Fetal and Maternal Plasma Electrolytes, Blood Gases, and pH in Dairy Cows during Late Gestation G. D. A. W I L S O N , J. T. H U N T E R , G. H. D E R R I C K , W. M. A I T K E N and D. S. K R O N F E L D 1 Ministry of Agriculture and Fisheries Ruakura Animal Research Station Private Bag, Hamilton, New Zealand
ABSTRACT
fluids and maternal and fetal bloods. Fetal blood is buffered well by phosphate, bicarbonate, and proteins. Relationships between anion concentrations and gas tensions influence acidity of the blood. Studies by Meschia et al. (12) have provided the impetus for development of techniques for the continuous catheterization of fetal blood vessels and fluid spaces in conscious animals. This paper furthers the studies of Meschia et al. (12) and Comline and Silver (5, 6) presenting results of determinations of sodium, chloride, and potassium in plasma, together with blood gas and pH data in pregnant cows and their fetuses. Other results are presented in (22).
Sodium, potassium, and chloride were determined in fetal and maternal plasma of six cows between 208 and 269 days of gestation. Blood pH and partial pressures of oxygen and carbon dioxide also were measured in samples collected from the jugular vein of the cow and the caudal aorta and vena cava of the fetus. Concentration of chloride in fetal plasma was generally lower than the corresponding maternal value, and fetal potassium was greater than maternal. Potassium of fetal plasma increased towards term. Sodium concentrations were not significantly different between fetal and maternal plasmas. Once fetal and maternal pH and blood gas tensions had stabilized after surgery, there was little change until shortly before delivery. In the last 24 h before calving maternal partial pressure of oxygen was high and fetal blood pH was low.
MATERIALS AND METHODS
INTRODUCTION
Sodium, chloride, and potassium ions are important components of fetal fluids in the sheep, and their concentrations in amniotic and allantois fluids change with advancing gestation and during parturition (10). These changes probably are mediated by fetal secretion of corticosteroids and antidiuretic hormone (11). During formation of amniotic and allantoic fluid, electrolytes equilibrate between these
Received November 5, 1976. 1Dept. of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348, U.S.A.
Surgery was on six pregnant cows of 208 to 244 days gestational age. Indwelling catheters were inserted into the fetal caudal vena cava and fetal caudal aorta through the lateral saphenous vein and artery at the level of the point of the hock. Anaesthesia, medication, and management of the animals were as in (22). Heparinized blood samples were withdrawn anaerobically from the catheters at 24 to 48-h intervals from shortly after surgery until delivery. Samples from maternal jugular vein were collected simultaneously by previously inserted catheters. Samples were stored anaerobically at 4 C, and Po2, P c o 2 , and pH were measured at 37 C within 2 h of sampling by standard Radiometer electrodes coupled to a digital readout (PHM72, Radiometer, Copenhagen). Maternal and fetal venous plasmas were separated, and chloride was determined on the Technicon Autoanalyzer 1 by Standard Method N5. Sodium and potassium were measured with an a t o m i c absorption spectrophotometer (Model SP90, Unicam Instruments Ltd, Cambridge).
1110
FETAL BLOOD GASES, pH, AND ELECTROLYTES
1111
TABLE 1. Concentrations of potassium, sodium and chloride in fetal and maternal plasma of six cows between 48 h after insertion of fetal catheters and parturition. Mother Mean Potassium m Eq/liter Sodium m Eq/liter Chloride m Eq/liter
Fetus Range
3.80 139 102
Mean
2.64 - 6.17 122 - 1 5 0 85.0 - 111
RESULTS Plasma Electrolytes
Since f e w fetuses could be sampled at exactly the same t i m e over the gestational period, data for sodium, chloride, and potassium are presented in relation to parturition regardless of the degree o f prematurity. Data collected within 48 h after surgery have been excluded f r o m statistical analyses because t h e y may be less representative o f n o r m a l pregnancy. All means were calculated f r o m simultaneously collected paired samples f r o m maternal jugular vein and fetal caudal vena cava. Overall means for potassium, sodium, and chloride in maternal and fetal plasma for the six experimental cows over t h e 22 days before delivery are in Table 1. Mean 48-h sequential data in these animals are summarized in Fig. 1 and 2 in relation to t i m e of delivery. Mean 48-hourly potassium values in maternal plasma were all lower than corresponding
150" 140-
Sodium
Range
4.19 140 97.2
Observations where maternal value < fetal
2.85 - 6.65 117 - 1 5 6 87.8 - 111
49/67 45/69 12/59
fetal values (Fig. 2), and similarly derived chloride values were all higher than their fetal equivalents (Fig. 1). No differences were consistent b e t w e e n fetal and maternal mean 48hourly sodium c o n c e n t r a t i o n s in plasma. Overall mean sodium c o n c e n t r a t i o n in maternal plasma for the six cows over the last 22 days before parturition was only slightly lower than s o d i u m in fetal plasma (Table 1). Blood Gas Tensions and pH
Gas tensions and pH of maternal venous and fetal arterial and venous blood remained fairly constant in individual cows f r o m a b o u t 48 h after surgery until i m m e d i a t e l y before parturition (Tables 2 and 3). Between 4 and 6 h after surgery, maternal pH values were slightly lower than those collected later. Fetal arterial and venous p H were less affected, and values were close to those shown subsequently. Maternal Po2 usually was elevated for 4 to 6 h after surgery (Table 4). Steady values were established a b o u t 24 h after surgery for pH, P 0 2 , and P C 0 2 of fetal blood. These were maintained until parturition when fetal pH fell and fetal P c 0 2 increased. This is shown in Fig. 3 for an individual c o w in
130T20-
E Chloride I00" ,
-20
i
i
-16
,
,
,
i
,
,
,
-12 -8 -4 0 Doys from parturition
,
,
*4
,
,
+8
FIG. 1. Mean 48-hourly sodium and chloride of maternal (o) and fetal (A) plasma in six cows in late pregnancy and at parturition.
