Beta Blockers and Pulmonary Edema Risk

[Duke Dive Medicine]

Hi jsex,

I agree that a bit caution is not a bad thing, but think that near hysteria over the issue is.

Happily, control of hypertension has a veritable luxury of treatment possibilities. Along with the customary & healthful behavioral approaches (e.g., smoking cessation, weight reduction, regular exercise, salt restriction, stress management, going easy on alcoholic beverages), there is a huge number of choices of medications aside from beta-blockers that may be considered, including diuretics, ACE inhibitors, angiotensin II receptor blockers, calcium channel blockers, alpha blockers, alpha-2 receptor agonists, peripheral adrenergic inhibitors and vasodilators, some of which can be used in combination. While most divers tolerate moderate doses of beta-blockers well, DAN recommends ACE (angiotensin converting enzyme) as the preferred class of drug for treating hypertensive divers (e.g., benazepril (Lotensin), captopril (Capoten), enalapril (Vasotec), fosinopril (Monopril), lisinopril (Prinivil, Zestri), ramipril (Altace)).

I’d like DDM to speak to the IPE v PE distinction he intends, but my take on his remark is that one should differentiate between PE that has immersion as its primary cause versus PE that has another primary cause, but just happens to occur while the individual is submerged (e.g., cardiac arrhythmia, fluid overload secondary to kidney dysfunction, upper airway obstruction, aspiration of seawater or gastric fluid, pulmonary contusion).

Regards,

DocVikingo

Great post Doc.

Re IPE: When the body is immersed, the effect of gravity on blood distribution is neutralized. This results in a redistribution of slightly more than half a liter of blood to the torso. Cold water causes peripheral vasoconstriction, which enhances this effect. There is a subset of the population whose pulmonary arteries apparently fail to dilate in response to this redistribution of blood. Let's call them non-dilators. When an influx of blood hits the pulmonary arteries in these non-dilators, the pulmonary artery (PA) pressure goes up, which in turn can result in pulmonary edema. We've been studying this for a couple of years. Our primary subjects are triathletes and military combat divers, whose cardiac outputs are extremely high. High cardiac output can further increase the PA pressure, which subsequently increases the risk of pulmonary edema in non-dilators. This is what I'd describe as "pure" IPE.

On the other hand, if someone's cardiac output is already compromised, e.g. from heart failure, the heart may not be able to handle the immersion-related blood redistribution - the blood can effectively back up in the lungs because the heart can't pump it out quickly enough, which again results in pulmonary edema, but the mechanism is entirely different. This is where the hoopla over diving on beta blockers originates – the potential to lower the heart rate and thus the cardiac output, which could theoretically cause blood to back up in the lungs and lead to pulmonary edema. However, the cardiac output in people who take beta blockers over a long period of time tends to recover in the form of increased stroke volume (i.e. the amount of blood that the heart puts out with one beat). Again though, the question of diving and beta blockers would be best answered with another question, which is, what’s the underlying medical condition for which the individual is taking the medication, and is that medical condition compatible with diving?

Best regards,
DDM

---------- Post added December 13th, 2013 at 12:47 PM ----------

I found it incredibly interesting. I am on beta blockers for the past 6 months, but not for hypertension. I developed post-operative a-fib and also tend to throw a lot of PVCs. In general, I have a somewhat irritable heart. My cardiologist put me on the beta blocker while things cleared up and has been fighting my desire to get off it because she thinks it is having a good effect on my heart function. Here's the kicker. She knows I'm a diver, knows some diving medicine, and used to work with Fred Bove, author of Diving Medicine and the physician quoted in the DAN article. So why is she insisting that I stay on it and not concerned at all about my tech diving?

That question can't be answered without more information about your condition. You said you developed post-operative a-fib... what was the surgery for, and why exactly are you seeing a cardiologist who is concerned about your heart function?

Best regards,
DDM

 

[jsex]

Thanks for that in-depth answer DDM! That makes a bit of the physiology behind a PE a little more clear to peeps like me.

I agree that a big question is what is the underlying condition of the divers. I have seen too many divers who had no business in the water due to their lack of condition, excessive over weight and apparent lack of desire to do anything about either...

 

[TSandM]

Again, jsex, I caution that correlation does not imply causation. And, as DDM has observed, without knowing the indication for a beta blocker, one can not even infer much about what is going on with these patients. The person on metoprolol for uncomplicated Afib with a structurally normal heart is a different patient from the one with severe, refractory hypertension requiring multiple medications, or the person who is on beta blockers for coronary artery disease. And the person taking them for migraine prophylaxis may be an entirely different patient altogether.

