So you have a really bad asthmatic in the emergency room, and you already have him on a continuous bronchodilator breathing treatment, and the nurse has already given intravenous epinephrine and solumedrol.
Now you, the RN and the doctor are willing to grasp at straws to prevent that person from needing to be intubated. What are some choices you might be able to recommend to the ER physician?
A book called Fatal Asthma and CMAJ list some of the most common "alternative therapies."
1. CPAP: This can be started to help the patient overcome his increased work of breathing. Adding CPAP is also a great technique of overcoming instinsic PEEP that causes hyperinflation. The problem with this is that asthmatics already feel as though they are suffocating, and this might make matters worse.
However, with good equipment, good coaching, and a doctor willing to apply to the patient some sedatives, this might be worth a shot if you have a compliant patient.
2. BiPAP: All the principles of CPAP apply here, except this also applies pressure with inspiraton to help the patient take in a deeper breath, thus allowing the patient to blow off some CO2. This may be of particular use if you suspect impending respiratory failure associated with a rising CO2.
I have seen BiPAP work on at least five asthmatics in the past couple years. Usually if a patient is bad enough to require noninvasive ventilation, we skip CPAP and go right to BiPAP.
3. Heliox: This is a helium/ oxygen mixture that consists of 80% helium and 20% oxygen. With the exception of hydrogen, helium is the lowest density of gas. And, according to medscape.com, since asthma is a disease associated with narrowed passages that result in turbulent flow and increased airway resistance, heliox can help create a more laminar flow, and thus decrease the work of breathing
According to studies, some patients benefit from this and others do not. So, while this is used in some hospitals, the jury is still out on whether it is a cost worthy investment for hospitals.
So now you have a patient in status asthamticus intubated in your emergency room. You have tried all the conventional therapies, and you once again are grasping at straws. What are some options?
4. Bronchiolar lavage: Also known as lung lavage. This is done with a fiberoptic bronchoscope and washing the bronchioles out with normal saline with the intent of clearing the lungs of mucus plugs. This is still not commonly done in a crisis, but remains an option.
5. Anesthetics: These are used to relax airway smooth muscles. According to Fatal Asthma, "Rapid, dramatic improvement is reported, leading to more effective ventilation and in some cases early extubation."
Ketamine is a smooth muscle relaxant and antihistamine, and is given intravenously. Of course this medicine is a known hallucinogenic, and it is a sedative. Many doctors prefer to wait until a patient is intubated to use it, and follow it up with a paralytic, as you can read here.
Isoflurane is an anaesthetic and bronchodilator that has been proven to be efficacious in ventilated patients in status asthmaticus. According to this study, " Isoflurane improves arterial pH and reduces partial pressure of arterial carbon dioxide in mechanically ventilated children with life-threatening status asthmaticus who are not responsive to conventional management."
6. Permissive Hypercapnia: This is something I'd wish doctors where I worked would consider more often. We had an asthmatic a few years back who was admitted to CCU, and the doctor ordered a tidal volume of 750. Since I was bagging the patient, and her lungs were stiff, like ventilating a brick. When I finally got her hooked up to the vent the highest tidal volume I could get was 150. The doctor was irate. But I was right. He finally admitted as much.
So, the point with permissive hypercapnia is that you allow a high CO2 and low pH at the expense of low pressures and a lower tidal volume and an appropriate respiratory rate to allow time for the patient to fully exhale to prevent air trapping. You do this while continuously trying to get the patient's airways to open up. In this patient's case, it took two days for this to happen.
As the author's of Fatal Asthma state, "Prolonged severe hypoxemia can cause devastating neurological injury and death, prolonged hypercapnia per se is thought to have no long-term adverse consequences. Use of permissive hypercapnia has become standard practice in many intensive care units and in general has rendered unnecessary other 'heroic' measures in the critically ill asthmatic patient."
Well, those are some of the options available to today's physicians for the treatment of status asthmaticus unresponsive to conventional therapies. Where I work we've used BiPAP and Bronchiolar lavage, although rarely.
I've known about heliox and permissive hypercapnia, but the anaesthetics used to treat status asthmaticus is something new to me. If these medicines were ever used at my facility I'm unaware of it.
If any of my readers know of any other alternative therapies for asthma please share them in the comments below.