-20
-16
-12 -8 -4 0 Days f r o m p u r t u r i t i o n
+4
+8
FIG. 2. Mean 48-hourly potassium of maternal (o) and fetal (A) plasma in six cows in late pregnancy and at parturition. Journal of Dairy Science Vol. 60, No. 7
bo
TABLE 2. S u m m a r y of b l o o d pH in fetal and mater na l blood of six cows from 48 h after surgery until 24 h before parturition. -T
< e_
g :z o
Cow
Days of
no.
gestation*
Mean
Maternal jugular b l o o d SE
n
Mean
35 46 131 132 134 150
244--268 224 -238 231 250 246-254 210 226 224-241
7.44 7.44 7.38 7.36 7.44 7.41
•004 .010 .018 .009 .009 .013
13 12 17 8 9 14
7.35 7.40 . . 7.31 7.33 7.36
Fetal vena b lo o d
Fetal aortic bl ood SE
.
.
.012 .007 . . . .004 .007 .012
.
n
Mean
SE
11 9
7.31 7.39 7.33 7.29 7.31 7.35
.010 .010 .013
. 8 8 12
9 12 17 3 7 14
.009 .010
*Period of sampling used to calculate these means. t" ¢/3 © Z ,.q > .r' TABLE 3. Tensions of oxygen and carbon dioxide in fetal and ma t e rna l blood of six
PO2 mm ttg
PCO 2 m m Hg
Cow no.
gestation*
Mean
SE
Mean
SE
35 46 131 132 134 150
244-268 224-238 231-250 246-254 210-226 224-241
36.1 31.1 34.2 35.7 33.9 33.7
1.10 .77 .95 2.00
36.8 44.2 42.5 37,5 44,2 39.9
3.21 1.71 1.65 1,53 ... 2.57
1175
*Period of sampling used to calculate these means.
from 48 h after surgery until 24 h before parturition. Fetal vena cava blood
Fetal aortic blood
Maternal jugular blood Days of
cows
Poa m m Ilg
PO: m m ttg
PCO~ mm Hg
Mean
n
Mean
SE
Mean
SE
6 9 17 8 3 11
21.0 28.3
.76 1.85 ... .41 ... .80
43.7 46.0
2.26 2.38
6 7
4319 45.7 48.2
i195
8 3 9
2310 24.6 24.5
1179
19.7 27.2 25.8 17.7 19.9 22.9
SE
1124 1.11
16o
PCO 2 m m Hg Mean 50.1 47.5 48.2 48.4 48.8 49.1
SE
i148 2.34
i182
4 9 17 3 3 9
FETAL BLOOD GASES, pH, A N D ELECTROLYTES
1113
7 6~ i
74t
724 J "~4,4
,~e4 " ,,
E t0,d-
.-
::
,,,,
£o20 t
to,~
-6
R
I
-5 -4 -3 -2 -I Hours from parturition*
0
,
J
+I
FIG. 3. Fetal vena cave (A) and maternal jugular (o) blood gas tensions and pH in a single cow sampled during first and second stage labor f r o m the onset of abdominal contractions. R = rupture of aUantoic membrane. Parturition * was manually assisted.
tr, t~ •d-
8
. . . . .
~toO
v
labor. No changes in fetal or maternal pH, P O 2 , o r PCO2 were obvious with increasing gestational age. Gradients in pH, P O 2 , and P C O 2 w e r e noted in all animals in all sets of samples between maternal vein, fetal artery, and fetal vein.
