Bronchial Asthma

Bronchial Asthma

Perioperative Management

Asthma

Asthma is a chronic pulmonary disease characterized by airway inflammation and hyper-responsiveness

Results in episodic wheezing, coughing, breathlessness, chest tightness, and reversible airflow obstruction

Contributing factors include genetics, atopy, and respiratory syncytial virus infection in infancy

Common environmental triggers are pollen, mold, animals, dust, tobacco smoke, and anxiety.

Asthma

It is estimated that up to 300 million people are affected worldwide

Asthma prevalence of 7.7% for adults and 9.5% for children, with a slightly higher prevalence in women (9.2%) than in men (7.0%)

The overall number of asthma-related hospitalizations and deaths has decreased, possibly due to improved prevention of attacks through inhaled steroid use and novel pharmaceutical agents introduced over the past decade

Pathophysiology

Bronchoconstriction results from contraction of bronchial smooth muscle induced by a myriad possible stimuli

Vagal and sympathetic factors directly modulate airway tone

Inflammatory edema and mucous plugging exacerbate airflow limitation and progressively impair the response to bronchodilator therapy.

Airway remodeling, thickening, and abnormal communications between the injured airway epithelium and the pulmonary mesenchyme confer resistance to corticosteroid therapy as well

Pathophysiology

The immunologic-inflammatory pathways involved in the pathogenesis of asthma are complex and include lymphocytes immunoglobulin E, eosinophils neutrophils, mast cells, leucotrienes, and cytokines

These pathways are triggered and modified by extrinsicand environmental factors

Thus, asthma ultimately represents a dynamic interaction between host and environmental factors

Triggering Factors For Bronchospasm

Cardiopulmonary Effects

Progressive acute bronchoconstriction rapidly leads to

Increased work of breathing (WOB)

Decreased airflow

Air trapping

Dynamic hyperinflation

Ventilationperfusion (V/Q) mismatch

Increased pulmonary vascular resistance (PVR)

Right ventricular overload

Pulmonary Function Tests

The forced expiratory volume in the first second of expiration (FEV1) is substantially decreased during active bronchospasm

The forced vital capacity (FVC), expiratory reserve volume (ERV), inspiratory capacity, and forced expiratory flow FEF25 75% are also decreased whereas residual volume, functional residual capacity, and total lung capacity are increased

All these indices can return towards normal between bronchospastic attacks

The dynamic compliance of the lungs decreases because of air trapping, and accessory muscles (scalene and sternocleidomastoid) are recruited to preserve the tidal volume (Vt) despite increased ERV

Treatment

Bronchodilators

Short acting

2 agonists (albuterol)

Anti-cholinergics (ipratropuim)

Long acting

2 agonists (salmeterol, folmeterol)

Anti-cholinergics (thiotropuim)

Anti-inflammatory drugs

Beclomethasone and fluticasone

Others

Preoperative Management

A thorough history and physical examination provides the anesthesiologist with information that allows for appropriate identification of level of disease, degree of symptom control, and anesthetic risk stratification

Review of

Baseline exercise tolerance

Hospital visits secondary to asthma (including whether endotracheal intubation or IV infusions were required)

Allergies

Previous surgical/anesthetic history

The patients medication regimen should be reviewed This applies especially to steroid therapy: inhaled vs systemic use, duration of exposure, and side-effects should be elicited

Physical Exam

Physical examination should include vital signs and assessment of breath sounds

Use of accessory muscles, and level of hydration.

The presence of labored breathing, use of accessory muscles, and prolonged expiration time suggest poorly-controlled asthma.

Wheezing on auscultation is concerning, particularly if the wheezing is noticed in phases of the respiratory cycle other than end-expiration

Arterial blood gas may be useful in determining baseline oxygenation, carbon dioxide retention, and acid-base status.

A chest x-ray may be obtained to assess for lung hyperinflation and air-trapping

Intraoperative Management

The overriding goal in anesthetizing an asthmatic patient is to avoid bronchospasm and reduce the response to tracheal intubation

Severe bronchospasm may cause fatal or near-fatal events such as irreversible brain damage due to inability to ventilate

It is extremely important that the patient be at a deep level of anesthesia prior to instrumenting the airway, as tracheal intubation during light levels of anesthesia can precipitate bronchospasm

Regional anesthetic techniques should be considered when appropriate, to avoid airway instrumentation. The risk of pulmonary complications is lower when the surgical anesthetic was performed under epidural or spinal anesthesia

Intraoperative Management

Intravenous lidocaine has been successfully used to decrease airway irritability

Anti-muscarinics such as glycopyrrolate and atropine may decrease secretions and provide additional bronchodilation if given in sufficient time prior to induction

Propofol is the induction agent of choice in the hemodynamically stable patient due to its ability to attenuate the bronchospastic response to intubation

Intraoperative Management

Thiopental or etomidate may also be used as induction agents but lack the bronchodilating properties of propofol and in the case of thiopental, may lead to detrimental histamine release

Ketamine is an ideal induction agent for hemodynamically unstable asthmatics due to its ability to produce direct smooth muscle relaxation and bronchodilation without decreasing arterial pressure or systemic vascular resistance

However, ketamine-induced bronchodilation is not as pronounced as with propofol

Intraoperative Management

Volatile anesthetics are excellent choices for general anesthesia, as they depress airway reflexes and produce direct bronchial smooth muscle relaxation

Sevoflurane has the most pronounced bronchodilation effect

Desflurane increases airway resistance and should be avoided in asthmatics, specifically at lighter levels of general anesthesia.

