Læknablaðið : fylgirit - 01.09.1993, Qupperneq 32

30
LÆKNABLAÐIÐ/FYLGIRIT 24
Veggspjöld
Ágrip veggspjalda á læknaþingi
13.-14. september 1993
A Mathematical Modelling of Biliary and Pan-
creatic Excretion in Man Based on Power_______
Spectral Analysis. J.R. Sveinsson, E. Péturs-
son, S.B. Stefánsson, S. Kristjánsdóttir,
D. Davidsson, 'O.G. BjÖrnsson, S. Bjornsson.
Haskóli fslands, Landakotsspítali, Landsspít-
ali, Reykjavík, Iceland.
Fast-Fourier power spectral analysis [1]
was used to examine biliary and pancreatic
excretory patterns in healthy human volunteers
(age 20 - 49 years, n = 4 - 6), or cholecyst-
ectomized subjects (age 33 - 70 years, n = 7).
Data were obtained either by duodenal perfus-
ion/aspiration (discrete signals), Tc-99mHIDA
cholescintigraphy, or by 75Se-HCAT (a synthet-
ic bile salt) abdominal counting. Power
spectral analysis based on the method of
smoothed periodograms of overlapping sectors
(after detrending and centering of the data
around the mean), showed that biliary excret-
ion into the duodenum in normal subjects was
affected in an exponential manner (first de-
gree process) by the cholecystokinin (CCK)
analogue caerulein, or a mixture of essential
amino acids (EEA), or an inhibitor like sod-
ium taurocholate (STC), i.e. gave a reasonable
fit to p(t) - k(l - e_t/T); t = time, T = time
constant; k = proportionality factor). The
time constant for the (assumed) EAA-induced
CCK release was, Tcc^ 5 min., and for the
gallbladder Tgb <: 1 min. (Tc-99mHIDA). Hepatic
removal of Tc-99mHIDA from blood was > 90%
complete by 30 min.; tl/2 for abdominal 75Se-
HCAT loss (an estimate of ileal bile salt ab-
sorption) was 4.7 days (a monoexponential.de-
cline) (n = 4, normal volunteers only). The
time constant for the inhibitory effect on the
biliary excretion induced by STC was, Tacck 06
5 min., with a 10 min. transport delay. STC
had no effect on trypsin excretion. Low pass
filtering and frequency analysis of biliary
excretion of indocyanine green (ICG) into the
duodenum in cholecystectomized subjects re-
vealed an oscillatory component with a period
* 40 min., superimposed on the sustained aver-
age output. Spectral analysis of bilirubin and
pancreatic excretion in healthy subjects sug-
gested an average period of around 60 min.
with 50% of the total power within the range
of 40 - 90 min. Reinfusion of aspirate into
the jejunum in order to preserve the entero-
hepatic bile salt pool did not affect period-
icity but "stabilized" the biliary excretion
patterns, i.e. reduced total power and the
peak power (resonance regions) of the signal.
A graphical model based on the above data is
presented. - [1] Digital Filtering and Signal
Processing, West Publ. Co. N.Y. 1975; [2] Time
and Frequency Domain Analysis. In: Biomedical
Signal Processing, vol. I, CRC Press, Inc.,
Boca Raton, Florida, 1986.