28 year old male BIBA as priority 1 – found unresponsive in room by parents. Patient last seen 24 hours prior. History of IVDU, they unsure what he has taken. Not on regular medication.
Mixed metabolic and respiratory acidaemia pH 7.208 PCO2 61 mmHg HCO3 18mmol/l
AG = Na – (Cl+HCO3) = 16
Delta Gap = Change in AG/Change in HCO3 = 0.67 Mixed HAGMA and NAGMA
Corrected potassium for acidosis – still high when corrected – 6.4mmol/l
The above VBG shows a mixed resp and metabolic acidaemia as well as a delta gap of 0.67 implying a HAGMA and NAGMA causing the acidaemia. The patient has a moderately raised creatinine and lactate, and a markedly high potassium.
In this clinical context the patient is presenting with signs and symptoms suggestive of a sympathomimetic toxidrome, with features of sodium channel blockade. Other toxidromes to consider would be anticholinergic and serotonergic toxidromes. Other causes to consider could be overwhelming sepsis, ICH, endocrine causes eg thyrotoxicosis.
The HAGMA is likely related to a combination of the lactic acidosis, renal dysfunction and toxins. There are numerous drugs that can cause this presentation including methamphetamines, MDMA and antipsychotic medication. The lactic acidosis is most likely secondary to hyperthermia, dehydration and /or seizures. The AKI is likely due to dehydration, but rhabdomyolysis needs to be excluded. The coexisting NAGMA in this case could be secondary to RTA or Addisons disease (associated high K), or diarrhea. The respiratory acidosis could be due to altered level of consciousness (the RR is a lot lower than you would expect in a pyrexial patient with a metabolic acidosis) or an underlying lung pathology eg aspiration pneumonia.
Management
A – Intubation – this patient has 2 indications for intubation – altered GCS and hyperthermia in the context of toxidrome. However, the patient needs to be adequately resuscitated before intubated – need to address hypoxia, hypotension, tachycardia and sodium channel blockade, and hyperkalaemia. Drugs to be used in intubation – fentanyl, low dose propofol (patient already has low GCS and low BP), rocuronium 1.2-1.5 mg/kg (sux C/I due to hyperkalaemia). Stand by drugs – metaraminol, sodium HCO3
B – Optimise oxygenation and ventilation prior to intubation – might need to use modified RSI ie ventilate the patient during induction to avoid worsening acidosis. When intubated hyperventilate to pH 7.5 to manage sodium channel blockade. Maintain sats 94-98% (avoid hyperoxaemia). Place NGT, CXR and activated charcoal
C – IV fluids to address the hypotension and AKI. Correct hyperkalaemia. Sodium HCO3 2mmol/kg until HR <100 Seek underlying cause – bloods sent for inflammatory markers, O/D screening and CK
D – Post intubation – on going sedation. Weigh up risk vs benefit of paralytic agents to control temp vs avoiding paralytics to monitor for seizures. Consider antibiotics
E – active cooling – cool fluids, icepacks, arctic sun etc. Invasive temperature moitoring Catheter monitor u/o. Arterial line. Other non invasive monitoring. Actively seek causes and complication of presentation – CT head. Referal ICU
F – try and obtain further collateral.