Fetal catecholamine, cardiovascular, and neurobehavioral responses to cocaine Kenneth Chan, MD, P. Adam Dodd, MD, Linda Day, Linda Kullama, PhD, M. Gore Ervin, PhD, James Padbury, MD, and Michael G. Ross, MD
Torrance, California OBJECTIVE: Although maternal cocaine administration results in fetal cardiovascular and behavioral alterations, these responses have been attributed to hypoxia resulting from reduced uteroplacental blood flow. We studied the fetal catecholamine, cardiovascular, and neurobehavioral responses to direct fetal cocaine administration. STUDY DESIGN: Cardiovascular, electrocortical, and electroocular responses and plasma catecholamines were monitored in chronically catheterized fetal sheep (n = 7), 127 ± 2 days' gestation, during a control period and after intravenous fetal injections of cocaine 0.5 and 1.0 mg/kg. RESULTS: Intravenous cocaine caused prompt increases in fetal plasma norepinephrine (372 ± 73 to 531 ± 112 and 842 ± 233 pg/ml), epinephrine (27 ± 7 to 46 ± 13 and 49 ± 11 pg/ml), and systolic blood pressure (46 ± 2 to 53 ± 2 and 55 ± 2 mm Hg). Low-voltage electrocortical activity decreased from 61.7% ± 3.0% to 38.4% ± 3.9% in the first hour after the cocaine 0.5 mg/kg dose but recovered to baseline values during the second hour. After the cocaine 1.0 mg/kg dose, low-voltage electrocortical activity decreased to 40.7% ± 2.0% and did not recover thereafter. Fetal blood gas values did not change. CONCLUSION: Direct fetal cocaine administration increases fetal plasma catecholamine levels and fetal blood pressure and suppresses low-voltage electrocortical activity. Chronic cocaine exposure may hamper central nervous system maturation and alter postnatal development. (AM J QasTET GVNECOL 1992; 167: 1616-23.)
Key words: Cocaine, catecholamine, fetal neurobehavioral state Mounting evidence suggests that cocaine use during pregnancy may have consequences beyond such perinatal events as abruptio placentae, preterm labor, fetal distress, and intrauterine growth retardation. Indeed, a number of observations indicate that neurobehavioral and central cardiorespiratory regulatory development may be impaired in children exposed to cocaine in utero. Infants exposed to cocaine displayed increased tremulousness and startle responses and depressed consolability and interactive behavior. I In addition, an increased incidence of sudden infant death syndrome 2 and abnormal ventilatory patterns' has been reported among children whose mothers used cocaine during pregnancy. Animal studies also demonstrate neurobehavioral alterations. Rat pups exposed prenatally to cocaine were delayed in the development of the righting reflex: cliff From the Departments of Obstetrics and Gynecology and Pediatrics, Perinatal Research Laboratories, Harbor-University of California, Los Angeles Medical Center. Supported in part by grant R-413 from the United Cerebral Palsy Association. Presented in part at the Thirty-ninth Annual Meeting of the Society for Gynecologic Investigation, San Antonio, Texas, March 18-21, 1992. Reprint requests: Michael Ross, MD, Harbor-UCLA Medical Center, Research Building #1, 1124 W. Carson St., Torrance, CA 90502. 6/6/41933
avoidance, acoustic startle,5 and odor-milk association. 6 Behavioral alterations extending to adulthood also were noted in rats exposed to cocaine in utero, including impairment in spontaneous alterations, open field activity, water-maze performance, tail flick, and foot shock sensitivities. 7 Cocaine's effect on postnatal behavioral development may well be mediated through its action on catecholamine metabolism and sleep state regulation in utero. Cocaine blocks presynaptic catecholamine reuptake, leading to increased intrasynaptic norepinephrine concentration in central nervous system and peripheral sympathetic neurons. s An important neurotransmitter for sleep state regulation,9 norepinephrine is decreased in active sleep,lo the predominant behavioral state in fetal life. II. 12 Because active sleep state is accompanied by peak cerebral metabolism and blood flow and thus theorized to be vital for central nervous system maturation,I3 cocaine-induced suppression of fetal active sleep state may alter central nervous system maturation and postnatal behavioral development through chronically elevated central nervous system norepinephrine levels. Burchfield et al. 14 demonstrated decreased active sleep in fetal lambs given continuous intravenous cocaine infusions. However, neither the duration of the sleep state alteration nor the plasma catecholamine level was reported.
