med abstracts

We will be periodically posting medical abstracts on this page. Following each abstract will be some commentary about it relative to diving by Andrea Zaferes(in red).

Internal Carotid Artery Dissection in stroke from scuba diving: A case
report. Gibbs JW, Piantadosi CA, Massey EW UHMS 2002;29:3:167-171

Although diving with compressed air is generally safe, neurological problems
resulting from infarction in SCUBA diving are well known, including arterial
gas embolism and decompression sickness involving the brain and spinal cord.
While air gas embolism forms the overwhelming majority of causes for stroke
in divers, internal carotid artery dissection is another potential mechanism
for central nervous system infarction in the setting of SCUBA diving. A 38
year old female who presented with complaints of headache, nausea, vomiting,
and left sided hemiparesis after rapid ascent to the surface from a depth of
120 feet of seawater was initially treated for decompression illness in a
hyperbaric chamber. Further neurological workup revealed a right ICA
dissection. This case demonstrates the dangers of ICA dissection following
rapid ascent to the surface from underwater and emphasizes an interesting
presentation of stroke associated with SCUBA diving.

Paresis: partial or incomplete paralysis.
Hemiparesis: Hemi means half, so half paralysis.

Carotid artery dissection is an uncommon cause of stroke and is
predominantly observed in young to middle aged persons. Dissection of the
ICA frequently occurs in association with abnormal neck movements or direct
trauma to the neck. This case illustrates carotid dissection occurring in
the setting of deep diving with rapid ascent to the surface.

I looked up more possible signs and symptoms and they include: aphasia
(speech problems), behavior disturbances, visual field defects, and
decreased level of consciousness.

The moral to this story is to carefully look for and document signs and
symptoms and do not always assume that the DCI or AGE is the cause - and of
course plan your dives and be well trained enough so that the chance of a
rapid ascent from 120 feet is lessened as much as possible. Far too many
divers dive at deep depths where they have NO business being based on their
training and experience.

I asked Dr. Cliff Turen, the LGS Medical Director, to explain what carotid
artery dissection is (see previous medical abstract posting) . I looked it
up in a few books and didn't find a good description. Here is what he had to
say.

"A dissection is an situation where there is a fault in the wall of the
artery that allows, usually blood to enter the space between the two walls.
If this expands, the inner wall may encroach upon the vessel lumen
sufficiently to cause a thrombus. Thus causing the cerebral event. I am
not sure that the ascent would cause the dissection where there was not an
abnormality already existing. You know, as with many things, everyone tries
to find a link when something happens. I would have to search to find
reference to this in the literature, but I doubt the ascent caused this.
Anything is possible."

Physiological responses to cold exposure in men: a disabled submarine study. Castellani et al. UHM 2002;29:3:189-203

A disabled submarine lacking power and or environmental control will become cold, and the ambient air may become hypercapnic and hypoxic. This study examined if the combination of hypoxia, hypercapnia, and cold exposure would adversely affect thermoregulatory responses to acute cold exposure in survivors waiting rescue. Seven male submariners completed a series of cold-air tests that consisted of 20 min at 22 degrees C, followed by a linear decline to 12 degrees C for 150 min. Cold air tests were performed under normoxic, normocapnic conditions, and acute hypoxia, after 4 days of chronic hypoxia, hypercapnia an cold, and hypoxia only again.

The results were very complicated because there were so many variables so here are a few:

“The primary finding from this study was that acute moderate hypoxia blunted vasoconstriction and initial shivering responses during whole body cold exposure, and that the addition of both high CO2 and living cold ambient temperatures (4.5C) to simulate disabled submarine conditions, cause no further thermoregulatory effector changes. … even mild hypoxic conditions blunt thermoregulatory effector responses.”

Moral to this story, as I think I understand it, is that if we have a patient (who could of course be a diver) who is experiencing hypoxia, we need to be very careful about preventing heat loss. Capnic refers to carbon dioxide levels. So hypercapnic means higher levels than normal.

