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Bronchoconstrictors

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1. Endogenous Chemical Mediators

Histamine

• Released primarily from mast cells during allergic reactions
• Acts on H1 receptors on bronchial smooth muscle (BSM), activating phospholipase C and protein kinase C (PKC), releasing Ca²⁺ from intracellular stores
• Leads to Ca²⁺ entry through calcium channels → sustained smooth muscle contraction
• Attenuated by atropine (cholinergic antagonist), indicating a reflex cholinergic component
• In humans with normal airways, small doses produce only modest bronchoconstriction; in asthmatic airways, much more potent — Miller's Anesthesia, 10e, p. 2065; Katzung's Basic and Clinical Pharmacology, 16e

Leukotrienes (Cysteinyl Leukotrienes: LTC₄, LTD₄, LTE₄)

• Produced via the lipoxygenase pathway from arachidonic acid
• Released by mast cells, eosinophils, basophils
• Up to 1,000× more potent than histamine as bronchoconstrictors
• Also increase mucus secretion, vascular permeability, and tissue fibrosis
• Major mediators in asthma and anaphylaxis
• Blocked by leukotriene receptor antagonists (montelukast, zafirlukast) and 5-LOX inhibitors (zileuton) — Henry's Clinical Diagnosis, p. 1757; Katzung's, p. 1529; Fishman's Pulmonary Diseases

Prostaglandins

• PGD₂, PGF₂α, and TXA₂ are potent bronchoconstrictors produced by eosinophils and mast cells
• PGF₂α and TXA₂ were once thought to be primary asthma mediators; polymorphisms in their receptor genes are linked with asthma
• PGE₂, in contrast, is a bronchodilator — Katzung's, p. 1924–1926; Fishman's Pulmonary Diseases

Acetylcholine (Parasympathetic/Vagal Tone)

• Postganglionic parasympathetic fibers release ACh → acts on M3 muscarinic receptors on airway smooth muscle → contraction
• M2 receptors on nerve endings act as autoreceptors (limit further ACh release)
• M1 receptors at ganglia facilitate neurotransmission
• The dominant neural bronchoconstrictor pathway; basis for anticholinergic bronchodilators (ipratropium, tiotropium) — Katzung's, p. 2553–2566; Miller's Anesthesia

Substance P and Tachykinins

• Released from C-fiber afferents in response to inhaled irritants
• Directly stimulate smooth muscle contraction (non-adrenergic, non-cholinergic mechanism) — Katzung's, p. 2553

Bradykinin

• Generated in allergic/inflammatory states
• Stimulates rapidly adapting airway receptors and provokes bronchoconstriction
• A significant trigger in asthma and in ACE-inhibitor-induced cough/bronchospasm

Serotonin (5-HT)

• Relevant in carcinoid syndrome — circulating serotonin + bradykinin + histamine cause flushing and bronchoconstriction; carcinoid crisis can cause life-threatening bronchospasm — Miller's Anesthesia

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2. Physiological/Reflexive Stimuli

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3. Pharmacological / Drug-Induced Bronchoconstrictors

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Neural Control of Airway Smooth Muscle

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Summary Table

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📝 ASSIGNMENT

Topic: BRONCHOCONSTRICTORS

Subject: Pharmacology / Respiratory Nursing

Format: Assignment (Deep & Easy Language)

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1. INTRODUCTION (Parichay)

Jaise ek pipe ka valve band karo — paani ki flow kam ho jaati hai. Usi tarah bronchoconstrictors airway ki "nali" ko tang kar dete hain, aur hawa ki flow kam ho jaati hai.

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2. DEFINITION (Paribhasha)

Bronchoconstrictors woh substances hain jo bronchial smooth muscle (airway ki deewar mein maujood muscle) ko contract karate hain, jis se airway ki diameter kam ho jaati hai aur saans lene mein takleef hoti hai.

