimization (SVO) protocol. Its considerable evidence base is testimony to the unique ability of ODM to recognise and monitor 10% changes in Stroke Volume.

Real-time Haemodynamic Monitoring for Optimal Patient Outcomes

All patients undergoing surgery are at risk from serious and potentially life-threatening complications caused by a reduction in circulating blood volume. This condition, known as Hypovolaemia, results from the combined effects of preoperative fasting, the anaesthetic agent and the blood lost during the surgical procedure. In many respects hypovolaemia can be thought of as akin to severe dehydration.

The complications that hypovolaemia causes arise because the reduced circulating blood volume is unable to carry sufficient oxygen to the major organs and tissues. All of these systems are at risk of failure as a consequence of the resultant oxygen deprivation.

ODM+ monitors the flow of blood leaving the heart with every beat as it happens and consequently can detect any reduction in circulating blood volume early and in real-time. This allows the anaesthetist to intervene quickly and safely to correct the situation, using a combination of specialized fluids and drugs, before the hypovolaemia becomes serious and potentially life threatening.

The technique of optimising a patient’s haemodynamic status in this way, by giving the right amount of the right fluid at the right time, is known as Fluid Management.

Using the ODM+ to monitor and manage a patient’s circulating blood volume during surgery helps them to recover more fully and more quickly. Using the ODM+ means that fewer patients need to go to intensive care and those that do tend to stay there for shorter periods. Because patient journeys through the hospital are more predictable and because fewer patients unexpectedly need intensive care support, the ODM+ can play an important part in improving the efficiency and productivity of any healthcare system.


The benefits of a comprehensive Enhanced Recovery programme have been demonstrated in numerous specialties, as follows: Colorectal, endocrine, gynaecological, urological, vascular and orthopaedic surgeries.

Enhanced Recovery principles and protocols are now considered to be a standard of care in many surgical specialties with further studies also being carried out in: emergency surgery, AAA, oesophago-gastric, lung, liver, pancreatic and caesarean sections.

ODM and Enhanced Recovery

Intraoperative Fluid Management using oesophageal Doppler monitoring is a vital element of Enhanced Recovery and has been well validated within the accepted protocol. In the UK, it is supported by the  Enhanced Recovery Partnership in line with the National Institute of Clinical Excellence (NICE) Guidance MTG3, the NHS Operating Framework 2012/13 and the Department of Health Innovation Health and Wealth Review, 2011.

In Europe, ODM was chosen by the Enhanced Recovery After Surgery (ERAS) group, stating that ‘Oesophageal Doppler ultrasonography was chosen as the preferred method of monitoring intraoperative stroke volume due to the broader evidence base in this context’.

Which patients?

The following list identifies the surgical patients who should receive ODM, as recommended by the Enhanced Recovery Partnership:

  • Major surgery with a mortality rate of >1%.
  • Major surgery with an anticipated blood loss of greater than 500mls.
  • Major intra-abdominal surgery.
  • Intermediate surgery in high-risk patients, including patients aged >80 years.
  • Unexpected blood loss and/or fluid loss requiring >2 litres of fluid replacement.
  • Patients with ongoing evidence of hypovolaemia and/or tissue hypoperfusion.

Monty Mythen, Clinical Lead for the Department of Health’s Enhanced Recovery Partnership Programme & Professor of Anaesthesia & Critical Care at University College London said:

“I have worked with ODM for almost two decades and have seen the benefits in my patients.  By offering a much less invasive method of fluid management during and after surgery, ODM helps patients recover more quickly.  I am delighted that this guidance has highlighted the advantages of this technology, and I hope that it gives the NHS the impetus it needs to ensure better access for all.”  March 2011

Download Enhanced Recovery brochure using ODM

The ODM+ monitor is designed to allow clinicians to guide fluid and drug administration during critical care. The monitor is highly responsive in tracking changes in Stroke Volume and so Cardiac Output during intervention.

Only oesophageal Doppler has been shown to have the precision to drive the 10% Stroke Volume Optimisation algorithm, widely acknowledged as the basis for Fluid Management.

Additionally ODM+ has a Pulse Pressure Waveform (PPWA) mode which is quickly and easily calibrated from the Doppler signal, providing continuous monitoring for postoperative and medical patients in Critical Care. In sedated patients the PPWA algorithm can be recalibrated at any time from the Doppler waveform.

Treatment algorithm suggested by Professor Mervyn Singer, University Hospital, London.


The ODM+ is the world’s first dedicated paediatric cardiac function and fluid status monitor, to measure both flow and pressure.

ODM+ can be safely used to guide fluid management and monitor haemodynamic changes in paediatric patients, using the minimally invasive paediatric Doppler probe (KDP72), placed orally in sedated or anaesthetised patients. The optional connection of an arterial line for pressure monitoring mode is now available, offering quick, easy calibration at the touch of a button.

