Acute Asthma - Part 2: When it Starts Winning

Rescue therapies, ventilation strategy, and preventing the spiral into respiratory failure

Asthma rarely fails suddenly. It fails progressively—and then all at once.

The patient who looked “tight but stable” an hour ago is now:

• Exhausted

• Silent

• Hypercapneic

And the physiology has shifted.

This is no longer about broncho-dilation.
This is about ventilation, mechanics, and survival.

In severe asthma, the danger is not hypoxia—it is failure to ventilate.

Recognising the Turn: When Compensated Becomes Pre-terminal

Early asthma is loud.
Severe asthma is often quiet.

Red flags of impending respiratory failure:

• Rising or normal PaCO₂

• Exhaustion / reduced respiratory effort

• Altered mentation

• Silent chest

• Bradycardia (late)

A normal PaCO₂ in acute asthma is not reassuring—it is a warning of imminent collapse (Cahill et al., 2025).

What is happening physiologically?

• Airflow obstruction worsens

• Expiratory time becomes insufficient

• Dynamic hyperinflation increases

• Intra-thoracic pressure rises

• Venous return falls

• Cardiac output drops

(Mein & Ferrera, 2025)

‘The patient is not tiring because they are hypoxic—they are tiring because they cannot exhale.’

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Adjuncts and Escalation: What Actually Works

Once initial therapy fails, escalation must be targeted—not reflexive.

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Ketamine in Acute Asthma:

Rescue Bronchodilator, Not Routine Therapy

Ketamine occupies a unique space in acute asthma—pharmacologically appealing, clinically inconsistent, and often used when options are running out.

Where does Ketamine fit?

Ketamine is best understood as a rescue therapy in refractory status asthmaticus—not as routine ED treatment.

It is typically considered when:

• Severe asthma persists despite maximal inhaled therapy + steroids ± magnesium

• The patient is deteriorating toward intubation

• Or as the induction agent of choice during RSI

(Goyal & Agrawal, 2013; La Via et al., 2022)

Mechanism: Why it makes sense

Ketamine produces broncho-dilation through multiple pathways:

• NMDA receptor antagonism

• Increased endogenous catecholamines → β₂ stimulation

• Reduced vagal tone

• Direct smooth muscle relaxation

(Goyal & Agrawal, 2013; La Via et al., 2022)

It also demonstrates:

• Anti-inflammatory effects

• Reduction in airway hyperresponsiveness (experimental data)

(Xiao et al., 2022)

Dosing (acute care context)

• Induction (RSI):

  • 1–2 mg/kg IV

• Infusion (refractory cases):

  • 0.5–2 mg/kg/hour

(Ueoka et al., 2021; Goyal & Agrawal, 2013)

What does the evidence say?

Despite strong physiological rationale:

• Systematic reviews show no consistent benefit in ED patients

• RCTs demonstrate minimal or no improvement over standard therapy

• Meta-analysis shows non-significant improvement in PEF

(La Via et al., 2022; Alshehri et al., 2022)

In contrast:

• ICU case series in life-threatening status asthmaticus report:

  • Improved pH and PaCO₂

  • Reduced airway pressures

  • Facilitation of ventilator weaning

(Heshmati et al., 2003; Ueoka et al., 2021)

Adverse effects

• Hallucinations / dysphoria

• Increased secretions

• Tachycardia, hypertension

Usually manageable with:

• Sedation

• Anticholinergics

(La Via et al., 2022; Binsaeedu et al., 2023)

Clinical takeaway

Ketamine is not a bronchodilator you reach for early—it is one you reach for when everything else is failing.

Its strongest roles:

• RSI induction in asthmatics

• Adjunct infusion in refractory, intubated patients

Adrenaline (Epinephrine) in Asthma:
Old Drug, New Role

Adrenaline was once the cornerstone of asthma therapy. Today, its role is far more selective.

Mechanism

• β₂ → bronchodilation

• α₁ → reduces airway edema

• β₁ → increases cardiac output

(Baggott et al., 2021; Mclean-Tooke et al., 2003)

Effectiveness vs β₂-agonists

Modern evidence shows:

Adrenaline is not superior to inhaled β₂-agonists.

• Equivalent efficacy

• No reduction in treatment failure

• More cardiovascular side effects

(Baggott et al., 2021)

Current role: Not routine

Adrenaline should not be used routinely in asthma exacerbations.