O
t~ ,a= ¢,I
DISCUSSION
b
Plasma Sodium
e-
£ 8
>l
..= O
1:¢
a:
=~8 =0"8
e~ 0
O
4
r,1
ABSTRACT
fluids and maternal and fetal bloods. Fetal blood is buffered well by phosphate, bicarbonate, and proteins. Relationships between anion concentrations and gas tensions influence acidity of the blood. Studies by Meschia et al. (12) have provided the impetus for development of techniques for the continuous catheterization of fetal blood vessels and fluid spaces in conscious animals. This paper furthers the studies of Meschia et al. (12) and Comline and Silver (5, 6) presenting results of determinations of sodium, chloride, and potassium in plasma, together with blood gas and pH data in pregnant cows and their fetuses. Other results are presented in (22).
Sodium, potassium, and chloride were determined in fetal and maternal plasma of six cows between 208 and 269 days of gestation. Blood pH and partial pressures of oxygen and carbon dioxide also were measured in samples collected from the jugular vein of the cow and the caudal aorta and vena cava of the fetus. Concentration of chloride in fetal plasma was generally lower than the corresponding maternal value, and fetal potassium was greater than maternal. Potassium of fetal plasma increased towards term. Sodium concentrations were not significantly different between fetal and maternal plasmas. Once fetal and maternal pH and blood gas tensions had stabilized after surgery, there was little change until shortly before delivery. In the last 24 h before calving maternal partial pressure of oxygen was high and fetal blood pH was low.
MATERIALS AND METHODS
INTRODUCTION
Sodium, chloride, and potassium ions are important components of fetal fluids in the sheep, and their concentrations in amniotic and allantois fluids change with advancing gestation and during parturition (10). These changes probably are mediated by fetal secretion of corticosteroids and antidiuretic hormone (11). During formation of amniotic and allantoic fluid, electrolytes equilibrate between these
Received November 5, 1976. 1Dept. of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348, U.S.A.
Surgery was on six pregnant cows of 208 to 244 days gestational age. Indwelling catheters were inserted into the fetal caudal vena cava and fetal caudal aorta through the lateral saphenous vein and artery at the level of the point of the hock. Anaesthesia, medication, and management of the animals were as in (22). Heparinized blood samples were withdrawn anaerobically from the catheters at 24 to 48-h intervals from shortly after surgery until delivery. Samples from maternal jugular vein were collected simultaneously by previously inserted catheters. Samples were stored anaerobically at 4 C, and Po2, P c o 2 , and pH were measured at 37 C within 2 h of sampling by standard Radiometer electrodes coupled to a digital readout (PHM72, Radiometer, Copenhagen). Maternal and fetal venous plasmas were separated, and chloride was determined on the Technicon Autoanalyzer 1 by Standard Method N5. Sodium and potassium were measured with an a t o m i c absorption spectrophotometer (Model SP90, Unicam Instruments Ltd, Cambridge).
1110
FETAL BLOOD GASES, pH, AND ELECTROLYTES
1111
TABLE 1. Concentrations of potassium, sodium and chloride in fetal and maternal plasma of six cows between 48 h after insertion of fetal catheters and parturition. Mother Mean Potassium m Eq/liter Sodium m Eq/liter Chloride m Eq/liter
Fetus Range
3.80 139 102
Mean
2.64 - 6.17 122 - 1 5 0 85.0 - 111
RESULTS Plasma Electrolytes
Since f e w fetuses could be sampled at exactly the same t i m e over the gestational period, data for sodium, chloride, and potassium are presented in relation to parturition regardless of the degree o f prematurity. Data collected within 48 h after surgery have been excluded f r o m statistical analyses because t h e y may be less representative o f n o r m a l pregnancy. All means were calculated f r o m simultaneously collected paired samples f r o m maternal jugular vein and fetal caudal vena cava. Overall means for potassium, sodium, and chloride in maternal and fetal plasma for the six experimental cows over t h e 22 days before delivery are in Table 1. Mean 48-h sequential data in these animals are summarized in Fig. 1 and 2 in relation to t i m e of delivery. Mean 48-hourly potassium values in maternal plasma were all lower than corresponding
150" 140-
Sodium
Range
4.19 140 97.2
Observations where maternal value < fetal
2.85 - 6.65 117 - 1 5 6 87.8 - 111
49/67 45/69 12/59
fetal values (Fig. 2), and similarly derived chloride values were all higher than their fetal equivalents (Fig. 1). No differences were consistent b e t w e e n fetal and maternal mean 48hourly sodium c o n c e n t r a t i o n s in plasma. Overall mean sodium c o n c e n t r a t i o n in maternal plasma for the six cows over the last 22 days before parturition was only slightly lower than s o d i u m in fetal plasma (Table 1). Blood Gas Tensions and pH
Gas tensions and pH of maternal venous and fetal arterial and venous blood remained fairly constant in individual cows f r o m a b o u t 48 h after surgery until i m m e d i a t e l y before parturition (Tables 2 and 3). Between 4 and 6 h after surgery, maternal pH values were slightly lower than those collected later. Fetal arterial and venous p H were less affected, and values were close to those shown subsequently. Maternal Po2 usually was elevated for 4 to 6 h after surgery (Table 4). Steady values were established a b o u t 24 h after surgery for pH, P 0 2 , and P C 0 2 of fetal blood. These were maintained until parturition when fetal pH fell and fetal P c 0 2 increased. This is shown in Fig. 3 for an individual c o w in
130T20-
E Chloride I00" ,
-20
i
i
-16
,
,
,
i
,
,
,
-12 -8 -4 0 Doys from parturition
,
,
*4
,
,
+8
FIG. 1. Mean 48-hourly sodium and chloride of maternal (o) and fetal (A) plasma in six cows in late pregnancy and at parturition.
