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Fetal electrocardiographic studies
Fetal electrocardiographic studies Tachycardia as a sign of fetal distress J. BRADY, M.D.* L. S. JAMES, M.D.** With the technical assistance of
MARTHA A. BAKER, A.B., R.N. New York, New York
fetal tachycardia, all of which had respiratory depression at birth.
W r T H improved techniques for electrical monitoring of the fetal heart throughout labor, considerable attention has been paid to bradycardia. However, apart from two communications from this clinic, 1 • 2 there have been no reports confirming the clinical
Material and methods The fetal heart rate was monitored with an electrocardiogram in the labor and delivery room as previously described, 1 and the instantaneous heart rate was plotted against time. The instantaneous heart rate is the number of beats per minute, assuming that the time interval between two consecutive beats remains constant for 1 minute. For example, two beats 0.5 second apart would be a rate of 120 beats per minute; 1.0 second apart would be 60 beats per minute. In the present study the average rate for each 4 second period was used unless there was a very obvious change in less time. One hundred and eighteen cases were studied. No attempt was made to randomize the case material; many patients were primarily studied because of an abnormal heart rate on auscultation. In 49 cases continuous tracings for periods up to 3 hours were obtained during the first stage of labor or cesarean section. Blood from the umbilical artery was obtained from a clamped segment of the cord at birth and, in some instances, from the hypogastric artery immediately after birth. This was analyzed for per cent oxygen saturation, pH, and C02 content by methods reported elsewhere. 1 The carbon dioxide tension and buffer base were calculated. 8
observation that tachycardia is also a sign
of fetal distress. Bradycardia has been related to a number of factors: pressure on the fetal head, strong uterine contractions, and cord compression.3·~> Under these circumstances the bradycardia is usually intermittent and the infants are delivered in good condition. On the other hand, if bradycardia is prolonged it is usually associated with severe respiratory depression at birth. 5 We have found that this also holds true if tachycardia is prolonged. This present report describes 4 cases of From the Departments of Anesthesiology, Obstetrics and Gynecology, and Pediatrics of the College of Physicians and Surgeons, Columbia University, and the Divisions of Anesthesiology, Obstetrics and Gynecology (Sloane Hospital), and Pediatrics (Babies Hospital) of the Presbyterian Hospital. This research was supported by United States Public Health Grants H-2410 and B-2390. *Present address: 446 Second Ave., San Francisco, California. Fetal Life Study Fellow, National Institutes of Health Grant RG-4194. **Recipient of investigatorship of the Health Research Council of the City of New York under Contract 1-148.
785
786
Brady and James
July l'•· l 1ih.:
,\nJ.
J, Obst.
& (;~w····
Table I. Data of 4 infants with fetal tachycardia ----;---·--~-----,--------.,.-----
I
........
:,
__________
......--------..
Arterial
~-----~pCO~-~ B;;f--
----
. ---·-
......... --·
.-
Heart rate during contractions
6cm.
Baseline heart ratet 167:!: 10
115 ± 15
5
21 7.15 (umbilical artery)
PPO,ff Nuchal cord; meconium; dysmature
2
5cm.
167:!: 10
No change
4
59 6.93 92 28 (hypogastric artery at 3 minutes of age)
PPO,
3
6cm.
187 ± 10
100 ± 25+
2
4
Full dilatation
167 ± 8
No change
2
Case Dilatation No. of cervix*
Apgar I score 8 0,%§ pH
( mm. Hg)
fer base
Resuscitation
PPO,
6 6.95 (umbilical artery)
NoJes
Emergency cesarean section; meconium, dysmature Face presentation; meconium
Intuba- Emergency cetion sarean section; PPO, meconium; clysmature
*Dilatation of cervix; stage of labor when tachycardia was first recorded. tBaseline heart rate of 167 ± 10; heart. rate of 167 with brief fluctuations to 177 or 157. tHeart rate during contractions usually 100 but rates of 75 or 125 also occasionally seen. §0.%; per cent oxygen saturation. llpCOo; carbon dioxide tension in mm. Hg. l!PPO•; positive pressure oxygen.
