- Email: [email protected]
Effect of alcohol on fetal cerebral function and metabolism
Effect of alcohol on fetal cerebral function and metabolism LEON
I.
MANN,
AMRUTHA
M.D.
BHAKTHAVATHSALAN,
MAIDA
LIU,
PHILIP
MAKOWSKI,
East Meadow
M.D.
B.S. M.D.
and Stony
Brook,
New
York
The effect of maternal alcohol infusion on fetal cerebral function in terms of the electroencephalogram (EEG) and fetal brain metabolism was studied in 10 fetal sheep experiments. A 9.75 per cent alcohol-dextrose solution was infused at the rate of 15 CL. per kilogram of maternal weight for 1 or 2 hours. Fetal cerebral uptake of oxygen was unaffected. Blood flow was significantly increased as a result of a greater decrease in resistance than decrease in blood pressure. The cerebral uptake of glucose and the glucose-oxygen utilization ratio were significantly increased. The EEG showed a decrease in amplitute and slowing of the dominant rhythm as the blood alcohol concentration increased and became isoelectric on occasion during the postinfusion period associated with a severe fetal acidosis.
W H I L E T H E maternal infusion of alcohol has been shown to be effective in inhibiting premature labor in a statistically significant number of cases,r the question of what effect the infusion of alcohol has on the cardiovascular, metabolic, and acid-base status of the fetus has only recently been investigated and reported in the literature.z-4 In an acute study on fetal sheep Dilts reported no significant alteration in fetal metabolism and acid-base balance during alcohol infusion, although placental transport of oxygen and fetal oxygenation were impaired during experiments conducted under pentobarbital
anesthesia. Horiguchi and associates,4 in a semiacute monkey preparation, reported a successful inhibition of spontaneous or induced labor prior to term that was associated with a significant fetal tachycardia, fall in blood pressure, and acidosis. An unsubstantiated clinical impression exists that premature newborn infants delivered following an unsuccessful attempt with alcohol to inhibit the premature labor are more severely depressed at birth, require vigorous resuscitative measures, and have a higher incidence of hyaline membrane disease than premature infants delivered without alcohol infusion. In a previous report we confirmed the observations of Horiguchi by showing a significant fetal acidosis during and following the infusion of alcohol in an acute fetal sheep preparation. The results of the direct effect of alcohol and/or the associated acidosis on fetal brain function and metabolism are presented here.
From the Department of Obstetrics and Gynecology, Nassau County Medical Center, East Meadow, and the Health Sciences Center, State University of New York at Stony Brook. Supported in part by a grant from the United Cerebral Palsy Research and Education Foundation 237-71 and the Meadowbrook Medical Research and Education Foundation, Inc. Received
for
Accepted
December
publication
October
31, 1974.
18, 1974.
Materials
Reprint requests: Leon I. Mann, M.D., Professor and Co-Chairman, Department of Obstetrics and Gynecology, State University of New York at Stony Brook; Director, Department of Obstetrics and Gynecology, Nassau County Medical Center, 2201 Hempstead Turnpike, East Meadow, New York 11554.
and
methods
Ten Dorset ewes with dated gestations from 121 to 138 days (term is approximately 145 days) were used for these experiments. The ewes were prepared for operation by withholding food for 24 hours and water for 12 hours. Progesterone in oil (Proluton 845
846
Mann
August 1. lllifi . Am. J. Ohstrt. Gynrrol.
et al.
15cclkg/Zhrs. 0.35t J 0.30-E i 5 2
O.25-z
z 5
r:o9443
0.20-
y :0.0136
L
+o
8743x
0.15-
0.00
l
000
Felol I 0.05
Carottd 1 0.10
Artery I 0.15
I 0.20 ETOH
I 0.25
Shering Corporation, Union, New Jersey) 150 mg., was administered intramuscularly twice daily for 2 days before and on the day of operation. Anesthesia was induced with halothane (Fluothane, Ayerst Labs., Division American Home Products Corporation, New York, New York) 2 to 4 per cent, delivered by nose cone, and anesthesia was maintained with a 0.6 to 1.2 per cent halothane-30 per cent oxygen-balance nitrogen mixture delivered by means of a cuffed endotracheal tube, a positivenegative respirator (Bird, Palms Spring, California) via an anesthetic apparatus. Polyvinyl catheters were placed into the maternal jugular vein and maternal ventral aorta by means of routine surgical cut-down procedure over the neck and femoral triangle, respectively. The maternal jugular catheter was used for maternal infusion while the distal ventral aorta catheter was connected to the three-way stopcock and a pressure transducer (P23DBStatham Instruments, Inc., Oxnard, California) for intermittent blood sampling and continuous blood pressure recordings. The fetal head was delivered through an abdominal and myometrial incision and placed into a stereotaxic device (David Kopf Instruments, Dejunga, California) that was modified for sheep. The technique of catheterization of the carotid artery and
I 0.35
I 0.40
(g%)
Fig. 1. Correlation
of blood alcohol concentrations during maternal infusion of 15 C.C. of 9.75 per total body weight for 2 hours.