-20
-16
-12 -8 -4 0 Days f r o m p u r t u r i t i o n
+4
+8
FIG. 2. Mean 48-hourly potassium of maternal (o) and fetal (A) plasma in six cows in late pregnancy and at parturition. Journal of Dairy Science Vol. 60, No. 7
bo
TABLE 2. S u m m a r y of b l o o d pH in fetal and mater na l blood of six cows from 48 h after surgery until 24 h before parturition. -T
< e_
g :z o
Cow
Days of
no.
gestation*
Mean
Maternal jugular b l o o d SE
n
Mean
35 46 131 132 134 150
244--268 224 -238 231 250 246-254 210 226 224-241
7.44 7.44 7.38 7.36 7.44 7.41
•004 .010 .018 .009 .009 .013
13 12 17 8 9 14
7.35 7.40 . . 7.31 7.33 7.36
Fetal vena b lo o d
Fetal aortic bl ood SE
.
.
.012 .007 . . . .004 .007 .012
.
n
Mean
SE
11 9
7.31 7.39 7.33 7.29 7.31 7.35
.010 .010 .013
. 8 8 12
9 12 17 3 7 14
.009 .010
*Period of sampling used to calculate these means. t" ¢/3 © Z ,.q > .r' TABLE 3. Tensions of oxygen and carbon dioxide in fetal and ma t e rna l blood of six
PO2 mm ttg
PCO 2 m m Hg
Cow no.
gestation*
Mean
SE
Mean
SE
35 46 131 132 134 150
244-268 224-238 231-250 246-254 210-226 224-241
36.1 31.1 34.2 35.7 33.9 33.7
1.10 .77 .95 2.00
36.8 44.2 42.5 37,5 44,2 39.9
3.21 1.71 1.65 1,53 ... 2.57
1175
*Period of sampling used to calculate these means.
from 48 h after surgery until 24 h before parturition. Fetal vena cava blood
Fetal aortic blood
Maternal jugular blood Days of
cows
Poa m m Ilg
PO: m m ttg
PCO~ mm Hg
Mean
n
Mean
SE
Mean
SE
6 9 17 8 3 11
21.0 28.3
.76 1.85 ... .41 ... .80
43.7 46.0
2.26 2.38
6 7
4319 45.7 48.2
i195
8 3 9
2310 24.6 24.5
1179
19.7 27.2 25.8 17.7 19.9 22.9
SE
1124 1.11
16o
PCO 2 m m Hg Mean 50.1 47.5 48.2 48.4 48.8 49.1
SE
i148 2.34
i182
4 9 17 3 3 9
FETAL BLOOD GASES, pH, A N D ELECTROLYTES
1113
7 6~ i
74t
724 J "~4,4
,~e4 " ,,
E t0,d-
.-
::
,,,,
£o20 t
to,~
-6
R
I
-5 -4 -3 -2 -I Hours from parturition*
0
,
J
+I
FIG. 3. Fetal vena cave (A) and maternal jugular (o) blood gas tensions and pH in a single cow sampled during first and second stage labor f r o m the onset of abdominal contractions. R = rupture of aUantoic membrane. Parturition * was manually assisted.
tr, t~ •d-
8
. . . . .
~toO
v
labor. No changes in fetal or maternal pH, P O 2 , o r PCO2 were obvious with increasing gestational age. Gradients in pH, P O 2 , and P C O 2 w e r e noted in all animals in all sets of samples between maternal vein, fetal artery, and fetal vein.
O
t~ ,a= ¢,I
DISCUSSION
b
Plasma Sodium
e-
£ 8
>l
..= O
1:¢
a:
=~8 =0"8
e~ 0
O
4
r,1