Intraoperative Management

Warm, humidified gases should be provided at all times

The use of a laryngeal mask airway or even mask ventilation may be preferable to tracheal intubation in asthmatics

The benefits of an LMA must be balanced against the risks of an unsecured airway and in patients with severe GERD, obesity, diabetic gastroparesis, or recent oral intake, the need for a secured airway may take precedence

Intraoperative Management

If endotracheal intubation is deemed necessary, histamine-releasing neuromuscular blockers should be avoided

Vecuronium, rocuronium, and cis-atracurium are safe for use in asthmatics.

Succinylcholine, which releases low levels of histamine, has been used safely in asthmatics with little morbidity

Reversal of neuromuscular blockade with acetylcholinesterase inhibitors should be used with caution in asthmatics due to the risk of muscarinic side effects including bronchospasm

Sugammadex is an alternative medication for reversal of neuromuscular blockade

Sugammadex, a novel agent that encapsulates steroidal neuromuscular blocking agents without muscarinic side effects, has been proposed as an alternative medication for reversal of neuromuscular blockade

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Ventilatory Strategies

limiting peak inspiratory pressures and tidal volumes

lengthening the I:E ratio

Assist in avoiding air-trapping and auto PEEP

Patients should be kept adequately hydrated as usual, but fluid overload, pulmonary congestion, and edema can precipitate bronchospasm (cardiac asthma)

Intra-Operative Bronchospasm

Signs of intraoperative bronchospasm may include wheezing, a change in capnography (upslope on CO2 waveform, or decreased/absent CO2 waveform), decreased tidal volumes, or high peak inspiratory pressures

Investigate alternative diagnoses including

Ventilator malfunction

Endotracheal tube obstruction (e.g. kink, mucous plug, clot)

Endobronchial intubation

Medical conditions such as tension pneumothorax or pulmonary embolus

It can even be foreign body obstruction such as a dislodged tooth

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Intra-Operative Bronchospasm

Switch to 100% O2

Switch to Manual Bag Ventilation (to evaluate pulmonary and circuit compliance)

Deepening the plane of anesthesia by the administration of rapid-acting intravenous bronchodilators such a propofol or ketamine and by increasing the concentration of volatile anesthetic

Inhaled -2 agonists should be administered for further bronchodilation using a MDI

Intra-Operative Bronchospasm

Other bronchodilating strategies include administering anticholinergics, intravenous steroids, and intravenous or subcutaneous -agonists such as epinephrine

Theophylline may be added for refractory bronchospasm

ECMO is reserved for patients with severe bronchospasm refractory to maximal medical therapy.

Used successfully with good neurological outcomes to treat status asthmaticus in children

Steroids need time to act and epinephrine causes tachycardia

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Emergence

Bronchospasm, poor ventilation, and hypoxaemia are major hazards of the emergence phase

Suctioning of the airways must be rendered cautiously, if at all

Aspiration can trigger bronchospasm

Reversal of neuromuscular block has a number of hazards

Deep extubation (tracheal extubation while still deeply anaesthetized) has been practiced for many years, especially in children

Neostigmine increases bronchospasm risk because of its

muscarinic and pro-secretory effects.22 These can be

blunted by co-administration of atropine or glycopyrrolate,

but the duration of action of neostigmine can outlast that of

the vagolytic agent, especially in the presence of renal

insufficiency

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Postoperative Management

Dictated by the intraoperative course

If the surgery was uneventful, and pain, nausea, and respiratory status are well-controlled, asthmatics may safely be discharged

In the setting of significant intraoperative complications such as severe bronchospasm, special care must be taken

Post op ventilation

Readminister -agonists prior to emergence and throughout the postoperative recovery period as needed for recurrent bronchospasm

Maintaining a head of the bed up position

allowing time for further medical management, recovery of airway function, and metabolism of neuromuscular blockers without the need reversal agents

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Summary and Guidelines

The keys to an uncomplicated perioperative course are

Assiduous attention to detail in preoperative assessment,

Maintenance of the anti-inflammatory and bronchodilatory regimen through the perioperative period

Vigilant monitoring is needed for immediate recognition and calling for assistance

References

Perioperative considerations for the patient with asthma and bronchospasm B. D. Woods and R. N. Sladen*Department of Anesthesiology PH 527-B, College of Physicians and Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA

The Perioperative Management of Asthma Richard Applegate, Ryan Lauer*, John Lenart, Jason Gatling and Marisa Vadi Department of Anesthesiology, Loma Linda University School of Medicine, USA

Millers Basics of Anesthesia 6th Edition