Designed for surgical and intensive care applications, ODM+ and the paediatric probe can be utilised in the following instances:

  • Sepsis
  • Major abdominal surgery
  • Laparoscopic surgery
  • Transplant procedures
  • Cardiac procedures
  • Trauma procedures
  • Spinal surgery

A paediatric specific nomogram, based on patient height, takes into consideration the unique anatomy and physiology of the paediatric population. As with adult patients, the calibrated Pressure Monitoring Mode allows for extended continuous monitoring in paediatric patients.

The ODM+ and paediatric probe are suitable for patients:

  • ≥ 3kg
  • ≥ 50cm tall
  • < 16 years old

For a list of studies validating the ODM in paediatric patients, click here

To access the Paediatric e-Learning module, click here

Paediatric Case Studies using the CardioQ-ODM+

Postoperative Warming

Covert Haemorrhage and Response to Fluid

Screenshot 1

3 year old child. Wt 15 kg (33 lb), Ht 108 cm (42.5 in), BSA 0.67m2. Intraoperative. Laparotomy and resection of abdominal neuroblastoma. General anaesthetic used and ventilated.

3yr s1A good clear Doppler signal is defined by the tidy green line around the waveform, orange/white around waveform edge (more white along downslope) with a dark center and correct arrow placement. Gain was adequate.

At this point in surgery, CI, FTc and PV had reduced from previous results possibly indicating an increasing afterload, yet the urine output and BP remained stable.



Screenshot 2

Wh3yrs s2ilst monitoring the child, 5 minutes later, the results continued to deteriorate, and blood was then seen in the suction canister. SV, FTc, PV and CO/I decrease suggesting further increase in afterload probably as a result of compensation to the drop in preload, together with an increase in HR. The waveform has also become smaller in height and width. BP at this point had also started to decrease. Fluid was given, Hb checked and a blood transfusion commenced.


Screenshot 3

Half a3yrs s3n hour later following fluid and blood, SV, FTc, PV and CO/I have increased as preload increased as well as a reduction in afterload. HR has also reduced and the waveform has increased in height and width.




In this scenario, the ODM+ indicated covert bleeding.

The ODM+ is the only technology precise enough to see small changes in flow. Flow is very responsive to changes in circulating blood volume, whereas pressure can often be maintained due to compensation. Hypovolaemia is unlikely to be missed when flow is measured by the ODM+ because of its superior precision. Fluid can then be given safely in small amounts, thus preventing over or under filling of the patient.

Abbreviations: BP – blood pressure. BSA – body surface area. CO/I – cardiac output/index. CVP – central venous pressure FTc – flow time corrected. HR – heart rate. Ht – height. IV – intravenous. ODM+ – oesophageal Doppler monitor. PV – peak velocity. SV/I – stroke volume/index. Wt – weight.

Postoperative Trauma

Screenshot 1

14 year old child. Wt 30 kg (66 lb), Ht 151 cm (59.5 in), BSA 1.10 m2. Multiple trauma following road traffic accident – suffered massive haemoperitoneum, chest trauma with pneumothorax, facial and abdominal trauma. Postoperative monitoring in intensive care following facial suturing, splenectomy and exploration of blunt trauma to liver. Ventilated and sedated.

A good 14yrs s1clear Doppler signal is defined by the tidy green line around the waveform, orange/white around waveform edge (more white along downslope) with a dark center and correct arrow placement. Gain was adequate.

BP at this stage was reduced. FTc is reduced probably indicating an increased afterload – the most common cause being hypovolaemia. The clinician gave a rapid fluid challenge.

Screenshot 2

Follo14yrs s2wing a fluid challenge, the SV has increased by more than 10% indicating fluid responsiveness. CO/I is unchanged, but FTc has also increased indicating a reduction in afterload. Further fluid was then given.



Screenshot 3

SV i14yrs s3ncreased again by more than 10%. FTc, PV and CO/I also increase while HR reduces.

BP however remained low and a dose of epinephrine was then given.



Screenshot 4

Foll14yrs s4owing the epinephrine, flow results continue to increase and BP also increased.






The ODM+ can be used safely to assess cardiac function and how it responds to interventions. It is the only technology precise enough to see small changes in flow. Flow is very responsive to even small changes in circulating blood volume as well as changes in arterial compliance.

Abbreviations: BP – blood pressure. BSA – body surface area. CO/I – cardiac output/index. CVP – central venous pressure FTc – flow time corrected. HR – heart rate. Ht – height. IV – intravenous. ODM+ – oesophageal Doppler monitor. PV – peak velocity. SV/I – stroke volume/index. Wt – weight.




Recommended by NICE

NICE released its recommendation on the CardioQ-ODM on 30 March 2011. 

Evidence-based recommendations and conclusions:

  • CardioQ-ODM specific recommendation
  • For major and high-risk surgery
  • Reduces post-operative complications
  • Shortens length of stay
  • Saves £1,100 per patient

The case for adopting the CardioQ-ODM in the NHS,…is supported by the evidence…The CardioQ-ODM should be considered for use in patients undergoing major or high-risk surgery or other surgical patients in whom a clinician would consider using invasive cardiovascular monitoring. This will include patients undergoing major or high-risk surgery or high-risk patients undergoing intermediate-risk surgery.

NICE, 2011

See NICE for further information.