Pocket Medicine: The Massachusetts General Hospital Handbook of Internal Medicine (31 page)

spontaneous bacterial empyema (SBEM) can occur (even w/o SBP being present), ∴ thoracentesis if suspect infection

transplant is definitive treatment and workup should begin immediately

VENOUS THROMBOEMBOLISM (VTE)

Definitions

• Proximal deep venous thrombosis (DVT): thrombosis of popliteal, femoral or iliac veins

(nb, “superficial” femoral vein part of deep venous system)

• Pulmonary embolism (PE): thrombosis originating in venous system and embolizing to pulmonary arterial circulation; 1 case/1000 person y; 250,000/y (
Archives
2003;163:1711)
Risk factors

• Virchow’s triad for thrombogenesis

stasis
: bed rest, inactivity, CHF, CVA w/in 3 mo, air travel >6 h (
NEJM
2001;345:779)

injury to endothelium
: trauma, surgery, prior DVT, inflammation

thrombophilia
: APC resistance, protein C or S deficiency, APS, prothrombin gene mutation,↑ factor VIII, hyperhomocysteinemia, HIT, OCP, HRT, tamoxifen, raloxifene

• Malignancy (12% of “idiopathic” DVT/PE) • History of thrombosis (greater risk of recurrent VTE than genetic thrombophilia) • Statin therapy ↓ risk (
NEJM
2009;360:1851)

Clinical manifestations—DVT

• Calf pain, swelling (>3 cm c/w unaffected side), venous distention, erythema, warmth, tenderness, palpable cord,
Homan’s sign (calf pain on dorsiflexion, seen in <5% of Pts),
phlegmasia cerulea dolens:
stagnant blood → edema,
cyanosis
, pain • 50% of Pts with sx DVT have asx PE

Diagnostic studies—DVT

• D-dimer: <500 helps r/o; ? use 1000 as threshold if low risk (
Annals
2013;158:93) • Compression U/S >95% Se & Sp for sx DVT (lower for asx DVT); survey whole leg rather than just proximal if ≥mod prob (
  JAMA
2010;303:438); venography rarely used

Figure 2-3 Approach to suspected DVT (
Chest
2012;141:e351S)

Clinical manifestations—PE

• Dyspnea (73%), pleuritic chest pain (66%), cough (37%), hemoptysis (13%) • ↑ RR (>70%), crackles (51%), ↑ HR (30%), fever, cyanosis, pleural friction rub, loud P
₂

•
Massive
: syncope, HoTN, PEA; ↑ JVP, R-sided S
₃
, Graham Steell (PR) murmur

Diagnostic studies—PE
(
NEJM
2010;363:266)

• CXR (limited Se & Sp): 12% nl, atelectasis, effusion, ↑ hemidiaphragm, Hampton hump (wedge-shaped density abutting pleura); Westermark sign (avascularity distal to PE) • ECG (limited Se & Sp): sinus tachycardia, AF; signs of RV strain → RAD, P pulmonale, RBBB, S
_I
Q
_III
T
_III
& TWI V
₁
–V
₄
(McGinn-White pattern,
Chest
1997;111:537) • ABG: hypoxemia, hypocapnia, respiratory alkalosis, ↑ A-a gradient (
Chest
1996;109:78) 18% w/ room air P
_a
O
₂
85–105 mmHg, 6% w/ nl A-a gradient (
Chest
1991;100:598) • D-dimer: high Se, poor Sp (~25%);
ELISA has >99% NPV and can be used to r/o PE in Pts w/ “unlikely” pretest prob. (
  JAMA
2006;295:172) • Echocardiography: useful for risk stratification (RV dysfxn), but not dx (Se <50%) • V/Q scan: high Se (~98%), low Sp (~10%). Sp improves to 97% for high prob VQ. Use if pretest prob of PE high and CT not available or contraindicated. Can also exclude PE if low pretest prob, low prob VQ, but 4% false
(
  JAMA
1990;263:2753).

•
CT angiography
(CTA; see Radiology inserts): Se
90% & Sp
95% w/ MDCT (
NEJM
2006;354:2317); PPV & NPV >95% if imaging concordant w/ clinical suspicion, ≤80% if discordant (∴ need to consider both); CT may also provide other dx • Lower extremity compression U/S shows DVT in ~9%, sparing CTA, but when added to CTA, does not Δ outcomes (
Lancet
2008;371:1343) • Pulmonary angio: ? gold standard (morbidity 5%, mortality <0.5%), infrequently performed • MR angiography: Se 84% (segmental) to 100% (lobar) (
Lancet
2002;359:1643); if add MR venography, Se 92%, Sp 96% (
Annals
2010;152:434)

Figure 2-4 Approach to suspected PE using CTA

Workup for idiopathic VTE

•
Thrombophilia workup
: ✓ if
FH, consider if age <50 y or on OCP/HRT. Send panel 2 wk after complete anticoagulation, as thrombus, heparin and warfarin Δ results. Nb, does not change management after 1st idiopathic DVT if plan for long-term anticoagulation (
  JAMA
2005;293:2352;
Blood
2008;112:4432;
Am J Med
2008;121:458).