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Meconium aspiration syndrome
Meconium aspiration syndrome Neonatal
and follow-up
RICHARD
MARSHALL,
EILEEN
TYRALA,
study
M.D. M.D.
WILLIAM
McALISTER,
MICHAEL
SHEEHAN,
M.D. M.D.
St. Louis, Missouri One year’s experience with MAS in a neonatal intensive-care unit is analyzad with follow-up information. Seventeen pa!ients or 3.7 per cent of all admissions had MAS. Four patients (23.5 per cent) died of acute respiratory failure. Two patients with MAS and persistence of the fetal circulation required cardiac catheterization to exclude cyanotic congenital heart disease. No survivors had persistent chronic lung disease. However, two of three patients with MAS and seizures had significant psychomotor retardation at follow-up examination. (AM. J. OBSTET. GYNECOL. 131: 672, 1978.)
of amniotic fluid occurs in between 8.9 to 9.6 per cent of deliveries and often is associated with meconium staining of infants.‘, 2 In a prospective study, as many as 20 per cent of meconium-stained infants developed either pulmonary disease requiring increased ambient oxygen and/or a pneumothorax or pneumomediastinum during the first 3 days of life. We define meconium aspiration syndrome (MAS) by the following criteria: (1) the presence of meconiumstained infants, (2) abnormal chest roentgenograms consistent with aspiration pneumonitis, and (3) clinical respiratory distress in the first 24 hours of life. Previous investigations have described certain aspects of the clinical course of MAS5 but there is scant information about the prognosis of infants with MAS.3, I3 The clinical course of the acute illness and a follow-up study of all patients with MAS admitted to the neonatal intensive-care unit (NICU) at St. Louis Children’s Hospital in 1974 form the basis of this report. MECONIUM
STAINING
From the Edward Mallinckrodt Department of Pediatrics and the Mallinckrodt Institute of Radiology, Wa.shingta University School of Medicine, and the Division of Neaatology, St. Loub Children’s Hospital. Received
for
Accepted
December
publication
Reprint requests: Richard Children’s Hospital, 500 Missouri 63 1 IO.
672
July
11, 1977.
6, 1977. Marshall, M.D., S. Kingshighway,
St. Louis St. LOGY,
Methods The hospital charts of all patients admitted to the NICU St. Louis Children’s Hospital were reviewed by one investigator (M. S.). Out of 441 NICU admissions, 17 patients were judged to have MAS by the criteria described above. Obstetric records were reviewed to determine (1) use of fetal monitoring, (2) time when meconium was observed prior to delivery, (3) Apgar scores, (4) mode of suctioning, and (5) mode of resuscitation The neonatal hospital course of each patient was reviewed. Follow-up exminations on all available survivors (11 of 13) at 1 I to 18 months of age consisted of a general physical examination, chest radiographs, developmental history, Denver developmental examination, and a specific history to determine intercurrent respiratory illnesses. Analysis of the obstetric records revealed that meconium was noted in the amniotic fluid more than 1 hour prior to delivery in six of 17 cases. Only one of these six deliveries in which meconium was recognized was monitored thereafter. Fifteen infants were vertex presentations and delivery was accomplished easily; two infants were delivered with difficulty-one because of a shoulder dystocia and one because of a transverse lie. Information about the type of suctioning received in the delivery room was available for 14 of 17 patients. Six patients received bulb syringe suctioning of the nasopharynx and posterior oral pharynx. Four pa000%9378/78/06131-0672$00,50/OO
1978 The C. V. Mosby Co
Volume Number
Meconium aspiration syndrome
151 6
Fig. 2. Chest roentgenograms. A, Initial: narv infiltrates a1.e shown. R, One nwnth
673
widespread pulmo-
Fig. 1. Chest roentgenograms. ‘4, Initial; there are intrinsic pulmonary infiltrates. B, One vear later; complete resolution has occurred.
is ndrmal.
tients received tracheal suctioning under direct larynoscopic visualization of the cords. One of the infants who died had direct tracheal suctioning. Three of the six infants who lived and required respiratory therapy had direct tracheal suctioning. Two patients were thought to be postterm by dates before delivery. However, pediatric physical examination suggested that seven infants were postmature. Three of the four deaths occurred in patients who were recognized as postmature after birth. Apgar scores at 1 and 5 minutes were higher in survivors and in more infants who did not require the respirator. Patients were divided into three categories: Group I, survivors who did not require respirator therapy (N = 7); Group II, survivors who required respirator therapy (N = 6); Group III. those who died (N = 4). Salient features of the clinical course are summarized in Table I. Patients in Group II who survived required the res-
pirator for a mean of 5.2 days. Those who died on the respirator did so within 24 hours. Group I1 patients were exposed to higher concentrations of inspired oxygen then were thostb in Group I. Calculations were made to estimate the percentage of cardiac output that was shunted right-to-left at the time initial blood gases were determined! Shunting was greatest in the patients who died. Patients in Group II had more shunting than patients in (iroup 1, who did not require the respirator. Two patients in Group II had clinical courses of particular interest which will be presented in detail. ‘They both had inadequate oxygenation on 100 per cent inspired oxygen, suggesting the possibility that they had cardiac disease superimposed upon MRS. .& an exarnpie, A. M. was born after a labor complic;~trd by maternal fever and shoulder dystocia. .Fhr I and .? minute Apgar scores were 1 and 5 despite tracheal suctioning done under direct visualization. ‘l‘his patient was plactd on the Bournes respirator immediately after
later.
the chest
film
674
Table
Marshall
et al.
