RT Book, Section
A1 Corbridge, Thomas
A1 Hall, Jesse B.
A2 Hall, Jesse B.
A2 Schmidt, Gregory A.
A2 Wood, Lawrence D.H.
SR Print(0)
ID 2288599
T1 Chapter 40. Status Asthmaticus
T2 Principles of Critical Care, 3e
YR 2005
FD 2005
PB The McGraw-Hill Companies
PP New York, NY
SN 9780071416405
LK accesssurgery.mhmedical.com/content.aspx?aid=2288599
RD 2023/10/04
AB Severe  asthma  exacerbation  is  defined  by  several,  but  not  necessarily  all,  of  the  following  features:  dyspnea  at  rest,  upright  positioning,  inability  to  speak  in  phrases  or  sentences,  respiratory  rate  >30  breaths  per  minute  (bpm),  use  of  accessory  muscles  of  respiration,  pulse  >120  beats/min,  pulsus  paradoxus  >25  mm  Hg,  peak  expiratory  flow  rate  <50%  predicted  or  personal  best,  hypoxemia,  and  eucapnia  or  hypercapnia.Altered  mental  status,  paradoxical  respirations,  bradycardia,  a  quiet  chest,  and  absence  of  pulsus  paradoxus  from  respiratory  muscle  fatigue  identify  imminent  respiratory  arrest.Airway  wall  inflammation,  bronchospasm,  and  intraluminal  mucus  cause  progressive  airflow  obstruction.  Fewer  patients  develop  sudden-onset  asthma  from  a  more  pure  form  of  bronchospasm.Severe  exacerbations  and  death  can  occur  in  patients  with  mild  asthma.Airflow  obstruction  causes  ventilation-perfusion  inequality,  lung  hyperinflation,  and  increased  work  of  breathing.Oxygen,  β  agonists,  and  systemic  corticosteroids  are  first-line  treatments.  Agents  of  debated  efficacy  include  ipratropium  bromide,  magnesium  sulfate,  leukotriene  modifiers,  theophylline,  inhaled  steroids,  and  heliox.Noninvasive  ventilation  is  potentially  useful  in  hypercapneic  patients  not  requiring  intubation.Postintubation  hyperinflation  decreases  preload  to  the  right  ventricle  and  may  cause  barotrauma,  hypotension,  or  cardiac  arrest.  A  ventilator  strategy  that  lowers  lung  volume  decreases  complications.Treating  airflow  obstruction  and  prolonging  expiratory  time  decreases  lung  hyperinflation.  Expiratory  time  is  prolonged  on  the  ventilator  by  lowering  minute  ventilation  (even  at  the  cost  of  hypercapnia)  and  increasing  inspiratory  flow  rate.Deep  sedation  allows  for  safe  and  effective  mechanical  ventilation  in  most  intubated  patients.  Paralysis  increases  the  risk  of  myopathy.Patient  education,  environmental  control,  and  pharmacotherapy  are  crucial  to  prevent  exacerbations  and  death.