The aim of this study was to see if a short-term period of exposure to cold
in young healthy subjects causes changes in hematological factors known to
be associated with the promotion of thrombogenesis. Over a period of 48 ho
urs, changes in the distribution of erythrocytes, granulocytes, and blood p
latelets, as well as several coagulation, inflammatory, and fibrinolytic pa
rameters, were monitored in 11 young healthy male subjects following a shor
t period (1 hour) of cold exposure (CE) (ambient temperature, 11 degrees C)
or exposure to thermoneutral conditions (ambient temperature, 26 degrees C
) in winter (November). The major findings were: (1) a CE-induced hemoconce
ntration as indicated by an increase in erythrocyte count (3.2% increase);
(2) after appropriate adjustments for changes in hemoconcentration, a cold-
induced mobilization of granulocytes (14.5% increase) and a cold-induced de
crease in lymphocytes (7% decrease); (3) thromboxane B-2 release following
endotoxin stimulation of whole blood was increased by 27.4% in the CE exper
iments; (4) diurnal rhythms were observed in granulocytes, blood platelets,
middle plate volume, tissue plasminogen activator, and plasma activator in
hibitor; and (5) CE caused no significant changes in lipopolysaccharide-ind
uced tissue factor, nor in the blood coagulation factor VII or cytokines, i
nterleukin-6, and tumor necrosis factor, It is concluded that short-term co
ld exposure in young healthy subjects initiates a mild inflammatory reactio
n and a tendency for an increased state of hypercoagulability. (C) 1999 Els
evier Science Ltd. All rights reserved.