Postmortem Vitreous Humor Chemistry in Sudden Infant Death Syndrome and in Other Causes of Death in Childhood THOMAS A. BLUMENFELD, M.D., CARY H. MANTELL, B.A., ROBERT L. CATHERMAN, M.D., AND WILLIAM A. BLANC, M.D.
WHEN A THOROUGH POSTMORTEM examination fails to reveal an adequate cause of death of an infant or young child who has died suddenly and unexpectedly, the diagnosis is sudden infant death syndrome (SIDS). 2 Postmortem chemical values of body fluids are difficult to interpret because chemical changes in tissues and fluids are influenced by storage temperature and time between death and autopsy (postmortem interReceived September 19, 1977; received revised manuscript and accepted for publication December 7, 1977. Address reprint requests to Dr. Blumenfeld: Babies Hospital, Columbia-Presbyterian Medical Center, 622 West 168th Street, New York, New York 10032.
Departments of Pediatrics and Pathology, College of Physicians and Surgeons, Columbia University, and Babies Hospital, The Children's Medical and Surgical Center, New York, New York, and Office of the Medical Examiner, Philadelphia, Pennsylvania
vol).14 However, postmortem vitreous humor chemical concentrations reflect antemortem blood chemical values, and vitreous humor concentrations of Na + , CI", and urea nitrogen remain stable for as long as 30 hours after death. Those of Ca +2 , Mg +2 , and creatinine remain constant or change slightly after d e a t h . 4 " 1 3 We compared postmortem vitreous humor concentrations of Na + , K + , Cl~, Ca +2 , Mg +2 , urea nitrogen, creatinine, and total protein of children who had died of known causes and those who had died of SIDS. The purposes of this study were: (1) to determine whether there were differences in the concentrations of the eight constituents of vitreous humor studied in children who had died of known causes and those who had died of SIDS that would identify SIDS or give information about its etiology; (2) to determine whether the concentrations of the chemical constituents studied changed with the postmortem interval, which, if so, could aid in determining the postmortem interval; (3) to compare postmortem vitreous humor concentrations with stated normal antemortem serum concentrations in children who had died of known causes. Materials and Methods Postmortem vitreous humor was aspirated from both eyes of 127 children during postmortem examination, at Babies Hospital and the Office of the Medical Examiner, Philadelphia. The aspiration was performed with an 18-gauge needle attached to a 10-ml disposable plastic syringe, by puncturing the sclera at the lateral canthus. Each sample was placed in a separately labeled plastic container, sealed, and frozen at - 2 0 C until chemically analyzed. When sufficient volume was obtained from each eye, analysis of each specimen was performed and the mean value of each
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Blumcnfeld, Thomas A., Mantell, Cary H., Catherman, Robert L., and Blanc, William A.: Postmortem vitreous humor chemistry in sudden infant death syndrome and in other causes of death in childhood. Am J Clin Pathol 71: 219-223, 1979. Postmortem vitreous humor concentrations reflect antemortem serum chemical values. The authors measured the postmortem vitreous humor concentrations of Na+, K+, Cl~, Ca+2, Mg+2, urea nitrogen, creatinine, and total protein of 127 children who died from sudden infant death syndrome (SIDS) and other causes. Forty-seven children, 1 hour to 13 years old, had died of medical or surgical causes; 21 children, 7 weeks to 11 years old, had died following acute trauma; 59 children, 8 days to 1 year old, had died of SIDS. There was no significant difference between mean postmortem vitreous humor concentrations of those who died of medical and surgical causes and those who died after acute trauma (non-SIDS). In both groups, the mean postmortem vitreous humor concentrations of Mg+2 and Ca+2 were significantly higher in premature infants. There was direct correlation of postmortem vitreous humor concentration and postmortem interval for K+, but the variation, ±26 hours, was too large to be of practical importance in estimating time of death in individual cases. The three patient groups were compared and the mean postmortem vitreous humor concentrations of all eight constituents in the SIDS and non-SIDS groups were in the same ranges. In SIDS, the mean postmortem vitreous humor concentrations of Mg+2, Cl~, and urea nitrogen were significantly different from values of the non-SIDS cases, but not enough to indicate SIDS or to be informative about the etiology of SIDS. Measurement of the concentrations of postmortem vitreous humor constituents may not aid in the diagnosis of SIDS, but may aid in discovering unsuspected antemortem serum chemical abnormalities. (Key words: Postmortem vitreous humor chemistry; Sudden infant death syndrome.)
