A 33 year old female presented with high fever and abdominal pain. She
has gram negative bacteraemia and septic shock. The following are data
from blood gas analysis. ·
Parameter |
Patient Value |
Normal Range |
FiO2 |
0.3 |
|
pH |
7.43 |
7.35 – 7.45 |
PaCO2 |
23* mmHg (3.0 kPa) |
35 – 45 (4.6 – 6.0) |
PaO2 |
107 mmHg (14 kPa) |
|
HCO3 |
15* mmHg |
22 – 26 |
Standard base excess |
-8.6* mmol/l |
-2 – +2 |
Sodium |
147* mmol/l |
135 – 145 |
Potassium |
6.7* mmol/l |
3.2 – 4.5 |
Chloride |
95* mmol/l |
100 – 110 |
Lactate |
23.0* mmol/l |
< 2 |
a} List the acid-base abnormalities
b) What are the causes of elevated plasma lactate in sepsis?
c) Name 3 drugs which result in plasma hyperlactaemia
College Answer
a} List the acid-base abnormalities
High anion gap metabolic acidosis with raised lactate Metabolic alkalosis (Delta BE <Delta AG) Respiratory alkalosis
b) What are the causes of elevated plasma lactate in sepsis?
1) Circulatory failure due to hypotension and hypoxia
2) Microvascular shunting and mitochondrial failure (cytopathic hypoxia)
3) Use of adrenaline as an inotrope
4) Inhibition of pyruvate dehydrogenase (PDH) by endotoxin.
c) Name 3 drugs which result in plasma hyperlactaemia
- Catecholamines
- Metformin I Phenformin
- Alcohols
- Cyanide, nitroprusside
- Salicylates
Discussion
This question is frequently repeated. Notable duplicates include the following:
- Question 6.4 from the first paper of 2013 (a detailed discussion is carried out here)
- Question 22.2 from the second paper of 2011
- Question 6.4 from the first paper of 2011
- Question 24 from the first paper of 2010
- Question 18 from the first paper of 2007
References
Grubbs, Robert D., and Michael E. Maguire. "Magnesium as a regulatory cation: criteria and evaluation." Magnesium 6.3 (1986): 113-127.
Martin, Kevin J., Esther A. González, and Eduardo Slatopolsky. "Clinical consequences and management of hypomagnesemia." Journal of the American Society of Nephrology 20.11 (2009): 2291-2295.
Chakraborti, Sajal, et al. "Protective role of magnesium in cardiovascular diseases: a review." Molecular and cellular biochemistry 238.1-2 (2002): 163-179.