CICM SAQ 2016.1 Q8

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