Category: Nuggets of Knowledge

Nuggets of Knowledge – when is Pneumocystis pneumonia prophylaxis warranted in a non-HIV infected patient?

I notice that quite a few of the patients I have encountered so far in Clinical Orientation and my 1st patient on my Oncology rotation are on SMX/TMP for PCP prophylaxis. It begged the question: when is it warranted? According to this meta-analysis, if the risk is >6%, you give prophylaxis. Which conditions warrant this type of risk? Should all cancer patients receive it?

– Cancer patients who SHOULD receive PCP prophylaxis: HL, NHL, brain tumours, myelodysplasia, ALL, lymphoproliferative dz, or myeloma, relapsed dz, “high-dose” corticosteroids, or R-CHOP-14 regimen
– Treatment with 20 or more mg prednisone equivalent for 1 month or more
– Alemtuzumab or temozolomide recipients
– Allogenic and select autologous (w/purine analogue conditioning Tx) HCT recipients
– Solid organ transplant recipients

There are a few SMX/TMP regimens… DS tab daily, DS tab qMWF, SS tab daily… there isn’t much direction to choose one. There was an RCT in HIV-infected patients that wasn’t statistically significant for daily SMX/TMP, but there was roughly 2x more discontinuation due to ADRs from the daily group.

I’ve personally seen DS tab qMWF most but it all depends on patient-specific factors such as adherence and recent lab work!

Nuggets of Knowledge – July 31st hodge podge: warfarin bridging, lumbar puncture findings, and ID tidbits

When to NOT bridge warfarin with LMWH following a procedure (low risk)
– Laprascopic surgery
– Dermatologic procedures
– Ophthalmologic procedures
– Colonoscopies
– Bone marrow aspirate and biopsy, lumbar punctures
– Thoracentesis

CSF findings that would raise suspicion of viral encephalitis (not meningitis)
– Increased WBC but <250/mL
– Increased protein but <150 mg/dL
– Normal glucose (decreased with herpes simplex)
– RBC usually absent, but positive in HSV-1 or if contaminants present

Gram-negative bacilli may be divided into fermenters and non-fermenters.
Fermenters can be found in GI/GU: 
E. coli, Proteus mirabilis, Klebsiella spp.
Non-fermenters (skin, resp, GU): Pseudomonas aeruginosa, Acinetobacter spp., Legionella pneumophila

Acinetobacter susceptibilities follow Pseudomonas susceptibilities closely!

And while I’m at it..
Gram-negative cocci
– Neisseria gonorrhoeae
– Neisseria meningitidis
– Moraxella catarrhalis
– Haemophilus influenzae

Nuggets of Knowledge: Causes of elevated lactate, and some pearls on myelodysplastic syndromes

Some causes of an elevated lactate include:
– Decreased renal function
– Comorbid liver disease
– Decreased tissue perfusion, hemodynamic instability (like sepsis)
– Active alcohol abuse
– Decompensated HF
– Hypoxic state

Myelodysplastic syndromes – risk and prognosis measured by DIPSS score, taking into account (one point each): age >65 yo, leukocytes >25, Plts <100, required transfusion, circulating blasts 1% or above, unfavourable karyotype, fever/sweats/wt loss preceding Dx. High risk DIPSS is for a score of 3 or above.
– DIPSS factors into decision making for drug therapy. High risk = allogenic HCT is favoured. Low risk = symptomatic care such as DNA hypomethylating agents, transfusion, G-CSF, or darbepoeitin may be favoured.
– Iron chelation therapy post-transfusion initiated if ferritin is constantly elevated >1000, AND pt is stable (no comorbid infections), DIPSS low risk (0-1) may favour iron chelation.

Nuggets of Knowledge – Intro to Infectious Diseases

Few tidbits from the ADS on ID.

  • Presence of polymorphonuclear cells (PMNs) indicates inflammation
  • Beware of epithelial cell contamination in a sample
  • Coagulase-negative Staphylococcus spp is often a contaminant of blood cultures
  • A C&S will NEVER have PO susceptibility data due to concerns with bioavailability. Consult microbiology if you need direction.
  • Eosinophilia increases suspicion of allergic reactions or parasitic infections
  • Lymphocytosis increases suspicion of malignancy or bacterial infections
  • Acute phase reactants are non-specific but add to the overall picture
  • Pearl: cellulitis treated with ABX will appear to worsen for 2-3 days due to killing of bacteria and subsequent release of endotoxins
  • Some antibiotics perform poorly in acidic environments, so therefore will not penetrate and treat an abscess.
  • When do you consult microbiology?
    • Need more specific identification on an organism
    • Need additional susceptibility or MIC data
    • Need guidance on which test to use to identify a bug

And of course, this fun gem:

10commandmentsID

Vancomycin tapering for C. difficile

I found this one to be interesting, and involved some digging into EMR. The patient was in for C. difficile associated diarrhea (CDAD), and was the first instance that I could see on Meditech (since 2010 at least), and was on vancomycin 125 mg PO QID since the 28th (closing in on one week). The order read as follows:

vancomycin 125 mg PO TID x 2 days (starting Jul 5th) then
vancomycin 125 mg PO BID x 3 days then
vancomycin 125 mg PO daily x 2 days then stop.

Immediately I thought that I better look into it as I was unfamiliar with taper regimens for PO vancomycin. What I found was that there really is not that much evidence to support taper regimens despite it appearing on UpToDate and some clinical guidelines, and taper regimens are only recommended under guidelines for the 2nd recurrence. In addition, it was the patient’s first bout with C. difficile as far as we knew; in that case what is recommended is either metronidazole 500 mg PO TID or vancomycin 125 mg PO QID x 14 days, if severe (see the paper above for more details). I decided to write it in the clinical book that the pharmacy had, describing my concerns so that the clinical pharmacist could reassess and follow up. It was a good opportunity to delve a bit deeper into an order and try and make an intervention from the dispensary.

QTc prolongation + Torsades de Pointes risk stratification and management

For this Nugget of Knowledge, I put several tags on it because I think I will be referring to it on multiple rotations…I just picked the ones that I suspect it will come in most handy.

Probably not the first thing that comes to mind when one thinks about drug distribution, but always a thing to keep in mind on a dispensary shift if a patient is on a bunch of QT prolonging drugs – how do you know who is at higher risk than another? Today I attended a CSHP webinar on this very topic; here are some pearls I picked up:

FDA and Health Canada definition of a prolonged QTc
>500 ms OR >60 ms above baseline

Beware of the hypos – K, Mg, and Ca

Risk stratification tool #1 – Tisdale et al – validated in cardiac critical care units
– Assigns varying point values to different risk factors
– Offending DRUGS are given more weight than say, hypokalemia
– Great positive predictive value for high risk individuals
– They did not routinely measure magnesium levels
– However, only predicts risk of prolonged QT, NOT TdP or any hard outcomes such as mortality.

Risk stratification tool #2 – Haugaa et al with the Mayo Clinic – not validated, but had patients across the board: peds, medicine, cardiology, ICU, you name it
– EQUAL weighing of risk factors
– Hard outcome: mortality
– Good predictive value of mortality for scores 4 or above
– ONLY valid for baseline QTc of 500 ms or greater

These tools are great for stratifying patients according to risk and will help me prioritize interventions. As always I would perform NESA on each offending drug (or each option to treat a condition) to see if it is worth the risk. Also, downloaded the CredibleMeds app onto my phone – a great tool to quickly look up rough risk levels for various medications to prolong the QT interval.