1916
8. 9. 10. 11. 12. 13.
Letters
findings in infants with meconium aspiration syndrome. JAMA 1979;242:60-3. Bertolussi R, Seeliger HPR. Listeriosis. In: Remington JS, Klein J 0, eds. Infectious diseases of the fetus and newborn infant. 3rd ed. Philadelphia: WB Saunders 1990;812:33. Jovanovic R, Nguyen HT. Experimental meconium aspiration in guinea pigs. Obstet Gynecol 1989;73:652-6. Linder N, ArandaJV, Tsur M, et al. Need for endotracheal intubation and suction in meconium-stained neonates. J Pediatr 1988;112:613-5. Burke-Strickalnd M, Edwards NB. Meconium aspiration in the newborn. Minn Med 1973;56:1031-8. Ting P, Brady JP. Tracheal suction in meconium aspiration. AM J OBSTET GYNECOL 1975;122:767-71. Committee on neonatal ventilation/meconium/chest compressions. In: Proceedings of the 1992 National Conference on Cardiopulmonary Resuscitation and Emergency Cardiac Care sponsored by the American Heart Association, Dallas, Texas, Feb 22-25, 1992.
Reply To the Editors: We reviewed meconium aspiration syndrome because for two decades obstetricians and pediatricians have tried to explain clinical observations with a theory about meconium aspiration that does not fit.' This theory of meconium aspiration syndrome held that the disease was caused by meconium inhaled during the infant's first breath. The influential works by Carson et al. 2 and Gregory et al.' built on this assumption to advocate tracheal suctioning to prevent meconium aspiration syndrome. However, meconium aspiration syndrome continued to occur de~pite tracheal suctioning. The 15-year survey of meconium aspiration syndrome by Wiswell et al. 4 illustrates this point most clearly. The incidence of meconium aspiration syndrome did not drop below the 1973 to 1974 levels (after which the practice of tracheal suctioning began) until 1983. The mortality rate from meconium aspiration syndrome declined from 1975 to 1977, but then rose to pre-1975 levels in 1979,1981,1982,1983, and 1985. We did not state that Wiswell et al. compared 1973 and 1985. We believe that the pathologic aspect of meconium aspiration syndrome is caused by pulmonary vascular spasm and vascular hyperreactivity caused by fetal hypoxia and asphyxia. Meconium aspiration syndrome is a spectrum of pulmonary vascular disease, and increased muscularization can be found in the most severe cases. Perlman et al. 5 did find excessive pulmonary vascular muscularity in infants who died with meconium aspiration syndrome and in controls. These controls were stillborn fetuses with abruptio placentae and other stressed fetuses and newborns. In reports that have also found increased pulmonary muscularity, the controls with normal vasculature were nonasphyxiated.' Meconium aspiration syndrome is associated with thin meconium approximately 5% of the time. Meconium aspiration syndrome with thin meconium is a mild, self-limited problem very different from the meconium aspiration syndrome associated with thick meconium. Studies such as that by Yeh et al.,6 which report a 44% association, describe a " ... relatively be-
December 1992
Am J Obstet Gynecol