• Endogenous (body ke andar se): Histamine, Leukotrienes, Acetylcholine
• Exogenous/Drugs se: Beta-blockers, NSAIDs, Carbachol
• Physiological Stimuli se: Thanda mausam, dhool, dhuaan, GERD (acid reflux)

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3. MECHANISM OF ACTION (Kaise Kaam Karte Hain)

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🔹 A. Histamine

1. Allergic reaction hone par mast cells se histamine release hoti hai
2. Histamine airway ki smooth muscle par H1 receptors se jud jaati hai
3. Isse Phospholipase C activate hota hai → calcium (Ca²⁺) cells ke andar aata hai
4. Calcium muscle ko contract karata hai → airway tang ho jaati hai
5. Yahi process asthma aur anaphylaxis mein hoti hai

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🔹 B. Acetylcholine (Parasympathetic Pathway)

1. Brain se signal aata hai → vagus nerve active hoti hai
2. Postganglionic nerves Acetylcholine (ACh) release karte hain
3. ACh airway muscle par M3 muscarinic receptors se milti hai
4. Isse smooth muscle contract hoti hai → bronchoconstriction
5. M2 receptors autoreceptors hain — yeh aur ACh release rokne ki koshish karte hain

Yahi wajah hai ki anticholinergic drugs (jaise Ipratropium) bronchoconstriction rokti hain

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🔹 C. Leukotrienes (LTC₄, LTD₄, LTE₄)

1. Arachidonic acid se Lipoxygenase enzyme ke zariye bante hain
2. Mast cells aur eosinophils inhe release karte hain
3. Airway smooth muscle par CysLT1/CysLT2 receptors se attach hote hain
4. Histamine se 1000 guna zyada powerful bronchoconstrictors hain
5. Alag se mucus secretion bhi badhate hain → aur zyada blockage
6. Asthma mein yeh dominant mediators hain

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🔹 D. Prostaglandins (PGF₂α, TXA₂, PGD₂)

1. COX pathway se arachidonic acid se bante hain
2. Airway smooth muscle par TP/FP receptors se kaam karte hain
3. Muscle contraction → bronchoconstriction
4. NSAIDs lene par COX block hota hai → zyada leukotrienes bante hain → bronchoconstriction worse hoti hai (Aspirin-Exacerbated Respiratory Disease)

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🔹 E. Beta-Blockers (Drug-Induced)

1. Normal mein β₂ receptors airway ko relax rakhte hain (bronchodilation)
2. Non-selective beta-blockers (jaise Propranolol) β₂ receptors block kar dete hain
3. Bronchodilation band → bronchoconstriction dominant ho jaati hai
4. Asthma patients mein jaan lewa ho sakta hai

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🔹 F. Substance P (Tachykinins)

1. Inhaled irritants (dhuaan, dhool) C-fiber nerve endings ko stimulate karte hain
2. Substance P release hoti hai
3. Yeh directly smooth muscle ko contract karati hai

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4. INDICATIONS (Kab Use Kiya Jata Hai)

Yaad rakhein: Bronchoconstrictors ke induced effects ko treat karna (bronchodilators dena) — yeh nursing practice mein zyada kaam aata hai.

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5. CONTRAINDICATIONS (Kab Nahi Dena Chahiye)

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6. SIDE EFFECTS (Samanye Prabhav — Common Effects)

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7. ADVERSE EFFECTS (Gambhir/Serious Effects)

"Propranolol is contraindicated in patients with bronchial asthma. Death by asphyxiation has been reported." — Lippincott Illustrated Reviews: Pharmacology

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8. NURSING MANAGEMENT (Nurse Ki Zimmedari)

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🩺 A. Assessment (Muayana karna)

1. Patient ki respiratory rate, depth, aur effort check karo
2. Oxygen saturation (SpO₂) monitor karo — normal >95%
3. Auscultation karo — wheezing, rhonchi sunai de rahi hai kya
4. Peak Flow Meter reading lo asthma patients mein
5. Patient se puchho — shortness of breath, chest tightness, cough hai kya
6. Allergy history lo — kisi drug ya substance se reaction toh nahi
7. Drug history lo — beta-blockers, NSAIDs, aspirin to use nahi ho rahi
8. Triggers identify karo — dust, smoke, cold air, GERD, stress

