ASTHMA. What is Asthma A Chronic disease of the airways that may cause:A Chronic disease of the...

ASTHMAASTHMA

What is AsthmaWhat is Asthma

• A Chronic disease of the airways A Chronic disease of the airways that may cause:that may cause:• WheezingWheezing• BreathlessnessBreathlessness• Chest tightnessChest tightness• Nighttime or early morning coughingNighttime or early morning coughing

The bronchospasm characteristic The bronchospasm characteristic of the acute asthmatic attack is of the acute asthmatic attack is typically reversible. It improves typically reversible. It improves spontaneously or within minutes to spontaneously or within minutes to hours of treatmenthours of treatment

• Asthma can exist by itself or Asthma can exist by itself or coexist with chronic bronchitis, coexist with chronic bronchitis, emphysema, or bronchiectasisemphysema, or bronchiectasis

Symptoms/Chief Symptoms/Chief ComplaintComplaint

• Progressive dyspneaProgressive dyspnea• CoughCough• Chest tightnessChest tightness• Wheezing/coughingWheezing/coughing

• The rapidly reversible airflow The rapidly reversible airflow obstruction of asthma is mainly obstruction of asthma is mainly due to bronchial smooth muscle due to bronchial smooth muscle contractioncontraction

Focus of TherapyFocus of Therapy

• Pharmacologic manipulation of airway smooth Pharmacologic manipulation of airway smooth musclemuscle

• Do not overlook physiologic impairment caused Do not overlook physiologic impairment caused by mucous production and mucosal edemaby mucous production and mucosal edema

• Bronchospasm can be reversed in minutesBronchospasm can be reversed in minutes• Airflow obstruction due to mucous plugging and Airflow obstruction due to mucous plugging and

inflammatory changes in bronchial walls may not inflammatory changes in bronchial walls may not resolve for days/weeks - resolve for days/weeks - • may lead to atelectasis, infectious bronchitis, may lead to atelectasis, infectious bronchitis,

pneumonitispneumonitis

Asthma TriggersAsthma Triggers• Immunologic reactionImmunologic reaction• Viral respiratory/sinus infectionsViral respiratory/sinus infections• change in temperature/humiditychange in temperature/humidity• Drugs/Chemicals - Drugs/Chemicals -

• aspirin, NSAIDSaspirin, NSAIDS

• ExerciseExercise• GE refluxGE reflux• Laughing/coughingLaughing/coughing• Environmental factors -Environmental factors -

• strong odors, pollutants, dust, fumesstrong odors, pollutants, dust, fumes

Patient ExamPatient Exam

• Wheezing Wheezing • may be audible w/o stethoscopemay be audible w/o stethoscope

• Use of accessory muscles of inspirationUse of accessory muscles of inspiration• diaphragmatic fatiguediaphragmatic fatigue• Paradoxical respirationsParadoxical respirations

• - reflect impending ventilatory failure- reflect impending ventilatory failure

• Altered mental status -Altered mental status -• lethargy, exhaustion, agitation, confusionlethargy, exhaustion, agitation, confusion


• Hyperrsonance to percussionHyperrsonance to percussion• decreased intensity of breath decreased intensity of breath

soundssounds• prolongation of expiratory phase w prolongation of expiratory phase w

or w/o wheezingor w/o wheezing


• The intensity of the wheeze may The intensity of the wheeze may not correlate with the severity of not correlate with the severity of airflow obstructionairflow obstruction

• ““quiet chest” - very severe airflow quiet chest” - very severe airflow obstructionobstruction

Risk factors for death from Risk factors for death from asthmaasthma

• Past history of sudden severe Past history of sudden severe exacerbations exacerbations

• Prior intubation for asthma Prior intubation for asthma • Prior admission for asthma to an Prior admission for asthma to an

intensive care unit intensive care unit • Two or more hospitalizations for asthma Two or more hospitalizations for asthma

in the past year in the past year • Three or more emergency care visits for Three or more emergency care visits for

asthma in the past year asthma in the past year • Hospitalization or emergency care visit Hospitalization or emergency care visit

for asthma within the past month for asthma within the past month

Risk factorsRisk factors cont.. cont..