I 0.30
cent
in the fetal carotid alcohol-dextrose
artery solution
and sagittal vein per kilogram of
sagittal vein has been previously presented in detail.5 A perivascular ultrasonic flow transducer (Ward Associates, LaJolla, California) was placed high on the carotid artery after tributaries had been ligated. The output of the flow transducer was calibrated for volume flow in vivo during the experiment by the technique that has been previously described.” Pressure in the cerebral vessels was monitored continuously by a pressure transducer. Solder ball electrodes were placed extradurally by the technique described previously’ and continuous bipolar recordings of the eletroencephalogram (EEG) were obtained. All electrophysiologic parameters were displayed by direct write-out on an eight-channel dynograph (Type RM Beckman Instruments Inc., Fullerton, California) through appropriate couplers. Each ewe was weighed prior to the experiment and a total dose of 15 C.C. per kilogram of total body weight of a 9.75 per cent solution of alcohol in a 5 per cent dextrose solution was infused for either 1 or 2 hours. Blood samples were drawn simultaneously from the maternal ventral aorta (MA), fetal carotid artery (FA) , and fetal sagittal vein (SV) at 30 minute intervals throughout the 2 hour infusion and at 15 minute intervals during recovery or as long as the fetus was viable. A portion of the blood sample was deproteinated immediately with cold
Volume Number
122 7
Alcohol
on
fetal
cerebral
function
and
metabolism
847
Ewe # 122 15cclKg/2hrs. Gest. Age 126 days
HR BP ---
Fig. 2. Continuous
heart rate (HR): blood pressure (BP), blood flow (BF), and resistance (Resist.) measurement during and following maternal infusion of 15 C.C. of 9.75 per cent alcohol-dextrose solution per kilogram for 2 hours in a single experiment. Gestational age was 126 days.
perchloric acid, frozen, and determined at a latter date for glucose and lactate by enzymatic methods (Boehringer Mannheim Corp., New York? New York). A part of the remaining portion of the blood sample was determined immediately for pH, Pco?, and PO, on an IL1 13 pH-Blood Gas Analyzer. Blood alcohol concentration was determined by gas chromatographic method.’ Oxygen content was calculated from the determination of the per cent saturation of hemoglobin with oxygen and the concentration of hemoglobin as determined by an IL Co-oximeter. Base excess (in milliequivalents per liter) was calculated from a convenient nomogram. The glucose/oxygen utilization ratio was calculated from the formula 6 x A-V A-V
difference, difference,
glucose oxygen
(mM./L.) (mM./L.)
’
Fetal heart rate was calculated from the carotid pressure tracing. Cerebral perfusion pressure was calculated as mean carotid artery pressure (diastolic pressure plus one-third pulse pressure) minus sagittal vein pressure. Group values are expressed as mean z standard errors. Statistical significance of changes from baseline were calculated by Student’s t test. Significance is presented in terms of p values.
Results As the results were statistically similar in both the 1 and 2 hour infusion periods and differed only in terms of the time of onset, the six experiments wherein a 2 hour infusion was utilized have been grouped and statistically evaluated and presented here. Fetal alcohol concentration and cerebral A-V difference. The mean fetal concentration of alcohol in the carotid artery was 0.177 + 0.009 Gm. per 100 ml. at 90 minutes, 0.222 ? 0.019 Gm. per 100 ml. at 120 minutes, and 0.180 + 0.011 Gm. per 100 ml. at 150 minutes. No significant cerebral A-V difference in alcohol concentration could be demonstrated during or following the infusion. The correlation of the concentrations of alcohol in the fetal carotid artery and fetal sagittal vein is shown in Fig. 1 (p < 0.001) . This correlation shows almost a linear relationship and the mean A-V differences were not significantly different from zero. Fetal cerebral cardiovascular observations. Fetal heart rate showed a slight but insignificant tachycardia through the infusion and into the postinfusion period (Table I). Blood pressure decreased during the infusion period but reached significance only in the 30 minute postinfusion period. Cerebral resistance had decreased significantly by 90 minutes
848
Mann
et
ai.
Table I. Fetal cerebral cardiovascular per kilogram per 2 hours Baseline
and metabolic
/
90 min.
/
observations
P
/
following
220 min.
alcohol
1
P
infusion,
/
150
15 (’ :‘.
miff.
~
P
Heart rate (beats/ min. ) Blood pressure (mm. Hg) Resistance (mm./I,./ min.) Blood flow (ml./100 Gm./min.) O? content (FA) (vol. %) (A-V)-0, (mM./L.) Q-0, (ml./100 Gm./ min.) Glucose (FA) (mg./ 100 ml.) (A-V)-glucose (mg./ 100 ml.) Q-glucose (mg./lOO Gm./min.) Glucose/Or ratio (A-V) -lactate (mg./ 100 ml.)
141 41.72
2 9.05 2
2.39
164
36.28
+
9.45
N.S.
t
2.88
N.S.
36.86
k 10.65
N.S
149
2
-c 2.66
N.S.
k 91.5
< 0.01
519.3 + 129.8
< (1.025
< 0.025
141.07 -c ‘7.63
<: 0.05
35.41 -’
6.97 3.17
N.S. CC fl,O>
* 87.1
629.1
+
3.49
11 1.62 2 113.41 < 0.1)125
9.52 2 1.51 k
1.17 0.23
7.93’ 1.67 2
1.13 0.27
N.S. N.S.
7.98 t 1.10 1.77 % 0.39
N.S. N.S.
5.39 _+ 0.73 < 0.01 1.no 2 0.39 N.S.
3.14 t- 0.53
3.50 2
0.56
N.S.
4.50 5
N.S
2.51 +
t
4.41
< O.f)005
934.1 82.43
11.82
?
2.00
53.78
5 75.2
154
< o.n125
554.8
129.05 + 17.59
0.95
69.83 + 4.02
<
0.0005
65.62
k
0.75
N.S.