Results
Normal baseline heart rates* were ob;erved in 37 of the 49 cases studied. Abnormally high baseline rates (above 160 per minute) were seen in 5 instances and slow baseline rates (below lOD-) in 7. Bradycardia was recorded for only a short time since delivery was achieved promptly after this sign was noted. On the other hand, tachycardia was recorded for prolonged periods because the significance of this sign was not appreciated. Heart rates, complications of labor, and biochemical determinations from the 4 cases exhibiting tachycardia are summarized in Table I. Case repo-rts Case 1. M. D. was a healthy 36-year-old multipara in whom labor began at 38 weeks' gestation after a normal antenatal course. During the *We have defined the baseline heart rate Ill! the rate during the interval between contractions. In normal term de· liveries during the first stage of labor it appears to lie between 115 to 150 beats per minute. This rate is very constant lor an individual fetus, and rarely- vari~ more than plus 'or minus 10 in an individual· i:ate. Extr~~&ystoles and drops in rate for 1 or 2 beats were occasionally seen.
first stage, a constant fetal heart rate of 160 to 188 beats per minute was recorded by auscultation (Fig. i ) . Membranes were ruptured artificially, releasing meconium-stained ammotJc fluid. The heart rate was irregular for a short period. When the cervix was 6 em. dilated fetal electrocardiogram revealed a baseline heart rate of 167 ± 10 falling to 115 ± 15 during contractions. An oxytocin infusion was given and 20 minutes later a female infant weighing 3,990 grams was delivered spontaneously under nitrous oxide analgesia, with a tight nucha] cord. Length of labor was 9 hours and the mother received meperidine ( 75 mg.) with scopolamine ( 0.4 mg.) 90 minutes prior to delivery. The infant was dysmature 7 with a golden vernix and peeling skin, made one gasp at 8 seconds, but did not breathe rhythmically until 70 seconds of age. At 1 minute of age, the infant had an Apgar score of 5, 8 was pale, limp, and not breathing. Positive pressure oxygen with a face mask was given for 1 minute after the onset of respiration because the infant's condition remained poor with a heart rate fluctuating between 115 and 193 beats per minute. Oxygen saturation at birth in the umbilical artery was 21 per cent and pH was 7.15. Case 2. C. R. was an 18~year-old primigravida. Antenatal -course was normal apart from
Volume 86 Number 6
Fetal electrocardiographic studies
pyelonephritis during the first trimester. She was admitted at term in early labor with ruptured membranes. The amniotic fluid was meconium stained and the fetal heart rate was 136 to 14·4 by auscultation~ Labor was ineffective and after 5 hours x-ray pelvimetry indicated absolute cephalopelvic disproportion. The patient received one dose of meperidine (75 mg.) and scopolamine (0.4 mg.). Fetal heart rate rose to 168 and electrical recording was started. This demonstrated a rate of 167 ± 10 which persisted throughout contractions. One hour later labor was terminated by cesarean section with the use of nitrous oxide and succinylcholine anesthesia. A limp dysmature male infant, weighing 3,480 grams (Clifford Grade III),9 was delivered. Apgar score at 1 minute was 4. The infant required positive pressure oxygen by mask to assist the onset of rhythmical respiration that was established at 2Y2 minutes of age. At 3 minutes of age the arterial pH was 6.98, P CO·• 92 mm.Hg, buffer base 28 mEq. per liter, and -oxygen saturation 59 per cent, indicating a severe respiratory and metabolic acidosis. Case 3. T. R. was a 25-year-old primigravida. Antenatal course was normal and labor began at term. The presentation was left mentoposterior and despite strong contractions progress was very slow. X-ray pelvimetry was performed and showed an adequate anthropoid pelvis. The mother received meperidine (50 mg.) after 8 hours, and again after 13 hours, together with atropine ( 0.3 mg.). At this time the fetal heart, which had been difficult to hear, was monitored electrically. A rate of 187 :': 10 was recorded falling from 100 to 25 with each contraction. When the cervix was fully dilated, the rate rose to 200 beats per minute falling tG 125 ± 25 with
5"' 200 .... .,_ 4•
~~ 150
·e "' ~! 100 ,__ z 4 ,_ tn
On
"'z
50
787
each contraction (Fig. 2). Eventually a limp, pale male infant, weighing 3,800 grams, bathed in meconium, was delivered after manual rotation under cyclopropane anesthesia. The Apgar score was 2 at 1 n1inute. Positive pressure oxygen was given by mask. Two minutes were required to establish rhythmical respiration. No biochemical determinations were made. Case 4. A. V. was a 24-year-old primipara, admitted at term with pre-eclampsia ( albuminuria 2+ and blood pressure 130 j90) , and some degree of inlet disproportion. The membranes ruptured spontaneously during an episode of false labor, and the mother's temperature was noted to be 101° F. Amnionitis was suspected and chloramphenicol therapy instituted. Labor commenced 24 hours later. The mother's temperature remained elevated ( 101.4° F.) and yellow offensive meconium-stained amniotic fluid was passed from which E. coli was cultured. Progress of labor was poor. Because of the amnionitis, prompt delivery was considered desirable. X-ray pelvimetry revealed an adequate pelvis and an oxytocin infusion was begun after 7 hours of labor. The cervix was fully dilated 12 hours later but the head continued to remain high. After a further 2 hours with little change, a cesarean section was performed under epidural anesthesia. Total length of labor was 21 hours. The mother received secobarbital sodium ( 100 mg.) at the onset of labor, meperidine ( 100 mg.) and scopolamine (0.4 mg.) 7 hours later, and scopolamine (0.3 mg.) 1 hour before delivery. During the first stage of labor the fetal heart rate was normal by clinical auscultation ( 128148). When the cervical dilatation reached a rim, fetal electrocardiogram revealed a rate of
CERVIX 6cms
CERVIX
Bcms
~(- rrft/\:r}j - - - - -·
CONTRACTIONS
2.12PM
2:28PM
TIME IN MINUTES
Fig. 1. Case 1. Tachycardia with relative bradycardia during contractions associated with a tight nuchal cord. Fetal tachycardia between contractions. Infant dysmature, requiring resuscitation, Ap-
gar score 5. Umbilical artery oxygen saturation 21 per cent, pH 7.15.
