Tag: sodium

Posted on

Its not the sodium intake its the sodium:potassium ratio

Don’t worry only about sodium intake (NYC, I’m looking at you) and its not just potassium intake (DASH diet in the cross-hairs). It’s all about the sodium potassium ratio. This is shown by Cook et al (PDF). during reanalysis of the Trial of Hypertension Prevention I and II. This trial had serial 24-hour urine collections done in 2,275 patients with pre-hypertension in the late 80’s and 90’s. The investigators looked at that data through the lens of 15 years of follow-up to determine the risk of cadiovascular events:

In observational analyses of the mean urinary excretion during 11⁄2 to 3 years, we found a suggested positive relationship of urinary sodium excretion and a suggested inverse relationship of urinary potassium excretion with risk of CVD, but neither was statistically significant when considered separately. Both measures strengthened when modeled jointly, with opposite but similar effects on risk. However, the sodium to potassium excretion ratio displayed the strongest and statistically significant association, with a 24% increase in risk per unit of the ratio that was similar for CHD and stroke and was consistent across subgroups.

Here is the key figure. Note in the graph the rate of events is presented on a log scale so the 2 indicates a rate 100 times the rate at zero.

Posted on

Teaching Medical Students


Last Friday I started teaching third year medical students. This is the first time I have taught medical students (in isolation, there are always medical students at my lectures for the residents) since 2003, when I ran a teaching section for renal physiology for first year medical students at Pritzker School of Medicine, University of Chicago with John Asplin.

I am now teaching the medical students two lectures every rotation, the first on sodium and the second on potassium and calcium. I hope to expand this to ABGs and another electrolyte lecture so I can isolate potassium and spend an entire hour on it.

I modified my Don’t Panic handout for the students. During the lecture I realized that the SIADH section was weak and too complex for the students. I will probably change it to focus on the fact that ADH reduces water excretion and that this can be adaptive (early CHF, volume depletion, hyperosmolar) or maladaptive (SIADH). I will change the section on the dilution of urine to a background box as I think it is important but only interesting to nephrologists and similar wierdos.

I will add a focus on a few clinical scenarios with increased ADH.

I still need to expand the hypernatremia section.

Handout
iPhone version

Posted on

Sodium and Potassium for ER residents


Yesterday I lectured the St John ER residency program. The ER residency has an impressive commitment to education. They set aside a half day every wednesday for their resident to get dedicated didactic time. They have great attendance with a good number of attendings showing up.

I have been asked to give three lectures and yesterday was the first. I gave a double lecture (running time about 90 minutes) on sodium and potassium. The fact that I could run over the standard 50 minute alotment normally given for medicial education is due to the fact that they have blocked an entire afternoon rather than try to shoehorn a lecture into lunch or before rounds.

The sodium lecture was the first time I used the Sodium handout I created for the St John IM residents. I gave the lectuer Seder-Style with the residents reading different sections, answering questions and me adding commentary. The ER residents are smart and empowered to ask questions. I felt that there was great two-way interactivity.

Dont Panic Sodium

Sodium iPhone format
Sodium booklet format

The potassium lectuer is an abrdged potassium lecture which is stripped to the bare bones of differential and treatment. It is a traditional powerpoint lecture. Immediately when I started this lectuer I saw about half a dozen exhausted interns fall asleep. My next project is to create a potassium haggadah.

Potassium powerpoint

Posted on

July first lecture on IVF, Diuretics and dysnatremia


Today I gave the first lecture of the ’08-’09 Academic Year. This was morning report for internal medicine. I did a lecture on IVF, diuretics, total body water and dysnatremia. It was a good lecture but Powerpoint only. I am about half-way done with the killer handout I am working on and am disapointed that I didn’t finish it. Hopefully will have it done for the next lecture in two weeks.

Fluids And Electrolytes July1

View SlideShare presentation or Upload your own. (tags: diuretics sodium)
Posted on

Hyponatremia and Marathons

I love it when some of the arcane nephrology knowledge makes headlines. When I heard NPR covering hyponatremia I almost cried. I am training for a half marathon in October and so I have been thinking about this topic.

Almond, Et al’s study published in the NEJM looked at 488 blood samples from 766 runners recruited from the 2002 Boston Marathon. They found post-race:

  • Average sodium 140±5 mmol/L
  • 13% had a sodium <>
    • 22% of woman
    • 8% of men
  • 3 runners had Na <>

When they looked at predictors of hyponatremia, univariate predictors included:

  • Female gender (p<0.001)
  • Lower BMI
  • Fewer prior marathons (p=0.008)
  • Slower training pace (p<0.001)
  • Longer race duration (p<0.001)
  • Hydration frequency (p<0.001)
  • Hydration volume (p=0.01)
  • Urination during the race (with more frequent voiding having a higher risk of hyponatremia) (p=0.047)
  • Weight gain during the race (p<0.001)

Of note use of sport drinks compared to pure water made no difference. In the multivariate analysis, hyponatremia was associated with:

  • weight gain
  • longer racing time
  • body-mass index of less than 20

Of note the female gender falls out in the multivariate analysis as it likely was accounted for both by the longer running time and lower BMI.

In the discussion the authors mention that most sport drinks have only 18 mmol/L of Na.