HIV Rx: Anes drug interactions
Basic, Basic Sciences
After inoculation, patients will often experience a flu-like illness. Over the first 4-8 weeks, patients have significant viremia with a drop in CD4+ cell count with a drop in virema and an increase in CD4+ cell count by the end of the first 4-8 weeks. At this time, antibodies will proliferate and can be detected with an ELISA test. Clinical latency and stability ensues for approximately 8-12 years before a decline with increasing viral load and decreasing CD4+ count. Signs/symptoms often include severe weight loss, persistent infections, pancytopenia and ultimately opportunistic infections. Patients typically start HAART therapy once their CD4+ count starts to decline or when they are at a point they can remain compliant with their treatment. This decision in made in conjunction with their Infectious Disease physician.
Studies suggest HAART therapy provides no protective benefit to reducing perioperative risk. Although, initiating therapy within 6 months preceding surgery increases overall morbidity and mortality. It is thought to be due to the Immune Reconstitution Inflammatory Syndrome (IRIS). Overall, there is a higher mortality rate at one year after surgery among HIV patient compared to patients who are HIV negative. It is thought to be due to HIV infection, not due to surgery.
HAART therapy includes 5 different classes of drugs; each targets various steps in the HIV replication cycle. Typical therapy includes at least 3 different classes and sometimes 4 classes.
The different classes and potential anesthetic implications are detailed below:
Nucleoside Reverse Transcriptase Inhibitors
This class of drugs may affect the clearance of methadone. Specifically, Zidovudine can cause bone marrow suppression (which can also be affected by the HIV infection itself). This drug may also cause severe myopathy and respiratory muscle dysfunction when concurrently used with corticosteroids.
Nonnucleoside Reverse Transcriptase Inhibitors (NNRTI)
These drugs may inhibit Cytochrome P450 and may prolong the effects/half-life of diazepam, midazolam, triazolam, fentanyl, meperidine, methadone.
These drugs may cause premature atherosclerosis and diastolic dysfunction, leading to complications including MI, CHF, pericarditis. Side effects may also include endocrine disturbances including glucose intolerance, lipid metabolism disorders and fat redistribution. Fat often redistributes to the neck, back of the neck and abdomen, having potential implications on intubation, aspiration risks and/or ventilation/respiratory complications. Other complications may include renal ATN or nephrolithiasis. Ritonavir and saquinovir inhibit cytochrome P450.
Integrase Strand Transfer Inhibitors
May alter the clearance of midazolam