788 Brady and James
j ~ 2,::rER:xsc:
Am .
CERVIX FULLY DILATED
1(J[}C ; ~ .v=+Pi-A~ v . ~ s ~ 100~-~--~--~--~------------"'
.
~ :! ~
~! ~
i
50 '
_
__
- - - -. -
nlrctCii ons
!:
~~···-~~~ ~1-r---~~~~ ~~~
0 5:OOPM
7:30PM
TIME IN MINUTES
Fig. 2. Case 3. Face presentation. Baseline tachycardia with relative bradycardia during contractions. No evidence of any cord complication at delivery.
136. An hour later tachycardia was noted for the first time. Fig. 3 is a portion of the original tracing taken at the onset of tachycardia ( 167 beats per minute). The rate remained high and extremely regular in spite of pelvic examinations and contractions augmented by an oxytocin infusion. It also remained at this same rate throughout the cesarean section (Fig. 4). A limp, dysmature male infant (3,410 grams) was delivered. He gasped once at 48 seconds and then remained apneic. At 1 minute the Apgar score was 2. Electrocardiogram record at this time revealed a heart rate of 158 beats per minute, and showed also an elevated S-T segment. Oxygen saturation was 6 per cent and pH was 6.95. The larynx was intubated and the lungs expanded artificially by mouth to tube breathing. The heart rate rose immediately to 200 beats per minute. Rhythmical respiration did not commence until 4 minutes. At age 30 minutes the heart rate had fallen to 140 and the S-T segment was isoelectric. Comment
In these 4 case studies a persistent fetal tachycardia between uterine contractions and minimal maternal sedation was associat-
J.
July 15, 1963 Obst. & Gynec.
ed with severe neonatal respiratory depression, the infants all requiring active resuscitation. On the other hand, in the 37 infants who were vigorous and breathed spontaneously there were no instances of prolonged tachycardia. These observations indicate that fetal tachycardia which persists between contractions is an important sign of fetal distress and is not benign as others have suggested. 10 - 12 However, brief periods of tachycardia seen during the final stages of labor and delivery in vigorous healthy infants 1 appear to have no clinical importance. Marked acidosis with arterial pH values of 6.93 to 7.15 were seen in 3 infants (Nos. 1, 2, and 4) who also showed signs of dysmaturity, a condition which others have reported to be frequently associated with fetal distress and respiratory depression at birth. 7 ' 9 In contrast, there were no marked signs of dysmaturity in any of the infants with normal baseline rates during labor. Rapid rates with no consistent changes during contractions were seen in 2 (Nos. 2 and 4). Both passed yellow meconium during labor which was finally terminated by cesarean section. The presence of dysmaturity together with the severe acidosis at birth suggest that the infants might have been severely compromised had the labor been further prolonged. One of the mothers (No. 4) had a fever of 101.4° F. This might have influenced the fetal heart rate. 1 3 However, it could not have been the sole cause since the maternal fever preceded the fetal tachycardia by several hours. Evidence of cord compression was seen
F•'•' ~U•rf hhl • I 7 ... fr/•llf M•f,HI NH'I _ , , , . , 1) . . . ,.;'.-.
,,,,,,,,,,
-IMC
I
4
PM
Fig. 3. Portion of original tracing from Case 4. 1'.J'otc constant rapid
fetal rate. Fetal complexes are of shorter duration and slightly less voltage than maternal.
