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Clinical Evidence

Clinical Evidence

Deltex Medical has a large body of Clinical Evidence and Educational Resources to support any hospital education program.

As well as  a large number of clinical papers, available in our Library, we have a range of Randomized Controlled Trials and a Meta-Analysis. These provide an in-depth understanding of how Esophageal Doppler Monitoring, Fluid Management and Enhanced Recovery can improve patient outcomes.

Premier Study 2015

Meta-Analysis

This Meta-Analysis has been prepared rigorously and objectively by Deltex Medical’s lead scientist. It is designed to be a valuable resource to everyone interested in the evidence for Intraoperative Fluid Management (IOFM) and may be downloaded and used without any need for permission.

Click here to download the full Meta-Analysis

This Meta-Analysis of published outcome evidence of fluid management using a Stroke Volume Optimization (SVO) strategy confirms that EDM is the only technology that can reduce both the incidence of complications and the length of hospital stay during surgery.

Studies of EDM-guided SVO for fluid management demonstrate a reduction in the incidence of postoperative complications, whereas studies using an arterial pressure based device (PPWA) to guide SVO for IOFM did not:

Comp 11.12

EDM-guided IOFM demonstrated a 1.1-day reduction in length of hospital stay, an outcome not obtained with PPWA technologies.

Deltex Medical plans to update the meta-analysis as it becomes aware of further studies newly published in peer reviewed journals to create a ‘living’ up to date meta-analysis.

LOS 11.12

Visitors to this page are invited to contact the author by email, should you wish to highlight any new or published studies which may merit inclusion: meta-analysis@deltexmedical.com

RCTs

A number of Randomized Controlled Trials (RCTs) have been conducted using the EDM to guide fluid management during surgery. See below for a summary of each, or the [Library] for a list of references.

Pillai, 2011 Summary

Challand, 2012 Summary

Clinical Application: Intraoperative

This double-blinded controlled trial compared goal-directed therapy (GDT; using esophageal Doppler monitoring (EDM) for intraoperative fluid management with that of routine care.

Protocol

179 patients undergoing elective colorectal surgery underwent cardiopulmonary exercise testing prior to being categorized as aerobically ‘fit’ (anaerobic threshold >11 mL O2/kg/min; n=123) or ‘unfit’ (n=56). Within each fitness group, patients were randomly assigned to receive fluid management using GDT or based on routine care. Patients included those undergoing both open and laparoscopic procedures. Outcome measures included readiness for discharge, actual length of stay, and postoperative complications.

Results

There was no difference in the amount of maintenance fluid given to the GDT and control groups (mean: 3849 mL vs. 4010 mL respectively). Approximately 90% of this maintenance fluid was crystalloid, infused at ~17 mL/kg/h. The GDT group received on average an additional 1360 mL of colloid (in the form of 200 mL boluses to optimise stroke volume (SV)). The GDT and control groups were 4179 mL and 4062 mL respectively in positive fluid balance at end of the day of their surgical procedure.

Time to readiness for discharge (6.8 [GDT] vs. 4.9 days [control]; P=0.09) and actual length of hospital stay (8.8 vs. 6.7 days; P=0.09) tended to be longer in the GDT group. This difference in length of stay became significant when analysis was performed on the aerobically ‘fit’ patients only. There were no significant differences in other outcome parameters including, gastrointestinal morbidity, serious postoperative complications, critical care admission or mortality between the GDT and control groups.

Commentary

The authors conclude “Intraoperative SV optimization conferred no additional benefit over standard fluid therapy. In an aerobically fit subgroup of patients, GDT was associated with detrimental effects on the primary outcome.”

Limitations

The results from this study are at odds with the previously published randomized controlled trials that use EDM to guide fluid management. The reasons for this may be related to the following:

  • Large volumes of maintenance crystalloid were administered to both patient groups. The authors aimed to target 10 mL/kg/h, but actually gave 17 mL/kg/h, an amount much higher than the recommended maintenance crystalloid rates of <2 mL/kg/h [1]. These high volumes of fluid may have placed the patients at risk of fluid overload.
  • The double-blinded nature of the study meant that during the procedure the anesthetist (infusing the maintenance fluid) and the investigator (administering the colloid boluses) were unable to correspond with each other. Therefore, even once the patient had an optimized SV (as deemed by the ODM), the anesthetist may still have been infusing high levels of maintenance crystalloid.
  • The poor randomization of the groups resulted in the GDT group having: fewer bowel preparations but more preoperative crystalloid loading, more epidurals, more blood transfusions and fewer laparoscopic procedures. These factors may have biased the GDT group towards a longer length of stay.
Summary of Responses

This study has generated responses from readers and the authors themselves, some of these are summarised as follows:

