- Risk Factors
- Etiology
- Pathology
- Management & Treatment
- Epidemiology
- Prevention
- Complications
- Prognosis
- Research Frontier
- Clinical Case Studies
- Study Questions
Content 12
Content 9
Complications of Injecting Drug Use
- Local problems—Abscess (Figures 240-2
and 240-3; Abscess), cellulitis, septic thrombophlebitis, local induration, necrotizing fasciitis, gas gangrene, pyomyositis, mycotic aneurysm, compartmental syndromes, and foreign bodies (e.g., broken needle parts) in local areas.2A 32-year-old woman with type 1 diabetes developed large abscesses all over her body secondary to injection of cocaine and heroin. Her back shows the large scars remaining after the healing of these abscesses. (Courtesy of Richard P. Usatine, MD.)
- IDUs are at higher risk of getting methicillin-resistant Staphylococcus aureus(MRSA) skin infections that the patient may think are spider bites (Figure 240-4).
- Some IDUs give up trying to inject into their veins and put the cocaine directly into the skin. This causes local skin necrosis that produces round atrophic scars (Figure 240-5).
- IDUs are at risk for contracting systemic infections, including HIV and hepatitis B or hepatitis C.
- Injecting drug users are at risk of endocarditis, osteomyelitis (Figures 240-6and 240-7), and an abscess of the epidural region. These infections can lead to long hospitalizations for intravenous antibiotics. The endocarditis that occurs in IDUs involves the right-sided heart valves (see Chapter 50, Bacterial Endocarditis).2 They are also at risk of septic emboli to the lungs, group A β-hemolytic streptococcal septicemia, septic arthritis, and candidal and other fungal infections.
Content 3
Content 13
A 73-year-old man is scheduled for emergency relief of an intestinal obstruction from a sigmoid volvulus. The patient had a myocardial infarction 1 month earlier that was complicated by congestive heart failure. His blood pressure is 160/90 mm Hg, pulse 110 beats/min, respiratory rate 22 breaths/min, and temperature 38.8°C.
Why is this case an emergency?
Strangulation of the bowel begins with venous obstruction, but can quickly progress to arterial occlusion, ischemia, infarction, and perforation. Acute peritonitis could lead to severe dehydration, sepsis, shock, and multiorgan failure.
What special monitoring is appropriate for this patient?
Because of the history of recent myocardial infarction and congestive heart failure, an arterial line would be useful. Transesophageal echocardiography and pulse contour analysis monitors of cardiac output could be used. Pulmonary arterial flotation catheters have often been used in the past, but they are associated with significant complications and current evidence does not indicate that their use improves patient outcomes. Large fluid shifts should be anticipated. Furthermore, information regarding myocardial supply (diastolic blood pressure) and demand (systolic blood pressure, left ventricular wall stress, and heart rate) should be continuously available. Central venous pressure may not track left atrial pressure in a patient with significant left ventricular dysfunction.
What cardiovascular medications might be useful during induction and maintenance of general anesthesia?
Drugs causing severe tachycardia or extremes in arterial blood pressure should be avoided.
During the laparotomy, gradual increases in heart rate and blood pressure are noted. ST-segment elevations appear on the electrocardiogram. A nitroglycerin infusion is started. The heart rate is now 130 beats/min, and the blood pressure is 220/140 mm Hg. The concentration of volatile anesthetic is increased, and metoprolol is administered intravenously in 1-mg increments. This results in a decline in heart rate to 115 beats/min, with no change in blood pressure. Suddenly, the rhythm converts to ventricular tachycardia, with a profound drop in blood pressure. As amiodarone is being administered and the defibrillation unit prepared, the rhythm degenerates into ventricular fibrillation.
What can explain this series of events?
A differential diagnosis of pronounced tachycardia and hypertension might include pheochromocytoma, malignant hyperthermia, or thyroid storm. In this case, further inspection of the nitroglycerin infusion reveals a labeling error: although the tubing was labeled “nitroglycerin,” the infusion bag was labeled “epinephrine.”
How does this explain the paradoxic response to metoprolol?
Metoprolol is a β1-adrenergic antagonist. It inhibits epinephrine’s β1-stimulation of heart rate, but does not antagonize α-induced vasoconstriction. The net result is a decrease in heart rate, but a sustained increase in blood pressure.
What is the cause of the ventricular tachycardia?
An overdose of epinephrine can cause life-threatening ventricular arrhythmias. In addition, if the central venous catheter was malpositioned, with its tip in the right ventricle, the catheter tip could have stimulated ventricular arrhythmias.
What other factors may have contributed to this anesthetic mishap?
Multiple factors will often combine to create an anesthetic misadventure. Incorrect drug labels are but one example of errors that can result in patient injury. Inadequate preparation, technical failures, knowledge deficits, and practitioner fatigue or distraction can all contribute to adverse outcomes. Careful adherence to hospital policies, checklists, patient identification procedures, and surgical and regional block timeouts can all help to prevent iatrogenic complications.
A
A 75-year-old triathlete complains of gradually worsening vision over the past year. It seems to be involving near and far vision. The patient has never required corrective lenses and has no significant medical history other than diet-controlled hypertension. He takes no regular medications. Physical examination is normal except for bilateral visual acuity of 20/100. There are no focal visual field defects and no redness of the eyes or eyelids. Which of the following is the most likely diagnosis?
The correct answer is A. You answered A.
Age-related macular degeneration is a major cause of painless, gradual bilateral central visual loss. It occurs as nonexudative (dry) or exudative (wet) forms. Recent genetic data have shown an association with the alternative complement pathway gene for complement factor H. The mechanism link for that association is unknown. The nonexudative form is associated with retinal drusen that leads to retinal atrophy. Treatment with vitamin C, vitamin E, beta-carotene, and zinc may retard the visual loss. Exudative macular degeneration, which is less common, is caused by neovascular proliferation and leakage of choroidal blood vessels. Acute visual loss may occur because of bleeding. Exudative macular degeneration may be treated with intraocular injection of a vascular endothelial growth factor antagonist (bevacizumab or ranibizumab). Blepharitis is inflammation of the eyelids usually related to acne rosacea, seborrheic dermatitis, or staphylococcal infection. Diabetic retinopathy, now a leading cause of blindness in the United States, causes gradual bilateral visual loss in patients with long-standing diabetes. Retinal detachment is usually unilateral and causes visual loss and an afferent pupillary defect.
Mr. Jenson is a 40-year-old man with a congenital bicuspid aortic valve who you have been seeing for more than a decade. You obtain an echocardiogram every other year to follow the progression of his disease knowing that bicuspid valves often develop stenosis or regurgitation requiring replacement in middle age. Given his specific congenital abnormality, what other anatomic structure is important to follow on his biannual echocardiograms?
The correct answer is A. You answered A.
The answer is A. (Chap. 282) Bicuspid aortic valve is among the most common of congenital heart cardiac abnormalities. Valvular function is often normal in early life and thus may escape detection. Due to abnormal flow dynamics through the bicuspid aortic valve, the valve leaflets can become rigid and fibrosed, leading to either stenosis or regurgitation. However, pathology in patients with bicuspid aortic valve is not limited to the valve alone. The ascending aorta is often dilated, misnamed “poststenotic” dilatation; this is due to histologic abnormalities of the aortic media and may result in aortic dissection. It is important to screen specifically for aortopathy because dissection is a common cause of sudden death in these patients.