Selective β₂-agonists (e.g., salbutamol) are:

• Safer

• Equally effective

(Indinnimeo et al., 2018)

When should you use adrenaline?

1. Asthma or Anaphylaxis (critical indication)

Adrenaline is first-line therapy here.

• Treats bronchospasm

• Reduces airway edema

• Prevents cardiovascular collapse

(Cardona et al., 2020; Ring et al., 2018)

2. Severe, refractory asthma (rescue use)

Consider when:

• Inhaled therapy is ineffective or not feasible

• Patient is deteriorating rapidly

Dosing

IM adrenaline:

• 0.3–0.5 mg (1:1000)

• Repeat every 20 minutes (max 3 doses)

SC terbutaline alternative:

• 0.25 mg every 20 minutes (max 0.75 mg)

(McFarlin et al., 2026; Leung, 2021)

Emerging data:

• Recent RCT suggests low-dose SC adrenaline may improve airflow and oxygenation when added to standard therapy

(Gong et al., 2024)

Cautions

• Tachy-arrhythmias

• Hypertension

• Myocardial ischemia (rare but relevant in older patients)

Clinical takeaway

Adrenaline is no longer a first-line bronchodilator—it is a situational drug.

Use it when:

• There is anaphylaxis

• Or severe asthma where inhaled therapy cannot be delivered effectively

Integrated Clinical Insight

Ketamine and adrenaline share a similar theme:

Both are powerful drugs—but neither belongs in routine asthma care.

They are:

• Not first-line

• Not substitutes for proper broncho-dilation

• Not replacements for steroids

They are:

• Bridging therapies in extreme physiology

In asthma, the right drug at the wrong time is as dangerous as the wrong drug.

Magnesium Sulfate: Selective but Effective

Dose:

• 2 g IV over 20–30 minutes

Mechanism:

• Smooth muscle relaxation

• Calcium antagonism

Evidence:

• Improves lung function

• Reduces hospitalisation in severe exacerbations

Magnesium is not a routine drug—it is a severity marker.

Use when:

• Persistent severe obstruction after initial therapy

(Cahill et al., 2025; McFarlin et al., 2026)

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Non-Invasive Ventilation (NIV): A Narrow Window

NIV can:

• Reduce work of breathing

• Improve ventilation

• Delay or prevent intubation

But only in the right patient:

• Awake and cooperative

• Hemodynamically stable

• No impending arrest

Typical starting settings:

• IPAP: ~8 cm H₂O

• EPAP: ~3 cm H₂O

(McFarlin et al., 2026)

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NIV is a bridge—not a rescue for the crashing patient.

Evidence remains limited; use cautiously (Mein & Ferrera, 2025).

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Systemic Beta-Agonists: Rescue Only

Not routine—but lifesaving in specific contexts.

Indications:

• Failure of inhaled therapy

• Inability to effectively inhale

Terbutaline (SC):

• 0.25 mg every 20 minutes (max 0.75 mg)

(McFarlin et al., 2026)

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If the drug cannot reach the airway, change the route.

What Not to Do (Evidence-Based De-adoption)

Modern asthma care is defined as much by what we avoid:

• ❌ Aminophylline / theophylline → toxicity without benefit

• ❌ Routine antibiotics → mostly viral triggers

• ❌ Aggressive IV fluids → worsens pulmonary mechanics

• ❌ Mucolytics / chest physiotherapy → no benefit

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In asthma, unnecessary treatments are not neutral—they are harmful.

(Mein & Ferrera, 2025; Farkas, 2024)

The Crashing Asthmatic: The Intubation Trap

Intubation in asthma is high-risk.

It can:

• Worsen hyperinflation

• Cause hypotension

• Precipitate cardiac arrest

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The goal is not to intubate early—it is to intubate safely, when unavoidable.

When to Intubate

• Altered mental status

• Exhaustion

• Rising CO₂

• Refractory hypoxemia

• Failure of maximal therapy

(Cahill et al., 2025)

Intubation Strategy: Physiology First

Induction:

• Ketamine 1–2 mg/kg IV

Why?

• Bronchodilator

• Preserves hemodynamics

(McFarlin et al., 2026)

Tube:

• Use larger ETT → reduces resistance

Ventilation Strategy: This Determines Survival

The ventilator can save—or kill—the patient.

