Status asthamaticus

    Status asthamaticus severe prolonged asthma attack which will not respond to standard treatment with bronchiodialaters.Asthma is a obstructive lung disease,the airways are hyper-reactive. possible triggers of hyper reactive response include allergens,cold air and excercise. hyper reactivity refers to the fact that the airways are more likely to constrict in response to these stimuli.status asthmaticus are two types .One is gradual onset and sudden onset.80% of the asthma attacksare having gradual onset that associated with esionophilic infiltration.sudden onset asthma attacks aredue to exposure to significant allergens.this is due to neutrophilic inflamattion and usually occursat  night.

Clincal feautures

1. Progressive shortness of breath develop over days or hours
2. Accessory muscle recruitment 
3. Wheezing 
4. Prolonged expiatory phase
5. Increased respiratory rate
6. Cyanosis
7. Diffcult in speaking 
8. Shortness of breath and anxiety causes tachycardia and hypertension.may be worsens by the use of beta 2 agonist which is bronchiodialtor
9. Bronchospasam

Causes 

1. Asthma is a disease that can be inherited or it can triggred by environmental factors.allergens that trigger bronchospasm varies one person to another.triggers include pollen,pets ,mold and dust mites.
2. Upper respiratory tract infections
3. Tobacco smoking
4. Exercise
5. Inhalation of cold or dry air
6. Gerd
7. Drugs such as beta blockers,asprin and non-steriodal anti inflamattory drugs

Investigations

1. Pulmonary function test reveals signs of obstructive airway,disease ,low- normal or decreased vital capacity and increased total lung and residual capacity.
2. Serum immunoglobin IgE levels may increase form an allergic reaction
3. Complete blood count with differential reveals increased eosinophil count
4. Chest xray can diagnose or monitor asthma progress and may show hyperinflation with areas of atelectasis.
5. ABG analysis detect hypoxemia and guide treatment
6. Pulse oximetry may show reduced Sao2 level

Management

1. The best treatment for asthma is prevention by identifying and avoid preciptating factors.usually complete removal of stimuli is impossible,so desensitization to specific antigen may be helpful
2. Long acting bronchodialaters such as salmeterol/formoterol) decrease bronchoconstriction,reduce bronchial airway odema,and increase pulmonary ventilation.
3. Corticosteriods(hydrocortisone/methylpredisolone) have the same effect as bronchodialtersas well as anti-inflamattory and immunosuppressive effects.inhaled corticosteriods are used in long term control of asthma
4. Leukotirene modifiers(montelukest,zafirlukas) are effective in reducing mucous formation and airway constrictions
5. Mast cell stabilizers such as cromolyn and nedocromil) when given prophylacticaly ,block the acute obstructive effects of antigen exposure.

Oxygen

    Low flow humidified oxygen is needed to treat dyspnea,cyanosis and hypoxemia,the amount deleiverdis designed to maintain a partial pressure of arterial oxygen between 65and 85 mm Hg,as determined by ABGs studies.

   Mechanical ventilation is necessary if the patient does not respond to intial ventilatory support and drugs or develops respiratory failure

References

1. Han P, Cole RP. Evolving differences in the presentation of severe asthma requiring intensive care unit admission. Respiration. Sep-Oct 2004;71(5):458-62. [Medline].
2. Vaschetto R, Bellotti E, Turucz E, Gregoretti C, Corte FD, Navalesi P. Inhalational anesthetics in acute severe asthma. Curr Drug Targets. Sep 2009;10(9):826-32. .
3. Hanania NA, David-Wang A, Kesten S, Chapman KR. Factors associated with emergency department dependence of patients with asthma. Chest. Feb 1997;111(2):290-5. 
4. Vital Signs: Asthma Prevalence, Disease Characteristics, and Self-Management Education --- United States, 2001—2009. CDC MMWR. Available athttp://www.cdc.gov/mmwr/preview/mmwrhtml/mm6017a4.htm?s_cid=mm6017a4_w. Accessed August 20, 2014.
5. National Heart, Lung, and Blood Institute. Managing exacerbations of asthma. In: National Asthma Education and Prevention Program (NAEPP). Expert panel report 3: guidelines for the diagnosis and management of asthma. National Guideline Clearinghouse; 
6. Saadeh CK, Goldman MD, Gaylor PB. Forced oscillation using impulse oscillometry (IOS) detects false negative spirometry in symptomatic patients with reactive airways. J Allergy Clin Immunol. 2003;111:S136.
7. Schultz TE. Sevoflurane administration in status asthmaticus: a case report. AANA J. Feb 2005;73(1):35-6.