October 26, 2017

004 Life-threatening bronchospasm – safe mechanical ventilation

18 minutes

(*This is a fictional case)

Your patient has just had a very difficult instrumental delivery in theatre after a prolonged obstructed labour. Unfortunately now her uterus won’t contract despite oxytocin and ergometrine and she is bleeding pretty briskly. You clean her deltoid with an alco-chlorhex wipe, inject 250mcg (1 ampoule) of carboprost i.m. and cross your fingers that this will do the job. You lean over the drapes, talk to the obstetric team and start rubbing her uterus while they repair the episiotomy. Suddenly you hear a raspy wheezing sound from the head of the bed – you immediately jerk your head around and glance at your patients face – she looks terrified. Bronchospasm! She has pursed lips and is struggling to breathe, her sats probe says 75% and you suddenly wish you had signed up to do dermatology back in your intern year…..

Your assistant runs around trying to find a nebuliser and salbutamol and over the next 4 minutes she becomes unresponsive, her breathing becomes progressively worse and she takes on a mottled colour. Everyone in the room including the IT technician fixing the PC in the corner can see she needs you to manage her airway & breathing……

1. How would you induce anaesthesia? Which drugs would you use?

2. Once you get the endotracheal tube in place how are you going to set up the ventilator to safely ventilate this woman?

You notice her ETCO2 is already 75mmHg and you can’t even get a pulse oximtery reading. You decide that her hypoxia and the acidosis from all that CO2 is causing her some serious harm – time to get some oxygen in. You set the ventilator to VCV with tidal volume 700ml x 16 breathes per minute and a PEEP of 8mmHg.

3.After a few minutes your patient has no pulse! What has happened (what is the differential diagnosis) and what are you going to do…?

4. You sort that issue out but now what bronchodilators are you going to use?

5. Her uterus is still bleeding and in fact the tone is much worse – what are you going to do about that!

SAFE MECHANICAL VENTILATION IN BRONCHOSPASM

KEY POINTS:

Use a volume-control mode of ventilation.

Use minimal PEEP.

Use a small tidal volume, 5-7ml/kg

Use a slow respiratory rate, 10-12 breaths per minute (or even less!)

Use a long expiratory time, with I:E ratio 1:3 or 1:4

Increase inspiratory flow rate to maximum. .

Reset the pressure limits (i.e. ignore high peak airway pressures). .

Use heavy sedation.

Use neuromuscular blockade.

Use lowest FiO2 to achieve SpO2 of 90-92%

Minimise the duration of neuromuscular blockade.

Keep the Pplat below 25cmH2o to prevent dynamic hyperinflation.

Resources:

http://www.derangedphysiology.com/main/required-reading/respiratory-medicine-and-ventilation/Chapter%206.1.1/ventilation-strategies-status-asthmaticus

http://intensiveblog.com/ INTENSIVE podcast – The Alfred ICU. “Asthma and Mechanical Ventilation Pitfalls by David Tuxen”

...more

View all episodes

By Roger Browning - Anaesthetist

4.8

55 ratings