• Use of more than two canisters per month of inhaled Use of more than two canisters per month of inhaled short-acting 2-agonistshort-acting 2-agonist

• Current use of systemic corticosteroids or recent Current use of systemic corticosteroids or recent withdrawal from systemic corticosteroids withdrawal from systemic corticosteroids

• Difficulty perceiving airflow obstruction or its Difficulty perceiving airflow obstruction or its severity severity

• Comorbidity, as from cardiovascular diseases or Comorbidity, as from cardiovascular diseases or chronic obstructive pulmonary disease chronic obstructive pulmonary disease

• Serious psychiatric illness or psychosocial problems Serious psychiatric illness or psychosocial problems • Low socioeconomic status in urban residents Low socioeconomic status in urban residents • Illicit drug useIllicit drug use

Asthma TreatmentAsthma Treatment

• Nebulized B-adrenergic drugsNebulized B-adrenergic drugs• CorticosteroidsCorticosteroids• Nebulized anticholinergicsNebulized anticholinergics• Magnesium sulfateMagnesium sulfate• OxygenOxygen• Long acting beta-agonistsLong acting beta-agonists• Inhaled steroidsInhaled steroids

Managing Asthma: Managing Asthma:

• Indications of a severe attack:Indications of a severe attack:• Breathless at restBreathless at rest• hunched forwardhunched forward• talking in words rather than talking in words rather than

sentencessentences• AgitatedAgitated• Peak flow rate less than 60% of Peak flow rate less than 60% of

normalnormal

Treatment Goals of Severe Treatment Goals of Severe AsthmaAsthma

• Improve airway function rapidlyImprove airway function rapidly• Avoid hypoxemiaAvoid hypoxemia• Prevent respiratory failure and Prevent respiratory failure and

deathdeath

Classifying Severity of Asthma Exacerbations

Mild Moderate SevereMild Moderate Severe

walking walking talking talking at rest at rest Can lie down Can lie down Prefers sittingPrefers sitting upright upright

Sentences Sentences PhrasesPhrases Words Words

May be agitated Usually agitatedMay be agitated Usually agitated

• SymptomsSymptoms

• Breathlessness

• Position

• Talks in

• Alertness


Signs Mild Moderate SevereMild Moderate Severe


Functional assessmentFunctional assessment Mild Moderate SevereMild Moderate Severe


80% 50–80% <50% or 80% 50–80% <50% or response response lasts<2h lasts<2h

Normal >60 mm Hg <60 mm Hg: Normal >60 mm Hg <60 mm Hg:

possible possible cyanosis cyanosis

<42 mm Hg <42 mm Hg > 42 mm Hg: <42 mm Hg <42 mm Hg > 42 mm Hg: possible respiratory possible respiratory failure failure

>95 %91–95% <91%>95 %91–95% <91%

Peak expiratory flow Peak expiratory flow % predicted or % predicted or

% personal best% personal best

PaO2 (on air)PaO2 (on air)

PaCO2 PaCO2

SaO2% SaO2% (on air) at sea level(on air) at sea level

Functional assessmentFunctional assessment Mild Moderate SevereMild Moderate Severe

Respiratory Arrest Respiratory Arrest ImminentImminent

• Drowsy or confusedDrowsy or confused• Paradoxical thoracoabdominal Paradoxical thoracoabdominal

movementmovement• Absent WheezeAbsent Wheeze• BradycardiaBradycardia• Absence Pulsus paradoxus suggests Absence Pulsus paradoxus suggests

respiratory muscle fatigue respiratory muscle fatigue

Asthma MimickersAsthma Mimickers

• Congestive heart failure ("cardiac asthma")Congestive heart failure ("cardiac asthma")• Upper airway obstructionUpper airway obstruction• Aspiration of foreign body or gastric acidAspiration of foreign body or gastric acid• Bronchogenic carcinoma with endobronchial Bronchogenic carcinoma with endobronchial

obstructionobstruction• Metastatic carcinoma with lymphangitic Metastatic carcinoma with lymphangitic

metastasismetastasis• Sarcoidosis with endobronchial obstructionSarcoidosis with endobronchial obstruction• Vocal cord dysfunctionVocal cord dysfunction• Multiple pulmonary emboli (rare)Multiple pulmonary emboli (rare)

treatment of acute asthmatreatment of acute asthma

Goal in the EDGoal in the ED• reverse airflow obstruction rapidly reverse airflow obstruction rapidly

by repetitive or continuous by repetitive or continuous administration of inhaled 2-agonistsadministration of inhaled 2-agonists

