Wednesday, August 19, 2009
After discussing an approach to dyspnea on exertion, the symptom of platypnea was discussed.
Platypnea is an increase in dyspnea in the upright position that improves on lying down.
Orthodeoxia is a decrease in oxygen saturation that occurs upon rising from supine.
These often occur together. They happen when there is right to left shunting that only occurs or is more pronounced, in the upright position. Shunts can be intracardiac (ASD, PFO) or intrapulmnary (AVM, hepatopulmonary syndrome).
This often occurs in HHT, when larger pulmonary AVMs are in bases of the bases of the lungs and therefore recevie a greater proportion of blood when the patient is upright. It can also occur for anatomic reasons in patients with intracardiac shunts.
Shunting can be seen with contrast ECHO where agitated saline bubbles are injected into peripheral veins. They appera in the right heart, and if a right to left shunt exists then they will appear in the left side of the heart. If they appear in 1-2 beats, the shunt is intracaridac, in 3-8 beats then it is likely intrapulmonmary.
Shunt fraction can be calculated by testing SaO2 and PaO2 before and after breating 100% oxygen fro 15 minutes. Normal is less than 5%.
International guidelines for the diagnosis and management of HHT (published by Toronto clinicians) can be found here.
A NEJM review of HHT can be found here.
A NEJM review of hepatopulmonary syndrome can be found here.
Friday, August 14, 2009
Here is a link to the JAMA Rational clinical exam article for Parkinson's Disease
Here is a link to a CMAJ review article on Parkinson's disease
When examining someone with potential Parkinsonism (in real life, but also consider if relevant on an exam), be sure to consider the "Parkinson plus" syndromes.
Here is a website with some interesting/rare medical conditions - not completely accurate descriptions and genetic causes for many are being discovered. Interesting nevertheless.
Here is the wikipedia page on Ken Jennings, the winningest player in Jeopardy history. He was defeated by Nancy Zerg in his 75th appearance.
Thursday, August 13, 2009
A great advanced discussion today that focused on monoarthritis.
The first step in assessing an "acute joint" is to determine if the process is articular, periarticular or referred.
If it is indeed an acute articular process the differential includes:
- a very good general rule, although as we learned today in classic presentations of other diseases, joint tap may be deferred
Crystal Arthropathy: Gout, Pseudogout (CPPD), Hydroxyapatite
Seropositive arthritis (early RA or SLE)
Seronegative arthritis (psoriatic, Ankylosing spondilitis, IBD, reactive)
A JAMA rational clinical exam article on septic arthritis is linked here and a CMAJ article on approach to acute monoarthritis is here. Gout is unusual in premenopausal women. An article on acute calcific periarthritis is linked here.
Not always necessary - may be helpful for
2)Evidence of crystal disease
3)Baseline study (i.e. to follow for development of pathology in future if septic joint, etc.)/to assess for obvious coexisting osteomyelitis.
Recurrent kidney stones
Gout and renal failure
Associate chronic joint changes
Frequent/severe attacks of gout
Uricosuric agents: - best in uric acid undexcretors (normal urine uric acid with high serum levels). Avoid if renal stones/uric acid nephropathy. Less effective in renal failure.
Xanthine oxidase inhibitor - decrease uric acid synthesis. Good for almost everyone, but need to consider drug interacations and adjusft for comorbidities (renal failure)
- Use minimum dose to achieve effect (follow serum urate levels)
- Azathioprine (Imuran) is mteabolized by xanthine oxidase (decrease Imuran dose by >50% and follow for toxicity)
- Not clear what its role will be vs allopurinol, and ongoing safety monitoring will be important to follow (as with any new med)
CONSIDER prophylaxis with colchicine (0.6 mg up to BID if normal CrCl) when initiating/titrating antihyperuricemic drugs - stop once normouricemic for 6 months.
Tuesday, August 11, 2009
The most important thing is to work hard and do good work - that is how you will build a good reputation.
SIRS: Two or more of the following: T>38.5°C or <35.0°c;>90 beats/min; RR >20 breaths/min or PaCO2 of <32>12,000 cells/mL, <4000>10 percent immature (band) forms.
