89 - Infectious Complications in the Injection Drug User

Summary

Intravenous drug abuse is a widespread public health problem because many of its medical complications (Table 89.1) are infectious due to the transmission of bloodborne infectious agents.

ENDOCARDITIS

Endocarditis, a life-threatening infection of the heart valves and/or endocardium, is associated with septic parenteral injections. Right-sided valvular infections are very frequent in injection drug users (IDU) because of septic inoculations. Intravenous injection with low-pressure venous return increases the susceptibility of right-sided structures to endocarditis. Concurrent pulmonary hypertension from drug adulterants, such as talc, may also predispose to right-sided valvular disease.

Despite the high prevalence of endocarditis, the offending pathogens are not specific to injectors. Staphylococcus aureus is the most commonly identified organism, but other pathogens are seen. These include Pseudomonas, Serratia, Streptococcus groups A and B, and Streptococcus viridans. Increasingly, fungal pathogens are seen with immunodeficiency.

Clinical diagnosis of endocarditis in the drug abuser can be difficult. The hallmark symptom is fever. Other constitutional symptoms such as chills, sweats, and arthralgia are less specific, but they are commonly observed in opiate-dependent patients during withdrawal. The physical signs associated with left-sided endocarditis are seldom present. Coexistent immunodeficiency appears to predispose to more severe systemic infections among human immunodeficiency virus (HIV-1)-infected IDU. Blood cultures may identify the offending pathogen and antimicrobial sensitivities.

Because clinical diagnosis alone presents challenges, echocardiographic findings have developed into the primary mechanism to diagnose and treat endocarditis.