Salter-Harris Growth Plate Fracture Classification

The Salter-Harris fracture classification has to be just about the most sensible classification systems in medicine, as least as far as the mnemonic goes.Β It is a system used to grade growth plate fractures and conveniently uses Salter’s name as the way to remember.

  1. SEPARATED (the bone and the growth plate have come apart) – but it actually looks normal on x-ray (you can only tell on physical exam)
  2. Fracture ABOVE the growth plate
  3. Fracture LOWER (below) the growth plate – fracture extends to the articular surface
  4. Fracture THROUGH the growth plate
  5. Fracture ERASING/compressing/squashing the growth plate – this is the worst kind because with disruption of the growth plate comes disruption of growth. Some odd things can cause these ones like frostbite, electric shock and irradiation. They’re hard to see on x-rays but show up on MRIs.

Cephalosporins (generations and spectrum of activity)

Cephalosporins work much like penicillins, inhibiting peptidoglycan cell wall synthesis in bacteria (remember those sites of action and mechanisms?)

Of course the issue is that they just keep making new cephalosporins and each generation is a little bit different in terms of its spectrum and whether it’s better at fighting Gram positive or Gram negative bacteria. Generally the newer the generation, the more broad spectrum and less Gram positive coverage. To add another layer to the confusion, there are separate oral and IV cephalosporins for each generation and all of the cephalosporins are usually recognizable by starting with “CEF-” or “KEF-” (except for Suprax and Ancef, who ever came up with those brand names didn’t get the memo)

 

Bacteria involved in bite wounds

With bites you need to consider not only the ton of different bacteria inhabiting the mouth of whatever/whoever was the biter, but also the flora of whatever part of the body was bitten. Mouths tend to be a schmogourbord of Gram positives and negative, aerobes and anaerobes. The two bugs to specifically keep in mind when thinking about bites are Eikenella in human bites and Pasturella in animal bites (especially cat bites).

Amox-clav is a fairly good choice for bites (of both the human and animal variety) but you need to remember that if the bite if say, on the ear, you’ll also need coverage for pseudomonas. To make matters a little more confusing Eikenella is resistant to clindamycin, macrolides, metronidazole, and fluoroquinolones. So if the bitten person is allergic to penicillins, clindamycin just won’t do.

Hypersensitivities (type I, II, III, IV, V)

The types of hypersensitivities can get a little confusing, especially 2, 3, and 5.

Type 1: Plain old allergy (asthma, anaphylaxis, atopy)
Type 2: Antibody-dependent, cytotoxic (think of autoimmune hemolytic anemia)
Type 3: Immune complex disease (like a lot of the autoimmune conditions: rheumatoid, lupus)
Type 4: Delayed/Cell-Mediated (mediated by T cells, T cells are slower to react than antibodies, so this reaction takes a couple days)
Type 5: Receptor-mediated autoimmune disease (Graves, myasthenia gravis)

Patent ductus arteriosus

Normal fetal circulation

The ductus arteriosus is a connection between the aorta and pulmonary artery present in the fetal circulation. Since the pulmonary vascular pressure is higher than the systemic pressure, blood is shunted through the ductus from the right to the left, bypassing the lungs.

 

When the baby is born, the resistance in the pulmonary vascular falls and more of the blood goes through the lungs. In conjunction with this the fall in the level of circulating prostaglandins causes the contraction of the ductus arteriosus.

Patent ductus arteriosus

In some babies, particularly those born prematurely, the ductus fails to close and the shunt becomes left to right.

This gives you the classic “continuous machine-like murmur

Insulin Regimens and Dosing

Insulin dosing has to be one of the most (seemingly) unnecessarily complicated dosings in medicine. Not only are there 4 ways to dose it (BID, QID with rapid, QID with fast, QID with extended-release) there are three different companies, all naming their insulins slightly differently. But how can you remember whether to give Humalog, Humulin N, Humulin R, NovoRapid, Novolin Toronto, NPH, Lantus, or some combination of the above?

This is a master illustration to help organize insulin dosing and amounts.

Total Daily Dose

0.3 – 0.6 units/kg
Start low, titrate up

BID (conventional therapy)

2/3 : 1/3 rule
2/3 breakfast : 1/3 supper
2/3 long : 1/3 fast

QID (with either Rapid or Fast-acting and either long or extended)

Breakfast: 20-25% long, 15-20% rapid
Lunch: 15-20% rapid
Supper: 15-20% rapid
Bedtime: 25-30% long

Pulmonary function test patterns

Same old pulmonary function tests (PFTs) that we’ve all probably memorized countless times. The only thing to remember that is a little odd is that you can get a restrictive type pattern of the FEV1/FVC ratio (but not quite the perfect flow loop) if you have air trapping in COPD.

Placenta Previa

Placenta previa isn’t generally something that is a concern in the western world, since prenatal ultrasounds are common practice, but in areas of the world where they’re not, it can be pretty devastating when the baby is being delivered.

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