Vaprisol (Conivaptan) -- a Treatment for Hyponatremia (Low Blood Sodium)

Vaprisol is a newly released drug treatment for low sodium in the blood (also called "hyponatremia").

First, some background. Hyponatremia is a medical condition that can have many possible causes. For various reasons, the body retains too much water and the blood sodium is diluted. Some causes of hyponatremia include losing body fluids (from vomiting, diarrhea, or from diuretics); an abnormally high level of antidiuretic hormone, also called vasopressin (related to medical problems like strokes or lung cancer); and other conditions like cirrhosis, congestive heart failure, and protein in the urine.

Hyponatremia can sometimes lead to swelling in the brain, which in some cases can cause confusion, seizures, and death. For an analysis of the case of Jennifer Strange, a radio show contestant who died from hyponatremia after drinking too much water, see here.

Vaprisol has been approved to treat hyponatremia related to conditions in which the body has not lost body fluid. It is not indicated for conditions like vomiting, in which the body's fluid is low.

Here's how it works. Usually, a gland in the brain called the pituitary released antidiurtic hormone (vasopressin) in response to a high concentration of sodium in the blood serum. More vasopressin causes the kidneys to retain more water, which causes the blood sodium to go down as the extra sodium is diluted by more water. In many cases of hyponatremia, the level of vasopressin is abnormally high and the body therefore retains too much water, driving the sodium level down.

Vaprisol is an intravenous medication which blocks the effect of vasopressin on the kidney. It's usually given as a bolus of 20 mg followed by a slow infusion. By blocking the effects of vasopressin, vaprisol causes the kidney to eliminate water (a "water diuresis"). This eventually causes the serum sodium to go up as the blood sodium becomes less diluted.

Cardiologists are also interested in the possible future use of Vaprisol to treat low sodium related to congestive heart failure, but it is not yet approved for this indication.

Labels: conivaptan, hyponatremia, nephrology, vaprisol

Permalink | 1 Comments| Email Post

Post your comment

HydraCoach: An Intelligent Water Bottle

Drinking enough water is difficult. Exactly how much water people need is debatable (here's a sample calculator), but most people probably aren't drinking enough. Typically, the usual recommendation is 8 ounces of water 8 times a day.

And for people in hot environments and with certain medical conditions, like kidney stones, drinking enough water is critical. To dilute their urine and prevent future stones from forming, people with kidney stones should drink enough water to produce at least 2.5 liters of urine a day -- at least 24-32 ounces three times a day. "You know those people who walk around with water bottles all day?" I tell my patients. "You should become one of those people."

But of course, it's tough to carry around water all the time, it's tough to know how much you've drank, and it's tough to remember to drink that much water.

The HydraCoach is a newly-created "intelligent water bottle" that is designed to calculate daily fluid requirements, monitor how much you drink, and encourage you to drink more water. It's such an obvious idea that I wondered why it hadn't been created before. From the website:

The HydraCoach hydration monitor functions by means of Generated Electronic Pulse technology. A magnetized impeller floating within a sealed cartridge is placed in-line with the path of fluid, and in close proximity to a sensor located within the head unit. When the flow of liquid comes in contact with the impeller, it begins to rotate, causing the equi-spaced magnetic elements embedded within to pass the sensor, generating a small electronic pulse. This pulse is transmitted to the microprocessor where a measurement of fluid volume is calculated. The volume of fluid is directly related to the rate at which the impeller spins and these pulses generated. The amount of fluid passing through the system is shown on the display. The interactive head unit features several buttons that allow the user to toggle between various informative function modes and to input customized settings.

I've not tried the Hydracoach personally, but considering the importance of hydration in preventing kidney stones, the next time someone complains that they can't remember to drink enough water, I'll be recommending this device. (It costs $29.95, and if it can help a person prevent even one kidney stone, I think it's worth it.)

Labels: hydracoach, kidney stones, nephrology

Permalink | 4 Comments| Email Post

Post your comment

Aquapheresis: A New Treatment for Heart Failure (Part 1)

Congestive heart failure (CHF) is a condition where the heart's pumping of blood is inadequate and consequently, fluid builds up in the lungs. (As a nod to my readers who are cardiologists -- CHF has many causes and is much more complicated that this simple explanation.) Symptoms of heart failure can include shortness of breath, low blood pressure, and a lack of blood flow to other organs of the body, like the kidneys.

Ninety percent of hospitalizations for congestive heart failure are due to shortness of breath from fluid overload. In patients with CHF, the major treatment for fluid overload has classically been diuretics injected intravenously. There are many types of diuretics, but Lasix (furosemide), is the one most commonly used.

The use of diuretics, while often quite effective, has many potential problems. First, an inadequate dose may be given, which may require a longer course of hospitalization until titration to the proper dose is achieved. Second, the patient may respond too well to the diuretic (a condition called "overdiuresis"), which can lead to low blood pressure and decreased kidney function. Third, even if the proper dose is given, diuretics may occasionally still lead to decreased kidney function and other complications, like low potassium.

For patients with congestive failure who already have significantly decreased kidney function, an alternative to diuretics is a process called "ultrafiltration." During dialysis -- a way of cleaning and filtering the blood using a dialysis machine -- fluid may be removed from the blood directly. In patients with CHF, ultrafiltration of extra fluid, which is performed during dialysis, can relieve symptoms of shortness of breath the same way diuretics can. The downside is that ultrafiltration requires a dialysis machine and is usually only used in patients with decreased kidney function.

In an attempt to overcome the problems with diuretics and the requirement of a dialysis machine for ultrafiltration, a company called CHF solutions has designed a device for ultrafiltration -- which they call "aquapheresis" -- called the AquaDex FlexFlow Fluid Removal System. A recently published study called the UNLOAD trial has shown impressive results in using the machine to treat patients with heart failure.

More in Part 2.

Labels: aquadex, aquapheresis, cardiology, chf solutions, congestive heart failure, heart failure, nephrology

Permalink | 2 Comments| Email Post

Post your comment