nign course similar to that of wet lung syndrome. .. produced by aspiration of thin meconium."6 Wiswell and Henley6 found 1 of 36 (3%) patients with meconium aspiration syndrome to be associated with thin meconium in their more recent report. Wiswell states that we cited no references in regard to meconium aspiration syndrome and infection. In fact, there were eight references. Additionally, Benny et al. B and Burke-Strickland and Edwards 9 found worse outcomes among infants with meconium aspiration syndrome and infection. Yeh et al. 7 found 6 of 11 deaths from meconium aspiration syndrome to be associated with pneumonia. The association between meconium aspiration syndrome and infection occurs because the pathologic make-up of both diseases may include pulmonary hypertension. Wiswell describes the work of Linder et al. 10 as flawed. That study is the only prospective trial looking at tracheal intubation 10; although it may have had methodological problems, among 264 infants without tracheal visualization there was no meconium aspiration syndrome. Among 308 infants with tracheal intubation there were four cases of MAS. Vern L. Katz, MD, and Watson A. Bowes, Jr., MD Department of Obstetrics and Gynecology, University of North Carolina, McNider Building, CB 7570, Chapel Hill, NC 27599 REFERENCES
1. Katz VK, Bowes WA Jr. Meconium aspiration syndrome: reflections on a murky subject. AM J OBSTET GYNECOL 1992; 166: 171-83. 2. Carson BS, Losey RW, Bowes WAJr, Simmons MA. Combined obstetric and pediatric approach to prevent meconium aspiration syndrome. AM J OBSTET GYNECOL 1976; 126:712-5. 3. Gregory GA, Gooding CA, Phibbs RH, Tooley WHo Meconium aspiration in infants-a prospective study. J Pediatr 1974;85:848-52. 4. Wiswell TE, Tuggle JM, Turner BS. Meconium aspiration syndrome: have we made a difference? Pediatrics 1990;85: 715-21. 5. Perlman EJ, Moore GW, Hutchins GM. The pulmonary vasculature in meconium aspiration. Hum Pathol 1989;20: 701-6. 6. Wiswell TE, Henley MA. Intratracheal suctioning, systemic infection, and the meconium aspiration syndrome. Pediatrics 1992;89:203-6. 7. Yeh TS, Harris V, Srinivasan G, Lilien L, Pyati S, Pildes RS. Roentgenographic findings in infants with meconium aspiration syndrome. JAMA 1979;242:60-3. 8. Benny PS, Malani S, Hoby MA, Hutton JD. Meconium aspiration-role of obstetric factors and suction. Aust N Z J Obstet Gynaecol 1987;27:36-9. 9. Burke-Strickland, Edwards NB. Meconium aspiration in the newborn. Minn Med 1973:1031-5. 10. Linder N, et al. Need for endotracheal intubation and suction on meconium-stained neonates. J Pediatr 1988; 112:613-5. Changes in human fetal cerebral oxygenation and blood volume during delivery To the Editors: We recently reported the first use of near-infrared spectroscopy for monitoring fetal brain oxygenation during labor (Peebles DM, Edwards AD,
Letters
Volume 167 Number 6
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8. 9. 10. 11. 12. 13.
Letters
findings in infants with meconium aspiration syndrome. JAMA 1979;242:60-3. Bertolussi R, Seeliger HPR. Listeriosis. In: Remington JS, Klein J 0, eds. Infectious diseases of the fetus and newborn infant. 3rd ed. Philadelphia: WB Saunders 1990;812:33. Jovanovic R, Nguyen HT. Experimental meconium aspiration in guinea pigs. Obstet Gynecol 1989;73:652-6. Linder N, ArandaJV, Tsur M, et al. Need for endotracheal intubation and suction in meconium-stained neonates. J Pediatr 1988;112:613-5. Burke-Strickalnd M, Edwards NB. Meconium aspiration in the newborn. Minn Med 1973;56:1031-8. Ting P, Brady JP. Tracheal suction in meconium aspiration. AM J OBSTET GYNECOL 1975;122:767-71. Committee on neonatal ventilation/meconium/chest compressions. In: Proceedings of the 1992 National Conference on Cardiopulmonary Resuscitation and Emergency Cardiac Care sponsored by the American Heart Association, Dallas, Texas, Feb 22-25, 1992.