• ensure adequate oxygenationensure adequate oxygenation

• relieve inflammation relieve inflammation

Initial Assessment

• History• physical examination

(auscultation use of accessory muscles, heart rate, respiratory rate)

• PEFR or FEV• oxygen saturation• other tests as indicated

Diagnosis Diagnosis

• Bedside spirometry Bedside spirometry • rapid, objective assessment ,guide to rapid, objective assessment ,guide to

the effectiveness of therapy.the effectiveness of therapy.• The forced expiratory volume in 1 s The forced expiratory volume in 1 s

(FEV1)(FEV1)• peak expiratory flow rate (PEFR)peak expiratory flow rate (PEFR)

• Sequential measurementsSequential measurements• management decisionsmanagement decisions

Pulse oximetryPulse oximetry

• assessing oxygenation and assessing oxygenation and monitoring oxygen saturation monitoring oxygen saturation during treatment.during treatment.

• ABG is not indicated in most ABG is not indicated in most patients with mild to moderate patients with mild to moderate asthma exacerbationasthma exacerbation

ABGABG

assess for assess for hypoventilation hypoventilation with with carbon dioxide carbon dioxide retentionretention and and respiratory acidosisrespiratory acidosis

• clinical evidence of severe attacks clinical evidence of severe attacks • PEFR or FEV1 of less than 25 percent predictedPEFR or FEV1 of less than 25 percent predicted• With acute attacks, ventilation is stimulated, With acute attacks, ventilation is stimulated,

resulting in a decrease in partial pressure of resulting in a decrease in partial pressure of carbon dioxide (PaCO2)carbon dioxide (PaCO2)• normal or slightly elevated PaCO2 (e.g., 42 mm Hg) normal or slightly elevated PaCO2 (e.g., 42 mm Hg)

indicates extreme airway obstruction and fatigue and indicates extreme airway obstruction and fatigue and may herald the onset of acute ventilatory failuremay herald the onset of acute ventilatory failure

radiographyradiography

• clinical indication of a complication clinical indication of a complication • pneumothorax, pneumomediastinum, pneumothorax, pneumomediastinum,

pneumonia, or other medical concernpneumonia, or other medical concern

• one-third of asthma exacerbations one-third of asthma exacerbations requiring admission, will requiring admission, will demonstrate an abnormality on demonstrate an abnormality on chest radiograph chest radiograph

CBCCBC

• not indicatednot indicated • modest leukocytosis secondary to modest leukocytosis secondary to

administration of B -agonist therapy administration of B -agonist therapy or corticosteroid treatmentor corticosteroid treatment

• In patients taking theophylline before In patients taking theophylline before ED presentation, a serum ED presentation, a serum theophylline level theophylline level

ECGECG

• Routine electrocardiogram is Routine electrocardiogram is unnecessary unnecessary

right ventricular strain, abnormal P waves, right ventricular strain, abnormal P waves, or nonspecific ST- and T-wave or nonspecific ST- and T-wave abnormalities, which resolve with abnormalities, which resolve with treatmenttreatment

Older patients, especially those with Older patients, especially those with coexisting heart disease, should have coexisting heart disease, should have cardiac monitoring during treatmentcardiac monitoring during treatment

Impending or Actual Respiratory

Arrest

• Intubation and mechanical ventilation with 100% 02

• Nebulized B2 agonist and anticholinergic

• Intravenous steroid

• Admit to ICU

FEV1 or PEFR <50% (Severe Exacerbation)

Repeat Assessment

• Symptoms. • physical examination. • PEFR. • 02 saturation. • other test as needed

Severe Exacerbation

Moderate Exacerbation

Good Response

Discharge Home

Poor Response

Incomplete Response

Poor Response

medications medications are used in the are used in the treatment of acute asthmatreatment of acute asthma

• adrenergic agonistsadrenergic agonists• anticholinergicsanticholinergics • glucocorticoidsglucocorticoids• Magnesium, helioxMagnesium, heliox (mixture of helium (mixture of helium

and oxygen), and and oxygen), and ketamineketamine may be may be considered when the aforementioned considered when the aforementioned medications fail to relieve bronchospasm. medications fail to relieve bronchospasm.

