71 / 116
who are at elevated risk of a stroke or heart attack). The
U.S. Preventive Services Task Force recently reviewed
the available evidence and recommended aspirin for
use by certain “at-risk” individuals over age 50 following
consultation with their primary care provider.
3
Given the
aging population of divers in the U.S., this could affect
many divers.
In some hyperbaric treatment facilities, aspirin
is prescribed as an adjunct to hyperbaric therapy
based on the hypothesis that it will “thin” the blood
and increase offgassing, thus increasing the efficacy
of hyperbaric oxygen therapy (HBOT).
4
Although
this sounds prudent, the evidence supporting its
prescription is controversial; what are needed next
are randomized clinical trials in which some patients
receive aspirin and others do not. Until then we will
not know for sure if aspirin is beneficial in HBOT.
Taking it before diving, however, is another matter.
In terms of regular predive administration, such as
in divers who take an aspirin a day, this is a vexing
question, so I turn to my colleague in medicine to
describe some potential considerations.
— Peter Buzzacott, MPH, Ph.D.,
DAN Director of Injury Monitoring and Prevention
As mentioned previously, even the decision to take
aspirin on a daily basis is not clear-cut. You must
discuss with your physician the risks and benefits of
taking this remarkable and inexpensive medication.
Even with a large body of evidence supporting
aspirin use in the prevention of cardiovascular
disease and some cancers, the risk of gastrointestinal
and intracranial bleeding moderates its universal
prescription for those it might benefit.
Introducing your desire to dive into the discussion
may have an impact on the decision for you to take
low-dose aspirin on a daily basis. I will primarily
discuss the effects of its anticlotting function since this
has the main impact on divers. In the future, research
may prove its anticancer effects, and this may also have
a direct impact on the diver.
Aspirin is a potent medication that has antithrombotic
effects by affecting platelet function. Platelets play an
important role in the clotting function. This effect can
be seen with low doses of aspirin (baby aspirin) and
is supported by multiple studies. The analgesic effects
of aspirin appear to require higher doses to achieve
analgesia by yet a different cellular pathway with an
associated increase in bleeding risk.
The same bleeding risks (gastrointestinal, intracranial,
etc.) for the general population affect divers in even
more locations in the body. The problem for divers
is that this antithrombotic or anticlotting effect can
have negative effects when impacted by a diving injury
from barotrauma and possibly severe neurologic
decompression illness (DCI).
Bleeding from trauma that includes injuries from
barotrauma may experience increased bleeding. This
may occur with middle-ear or sinus barotrauma
(squeeze). These areas do not allow easy access to
control such bleeding.
A concern by many diving medicine experts is that
with serious neurologic DCI, hemorrhage or bleeding
has been seen in sensitive neurologic tissue. With
aspirin-induced anticoagulation, this bleeding may take
on increased significance for both treatment response
and long-term outcome.
Nonsteroidal medications, which share some of
the same mechanisms of action as aspirin, have
been used in conjunction with the hyperbaric
treatment of DCI. Those investigators reported
some benefit in the number of hyperbaric treatments
required. Some benefit of its analgesic properties may
account for this. Unfortunately, this effect will probably
not be seen with low-dose aspirin since the cellular
pathway producing this analgesia is minimally affected.
In addition to the discussion of studies that outline
the risks and benefits of low-dose aspirin for the
general population, divers must also consider with
their physician concerns over increased bleeding in the
event of barotrauma or decompression injury. If taking
low-dose aspirin, divers should pay strict attention to
the ability to equalize, have no evidence of congestion
or upper-respiratory illness and employ conservative
measures to prevent DCI.
AD
— Jim Chimiak, M.D.,
DAN Medical Director
ALERTDIVER.COM|
69
References
1. Lambrechts K, Pontier JM, Mazur A, Theron M, Buzzacott P, Wang Q, et al. Mechanism of action of antiplatelet drugs on decompression sickness in
rats: a protective effect of anti-GPIIbIIIa therapy. J Appl Physiol. 2015; 118(10):1234-9.
2. Kux L. Citizen petition denial response from FDA to Bayer Healthcare LLC. Rockville, Md.: FDA; May 2, 2014. Available at:
http://www.regulations.gov/document?D=FDA-1977-N-0018-0101. Accessed Sept. 21, 2016.
3. Whitlock EP, Burda BU, Williams SB, Guirguis-Blake JM, Evans CV. Bleeding risks with aspirin use for primary prevention in adults: a systematic review
for the U.S. Preventive Services Task Force. Ann Intern Med. 2016; 164(12):826-35.
4. Bessereau J, Coulange M, Genotelle N, Barthélémy A, Michelet P, Bruguerolle B, et al. [Aspirin in decompression sickness] (French). Therapie. 2008; 63(6):
419-23.