Pocket Medicine: The Massachusetts General Hospital Handbook of Internal Medicine (82 page)

• Reasons for failure to improve on initial Rx:
Insufficient time: may take ≥72 h to see clinical improvement

Insufficient drug levels: eg, vanco trough <15–20 µg/mL (needed for lung penetration)

Resistant organisms (or superinfxn): eg, MRSA,
Pseudomonas
; consider
bronchoscopy

Wrong dx: fungal/viral, chemical pneumonitis, PE, CHF, ARDS, DAH, ILD;
consider CT

Parapneumonic effusion/empyema/abscess: esp. seen w/ strep; if CXR
,
consider CT
(dx tap ± chest tube if effusion present, esp. if loculated)

Metastatic infection (eg, endocarditis, meningitis, arthritis)

Prognosis

• Pneumonia and influenza are the 8th leading cause of death in the U.S.

• For low-risk Pts, can discharge immediately after switching to PO abx (
CID
2007;44:S27) • CXR resolves in most by 6 wk; consider f/u to r/o underlying malignancy (esp. if age >50 y or smoker,
Archives
2011;171:1192) or other dx • Severe CAP (generally requiring ICU) defined as: septic shock, resp failure, or ≥3 of: RR ≥30, P
_a
O
₂
/F
_i
O
₂
≤250, <36°C, HoTN, DMS, multilobar, WBC <4k, plt <100, BUN ≥19.9, metabolic acidosis, ↑ lactate (ATS/IDSA criteria,
CID
2007;44:S27) •
SMART-COP
risk score:
S
BP <90 (2 points),
M
ultilobar infiltrates,
A
lb <3.5 g/dL,
R
R ≥30,
T
achycardia (HR >125),
C
onfusion,
O
₂
sat <90% (2 points), arterial
p
H <7.35 (2 points) score ≥3 points has Se ~60–90% & Sp 45–75% for need for ICU care (
CID
2008;47:375)

Prevention

• Pneumococcal vaccine (PPSV23):
all
persons >65 y of age. If high-risk comorbidity, give at younger age and consider additional vaccination with PCV13.

• VAP precautions: HOB >30°, chlorhexidine rinse; aspiration precautions in high-risk Pts • Tdap booster: 1 time dose in adults with uncertain vaccination history (
MMWR
2012; 61:468)

VIRAL RESPIRATORY INFECTIONS

URI, bronchitis, bronchiolitis, pneumonia
(
Lancet
2011;377:1264)
Microbiology & epidemiology

• Typical pathogens: short, mild = rhinovirus, coronavirus; longer, more severe or complicated =
influenza
, parainfluenza, respiratory syncytial virus (RSV), adenovirus, metapneumovirus. Can be esp. severe in immunosupp.

• Seasonal flu: 365,000 hosp, 51,000 deaths per y in U.S.; most >65 y (
NEJM
2008;359:2579) • Pandemic 2009 H1N1 (swine): more severe in younger and obese Pts (
JAMA
2009;302:1896) • Sporadic 2011 H3N2: adults exposed to swine (also human-to-human) (
MMWR
2011;60:1615) • H5N1 influenza (avian): ongoing small outbreaks globally.

• For weekly influenza updates:
http://www.cdc.gov/flu/weekly

Diagnosis

• Primarily clinical:
cough
,
fever
,
myalgias
, arthralgias, rhinorrhea, pharyngitis (in contrast, viral bronchitis p/w cough ± low-grade temp; usually benign & self-limited) • Respiratory viral panel on nasal washing or sputum/BAL

• Rapid influenza test on nasal swab: Se ~50–70% (? lower for pandemic flu), Sp >95%

• DFA (Se ∼85%), RT-PCR (gold standard) avail. for influenza (PCR distinguishes type)

Treatment
(
NEJM
2008;359:2579)

• Seasonal influenza: treat with neuraminidase inhib. (oseltamivir, zanamivir), which are effective vs. A & B, but resistance emerging. M2 inhib. (amantadine, rimantadine) not recommended due to widespread resistance (
MMWR
2011;60:1).

• Pandemic H1N1: nearly 100% sens. to
oseltamivir
. H5N1: Uncertain resistance pattern.