6.14
< fl.0005
3.76?
0.71
8.06 k
1.62
< 0.025
8.55 2
1.53
< 0.01
4.86 +
1.39
N.S.
3.53 2 0.83 ?
0.73 0.07
7.12 -c 0.90 1.61 + 0.18
< 0.01
9.83 + 1.86 1.98 T! 0.39
< 0.01 < 0.01
5.33 i
0.92
N.S.
1.98’
0.75
N.S.
0.71
N.S.
-1.54
+ 0.35
-1.26
k
< 0.0025
0.41
and remained significantly decreased throughout the infusion and postinfusion period. Cerebral blood flow was significantly increased at 90 minutes’ infusion as the fall in resistance was proportionately greater than the decrease in blood pressure (Table I and Fig. 2). In the experiment shown in Fig. 2, 1 hour after infusion, when the pH was 6.950, cerebral resistance had returned to baseline value while blood pressure and therefore cerebral blood flow was then 25 per cent below the baseline value. Heart rate in this experiment, which had been 175 beats per minute prior to alcohol infusion, was 150 beats per minute 1 hour after infusion, or 15 per cent below the baseline value. Fetal cerebral metabolic observations. Oxygen tension and oxygen content in the carotid artery as well as the cerebral A-V difference in oxygen and the cerebral metabolic rate for oxygen remained essentially unchanged during the infusion and postinfusion periods. Oxygen content in the carotid artery was significantly decreased at 30 minutes after infusion. Glucose concentration in the carotid artery was significantly elevated from baseline throughout the experiment as a result of the continued infusion of glucose into the maternal circulation and placental transport to the fetus. The cerebral A-V difference in glucose concentration was increased significantly during the infusion period but returned to insignifi-
N.S.
-
-1.60
-t
0.68
N.S.
-2.30
*
cant values by 30 minutes after infusion. The cerebral metabolic rate for glucose was similarly significantly elevated at 90 minutes’ and 120 minutes’ infusion but insignificant 30 minutes after infusion. The glucose/oxygen utilization ratio was increased from 0.83 f 0.07 to 1.61 i 0.18 at 90 minutes’ infusion (p < 0.0025) and remained elevated through the infusion period. At 30 minutes after infusion the glucose/oxygen utilization ratio was still increased but so variable that the mean was insignificantly different from baseline. The cerebral A-V difference in lactate concentration was unchanged during and following the infusion of alcohol and did not significantly differ from zero. Fetal EEG observations. The changes observed in the frequency and amplitude characteristics of the fetal EEG were fairly consistent regardless of a 1 or 2 hour infusion of alcohol or the gestational age of the fetus (Fig. 3). During the first 60 to 90 minutes of alcohol infusion the EEG showed a decrease in amplitude, a decrease in the frequency of the slow wave patterns, and the onset of a predominant frequency pattern in the -1 to 8 cycles per second range. Further increase in the concentration of alcohol to the peak value at 2 hours resulted in a further decrease in over-all amplitude and a general slowing of the record. The EEG failed to recover during the postinfusion period and as the fetal acidosis vj.orsened the EEG became isoelectric (flat) in
Volume Number
12? 7
Alcohol
on fetal
cerebral
function
and
metabolism
849
Fig. 3. EEG records at intervals during and following the maternal infusion of 15 C.C. of 9.75 per cent alcohol-dextrose per kilogram for 2 hours in a single experiment. Gestational age was 126 days. ETOH, blood alcohol concentration; HR, heart rate.
several experiments. The EEG was never noted to f u 11y recover to its baseline appearance in any experiment that could be followed long enough for reliable observations to be made. Comment
The rapid diffusion of alcohol across the placental membrane from mother to fetus is consistent with the small molecular size and weak properties of dissociation and polarization of alcohol. Similarly, it could be expected that alcohol would be rapidly and readily diffusible throughout all body fluids and tissues, including the central nervous system. A posi-
tive A-V difference across any organ would depend upon the ability of that organ to metabolize alcohol. The absence of a significant A-V difference across the fetal brain in these experiments is consistent with the observation that only small amounts of alcohol dehydrogenase (ADH) as well as aldehyde dehydrogenase are present in the brain.” The amount of brain ADH activity has been estimated to amount to only about l/3,700 of that found in the liver, which is the major organ of metabolism of alcohol.‘” It would appear that significant oxidation of alcohol does not normally occur in the brain. The changes in acid-base balance that occur in
850
Mann
et al.
