Effects of endotoxin on the pregnant baboon and fetus HISA YO 0. MORISHIMA, M.D., PH.D. WENDELL H. NIEMANN, D.V.M. L. STANLEY JAMES, M.D.
New York, New York Effects of E. coli endotoxin upon uterine activity and maternal and fetal condition were studied in four pregnant baboons and their fetuses. Uterine activity increased significantly following administration of endotoxin to the mother. Endotoxin also produced maternal circulatory collapse, severe acidosis, and profound fetal asphyxia resulting in death. Death also occurred in three of the four mothers within 24 hours without amelioration of their conditions. (AM. J. 0BSTET. GYNECOL. 131:899, 1978.)
HIGH FEVER IN OBSTETRIC PATIENTS with pyelonephritis accompanied by premature labor is not an infrequent occurrence. 1- 4 Premature labor probably is caused by the hyperthermia/' endotoxin, 6 • 7or endotoxin stimulation of resting uterine activity. 8 • 9 It has been reported that experimental endotoxemia in mice leads to abortion and fetal death due to the synthesis and release of endogenous prostaglandins. 10 The present experiments were undertaken to determine the effect of endotoxin upon uterine activity, maternal and fetal circulations, and temperature in pregnant baboons and their fetuses.
Material and methods Experiments were carried out on four pregnant ba· boons, Papio hybrid, of average gestational age of 167 days (term. 185 days), and their fetuses. Anesthetic management for the fetal operation and the details of the experimental model have been described elsewhere.1I. 12 Briefly after effecting general anesthesia with halothane, nitrous oxide and oxygen catheters were inserted into a femoral artery and vein of the mother and fetus at hysterotomy. Thermocouples were placed midway into the fetal esophagus and into the
maternal colon to a depth of 15 em. in order to measure the temperature gradient between fetus and mother (AF-M)· A catheter also was placed in the amniotic cavity for monitoring intra-amniotic pressure. Postoperatively, analgesia was maintained with 60 per cem nitrous oxide in oxygen, and respiration was as· sisted using a nonrebreathing method with intermittent positive pressure ventilation throughout the experiment. The arterial blood pressure, heart rate, and temperature of mother and fetus as well as intraamniotic pressure were measured continuously and recorded on a polygraph. Serial arterial blood samples were drawn simultaneously from mother and fetus for the determination of pH, Pco 2, Po 2, and hematocrit; all values were corrected for the individual maternal or fetal temperatures. Base deficits were calculated using a Radiometer blood calculator.* Uterine activity was expressed in Montevideo Units. 13 Animals were allowed to recover from the operation for two hours prior to the experiment (control period). E. coli endotoxint was injected intravenously into all mothers (5 mg. per kilogram-one hfth of the lethal dose).
Results From the Departmmts of Anesthesiology and Pediatrics, Collegt of Physician~ mul Surgeons, Columbia University. Supported in part by Grant 5P50-GM-09069 from the National Institute of General Medical Sciences, National lmtitutes of Health.
RPcPiz•td j(1r publication Nowmber 21, I 977. Rn•i1·1'd January I J, I 978. Ai'Cepted February 7, 1978.
Reprint request1: Dr. Hisa.~o 0. Morishima, Department of Anesthesiology, College of Physicians and Surgeon.1, Columbia University, 622 W. I 68th St., New York, New
York !0012.
·
0002·9378/78/08131·0899$00.40/0 © 1978 The C. V. Mosby Co.
During the control period, all mothers showed some uterine activity with an average of 35 Montevideo Units (range, 35 to 60). All fetuses were in good condition with a mean pHa value of 7.34 (range 7.30 to 7.40); PaC0 2 , 41 (40 to 42) torr; base deficit, 3.4 ( -0.8 to 6.3) mEq. per liter; Pa0 2 , 29 (25 to 32) torr: and temperature, 38.6° (38.5° to 38.7°) C. In Table I. changes in *London Co., Cleveland, Ohio. tO 127: B8 Lipopolysaccharide, Difco Laboratories, Detroit. Michigan.
899
900
Morishima, Niemann, and James Am.
J
August l ;,, l97H Obstet. C:ynecol.
Table I. The effects of endotoxin on uterine activity (Montevideo Units), temperature, mean arterial pressure. heart rate, and acid-base state of the mother and fetus in four experiments Mother Animal no.
Montevideo Units
Temp. (oC.)
M.BP (torr)
HR (b.p.m.)
35 24 20 60
38.0 38.1 38.2 38.0
98 103 100 106
115 130 104 150
100 180 140 480
38.6 38.6 37.9 38.2
88 93 88 83
180 200 160 480
39.4 39.2 39.0 39.9
70 70 60 65
Fetus
PaC0 2 (torr)
BD (mEq.IL.)