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Table 1. Methods, Instruments, and Sample Volumes
Analyte
Method
Sample Volume, UI
Urea nitrogen Calcium Chloride Magnesium Potassium Sodium Total protein Creatinine
Enzymatic (urease)* Atomic absorptiont Coulmetric amperometrict Atomic absorptiont Flame photometry§ Flame photometry! Trichloroacetic acid-Ponceau S dye Jaffe*
10 25 10 25 12 12 50 25
* Centrifichem Analyzer; Union Carbide Corp., Tarrytown, New York 10591. t Atomic Absorption Spectrophotometer Model 303; Perkin Elmer Corp., Main Avenue, Norwalk. Connecticut 06856. t Chloride Titrator; American Instrument Co., Silver Spring, Maryland 20910. § KLINA Flame System; Beckman Instruments, Inc., 2500 Harbor Blvd., Fullerton, California 92634.
Results Statistical comparison of the mean postmortem vitreous humor concentrations of children who had suffered acute traumatic deaths and hospital deaths showed no significant difference. Hence, these pop-
ulations were combined and are referred to as the nonSIDS population. Postmortem
Interval
The statistical correlation between vitreous humor K + concentration and postmortem interval was significant (r = 0.630), but the 95% confidence limit was ±26 hours at the mean K + concentration. The K + concentration was 7.9 to 25.1 mEq/1, and the postmortem interval was 1-77 hours. There was no statistically significant correlation between vitreous humor concentrations of Na+ (r = 0.370), Cl~ (r = 0.080), Ca+2 (r = 0.590), Mg+2 (r = 0.580), or urea nitrogen (r = 0.030) and postmortem interval. Comparison of Acute Traumatic Death Cases with Hospital Death Cases There was no significant difference between the mean postmortem vitreous humor concentrations of K+ (t = 0.150, / > > 0 . 0 5 ) , Na+ (t = 0.460, P > 0 . 0 5 ) , CI- (t = 1.930, P > 0.05), Ca+2 (t = 1.080, P > 0.05), Mg+2 (t = 0.840, P > 0.05) and urea nitrogen (t = 0.720, P > 0.05) in the acute traumatic death population and those in the hospital death population. There were significant differences between the mean postmortem vitreous humor concentrations of Ca +2 (t = 4.43, P < 0.05) and Mg +2 (t = 13.66, P < 0.05) in premature and full-term infants (Fig. 1); for this reason, the acute traumatic death and hospital death populations were matched for age before comparison of the mean postmortem vitreous concentrations of Ca +2 and Mg +2 . Comparison of SIDS with Non-SIDS
Cases (Table 2)
There was no significant difference between the mean postmortem vitreous humor concentration of K+ (t = 0.890, />>0.05), Na + (t = 0.160, P > 0 . 0 5 ) , Ca +2 (t = 0.420, P > 0 . 0 5 ) , creatinine (t = 1.240, P > 0.05), and total protein (t = 1.390, P > 0.05) of the SIDS and that of the Non-SIDS population. There was a significant difference between the mean postmortem vitreous concentration of CI" (t = 2.620, P < 0.05), Mg +2 (t = 6.630, P < 0.05), and urea nitrogen (t = 3.480, P < 0.05) of the SIDS population and that of the NonSIDS population. The two groups were matched for age before comparison of the mean postmortem vitreous humor concentrations of Ca +2 and Mg +2 due to the age dependency of these constituents. Comparison of Postmortem Vitreous Humor Concentrations with Antemortem Serum Concentrations (Table 3) The postmortem vitreous humor concentrations (range of mean ± 2 SD) for urea nitrogen, creatinine,
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chemical constituent was calculated. When the volume obtained from each eye was insufficient, samples from both eyes were pooled before analysis. 13 In some cases, the pooled volume was insufficient for analysis of all chemical constituents. The chemical methods, analytic instruments and sample volumes used in this study are listed in Table 1. Based on the cause of death, the results were placed into one of three groups: /. Hospital Deaths. These 47 children (32 male, 15 female) were 1 hour to 13 years of age, and 24 were premature (
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WHEN A THOROUGH POSTMORTEM examination fails to reveal an adequate cause of death of an infant or young child who has died suddenly and unexpectedly, the diagnosis is sudden infant death syndrome (SIDS). 2 Postmortem chemical values of body fluids are difficult to interpret because chemical changes in tissues and fluids are influenced by storage temperature and time between death and autopsy (postmortem interReceived September 19, 1977; received revised manuscript and accepted for publication December 7, 1977. Address reprint requests to Dr. Blumenfeld: Babies Hospital, Columbia-Presbyterian Medical Center, 622 West 168th Street, New York, New York 10032.
