27 year old male is brought into ED by his parents who are concerned about the patients mental health, the patient showing increasing anxiety and low mood over the last few weeks

Metabolic acidosis pH7.1  HCO3 10.2mmol/l

Compensation: Expected pCO2 =HCO3x1.5+8 =23mmHg.

AG = Na- (Cl+HCO3) =21

Delta gap = Change in AG/Change in HCO3 =0.64

Corrected potassium for pH – for each 0.1 drop in pH the potassium increases by 0.6, therefore actual potassium 1.7

The above VBG shows a metabolic acidaemia. It is partially compensated for with an expected PCO2 of 23mmHg, or there is an underlying respiratory acidosis.  There is a raised anion gap with a delta ratio of 0.64 suggestive that there is an existing NAGMA as well. There is a markedly raised lactate of 14, a low normal sodium and chloride. There is a markedly low corrected potassium of 1.7 mmol/l.  The BSl and Cr are within normal range

In this clinical context a number of causes could account for the VBG results. The HAGMA is secondary to a lactic acidosis. The lactic acidosis could be due to seizures, ingestion of a serotonergic, anticholinergic or sympathomimetic drug or fever due to underlying sepsis.

The co existing NAGMA (recall USEDCARP for causes) might be a result of RTA secondary to toluene or other chronic solvent ingestion. Typically  RTA due to solvent abuse presents with a hyperchloraemic, hypokalaemic NAGMA. This patients chloride is on the low-normal side. Other causes to consider would be Addisonian crisis (but potassium is low and BSL is normal). Normal saline is also a common cause for a NAGMA but the chloride would be raised if this was the cause.

The coexisting respiratory acidosis could be secondary to aspiration or the patients altered GCS.

The low normal sodium could be secondary to SIADH that can occur with MDMA abuse.

Other causes for the low potassium could be poor diet, abuse of sympathomimetic drugs or a theophylline over dose

Management of this patient would include:

Resuscitation

• Intubation – to consider if GCS continues to drop or temperature not responding to fluids and benzodiazepines (resuscitate and optimise patient before intubating)
• fluids – normal saline boluses 500ml aiming for MAP 60mmhg, HR<100, u/o 0.5ml/kg/hr (might increase end point if CK is found to be raised)

Specific treatment

• Temperature management – core temperature monitoring, titrate diazepam 5-10mg to achieve gentle sedation and aim for a temperature <38 degrees. If temp >39.5 C – intubate and paralyse
• Seizure control – diazepam
• Replace potassium and magnesium and recheck on regular basis
• Look for other complications and causes and treat accordingly eg sepsis, other electrolyte abnormalities, raised CK, head injury. Obtain collateral from family and medical notes – specifically what medication is the patient on and what illicit drugs do they use.

Supportive care

• Cardiac monitoring, fluid and fluid balance
• Fluids
• Bladder care
• DVT prophylaxis

Disposition

• Observe in ED, if improving – observation ward admit, if not HDU/ICU
• Psych and drug and alcohol review when patient improved GCS