• Mast cell-stabilizingMast cell-stabilizing agents, agents, methylxanthinesmethylxanthines, and , and leukotrieneleukotriene modifiers are currently reserved for modifiers are currently reserved for maintenance therapy only maintenance therapy only

Adrenergic Agents Adrenergic Agents

• Adrenergic receptors Adrenergic receptors

• Stimulation of Stimulation of B B 1-receptors increases 1-receptors increases rate and force of cardiac contraction and rate and force of cardiac contraction and decreases small intestine motility and decreases small intestine motility and tonetone

• B2B2-adrenergic stimulation promotes -adrenergic stimulation promotes bronchodilation, vasodilation, uterine bronchodilation, vasodilation, uterine relaxation, and skeletal muscle tremor relaxation, and skeletal muscle tremor

Adrenergic AgentsAdrenergic Agents

• stimulation of the enzyme adenyl cyclase, which stimulation of the enzyme adenyl cyclase, which converts intracellular converts intracellular adenosine triphosphateadenosine triphosphate into into cyclic adenosine monophosphatecyclic adenosine monophosphate

• enhances the binding of intracellular calcium to enhances the binding of intracellular calcium to cell membranes, reducing the myoplasmic cell membranes, reducing the myoplasmic calcium concentration, and results in relaxation calcium concentration, and results in relaxation of bronchial smooth muscleof bronchial smooth muscle

• inhibit mediator release and promote inhibit mediator release and promote mucociliary clearance. mucociliary clearance.

side effectside effect of B-adrenergic of B-adrenergic drugsdrugs

• skeletal muscle tremor (most common)skeletal muscle tremor (most common)• nervousness, anxiety, nervousness, anxiety, • insomnia, headache, insomnia, headache, • hyperglycemia,hyperglycemia,• palpitations, tachycardia, and hypertensionpalpitations, tachycardia, and hypertension• potential cardiotoxicity(combination with potential cardiotoxicity(combination with

theophylline not significant problems)theophylline not significant problems)• Arrhythmias and evidence of myocardial Arrhythmias and evidence of myocardial

ischemia( rare)ischemia( rare)

Inhaled short-acting B-2 Inhaled short-acting B-2 agonistsagonists

Albuterol Albuterol • Nebulizer solution (5 mg/mL)Nebulizer solution (5 mg/mL)

• 2.5–5.0 mg every 20 min for 3 doses2.5–5.0 mg every 20 min for 3 doses• then 2.5–10 mg every 1–4 h as needed then 2.5–10 mg every 1–4 h as needed or or 10–15 10–15

mg per h continuouslymg per h continuously

• Only selective B-2 agonists are Only selective B-2 agonists are recommendedrecommended• for optimal delivery, dilute aerosols to minimum for optimal delivery, dilute aerosols to minimum

of 4 mL at gas flow of 6–8 L per minof 4 mL at gas flow of 6–8 L per min

AlbuterolAlbuterol

• MDI (90 g/puff)MDI (90 g/puff)

• 4–8 puffs every 20 min up to 4 h4–8 puffs every 20 min up to 4 h

• then every 1–4 h as needed then every 1–4 h as needed

• As effective as nebulized therapy if patient As effective as nebulized therapy if patient is able to coordinate inhalation maneuver; is able to coordinate inhalation maneuver; use spacer/holding chamberuse spacer/holding chamber


• Bitolterol Bitolterol • Nebulizer solution (2 mg/mL) Nebulizer solution (2 mg/mL) • MDI (370 macg/puff) MDI (370 macg/puff)

• Pirbuterol Pirbuterol • MDI (200 g/puff) MDI (200 g/puff)


