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मंगलवार, 13 सितंबर 2011

MANAGEMENT OF ASTHMA IN PREGNANCY


 INTRODUCTION :     
       Asthma is defined as a chronic inflammatory disease of the airway that is manifested by hyper responsiveness of airway to a wide variety of stimuli. It tends to be an episodic disease with exacerbations of reversible airway narrowing that are characterized clinically by coughing, wheezing and shortness of breath.
       Asthma is probably the most common and potentially life threatening disorder to occur in pregnancy. The worldwide incidence is about 1 to 4%. It complicates in 0.5 to 1.5% of pregnancies and status asthmaticus complicates in 0.2%. In 20% the condition improves, in 30% cases it deteriorates and in 50% cases it remains unchanged.
       In pregnancy, bronchodialator action is due to progesterone and cortisol and bronchoconstrictor action is due to reduced residual volume and increased PGF2 α.

 EFFECTS OF PREGNANCY ON ASTHMA :
        There is no evidence that pregnancy has predictable effect on underlying asthma. 1/3rd of asthmatic women can expect worsening of disease at sometime during pregnancy.  There is 18% increase in exacerbation of asthma following caesarian delivery compared with vaginal delivery.

EFFECTS OF ASTHMA ON PREGNANCY :
       When severe asthma can affect pregnancy outcome . It may lead to abortions preterm labour, LBW, neonatal hypoxia etc.
       There is a significant correlation between maternal pulmonary function and  foetal birth weight. 
       Uncontrolled asthma has maternal risks and  maternal deaths may be associated with status asthmaticus.
       It may lead to life threatening complications like- pnuemothorax, pneumomediastenum, acute cor pulmonale, cardiac arrhythmias and  muscle fatigue with respiratory arrest.


PATHOPHYSIOLOGY :
Allergens, respiratory infections, environmental pollutants, occupational exposure, cold air, emotional stress, strenuous exercise, aspirin and β blockers can precipitate asthma.
                                                                           Acted by primary mediators like histamines
                                                                           and  secondary mediators like PGs,
                                                                           thromboxanes and leukotrienes.


Mucus hypersecretion and mucosal edema

CLINICAL  COURSE :
Clinically,
It may range from
Mild wheezing             ___                                        severe bronchospasm
                                                                                        |           
Respiratory failure
 |
Severe hypoxaemia
 |
          DEATH




Functionally
                 Acute broncospasm( airway obstruction and reduced airflow)
                                                       |
                                           Increased breathing
                                                       |
                           Chest tightness/ wheezing/ breathlessness
                                                    |
                                           Altered oxygenation
                                                      |
                Ventilation perfusion mismatching and airway narrowing




CLINICAL STAGES OF ASTHMA

       Stage
         PO2
       PCO2
         pH
     FEV1
Mild respiratory alkalosis
      Normal
65 – 80

Respiratory alkalosis
50 – 64

Danger  zone

      normal
      Normal
35 – 49

Respiratory acidosis
<35




FEV – forced expiratory volume in 1 second

 



FOETAL EFFECTS :

Maternal alkalosis leads to fetal hypoxaemia well before maternal oxygenation is compromised.
Thus the fetus may be seriously compromised before maternal distress is severe.
This underscores the need for aggressive management of all pregnant women with acute asthma.
Therefore fetal response in effect becomes an indicator of maternal compromise .




CLINICAL EVALUATION :
 Signs :-
1) 1   Labored breathing
2)  2  Tachycardia
3)   3 Pulsus  paradoxus
4) 4   Prolonged expiration and use of accessory muscles of respiration

Fatal signs:-
1)   1 Central cyanosis
2)    2 Altered consciousness

Investigations:-
1)    1 ABG  analysis
2)   2  PEFR < 60% of baseline
3)   3  FEV1 < 20% suggestive of severe distress
4) 4    PO2 < 70 mm of Hg at sea level
5) 5   PCO2 > 35 mm of Hg at sea level
6)  6   PCO2 > 40 mm of Hg in pregnancy is suggestive of respiratory failure.
7)   7  pH < 7.35 (indication of hyperventilation and CO2 retention)
P     


Preconceptional
P
p    possibility of child becoming asthmatic is 4%
If    If 1 parent is asthmatic, the possibility is 8 to 10%
If     both parents are asthmatic, the possibility is 30%