PaO, (torr)
ATF-M (oC.)
7.39 7.47 7.42
29 32 30 34
-0.3 4.5 0.7
0.5 0.4 0.5 0.5
42 50 40
1.6
154 146 148 128
120 170 120 170
7.44 7.35 7.40 7.32
25 28 27 21
5.3 8.7 6.6 14.0
136 110 139 116
0.6 0.4 0.7
160 130 185 170
7.35 7.34 7.29 7.28
27 31 24 21
9.8 9.8 14.2 15.8
126 124 140 110
pHa
MBP (torr)
I (b.p.m.) HR I pHa
Control:
104 1,005 965 994
7A9
41
184 185 190 200
7.33 7.30 7.40 7.32
1.0
45 53 47 47
150 140 140 140
7.15 7.15 7.18 7.12
-0.1 -0.2 00 0.2
38 37 21 37
140 200 80 210
7.00 6.97 6.78 6.96
60 minutes:
104 1,005 965 994 120 minutes:
104 1,005 965 994
*Legend: Temp., temperature; M.BP, mean blood pressure; HR, heart rate; BD, base deficit.
uterine activity as well as temperature, mean arterial pressure, heart rate, pHa, and blood gases of both mother and fetus following the injection of endotoxin are presented. Maternal temperature rose gradually after the injection of endotoxin from the initial value of 38.1° to 38.3° C. by 60 minutes and to 39.4° C. by 120 minutes. Fetuses in moderate distress had temperatures exceeding maternal temperatures; the temperature gradient between mother and fetus increased from the preinjection value of 0.48° (0.4° to 0.5°) to 0.68° (0.4° to 1.0°) C. after 60 minutes. This was followed by a decline in ~ T F-M when these fetuses developed profound asphyxia; in two instances ~ T F-M became reversed. A marked and consistent increase in uterine activity was observed in all animals following the administration of endotoxin (Table 1). A gradual but significant fall in maternal systemic arterial pressure and rise in heart rate occurred after the injection of endotoxin. The fetal heart rate declined steadily after the injection of endotoxin, while the blood pressure remained stable until onset of final deterioration. All fetuses exhibited late decelerations of the heart rate from the mean baseline value of 142 ( 140 to 150) to 85 (50 to 110) b.p.m. as the increase in uterine activity became extreme. Metabolic acidosis developed in both mother and fetus; a marked fall in maternal pHa and rise in base deficit were accompanied by a significant decrease in the fetal pHa and Pa0 2 from the initial values of 7.34 to 6. 93 (6. 78 to 7.00) and 29 to 7 (6 to 9) torr, respectively. A typical case showing the effects on tempera-
ture, mean arterial pressure, heart rate, and uterine activity following the injection of endotoxin is illustrated in Fig. l. Complications were considerable in this study. All fetuses died in utero two to six hours after the injection of endotoxin; at delivery, cerebral hemorrhage was found in one fetus, and 90 per cent placental separation was found in another. The recovery of the mother was noticeably prolonged, with persistent circulatory and respiratory depression. The animals remained flaccid and unresponsive following discontinuation of nitrous oxide near the end of the experiment; all animals regained consciousness two to three hours after discontinuation of anesthesia, but three mothers died within 24 hours of endotoxin administration.
Comment The present experiment has demonstrated that administration of £. roli endotoxin (5 mg. per kilogram~one fifth of lethal dose) to the pregnant baboon near term increases uterine activity and can cause a severe fetal distress leading to intrauterine death. Fetal deaths following administration of endotoxin probably are due to progressively severe hypotension in the mother together with the possible reduction of uterine blood flow, resulting in decreased oxygen supply to the fetus and subsequent metabolic acidosis in both mother and fetus. A fall in the fetal arterial oxygenation indicated a reduction in intervillous space perfusion. Our previous study has shown that hyperthermia, in the absence of infection, causes a marked increase in uterine activity in the pregnant baboon.·; Pregressive
Effects of endotoxin on pregnant baboon and fetus
Volume l:ll Number x
Endotoxin l .V.
