Pocket Medicine: The Massachusetts General Hospital Handbook of Internal Medicine (26 page)

• Education and avoidance of environmental triggers for all Pts; yearly flu shot • Use quick-relief rescue medication as needed for all Pts • Goal to achieve
complete control
= daily sx ≤2/wk, Ø nocturnal sx or limitation of activity, reliever med ≤2/wk, nl PEF or FEV
₁
; partly controlled = 1–2 of the above present in a wk; uncontrolled = ≥3 of the above present in a wk • Step up treatment as needed to gain control, step down as tolerated • If PEF ↓ 15% × 2 d or ↓ 30%, 4× ICS dose ↓ need for PO steroids (
AJRCCM
2009;180:598) • Variants in glucocorticoid-induced transcript 1 gene a/w resp to ICS (
NEJM
2011;365:1173)

EXACERBATION

Evaluation

• History: baseline PEF, steroid requirement, ED visits, hospital admissions, prior intubation Current exacerbation: duration, severity, potential precipitants, meds used

Risk factors for life-threatening
: prior intubation, h/o near-fatal asthma, ED visit/hosp for asthma w/in 1 y, current/recent PO steroids, not using ICS, overdependent on SABA, Ψ, h/o noncompl

• Physical exam: VS, pulm, accessory muscle use, pulsus paradoxus, abdominal paradox

Assess for barotrauma: asymmetric breath sounds, tracheal deviation, subcutaneous air → pneumothorax, precordial (Hamman’s) crunch → pneumomediastinum

• Diagnostic studies:
PEF
(used to follow clinical course);
S
_a
O
₂
;
CXR
to r/o PNA or PTX ABG if severe: low P
_a
CO
₂
initially; nl or high P
_a
CO
₂
may
signify tiring

Initial treatment
(
NEJM
2010;363;755)

•
Oxygen
to keep S
_a
O
₂
≥90%

•
Inhaled SABA
(eg, albuterol) by MDI (4–8 puffs) or nebulizer (2.5–5 mg) q20min •
Corticosteroids
: prednisone 0.5–1 mg/kg PO; IV if impending resp arrest •
Ipratropium
MDI (4–6 puffs) or nebulizer (0.5 mg) q20min if severe (
Chest
2002;121:1977) • Epinephrine (0.3–0.5 mL SC of 1:1000 dilution) no advantage over inh SABA • Montelukast IV ↑ FEV
₁
but did not Δ rate of hosp (
  J Allergy Clin Immunol
2010;125:374) •
Reassess after 60–90 min of Rx

Mild-mod exacerbation: cont SABA q1h

Severe exacerbation: SABA & ipratropium q1h or continuously; ± Mg 2 g IV over 20 min (
Lancet
2003;361:2114); ± heliox (60–80%)

•
Decide disposition within 4 h of presentation and after
1–3 h of Rx

Figure 2-2 
Disposition of patients after initial treatment of asthma exacerbation

ICU-level care

•
High-dose steroids
: methylprednisolone 125 mg IV q6h (
Archives
1983;143:1324) •
Invasive ventilation
:

large ET tube, P
_plat
<30 cm H
₂
O (predicts barotrauma better than PIP), max exp time

PEEP individualized to Pt physiology

paralysis, inhalational anesthetics, bronchoalveolar lavage w/ mucolytic, heliox (60–80% helium) and ECMO have been used with success

• NPPV likely improves obstruction (
Chest
2003;123:1018), but controversial and rarely used

ANAPHYLAXIS

Definition and pathophysiology (
Ann Emerg Med
2006;47:373)

• Severe, rapid-onset (mins to hrs), potentially life-threatening systemic allergic response • IgE-mediated mast cell degranulation with release of histamine, tryptase and TNF

• Precipitates systemic reactions (bronchospasm, tissue swelling, fluid shifts, vasodilation) • Common triggers: penicillins, cephalosporins, shellfish, nuts, insect stings, IV contrast (not truly an IgE-mediated mechanism, but clinically similar)
Diagnosis:
any of the three following criteria
1) Acute illness with skin ± mucosal involvement (rash, flushing, hives), AND at least one of:

