Biology Reference
In-Depth Information
anxiety, numerous medications (pseudoephedrine, digoxin, etc.), alcohol, numerous
street drugs (especially cocaine and amphetamines), and caffeine (excessive coffee
intake is a common cause, and “energy drinks” also contain large amounts of caf-
feine as well as other stimulants such as guarana extract), hypoxia, electrolyte dis-
turbances (e.g., hypokalemia), and other underlying asymptomatic and symptomatic
arrhythmias, as well as myocardial infarction, myocarditis, cardiomyopathy, and oth-
ers. In comparison to PACs, there are a few more data regarding the epidemiology
of PVCs among certain populations. Available evidence indicates no increased mor-
tality among patients with normal cardiac evaluation who report palpitations that are
related to PVCs (Abbott, 2005; Kennedy et al., 1985). A large, multiple-community-
based, cross-sectional analysis of 15,792 individuals (aged 45-65 years) suggested that
PVCs were present in
6% of middle-aged American adults (Simpson et al., 2002).
Increasing age, the presence of heart disease, faster sinus rates, African American eth-
nicity, male sex, lower educational attainment, and lower serum levels of some elec-
trolytes (magnesium or potassium) were directly associated with PVC prevalence.
Hypertension was independently associated with a 23% increase in the prevalence
of PVCs (Simpson et al., 2002). This emphasizes the essential need for carefully
collected and documented medical history, prescription medication regimens (and
adherence or lack thereof to prescribed dosing frequency), and basic psychosocial
background (especially alcohol and street drug use) of any patient presenting with a
reportedly medically significant snakebite. These factors may play an integral part in
the presentation, and thus related symptoms/signs may be independent of the circum-
stances. However, three cases of
Naja
spp. envenomings that included dysrhythmias
have been reported. These occurred in India and Malaysia and included either ST seg-
ment depression with inverted T waves or atrioventricular juctional escape rhythm with
left bundle branch block (Pahlajani et al., 1987; Reid, 1964).
Naja
spp. likely respon-
sible for these envenoming (e.g.,
N. kaouthia
,
N. naja
) secrete venoms that contain car-
diotoxins and often produce serious or life-threatening envenoming. Therefore, some
envenomings by highly venomous species may occasionally include dysrhythmias.
Conversely, the clinician must remain cognizant of the possibility of exacerbation of
comorbid illness (e.g., ischemic cardiac disease, generalized anxiety disorder, etc; see
Sections 4.5 and 4.6) in the event of clinically significant effects from a bite inflicted
by any colubroid species of unknown medical importance.
It must also be observed that although the patient in this aberrant case reported
“paralysis” hours after sustaining the bite, and “muscle weakness” lasting for
2 months, there was no documented evidence of neuropathy, neurotoxicity, or myopathy.
Regardless, due to the reported symptoms/signs, documentation of electromyographic
testing, autoimmune serology, follow-up neurological examination, and imaging (if indi-
cated) are all desirable (see the aberrant alleged
P. najadum
case; Sections 4.4 and 4.6).
Caution is advised when handling these snakes due to their large size, and their
capacity for producing relatively substantial volumes of proteolytic secretion.
Special precautions should be taken when feeding captive specimens or when per-
forming captive maintenance after handling potential food items. Larger specimens
are capable of inflicting a painful local wound. Currently, there are no data that pro-
vide acceptable evidence of systemic envenoming by this species.