Sepsis: SIRS secondary to an infection
Early goal directed therapy for sepsis is now the standard of care. A trial showing improved mortality using an early goal directed approach to sepsis can be found here, this trial is frequently referred to in the ICU as the Rivers' protocol.
Aimed at maintaining tissue perfusion:
1) Ensure adequate airway/breathing - intubate if necessary. Provide supplemental oxygen
2) Evaluate for signs of poor perfusion - frequent BP monitoring (consider art line - NEJM video on insertion here), LOC, Urine output, lactic acidosis, shock liver, etc.
3) Improve perfusion - FLUIDS!!!!!. Crystalloids (NS or Ringer's) are currently used as the first line resuscitation fluid. Patients often need >6L in the early stages of sepsis - be sure to monitor for signs of fluid overload, especially in those with renal or heart failure. Consider placing a central venous catheter - this provides secure venous access, can allow infusion of inotropes/pressors and can be used to monitor central venous oxygen saturatino and CVP.
4) Monitoring/"Advanced measures" - Involve the ICU/CCRT team. Activated Protein C (Xigris) and/or steroids should be considered in the right clinical context. Steroids are generally used now when shock persists despite adequate fluids and inotrope administration, or in patients on chronic steroids.
5) TREAT THE SOURCE - Identify and treat the cause of infection. In a large retrospective study, antimicrobial administration within the first hour of hypotension was associated with increased survival to hospital discharge in patients with septic shock. Culture potential sources and use appropriate broad spectrum antibiotics based on the suspected source and patient characteristics. Surgical evaluation and debridement should be rapdily arranged if necessary.
Thursday, August 6, 2009
The physiologically important calcium (Ca2+) is ionized calcium. This can be measured in the lab, however, total calcium is the value most commonly reported.
Calcium is bound to serum proteins, most importantly albumin. Therefore, in patients with low serum albumin concentration, the fraction of total serum Ca2+ that exists as ionized Ca2+ will be higher.
It is important to know the serum albumin when interpreting total serum calcium levels. A correction for total serum calcium can be made using the following formula (alternatively ionized Ca2+ could be measured):
Ca = SerumCa + 0.02 * (NormalAlbumin - PatientAlbumin) (SI UNITS)
Pseudohypercalcemia can occur when patients are hyperalbuminemic or have a multiple myeloma with a paraprotein that binds calcium (rare) - in these cases total CA2+ will be high, but ionized CA2+ will be normal.
Infusion rate depends on volume status, heart function, etc, but should target 100-1500 cc urine output/hr - do not need to hydrate beyond euvolemia
If severe/symptomatic consider: Bisphosphonates (IV) - will not take effect for 48-72 hrs, but will help maintain normal calcium when achieved.
Calcitonin by nasal spray or subQ is also very effective.
If hyperCa2+ is from sarcoid or lymphoma consider steroids (20-40 mg/day) - this works by decreasing calcitriol production from activated mononuclear cells in the lung and lymph nodes.
AVOID LASIX since most patients are profoundly volume depleted initially and once replete can cause hypokalemia, hypomagnesemia, and lead to recurrence of volume depletion. A recent Annals of Internal Medicine article reviews the use/concerns regarding Lasix in hypercalcemia.
Dialysis should be consider if the above fail/can't be done because of renal failure or heart failure.
When patients with chronic disease (such as Wegener's) present with an acute problem, one should consider if this is a process related or unrelated to their underlying disease. Attempts to evaluate the "activity" of the chronic disease should also be made.
When patients are admitted to hospital, careful thought should be given to what tests are ordered at time of admission. Although we should all try to attempt to minimize unnecessary investigations, if a patient is going to be in hospital for more than a few days it may be helpful to get "baseline" CXR, ECG and "routine bloodwork". This will may serve as a useful comparison should they develop further complications associated with their admission diagnosis or adverse events from hospitalization or treatment.
A 1997 NEJM review of small vessel vasculitis is available here.
A review of the evidence of PCP prophylaxis in non HIV infected patients is available here.