241 Clinical trials on continuous measurement of fetal tcPco2
Dr. S. Schmidt
Institute of Perinatal Medicine, Free University of Berlin Mariendorfer Weg 28, D-1OOO Berlin 4 4 , Germany
We have used the tcPco2 registration in addition to the super- vision of the fetus during labor by cardiotocography (CTG) and fetal blood analysis. We use a modified Severinghaus electrode (Radiometer E 523O) at a measuring temperature of 39°C respec- tively 44 C ( 2 ) . By comparing the transcutaneously measured data with the values measured in the fetal blood it is possi- ble to answer some specific questions of tcPco^ monitoring in the fetus ( 1 ) : In order to test the reliability of the tcPco2
registration at different measuring temperatures we analysed the correlation between Pco2 of the FBA and the synchroneously registered tcPco2 at 39 C (r = O . 7 4 , p O.OO1, slope : 1.O5, intercept: +8.57, n = 111) and compared this result,-with the analysis at 44 C (Fig. 1 ) . while afc bQth temperatulES
tcf>c°2 the correlation is signi-
lmmHfll IkPal ficant (p< O . O O 1 ) , due to Co? production in the tis- sue and the effect of the raised temperature, the transcutaneous values ex- ceed the values of the fetal blood (at 44 C to a greater extent than at 39°)
( 3 ) . By comparing data of cases in which a caput succedaneum developed with cases where no such pheno- menon occurred, we were able to elicit its influ- ence on the tcPco~ mea- surement ( T a b . I ) . We also analysed the influence of the duration of the tnans- cutaneous measurement on its accuracy (Tab. I I ) .
99 r - 0.81
tcPco2 - 1.15 - Pco2(FBA) -f 11.6 ρ < 0.001
β 12 [kPa]
90 [mmHg]Pco2 Fig. 1
caput
succedaneum 39° C - 39° C + 44° C - 44° C +
correlation (R) 0.78 0.72 0.82 0.80
significance
< 0.001
< 0.001
< 0.001
< 0.001
intercept 10.84 11.78 14.68
3.18
slope 1.01 0.99 1.09 1.28
number of values
28 83 74 25
A caput succeda- neum has a con- siderable influ- ence on the reli- ability of the tcPco2 measure- ment especially when the precho-
sen temperature Tab. I is 39 C while measurements at 44 C seem to be less accurate after registra-
tion of 15O min. As one basis of fetal surveillance is the intermittent pH measurement the correlation of the tcPco9
J.Perinat.Med. 12(1980
Copyright by Walter de Gruyter & Co., Berlin-New York
242 duration of measurement
< 1 50min 39» C
> 1 50min 39° C
< 1 50min 440 c
> 1 50min 440 C
correlation (R)
0.86 0.83 0.93 0.79
significance
< 0.001
< 0.001
< 0.001
< 0.001
intercept
11.92 7.60 8.16 7.41
slope
0.98 1.11 1.21 1.24
number of values
13 14 24 20 Tab. II
tcPco9 values
>70 mmHg (Pig.
[mmHg] [kPa]
30
with the pH is of great clinical importance. In
•bhe range between a pH level of
7.25 to 7.5O we find the tcPco2 values to be
rather scattered.
However with pH value dropping to 7 . 2 4 (pre- acidösis), all of this study at 44 C and not corrected,: are 2) . If we only then perform an
FBA when the indication emerged from an irregular heart rate pattern, and ad- ditionally this level of 7O mmHg is exceeded, a consi- derable number of FBAs could be spared. (This action line should be confirmed by addi- tional measurements). Fur-.
thermore the timing of an obstetrical operation may be optimised. During our cli- nical trial the occurrence of an acute complication was in all instances clearly
indicated by a rise of the
127 - 53
-99 · pH(FBA) + 78a8
TOO 7.10 120 130 140 tcPco2 value from its ori- ginal level. All these ba-
ISO pH(FBA]
bies, in spite of acidosis, were born by immediate ope- ration before clinical sigis (Apgar<7) had manifested.
of depression Bibliography
( 1 ) SALiTNG, E . : Neues Vorgehen zur Untersuchung des Kindes unter der Geburt (Einführung, Technik, Grundlagen).
Arch.Gynäk. 197 ( 1 9 6 2 ) , 1O8
(2) SCHMIDT, S., K.LANGNER,J.ROTHE,E.SALING: A new combined non-invasive electrode for tcPco9 measurement and fetal heart rate recording. J.Perinat.Med. 1O ( 1 9 8 2 ) , 297
(3) SEVERINGHAUS, J . W . , M.STAFFORD, A.F.BRADLEY: tcPco elec- trode design, calibration and temperature gradient2
problems. Acta Anesth.Scand.Suppl. 68 ( 1 9 7 8 ) , 118
J.Perlnat.Med. 12(W)