  • “The EDM data were only available to the investigator, who could, according to the algorithm, give boluses of colloid until no further increase in SV was recorded. At this point they would give no further fluid. The anesthetist without this information would continue to give maintenance and other fluid they felt necessary…It seems the study design led to more fluid being given than might have been if the ODM data were visible to the an esthetist.” Rivers, 2012 [2]
  • “This study provides a surprising result…which is in contrast to the large body of available data supporting the use of GDT in open surgery and the NICE technology appraisal… It is hard to see from the data presented exactly what led to the delayed readiness for discharge as tolerance of diet, bowel movement, flatus passed, renal complications, and postoperative complications did not show any significant difference between the two groups… As with many studies, it raises more questions than it directly answers.” Isherwood, 2012 [3]
References
  1. Mythen, M.G.S., M.; Acheson, N.; Crawford, R.; Jones, K.; Kuper, M.; McGrath, J. S.; Horgan, A. F., Perioperative fluid management: Consensus statement from the enhanced recovery partnership. Perioperative Medicine, 2012. 1(2).
  2. Rivers, J., Intraoperative goal-directed fluid therapy in aerobically fit and unfit patients having major colorectal surgery. Br J Anaesth, 2012. 108(6): p. 1036; author reply 1037.
  3. Isherwood, P., Re: Randomized controlled trial of intraoperative goal-directed fluid therapy in aerobically fit and unfit patients having major colorectal surgery. Br J Anaesth, 2012. 108(6): p. 1036-7; author reply 1037.

 

Case Studies

Postoperative hypovolemia responding to fluid management

Effects of vasodilation, useful ectopics

Background

Montreux, Switzerland

83 year old man, Wt 66kg. Ht 177 cm, BSA 1.82 m2. Intraoperative closure of colostomy. No cardiac history

Baseline at start of surgery

CO, SV and FTc may be acceptable for a healthy resting individual. CI and PV are on the lower end of normal A normal PV for this age is approximately 50-80cm/s. Although these parameters appear normal, vasodilation and therefore low resistance/afterload is usually expected with anaesthesia, but since FTc is ‘normal’, the vasodilation could be masked by a relatively low preload.

Baseline at start of surgery

After epidural top up

Before a fluid challenge was considered, a bolus of the epidural was given. This is likely to cause further dilation. SV, SVI and PV have reduced, which may indicate that preload may not be sufficient. CO/CI is similar, FTc has increased slightly. The clinician surmised that there may be relative hypovolemia present due to vasodilation, and two 200ml rapid fluid challenges were given to fill the dilated vascular space.

After epidural top up

Useful ectopic

All parameters have increased following the fluid and in particular the SV has increased by >10% indicating fluid responsiveness. Subsequently, isolated atrial ectopics were seen on the ECG. This can be useful when using EDM monitoring to determine fluid responsiveness. If the waveform after the ectopic is larger than a normal waveform, this indicates that the compensatory pause allows more filling and this larger waveform indicates fluid responsiveness.

Useful ectopic

Flow parameters reduced

Despite these indications of a possible reduction in circulating blood volume, no further fluid was given and 10 minutes later, SV and other parameters reduced. The clinician then gave three fluid challenges as per algorithm with good SV increases.

Flow parameters reduced

After 3rd fluid challenge. Abdomen now closed

SV increased by >10 %. Other flow parameters increased. These indicate good responses to fluid.

After 3rd fluid challenge, abdomen now closed

Summary

This case scenario describes how relative hypovolaemia can be missed. Since FTc is inversely related to resistance/afterload, it can be assumed that when the patient is dilated, that FTc should rise, however if the vascular space remains under filled (relative hypovolemia), the flow numbers may reduce initially until filling commences. It also describes how the presence of isolated ectopics could have helped the clinician to diagnose fluid responsiveness earlier. Both of these issues can be observed and corrected using the EDM monitors.

Abbreviations:

FTC – Flow Time corrected ECG – Electrocardiograph
CO – Cardiac Output/CI – Cardiac Index Wt – Weight
SV – Stroke Volume/SVI – Stroke Volume Index Ht – Height
PV – Peak Velocity BSA – Body Surface Area

 

BP – Blood Pressure CVP – Central Venous Pressure
CO – Cardiac Output HR – Heart Rate
SV – Stroke Volume Wt – Weight
FTc – Flow Time corrected Ht – Height
PV – Peak Velocity BSA – Body Surface Area

 

Library

There is a large body of evidence to support the use of Deltex Medical’s technology. This includes an AHRQ Technology Assessment,  NICE recommendation, Randomized Controlled Trials (RCTs), published Audit studies, Reviews and Meta-Analyses, and Case Histories. Click here for a pdf version of the Deltex Medical Bibliography.