Core principles:

• Tidal volume: ~6 mL/kg IBW

• Respiratory rate: 8–12/min

• I:E ratio: ≥1:3

• Low or minimal PEEP

Why?

To:

• Maximise expiratory time

• Reduce air trapping

• Prevent barotrauma

(Mein & Ferrera, 2025; McFarlin et al., 2026)

Permissive Hypercapnia

• Accept PaCO₂ 70–100 mmHg

• Maintain pH ≥7.15

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Trying to normalise CO₂ in asthma is a common and dangerous mistake.

Post-intubation Collapse: The Critical Pearl

If the patient becomes:

• Hypotensive

• Hypoxic

Think:

Dynamic hyperinflation (auto-PEEP)

Immediate action:

• Disconnect ventilator

• Allow full exhalation

This can rapidly restore hemodynamics (Mein & Ferrera, 2025).

Beyond the ED:

The Next 7 Days Matter More Than the Next 7 Minutes

An exacerbation is a risk marker for future deterioration.

Discharge Essentials

Every patient should leave with:

• Systemic steroids (5–7 days)

• ICS-based controller therapy

• Early follow-up (2–7 days)

(Cahill et al., 2025; GINA, 2025)

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🔄 The Big Shift: ICS-Based Reliever Therapy

SABA-only therapy is obsolete.

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Preferred strategy (GINA 2025):

• ICS–formoterol as reliever (SMART/MART)

Benefits:

• ↓ exacerbations

• ↓ hospitalisations

• ↓ steroid exposure

(GINA, 2025)

The Most Underrated Intervention: Education

• Correct inhaler technique

• Provide written action plan

• Address triggers and comorbidities

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The best way to treat asthma in the ED is to prevent the next visit.

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🧠 Final Clinical Synthesis

Acute asthma is a disease of:

• Airflow limitation

• Time-sensitive escalation

• Ventilatory mechanics

Recognise early. Escalate appropriately. Ventilate gently. Discharge intelligently.

Final Take-home

Asthma kills by air trapping—not hypoxia. Treat accordingly.

References (AMA Style)

1. Mein SA, Ferrera MC. Management of asthma and COPD exacerbations in adults in the ICU. Chest Crit Care. 2025;3(1):100107.

2. Cahill KN, Dixon AE, Zachrison KS. Acute exacerbations of asthma in adults: Emergency department and inpatient management. UpToDate. Updated September 2025.

3. Global Initiative for Asthma (GINA). Global Strategy for Asthma Management and Prevention. 2025 update.

4. McFarlin A, Chan C, Winters M, et al. Asthma in adults. EM:RAP CorePendium. Updated February 2026.

5. Farkas J. Asthma. EMCrit Project. January 2024.

6. Helman A, Sommer L, Mal S. The crashing asthmatic: Recognition and management of life-threatening asthma. Emergency Medicine Cases. April 2024.

7. Morris MJ, Mosenifar Z. Asthma guidelines: Guidelines summary. Medscape. Updated March 2026.

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13. Binsaeedu A, Prabakar D, Ashkar M, et al. Safety and efficacy of ketamine in acute asthma exacerbation. Cureus. 2023;15.

14. Xiao S, Zhou Y, Wang Q, Yang D. Ketamine attenuates airway inflammation via Nrf2 pathway. Drug Des Devel Ther. 2022;16:4411–4428.

15. Baggott C, Hardy J, Sparks J, et al. Epinephrine versus β₂-agonists in acute asthma: systematic review and meta-analysis. Thorax. 2021;77:563–572.

16. Indinnimeo L, Chiappini E, Del Giudice M, et al. Guideline on management of acute asthma attack in children. Ital J Pediatr. 2018;44.

17. Cardona V, Ansotegui IJ, Ebisawa M, et al. World allergy organization anaphylaxis guidance. World Allergy Organ J. 2020;13.

18. Ring J, Klimek L, Worm M. Adrenaline in acute treatment of anaphylaxis. Dtsch Arztebl Int. 2018;115:528–534.

19. Gong W, Jiang J, Fan H. Low-dose adrenaline in severe asthma. Pharm Bioprocess. 2024;6:106–112.

20. Leung J. Acute asthma exacerbations management. Drugs Context. 2021;10.