both the adult and fetal animal following the infusion of alcohol have been presented and discussed previously.” A metabolic acidosis develops as a result of the hyperlactacidemia that occurs by the reduction of pyruvate to lactate following an increase in the DPNH/DPN ratio as alcohol is degraded to acetaldehyde by the ADH system. The increase in acetaldehyde, although difficult to recover from blood determinations, is considered responsible for the tachycardia and peripheral vasodilatation that are seen following alcohol infusion. In the present experiments it was noted that cerebral blood flow increased as a result of a more significant fall in resistance than in blood pressure. The significant marked fall in cerebral resistance most likely represents the autoregulatory mechanism to maintain cerebral blood flow in the face of a fall in perfusion pressure.” Alternatively, the fall in resistance might have occurred secondarily to the vasodilatory effect of alcohol. The decrease in blood flow and increase in resistance that occurred during the postinfusion period in a single experiment, shown in Fig. 2, might be explained on the basis of the severe metabolic acidosis that developed. That the fetus remained well oxygenated during the alcohol infusion and postinfusion periods was demonstrated by the insignificant change in the A-V difference in oxygen content and the cerebral metabolic rate for oxygen. These values are similar to those reported previously by ourselves and others.‘“, ” An Y interpretation of the effect of alcohol on fetal glucose metabolism during these experiments is hazardous in view of the infusion of glucose with the alcohol. The increase in glucose concentration during the period of infusion could be expected to increase the concentration of glucose within the central nervous system, as we have previously reported a linear relationship between blood and cerebral spinal fluid glucose concentration (range, 5 to 28 mg. per 100 ml., r = 0.7842; p < 0.01) .lh The increase in the A-V concentration difference of glucose, the cerebral metabolic rate for glucose, and the glucose-oxygen utilization ratio suggests that glucose was taken up by the brain in amounts that could not be explained by aerobic metabolism. The failure to observe any increase in the A-V difference for lactate, pyruvate, or CO, would tend to confirm this suggestion. While the precise explanation for this observed enhancement of glucose uptake by the brain during alcohol is not readily apparent, it has been observed that gluconeogenesis is increased in the well-fed individual
given alcohol. lG Fasted individuals, however, have been reported to become hypoglycemic followulr alcohol infusion due to a decrease in gluconeogenesis. Alternatively, the situation might have existed in these experiments where a high concentration of glucose stimulated insulin release that w’as potentiated by the effect of alcohol and resulted in increased uptake. The exact mechanism requires further investigation. The effect of alcohol on fetal brain functioning in terms of the EEG, as well as the other neurophysiologic parameters such as evoked cortical responses, has been studied extensively both in acute alcohol infusion and in chronic alcoholics.l’-“u While no specific EEG pattern has been agreed upon, the consensus of opinion suggests that a slowing of the alpha rhythm is characteristically found following alcohol infusion. In a series of experiments where a drip infusion of 100 Gm. of ethanol in solution was infused, the first detectable change to appear was a slowing in the alpha rhythm which was followed at a slightly higher dosage by a reduction in amplitude. It has been further observed that the peak change in the EEG does not occur until the blood-alcohol level begins to decline. Isoelectric (flat) EEG’s have been observed in adult human subjects and animals at very high blood-alcohol concentrations. While it is difficult to interpret from adult human or adult animal studies to the sheep fetus in utero, the results presented here are not inconsistent with the general findings presented previously. An over-all decrease in amplitude and a slowing of the record leading to isoelectricity on occasion were observed in these fetal sheep experiments. Whether these EEG changes were the result of the direct effect of alcohol and/or the effect of the severe fetal acidosis that developed is not clear. Similar, but not identical, EEG changes have been observed and presented by us previously during exogenously induced fetal acidosis.“” It would seem reasonable to suggest that both alcohol and the acidosis are functioning in an additive fashion in the impairment of brain function as reflected in the EEG. The cortical or subcortical structural-functional relationships could not be elucidated from these experiments. That the central nervous system is depressed following alcohol infusion would seem to be a clearly warranted conclusion from these experiments. From the observations presented here and by those of others,’ an acidosis should be expected to develop toward the end of a 2 hour infusion of alcohol and
Volume 122 Number7
during the postinfusion period. These observations would indicate a strong need for close fetal monitoring in the human subject, particularly following the loading dose of alcohol. The pediatrician should be alerted to the poqsibility of a depressed neonate due to both peripheral and central factors. The perinatal team should be equipped to administer resuscitative measures expeditiously in these unsuccessful attempts at inhibiting premature labor with alcohol infusion. The potential deleterious effect of these brief periods of central nervous system depression
Alcohol
on fetal
cerebral
function
and
metabolism
851
and acidosis on eventual brain function in both the successful and unsuccessful cases of alcohol infusion must await further studies. The authors wish to acknowledge the cooperation and assistance of Mr. Peter Lorenzo and staff of the Animal Research Division of the Nassau County Medical Center in the performance of these experiments, and Dr. J. Bidouset and Mr. Tom Manning of the Toxicology Division, Nassau County Medical Examiner’s Office, for the performance of the alcohol determinations.
REFERENCES
Fuchs, F., Fuchs, A.-R., Poblete, V. F., Jr., and Risk, A.: AM. J. OBSTET. GYNECOL. 99:627, 1967. Dilts, P. V., Jr.: AM. J. OBSTET. GYNECOL. 107: 1018, 1970. Dilts, P. V., Jr.: AM. J. OBSTET. GYNECOL. 108: 221, 1970. Horiguchi, T., Suzuki, K., Comas-Urrutia, A. C., Mueller-Heubach, E., Boyer-Milic, A. M., Baratz, R. A., Morishima, H. D., James, L. S., and Adamsons,K.: AM.J. OBSTET.GYNECOL. 109:910, 1971. 5. Mann, L. I., Carmichael, A., and Duchin, S.: AM. J. OBSTET. GYNECOL. 114:549,1972. 6. Mann, L. I.: Exp. Neurol. 26: 136, 1970. L. I.: Am. 1. Phvsiol. 218: 1453. 1970. 7. Mann. 8. Goldbium, L. R., grid Schlaegel, E. L.: J. Forensic Sci. 9: 63, 1964. 9. Raskin, N. H.: Ann. N. Y. Acad. Sci. 215: 49, 1973. 10. Seixas, F. A.: Ann. N. Y. Acad. Sci. 215: 10, 1973. 11. Mann, L. I., Bhakthavathsalan, A., Liu, M., and Makowski, P.: .4~. J. OBSTET. GYNECOL. 122: 837, 1975. 12. Rurves, M. J., and James, I. M.: Circ. Res. 25:651, 1969. 13. Mann, L. I., Duchin, S., Halverstram, J., Mastran-
14.