Volume 167 Number 6
Maternal cocaine administration results in significant ovine fetal cardiovascular effects in sheep. IS However, these effects may be secondary to cocaine-induced decreases in uteroplacental blood flow and resultant fetal hypoxemia. To avoid the vasoconstrictive effects of cocaine on uterine blood flow and resultant fetal hypoxia, we administered cocaine by direct fetal intravenous injections and sought to investigate fetal catecholamine, cardiovascular, and neurobehavioral responses. The results suggest an important role for norepinephrine in regulating cardiovascular and neurobehavioral states. Methods Surgical preparations. Seven time-bred ewes with singleton fetuses at 127 ± 2 days' gestation were studied. Animals were kept in individual metabolic cages and acclimated to an environment of alternating 12 hour light and dark cycles. Food and water were available ad libitum, except for withholding food 24 hours before surgery. The protocol was approved by the Harbor-UCLA Animal Use Committee and was in accord with American Association for Accreditation of Laboratory Animal Care and National Institutes of Health guidelines. The ewes were pre sedated with ketamine before endotracheal intubation and maintained during surgery on 1% to 2% isoflurane balanced with oxygen. Through a midline abdominal incision the uterus was exposed and the fetal head identified and exteriorized. Fetal electrocortical electrodes were inserted into the parietal dura, 16 and electroocular electrodes were sewn onto the periorbital tissue through incisions made above and below the orbit. Fetal and maternal polyethylene catheters were placed in the femoral artery and vein and advanced to the abdominal aorta and inferior vena cava, respectively. An intrauterine catheter (Corometrics Medical System, Wallingford, Conn.) was inserted for amniotic fluid pressure measurement. Antibiotics were administered in the immediate postoperative period and twice daily for 2 days. Gentamicin (S mg) and oxacillin (33 mg) were administered intravenously to the fetus, and gentamicin (72 mg), oxacillin (1 gm), and chloramphenicol (1 gm) were given to the ewe. Methods for the maintenance of catheters and protocols used for the sampling of blood have been detailed previously.17 All animals were allowed to recover for a minimum of 5 days before study. Protocol. On the day of study the unanesthesized animals were observed for a 2-hour control period (0 to 120 minutes), during which time fetal electrocortical and electroocular activity were recorded continuously and blood pressure and pulse were measured every 5 minutes. Duplicate fetal blood samples for measurement of hematocrit, arterial pH, P0 2 , Pco 2 , norepinephrine, epinephrine, and cocaine concentrations were
Fetal responses to cocaine
1617
withdrawn at 60 and 120 minutes. At the end of the control period an injection of cocaine 0.5 mg/kg in 2 ml of 0.9% saline solution was administered intravenously over 30 seconds. At time 240 minutes, a second injection of 1.0 mg/kg was similarly administered. The estimated fetal weights were derived on the basis of gestational age by the formula: Estimated fetal weight (kilograms) = 0.0961 x Gestational age (days) - 9.222S.18 The ewe and fetus were continuously monitored and fetal blood samples were drawn at 5, 15, 30, 60, and 120 minutes after each i~ection. Two maternal blood samples for measurement of hematocrit, arterial pH, P0 2 , Pc0 2 , catecholamine, and cocaine concentrations were taken during the control period and 15 and 120 minutes after each injection. All fetal blood samples were replaced with equivalent volumes of heparinized maternal blood drawn before the study. Maternal blood samples were replaced with equivalent volumes of saline solution. Fetal electrocortical activity. Fetal electrocortical activity was defined as either high or low voltage on the basis of visual inspection of the polygraph tracings. Results are expressed as percentage time spent during two 60-minute epochs in each study period (control, after first injection, and after second injection). Analytic techniques. Blood samples were transferred immediately to chilled test tubes. One milliliter of whole blood for catecholamine determination was added to tubes containing ethylene glycol-bis (l3-aminoethyl ether) N,N,N',N'-tetraacetic acid 4 mmol!L and reduced glutathione 3 mmol!L. Two milliliters of blood for cocaine and metabolite determination injected into 3 ml capacity Vacutainer tubes (No. 6471; Becton Dickinson, Rutherford, N.].) containing 12.5 mg of sodium fluoride and 10.0 mg of potassium oxalate. These samples were immediately centrifuged at 4° C and the serum was stored at - 70° C until analysis. An additional 0.5 ml was withdrawn in heparinized syringes for arterial pH, P0 2 , and Pc0 2 measurements. Plasma catecholamine levels were measured by a radioenzymatic assay as previously described. 19 The assay is sensitive to 1 to 2 pg of norepinephrine or epinephrine. The intraassay and interassay variabilities are