Departments of Pediatrics and Pathology, College of Physicians and Surgeons, Columbia University, and Babies Hospital, The Children's Medical and Surgical Center, New York, New York, and Office of the Medical Examiner, Philadelphia, Pennsylvania
vol).14 However, postmortem vitreous humor chemical concentrations reflect antemortem blood chemical values, and vitreous humor concentrations of Na + , CI", and urea nitrogen remain stable for as long as 30 hours after death. Those of Ca +2 , Mg +2 , and creatinine remain constant or change slightly after d e a t h . 4 " 1 3 We compared postmortem vitreous humor concentrations of Na + , K + , Cl~, Ca +2 , Mg +2 , urea nitrogen, creatinine, and total protein of children who had died of known causes and those who had died of SIDS. The purposes of this study were: (1) to determine whether there were differences in the concentrations of the eight constituents of vitreous humor studied in children who had died of known causes and those who had died of SIDS that would identify SIDS or give information about its etiology; (2) to determine whether the concentrations of the chemical constituents studied changed with the postmortem interval, which, if so, could aid in determining the postmortem interval; (3) to compare postmortem vitreous humor concentrations with stated normal antemortem serum concentrations in children who had died of known causes. Materials and Methods Postmortem vitreous humor was aspirated from both eyes of 127 children during postmortem examination, at Babies Hospital and the Office of the Medical Examiner, Philadelphia. The aspiration was performed with an 18-gauge needle attached to a 10-ml disposable plastic syringe, by puncturing the sclera at the lateral canthus. Each sample was placed in a separately labeled plastic container, sealed, and frozen at - 2 0 C until chemically analyzed. When sufficient volume was obtained from each eye, analysis of each specimen was performed and the mean value of each
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Blumcnfeld, Thomas A., Mantell, Cary H., Catherman, Robert L., and Blanc, William A.: Postmortem vitreous humor chemistry in sudden infant death syndrome and in other causes of death in childhood. Am J Clin Pathol 71: 219-223, 1979. Postmortem vitreous humor concentrations reflect antemortem serum chemical values. The authors measured the postmortem vitreous humor concentrations of Na+, K+, Cl~, Ca+2, Mg+2, urea nitrogen, creatinine, and total protein of 127 children who died from sudden infant death syndrome (SIDS) and other causes. Forty-seven children, 1 hour to 13 years old, had died of medical or surgical causes; 21 children, 7 weeks to 11 years old, had died following acute trauma; 59 children, 8 days to 1 year old, had died of SIDS. There was no significant difference between mean postmortem vitreous humor concentrations of those who died of medical and surgical causes and those who died after acute trauma (non-SIDS). In both groups, the mean postmortem vitreous humor concentrations of Mg+2 and Ca+2 were significantly higher in premature infants. There was direct correlation of postmortem vitreous humor concentration and postmortem interval for K+, but the variation, ±26 hours, was too large to be of practical importance in estimating time of death in individual cases. The three patient groups were compared and the mean postmortem vitreous humor concentrations of all eight constituents in the SIDS and non-SIDS groups were in the same ranges. In SIDS, the mean postmortem vitreous humor concentrations of Mg+2, Cl~, and urea nitrogen were significantly different from values of the non-SIDS cases, but not enough to indicate SIDS or to be informative about the etiology of SIDS. Measurement of the concentrations of postmortem vitreous humor constituents may not aid in the diagnosis of SIDS, but may aid in discovering unsuspected antemortem serum chemical abnormalities. (Key words: Postmortem vitreous humor chemistry; Sudden infant death syndrome.)
