Introduction

Bronchodilators are prescribed to patients who receive poor ventilation through the lungs. Beta-2 agonists are responsible for targeting the smooth muscles that are present in the bronchioles of the lung and constitute the central component of treatment. Bronchodilators are necessary for a range of respiratory conditions which includes conditions such as chronic obstructive pulmonary disease and asthma. Patients with chronic obstructive pulmonary disease, are either used to reverse asthma symptoms or to enhance lung function.

This activity would provide interprofessional team members with a comprehensive understanding of bronchodilators' mechanism of action, adverse event profile, dosing, pharmacodynamics, and monitoring as they pertain to the treatment of patients with obstructive lung pathology.¹ It is important to understand the importance of bronchodilators in respiratory health. Bronchodilators would make the patient breathe easier. They are frequently employed to manage chronic conditions characterised by constriction and inflammation of the airways, which include:

1. Asthma: A prevalent pulmonary disorder characterised by constriction and inflammation of the airways
2. Chronic Obstructive Pulmonary Disorder (COPD): A group of smoke-related lung conditions that obstruct breathing² 

Bronchodilators may either be short-acting, which is used as short-term relief from sudden breathlessness and long-acting, which are regularly used to control breathlessness in asthma and COPD patients. Healthcare professionals must consider the patient’s cardiovascular status, especially if they have pre-existing heart conditions when prescribing bronchodilators. Additionally, patients using bronchodilators should be aware of any changes in heart rate and should seek medical attention if they experience significant or persistent cardiovascular symptoms. Always consult with a healthcare provider for personalised medical advice and information based on individual health circumstances. 

Types of bronchodilators

The 3 most widely used bronchodilators include:

Beta-2 agonists

Mechanism of actions:- Bronchial smooth muscle is targetted by beta-adrenergic agonists, which induce bronchodilation and alleviate bronchospasm in patients with asthma and chronic obstructive pulmonary disease with asthmatic symptoms. There is no association between their use in asthma and liver damage.³ 

Beta-2 Agonists include drugs such as Salbutamol, Salmeterol, Formoterol, and Vilanterol.²

Impact on heart rate:- The utilisation of Beta-s Agonists has been linked to an elevated likelihood of experiencing myocardial infarction, congestive heart failure, cardiac arrest, or sudden cardiac death.⁴ 

Anticholinergics

Mechanism of actions:- Anticholinergic medications are pharmaceutical substances that inhibit the actions of the neurotransmitter acetylcholine in both central and peripheral nervous systems. Through this mechanism, the Anticholinergics impair the activities of the parasympathetic nervous system. This is achieved through the selective inhibition of Ach receptor binding to neurons.⁵

Anticholinergics include drugs such as ipratropium and tiotropium.

Impact on heart rate: Anticholinergics elevate your heart rate, which could be used to treat bradycardia. 

Theophylline

Mechanism of actions: Smooth muscle situated in the bronchial airways and pulmonary blood vessels are relaxed by theophylline. Additionally, it diminishes the airway responsiveness to histamine, adenosine, methacholine, and allergens.⁶ 

Impact on heart rate: Theophylline improves the function of the right and left heart systolic pump function, while simultaneously reducing pulmonary artery pressure and pulmonary vascular resistance.⁷ 

Physiological basis of bronchodilators and heart rate

Bronchodilators are medications that relax and widen the airways (bronchi and bronchioles) in the respiratory system. They are commonly used to treat conditions such as asthma and COPD, where airway constriction is a significant problem.

Bronchodilators' mechanism of action would include selectively binding to the beta-2 receptor, a G-protein coupled receptor located in the lung's airways. Activation of the beta-2 receptor induces relaxation of the smooth muscle lining the airway. Following this, the patient undergoes a temporary improvement in breathing. Long-term consistent administration of beta-2 agonists diminishes their effectiveness as a result of beta-2 receptor downregulation in the airways.

Consequently, a greater dosage of medication is required to attain an equivalent outcome. The bronchodilator mechanism is facilitated by cytochrome P-450 enzyme in the gastrointestinal tract. Approximately 80% to 100% are eliminated via urine, while the faeces contain less than 20%. The half-life of short-acting bronchodilators is between 3 and 6 hours, whereas the longer-acting bronchodilators are between 18 and 24 hours. 

Anticholinergics inhibit the function of parasympathetic nervous system receptors located in the airways. Reversing the effects of the parasympathetic nervous system, which is accountable for constriction and increased bronchial secretions, should result in bronchodilation and decreased secretions.¹

Clinical applications

Asthma

Relief of acute symptoms: Short-acting bronchodilators, such as albuterol, are often used for quick relief of acute asthma symptoms, providing rapid bronchodilation during asthma attacks.

