Lab Case 219 Interpretation

A 75 year old male presents to ED after 2 syncopal episode at home.

Metabolic acidosis – pH 7.2 HCO3 9

Compensation – Expected pCO2 = 1.5xHCO3 +8 = 21.5

AG = Na – (Cl + HCO3) =26

Delta Gap = Change in AG/Change in HCO3 = 0.93

The above VBG shows a metabolic acidaemia due to a  HAGMA. The HAGMA is compensated for. There is a markedly elevated lactate and hypoglycaemia. There is a moderately low haemoglobin and a mildly elevated creatinine. Electrolytes are within normal limits.

In this clinical context of syncope and low HB with a patient on dual antiplatelet therapy, an upper GI bleed needs to be considered causing orthostatic syncope.  This needs to be aggressively sought. The cause for the HAGMA is likely multifactorial – lactic acidosis secondary to hypovolaemic shock from an upper GI bleed. The BSL is low and the lactate is markedly elevated – this could be due to liver failure, which could also contribute to the low HB – varices or bleeding diathesis.   Other causes for such a high lactate need to be considered – seizures (was the syncope actually a seizure?), overdoses – valproate (causing multi organ failure), delayed paracetamol OD with liver failure.  The renal dysfunction can be contributing to the HAGMA. With the low BSL, starvation ketosis could also be a cause for the HAGMA.

Syncope is defined as a sudden and transient loss of consciousness that is associated with loss of postural tone and that resolves spontaneously and completely without intervention.

When assessing a patient with syncope, the differential diagnosis needs to be considered ie:

Cardiac causes – more likely if the syncope occurs while seated or reclining, or during exertion, or with associated chest pain and palpitations

Neurological causes – more likely if associated with a headache or neck manipulation

Systemic Hypotension – more likely if the patient complains of orthostatic symptoms, is dehydrated or shows signs of blood loss or on offending medication

Endocrine – history of diabetes, or use of hypoglycaemic medication

Reflex mediated – vasovagal or situational syncope is more likely associated with preceding nausea or vomiting

Psychiatric Disease

A collateral history from witnesses is valuable to help differentiate syncope from seizures, and further information around the preceding events need to be sought.

A detailed past medical history and medication history will further help define the cause of the syncope

Examination should focus on vital signs including postural blood pressures, a thorough CVS and neurological examination. If there is concern about systemic hypotension abdominal and rectal examination should be done to look for bleeding.

Bedside investigations include BSL, ECG and U/A and BHCG in woman of child bearing age.

Further investigations will be directed by your history and physical examination looking for specific cause. Imaging and blood tests should not be routinely performed, unless a specific cause is being sought.