A  Pregnancy
A  A STEP WISE PLAN is recognized by the
U.U. S. National Asthma Education And Prevention Programme       &
     British  Thoracic  Society.
A     As told earlier, patient education is of utmost importance.
1)    1.Patient must measure PEFR  twice daily.
2)    2.Use of proper inhaler
3)  3.  Patient is given a written management plan
4) 4.   Use of impermeable pillows
5)   5. Avoid pets at home
6) 6.   No carpets in bedrooms
7) 7.   Avoid cigarette smoke
If   If PEFR reduces by 20% then step up the therapy and patient must see a physician
If    If  PFER reduces by 50% its an emergency and needs hospitalization.

    TREATMENT OF ASTHMA HAS TWO MAJOR GROUPS
  
           RESCUE AGENTS                                                 MAINTENANCE AGENTS
     Relieve bronchospasm                                          treat airway inflammation                                              
      Eg: β2 agonists                                                      Eg: steroids, mast cell stabilizers,
and  ipratropium                                                     methyl xanthenes, leukotriene  


                    STEP WISE THERAPY :-
   
     Category
             Criteria
                    Step therapy
Mild intermittent
PEFR>80%
Variability<20%
-symptoms occur twice a week
-at night twice a month
-exacerbations last for hours to a few days
-asymptomatic in between two episodes
-no daily treatment required
-inhalation of β2 adrenergic agonists as needed
Mild persistant
PEFR >80%
Variability 20-30%
-symptoms occur more than twice a week
-night symptoms more than twice a month
-exacerbations may affect daily activity
- inhalation of β2 adrenergic agonists as needed
-and daily treatment with inhaled chromolyn or nedochromil or low dose corticosteroids or theophylline
Moderate persistant
PEFR 60-80%
Variability >30%
-symptoms occur daily
-night symptoms > once a week

-inhalation of β2 adrenergic agonists as needed
-and daily treatment with low to medium dose corticosteroids
-and daily treatment with salmeterol/theophylline preparation
Severe persistant
PEFR <60%
Variability >30%
-continual symptoms that limit activity
-frequent night symptoms an d actual exacerbations
-inhalation of β2 adrenergic agonists as needed
-and daily treatment with high dose corticosteroids
-and daily treatment with salmeterol/theophylline preparation
-and daily or alternate day treatment with systemic prednisolone
                                                                      






If plan fails treatment with prednisolone orally for 5 to 10 days.


Intra partum :-
During labour ,exacerbation is rare because of natural outpouring of endogenous steroids and epinephrine associated with stress of delivery.
1)         1;Clinical evaluation of the patient in labour may be inaccurate to predict the severity.
2)          2:Stress dose corticosteroids must be given during labour if the patient had steroids within the previous 4 weeks . HYDROCORTISONE 100mg I.V. 8 hrly.
3)         3:Opoid analgesics must be avoided as they cause bronchconstriction and respiratory depression. FENTANYL is preferred as it is non histaminic releasing narcotic over meperidine and morphine.
4)        4: SYNTOCINON is preferred over ergometrine, because the latter causes bronchoconstriction.
5)   5: PGF2α should not be used as it precipitates bronchospasm.
6)  6:  PGE1 and PGE2 can be used locally for induction of labour or abortion.
7)  7:  EPIDURAL ANAESTHESIA is preferable to G.A. because of risk of atelectasis and chest infection by latter.
8) 8:   If G.A. is given then bronchodialators like HALOTHANE and KETAMINE should be used.
9)    9:ABG analysis may be needed to assess oxygenation, ventilation and acid-base status.(PCO2 > 35mmHg and pH>7.35 indicates CO2 retension)
      10)  THEOPHYLLINE is used as an adjunct for nocturnal asthma.



Post natal :-       
1)    1:Post natal physiotherapy
2) 2:   Encourage breast feeding
3)  3:  Restart maintenance drug therapy
4)  4:  Encourage respiratory therapy to prevent atelectasis
5)    5:BARRIER CONTRACEPTIVES must be encouraged
6)    6:Advice VASECTOMY for terminal measures




Dr. Arpita Masalia
M.S. RESIDENT(GYNAEC)
P.G. SCHOLAR

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