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Table 1. Methods, Instruments, and Sample Volumes
Analyte
Method
Sample Volume, UI
Urea nitrogen Calcium Chloride Magnesium Potassium Sodium Total protein Creatinine
Enzymatic (urease)* Atomic absorptiont Coulmetric amperometrict Atomic absorptiont Flame photometry§ Flame photometry! Trichloroacetic acid-Ponceau S dye Jaffe*
10 25 10 25 12 12 50 25
* Centrifichem Analyzer; Union Carbide Corp., Tarrytown, New York 10591. t Atomic Absorption Spectrophotometer Model 303; Perkin Elmer Corp., Main Avenue, Norwalk. Connecticut 06856. t Chloride Titrator; American Instrument Co., Silver Spring, Maryland 20910. § KLINA Flame System; Beckman Instruments, Inc., 2500 Harbor Blvd., Fullerton, California 92634.
Results Statistical comparison of the mean postmortem vitreous humor concentrations of children who had suffered acute traumatic deaths and hospital deaths showed no significant difference. Hence, these pop-
ulations were combined and are referred to as the nonSIDS population. Postmortem
Interval
The statistical correlation between vitreous humor K + concentration and postmortem interval was significant (r = 0.630), but the 95% confidence limit was ±26 hours at the mean K + concentration. The K + concentration was 7.9 to 25.1 mEq/1, and the postmortem interval was 1-77 hours. There was no statistically significant correlation between vitreous humor concentrations of Na+ (r = 0.370), Cl~ (r = 0.080), Ca+2 (r = 0.590), Mg+2 (r = 0.580), or urea nitrogen (r = 0.030) and postmortem interval. Comparison of Acute Traumatic Death Cases with Hospital Death Cases There was no significant difference between the mean postmortem vitreous humor concentrations of K+ (t = 0.150, / > > 0 . 0 5 ) , Na+ (t = 0.460, P > 0 . 0 5 ) , CI- (t = 1.930, P > 0.05), Ca+2 (t = 1.080, P > 0.05), Mg+2 (t = 0.840, P > 0.05) and urea nitrogen (t = 0.720, P > 0.05) in the acute traumatic death population and those in the hospital death population. There were significant differences between the mean postmortem vitreous humor concentrations of Ca +2 (t = 4.43, P < 0.05) and Mg +2 (t = 13.66, P < 0.05) in premature and full-term infants (Fig. 1); for this reason, the acute traumatic death and hospital death populations were matched for age before comparison of the mean postmortem vitreous concentrations of Ca +2 and Mg +2 . Comparison of SIDS with Non-SIDS
Cases (Table 2)
There was no significant difference between the mean postmortem vitreous humor concentration of K+ (t = 0.890, />>0.05), Na + (t = 0.160, P > 0 . 0 5 ) , Ca +2 (t = 0.420, P > 0 . 0 5 ) , creatinine (t = 1.240, P > 0.05), and total protein (t = 1.390, P > 0.05) of the SIDS and that of the Non-SIDS population. There was a significant difference between the mean postmortem vitreous concentration of CI" (t = 2.620, P < 0.05), Mg +2 (t = 6.630, P < 0.05), and urea nitrogen (t = 3.480, P < 0.05) of the SIDS population and that of the NonSIDS population. The two groups were matched for age before comparison of the mean postmortem vitreous humor concentrations of Ca +2 and Mg +2 due to the age dependency of these constituents. Comparison of Postmortem Vitreous Humor Concentrations with Antemortem Serum Concentrations (Table 3) The postmortem vitreous humor concentrations (range of mean ± 2 SD) for urea nitrogen, creatinine,
Downloaded from http://ajcp.oxfordjournals.org/ by guest on June 5, 2016
chemical constituent was calculated. When the volume obtained from each eye was insufficient, samples from both eyes were pooled before analysis. 13 In some cases, the pooled volume was insufficient for analysis of all chemical constituents. The chemical methods, analytic instruments and sample volumes used in this study are listed in Table 1. Based on the cause of death, the results were placed into one of three groups: /. Hospital Deaths. These 47 children (32 male, 15 female) were 1 hour to 13 years of age, and 24 were premature (
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