Maternal Temp . (•C)
Remarks
(torr)
Baboon # 994 Gest . 164 days
:~~I t 39 0 385 380 1.0
0.5
901
.-
......•-•-•-•
Molh#r
·-·--
_.. _ _...... - · - · - · - · - -
f
~
6-~ 6-6-6...._
6 ..._6
'o--ll- 6 - 6 - A- ll
0 .0
-0.5
42
3.8
28
40 41 41
6.3
30 32 25
62 65 62 56
- 0.8 4.3
9.5 8.0 6.3 12.8
16 18 16
8
92
12.7
9
93
7
180
13.5 12.5
6
77
17.0
6
100 120r Mean Arterial
80
Prusure
60 40 20
(mmHgl
Late Late Late Late
deceleration deceleration deceleration deceleration
(150- 110 b. p.m.) (140--+ 100 b.p.m.) ( 140- 80 b. p.m.) (140--+ 50 b.p.m.)
Died; placental separation Died 4 hr. later Died 15 min. later Died 30 min. later; cerebral hemorrhage
""'-, •-·-·-•-•,
0
Heart Rate (btots/mln.)
Montevideo Unitt
°- o- 0
' o
F1lus
250~ 200 150
100 50
'"I 111111111111111
500 400 300 200 100
0
•
0
10 20 3040 50 60 ro eo 90Joo 110120130140150 TIME
hypotension and metabolic acidosis developed in both mother and fetus, leading to fetal deterioration. We postulate that the cause of increased uterine activity during hyperthermia could be related to several factors, including the release of oxytocin, antidiuretic hormone, cortisol, and catecholamines and synthesis of prostaglandin. The patterns of maternal and fetal responses to hyperthermia were similar to those observed in the animals given endotoxin in the present experiment. The response to an injection of bacterial endotoxin in mice, namely. fetal death as well as abortion, has been shown to be due to the synthesis and release of endogenous prostaglandins. 10 In addition, there is sharp increase in the concentration of prostaglandin F in the endometrium, urine, and serum following the administration of endotoxin in mice. 14 The profound and progressive fall in arterial pressure observed in the animals given endotoxin was similar to that reported in nonpregnant monkeys receiving a large dose (21 mg. per kilogram, LD 80 ) of E. cofi endotoxin. In these animals, the hypotension was caused primarily by a decrease in venous return. 1;; Marked species differences in the pattern of occurrence of hypotension as well as in the lethal dose have been shown between primates, dogs, 16 and sheep. 17 In sheep, a precipitous but brief drop in maternal blood pressure occurs after the injection of E. coli endotoxin (0.2 to 0.5 mg. per kilogram). This period is followed by a recovery phase, but hypotension and death soon followed. A marked fall in uterine blood How and uteroplacental oxygen transfer, accompanied by an increase in uterine vascular resistance, occurs during the
e-•-·-•-•-•, • - • -• Molltlr
New York, New York Effects of E. coli endotoxin upon uterine activity and maternal and fetal condition were studied in four pregnant baboons and their fetuses. Uterine activity increased significantly following administration of endotoxin to the mother. Endotoxin also produced maternal circulatory collapse, severe acidosis, and profound fetal asphyxia resulting in death. Death also occurred in three of the four mothers within 24 hours without amelioration of their conditions. (AM. J. 0BSTET. GYNECOL. 131:899, 1978.)
HIGH FEVER IN OBSTETRIC PATIENTS with pyelonephritis accompanied by premature labor is not an infrequent occurrence. 1- 4 Premature labor probably is caused by the hyperthermia/' endotoxin, 6 • 7or endotoxin stimulation of resting uterine activity. 8 • 9 It has been reported that experimental endotoxemia in mice leads to abortion and fetal death due to the synthesis and release of endogenous prostaglandins. 10 The present experiments were undertaken to determine the effect of endotoxin upon uterine activity, maternal and fetal circulations, and temperature in pregnant baboons and their fetuses.
Material and methods Experiments were carried out on four pregnant ba· boons, Papio hybrid, of average gestational age of 167 days (term. 185 days), and their fetuses. Anesthetic management for the fetal operation and the details of the experimental model have been described elsewhere.1I. 12 Briefly after effecting general anesthesia with halothane, nitrous oxide and oxygen catheters were inserted into a femoral artery and vein of the mother and fetus at hysterotomy. Thermocouples were placed midway into the fetal esophagus and into the
maternal colon to a depth of 15 em. in order to measure the temperature gradient between fetus and mother (AF-M)· A catheter also was placed in the amniotic cavity for monitoring intra-amniotic pressure. Postoperatively, analgesia was maintained with 60 per cem nitrous oxide in oxygen, and respiration was as· sisted using a nonrebreathing method with intermittent positive pressure ventilation throughout the experiment. The arterial blood pressure, heart rate, and temperature of mother and fetus as well as intraamniotic pressure were measured continuously and recorded on a polygraph. Serial arterial blood samples were drawn simultaneously from mother and fetus for the determination of pH, Pco 2, Po 2, and hematocrit; all values were corrected for the individual maternal or fetal temperatures. Base deficits were calculated using a Radiometer blood calculator.* Uterine activity was expressed in Montevideo Units. 13 Animals were allowed to recover from the operation for two hours prior to the experiment (control period). E. coli endotoxint was injected intravenously into all mothers (5 mg. per kilogram-one hfth of the lethal dose).