Reuter M, Tetzlaff K, Hutzelmann A, et al.
MR imaging of the central nervous system in diving-related decompression
illness
Acta Radiol 1997; 38:940-944

This investigation was conducted to determine whether MR imaging showed
cerebral or spinal damage in acute diving-related decompression illness, a
term that includes decompression sickness (DCS) and arterial gas embolism
(AGE). A total of 16 divers with dysbaric injuries were examined after the
initiation of therapeutic recompression. Their injuries comprised:
neurological DCS II n=8; AGEn=7; combined cerebral-AGE/spinal-DCSn=1. T1-
and T2- weighted images of the brain were obtained in two planes. In
addition, the spinal cord was imaged in seven subjects. The imaging findings
were correlated with the neurological symptoms. MR images of the head showed
ischemic cerebrovascular lesions in six of eight patients with AGE but
showed focal hyperintensities in only two of eight divers with DCS. Spinal
cord involvement was detected in one of seven examinations, which was the
combined cerebral-AGE/spinal-DCS case. There was agreement between the
locations of the documented lesions and the clinical manifestations. MR
readily detects cerebral damage in AGE but yields low sensitivity in DCS. A
negative MR investigation cannot rule out AGE or DCS. However, MR is useful
in the examination of patients with decompression illness.

How many of you have contacted your local hospital emergency department(s)
to find out what protocols they have for scuba-related accidents? We found
out many years ago that our local hospitals were sadly lacking in knowledge.
They kept a DCI victim in their ED for 17 hours because they didn't
understand the signs of DCI and it wasn't until they finally hooked up with
a DAN doctor that the diver was sent to Westchester Med for hyperbaric
treatment. Not good! Go talk with your ED docs. There is a good chance you
can teach them something. Sit down and develop a plan of action with them.
Make sure they know what DAN (Divers Alert Network) is and how to contact
DAN's emergency hotline - as well as when to call and why.
stay safe,
TeamLGS

Environmental Stress on diving-induced platelet activation.

UHMS 2001:28(4)207-211

Platelet activation has been suggested to play an important role in the pathogenesis of prethrombotic states and thus may be responsible for decompression illness during compressed air (scuba) diving. To investigate the physical, mental, and environmental stress on platelet activation during immersion in ice-cold water, we examined 10 male breath-hold divers (BHD), 10 elite BHD (eBHD), and ten scuba divers during immersion in an ice-covered lake at 2,030 m altitude. (water temp 0.6-1.2 degrees C, ice 1.5 m thick). All subjects swam from one ice hole to another hole 60 feet away, while wearing a 5mm wetsuit. Platelet activation was examined by surface expression of activation-dependent glycoproteins 10 min before, 1 min after, and 24 h after diving. Plasma epinephrine level was also measured, with the relationship between epinephrine levels and activated platelets. There was increased platelet activation in all three groups of divers. The percentage of platelet activation returned to pre-immersino levels in BHD and eBHD divers 24 h after diving, but was still higher in scuba divers. A positive relationship exists between the plasma epinephrine level and the percentage of platelet activation. This study suggests that physical and mental stress enhance platelet activation during diving in ice-cold water.

Platelet activation may increase the risk of or the severity of decompression illness (DCS and AGE). Picture a tiny bubble traveling slowly through a tiny diameter capillary. With platelet activation that bubble may be more likely to lodge and cause an obstruction. An already lodged bubble can become a larger obstruction as platelets form around it and the blood vessel’s endothelial tissue that was damaged by the bubble – that damage can activate the clotting system (e.g. platelet activation) aside from cold water immersion. Hence we move over one time category to the right on dive tables for cold dives, and move over two time categories for cold and arduous dives. Think about what other effects cold and exertion can have that might increase the chances of DCS or AGE. Let’s list them out and see what we can all learn. One hint is to remember that in regards to DCS – the more blood flow, perfusion, a tissue has, the faster that tissue on or offgasses. So if a tissue gets lots of blood flow during the dive at depth, and then less perfusion during ascent and the hang what are the implications for on and offgassing?

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