Lactate

Question 1

What is lactate?

Answer 1

• By-product of an emergency mechanism that produces ATP from glucose when oxygenation of tissues is insufficient (hypoxia)
• Produces 2 mol ATP/mol of glucose
• Excess lactate released into blood (early, sensitive, quantitative indicator of O2 deprivation in tissues)

Question 2

How is lactate regulated?

Answer 2

• Not specifically reg’d
• As O2 delivery decreases to critical, blood lactate [ ] rise rapidly indicating tissue hypoxia earlier than pH
• Liver is major organ for removing lactate by converting back to glucose (gluconeogenesis)

Question 3

Clinical application for critically ill patients

Answer 3

• Metabolic monitoring
• Indicating severity of illness
• Objectively determining pt. prognosis

Question 4

Clinical application for type A lactic acidosis

Answer 4

• Most common

- Associated w/ inadequate O2 uptake/decreased blood flow

Question 5

Clinical application for type B lactic acidosis

Answer 5

• Metabolic origin (associated w/ disease, drugs/toxins/sepsis or inborn errors of metabolism)

Question 6

When is there a need for lactate therapeutic intervention?

Answer 6

• Usually high post-surgery
• When it remains high despite treatment
• Rise in lactate during treatment

Question 7

Treatment for high lactate

Answer 7

• Treat the underlying cause
• Oxygen
• Possible medications

Question 8

How/what specimen is collected for lactate determination?

Answer 8

• Patient should fast and sit/be reclined for 2 hours prior to collection
• Venous or arterial
• Should be collected w/ no tourniquet (could increase levels)
• Prevent anaerobic glycolysis (iodoacetate/fluoride as additive or heparinized blood on ice)
• Spin w/in 15 min, avoid hemolysis

Question 9

Requirements for a CSF lactate

Answer 9

• Patient sitting/reclined for 10min
• Rush to lab on ice immediately after collection
• Unsuitable if contaminated w/ blood

Question 10

Describe the method of lactate measurement

Answer 10

• Enzymatic
• Intensity of color formed is proportional to [ ] (DXC measures endpoint at 520nm)
• Other means of following perfusion/oxygenation: pulse oximeters, indwelling catheters that measure blood flow

Question 11

Why is it not likely a lactate will be measured by ISE?

Answer 11

• Very costly

- Electrodes have a very short life span

Question 12

When is L-lactate acidosis likely?

Answer 12

• Conditions producing hypoxia
• Some metabolic abnorms
• Drug intoxication

Question 13

When is D-lactate acidosis likely?

Answer 13

• Uncommon
• After jejunoileal bypass surgery (from alteration of intestinal NF, its produced by abnormal bacteria)
• Manifests as encephalopathy w/ elevated D-lactate but norm levels of L
• Not detected by routine methods

Question 14

Reference ranges for lactate

Answer 14

Arterial: 0.5-1.6
Venous: 0.5-2.2
CSF: 1.0-2.9

Hyperlactemia: >2.0
Lactic acidosis: >3.0-4.0

Question 15

When does lactic acidosis occur?

Answer 15

Due to medical conditions: congestive heart failure, sever anemia, metabolic disorders, drugs/toxins/sepsis

Question 16

When should levels be determined?

Answer 16

• AG (K included) >20mmol/L

- pH <7.25 and pCO2 is not elevated (generally indicates significant acidosis)

Question 17

What does an increased CSF without increased blood lactate indicate?

Answer 17

• Cerebrovascular accidents
• Intracellular hemorrhage
• Epilepsy and other CNS disorders

Question 18

What does a CSF lactate >4.0 indicate?

Answer 18

Bacterial meningitis