Volume 86 Number 6
Fig. 4. Case 4. Persistent fetal tachycardia associated with maternal fever, amnionitis, and dysmaturity. Heart rate remained rapid through uterine contractions, pelvic manipulations, cesarean section, and after delivery when the infant was depressed and apneic.
in the tracings of 2 (Nos. 1 and 3) (Figs. 1 and 2;,. A nuchal cord was present at delivery in 1 (No. 1). However, there was no clinical evidence of any cord complication in the other infant (No. 3) who was born as a face presentation. It is possible that compression of the carotid sinus occurred when the neck was hyperextended during contractions. This would explain the bradycardia seen with each contraction over a 2 hour period, but not the baseline tachycardia of 187 rising to 200 at full dilatation. Fetal tachycardia can be produced in a number of ways; but the precise mechanisms involved have not yet been defined. Experimentally, transient tachycardia can be induced during the last trimester simply by a loud! vibratory stimuli or cigarette smoking;14• 15 rates of 180 to 200 beats per minute have been reported. In the fetal Iamb a sustained tachycardia occurs when the oxygen content of the air inspired by the ewe is reduced. 16 A similar response is seen experimentally if the lamb is asphyxiated by partial cord occlusion and there is both hypoxia and hypercapnia. 16 • 17 The increase REFERENCES 1. Brady, ]., James, L. S., and Baker, M. A.: AM. J. OnsT. & GYNEC. 84: 1, 1962. :!. Brady, J., and James, L. S.: Bull. Sloane Hosp. Women. 8: 1, 1962.
3. Hon, E. If.: Aru:. J. 0Bs'I'. & GYNEc. 77: 1084, 1959. 4. Chung, F., and Hon, E. H.: Obst. & Gynec. 13: 633, 1959. 5. Hon, E. H.: AM. ]. OnsT. & GYNEC. 83: 333, 1962.
Fetal electrocardiographic studies 789
in heart rate is probably related to sympathetic stimulation.18 When very low levels of oxygenation are reached, bradycardia occurs.16 From the practical point of view it appears that a living infant can be delivered after several hours of persistent fetal tachycardia. With fetal bradycardia however, a critical time interval exists between the time of its discovery and the delivery of the infant, perinatal mortality tripling after half an hour. 10 A possible explanation is that persistent tachycardia represents a response to circulatory stress from moderate fetal asphyxia. Cardiac output and therefore tissue oxygenation can be maintained for a while. On the other hand persistent bradycardia represents a more severe degree of fetal asphyxia and the onset of circulatory failure from severe myocardial depression. Cardiac output begins to fall and tissue oxygenation becomes inadequate. In this light, fetal tachycardia, if present, would be an earlier sign of fetal distress than bradycardia.
Conclusions Prolonged tachycardia was observed in the 4 cases studied with the fetal electrocardiogram during labor. All had respiratory depression at birth and required resuscitation. In 3 cases marked acidosis was confirmed by biochemical determinations. Persistent tachycardia during labor occurring between contractions appears to be a sign of fetal distress. Our findings suggest that if tachycardia is noted, early delivery of the infant should be effected either by forceps or cesarean section, and without further stimulation of labor.
6. Singer, R. B., and Hastings, A. B.: Medicine 27: 223, 1948. 7. Sjostedt, S., Engleson, G., and Rooth, G.: Arch. Dis. Childhood 33: 123, 1958. 8. Apgar, V., et al.: J. A. M. A. 168: 1985, 1958. 9. Clifford, S. H.: Advances Pediat. 9: 13, 1957. l 0. Fenton, A., and Steer, C. M.: AM. J. On sT. & GYNEC. 83: 354, 1962. 11. Lund, C. J.: AM. J. OnsT. & GYJ>;EC. 45: 636. 1943.
790 Brady and James
12. Bartholomew, R. A.: AM. J. OasT. & GYNEC. 10: 89, 1925. 13. McCredie Smith, J. A., Jennison, R. F., and Langley, F. A.: Lancet 2: 903, 1956. 14. Sontag, L. W., and Newberry, H.: Am. J. Dis. Child. 62: 991, 1941. 15. Hellman, L. M., Johnson, H. L., Tolles, W. E. and Jones, E. H.: AM. J. OasT. & GYNEC. 82: 1055, 1961. 16. Born, G. V. R., Dawes, G. S., and Mott, J, C.: J. Physiol. 134: 149, 1956.
July l'J, l!JtJ) \n1.
J.