Torrance, California OBJECTIVE: Although maternal cocaine administration results in fetal cardiovascular and behavioral alterations, these responses have been attributed to hypoxia resulting from reduced uteroplacental blood flow. We studied the fetal catecholamine, cardiovascular, and neurobehavioral responses to direct fetal cocaine administration. STUDY DESIGN: Cardiovascular, electrocortical, and electroocular responses and plasma catecholamines were monitored in chronically catheterized fetal sheep (n = 7), 127 ± 2 days' gestation, during a control period and after intravenous fetal injections of cocaine 0.5 and 1.0 mg/kg. RESULTS: Intravenous cocaine caused prompt increases in fetal plasma norepinephrine (372 ± 73 to 531 ± 112 and 842 ± 233 pg/ml), epinephrine (27 ± 7 to 46 ± 13 and 49 ± 11 pg/ml), and systolic blood pressure (46 ± 2 to 53 ± 2 and 55 ± 2 mm Hg). Low-voltage electrocortical activity decreased from 61.7% ± 3.0% to 38.4% ± 3.9% in the first hour after the cocaine 0.5 mg/kg dose but recovered to baseline values during the second hour. After the cocaine 1.0 mg/kg dose, low-voltage electrocortical activity decreased to 40.7% ± 2.0% and did not recover thereafter. Fetal blood gas values did not change. CONCLUSION: Direct fetal cocaine administration increases fetal plasma catecholamine levels and fetal blood pressure and suppresses low-voltage electrocortical activity. Chronic cocaine exposure may hamper central nervous system maturation and alter postnatal development. (AM J QasTET GVNECOL 1992; 167: 1616-23.)
Key words: Cocaine, catecholamine, fetal neurobehavioral state Mounting evidence suggests that cocaine use during pregnancy may have consequences beyond such perinatal events as abruptio placentae, preterm labor, fetal distress, and intrauterine growth retardation. Indeed, a number of observations indicate that neurobehavioral and central cardiorespiratory regulatory development may be impaired in children exposed to cocaine in utero. Infants exposed to cocaine displayed increased tremulousness and startle responses and depressed consolability and interactive behavior. I In addition, an increased incidence of sudden infant death syndrome 2 and abnormal ventilatory patterns' has been reported among children whose mothers used cocaine during pregnancy. Animal studies also demonstrate neurobehavioral alterations. Rat pups exposed prenatally to cocaine were delayed in the development of the righting reflex: cliff From the Departments of Obstetrics and Gynecology and Pediatrics, Perinatal Research Laboratories, Harbor-University of California, Los Angeles Medical Center. Supported in part by grant R-413 from the United Cerebral Palsy Association. Presented in part at the Thirty-ninth Annual Meeting of the Society for Gynecologic Investigation, San Antonio, Texas, March 18-21, 1992. Reprint requests: Michael Ross, MD, Harbor-UCLA Medical Center, Research Building #1, 1124 W. Carson St., Torrance, CA 90502. 6/6/41933
avoidance, acoustic startle,5 and odor-milk association. 6 Behavioral alterations extending to adulthood also were noted in rats exposed to cocaine in utero, including impairment in spontaneous alterations, open field activity, water-maze performance, tail flick, and foot shock sensitivities. 7 Cocaine's effect on postnatal behavioral development may well be mediated through its action on catecholamine metabolism and sleep state regulation in utero. Cocaine blocks presynaptic catecholamine reuptake, leading to increased intrasynaptic norepinephrine concentration in central nervous system and peripheral sympathetic neurons. s An important neurotransmitter for sleep state regulation,9 norepinephrine is decreased in active sleep,lo the predominant behavioral state in fetal life. II. 12 Because active sleep state is accompanied by peak cerebral metabolism and blood flow and thus theorized to be vital for central nervous system maturation,I3 cocaine-induced suppression of fetal active sleep state may alter central nervous system maturation and postnatal behavioral development through chronically elevated central nervous system norepinephrine levels. Burchfield et al. 14 demonstrated decreased active sleep in fetal lambs given continuous intravenous cocaine infusions. However, neither the duration of the sleep state alteration nor the plasma catecholamine level was reported.
