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Fluid Optimization

Fluid Optimization

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 Hypovolemia, results from the combined effects of preoperative fasting, the anesthetic agent and the blood lost during the surgical procedure. In many respects hypovolemia can be thought of as akin to severe dehydration.

The complications that hypovolemia 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.

EDM 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 anesthetist to intervene quickly and safely to correct the situation, using a combination of specialized fluids and drugs, before the hypovolemia becomes serious and potentially life threatening.

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

Using the EDM+ to monitor and manage a patient’s circulating blood volume during surgery helps them to recover more fully and more quickly. Using the EDM+ 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 EDM+ can play an important part in improving the efficiency and productivity of any healthcare system.

Surgical

The EDM and EDM+ are 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. EDM is the only fluid management technology to be awarded with NICE Guidance (MTG3).

10% Stroke Volume Optimization

Stroke Volume Optimization (SVO) is in its simplest form 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.

Surgical_Fluid_Algorithm

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

Only EDM 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 EDM to recognize and monitor 10% changes in Stroke Volume.

Critical Care

The EDM and EDM+ are designed to allow clinicians to guide fluid and drug administration during critical care. The monitors are highly responsive in tracking changes in Stroke Volume and Cardiac Output during intervention.

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

Additionally the EDM+ 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.

Pediatrics

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

EDM+ can be safely used to guide fluid management and monitor haemodynamic changes in paediatric patients, using the minimally invasive pediatric 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, EDM+ and the pediatric probe can be utilized in the following instances:

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

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

The EDM+ and pediatric probe are suitable for patients:

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

Access the Pediatric brochure for further reading.

For a list of studies validating the EDM in pediatric patients, click here.

Pediatric Case Studies using the CardioQ-EDM+

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 anesthetic 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.

 

 

 

Summary

In this scenario, the EDM+ indicated covert bleeding.

The EDM+ 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. Hypovolemia 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. EDM+ – esophageal 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 hemoperitoneum, 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 hypovolemia. 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.

 

 

 

 

 

Summary

The EDM+ 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. EDM+ – esophageal Doppler monitor. PV – peak velocity. SV/I – stroke volume/index. Wt – weight.

 

Flow vs Pressure

Many different technologies have been used for Cardiac Output monitoring. However, the two most utilized are direct flow measurement using Doppler ultrasound and flow derived from mathematical algorithms using arterial blood pressure (ABP).

Direct flow measurement, by way of Doppler ultrasound, has the precision and responsiveness to guide Intraoperative Fluid Management (IOFM) using the clinically proven >10% change Stroke Volume Optimization (SVO) algorithm. Direct flow requires no additional calibration. Direct flow measurement by Doppler requires occasional focussing and in some scenarios, the signal is not always continuously available, making the technology less ideal for long term continuous monitoring.  However, the EDM+, which utilises both flow and pressure measurements, ensures continuous access to calibrated waveforms.

Pressure based technologies, using pressure as a surrogate for flow, have their limitations, particularly in periods of hemodynamic instability. Pressured based methods using ABP lines have been shown to be prone to drift due to changes in vascular tone, arterial compliance and the consequent arterial blood pressure variation. These changes have been reported to be clinically significant and prevent such devices from successful use of the >10% SVO algorithm. As a result, such devices offer Pulse Pressure Variation and/or Stroke Volume Variation as their modality for guiding intervention.

These parameters have significant limitations in use as they require the patient to be:

  • in sinus rythm;
  • fully mechanically ventilated;
  • tidal volume ≥7-8 mL/kg – higher tidal volumes elicit higher variations;
  • heart rate:respiratory rate ratio ≥4;
  • increasing PEEP results in higher variations;
  • changes in lung or chest compliance, or patient position and right ventricular dysfunction or abdominal insufflation may affect readings.

In periods where the patient has stable hemodynamics, pressure based technologies can be used to make a continuous record of cardiac output.

The direct flow Doppler EDM, is preferred for guidance of intervention with fluid and drugs. EDM can do this effectively in the hemodynamically challenging environment of the Operating Theatre, where anesthesia and surgery result in rapid and frequent changes in compliance. Pressure based technologies are useful in stable postoperative patients but are limited in their ability to guide interventional treatment.  A combination of both technologies, EDM+ is the best of both worlds.