OhsL & Gynt•t
17. Born, G. V. R., Dawes, G. S., Mott,]. C., and Rennick, B. R.: ]. Physiol. 132: 304, 1956. 18. Comline, R. S., and Silver, M.: Nature 181: 283, 1958. 622 West 168th St. New York 32, New York (Dr. fames)
MARTHA A. BAKER, A.B., R.N. New York, New York
fetal tachycardia, all of which had respiratory depression at birth.
W r T H improved techniques for electrical monitoring of the fetal heart throughout labor, considerable attention has been paid to bradycardia. However, apart from two communications from this clinic, 1 • 2 there have been no reports confirming the clinical
Material and methods The fetal heart rate was monitored with an electrocardiogram in the labor and delivery room as previously described, 1 and the instantaneous heart rate was plotted against time. The instantaneous heart rate is the number of beats per minute, assuming that the time interval between two consecutive beats remains constant for 1 minute. For example, two beats 0.5 second apart would be a rate of 120 beats per minute; 1.0 second apart would be 60 beats per minute. In the present study the average rate for each 4 second period was used unless there was a very obvious change in less time. One hundred and eighteen cases were studied. No attempt was made to randomize the case material; many patients were primarily studied because of an abnormal heart rate on auscultation. In 49 cases continuous tracings for periods up to 3 hours were obtained during the first stage of labor or cesarean section. Blood from the umbilical artery was obtained from a clamped segment of the cord at birth and, in some instances, from the hypogastric artery immediately after birth. This was analyzed for per cent oxygen saturation, pH, and C02 content by methods reported elsewhere. 1 The carbon dioxide tension and buffer base were calculated. 8
observation that tachycardia is also a sign
of fetal distress. Bradycardia has been related to a number of factors: pressure on the fetal head, strong uterine contractions, and cord compression.3·~> Under these circumstances the bradycardia is usually intermittent and the infants are delivered in good condition. On the other hand, if bradycardia is prolonged it is usually associated with severe respiratory depression at birth. 5 We have found that this also holds true if tachycardia is prolonged. This present report describes 4 cases of From the Departments of Anesthesiology, Obstetrics and Gynecology, and Pediatrics of the College of Physicians and Surgeons, Columbia University, and the Divisions of Anesthesiology, Obstetrics and Gynecology (Sloane Hospital), and Pediatrics (Babies Hospital) of the Presbyterian Hospital. This research was supported by United States Public Health Grants H-2410 and B-2390. *Present address: 446 Second Ave., San Francisco, California. Fetal Life Study Fellow, National Institutes of Health Grant RG-4194. **Recipient of investigatorship of the Health Research Council of the City of New York under Contract 1-148.
785
786
Brady and James
July l'•· l 1ih.:
,\nJ.
J, Obst.
& (;~w····
Table I. Data of 4 infants with fetal tachycardia ----;---·--~-----,--------.,.-----
I
........
:,
__________
......--------..
Arterial
~-----~pCO~-~ B;;f--
----
. ---·-
......... --·
.-
Heart rate during contractions
6cm.
Baseline heart ratet 167:!: 10
115 ± 15
5
21 7.15 (umbilical artery)
PPO,ff Nuchal cord; meconium; dysmature
2
5cm.
167:!: 10
No change
4
59 6.93 92 28 (hypogastric artery at 3 minutes of age)
PPO,
3
6cm.
187 ± 10
100 ± 25+
2
4
Full dilatation
167 ± 8
No change
2
Case Dilatation No. of cervix*
Apgar I score 8 0,%§ pH
( mm. Hg)
fer base
Resuscitation
PPO,
6 6.95 (umbilical artery)
NoJes
Emergency cesarean section; meconium, dysmature Face presentation; meconium
Intuba- Emergency cetion sarean section; PPO, meconium; clysmature
*Dilatation of cervix; stage of labor when tachycardia was first recorded. tBaseline heart rate of 167 ± 10; heart. rate of 167 with brief fluctuations to 177 or 157. tHeart rate during contractions usually 100 but rates of 75 or 125 also occasionally seen. §0.%; per cent oxygen saturation. llpCOo; carbon dioxide tension in mm. Hg. l!PPO•; positive pressure oxygen.