Results From the Departmmts of Anesthesiology and Pediatrics, Collegt of Physician~ mul Surgeons, Columbia University. Supported in part by Grant 5P50-GM-09069 from the National Institute of General Medical Sciences, National lmtitutes of Health.
RPcPiz•td j(1r publication Nowmber 21, I 977. Rn•i1·1'd January I J, I 978. Ai'Cepted February 7, 1978.
Reprint request1: Dr. Hisa.~o 0. Morishima, Department of Anesthesiology, College of Physicians and Surgeon.1, Columbia University, 622 W. I 68th St., New York, New
York !0012.
·
0002·9378/78/08131·0899$00.40/0 © 1978 The C. V. Mosby Co.
During the control period, all mothers showed some uterine activity with an average of 35 Montevideo Units (range, 35 to 60). All fetuses were in good condition with a mean pHa value of 7.34 (range 7.30 to 7.40); PaC0 2 , 41 (40 to 42) torr; base deficit, 3.4 ( -0.8 to 6.3) mEq. per liter; Pa0 2 , 29 (25 to 32) torr: and temperature, 38.6° (38.5° to 38.7°) C. In Table I. changes in *London Co., Cleveland, Ohio. tO 127: B8 Lipopolysaccharide, Difco Laboratories, Detroit. Michigan.
899
900
Morishima, Niemann, and James Am.
J
August l ;,, l97H Obstet. C:ynecol.
Table I. The effects of endotoxin on uterine activity (Montevideo Units), temperature, mean arterial pressure. heart rate, and acid-base state of the mother and fetus in four experiments Mother Animal no.
Montevideo Units
Temp. (oC.)
M.BP (torr)
HR (b.p.m.)
35 24 20 60
38.0 38.1 38.2 38.0
98 103 100 106
115 130 104 150
100 180 140 480
38.6 38.6 37.9 38.2
88 93 88 83
180 200 160 480
39.4 39.2 39.0 39.9
70 70 60 65
Fetus
PaC0 2 (torr)
BD (mEq.IL.)
PaO, (torr)
ATF-M (oC.)
7.39 7.47 7.42
29 32 30 34
-0.3 4.5 0.7
0.5 0.4 0.5 0.5
42 50 40
1.6
154 146 148 128
120 170 120 170
7.44 7.35 7.40 7.32
25 28 27 21
5.3 8.7 6.6 14.0
136 110 139 116
0.6 0.4 0.7
160 130 185 170
7.35 7.34 7.29 7.28
27 31 24 21
9.8 9.8 14.2 15.8
126 124 140 110
pHa
MBP (torr)
I (b.p.m.) HR I pHa
Control:
104 1,005 965 994
7A9
41
184 185 190 200
7.33 7.30 7.40 7.32
1.0
45 53 47 47
150 140 140 140
7.15 7.15 7.18 7.12
-0.1 -0.2 00 0.2
38 37 21 37
140 200 80 210
7.00 6.97 6.78 6.96
60 minutes:
104 1,005 965 994 120 minutes:
104 1,005 965 994
*Legend: Temp., temperature; M.BP, mean blood pressure; HR, heart rate; BD, base deficit.
uterine activity as well as temperature, mean arterial pressure, heart rate, pHa, and blood gases of both mother and fetus following the injection of endotoxin are presented. Maternal temperature rose gradually after the injection of endotoxin from the initial value of 38.1° to 38.3° C. by 60 minutes and to 39.4° C. by 120 minutes. Fetuses in moderate distress had temperatures exceeding maternal temperatures; the temperature gradient between mother and fetus increased from the preinjection value of 0.48° (0.4° to 0.5°) to 0.68° (0.4° to 1.0°) C. after 60 minutes. This was followed by a decline in ~ T F-M when these fetuses developed profound asphyxia; in two instances ~ T F-M became reversed. A marked and consistent increase in uterine activity was observed in all animals following the administration of endotoxin (Table 1). A gradual but significant fall in maternal systemic arterial pressure and rise in heart rate occurred after the injection of endotoxin. The fetal heart rate declined steadily after the injection of endotoxin, while the blood pressure remained stable until onset of final deterioration. All fetuses exhibited late decelerations of the heart rate from the mean baseline value of 142 ( 140 to 150) to 85 (50 to 110) b.p.m. as the increase in uterine activity became extreme. Metabolic acidosis developed in both mother and fetus; a marked fall in maternal pHa and rise in base deficit were accompanied by a significant decrease in the fetal pHa and Pa0 2 from the initial values of 7.34 to 6. 93 (6. 78 to 7.00) and 29 to 7 (6 to 9) torr, respectively. A typical case showing the effects on tempera-
ture, mean arterial pressure, heart rate, and uterine activity following the injection of endotoxin is illustrated in Fig. l. Complications were considerable in this study. All fetuses died in utero two to six hours after the injection of endotoxin; at delivery, cerebral hemorrhage was found in one fetus, and 90 per cent placental separation was found in another. The recovery of the mother was noticeably prolonged, with persistent circulatory and respiratory depression. The animals remained flaccid and unresponsive following discontinuation of nitrous oxide near the end of the experiment; all animals regained consciousness two to three hours after discontinuation of anesthesia, but three mothers died within 24 hours of endotoxin administration.
