What are the possible causes of shaking (tremor) in a patient with chronic obstructive pulmonary disease?

Causes of Shaking (Tremor) in COPD Patients

The most common cause of shaking in COPD patients is medication-induced tremor from β2-agonist bronchodilators (such as albuterol/salbutamol or formoterol), which occurs in a dose-dependent manner and represents an exaggerated somatic response to β2-adrenergic receptor stimulation. 1

Medication-Related Causes (Most Common)

β2-Agonist Bronchodilators

• Exaggerated somatic tremor occurs in some patients treated with higher doses of β2-agonists, which are central to COPD management 1
• Both short-acting β2-agonists (SABAs like albuterol) and long-acting β2-agonists (LABAs like formoterol) can cause tremor through β2-adrenergic receptor stimulation 1
• Tremor severity increases in a dose-dependent manner with salbutamol administration 2
• Common side effects of formoterol specifically include tremor, nervousness, and muscle cramps 3
• The tremor is typically postural (worse with arms outstretched) and worsens with exhaustion 2

Other Medications

• Theophylline, used as a bronchodilator in COPD, is associated with dose-related toxicity that can include tremor 1
• Benzodiazepines (sometimes used for anxiety in COPD patients) can paradoxically cause tremor as an adverse effect 4

Metabolic and Physiological Causes

Hypercapnia (Elevated CO2)

• Flapping tremor (asterixis) is a classic sign of hypercapnia, which can occur during acute exacerbations or in patients with severe stable COPD 1, 5
• Other signs of hypercapnia include bounding pulse and drowsiness, though a high PaCO2 can occur without these signs 1
• These symptoms require emergency evaluation 5

Hypoxemia

• Severe hypoxemia can contribute to tremor and altered mental status 5
• Oxygen saturation <94% warrants specialist referral 5

Electrolyte Abnormalities

• β2-agonists can cause hypokalemia (low potassium), which may manifest as muscle spasm, muscle weakness, or tremor 3
• Hyperglycemia is another metabolic consequence of β2-agonist therapy 3

Cardiovascular Causes

Cardiac Effects of Bronchodilators

• β2-agonists can cause fast or irregular heartbeat, which may be accompanied by tremor 3
• Stimulation of β2-adrenergic receptors can precipitate cardiac rhythm disturbances in susceptible patients 1

Systemic and Comorbid Conditions

COPD-Related Systemic Effects

• COPD is a systemic disorder with weight loss and dysfunction of respiratory and skeletal muscles 6
• Muscle weakness and fatigue are common in severe COPD and may manifest as tremulousness 1

Comorbidities

• Anxiety and depression are common comorbidities in COPD that can cause or exacerbate tremor 1
• Cardiovascular disease, which frequently coexists with COPD, may contribute to tremor 1

Clinical Approach to Tremor in COPD

Immediate Assessment Priorities

• Review all current medications, particularly β2-agonist dosing and frequency 1, 3
• Assess for signs of hypercapnia: altered mental status, drowsiness, bounding pulse, flapping tremor 1, 5
• Check oxygen saturation; if <94%, obtain arterial blood gas 5
• Evaluate for signs of severe exacerbation: tachypnea, tachycardia, accessory muscle use, cyanosis 7, 5

Management Strategy

• If tremor is medication-related and bothersome, consider dose reduction or switching to alternative bronchodilator classes (e.g., from SABA to long-acting muscarinic antagonist/LAMA) 1
• LAMAs (such as tiotropium) do not cause tremor and may be preferred in patients with troublesome β2-agonist side effects 1
• If hypercapnia is present, this requires urgent intervention and possible hospitalization 5
• Check serum potassium if patient is on high-dose β2-agonists 3

Key Pitfall to Avoid

• Do not assume tremor is simply a benign medication side effect without ruling out hypercapnia, especially if accompanied by altered mental status or drowsiness, as this represents a life-threatening emergency 1, 5