Can creatine kinase (CK) levels be elevated in asthmatic patients?

Creatine Kinase Elevation in Asthmatic Patients

Yes, creatine kinase (CK) can be elevated in asthmatic patients, particularly during severe exacerbations and in those receiving certain treatments. The elevation is primarily due to increased work of respiratory muscles during periods of airway obstruction and may also be influenced by specific asthma medications.

Mechanisms of CK Elevation in Asthma

• CK elevation in asthma is primarily derived from skeletal muscle, specifically respiratory muscles, due to the increased work of breathing during exacerbations 1
• During severe asthma attacks requiring mechanical ventilation, a surprisingly high incidence (76%) of CK elevation has been documented, with median levels reaching 1,575 U/L 2
• The CK elevation correlates with the severity of subjective symptoms and objective measurements of airway obstruction, such as forced expiratory volume in one second (FEV1) 1

Medication-Related CK Elevation

• Beta-2 adrenergic agonists commonly used in asthma treatment may contribute to CK elevation:
  • Intravenous salbutamol administration has been associated with significant increases in CK-MB activity in asthmatic patients 3
  • Subcutaneous terbutaline treatment in patients with brittle asthma has been linked to higher median serum total CK activity (211 units/L) compared to control groups (120 units/L) 4
• Importantly, the CK elevation seen with beta-agonist treatment appears to be primarily from skeletal muscle rather than cardiac origin, as cardiac-specific isoenzyme components were not elevated in studies 4

Clinical Significance and Monitoring

• CK elevation in asthma typically involves the skeletal muscle isoenzyme rather than the cardiac isoenzyme (CK-MB), suggesting that the source is respiratory muscles rather than cardiac injury 1
• In patients with severe asthma requiring mechanical ventilation, the presence of myopathy or CK enzyme rise is associated with significant prolongation of ventilation time 2
• When evaluating CK elevation in asthmatic patients, it's important to consider other potential causes, including steroid-induced myopathy, especially in patients on high-dose corticosteroids 5

Differentiating from Other Causes

• When encountering elevated CK in asthmatic patients, clinicians should consider:
  • Steroid-induced myopathy, which can occur in patients with refractory asthma on high-dose corticosteroids 5
  • Potential medication effects, particularly from beta-agonists 3, 4
  • Respiratory muscle fatigue from increased work of breathing 1
  • Other causes of myopathy that may coexist with asthma 5

Monitoring Recommendations

• Consider baseline CK measurement in asthmatic patients, particularly those with severe or refractory disease, to aid in later clinical decision-making 5
• Monitor CK levels during severe exacerbations, especially in patients requiring mechanical ventilation 2
• For patients on high-dose beta-agonist therapy (especially parenteral forms), periodic CK monitoring may be warranted 3, 4

CK elevation in asthmatic patients is a relatively common finding that primarily reflects increased respiratory muscle work during periods of airway obstruction, with potential contributions from medication effects. While generally not indicating cardiac injury, it can serve as a marker of disease severity and may have implications for ventilation duration in severe cases.