Results
Normal baseline heart rates* were ob;erved in 37 of the 49 cases studied. Abnormally high baseline rates (above 160 per minute) were seen in 5 instances and slow baseline rates (below lOD-) in 7. Bradycardia was recorded for only a short time since delivery was achieved promptly after this sign was noted. On the other hand, tachycardia was recorded for prolonged periods because the significance of this sign was not appreciated. Heart rates, complications of labor, and biochemical determinations from the 4 cases exhibiting tachycardia are summarized in Table I. Case repo-rts Case 1. M. D. was a healthy 36-year-old multipara in whom labor began at 38 weeks' gestation after a normal antenatal course. During the *We have defined the baseline heart rate Ill! the rate during the interval between contractions. In normal term de· liveries during the first stage of labor it appears to lie between 115 to 150 beats per minute. This rate is very constant lor an individual fetus, and rarely- vari~ more than plus 'or minus 10 in an individual· i:ate. Extr~~&ystoles and drops in rate for 1 or 2 beats were occasionally seen.
first stage, a constant fetal heart rate of 160 to 188 beats per minute was recorded by auscultation (Fig. i ) . Membranes were ruptured artificially, releasing meconium-stained ammotJc fluid. The heart rate was irregular for a short period. When the cervix was 6 em. dilated fetal electrocardiogram revealed a baseline heart rate of 167 ± 10 falling to 115 ± 15 during contractions. An oxytocin infusion was given and 20 minutes later a female infant weighing 3,990 grams was delivered spontaneously under nitrous oxide analgesia, with a tight nucha] cord. Length of labor was 9 hours and the mother received meperidine ( 75 mg.) with scopolamine ( 0.4 mg.) 90 minutes prior to delivery. The infant was dysmature 7 with a golden vernix and peeling skin, made one gasp at 8 seconds, but did not breathe rhythmically until 70 seconds of age. At 1 minute of age, the infant had an Apgar score of 5, 8 was pale, limp, and not breathing. Positive pressure oxygen with a face mask was given for 1 minute after the onset of respiration because the infant's condition remained poor with a heart rate fluctuating between 115 and 193 beats per minute. Oxygen saturation at birth in the umbilical artery was 21 per cent and pH was 7.15. Case 2. C. R. was an 18~year-old primigravida. Antenatal -course was normal apart from
Volume 86 Number 6
Fetal electrocardiographic studies
pyelonephritis during the first trimester. She was admitted at term in early labor with ruptured membranes. The amniotic fluid was meconium stained and the fetal heart rate was 136 to 14·4 by auscultation~ Labor was ineffective and after 5 hours x-ray pelvimetry indicated absolute cephalopelvic disproportion. The patient received one dose of meperidine (75 mg.) and scopolamine (0.4 mg.). Fetal heart rate rose to 168 and electrical recording was started. This demonstrated a rate of 167 ± 10 which persisted throughout contractions. One hour later labor was terminated by cesarean section with the use of nitrous oxide and succinylcholine anesthesia. A limp dysmature male infant, weighing 3,480 grams (Clifford Grade III),9 was delivered. Apgar score at 1 minute was 4. The infant required positive pressure oxygen by mask to assist the onset of rhythmical respiration that was established at 2Y2 minutes of age. At 3 minutes of age the arterial pH was 6.98, P CO·• 92 mm.Hg, buffer base 28 mEq. per liter, and -oxygen saturation 59 per cent, indicating a severe respiratory and metabolic acidosis. Case 3. T. R. was a 25-year-old primigravida. Antenatal course was normal and labor began at term. The presentation was left mentoposterior and despite strong contractions progress was very slow. X-ray pelvimetry was performed and showed an adequate anthropoid pelvis. The mother received meperidine (50 mg.) after 8 hours, and again after 13 hours, together with atropine ( 0.3 mg.). At this time the fetal heart, which had been difficult to hear, was monitored electrically. A rate of 187 :': 10 was recorded falling from 100 to 25 with each contraction. When the cervix was fully dilated, the rate rose to 200 beats per minute falling tG 125 ± 25 with
5"' 200 .... .,_ 4•
~~ 150
·e "' ~! 100 ,__ z 4 ,_ tn
On
"'z
50
787
each contraction (Fig. 2). Eventually a limp, pale male infant, weighing 3,800 grams, bathed in meconium, was delivered after manual rotation under cyclopropane anesthesia. The Apgar score was 2 at 1 n1inute. Positive pressure oxygen was given by mask. Two minutes were required to establish rhythmical respiration. No biochemical determinations were made. Case 4. A. V. was a 24-year-old primipara, admitted at term with pre-eclampsia ( albuminuria 2+ and blood pressure 130 j90) , and some degree of inlet disproportion. The membranes ruptured spontaneously during an episode of false labor, and the mother's temperature was noted to be 101° F. Amnionitis was suspected and chloramphenicol therapy instituted. Labor commenced 24 hours later. The mother's temperature remained elevated ( 101.4° F.) and yellow offensive meconium-stained amniotic fluid was passed from which E. coli was cultured. Progress of labor was poor. Because of the amnionitis, prompt delivery was considered desirable. X-ray pelvimetry revealed an adequate pelvis and an oxytocin infusion was begun after 7 hours of labor. The cervix was fully dilated 12 hours later but the head continued to remain high. After a further 2 hours with little change, a cesarean section was performed under epidural anesthesia. Total length of labor was 21 hours. The mother received secobarbital sodium ( 100 mg.) at the onset of labor, meperidine ( 100 mg.) and scopolamine (0.4 mg.) 7 hours later, and scopolamine (0.3 mg.) 1 hour before delivery. During the first stage of labor the fetal heart rate was normal by clinical auscultation ( 128148). When the cervical dilatation reached a rim, fetal electrocardiogram revealed a rate of
CERVIX 6cms
CERVIX
Bcms
~(- rrft/\:r}j - - - - -·
CONTRACTIONS
2.12PM
2:28PM
TIME IN MINUTES
Fig. 1. Case 1. Tachycardia with relative bradycardia during contractions associated with a tight nuchal cord. Fetal tachycardia between contractions. Infant dysmature, requiring resuscitation, Ap-
gar score 5. Umbilical artery oxygen saturation 21 per cent, pH 7.15.