I definitely do not think we have enough evidence at all to recommend against diving in the second half of life, on beta blockers or not. But I think a patient with coronary artery disease or refractory hypertension may want to rethink his risk assessment regarding diving, either at all, or in respect to what types of dives he does.

 

[jsex]

I understand your points, TSandM, but do not agree with not letting folks who have to work with divers know about something they are unaware of. Too many divers take their physical and medical conditions way to lightly. In the field working, I was faced with the consequences of that laissez-faire attitude more than once and it almost cost a life then as well. If one person is better prepared to handle an emergency because he/she noticed something associated with this discussion, then I am a happy person. This is the reason I wrote it up in the first place and emphasized points for others to be aware of.

 

[diving4ever]

I understand your points, TSandM, but do not agree with not letting folks who have to work with divers know about something they are unaware of. Too many divers take their physical and medical conditions way to lightly. In the field working, I was faced with the consequences of that laissez-faire attitude more than once and it almost cost a life then as well. If one person is better prepared to handle an emergency because he/she noticed something associated with this discussion, then I am a happy person. This is the reason I wrote it up in the first place and emphasized points for others to be aware of.

First, I want to thank the Docs who weighed in. I found it very helpful.

I'll just add that when we talk about sharing un-proven anecdotal medical information, its important to note that wrong information can be as hurtful as no information. Part of the reason is because that type of health info is often presented with a great deal of editorial flair. We've all done it. The OP wrote "I received a scary message from a diving friend recently. One that sent chills down my spine and thoughts racing through my brain." While that may be true, it isn't helpful and it makes it harder for the reader to effectively reason the issue out. What we might reasonably want from an observation of correlation is for the dive medicine community to respond or research (if necessary). What we don't want is to spook divers, especially if it encourages divers to go off medications they need, give up a form of exercise they enjoy, or be misinformed about the risks of diving.

We've seen a lot of high profile correlations that didn't pan out. Vaccines and autism / antiperspirant and Alzheimer / Vitamin C and the common cold cure / sugar and hyperactivity / cold weather and colds etc. People got the word about these correlations loud and clear--largely because the brain is giant pattern recognition machine. But science has since called bulls@#t on all of it, but the ideas persist. Just something to think about.

Remember:
Correlation does not imply causation, but it does waggle its eyebrows suggestively and gesture furtively while mouthing "look over there."
—xkcd

 

[flots am]

I definitely do not think we have enough evidence at all to recommend against diving in the second half of life, on beta blockers or not. But I think a patient with coronary artery disease or refractory hypertension may want to rethink his risk assessment regarding diving, either at all, or in respect to what types of dives he does.

I always thought "Diving for older folks" would be a nice specialty class. It could cover things like getting out of the water without injury, how to flip off the DM when he wants to swim into the current, and shooting an SMB for boat pickup if you get blown off the dive site.

Extrordinary physical exertion can often be replaced with a little planning and judgement.

flots.

 

[kwinter]

That question can't be answered without more information about your condition. You said you developed post-operative a-fib... what was the surgery for, and why exactly are you seeing a cardiologist who is concerned about your heart function?

Best regards,
DDM

PM sent to avoid thread hijack.

 

[tomfcrist]

This theory doesn't surprise me at all. I have noticed a correlation between undeserved dcs hits and scopolamine over the years, at least in the cases that I have witnessed, nearly all of them were wearing the patch. Could be coincidence, but more research int the effects of these receptor antagonists on divers would be nice.

 

[Hatul]

Don't know about the relationship of immersion pulm edema and beta blockers, but there are beta blockers and beta blockers. As an anesthesiologist I see too many people on high dose beta blockers unnecessarily. Usually it's for hypertension, and the dose is to the point of severely limiting the heart rate response to exertion and/or bradycardia at rest. There are not many conditions that justify the use of high does beta blockers, and it's not a good choice as the first line drug for hypertension. They limit your ability to exercise and likely cause weight gain as well. Some of the older studies that showed protection from high dose beta blockers and surgery were found to be fraudulent and the latest show they do more harm than good.

Low dose beta blockers are a different story. They can synergystically lower the blood pressure with other meds, are protective against dangerous tachycardias and dysrhythmias, and are even useful in heart failure. I think low dose beta blockers, that maintain normal resting heart rate and allow an increase in heart rate response to exercise, should be fine for diving and may even be protective.