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🩺 B. Diagnosis (Nursing Diagnosis)

1. Ineffective Airway Clearance — airway mein blockage hai
2. Impaired Gas Exchange — O₂ aur CO₂ sahi se exchange nahi ho raha
3. Activity Intolerance — saans ki takleef ki wajah se movement mushkil
4. Anxiety — saans na aane ka darr
5. Risk for Respiratory Failure — severe cases mein

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🩺 C. Interventions (Kya Karna Chahiye)

1. Patient ko upright (60–90°) position mein bithao — isse breathing easy hoti hai
2. Oxygen therapy dena — mask/nasal cannula se O₂ dena — SpO₂ maintain karo
3. Bronchodilator dena as prescribed — Salbutamol (Albuterol) nebulization sabse pehle
4. IV access banao — emergency drugs dene ke liye
5. Epinephrine (Adrenaline) — anaphylaxis mein 0.3–0.5 mg IM (doctor order par)

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🩺 D. Patient Education (Mareez Ko Sikhaana)

1. Inhaler technique sahi se sikhao — MDI ya spacer ka use
2. Triggers avoid karo: Dhuaan, dhool, cold air, pets, strong smells
3. Medications kabhi band mat karo bina doctor se pooche
4. Beta-blockers aur NSAIDs se bacho asthma patients mein
5. GERD control karo — acid reflux asthma trigger kar sakta hai
6. Action plan do — kaun se symptoms mein doctor ke paas jaana hai
7. Peak flow meter use karna sikhao — apni condition monitor karne ke liye
8. Stress management — deep breathing, meditation (but over-relaxation se vagal tone na badhe)

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🩺 E. Evaluation (Result Check karna)

1. Kya patient ki saans normal ho gayi?
2. SpO₂ 95% se upar hai?
3. Wheezing kam hui ya band ho gayi?
4. Patient comfortable feel kar raha hai?
5. Anxiety kam hui?
6. Patient ne triggers avoid karna seekh liya?

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📌 SUMMARY TABLE

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References:

• Miller's Anesthesia, 10th Edition
• Katzung's Basic & Clinical Pharmacology, 16th Edition
• Lippincott Illustrated Reviews: Pharmacology
• Goodman & Gilman's Pharmacological Basis of Therapeutics
• Fishman's Pulmonary Diseases and Disorders

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📝 ASSIGNMENT

Topic: BRONCHOCONSTRICTORS

Subject: Pharmacology / Respiratory Nursing

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1. INTRODUCTION

• Natural body chemicals (released during allergic reactions or inflammation)
• Drugs (that narrow airways as a main or side effect)
• Physical triggers (cold air, smoke, stress)

Think of it this way: Airways are like a water pipe. Bronchoconstrictors are like squeezing that pipe — less air can pass through, causing breathlessness, wheezing, and chest tightness.

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2. DEFINITION

Bronchoconstrictors are substances (endogenous or exogenous) that cause contraction of bronchial smooth muscle, resulting in narrowing of the airway lumen, reduced airflow, and difficulty in breathing.

Types:

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3. MECHANISM OF ACTION

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🔹 A. Histamine

1. During an allergic reaction, mast cells are activated and release histamine
2. Histamine binds to H1 receptors on bronchial smooth muscle
3. This activates Phospholipase C and Protein Kinase C (PKC)
4. These enzymes trigger release of calcium (Ca²⁺) from intracellular stores
5. Calcium causes smooth muscle to contract → airway narrows
6. Additionally, histamine stimulates vagal afferent nerves → reflex bronchoconstriction
7. The enzyme histamine N-methyltransferase in the airway epithelium helps break down histamine and provides some natural protection

Key point: Volatile anesthetics (halothane, sevoflurane, isoflurane) can inhibit histamine-induced bronchoconstriction — important in anesthesia nursing.