H7N9: newly emerging in Asia (
NEJM
2013;368:1888)

• Oseltamivir dosed 75 mg PO bid × 5 d. Must start w/in 48h of sx for low-risk; for critically ill or immunosupp., start ASAP even if >48 h.

• Consider inhaled ribavirin for RSV in immunosupp. (eg, BMT, lung tx); limited adult data
Prevention

• Inactivated
influenza vaccine
: incl. H1N1. Rec for
all
>6 mo of age and esp. if pregnant, >50 y, immunosupp., or HCW (
MMWR
2012;61:613) • Isolation, droplet precautions for inPts strongly recommended

• Prophylaxis for high-risk contacts of confirmed influenza: oseltamivir 75 mg PO daily × 10 d

FUNGAL INFECTIONS

Candida
species

•
Microbiology
: normal GI flora;
C. albicans
& nonalbicans spp. (consider azole resistance if h/o Rx or nonalbicans;
C. parapsilosis
↑ echinocandin resistant). Sensi testing available.

•
Risk factors
: neutropenia, immunosupp., broad-spectrum abx, intravascular catheters (esp. if TPN), IVDU, abd surgery, DM, renal failure, age >65

•
Clinical manifestations

Mucocutaneous: cutaneous (eg, red, macerated lesions in intertriginous zones); oral thrush (exudative, erythematous or atrophic; if unexplained, r/o HIV); esophageal (odynophagia; ± oral thrush); vulvovaginal, balanitis

Candiduria: typically colonization due to broad-spectrum abx and/or indwelling catheter

Candidemia (#4 cause of health care assoc. bloodstream infxn): r/o retinal involvement (req ↑ Rx); endocarditis rare but serious (esp. w/ nonalbicans & prosthetic valve)

Hepatosplenic: intestinal seeding of portal & venous circulation; esp. in acute leukemia

Hematogenous dissemination: lung, brain, meninges,
etc.

Cryptococcus
(
CID
2010;50:291)

•
Epidemiology
: immunosupp. (esp. AIDS) most susceptible; can occur in healthy host, esp. elderly, EtOH, DM. If from Pacific NW, consider
C. gatti
(↑ mortality in healthy host).

•
Clinical manifestations

CNS
(meningitis): HA, fever, meningismus, ↑ ICP, CN abnl, ± stupor, often subacute. Dx: CSF CrAg, India ink stain, fungal cx. Cell counts vary; serum CrAg >1:8 Se/Sp in AIDS.

Other sites: pulm, GU, cutaneous, CNS cryptococcoma.
With any crypto dx, LP all Pts
.

•
Treatment

CNS: If ↑ ICP, repeat large-volume LPs or temp. lumbar drain; few require VP shunt

In HIV
or immunosupp. Pts, CNS Rx has induction (ampho ± flucytosine), consolidation and maintenance (fluconazole) phases (
NEJM
2013
;
368:1291). If r/o CNS disease, then fluconazole. Dosing and duration vary by host.

Non-CNS disease in healthy Pts: fluconazole vs. observation, based on clinical setting

Histoplasmosis
(
CID
2007;45;807)

•
Endemic
: central & SE U.S. (esp. in areas w/ bird & bat droppings), river banks elsewhere •
Clinical manifestations

Acute: often subclinical, but may see mild to severe PNA ± cavitary & hilar LAN

Chronic pulm: ↑ productive cough, wt loss, night sweats, apical infiltrates, cavitation

Disseminated (typically in immunosupp.): fever, wt loss, HSM, LAN, oral ulcers, skin lesion, fibrosing mediastinitis, reactive arthritis, pericarditis

•
Treatment
: itraconazole (monitor levels); ampho ± steroids if severe or immunosupp.

Coccidioidomycosis (
CID
2005;41:1217)

•
Endemic
: SW U.S. (San Joaquin or “Valley” fever) •
Clinical manifestations

Acute: 50–67% subclinical; PNA w/ cough, chest pain, fever, arthralgias,
fatigue

Chronic pulm: nodule(s), cavity or progressive fibrocavitary PNA (can be asx or sx)

Disseminated (typically in immunosupp.): fever, malaise, diffuse pulmonary process, bone, skin, & meningeal involvement