Oxygen Sat 38% !!

The patient was a 53 yo man having a FESS procedure. Pre-op assessment was unremarkable except for BMI of 37.  Anaesthesia was induced with fentanyl 100 mcg, midazolam 2.5 mg, propofol 200 mg and atracurium 35 mg.

He was a grade 2 laryngoscopy and was intubated with a size 7.5  oral RAE ETT.

Initially ventilation and observations were normal.

The patient's pillow was replaced with a head ring.

At this stage the ventilator alarm sounded. The patient was manually ventilated with difficulty.

Auscultation of the chest indicated poor air entry with some squeaky / bubbly noises.

The CO2 trace showed only a small rise to about 15 mmHg with a peak-like rather than a plateau shaped trace. The O2 saturation started to fall.

This was felt to be due to profound bronchospasm and a diagnosis of atracurium anaphylaxis was presumed.

Adrenaline was requested and 0.2mg IV was given.

By this stage the O2 sat was 75%. HR was 90 and BP 110/70. There was no obvious rash.

Ventilation remained difficult. A further 0.5 mg of adrenaline was given.

The assistance of another anaesthetist from a neighbouring theatre was requested.

 By the time the other  anaesthetist arrived the O2 sat was 38%. BP was 200/110 and HR was 120 with atrial ectopic beats.

The assisting anaesthetist found similar difficulties with ventilation and removed the ETT.  A self-inflating bag with mask was used to ventilate the patient with no difficulty. The O2 sat  climbed rapidly to 96%, the CO2 trace returned to a normal shape and the ectopic beats disappeared.

It appears the ETT had become displaced during head manipulation to become oesophageal / in the hypopharynx. The anaesthetist had seen the ETT pass through the vocal cords initially and presumed throughout that it was still in its correct position. There had been a very small amount of gas exchange producing a low peak shaped (misleading) CO2 trace.

 

The procedure was postponed and the patient made a full recovery.

 

Comment 1

It is very unusual for anaphylaxis to present with purely bronchospasm.

Comment 2

One problem with RAE ETTs is that they are “one size fits all” because of their pre-formed curve at the level of the mouth. So in a taller patient a standard sized ETT is more likely to "pop out" of the larynx, as apparently happened in this case.

Comment 3

“Fixation error” is a problem for us as anaesthetists. We need to be aware of the kind of situations in which it can occur, such as this one.

Comment 4

If there is any doubt change the ETT, or remove it and resort to bag and mask ventilation. If there could be any problems with the circuit on the anaesthesia machine, then one should reach for the self-inflating bag.

Find the self-inflating bag in the photo:

(It is important to know where this equipment is in your OT as you may need it in a hurry!)