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🔹 B. Acetylcholine (Parasympathetic/Vagal Pathway)

1. A stimulus (irritant, emotion, cold air) activates the vagus nerve
2. Preganglionic fibers synapse at parasympathetic ganglia in the airway wall
3. Postganglionic fibers release Acetylcholine (ACh)
4. ACh binds to M3 muscarinic receptors on airway smooth muscle → contraction
5. ACh also binds to M1 receptors at ganglia → facilitates neurotransmission
6. M2 receptors on nerve endings act as autoreceptors → try to limit further ACh release
7. Net result: bronchoconstriction + increased mucus secretion

This is the dominant neural pathway for bronchoconstriction. Anticholinergic drugs (Ipratropium, Tiotropium) block M3 receptors and are used as bronchodilators.

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🔹 C. Leukotrienes (LTC₄, LTD₄, LTE₄)

1. Cell membranes contain arachidonic acid
2. During inflammation, the enzyme 5-Lipoxygenase (5-LOX) converts it into cysteinyl leukotrienes
3. Released by mast cells, eosinophils, and basophils
4. Bind to CysLT1 and CysLT2 receptors on airway smooth muscle
5. Cause powerful smooth muscle contraction → severe bronchoconstriction
6. Additionally cause: mucus hypersecretion, mucosal edema, vascular permeability
7. Are up to 1,000 times more potent than histamine
8. Dominant mediators in chronic asthma

Blocked by: Montelukast, Zafirlukast (leukotriene receptor antagonists); Zileuton (5-LOX inhibitor)

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🔹 D. Prostaglandins (PGF₂α, TXA₂, PGD₂)

1. Also derived from arachidonic acid via the COX (Cyclooxygenase) pathway
2. Released from mast cells and eosinophils
3. Bind to TP, FP, and DP2 receptors on airway smooth muscle
4. Cause direct smooth muscle contraction → bronchoconstriction
5. NSAIDs block COX → arachidonic acid is diverted to lipoxygenase pathway → more leukotrienes → worse bronchoconstriction (this is the basis of Aspirin-Exacerbated Respiratory Disease)

PGE₂ is the exception — it causes bronchodilation, not constriction.

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🔹 E. Beta-Blockers (Drug-Induced Mechanism)

1. Normally, β₂ adrenergic receptors on airway smooth muscle maintain bronchodilation (relaxation)
2. Non-selective beta-blockers (e.g., Propranolol) block both β₁ and β₂ receptors
3. Blocking β₂ removes the bronchodilatory tone → bronchoconstriction dominates
4. In asthmatic patients, this can be life-threatening

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🔹 F. Substance P (Tachykinins)

1. Inhaled irritants (dust, smoke, chemicals) stimulate C-fiber nerve endings in the airway
2. These fibers release Substance P (a neuropeptide/tachykinin)
3. Substance P directly acts on NK1/NK2 receptors on smooth muscle → contraction
4. Also enhances the release of other mediators like histamine

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🔹 G. Bradykinin

1. Generated during inflammation and allergic reactions
2. Stimulates rapidly adapting receptors in the airways
3. Causes direct smooth muscle contraction and triggers vagal reflexes
4. Also responsible for ACE inhibitor-induced cough and sometimes bronchospasm

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4. INDICATIONS (When Are Bronchoconstrictors Used?)

Important: Nurses use this knowledge to manage the consequences of bronchoconstriction (e.g., asthma attack, anaphylaxis, drug reaction) rather than administer bronchoconstrictors themselves.

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5. CONTRAINDICATIONS (When Should They Be Avoided?)

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6. SIDE EFFECTS (Common / Mild Effects)

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7. ADVERSE EFFECTS (Serious / Dangerous Effects)

"Propranolol is contraindicated in patients with bronchial asthma. Death by asphyxiation has been reported for patients with asthma who inadvertently received the drug." — Lippincott Illustrated Reviews: Pharmacology

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8. NURSING MANAGEMENT

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🩺 A. Assessment

1. Assess respiratory rate, rhythm, and depth — normal 12–20 breaths/min
2. Monitor oxygen saturation (SpO₂) continuously — normal >95%
3. Auscultate lung sounds — listen for wheezing, crackles, or absent breath sounds
4. Observe for use of accessory muscles (neck, chest, abdomen) — sign of respiratory distress
5. Assess skin color — pallor or cyanosis indicates hypoxia
6. Measure peak expiratory flow rate (PEFR) in asthma patients

