Instructor: Professor Yuan
Session 1 Assignment: Pericardial Effusion
A pericardial effusion occurs when more than average fluid accumulates between the heart and pericardium. Normally, there is about 50 mL of pericardial fluid, so any more than that would qualify as a pericardial effusion.
The severity of a pericardial effusion depends on how much fluid is present and how quickly that fluid accumulates. Acutely, the heart can accommodate 80-120 mL of fluid and still function, while gradually, it can accommodate up to 2 L of fluid because the pericardium will have time to expand and the heart will be able to get used to working around it. When the pericardial effusion becomes severe, we become concerned about cardiac tamponade, where the fluid build-up prevents the ventricles from properly filling and pumping blood and the patient becomes hemodynamically unstable.
Pericardial effusion has many different etiologies; these include:
- Acute pericarditis (viral, bacterial, tuberculous, or idiopathic in origin)
- Autoimmune disease (like RA or SLE)
- Post MI or cardiac surgery
- Sharp or blunt chest trauma, including a cardiac diagnostic or interventional procedure
- Malignancy, particularly metastatic spread of noncardiac primary tumors
- Mediastinal radiation
- Renal failure with uremia
- Myxedema
- Aortic dissection extending into the pericardium
- Selected drugs
Pericardial effusions are usually incidental findings because they are typically asymptomatic unless there is progression into cardiac tamponade, where one might observe Beck’s triad (hypotension, muffled heart sounds, and JVD), fatigue, SOB, and edema. If there are any symptoms present in a simple pericardial effusion, they usually align with the specific etiology causing the effusion.
In terms of diagnosis, we can rely on a combination of EKG, chest x-ray, and echocardiogram, but CT and MRI will also show the presence of a pericardial effusion. EKG might show sinus tachycardia, low QRS voltage, and electrical alternans, but these are nonspecific. Chest x-ray might show the effusion if it is large enough or if the patient is positioned in the right way, but as we saw with out patient, the AP view did not actually show the effusion and we had to get the lateral view to see it. It would show an enlarged cardiac silhouette, but this is also nonspecific. Echocardiogram is the go-to test to diagnose a pericardial effusion, which can be visualized in the image and video below.
Not all pericardial effusions require treatment; acute small pericardial effusions can be monitored for up to a week to see if it gets larger to dictate treatment. If it remains small, there is no need to treat it. Moderate and large pericardial effusions, however, should be treated through pericardiocentesis. Additionally, if the etiology of the effusion is unclear, some pericardial fluid can be removed and analyzed to determine the cause. Cardiac tamponade is also an indication for emergent pericardiocentesis. If the fluid reaccumulates very quickly to become symptomatic after the pericardiocentesis, a pericardial window is the definitive treatment. Some patients have a chronic pericardial effusion, but serial pericardiocentesis is not recommended as long as the patient remains hemodynamically stable.
https://www.uptodate.com/contents/diagnosis-and-treatment-of-pericardial-effusion?search=pericardial%20effusion&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1#H15
Session 2 Assignment: Discuss getting a CT with contrast with a patient with a Creatinine of 2 and eGFR of 35 and suspected peripheral artery disease
Session 3 Assignment: Discuss the antibiotics the cover MRSA soft tissue infections.
In the case we discussed, our patient had an abscess on the dorsal side of his hand. We discussed the possibility of the causative organism being MRSA, so my assignment was to discuss the treatment options for MRSA. Since we were discussing a soft tissue infection and soft tissue infections are the most common source of non-nosocomial MRSA infections, I focused on that in terms of treatment.
Since there is high community prevalence of MRSA in skin and soft tissue infections, we always want to cover MRSA empirically when choosing an antibiotic.
Oral treatment can be considered in patients with mild infections, meaning that they have a localized infection without any systemic symptoms. Agents appropriate in this kind of treatment include:
- Trimethoprim-sulfamethoxazole (Bactrim DS)
- Clindamycin
- Tetracyclines (most commonly doxycycline or minocycline, but occasionally omadacycline)
- Oxazolidinones (linezolid and tedizolid)
- Delafloxacin (Baxdela)
Of these oral options, Bactrim DS and Clindamycin are the most commonly used, as they have the greatest success rates. Despite their comparable efficacy, Bactrim DS is more commonly used because of the developing resistance patterns to Clinamycin, but it can still be used as long as there is less than 10-15% resistance in the local population it is being used on. Use of the Doxycycline and Minocycline is less reliable, as there is not as much evidence of their efficacy. Omadacycline, the oxazilidinones, and Delafloxacin are typically reserved for MRSA skin infections that are not responsive to or cannot take the other, more commonly used agents because of their cost and adverse effects.
Parenteral treatment is considered in more severe infections, meaning that the infection is extensive, there are systemic symptoms, the patient’s condition has worsened rapidly, there is no improvement after 2-3 days of oral therapy, the patient is immunocompromised, or the infection is close to any indwelling device, including prosthetics and grafts. Option for treatment include:
- Vancomycin
- Daptomycin
- Oxazolidinones(linezolid andtedizolid)
- Delafloxacin (Baxdela)
- Omadacycline
- 5th generation cephalosporins (ceftaroline or ceftobiprole [only available in Canada and Europe])
- Lipoglycopeptides (Dalbavancin, oritavancin, and telavancin)
Of these options, vancomycin is the most commonly used, although daptomycin is an appropriate alternative. The oxazolidinones, again, should be reserved for patients who either cannot take the more common antibiotics or have not responded well with other agents due to their cost and adverse effects. Delafloxacin is a good option if you are trying to cover MRSA, gram negatives, and Pseudomonas. The lipoglycopeptides are long-acting agents, so they may be good alternatives for patients who require parenteral therapy but do not require inpatient care.
In all cases, patients typically receive treatment for 5 – 14 days.
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