Perioperative Management Of Asthma In Cesarean Section

PERIOPERATIVE MANAGEMENT OF ASTHMA IN CESAREAN SECTION Houman Teymourian, M.D. Assistant professor, Department of Anesthesiology and Critical Care, Shahid Beheshti Medical University

ASTHMA   

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Asthma is a very common chronic disease 150 million people worldwide are affected The most common respiratory disease in women of childbearing age 4% of all pregnancies are complicated by asthma

DEFINITION & PATHOPHYSIOLOGY 

It is a chronic inflammatory disease of the airways involving multiple components of immune system (mast cells, eosinophils, neutrophils, T cell lymphocytes & cysteinyl leukotrienes)

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Is associated with : acute

bronchoconstriction , airway edema , mucus plug formation ,& airway wall remodeling 

Hyper reactivity ,Hypertrophy, Autonomic dysfunction, Inflammation secretion & edema

CLASSIFICATION 1. 2.

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Childhood-onset asthma (extrinsic) Adult-onset asthma (intrinsic) or traditionally: Mild , Moderate , Severe Women with severe asthma tends to have more pronounced exacerbations of disease during pregnancy

CLASSIFICATION OF ASTHMA SEVERITY 

STEP 1 (mild intermittent)

Symptoms: <2 times a week , brief exacerbations Nighttime symptoms: < 2 times a month Lung function: FEV1 >80% predicted 

STEP 2 (mild persistent)

Symptoms: >2 times a weak but<1 time a day, exacerbations affect activity Nighttime symptoms:> 2 times a month Lung function: FEV1 >80% predicted

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STEP 3 (moderate persistent)

Symptoms: daily , daily use of inhaled short acting β2 agonists, exacerbations affect activity and are >2 time a weak , may last days Nighttime symptoms: > 1 time a weak Lung function: FEV1 >60 -<80% predicted 

STEP 4 (severe persistent)

Symptoms: continuous , limited activity , frequent exacerbations Nighttime symptoms: frequent Lung function: FEV1 <60%

PHYSIOLOGIC CHANGES OF PREGNANCY   

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Cardiovascular: HR, SV , CO Respiratory: MV , VT ,FRC ,

,BP ,SVR , PVR

& RR remains unchanged, CO2 production but PaCO2 capillary engorgement of mucosa and edema of the oropharynx ,larynx ,and trachea

Hematologic: Blood volume 45%, red cell 30%

EFFECTS OF ASTHMA ON PREGNANCY 

The rate of prematurity ,pregnancy induced hypertension , perinatal mortality , low birth weight are increased (particularly in steroid dependents)

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Pre & post partum hemorrhage, preterm labor , premature rupture of membranes Neonatal tachycardia & transient tachypnea Increase in need to induce labor & the rate of cesarean section

MECHANISM 1.Disease process itself Interfering with increase of MV results in maternal co2 retention & hypoxemia.  CO2 retention shifts PH & decreases neonatal oxygenation  Maternal SPO2 less than 95% decreases neonatal oxygenation  Hyperventilation (alkalosis) decreases neonatal oxygenation Asthmatics are dehydrated and have increased intrathoracic pressure  Cardiac output decrease results in decrease in uterine blood flow

2.Treatment (steroids) 3.Other undefined causes (tobacco

TREATMENT OF ASTHMA Removal of triggers , monitoring ,patient education  STEP 1 (mild intermittent): Inhaled short acting β2-agonist ( e.g. albuterol )

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STEP 2 (mild persistent): step 1 +anti inflammatory (Inhaled steroid or cromolyn sodium) + possible use of sustained-release theophylline

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STEP 3 ( moderate persistent): long acting β2-agonist (e.g. salmeterol) + Inhaled steroid

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STEP 4 (severe persistent): all above + systemic steroid

TREATMENT OF ASTHMA DURING PREGNANCY 

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Poor treatment of asthma during pregnancy contribute significantly to adverse outcome The risk of untreated asthma far exceeds the risk of the medications Use of β2-agonists is safe. Use of oral corticosteroids is associated with pregnancy-induced hypertension & weakly with low-birth weight & cleft palate

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Anti cholinergics (Ipratropium) may be useful. During delivery , Inhaled β2-agonists + steroid + supplemental O2 should be used for any level of asthma Leukotriene modifiers are safe during pregnancy (zafirlukast ,montelukast) Zileuton is associated with IUGR, cleft palate, & long bone abnormalities

Status Asmathicus 

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Severe bronchospasm unresponsive to systemic steroids & β2-agonists that

requires mechanical ventilation & sedation & may be muscle relaxants & volatile anesthetics Use permissive hypercarbia , anticholinergics , heliox , methyl xantines