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🩺 B. Nursing Diagnoses

1. Ineffective Airway Clearance related to bronchospasm and excessive mucus secretion
2. Impaired Gas Exchange related to narrowed airways and reduced alveolar ventilation
3. Ineffective Breathing Pattern related to bronchoconstriction
4. Activity Intolerance related to dyspnea and reduced oxygen availability
5. Anxiety related to difficulty breathing and fear of suffocation
6. Deficient Knowledge related to triggers, medications, and self-management
7. Risk for Respiratory Failure in severe/uncontrolled bronchospasm

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🩺 C. Planning & Interventions

🔴 Immediate / Emergency Interventions:

1. Position the patient upright (60°–90°, Fowler's position) — gravity helps expand lungs and reduces work of breathing
2. Administer supplemental oxygen via nasal cannula or mask — maintain SpO₂ >95%
3. Administer prescribed bronchodilators immediately:
   • Salbutamol (Albuterol) via nebulizer — first-line for acute bronchospasm
   • Ipratropium bromide — anticholinergic bronchodilator (blocks M3 receptors)
4. Establish IV access — for emergency drug administration
5. Administer Epinephrine (Adrenaline) 0.3–0.5 mg IM in anaphylaxis — as per doctor's order
6. Call the physician immediately if patient does not respond within minutes
7. Prepare for intubation if respiratory failure is imminent

🟡 Ongoing / Supportive Care:

1. Remove or eliminate the trigger — allergen, irritant, offending drug
2. Administer IV corticosteroids as ordered — reduce airway inflammation
3. Encourage pursed-lip breathing and controlled breathing techniques
4. Ensure adequate hydration — oral or IV fluids thin the mucus secretions
5. Perform chest physiotherapy / suction if secretions are blocking airways
6. Monitor vital signs every 15–30 minutes during acute episode
7. Attach pulse oximetry for continuous SpO₂ monitoring
8. Reassure the patient — anxiety worsens bronchospasm by increasing respiratory rate

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🩺 D. Patient & Family Education

1. Teach correct inhaler technique — MDI with spacer or dry powder inhaler (DPI)
2. Educate about triggers and how to avoid them:
   • No smoking (active or passive)
   • Avoid dust, pollen, animal dander, strong perfumes
   • Avoid cold and dry air — use a scarf over mouth in winter
   • Control GERD — eat small meals, avoid lying flat after eating
3. Never stop medications suddenly — especially inhaled corticosteroids
4. Avoid beta-blockers and NSAIDs/aspirin unless specifically approved by doctor
5. Teach use of Peak Flow Meter — to monitor airway status at home daily
6. Provide written Asthma Action Plan:
   • Green zone (>80% peak flow) = routine medications
   • Yellow zone (50–80%) = increase bronchodilator + call doctor
   • Red zone (<50%) = emergency — go to hospital immediately
7. Stress management — teach relaxation techniques carefully (note: excessive vagal activation can worsen bronchoconstriction)
8. Regular follow-up — emphasize importance of scheduled clinic visits

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🩺 E. Evaluation (Outcome Criteria)

1. ✅ Patient's SpO₂ returns to ≥95%
2. ✅ Respiratory rate normalizes (12–20 breaths/min)
3. ✅ Wheezing and chest tightness resolved or significantly reduced
4. ✅ Patient able to speak in full sentences without breathlessness
5. ✅ Peak flow returns to ≥80% of personal best
6. ✅ Patient is calm and not anxious
7. ✅ Patient can correctly demonstrate inhaler use
8. ✅ Patient can identify personal triggers and explain how to avoid them

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📌 QUICK SUMMARY TABLE

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References:

• Miller's Anesthesia, 10th Edition
• Katzung's Basic & Clinical Pharmacology, 16th Edition
• Lippincott Illustrated Reviews: Pharmacology
• Goodman & Gilman's Pharmacological Basis of Therapeutics
• Fishman's Pulmonary Diseases and Disorders
• Robbins & Kumar Basic Pathology