15. 16. 17.
18. 19.
tonio, J., Weiss, R. R., and Schulman, J.: AM. J. OBSTET.GYNECOL. 117:45, 1973. Makowski, E. L., Schneider, J. M., Tsoulos, N. G., Colwill, J. R., Battaglia, F. C., and Meschia, G.: AM. J. OBSTET.GYNECOL. 114:292, 1972. Mann, L. I,, Carmichael, A., and Duchin, S.: AM. J. OBSTET.GYNECOL. 114:549, 1972. Kalkhoff, R. K., and Kim, H-J.: Diabetes 22: 372, 1973. Begleiter, H., and Platz, A.: In Kissim, B., and Begleiter, H., editors: The Biology of Alcoholism, New York, 1972. ’ Plenum Publishing Comoanv. . ,, vol. 2, pp. 2931343. 215: 303, 1973. Naitoh, P.: Ann. N. Y. Acad. Med. Davis, P. A., Gibbs, F. A., Davis, H., Jetter, W. W., and Trowbridee. L. S.: 0. 1. Stud. Alcoholism 1: 626, 1941. - ’ Dolce, G., and Decker, H.: Res. Comm. in Chem. Pathol. Pharmacol. 3: 523, 1972. Katani, K.: Bull. Osaka Med. School 12 (Suppl.) : 11, 1965. Mann, L. I., Solomon, G., Carmichael, A., and Duchin, S.: AM. J. OBSTET. GYNECOL. 111: 353, 1971. -
20. 21. 22.
”
I.
MANN,
AMRUTHA
M.D.
BHAKTHAVATHSALAN,
MAIDA
LIU,
PHILIP
MAKOWSKI,
East Meadow
M.D.
B.S. M.D.
and Stony
Brook,
New
York
The effect of maternal alcohol infusion on fetal cerebral function in terms of the electroencephalogram (EEG) and fetal brain metabolism was studied in 10 fetal sheep experiments. A 9.75 per cent alcohol-dextrose solution was infused at the rate of 15 CL. per kilogram of maternal weight for 1 or 2 hours. Fetal cerebral uptake of oxygen was unaffected. Blood flow was significantly increased as a result of a greater decrease in resistance than decrease in blood pressure. The cerebral uptake of glucose and the glucose-oxygen utilization ratio were significantly increased. The EEG showed a decrease in amplitute and slowing of the dominant rhythm as the blood alcohol concentration increased and became isoelectric on occasion during the postinfusion period associated with a severe fetal acidosis.
W H I L E T H E maternal infusion of alcohol has been shown to be effective in inhibiting premature labor in a statistically significant number of cases,r the question of what effect the infusion of alcohol has on the cardiovascular, metabolic, and acid-base status of the fetus has only recently been investigated and reported in the literature.z-4 In an acute study on fetal sheep Dilts reported no significant alteration in fetal metabolism and acid-base balance during alcohol infusion, although placental transport of oxygen and fetal oxygenation were impaired during experiments conducted under pentobarbital
anesthesia. Horiguchi and associates,4 in a semiacute monkey preparation, reported a successful inhibition of spontaneous or induced labor prior to term that was associated with a significant fetal tachycardia, fall in blood pressure, and acidosis. An unsubstantiated clinical impression exists that premature newborn infants delivered following an unsuccessful attempt with alcohol to inhibit the premature labor are more severely depressed at birth, require vigorous resuscitative measures, and have a higher incidence of hyaline membrane disease than premature infants delivered without alcohol infusion. In a previous report we confirmed the observations of Horiguchi by showing a significant fetal acidosis during and following the infusion of alcohol in an acute fetal sheep preparation. The results of the direct effect of alcohol and/or the associated acidosis on fetal brain function and metabolism are presented here.
From the Department of Obstetrics and Gynecology, Nassau County Medical Center, East Meadow, and the Health Sciences Center, State University of New York at Stony Brook. Supported in part by a grant from the United Cerebral Palsy Research and Education Foundation 237-71 and the Meadowbrook Medical Research and Education Foundation, Inc. Received
for
Accepted
December
publication
October
31, 1974.
18, 1974.
Materials
Reprint requests: Leon I. Mann, M.D., Professor and Co-Chairman, Department of Obstetrics and Gynecology, State University of New York at Stony Brook; Director, Department of Obstetrics and Gynecology, Nassau County Medical Center, 2201 Hempstead Turnpike, East Meadow, New York 11554.
and
methods
Ten Dorset ewes with dated gestations from 121 to 138 days (term is approximately 145 days) were used for these experiments. The ewes were prepared for operation by withholding food for 24 hours and water for 12 hours. Progesterone in oil (Proluton 845
846
Mann
August 1. lllifi . Am. J. Ohstrt. Gynrrol.
et al.