Maintenance therapy: Long-acting bronchodilators, such as formoterol and salmeterol, are used as part of maintenance therapy to control and prevent asthma symptoms.

Chronic Obstructive Pulmonary Disease (COPD)

Maintenance Therapy: Long-acting bronchodilators, including beta-agonists (e.g., formoterol, salmeterol) and anticholinergics (e.g., tiotropium, aclidinium), are commonly prescribed to manage COPD symptoms and improve lung function.

Combination Therapy: Some individuals with COPD may benefit from a combination of long-acting bronchodilators to achieve better control of symptoms.

Exercise-induced bronchoconstriction (EIB)

Short-acting bronchodilators can be used prophylactically before exercise to prevent or reduce exercise-induced bronchoconstriction in individuals with asthma or EIB.

Bronchodilator testing

Bronchodilators are used in pulmonary function testing to assess reversible airway obstruction. Spirometry is often performed before and after the administration of a bronchodilator to determine the degree of reversibility.

Preoperative bronchodilation

Bronchodilators may be administered before surgery in patients with known or suspected bronchospastic conditions to prevent perioperative bronchoconstriction.

Cystic fibrosis

Bronchodilators may be used in the management of cystic fibrosis to improve airway clearance and facilitate the delivery of other inhaled medications.

Neonatal Respiratory Distress Syndrome (NRDS)

In preterm infants with NRDS, bronchodilators may be used to improve airway patency and reduce the work of breathing.

Side effects 

Side effects of bronchodilators vary with the type:

Beta-2 Agonists

• Nervous or shaky feelings
• Overexitement
• Hyperactivity
• Increased heart rate
• Upset stomach
• Trouble sleeping

Anticholinergics

• Dry throat, eyes, and nose
• Unusual taste
• Nausea and Vomiting
• Temporary blurred vision if the medicine gets in your eye

Theophylline

• Nausea and Vomiting
• Stomach ache
• Diarrhea
• Headache
• Rapid or irregular heartbeat
• Muscle cramps
• Nervous or shaky feelings⁸

How do I use a bronchodilator inhaler

To obtain a complete dosage of a bronchodilator inhaler, appropriate use is crucial. Following these procedures will assist you in using a bronchodilator inhaler correctly.

• The inhaler should be shaken approximately 10 to 15 times. It is necessary to ensure that the cap is tight
• Remove the cap
• Breathe in and out
• Place your mouth around the mouthpiece
• The inhaler should be pressed down once
• A slow deep breath should be taken through your mouth
• Your breath should be held for 10 seconds. For the medication to reach the airways of the lungs, count slowly
• When you are finished using the inhaler, replace the cap⁸ 

Precautions and complications

Beta - 2 Agonists

• Hypothyroidism: Beta-2 Agonists have the potential to induce thyroid activity
• Diabetes Mellitus: A rare complication is ketoacidosis, which can occur particularly after intravenous beta-2 agonist administration 
• Cardiovascular disease: Beta-2 Agonists may precipitate arrhythmias and substantial alterations in blood pressure and heart rate in patients with cardiovascular disease⁹

Anticholinergics

• Respiratory failure
• Cardiovascular collapse
• Rhabdomyolysis
• Seizures
• Coma
• Permanent disability
• Death¹⁰ 

Theophylline

• Cardiovascular Disease
• Cystic Fibrosis
• Hepatic Failure
• Hyperthyroidism
• Peptic Ulcer Disease
• Seizure Disorder⁶

FAQs

Do bronchodilators raise heart rate?

Bronchodilators do increase heart rate. The possible side effect of bronchodilators is elevated heart rate.

Do inhalers make your heart rate faster?

If too much inhaler is used you may notice heart beating faster.

How do bronchodilators affect the cardiovascular system?

Cardiovascular effects including ischaemic events and arrhythmias are the side effects of bronchodilators.

Which inhalers increase heart rate?

Inhaled corticosteroids cause an increase in heart rate.¹¹

Summary

Bronchodilators are prescribed to patients with poor ventilation through the lungs. They are used in the management of Asthma and Chronic Obstructive Pulmonary Disease (COPD). Bronchodilators may be short-acting or long-acting and include types such as Beta-2 Agonists, Anticholinergics, and Theophylline. Clinical applications of bronchodilators include Asthma, Chronic Obstructive Pulmonary Disease, Exercise-induced bronchoconstriction, Bronchodilator testing, Preoperative bronchodilation, Cystic fibrosis, and Neonatal respiratory distress syndrome. Cardiovascular disease is a common side effect of bronchodilators and their continuous use result in an increased heart rate.