Comment The present experiment has demonstrated that administration of £. roli endotoxin (5 mg. per kilogram~one fifth of lethal dose) to the pregnant baboon near term increases uterine activity and can cause a severe fetal distress leading to intrauterine death. Fetal deaths following administration of endotoxin probably are due to progressively severe hypotension in the mother together with the possible reduction of uterine blood flow, resulting in decreased oxygen supply to the fetus and subsequent metabolic acidosis in both mother and fetus. A fall in the fetal arterial oxygenation indicated a reduction in intervillous space perfusion. Our previous study has shown that hyperthermia, in the absence of infection, causes a marked increase in uterine activity in the pregnant baboon.·; Pregressive
Effects of endotoxin on pregnant baboon and fetus
Volume l:ll Number x
Endotoxin l .V.
Maternal Temp . (•C)
Remarks
(torr)
Baboon # 994 Gest . 164 days
:~~I t 39 0 385 380 1.0
0.5
901
.-
......•-•-•-•
Molh#r
·-·--
_.. _ _...... - · - · - · - · - -
f
~
6-~ 6-6-6...._
6 ..._6
'o--ll- 6 - 6 - A- ll
0 .0
-0.5
42
3.8
28
40 41 41
6.3
30 32 25
62 65 62 56
- 0.8 4.3
9.5 8.0 6.3 12.8
16 18 16
8
92
12.7
9
93
7
180
13.5 12.5
6
77
17.0
6
100 120r Mean Arterial
80
Prusure
60 40 20
(mmHgl
Late Late Late Late
deceleration deceleration deceleration deceleration
(150- 110 b. p.m.) (140--+ 100 b.p.m.) ( 140- 80 b. p.m.) (140--+ 50 b.p.m.)
Died; placental separation Died 4 hr. later Died 15 min. later Died 30 min. later; cerebral hemorrhage
""'-, •-·-·-•-•,
0
Heart Rate (btots/mln.)
Montevideo Unitt
°- o- 0
' o
F1lus
250~ 200 150
100 50
'"I 111111111111111
500 400 300 200 100
0
•
0
10 20 3040 50 60 ro eo 90Joo 110120130140150 TIME
hypotension and metabolic acidosis developed in both mother and fetus, leading to fetal deterioration. We postulate that the cause of increased uterine activity during hyperthermia could be related to several factors, including the release of oxytocin, antidiuretic hormone, cortisol, and catecholamines and synthesis of prostaglandin. The patterns of maternal and fetal responses to hyperthermia were similar to those observed in the animals given endotoxin in the present experiment. The response to an injection of bacterial endotoxin in mice, namely. fetal death as well as abortion, has been shown to be due to the synthesis and release of endogenous prostaglandins. 10 In addition, there is sharp increase in the concentration of prostaglandin F in the endometrium, urine, and serum following the administration of endotoxin in mice. 14 The profound and progressive fall in arterial pressure observed in the animals given endotoxin was similar to that reported in nonpregnant monkeys receiving a large dose (21 mg. per kilogram, LD 80 ) of E. cofi endotoxin. In these animals, the hypotension was caused primarily by a decrease in venous return. 1;; Marked species differences in the pattern of occurrence of hypotension as well as in the lethal dose have been shown between primates, dogs, 16 and sheep. 17 In sheep, a precipitous but brief drop in maternal blood pressure occurs after the injection of E. coli endotoxin (0.2 to 0.5 mg. per kilogram). This period is followed by a recovery phase, but hypotension and death soon followed. A marked fall in uterine blood How and uteroplacental oxygen transfer, accompanied by an increase in uterine vascular resistance, occurs during the
e-•-·-•-•-•, • - • -• Molltlr