788 Brady and James
j ~ 2,::rER:xsc:
Am .
CERVIX FULLY DILATED
1(J[}C ; ~ .v=+Pi-A~ v . ~ s ~ 100~-~--~--~--~------------"'
.
~ :! ~
~! ~
i
50 '
_
__
- - - -. -
nlrctCii ons
!:
~~···-~~~ ~1-r---~~~~ ~~~
0 5:OOPM
7:30PM
TIME IN MINUTES
Fig. 2. Case 3. Face presentation. Baseline tachycardia with relative bradycardia during contractions. No evidence of any cord complication at delivery.
136. An hour later tachycardia was noted for the first time. Fig. 3 is a portion of the original tracing taken at the onset of tachycardia ( 167 beats per minute). The rate remained high and extremely regular in spite of pelvic examinations and contractions augmented by an oxytocin infusion. It also remained at this same rate throughout the cesarean section (Fig. 4). A limp, dysmature male infant (3,410 grams) was delivered. He gasped once at 48 seconds and then remained apneic. At 1 minute the Apgar score was 2. Electrocardiogram record at this time revealed a heart rate of 158 beats per minute, and showed also an elevated S-T segment. Oxygen saturation was 6 per cent and pH was 6.95. The larynx was intubated and the lungs expanded artificially by mouth to tube breathing. The heart rate rose immediately to 200 beats per minute. Rhythmical respiration did not commence until 4 minutes. At age 30 minutes the heart rate had fallen to 140 and the S-T segment was isoelectric. Comment
In these 4 case studies a persistent fetal tachycardia between uterine contractions and minimal maternal sedation was associat-
J.
July 15, 1963 Obst. & Gynec.
ed with severe neonatal respiratory depression, the infants all requiring active resuscitation. On the other hand, in the 37 infants who were vigorous and breathed spontaneously there were no instances of prolonged tachycardia. These observations indicate that fetal tachycardia which persists between contractions is an important sign of fetal distress and is not benign as others have suggested. 10 - 12 However, brief periods of tachycardia seen during the final stages of labor and delivery in vigorous healthy infants 1 appear to have no clinical importance. Marked acidosis with arterial pH values of 6.93 to 7.15 were seen in 3 infants (Nos. 1, 2, and 4) who also showed signs of dysmaturity, a condition which others have reported to be frequently associated with fetal distress and respiratory depression at birth. 7 ' 9 In contrast, there were no marked signs of dysmaturity in any of the infants with normal baseline rates during labor. Rapid rates with no consistent changes during contractions were seen in 2 (Nos. 2 and 4). Both passed yellow meconium during labor which was finally terminated by cesarean section. The presence of dysmaturity together with the severe acidosis at birth suggest that the infants might have been severely compromised had the labor been further prolonged. One of the mothers (No. 4) had a fever of 101.4° F. This might have influenced the fetal heart rate. 1 3 However, it could not have been the sole cause since the maternal fever preceded the fetal tachycardia by several hours. Evidence of cord compression was seen
F•'•' ~U•rf hhl • I 7 ... fr/•llf M•f,HI NH'I _ , , , . , 1) . . . ,.;'.-.
,,,,,,,,,,
-IMC
I
4
PM
Fig. 3. Portion of original tracing from Case 4. 1'.J'otc constant rapid
fetal rate. Fetal complexes are of shorter duration and slightly less voltage than maternal.
