Theophylline
Theophylline is a phosphodiesterase inhibitor with a narrow therapeutic range that can cause life-threatening toxicity by two major mechanisms:
- Adenosine receptor blockade
Therapeutic bronchodilation, but also:- Tachycardia
- Tachyarrhythmias
- Seizures
- Cerebral vasoconstriction
- Phosphodiesterase inhibition
↑ Adrenergic activation and circulating catecholamines, with ↑ up to:- 4-8 times normal for adrenaline
- 4-10 times normal for noradrenaline
Epidemiology and Risk Factors
Pathophysiology
Aetiology
Clinical Features
Assessment
History:
Exam:
Investigations
Bedside:
Laboratory:
- Blood
- Theophylline level
- Confirms ingestion
- <10mg/ml: Gastrointestinal symptoms
- 10-30mg: Tachycardia and arrhythmias
- 30-60mg/L: Seizures, malignant arrhythmias
- Theophylline level
Imaging:
Other:
Diagnostic Approach and DDx
Management
- Activated charcoal
- Treat arrhythmias and seizures
- RRT
- Correct electrolytes
Resuscitation:
- C
- Arrhythmias
- β-blockers ideal in the non-asthmatic patient
- Diltiazem or verapamil otherwise
- Arrhythmias
- D
- Seizures
- Benzodiazepines
- Seizures
Avoid phenytoin as it may worsen seizures.
Specific therapy:
Theophylline undergoes significant enterohepatic recirculation and so activated charcoal is effective.
- Pharmacological
- Activated charcoal
Give multi-dose for slow-release preparations or toxicity.
- Activated charcoal
- Procedural
- RRT
- Physical
Supportive care:
Disposition:
Preventative:
Marginal and Ineffective Therapies
Anaesthetic Considerations
Complications
- F
- Electrolyte abnormalities
- Hypokalaemia
- Hypomagnesaemia
- Hypercalcaemia
- Hyperglycaemia
- Rhabdomyolysis
- Electrolyte abnormalities
Prognosis
Key Studies
References
- Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.