15cclkg/Zhrs. 0.35t J 0.30-E i 5 2
O.25-z
z 5
r:o9443
0.20-
y :0.0136
L
+o
8743x
0.15-
0.00
l
000
Felol I 0.05
Carottd 1 0.10
Artery I 0.15
I 0.20 ETOH
I 0.25
Shering Corporation, Union, New Jersey) 150 mg., was administered intramuscularly twice daily for 2 days before and on the day of operation. Anesthesia was induced with halothane (Fluothane, Ayerst Labs., Division American Home Products Corporation, New York, New York) 2 to 4 per cent, delivered by nose cone, and anesthesia was maintained with a 0.6 to 1.2 per cent halothane-30 per cent oxygen-balance nitrogen mixture delivered by means of a cuffed endotracheal tube, a positivenegative respirator (Bird, Palms Spring, California) via an anesthetic apparatus. Polyvinyl catheters were placed into the maternal jugular vein and maternal ventral aorta by means of routine surgical cut-down procedure over the neck and femoral triangle, respectively. The maternal jugular catheter was used for maternal infusion while the distal ventral aorta catheter was connected to the three-way stopcock and a pressure transducer (P23DBStatham Instruments, Inc., Oxnard, California) for intermittent blood sampling and continuous blood pressure recordings. The fetal head was delivered through an abdominal and myometrial incision and placed into a stereotaxic device (David Kopf Instruments, Dejunga, California) that was modified for sheep. The technique of catheterization of the carotid artery and
I 0.35
I 0.40
(g%)
Fig. 1. Correlation
of blood alcohol concentrations during maternal infusion of 15 C.C. of 9.75 per total body weight for 2 hours.
I 0.30
cent
in the fetal carotid alcohol-dextrose
artery solution
and sagittal vein per kilogram of
sagittal vein has been previously presented in detail.5 A perivascular ultrasonic flow transducer (Ward Associates, LaJolla, California) was placed high on the carotid artery after tributaries had been ligated. The output of the flow transducer was calibrated for volume flow in vivo during the experiment by the technique that has been previously described.” Pressure in the cerebral vessels was monitored continuously by a pressure transducer. Solder ball electrodes were placed extradurally by the technique described previously’ and continuous bipolar recordings of the eletroencephalogram (EEG) were obtained. All electrophysiologic parameters were displayed by direct write-out on an eight-channel dynograph (Type RM Beckman Instruments Inc., Fullerton, California) through appropriate couplers. Each ewe was weighed prior to the experiment and a total dose of 15 C.C. per kilogram of total body weight of a 9.75 per cent solution of alcohol in a 5 per cent dextrose solution was infused for either 1 or 2 hours. Blood samples were drawn simultaneously from the maternal ventral aorta (MA), fetal carotid artery (FA) , and fetal sagittal vein (SV) at 30 minute intervals throughout the 2 hour infusion and at 15 minute intervals during recovery or as long as the fetus was viable. A portion of the blood sample was deproteinated immediately with cold
Volume Number
122 7
Alcohol
on
fetal
cerebral
function
and
metabolism
847
Ewe # 122 15cclKg/2hrs. Gest. Age 126 days
HR BP ---
Fig. 2. Continuous
heart rate (HR): blood pressure (BP), blood flow (BF), and resistance (Resist.) measurement during and following maternal infusion of 15 C.C. of 9.75 per cent alcohol-dextrose solution per kilogram for 2 hours in a single experiment. Gestational age was 126 days.
perchloric acid, frozen, and determined at a latter date for glucose and lactate by enzymatic methods (Boehringer Mannheim Corp., New York? New York). A part of the remaining portion of the blood sample was determined immediately for pH, Pco?, and PO, on an IL1 13 pH-Blood Gas Analyzer. Blood alcohol concentration was determined by gas chromatographic method.’ Oxygen content was calculated from the determination of the per cent saturation of hemoglobin with oxygen and the concentration of hemoglobin as determined by an IL Co-oximeter. Base excess (in milliequivalents per liter) was calculated from a convenient nomogram. The glucose/oxygen utilization ratio was calculated from the formula 6 x A-V A-V
difference, difference,
glucose oxygen
(mM./L.) (mM./L.)
’
Fetal heart rate was calculated from the carotid pressure tracing. Cerebral perfusion pressure was calculated as mean carotid artery pressure (diastolic pressure plus one-third pulse pressure) minus sagittal vein pressure. Group values are expressed as mean z standard errors. Statistical significance of changes from baseline were calculated by Student’s t test. Significance is presented in terms of p values.
Results As the results were statistically similar in both the 1 and 2 hour infusion periods and differed only in terms of the time of onset, the six experiments wherein a 2 hour infusion was utilized have been grouped and statistically evaluated and presented here. Fetal alcohol concentration and cerebral A-V difference. The mean fetal concentration of alcohol in the carotid artery was 0.177 + 0.009 Gm. per 100 ml. at 90 minutes, 0.222 ? 0.019 Gm. per 100 ml. at 120 minutes, and 0.180 + 0.011 Gm. per 100 ml. at 150 minutes. No significant cerebral A-V difference in alcohol concentration could be demonstrated during or following the infusion. The correlation of the concentrations of alcohol in the fetal carotid artery and fetal sagittal vein is shown in Fig. 1 (p < 0.001) . This correlation shows almost a linear relationship and the mean A-V differences were not significantly different from zero. Fetal cerebral cardiovascular observations. Fetal heart rate showed a slight but insignificant tachycardia through the infusion and into the postinfusion period (Table I). Blood pressure decreased during the infusion period but reached significance only in the 30 minute postinfusion period. Cerebral resistance had decreased significantly by 90 minutes
848
Mann
et
ai.
Table I. Fetal cerebral cardiovascular per kilogram per 2 hours Baseline
and metabolic
/
90 min.
/
observations
P
/
following
220 min.
alcohol
1
P
infusion,
/
150
15 (’ :‘.
miff.