I. Salient
July 1.5, I978 Am. J. Obstet. Gynerol.
features
of clinical
courses Apgar
Birth wt. (Gm.)
Group I, living, no respirator (N = 7) Group II, living, respirator (N -7) Group III, dead, respirator
scores
Resp.
rate
60, tachypaea 1 min.
(days)
Duration resp. therapy (days)
7.2
f 1.0
3.4 + 1.4
18.7
f 1.1
-
2.8 Y!I 0.7
4.3
+ 1
9.8 2 3.5
54.3
+ 9.7
5.2 + 2.3
1.8 -+ 0.3
2.5 t 0.8
-
80.
2 15
3,385
f 289
4.6
2,353
~~228
3,538
2 213
r 1.1
5 min.
Cardiac output, shunted R-L, initial blood gases (%,J
-
(N =4)
birth and required 100 per cent inspired oxygen with a positive end-expiratory pressure of 4 cm. H,O to maintain a Pa, of less than 45 mm. Hg. Cardiac catheterization on day 2 demonstrated systemic pressure in the right ventricle, patent foramen ovale, and a large patent ductus arteriosus. She gradually improved but required respirator care for 11 days. Another patient, M. C., was born postmaturely with gross meconium staining and had 1 and 5 minute Apgar scores of 4 and 4, respectively. Meconium was suctioned from the trachea in the delivery room under direct visualization. Shortly after birth, she was placed on a Bournes respirator with 100 per cent inspired oxygen and 3 cm. HZ0 positive end-expiratory pressure. Inadequate oxygenation resulted in cardiac catheterization, whereupon she was found to have elevated pulmonary artery and right ventricular pressure with a large right-to-left shunt at the ductus arteriosus. At 30 hours of age her oxygenation improved, and she was extubated by 4 days of age. Follow-up information was available for 11 of the surviving patients. Ten patients were examined by either of two investigators (R. M. or E. T.) and detailed information was obtained from the private physician of one patient. Only two patients showed any significant developmental delay. Both of these infants had neonatal seizures while receiving respirator care. One of the patients, E. A., had been noted to have a decreased fetal heart rate in a postmature pregnancy. The infant was heavily meconium stained and flaccid at birth, with 1 and 5 minute Apgar scores of 2 and 6, respectively. Large amounts of meconium were suctioned from the trachea under direct vision, but the infant had spontaneous respirations at 1 minute. Severe seizures occurred at 9 hours of age, associated with severe apnea that required the use of a respirator. When seen on follow-up examination at 13 months of age, he was microcephalic (head circumference more than 2 S.D. below the mean) and had significant delay in motor function.
The other patient, R. P., had meconium staining after a vaginal delivery. Apgar score was 1 at both 1 and 5 minutes. He was intubated and placed on a respirator before transfer to St. Louis Children’s Hospital, where he remained on the respirator for 15 days. Seizures developed on the second day of life. On followup examination at 8 months, length and head circumference were at the third percentile and the patient performed at the 6 to 7 month level. All other children had normal developmental parameters on follow-up examination. All patients at the time of discharge from the neonatal unit had no evidence of clinical pulmonary disease. No patient had significant intercurrent pulmonary problems as determined by careful questioning of parents at the followup examination. Initial chest roentgenogram (Figs. 1 and 2) demonstrated pulmonary infiltrates ranging from mild to severe. Air trapping was present when the disease was more than mild. Follow-up chest roentgenograms were obtained on eight of the 11 children. Two asymptomatic patients had evidence of small residual densities suggestive of old inflammatory lung disease. However, the amount of pulmonary disease on the original chest roentgenogram had no correlation with patient survival, residual seen on followup roentgenogram, or subsequent neurologic abnormalities.
Comment MAS is a significant clinical problem in neonatal intensive-care units. During 1974, 3.7 per cent of admissions to a regional referral neonatal intensive-care unit at St. Louis Children’s Hospital had MAS. From the obstetric viewpoint, about 8 to 10 per cent of all pregnancies will be accompanied by meconium staining of the amniotic fluid. i* 2 About 20 per cent of pregnancies with meconium-stained fluid (or 1 to 2 per cent of all pregnancies) may result in patients with MAS.