STATUS ASTHMATICUS IN PREGNANTS 

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In pregnants permissive hypercarbia cannot be achieved PPV may make the decrease in cardiac out put even more pronounced Position is important( aortocaval compression ) β2-agonists & theophylline can cause excessive tachycardia in mother & atrial arrhythmia in fetus Heliox : only if adequate oxygenation can be achieved with an FIO2 less than 0.4

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Magnesium sulfate particularly in pregnancy-induced hypertension and asthma There is some evidence that epidural anesthesia alone can be efficacious in termination of status asthmaticus in the parturient Early termination of pregnancy may be necessary to insure the survival of the mother and may result in immediate improvement in the respiratory status

Induction of labor 

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Prostaglandin F α provokes bronchospasm in induction of the labor Oxytocin has no adverse effect on asthma and is the agent of choice 2

ANESTHESIA FOR LABOR AND CESAREAN SECTION IN THE ASMATHIC PATIENT 

Basic principles: 1.

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Optimization of pulmonary status before anesthesia Avoidance of bronchospasm inducing agents (histamine releasers) Avoidance of airway irritation by an endotracheal tube whenever possible

Neuraxial Anesthesia For Cesarean Section 

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Epidural , Spinal , Combined spinalepidural Epidural anesthesia decreases catecholamine levels & O2 consumption , and may result in termination of the status asthmaticus Few cases of bronchospasm has been reported after spinal anesthesia Patients on steroid therapy may be at risk for infections

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No special considerations regarding choice of local anesthetics for this population Careful attention must be paid to avoidance of high block & respiratory failure Maintenance of Adequate intravascular volume is important If opioids are used either epidural or intrathecally the patient must be monitored carefully for respiratory

GENERAL ANESTHESIA 

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General anesthesia only if neuraxial anesthesia is contraindicated Risk of bronchospasm is high: 1. 2. 3.

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Tracheal intubation Rapid sequence induction Anesthetic level Insufficiency

Agents for induction: most commonly thiopental, ketamin , propofol

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Ketamin : has mild bronchodilatory action due to release of endogenous catecholamines Propofol: efficacious in blunting airway responces & has weak bronchodilatory action but hemodynamic changes must be managed appropriately and aggressively in parturient Thiopental: can cause histamine release, doses which is safe for fetus

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Lidocaine: is useful as an adjuvant to thiopental induction (1 mg/kg is enough to attenuate both airway and hemodynamic responses) , Aerosolized lidocaine is airway irritant and should not be used

MUSCLE RELAXANTS Succinylcholine can be used for initial relaxation  Rocuronium is a safe alternative in asthmatics  Atracurium & Rapacuronium can worsen bronchospasm & histamine release  Cisatracurium also is a choice 

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REVERSAL OF NEUROMUSCULAR BLOCKADE

Neostigmine can exacerbate airflow obstruction by increasing secretions and bronchospasm Edrophonium is a better choice in asthmatic patients Use of atropine or glycopyrrolate can attenuate these effects Succinylcholine infusion may be used to avoid using reversal agents

Maintenance of anesthesia 

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Halogenated agents have bronchodialating properties : halothane, isoflurane , sevoflurane Disadvantage: using high alveolar concentration (>1 – 1.5 MAC) for control of bronchospasm increase bleeding from uterine relaxation Halothane disadvantage : cardiac irritability particularly in high catecholamine state and

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Extubation take place when the patient is fully awake & airway obstruction controlled Patient should be treated during surgery with Steroids & β2-agonist Lidocaine infusion decreases airway reactivity during emergence Post operative Mechanical ventilation may be necessary to control obstruction

Postpartum Hemorrhage 

Is Increased in asthmatics due to: 

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Abnormalities in smooth muscles and neural regulation of contraction Peripartum use of β2-agonists

Use of Oxytocin is valid in asthmatics Use of Ergot alkaloid e.g. methylegonovine ( methergine) & ergonovine (ergotrate) is relatively

Postpartum Hemorrhage 

Prostaglandins used for uterine atony : 

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E causes bronchodilatation (only vaginal gel is available) F2α causes bronchoconstriction

Severe bronchospasm might be preferable to cardiovascular collapse

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HYPERTENSION PREECLAMPSIA AND ASTHMA Aspirin, NSAIDS & all beta blockers(

specially non β1 selective) can cause bronchospasm Hydralazine, TNG , Sodium nitroprusside ,and calcium channel blockers can be used, but they may cause hypoxemia by interfering with HPV Volume expansion is critical in both asthma & hypertension Magnesium sulfate has benefit in seizure prophylaxis and treatment of bronchospasm Neuraxial anesthesia is the preferred option unless there are clear