~
P
Heart rate (beats/ min. ) Blood pressure (mm. Hg) Resistance (mm./I,./ min.) Blood flow (ml./100 Gm./min.) O? content (FA) (vol. %) (A-V)-0, (mM./L.) Q-0, (ml./100 Gm./ min.) Glucose (FA) (mg./ 100 ml.) (A-V)-glucose (mg./ 100 ml.) Q-glucose (mg./lOO Gm./min.) Glucose/Or ratio (A-V) -lactate (mg./ 100 ml.)
141 41.72
2 9.05 2
2.39
164
36.28
+
9.45
N.S.
t
2.88
N.S.
36.86
k 10.65
N.S
149
2
-c 2.66
N.S.
k 91.5
< 0.01
519.3 + 129.8
< (1.025
< 0.025
141.07 -c ‘7.63
<: 0.05
35.41 -’
6.97 3.17
N.S. CC fl,O>
* 87.1
629.1
+
3.49
11 1.62 2 113.41 < 0.1)125
9.52 2 1.51 k
1.17 0.23
7.93’ 1.67 2
1.13 0.27
N.S. N.S.
7.98 t 1.10 1.77 % 0.39
N.S. N.S.
5.39 _+ 0.73 < 0.01 1.no 2 0.39 N.S.
3.14 t- 0.53
3.50 2
0.56
N.S.
4.50 5
N.S
2.51 +
t
4.41
< O.f)005
934.1 82.43
11.82
?
2.00
53.78
5 75.2
154
< o.n125
554.8
129.05 + 17.59
0.95
69.83 + 4.02
<
0.0005
65.62
k
0.75
N.S.
6.14
< fl.0005
3.76?
0.71
8.06 k
1.62
< 0.025
8.55 2
1.53
< 0.01
4.86 +
1.39
N.S.
3.53 2 0.83 ?
0.73 0.07
7.12 -c 0.90 1.61 + 0.18
< 0.01
9.83 + 1.86 1.98 T! 0.39
< 0.01 < 0.01
5.33 i
0.92
N.S.
1.98’
0.75
N.S.
0.71
N.S.
-1.54
+ 0.35
-1.26
k
< 0.0025
0.41
and remained significantly decreased throughout the infusion and postinfusion period. Cerebral blood flow was significantly increased at 90 minutes’ infusion as the fall in resistance was proportionately greater than the decrease in blood pressure (Table I and Fig. 2). In the experiment shown in Fig. 2, 1 hour after infusion, when the pH was 6.950, cerebral resistance had returned to baseline value while blood pressure and therefore cerebral blood flow was then 25 per cent below the baseline value. Heart rate in this experiment, which had been 175 beats per minute prior to alcohol infusion, was 150 beats per minute 1 hour after infusion, or 15 per cent below the baseline value. Fetal cerebral metabolic observations. Oxygen tension and oxygen content in the carotid artery as well as the cerebral A-V difference in oxygen and the cerebral metabolic rate for oxygen remained essentially unchanged during the infusion and postinfusion periods. Oxygen content in the carotid artery was significantly decreased at 30 minutes after infusion. Glucose concentration in the carotid artery was significantly elevated from baseline throughout the experiment as a result of the continued infusion of glucose into the maternal circulation and placental transport to the fetus. The cerebral A-V difference in glucose concentration was increased significantly during the infusion period but returned to insignifi-
N.S.
-
-1.60
-t
0.68
N.S.
-2.30
*
cant values by 30 minutes after infusion. The cerebral metabolic rate for glucose was similarly significantly elevated at 90 minutes’ and 120 minutes’ infusion but insignificant 30 minutes after infusion. The glucose/oxygen utilization ratio was increased from 0.83 f 0.07 to 1.61 i 0.18 at 90 minutes’ infusion (p < 0.0025) and remained elevated through the infusion period. At 30 minutes after infusion the glucose/oxygen utilization ratio was still increased but so variable that the mean was insignificantly different from baseline. The cerebral A-V difference in lactate concentration was unchanged during and following the infusion of alcohol and did not significantly differ from zero. Fetal EEG observations. The changes observed in the frequency and amplitude characteristics of the fetal EEG were fairly consistent regardless of a 1 or 2 hour infusion of alcohol or the gestational age of the fetus (Fig. 3). During the first 60 to 90 minutes of alcohol infusion the EEG showed a decrease in amplitude, a decrease in the frequency of the slow wave patterns, and the onset of a predominant frequency pattern in the -1 to 8 cycles per second range. Further increase in the concentration of alcohol to the peak value at 2 hours resulted in a further decrease in over-all amplitude and a general slowing of the record. The EEG failed to recover during the postinfusion period and as the fetal acidosis vj.orsened the EEG became isoelectric (flat) in
Volume Number
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Alcohol
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Fig. 3. EEG records at intervals during and following the maternal infusion of 15 C.C. of 9.75 per cent alcohol-dextrose per kilogram for 2 hours in a single experiment. Gestational age was 126 days. ETOH, blood alcohol concentration; HR, heart rate.
several experiments. The EEG was never noted to f u 11y recover to its baseline appearance in any experiment that could be followed long enough for reliable observations to be made. Comment
The rapid diffusion of alcohol across the placental membrane from mother to fetus is consistent with the small molecular size and weak properties of dissociation and polarization of alcohol. Similarly, it could be expected that alcohol would be rapidly and readily diffusible throughout all body fluids and tissues, including the central nervous system. A posi-
tive A-V difference across any organ would depend upon the ability of that organ to metabolize alcohol. The absence of a significant A-V difference across the fetal brain in these experiments is consistent with the observation that only small amounts of alcohol dehydrogenase (ADH) as well as aldehyde dehydrogenase are present in the brain.” The amount of brain ADH activity has been estimated to amount to only about l/3,700 of that found in the liver, which is the major organ of metabolism of alcohol.‘” It would appear that significant oxidation of alcohol does not normally occur in the brain. The changes in acid-base balance that occur in
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et al.
