34 year old male with a background of alcohol dependence (30 standard drinks per day) and Crohn’s disease presents to ED after 24 hours of no alcohol use. He is complaining of feeling anxious, sweaty and in the last few hours he feels like his legs are cramping and he is feeling increasingly weak. He required a wheel chair to get him into the department.
VBG
pH 7.66 Na 127mmol/l
pCO2 31mmHg K 2.3 mmol/l
pO2 32mmHg Cl 68 mmol/l
HCO3 36mmol/l Cr 156 umol/l
B/E 14 Lactate 7.2 mmol/l
BSL 9.0 mmol/l
- Describe and interpret the VBG
- What is delirium tremens?
Answer
Metabolic alkalosis – pH 7.66 and HCO3 36mmol/l
Compensation – expected PCO2 = 0.7XHCO3 +20 (+/-5)= 45
AG = 23
The above VBG shows a metabolic alkalosis with inadequate compensation with an actual CO2 lower than expected, which indicates a coexisting respiratory alkalosis. There is a raised lactate with an raised AG, causing an underlying HAGMA. There is a moderately low sodium, and a severely low potassium and chloride. As well as a mildly raised creatinine and BSL.
In this clinical context this case is more complex than simple alcohol withdrawal. The metabolic alkalosis could be due to a number of causes in this case including
-volume contraction
-endocrine – Cushing syndrome needs to be considered in this patient if the patient is on steroids for his Crohns disease. The low potassium and elevated glucose would be consistent with cortisol excess, however one would expect to find an elevated sodium
-vomiting from alcohol withdrawal or excess
-renal bicarbonate retention in the context of hypochloraemia and hypokalaemia – this is through multiple mechanisms leading to a HCO3 retention and an increase in H+ excretion
The coexisting respiratory alkalosis could be due to tachypnea secondary to anxiety, hepatic encephalopathy, underlying aspiration pneumonia.
The causes of the low potassium is mutifactoral – vomiting, decreased oral intake, low magnesium, poor absorption as a result of the Crohns disease, the alkalosis causing a shift in potassium, aldosterone mediated due to volume contraction and Cushings if the patient is on steroids.
The low sodium is likely due to GI losses, as well as alcohol related
The very high lactate could be the result of hypovolaemia, shivering, liver failure, thiamine deficiency
Alcohol withdrawal can present on a wide spectrum from mild tremor to neuro-excitation leading to seizures. Delirium tremens is a severe form of alcohol withdrawal manifested by altered level of consciousness and autonomic hyperactivity. It occurs 3-10 days after the last drink and global confusion is the hallmark of DT’s. When managing patients with alcohol withdrawal it is essential to treat underlying co-morbidities as well as the alcohol withdrawal.