Reply To the Editors: We reviewed meconium aspiration syndrome because for two decades obstetricians and pediatricians have tried to explain clinical observations with a theory about meconium aspiration that does not fit.' This theory of meconium aspiration syndrome held that the disease was caused by meconium inhaled during the infant's first breath. The influential works by Carson et al. 2 and Gregory et al.' built on this assumption to advocate tracheal suctioning to prevent meconium aspiration syndrome. However, meconium aspiration syndrome continued to occur de~pite tracheal suctioning. The 15-year survey of meconium aspiration syndrome by Wiswell et al. 4 illustrates this point most clearly. The incidence of meconium aspiration syndrome did not drop below the 1973 to 1974 levels (after which the practice of tracheal suctioning began) until 1983. The mortality rate from meconium aspiration syndrome declined from 1975 to 1977, but then rose to pre-1975 levels in 1979,1981,1982,1983, and 1985. We did not state that Wiswell et al. compared 1973 and 1985. We believe that the pathologic aspect of meconium aspiration syndrome is caused by pulmonary vascular spasm and vascular hyperreactivity caused by fetal hypoxia and asphyxia. Meconium aspiration syndrome is a spectrum of pulmonary vascular disease, and increased muscularization can be found in the most severe cases. Perlman et al. 5 did find excessive pulmonary vascular muscularity in infants who died with meconium aspiration syndrome and in controls. These controls were stillborn fetuses with abruptio placentae and other stressed fetuses and newborns. In reports that have also found increased pulmonary muscularity, the controls with normal vasculature were nonasphyxiated.' Meconium aspiration syndrome is associated with thin meconium approximately 5% of the time. Meconium aspiration syndrome with thin meconium is a mild, self-limited problem very different from the meconium aspiration syndrome associated with thick meconium. Studies such as that by Yeh et al.,6 which report a 44% association, describe a " ... relatively be-
December 1992
Am J Obstet Gynecol
nign course similar to that of wet lung syndrome. .. produced by aspiration of thin meconium."6 Wiswell and Henley6 found 1 of 36 (3%) patients with meconium aspiration syndrome to be associated with thin meconium in their more recent report. Wiswell states that we cited no references in regard to meconium aspiration syndrome and infection. In fact, there were eight references. Additionally, Benny et al. B and Burke-Strickland and Edwards 9 found worse outcomes among infants with meconium aspiration syndrome and infection. Yeh et al. 7 found 6 of 11 deaths from meconium aspiration syndrome to be associated with pneumonia. The association between meconium aspiration syndrome and infection occurs because the pathologic make-up of both diseases may include pulmonary hypertension. Wiswell describes the work of Linder et al. 10 as flawed. That study is the only prospective trial looking at tracheal intubation 10; although it may have had methodological problems, among 264 infants without tracheal visualization there was no meconium aspiration syndrome. Among 308 infants with tracheal intubation there were four cases of MAS. Vern L. Katz, MD, and Watson A. Bowes, Jr., MD Department of Obstetrics and Gynecology, University of North Carolina, McNider Building, CB 7570, Chapel Hill, NC 27599 REFERENCES
1. Katz VK, Bowes WA Jr. Meconium aspiration syndrome: reflections on a murky subject. AM J OBSTET GYNECOL 1992; 166: 171-83. 2. Carson BS, Losey RW, Bowes WAJr, Simmons MA. Combined obstetric and pediatric approach to prevent meconium aspiration syndrome. AM J OBSTET GYNECOL 1976; 126:712-5. 3. Gregory GA, Gooding CA, Phibbs RH, Tooley WHo Meconium aspiration in infants-a prospective study. J Pediatr 1974;85:848-52. 4. Wiswell TE, Tuggle JM, Turner BS. Meconium aspiration syndrome: have we made a difference? Pediatrics 1990;85: 715-21. 5. Perlman EJ, Moore GW, Hutchins GM. The pulmonary vasculature in meconium aspiration. Hum Pathol 1989;20: 701-6. 6. Wiswell TE, Henley MA. Intratracheal suctioning, systemic infection, and the meconium aspiration syndrome. Pediatrics 1992;89:203-6. 7. Yeh TS, Harris V, Srinivasan G, Lilien L, Pyati S, Pildes RS. Roentgenographic findings in infants with meconium aspiration syndrome. JAMA 1979;242:60-3. 8. Benny PS, Malani S, Hoby MA, Hutton JD. Meconium aspiration-role of obstetric factors and suction. Aust N Z J Obstet Gynaecol 1987;27:36-9. 9. Burke-Strickland, Edwards NB. Meconium aspiration in the newborn. Minn Med 1973:1031-5. 10. Linder N, et al. Need for endotracheal intubation and suction on meconium-stained neonates. J Pediatr 1988; 112:613-5. Changes in human fetal cerebral oxygenation and blood volume during delivery To the Editors: We recently reported the first use of near-infrared spectroscopy for monitoring fetal brain oxygenation during labor (Peebles DM, Edwards AD,
Letters
Volume 167 Number 6
--
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!
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0
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'-"
1917
Hb
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