• Systemic (injected), B-2 agonistsSystemic (injected), B-2 agonists

• Epinephrine Epinephrine (1:1000 or 1 mg/mL)(1:1000 or 1 mg/mL)• 0.3–0.5 mg SC every 20 min for 3 doses0.3–0.5 mg SC every 20 min for 3 doses

• TerbutalineTerbutaline (1 mg/mL) (1 mg/mL)• 0.25 mg SC every 20 min for 3 doses0.25 mg SC every 20 min for 3 doses

No proven advantage of systemic No proven advantage of systemic therapy over aerosoltherapy over aerosol

Anticholinergics Anticholinergics

• potent bronchodilatorspotent bronchodilators in patients with asthma and in patients with asthma and other forms of obstructive lung disease other forms of obstructive lung disease

• anticholinergics affect anticholinergics affect large, central airwayslarge, central airways, , • whereas whereas B-adrenergic drugs dilate smaller airwaysB-adrenergic drugs dilate smaller airways • competitively antagonize acetylcholine at the competitively antagonize acetylcholine at the

postganglionic junction between the parasympathetic postganglionic junction between the parasympathetic nerve terminal and effector cellnerve terminal and effector cell

• blocks the bronchoconstriction induced by vagal blocks the bronchoconstriction induced by vagal cholinergic-mediated innervation to the larger central cholinergic-mediated innervation to the larger central airwaysairways

• concentrations of cyclic guanosine monophosphate in concentrations of cyclic guanosine monophosphate in airway smooth muscle are reduced,further promotin airway smooth muscle are reduced,further promotin bronchodilation bronchodilation

AnticholinergicsAnticholinergics

Ipratropium bromideIpratropium bromide • Nebulizer solution (0.2 mg/mL)Nebulizer solution (0.2 mg/mL)

• 0.5 mg every 30 min for 3 doses0.5 mg every 30 min for 3 doses• then every 2–4 h as needed then every 2–4 h as needed

• Should not be used as first-line therapy;Should not be used as first-line therapy;• should be added to 2 agonist therapy; should be added to 2 agonist therapy; • may mix in same nebulizer with albuterolmay mix in same nebulizer with albuterol

• MDI (18 g/puff)MDI (18 g/puff)• 4–8 puffs every 6–8 h4–8 puffs every 6–8 h

side effectsside effects

• dry mouthdry mouth• ThirstThirst• difficulty swallowingdifficulty swallowing• Less commonlyLess commonly

• tachycardia, restlessness, irritability, tachycardia, restlessness, irritability, confusion, difficulty in micturition, confusion, difficulty in micturition, ileus, blurring of vision, or an increase ileus, blurring of vision, or an increase in intraocular pressure in intraocular pressure

CorticosteroidsCorticosteroids

• highly effective drugs in asthma highly effective drugs in asthma exacerbationexacerbation

• one of the cornerstones of treatmentone of the cornerstones of treatment• mechanism of action is unknownmechanism of action is unknown

• Restoring B-adrenergic responsiveness Restoring B-adrenergic responsiveness • reducing inflammationreducing inflammation

• The onset of anti-inflammatory The onset of anti-inflammatory effect effect is delayedis delayed at least 4 to 8 h after at least 4 to 8 h after intravenous or oral administration.intravenous or oral administration.


• administered within 1 h of arrival in the EDadministered within 1 h of arrival in the ED• reduces the need for hospitalizationreduces the need for hospitalization• prednisone 40 to 60 mg, oralprednisone 40 to 60 mg, oral• methylprednisolone 60 to 125 mg IV methylprednisolone 60 to 125 mg IV

• High-doseHigh-dose corticosteroid therapy offers no corticosteroid therapy offers no advantageadvantage

• Additional doses should be given every 4 to 6 h Additional doses should be given every 4 to 6 h until significant subjective and objective until significant subjective and objective improvements are achievedimprovements are achieved

• discharging all patients with mild persistent or discharging all patients with mild persistent or more severe asthma on maintenance inhaled more severe asthma on maintenance inhaled corticosteroids in addition to a burst of oral corticosteroids in addition to a burst of oral corticosteroidcorticosteroid