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Fig. 4. Case 4. Persistent fetal tachycardia associated with maternal fever, amnionitis, and dysmaturity. Heart rate remained rapid through uterine contractions, pelvic manipulations, cesarean section, and after delivery when the infant was depressed and apneic.
in the tracings of 2 (Nos. 1 and 3) (Figs. 1 and 2;,. A nuchal cord was present at delivery in 1 (No. 1). However, there was no clinical evidence of any cord complication in the other infant (No. 3) who was born as a face presentation. It is possible that compression of the carotid sinus occurred when the neck was hyperextended during contractions. This would explain the bradycardia seen with each contraction over a 2 hour period, but not the baseline tachycardia of 187 rising to 200 at full dilatation. Fetal tachycardia can be produced in a number of ways; but the precise mechanisms involved have not yet been defined. Experimentally, transient tachycardia can be induced during the last trimester simply by a loud! vibratory stimuli or cigarette smoking;14• 15 rates of 180 to 200 beats per minute have been reported. In the fetal Iamb a sustained tachycardia occurs when the oxygen content of the air inspired by the ewe is reduced. 16 A similar response is seen experimentally if the lamb is asphyxiated by partial cord occlusion and there is both hypoxia and hypercapnia. 16 • 17 The increase REFERENCES 1. Brady, ]., James, L. S., and Baker, M. A.: AM. J. OnsT. & GYNEC. 84: 1, 1962. :!. Brady, J., and James, L. S.: Bull. Sloane Hosp. Women. 8: 1, 1962.
3. Hon, E. If.: Aru:. J. 0Bs'I'. & GYNEc. 77: 1084, 1959. 4. Chung, F., and Hon, E. H.: Obst. & Gynec. 13: 633, 1959. 5. Hon, E. H.: AM. ]. OnsT. & GYNEC. 83: 333, 1962.
Fetal electrocardiographic studies 789
in heart rate is probably related to sympathetic stimulation.18 When very low levels of oxygenation are reached, bradycardia occurs.16 From the practical point of view it appears that a living infant can be delivered after several hours of persistent fetal tachycardia. With fetal bradycardia however, a critical time interval exists between the time of its discovery and the delivery of the infant, perinatal mortality tripling after half an hour. 10 A possible explanation is that persistent tachycardia represents a response to circulatory stress from moderate fetal asphyxia. Cardiac output and therefore tissue oxygenation can be maintained for a while. On the other hand persistent bradycardia represents a more severe degree of fetal asphyxia and the onset of circulatory failure from severe myocardial depression. Cardiac output begins to fall and tissue oxygenation becomes inadequate. In this light, fetal tachycardia, if present, would be an earlier sign of fetal distress than bradycardia.
Conclusions Prolonged tachycardia was observed in the 4 cases studied with the fetal electrocardiogram during labor. All had respiratory depression at birth and required resuscitation. In 3 cases marked acidosis was confirmed by biochemical determinations. Persistent tachycardia during labor occurring between contractions appears to be a sign of fetal distress. Our findings suggest that if tachycardia is noted, early delivery of the infant should be effected either by forceps or cesarean section, and without further stimulation of labor.
6. Singer, R. B., and Hastings, A. B.: Medicine 27: 223, 1948. 7. Sjostedt, S., Engleson, G., and Rooth, G.: Arch. Dis. Childhood 33: 123, 1958. 8. Apgar, V., et al.: J. A. M. A. 168: 1985, 1958. 9. Clifford, S. H.: Advances Pediat. 9: 13, 1957. l 0. Fenton, A., and Steer, C. M.: AM. J. On sT. & GYNEC. 83: 354, 1962. 11. Lund, C. J.: AM. J. OnsT. & GYJ>;EC. 45: 636. 1943.
790 Brady and James
12. Bartholomew, R. A.: AM. J. OasT. & GYNEC. 10: 89, 1925. 13. McCredie Smith, J. A., Jennison, R. F., and Langley, F. A.: Lancet 2: 903, 1956. 14. Sontag, L. W., and Newberry, H.: Am. J. Dis. Child. 62: 991, 1941. 15. Hellman, L. M., Johnson, H. L., Tolles, W. E. and Jones, E. H.: AM. J. OasT. & GYNEC. 82: 1055, 1961. 16. Born, G. V. R., Dawes, G. S., and Mott, J, C.: J. Physiol. 134: 149, 1956.
July l'J, l!JtJ) \n1.
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17. Born, G. V. R., Dawes, G. S., Mott,]. C., and Rennick, B. R.: ]. Physiol. 132: 304, 1956. 18. Comline, R. S., and Silver, M.: Nature 181: 283, 1958. 622 West 168th St. New York 32, New York (Dr. fames)