Improving surgical outcomes: it is the destination not the journey

A comparison of noninvasive bioreactance with oesophageal Doppler estimation of stroke volume during open abdominal surgery: an observational study

CONTEXT

The anaesthetist must maintain tissue perfusion by ensuring optimal perioperative fluid balance. This can be achieved using less invasive cardiac output monitors such as oesophageal Doppler monitoring (ODM). Other less invasive cardiac output monitors using bio-impedence technology (noninvasive cardiac output monitoring, NICOM) may have a role in monitoring the circulation and informing fluid management decisions.

OBJECTIVE

To compare estimates of stroke volume from ODM with those from NICOM, a noninvasive monitor using bioreactance, a modification of transthoracic bio-impedence.

DESIGN

An observational study.

SETTING

Manchester Royal Infirmary, UK. Data collected in 2011 and 2012.

PARTICIPANTS

Twenty-two patients scheduled for major, open abdominal surgery. Reasons for noninclusion: atrial fibrillation; heart failure; oesophageal disease; lack of capacity; and known sensitivity to colloid.

INTERVENTION

All patients had oesophageal Doppler cardiac output monitoring as a standard element of anaesthesia care. We placed NICOM Bioreactance electrodes and recorded stroke volume estimates from both devices. Fluid challenges were given by the anaesthetist and the haemodynamic responses were recorded.

MAIN OUTCOME MEASURE

Stroke volume during surgery. The Bland-Altman method was used to compare bias and limits of agreement for stroke volume and cardiac output. Fluid responders were defined as patients who increased stroke volume by at least 10% after fluid loading. The precision of each device was calculated during periods of haemodynamic stability.

RESULTS

We made 788 acceptable measurements of cardiac output. The bias was -6.9 ml and the limits of agreement were -22.9 to 36.8 ml. The percentage error was 57%. Average precision for both the ODM and NICOM were similar, 8.5% (SD 5.4%) and 8.7% (SD 3.2%). The concordance for the stroke volume change following fluid challenge was 90.5%. Both devices produced unacceptable readings with electrical diathermy.

CONCLUSION

Simultaneous stroke volume estimations made by noninvasive Bioreactance (NICOM) and oesophageal Doppler showed bias and limits of agreement that are not clinically acceptable. The measurements made by these two devices cannot be regarded as interchangeable.

Update on acute kidney injury after cardiac surgery

OBJECTIVES

To review the current state of clinical practice and discuss recent advances in the diagnosis and management of acute kidney injury (AKI) in the context of cardiac surgery.

METHODS

A review of the published data pertaining to AKI in the setting of cardiac surgery and cardiothoracic surgical critical care medicine was conducted, and the relevant data were synthesized from appropriate interventional and observational study reports.

RESULTS

Significant advances have occurred in the diagnosis of AKI, and consensus has been reported on a system of diagnosis using the serum creatinine and urine output. New biomarkers of injury and function are available that are likely to improve the interval to diagnosis of AKI after cardiac surgery. The adverse effect on outcome of small changes in serum creatinine is appreciated. Novel prevention and rescue therapies are now entering phase I and II studies. Urinary alkalinization was effective in a phase II blinded clinical trial and is now the subject of a multicenter, double-blind, randomized clinical trial of cardiac surgery patients.

CONCLUSIONS

In 2011, the field of AKI could be emerging from a period of stagnation that has lasted more than 2 decades. The failure to translate successful animal model interventions to the clinic might have resulted from delays in diagnosis that might now be avoidable with the advent of novel diagnostic biomarkers.