0071643192.pdf

HEMATOLOGY, ONCOLOGY, ALLERGY,

AND IMMUNOLOGY

Glycoprotein IIb/IIIa Inhibitors

GP IIb/IIIa inhibitors prevent binding of fibrinogen on the IIb/IIIa receptor
which inhibits platelet activation. Most sources recommend addition of
GP IIb/IIIa inhibitors to conventional anticoagulation for patient receiving per-
cutaneous coronary intervention. GP IIb/IIIa inhibitors include abciximab,
tirofiban, eptifibatide.

CONTRAINDICATION

■ Hypersensitivity, bleeding disorder, severe hypertension (SBP >200 mmHg),
severe renal insufficiency, major surgery in the preceding 6 weeks, history
of hemorrhagic stroke, ischemic stroke within past 30 days

COMPLICATION

■ Bleeding, hypersensitivity

DYSHEMOGLOBINEMIAS

A 60-year-old patient is undergoing placement of a nasogastric tube.

Benzocaine is used to anesthetize the posterior pharynx. The patient’s O 2

saturation drops to 83% without improvement with supplemental treat-

ment. What is your suspected diagnosis?

Methemoglobinemia.

Metheomoglobinemia

In the presence of non-O 2 oxidizing agents, Fe2+changes to Fe3+. Hemoglobin-
containing Fe3+does not bind O 2 and is referred to as methemoglobin.

CAUSES

■ Nitrates (in well water or vegetables)
■ Medications: Lidocaine, benzocaine, nitrates, nitroglycerin, nitroprusside,
sulfonamides, dapsone, phenazopyridine (pyridium)

SYMPTOMS/EXAM

■ Bluish skin discoloration, anxiety, headache, lightheadedness
■ Symptoms include tachypnea, tachycardia, myocardial ischemia, seizures,
coma. Classically see pulse oximetry of 80–85% without response to supple-
mental O 2. However, pulse oximetry is an unreliable test in the presence of
methemoglobinemia. Actual tissue O 2 availability may be much lower than
suggested by pulse oximetry.
■ Chocolate brown bloodon venipuncture
■ May become more symptomatic at lower levels with underlying anemia or
pulmonary disease

DIFFERENTIAL

■ Hypoxemia
■ Decreased FiO 2 (altitude)
■ Hypoventilation
■ Ventilation-perfusion mismatch
■ Right-to-left shunt
■ Dyshemoglobinemia (methemoglobinemia or sulfhemoglobinemia)

Treat methemoglobinemia

with methylene blue.

The amyl nitrite and sodium

nitrite in the Cyanide Antidote

Kit or “Lilly Kit” work by

inducing a

methemoglobinemia, which

scavenges cyanide. Use the

“Lilly Kit” to treat cyanide

toxicity, not

methemoglobinemia.