• PrednisonePrednisone• Methylprednisolone Methylprednisolone • PrednisolonePrednisolone

• 120–180 mg per d in 3 or 4 divided doses for 120–180 mg per d in 3 or 4 divided doses for 48 h,48 h,

• then 60–80 mg per d until FEV1, or PEFR then 60–80 mg per d until FEV1, or PEFR reaches 70% of predicted or personal bestreaches 70% of predicted or personal best

• For outpatient "burst," use 40–60 mg per d, for For outpatient "burst," use 40–60 mg per d, for 3–10 d in adults3–10 d in adults

TheophyllineTheophylline

• no longer considered a first-line treatment no longer considered a first-line treatment • in combination with inhaled B 2-in combination with inhaled B 2-

adrenergic drugs,adrenergic drugs,• increase the toxicity, but not the efficacy, of increase the toxicity, but not the efficacy, of

treatmenttreatment

• more sustained bronchodilator effect, more sustained bronchodilator effect, improving respiratory muscle enduranceimproving respiratory muscle endurance

• improving resistance to fatigueimproving resistance to fatigue• anti-inflammatoryanti-inflammatory

TheophyllineTheophylline

side effects side effects • nervousness, nausea, vomiting, nervousness, nausea, vomiting,

anorexia, and headacheanorexia, and headache

• At plasma levels greater than 30 At plasma levels greater than 30 g/mL, there is a risk of seizures g/mL, there is a risk of seizures and cardiac arrhythmias. and cardiac arrhythmias.

magnesium sulfatemagnesium sulfate

• acute, very severe asthmaacute, very severe asthma (i.e., FEV1 <25 percent predicted)(i.e., FEV1 <25 percent predicted)

• The dose is 1 to 2 g IV over 30 The dose is 1 to 2 g IV over 30 min.min.

• Heliox, Ketamine, and HalothaneHeliox, Ketamine, and Halothane

• Mast Cell ModifiersMast Cell Modifiers

• Leukotriene Modifiers Leukotriene Modifiers

Mechanical VentilationMechanical Ventilation

• progressive hypercarbia and acidosis progressive hypercarbia and acidosis • ExhaustedExhausted• confused, confused,

• does not relieve the airflow obstruction does not relieve the airflow obstruction eliminates the work of breathing and eliminates the work of breathing and enables the patient to rest while the enables the patient to rest while the airflow obstruction is resolvedairflow obstruction is resolved

• Direct oral intubationDirect oral intubation

COPDCOPD

COPDCOPD

• Hallmark symptom - DyspneaHallmark symptom - Dyspnea• Chronic productive coughChronic productive cough• Minor hemoptysisMinor hemoptysis• pink puffer pink puffer • blue bloaterblue bloater

COPD- pulmonary hyperinflation- the diaphragms are at the level of the eleventh posterior ribs and appear flat.

COPD - Physical FindingsCOPD - Physical Findings

• TachypneaTachypnea• Accessory respiratory muscle useAccessory respiratory muscle use• Pursed lip exhalationPursed lip exhalation• Weight loss due to poor dietary Weight loss due to poor dietary

intake and excessive caloric intake and excessive caloric expenditure for work of breathingexpenditure for work of breathing

Dominant Clinical Forms of Dominant Clinical Forms of COPDCOPD

• Pulmonary emphysemaPulmonary emphysema• Chronic bronchitisChronic bronchitis

• Most patients exhibit a mixture of Most patients exhibit a mixture of symptoms and signssymptoms and signs

COPD - Advanced DxCOPD - Advanced Dx

• secondary polycythemiasecondary polycythemia• cyanosiscyanosis• tremortremor• somnolence and confusion due to somnolence and confusion due to

hypercarbia hypercarbia • Secondary pulmonary HTN w or Secondary pulmonary HTN w or

w/o cor pulmonalew/o cor pulmonale

COPD Treatment StrategyCOPD Treatment Strategy

• Elimination of extrinsic irritantsElimination of extrinsic irritants• bronchodilator & glucocorticoid bronchodilator & glucocorticoid

therapytherapy• AntibioticsAntibiotics• Mobilization of secretionsMobilization of secretions• ““respiratory vaccines”respiratory vaccines”• Oxygen therapy - if oxygen saturation Oxygen therapy - if oxygen saturation

