CICM SAQ 2016.1 Q8

Question

Critically evaluate the role of monitoring blood lactate levels in the critically ill.

Answer

Answer and interpretation

Introduction:

Lactate measurement is easy, widely available and accurate. High blood lactate levels may represent increased production from tissues and/or decreased metabolic clearance.

Uses

  • End-point of resuscitation – lactate clearance.
  • Diagnosis of inadequate tissue oxygenation / ischaemia.
  • Risk stratification in ED and ICU – predictor of non-survival.
  • Prognostication and assessment of severity in liver disease.
  • Prognosis post cardiac arrest.
  • Lactate gap (lactate value from POC analyser – lactate value from lab) assists diagnosis in ethylene glycol toxicity.

Evidence:

  • Lactate levels proportional to mortality – lactate ≥ 4 is associated with poorer outcome.
  • Poor lactate clearance in trauma patients associated with bad prognosis.
  • High lactate levels may indicate underlying sepsis in patients who otherwise appear stable (in
    Rivers EGDT in sepsis trial, 50% patients with MAP >100 had high lactate).
  • Multi-centre study of 100 patients post cardiac arrest showed lower lactate levels in first 24 hours and increased lactate in first 12 hours post arrest were associated with survival and
    good neurological outcome.
  • Sustained high levels of lactate in paracetamol toxicity related ALF may be a trigger for need
    for transplantation.
  • Three studies have looked at lactate-directed versus non-lactate-directed therapy in:
    • Post-cardiac surgery patients – showed reduction in morbidity but not powered to look at
      mortality.
    • Septic patients in the ED – testing non-inferiority with ScvO2 showed no difference in
      outcomes although some limitations of study.
    • ICU patients with raised lactate levels – used GTN when ScvO2 normalised but lactate
      remained high. Showed statistically significant reduction in morbidity and trend to reduction in mortality but course of lactate levels in both groups was similar.

Practical points:

  • Monitoring alone does not improve outcome and treatment needs to target the underlying disease. Adequate understanding of the anaerobic and aerobic mechanisms of production and clearance is essential to correctly interpret the significance of raised lactate levels. Lactate levels should be interpreted with clinical correlation.

Lactate levels not useful in:

  • Elevated lactate levels with beta agonist therapy (increased lactate production from
    increased glycolytic flux).
  • Post seizures.

Overall:

  • Lactate levels in critical illness not fully understood.
  • Lack of high-level evidence showing use of lactate monitoring improves outcomes.

Summary statement:

For example:

Lactate appears to be an epiphenomenon and marker of severity in the critically ill. My practice is to use it as an end-point of resuscitation and an indicator of possible underlying tissue ischaemia in the shocked patient but not necessarily to react in patients who are otherwise haemodynamically stable with adequate tissue O2 delivery.

Additional comments:

Candidates were given credit for including valid points not included in the template. The detail of the studies given in the above template was not required for a pass mark.

Satisfactory answer for a pass mark was expected to include:

  • The uses of lactate monitoring
  • Some reference to the supporting evidence
  • Limitations of lactate monitoring

Pass rate: 14.6%

Highest mark: 7.0


Exams LITFL ACEM 700

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CICM

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health and Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of two amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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