both the adult and fetal animal following the infusion of alcohol have been presented and discussed previously.” A metabolic acidosis develops as a result of the hyperlactacidemia that occurs by the reduction of pyruvate to lactate following an increase in the DPNH/DPN ratio as alcohol is degraded to acetaldehyde by the ADH system. The increase in acetaldehyde, although difficult to recover from blood determinations, is considered responsible for the tachycardia and peripheral vasodilatation that are seen following alcohol infusion. In the present experiments it was noted that cerebral blood flow increased as a result of a more significant fall in resistance than in blood pressure. The significant marked fall in cerebral resistance most likely represents the autoregulatory mechanism to maintain cerebral blood flow in the face of a fall in perfusion pressure.” Alternatively, the fall in resistance might have occurred secondarily to the vasodilatory effect of alcohol. The decrease in blood flow and increase in resistance that occurred during the postinfusion period in a single experiment, shown in Fig. 2, might be explained on the basis of the severe metabolic acidosis that developed. That the fetus remained well oxygenated during the alcohol infusion and postinfusion periods was demonstrated by the insignificant change in the A-V difference in oxygen content and the cerebral metabolic rate for oxygen. These values are similar to those reported previously by ourselves and others.‘“, ” An Y interpretation of the effect of alcohol on fetal glucose metabolism during these experiments is hazardous in view of the infusion of glucose with the alcohol. The increase in glucose concentration during the period of infusion could be expected to increase the concentration of glucose within the central nervous system, as we have previously reported a linear relationship between blood and cerebral spinal fluid glucose concentration (range, 5 to 28 mg. per 100 ml., r = 0.7842; p < 0.01) .lh The increase in the A-V concentration difference of glucose, the cerebral metabolic rate for glucose, and the glucose-oxygen utilization ratio suggests that glucose was taken up by the brain in amounts that could not be explained by aerobic metabolism. The failure to observe any increase in the A-V difference for lactate, pyruvate, or CO, would tend to confirm this suggestion. While the precise explanation for this observed enhancement of glucose uptake by the brain during alcohol is not readily apparent, it has been observed that gluconeogenesis is increased in the well-fed individual
given alcohol. lG Fasted individuals, however, have been reported to become hypoglycemic followulr alcohol infusion due to a decrease in gluconeogenesis. Alternatively, the situation might have existed in these experiments where a high concentration of glucose stimulated insulin release that w’as potentiated by the effect of alcohol and resulted in increased uptake. The exact mechanism requires further investigation. The effect of alcohol on fetal brain functioning in terms of the EEG, as well as the other neurophysiologic parameters such as evoked cortical responses, has been studied extensively both in acute alcohol infusion and in chronic alcoholics.l’-“u While no specific EEG pattern has been agreed upon, the consensus of opinion suggests that a slowing of the alpha rhythm is characteristically found following alcohol infusion. In a series of experiments where a drip infusion of 100 Gm. of ethanol in solution was infused, the first detectable change to appear was a slowing in the alpha rhythm which was followed at a slightly higher dosage by a reduction in amplitude. It has been further observed that the peak change in the EEG does not occur until the blood-alcohol level begins to decline. Isoelectric (flat) EEG’s have been observed in adult human subjects and animals at very high blood-alcohol concentrations. While it is difficult to interpret from adult human or adult animal studies to the sheep fetus in utero, the results presented here are not inconsistent with the general findings presented previously. An over-all decrease in amplitude and a slowing of the record leading to isoelectricity on occasion were observed in these fetal sheep experiments. Whether these EEG changes were the result of the direct effect of alcohol and/or the effect of the severe fetal acidosis that developed is not clear. Similar, but not identical, EEG changes have been observed and presented by us previously during exogenously induced fetal acidosis.“” It would seem reasonable to suggest that both alcohol and the acidosis are functioning in an additive fashion in the impairment of brain function as reflected in the EEG. The cortical or subcortical structural-functional relationships could not be elucidated from these experiments. That the central nervous system is depressed following alcohol infusion would seem to be a clearly warranted conclusion from these experiments. From the observations presented here and by those of others,’ an acidosis should be expected to develop toward the end of a 2 hour infusion of alcohol and
Volume 122 Number7
during the postinfusion period. These observations would indicate a strong need for close fetal monitoring in the human subject, particularly following the loading dose of alcohol. The pediatrician should be alerted to the poqsibility of a depressed neonate due to both peripheral and central factors. The perinatal team should be equipped to administer resuscitative measures expeditiously in these unsuccessful attempts at inhibiting premature labor with alcohol infusion. The potential deleterious effect of these brief periods of central nervous system depression
Alcohol
on fetal
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and
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851
and acidosis on eventual brain function in both the successful and unsuccessful cases of alcohol infusion must await further studies. The authors wish to acknowledge the cooperation and assistance of Mr. Peter Lorenzo and staff of the Animal Research Division of the Nassau County Medical Center in the performance of these experiments, and Dr. J. Bidouset and Mr. Tom Manning of the Toxicology Division, Nassau County Medical Examiner’s Office, for the performance of the alcohol determinations.
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