<90% at rest on room air<90% at rest on room air

SpirometrySpirometry

A-a gradientA-a gradient

A-a gradient = A-a gradient = predicted pOpredicted pO2 2 – observed PO– observed PO22

PAOPAO22 = (FIO = (FIO22 X 713) – (PaCO X 713) – (PaCO22/0.8) at sealevel/0.8) at sealevel

PAOPAO22 = 150-(PaCO = 150-(PaCO22/0.8) at sealevel on room air/0.8) at sealevel on room air

Normal range 10-15mm > 30 years of ageNormal range 10-15mm > 30 years of ageNormal range 8mm < 30 years of ageNormal range 8mm < 30 years of ageIncreased A-aDOIncreased A-aDO22=diffusion defect=diffusion defectRight to left shunt Right to left shunt V/Q mismatchV/Q mismatch

ExamplesExamples

• A doubel overdose brings two 30 yr old A doubel overdose brings two 30 yr old patients to the ED. Both have ingested patients to the ED. Both have ingested substantial amounts of barbiturates and substantial amounts of barbiturates and diazepam. Blood gases drawn on room diazepam. Blood gases drawn on room air revealed these values: air revealed these values:

• patient 1- pH =7.18, PCOpatient 1- pH =7.18, PCO22 = 70mmHg, = 70mmHg, POPO22=50mmHg, HCO=50mmHg, HCO33=24mEq/L; =24mEq/L;

• patient2- pH =7.31, PCOpatient2- pH =7.31, PCO22=50mmHg, =50mmHg, POPO22=50mmHg, HCO=50mmHg, HCO33=25mEq/L=25mEq/L

CommentComment

• The A-a gradient calculation for patient The A-a gradient calculation for patient 1 is as follows:1 is as follows:

• A-a DOA-a DO22 = PAO = PAO22 – PaO – PaO22

• PAOPAO22 = 150 – (1.25x PCO = 150 – (1.25x PCO22))

• PAOPAO22 = 150 – (1.25x 70) = 150 – (1.25x 70)

• PAOPAO22 = 62 = 62

• A-a =62 – 50A-a =62 – 50• A-a = 12A-a = 12

CommentComment

• The calculation reveals a normal The calculation reveals a normal gradient, indicating that the gradient, indicating that the etiology for hypoxemia and etiology for hypoxemia and hypoventilation is extrinsic to the hypoventilation is extrinsic to the lung itself.lung itself.

CommentComment

• The A-a gradient calculation for The A-a gradient calculation for patient 2 is as follows:patient 2 is as follows:

• PAOPAO22 = 150 – (1.25 x PCO = 150 – (1.25 x PCO22))• PAOPAO22 = 150 – (1.25 x 50) = 150 – (1.25 x 50)• PAOPAO22 = 150 – 63 = 150 – 63• PAOPAO22 = 87 = 87 • Therefore, A-a = 87 – 50 =37 (an Therefore, A-a = 87 – 50 =37 (an

abnormally increased gradient)abnormally increased gradient)

CommentComment

• We can be reasonably confident We can be reasonably confident that patient 1 suffered that patient 1 suffered hypoventilation due to the effect of hypoventilation due to the effect of the ingested drugs on the brain the ingested drugs on the brain stem. stem.

• Temporary mechanical ventilation Temporary mechanical ventilation restored this patient’s gas restored this patient’s gas exchange. exchange.

CommentComment

• Patient 2, on the other hand, had an Patient 2, on the other hand, had an increased A-a gradient, indicating a lung increased A-a gradient, indicating a lung problem in addition to any central cause problem in addition to any central cause for hypoventilation. for hypoventilation.

• The chest x-ray film revealed that this The chest x-ray film revealed that this patient’s overdose was complicated by patient’s overdose was complicated by aspiration pneumonitis and that the aspiration pneumonitis and that the patient required treatment with patient required treatment with antibiotics in addition to mechanical antibiotics in addition to mechanical ventilation.ventilation.

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