A 76-year-old man is admitted to ICU following a Medical Emergency Team call for hypotension and tachypnea. He is three days post-laparoscopic anterior resection for sigmoid cancer.
Information from his arterial blood gas is as follows:
Parameter |
Result |
Normal Range |
Sodium |
138 mmol/L |
135 – 145 |
Potassium |
5.4 mmol/L* |
3.5 – 4.5 |
Chloride |
104 mmol/L |
95 – 105 |
Barometric pressure |
760 mmHg (100 kPa) |
|
FiO2 |
0.4 |
|
pH |
7.01* |
7.35 – 7.45 |
PCO2 |
45 mmHg (6 kPa) |
35 – 45 (4.6 – 6) |
PO2 |
84 mmHg (11 kPa) |
|
Bicarbonate |
11 mmol/L* |
22 – 27 |
Base Excess |
-19 mmol/L* |
-2.0 – +2.0 |
Haemoglobin |
88 G/L* |
135 - 180 |
Glucose |
7.5 mmol/L* |
3.5 – 7.0 |
Lactate |
13 mmol/L* |
<2.0 |
a)
High anion gap metabolic acidosis
AG 23 not accounted for by just rise in lactate
Marked lactic acidosis
Respiratory acidosis
Hypoxaemia with A-a DO2 145
Anaemia
b)
Septic shock (intra-abdo, lung, other)
Hypovolaemic shock with intra-abdominal bleeding
Ischaemic gut
Cardiogenic shock (myocardial ischaemia or septic ardiomyopathy)
PE less likely with PO2 84 on FiO2 0.4 but cannot be excluded
c)
Resuscitation with simultaneous focussed assessment (history, examination, investigations) to ascertain diagnosis and institution of treatment (supportive and definitive)
Resuscitation – ensure adequate airway and ongoing adequate oxygenation and ventilation. Intubation and IPPV if needed. IV access and fluid resus plus/minus vasopressors.
Focussed assessment – differential diagnosis as above. Look for signs of bleeding, sepsis, intra-abdominal catastrophe, assess myocardial function
Investigations – FBC, U&E, coags, Troponin, septic screen, ECG, CXR, CT abdo (if stable) ± CTPA, bedside echo
Broad-spectrum antibiotics if sepsis suspected
Surgical review, consider proctoscopy, with urgent return to theatre if indicated (anastamotic leak, ischaemic gut)
Other urgent specific treatment as indicated eg stop bleeding, treat myocardial ischaemia Monitoring and transfer to ICU/HDU
Let us dissect these results systematically.
The lactate is 13, which can actually account for all of the increase in the anion gap. The anion gap is 23, which means it has increased by 11. The lactate is 13. What other anions do you need here?
Perhaps they want a better explanation for the change in SBE? True, there is a very large base deficit. Taking the simplistic view that lactate is a fully dissociated ion and for every mole of lactic acid there should be a mole of hydrogen ions, one would still fall short of explaining the SBE of -19.
Anyway: why is the lactate so high, the college asks?
Differentials relevant to this case might include the following:
Approaching the management systematically, one might respond to the last question in the following fashion:
Oh's Intensive Care manual: Chapter 45 (pp. 520) Abdominal surgical catastrophes by Stephen J Streat
Marshall, John C., and Marilyn Innes. "Intensive care unit management of intra-abdominal infection." Critical care medicine 31.8 (2003): 2228-2237.
Gajic, Ognjen, et al. "Acute abdomen in the medical intensive care unit."Critical care medicine 30.6 (2002): 1187-1190.