Diving and diuretics. Because it comes up from time to time.+

[DocVikingo]

Diuretics, sometimes called “water pills,” remove sodium and water from the body. Used either alone (e.g., furosemide (Lasix), hydrochlorothiazide (Hydrodiuril)) or in combination with another agent (e.g., propranolol+hydrochlorothiazide (Inderide), atenolol+chlorthalidone (Tenormin Plus)), they are the most common, and often among the first, drugs prescribed for the control of high blood pressure. They are prescribed for other conditions as well, such as congestive heart failure and tissue swelling, and occasionally for vertigo, osteoporosis and other disorders.

Interestingly, in a study of medications taken by divers who later received care at a hyperbaric facility ("Drugs Downed Divers Did"; Undersea and Hyperbaric Medical Society, Inc. Annual Scientific Meeting held June 14-16, 2007), antihypertensives were the second most frequently reported: "RESULTS: Two hundred seventy-eight cases had been treated within the study period of which 92 (33%) had been using at least one drug at the time of accident.

Table 1. Number and percent cases by drug category (n=278)

Drug category/Number of cases/Percent of cases

Psychotherapeutics 28 10%
Antihypertensives 25 8.9%
NSAIDS 24 8.6% ...."

The diver taking a diuretic should consider several issues.

During SCUBA, inert gas (e.g., nitrogen) released from tissues upon ascent may block blood circulation and cause mechanical distortion of blood vessels and nerves. And areas of nervous system tissue that have been subject to such ischemia or trauma may remain sensitive to reduced blood flow/oxygen delivery for some period of time. By their very nature, diuretics of all types tend to reduce plasma volume and increase blood viscosity, and the potential implication of this for DCS is obvious.

Certain diuretics may result in excessive loss of blood potassium. This condition may cause numbness or tingling in the feet and weakness and a sensation of heaviness in the lower extremities, amongst other signs and symptoms. Certain drugs of this type also can have lower back or side pain as an unusual side effect. It is important not to misidentify these as the result of the drug when DCS is the cause (and vice-versa). This is not always an easy distinction.

There are classes of antihypertensives that do not pose the above discussed issues and the diver may wish to explore these with his or her treating physician.

If a diuretic still appears to be a treatment of choice, it might be worth investigating a "potassium-sparing" type, meaning they do not cause the body to lose potassium. Potassium-sparing diuretics include spironolactone (Aldactone), miloride (Midamor) and triamterene (Dyrenium).

Clearly the diver using a diuretic must take extra care to remain properly hydrated. In this regard, it may be prudent to discontinue the drug during tropical dive outings, with doctor clearance, of course. Diving medicine expert Dr. Fred Bove says: "Diuretics -- These drugs are used to eliminate water and excess salt (sodium) from the body. They act by allowing more water to pass through the kidneys to form urine. Divers will have little effect from the diuretics. In hot environments, where fluid can be lost from sweating, the diuretics can cause excess water loss. If you are exposed to heat and are sweating, the diuretic may not be needed. Diuretics will also cause loss of potassium, an important mineral in the body. It is best to skip your diuretic on a diving day."

Regards,

DocVikingo

This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual, and should not be construed as such.

 

[TSandM]

The statistics on how many divers in chambers are on diuretics would only be useful if we knew how many of the untreated diving population were on such meds. Since hypertension is extremely common, especially in the age demographic which leads in diving these days, I wouldn't be at all surprised if close to 9 percent of the diving population were on those medications, in which case they would not be overly represented in the DCS cases.

Although excessive volume loss and electrolyte disturbances can occur with diuretics (more with the loop diuretics like Lasix than with the thiazides, which are more commonly prescribed for hypertension) they are more likely to occur immediately after institution of the drug, or with dosage changes. As with any medication, one should not start diuretics and dive immediately, but allow some days (or in this case, probably better a couple of weeks) to see what the effects of the medicine are in your particular case.

Although there is certainly a theoretical increase in risk of DCS with diuretics, due to their volume contraction effect, DAN states that they are generally well tolerated in divers, and I believe they have considerably more data than we have.

 

[DocVikingo]

Hi TSandM,

Good points and on balance I agree.

RE:

Although there is certainly a theoretical increase in risk of DCS with diuretics, due to their volume contraction effect, DAN states that they are generally well tolerated in divers, and I believe they have considerably more data than we have.

Indeed DAN’s stated position (DAN Divers Alert Network -- Diuretics (water pills- HCTZ, Aldactone, Bumex)) essentially repeats that of Dr. Bove as quoted in my post (“Divers will have little effect from the diuretics….). Nevertheless, both DAN and Bove mention that when diving in very warm environments a diver may wish to consider a reduction in dosage or even skipping doses on diving days.

Moreover, DAN and many other professional sources frequently caution about the use of substances with a known diuretic effect such as alcohol, regular tea and regular coffee during dive outings. Personally, except in cases of very gross abuse I think this is unsupported as the diuretic effect of such drinks is minuscule and even factoring in this effect there is a net gain in water. In any case, the fact is both loop diuretics and thiazides have a far, far greater potency in reducing plasma volume and causing electrolyte disturbances than do caffeinated and alcoholic beverages about which divers routinely are cautioned.

IMHO, the issue of diving on diuretics remains worthy of discussion. I recently had dealings with a diver who was being treated with Lasix (furosemide) for vertigo and clearly had significant DCS-like events related to it.

Regards,

DocVikingo

 

[TSandM]

I totally agree about the caffeinated drinks, but alcohol does some nasty things to free water balance, and I have seen some surprising electrolyte disturbances in people after heavy drinking. Alcohol also falls into the category of substances you aren't taking regularly, and therefore haven't adapted to (for most people, anyway!)