Asthma Cardiac Arrest

Asthma Cardiac Arrest

In the early 1990’s at  the Alfred Hospital in Melbourne a young man was admitted in extremis with severe asthma. He had had many previous admissions some requiring ICU. He was intubated and ventilated, and given salbutamol and adrenaline.

However he went into asystole and was given all resuscitation measures but a rhythm could not be established. His pupils became dilated and fixed and further resuscitation was considered futile.

He was disconnected from the self-inflating bag and most of the staff left the room. After a few minutes a nurse noted that the patient had developed sinus rhythm. Staff were recalled and ventilation was recommenced.

However shortly afterwards he became pulseless  and again went into asystole. After some time resuscitation was again declared unsuccessful. Following disconnection from the breathing system the patient again developed a rhythm and pulses. Each subsequent time he was ventilated the same thing happened.

The staff realized that IPPV was causing the problem. Gentle ventilation with a slow respiratory rate was continued. The patient subsequently made a full recovery. This cases was written up in the journal “Anaesthesia and Intensive Care” in 1991 Vol 19 pp 118-121. Similar cases have since been published.

The problem here was gas trapping leading to high intrathoracic pressure which prevented venous return to the heart and resulted in cardiac arrest.

It is now appreciated that care must be taken with ventilation in asthma to allow ample time for expiration. A low respiratory rate of perhaps 6 breaths per minute should be combined with a long I:E ratio (say 1:6) to prevent gas trapping. Some level of “permissive” hypoxia and hypercarbia  is now considered to lead to better outcomes in ventilated asthmatic patients in preference to gas trapping.

There is not much point having oxygen in the lungs if there is no cardiac output to deliver it to vital organs.

Take Home Message:

Avoid high intra-thoracic pressures and gas trapping in ventilated patients with asthma.

This also applies to shocked patients where blood is returning to the thorax at very low pressure.

 source: http://www.anaesthesiacases.com.au/cases/asthma_cardiac_arrest