Volume 167 Number 6
Maternal cocaine administration results in significant ovine fetal cardiovascular effects in sheep. IS However, these effects may be secondary to cocaine-induced decreases in uteroplacental blood flow and resultant fetal hypoxemia. To avoid the vasoconstrictive effects of cocaine on uterine blood flow and resultant fetal hypoxia, we administered cocaine by direct fetal intravenous injections and sought to investigate fetal catecholamine, cardiovascular, and neurobehavioral responses. The results suggest an important role for norepinephrine in regulating cardiovascular and neurobehavioral states. Methods Surgical preparations. Seven time-bred ewes with singleton fetuses at 127 ± 2 days' gestation were studied. Animals were kept in individual metabolic cages and acclimated to an environment of alternating 12 hour light and dark cycles. Food and water were available ad libitum, except for withholding food 24 hours before surgery. The protocol was approved by the Harbor-UCLA Animal Use Committee and was in accord with American Association for Accreditation of Laboratory Animal Care and National Institutes of Health guidelines. The ewes were pre sedated with ketamine before endotracheal intubation and maintained during surgery on 1% to 2% isoflurane balanced with oxygen. Through a midline abdominal incision the uterus was exposed and the fetal head identified and exteriorized. Fetal electrocortical electrodes were inserted into the parietal dura, 16 and electroocular electrodes were sewn onto the periorbital tissue through incisions made above and below the orbit. Fetal and maternal polyethylene catheters were placed in the femoral artery and vein and advanced to the abdominal aorta and inferior vena cava, respectively. An intrauterine catheter (Corometrics Medical System, Wallingford, Conn.) was inserted for amniotic fluid pressure measurement. Antibiotics were administered in the immediate postoperative period and twice daily for 2 days. Gentamicin (S mg) and oxacillin (33 mg) were administered intravenously to the fetus, and gentamicin (72 mg), oxacillin (1 gm), and chloramphenicol (1 gm) were given to the ewe. Methods for the maintenance of catheters and protocols used for the sampling of blood have been detailed previously.17 All animals were allowed to recover for a minimum of 5 days before study. Protocol. On the day of study the unanesthesized animals were observed for a 2-hour control period (0 to 120 minutes), during which time fetal electrocortical and electroocular activity were recorded continuously and blood pressure and pulse were measured every 5 minutes. Duplicate fetal blood samples for measurement of hematocrit, arterial pH, P0 2 , Pco 2 , norepinephrine, epinephrine, and cocaine concentrations were
Fetal responses to cocaine
1617
withdrawn at 60 and 120 minutes. At the end of the control period an injection of cocaine 0.5 mg/kg in 2 ml of 0.9% saline solution was administered intravenously over 30 seconds. At time 240 minutes, a second injection of 1.0 mg/kg was similarly administered. The estimated fetal weights were derived on the basis of gestational age by the formula: Estimated fetal weight (kilograms) = 0.0961 x Gestational age (days) - 9.222S.18 The ewe and fetus were continuously monitored and fetal blood samples were drawn at 5, 15, 30, 60, and 120 minutes after each i~ection. Two maternal blood samples for measurement of hematocrit, arterial pH, P0 2 , Pc0 2 , catecholamine, and cocaine concentrations were taken during the control period and 15 and 120 minutes after each injection. All fetal blood samples were replaced with equivalent volumes of heparinized maternal blood drawn before the study. Maternal blood samples were replaced with equivalent volumes of saline solution. Fetal electrocortical activity. Fetal electrocortical activity was defined as either high or low voltage on the basis of visual inspection of the polygraph tracings. Results are expressed as percentage time spent during two 60-minute epochs in each study period (control, after first injection, and after second injection). Analytic techniques. Blood samples were transferred immediately to chilled test tubes. One milliliter of whole blood for catecholamine determination was added to tubes containing ethylene glycol-bis (l3-aminoethyl ether) N,N,N',N'-tetraacetic acid 4 mmol!L and reduced glutathione 3 mmol!L. Two milliliters of blood for cocaine and metabolite determination injected into 3 ml capacity Vacutainer tubes (No. 6471; Becton Dickinson, Rutherford, N.].) containing 12.5 mg of sodium fluoride and 10.0 mg of potassium oxalate. These samples were immediately centrifuged at 4° C and the serum was stored at - 70° C until analysis. An additional 0.5 ml was withdrawn in heparinized syringes for arterial pH, P0 2 , and Pc0 2 measurements. Plasma catecholamine levels were measured by a radioenzymatic assay as previously described. 19 The assay is sensitive to 1 to 2 pg of norepinephrine or epinephrine. The intraassay and interassay variabilities are
