aka Prehospital Predicament 002
This is a case scenario that challenges you to find the solution! Do you fancy yourself as a latter day Joseph Bell?
Let’s see if you’re up to it…
A retrieval registrar and flight nurse are on a mission to transport a ventilated patient with severe pneumonia from a rural hospital. At handover of the patient at the referring facility, everything appears stable with good oxygenation and haemodynamics. The patient has been intubated and ventilated for 2 hours. There is good urine output. An arterial line is placed. An arterial blood gas is drawn preflight and shows adequate oxygenation and ventilation but a low potassium of 3.2 mmol/L.
A decision is made to provide potassium replacement during the transport and the registrar prepares a litre bag of normal saline with 3 x 20 mmol ampoules of KCL, whilst the nurse setups the transport monitoring and ventilator. The patient is loaded onto the aircraft and the Saline/KCL bag infusion is started at 250 mls/hr.
30 minutes into the flight, the transport monitor shows a broad complex tachycardia then ventricular fibrillation. CPR is begun. An urgent arterial blood gas is done and shows a potassium level of 14 mmol/L! Calcium gluconate and insulin /dextrose are given. The Saline/KCL infusion is stopped. Two cycles of CPR and defibrillation lead to return of sinus rhythm and spontaneous circulation. Repeat potassium levels 10 and 20 minutes later show a rapid decline in serum levels.
On inspection of the Saline/KCL bag only 120mls of the solution had been infused.
The aeromedical consultant on review of the case asked the registrar one key question that explains completely what happened.
I must thank my brother Thien, who is a retrieval anaesthetist in South Australia, for this case.
What is the single question that the consultant asked the registrar?
Not so fast! We’re going to break with LITFL case-based Q&A tradition and give you some time to mull this one over…
Feel free to leave a comment if you think you know the answer or you have something worthy of discussion. We’ll put you out of your misery sooner or later…
Addendum 15 May 2012
The question was:
“Did you thoroughly mix the bag of fluid after adding the KCl?”
KCl at 20 mmol/ 10 mL is considerably more dense than normal saline. Unless thouroughly mixed the KCl solution will simply sit at the bottom of the bag… The patient will thus receive a dose of highly concentrated, and potentially lethal, KCl.