• Respiratory compromise (wheeze, stridor, dyspnea, hypoxemia)

• Hypotension or hypoperfusion (syncope, incontinence)

2) Two or more of the following after exposure to a
likely
allergen: skin/mucosal involvement, respiratory compromise, ↓ BP or hypoperfusion, GI symptoms 3) Hypotension after exposure to
known
allergen for that Pt

Treatment

•
Epinephrine
: IM or SC 0.3–0.5 mL of 1:1000 dilution (1 mg/mL) q5–20min; if HoTN or cardiac arrest, IV (or via ETT) 2.5–10 mL of 1:10,000 dilution q5min ± gtt •
Airway management
: suppl O
₂
± intubation (or cricothyroidotomy if laryngeal edema) β
₂
-agonists (stacked or continuous nebulizers) for refractory bronchospasm • Fluid resuscitation w/ lg volume of crystalloid (may extravasate up to 35% of blood volume) • Antihistamines relieve hives & itching,
no effect on airway or hemodynamics
H1RA (diphenhydramine 50 mg IV/IM) ± H2RA (eg, ranitidine 50 mg IV) • Corticosteroids have no immediate effect but may help prevent relapse: methylprednisolone 125 mg IV q6h if severe or prednisone 50 mg PO

• Glucagon (1–5 mg IV over 5 min) if inotropic or chronotropic support needed in Pt taking bB

• Avoid unopposed a-adrenergic vasopressors

Disposition

• Mild rxn limited to urticaria or mild bronchospasm can be observed for ≥6 h; admit all others • Watch for biphasic reaction; occurs in 23%, typically w/in 8–10 h but up to 72 h

• At time of d/c: education re: allergen avoidance, instruction and Rx for EpiPen, allergist f/u

CHRONIC OBSTRUCTIVE PULMONARY DISEASE

Definition and epidemiology
(
NEJM
2004;350:26)

• Progressive airflow limitation caused by airway and parenchymal inflammation

Pathogenesis
(
Lancet
2003;362:1053)

•
Cigarette smoke
(centrilobular emphysema, affects 15–20% of smokers)

• Recurrent airway infections

• ɑ
₁
-antitrypsin defic.: early-onset panacinar emphysema, 1–3% of COPD cases. Suspect if age <45, lower lungs affected, extrathoracic manifestations (liver disease [not if MZ subtype], FMD, pancreatitis). ✓ serum AAT level (nb, acute phase reactant).

Clinical manifestations

• Chronic cough, sputum production, dyspnea; later stages → freq exac., a.m. HA, wt loss

• Exacerbation triggers: infxn, other cardiopulmonary disease, incl. PE (
Annals
2006;144:390)

Infxn: overt tracheobronchitis/pneumonia from viruses,
S. pneumoniae
,
H. influenzae
,
M. catarrhalis
or triggered by changes in strain of colonizers (
NEJM
2008;359:2355)

• Physical exam: ↑ AP diameter of chest (“barrel-chest”), hyperresonance, ↓ diaphragmatic excursion, ↓ breath sounds, ↑ expiratory phase, rhonchi, wheezes during exacerbation: tachypnea, accessory muscle use, pulsus paradoxus, cyanosis

Diagnostic studies

• CXR (see Radiology inserts): hyperinflation, flat diaphragms, ± interstitial markings & bullae

• PFTs:
Obstruction
: ↓↓ FEV
₁
, ↓ FVC,
FEV
₁
/FVC <0.7 (no sig
Δ
post bronchodilator)
, expiratory scooping of flow-volume loop;
Hyperinflation
: ↑↑ RV, ↑ TLC, ↑ RV/TLC;

Abnormal gas exchange
: ↓ D
_L
CO (in emphysema)

• ABG: ↓ P
_a
O
₂
, ± ↑ P
_a
CO
₂
(in chronic bronchitis, usually only if FEV
₁
<1.5 L) and ↓ pH

• ECG: PRWP, S1S2S3, R-sided strain, RVH, ↑ P waves in lead II (“P pulmonale”)

Chronic treatment
(
NEJM
2010;362:1407;
Lancet
2012;379:1341)