Meconium
Days before back on
Duration sq@. oqp above 507~ (days)
Duration supP1. oqgen below 5OYe
0
1.1 2 0.6
1.1 f 0.6
3.0 + 2
5.3 t- 2.4
8.3 -c 2.7
fdW
-
room air
-
The typical patient with MAS is a term or postterm infant with a birth weight about 2,500 grams. Cardiorespiratory symptoms usually dominate the early clinical course of most of these patients. The underlying pathophysiology responsible for the clinical respiratory distress observed is not clear. The hypoxemia observed with MAS might be related to true right-toleft shunts in which blood goes into the arterial system without going through ventilated areas of lung. Alternatively, hypox,:mia might he due’ to a ventilationperfusion abnormality in which there is a mismatch between blood How and ventilation. Corbet and Burnand7 demonstrated that hypoxemia in 12 patients with MAS was related to both true right-to-left shunts and ventilation-perfusion abnormalities. However, they suggested that ventilation-perfusion abnormalities were more significant than right-to-left shunts.’ Our data from calculated initial shunts do not permit us to distinguish between these two possible explanations for hypoxemia. However, it is of interest that in our study those patients with the most severe initial shunts either died or required the respirator (see Table I). Two of‘ our patients required cardiac catheterization to exclude the possibility that their hypoxemia was caused bv congenital heart disease. In both cases, elevated pulmonary artery pressures were found without structural heart defects. Our patients fit the description of the recently described syndrome of persistence of the fetal or transitional circulation (PFC).Hz ’ PFC patients. usually term infants, present with profound cyanosis and hypoxemia within the first 24 hours of’ life; many conditions have been associated with PFC, hut the consistent abnormality has been elevated pressure in the pulmonary artery with right-to-left shunting through the ductus arteriosus and foramen ovale. The association we described between the MAS and PFC has recently been suggested but has not been substantiated previously by cardiac catheterization.‘O It could be that MAS resulted in hypoxemia, which is
aspiration
syndrome
675
known to increase pulmonary vascular !.t.ristanct..” Little information is available on the morbidity associated with MAS. Stahlman” mentiontd that “nt*urological sequelae are not uncommon airrr MAS.” Kachaner and associate9 reported on 65 patients with MAS seen in Paris from 1965 to IY6ix. f:ollow-up information was available on 28 (43 per < ent) patients and 19 (68 per cent) of the 28 were oxen bet\+ecn 2 and 4 months of age. ‘Two patients had rcspn.arorv abnormalities and one patient had psychomc~tc~t- retardation and seizures. Two of our three survivot \ with neonatal seizures had significant developmental deficits. ‘l‘he presumed etiology of the seizures tr-il h M.4S was hypoxic-ischemic encephalopathy. Our ob$iervations are consistent with those of Rose and I.omhroso.“’ who reported significant sequelae in ahout %I per c.tbnt of survivors with neonatal seizurtrq l-esultirrg f’rcjm hypoxic-ischemic encephalopaths. Reported mortality rates ti,r MAS v;try t rem 1Y to :\4 per cent. ‘, I4 The mortality ratr in our \t.rit.s \\;ts f;)rlt of I’i (23.5 per cent). .4lI patients died within 21 hours of admission in acute respiratory 1-lilu~~~ despite assisted ventilation from the respirator,. <)III results cornpare favorably with others for sur\,iv,tl \\ itI1 M.4S patients on the respirator. Mortalit) l’dtc\ JS high as 30 per cent have been reported, but in OIII‘ ,cGs :56 per cent of MAS patients on the respirator d~cd.’ Recent data suggest that effect& prrtn;tt;tl collahoration can markedly reduce the mortalit v I ;ite nssociated with MAS. In the deliver\ gloom. i ircg01.y a11t1 colleagues” suctioned both upper and loTtc*r ;rirwavs ot 80 patients with meconium-st?intftl flultl. -ihose l)atients with meconium reco\rered tram the t t,ac.hca or an abnormal chest roentgenogram rccrivcd thoractc ph),siotherapy and postural drainage. I’hcrc q\ 1‘t.c no deaths in their 80 patients. Carson and ~olleag~~ec” rcc:entl\ reported on a combined obstetric and peciiatric approach to meconium-stained infants. i )bstetricians suctioned the oral nasopharynx it-hilt: the :ttf,tnt’s head, was still on the perineum. The latynr \;;$4 ro~ltineh inspected by the pediatricians and tracheal stwtiw w;ts performed if meconium was present. l‘11er~ wc’rc IIO deaths in 23 patients with respiratory cli\trt.ss trorn the 661 deliveries with tneconium-stained fluid. I‘hese lesults contrast to an earlier eaperiencr \vithottt ;I wmbined approach when I I per cent ot‘ p:ttict:ts \\.irh LIAS died.” It is our hope that the experienc-r reportctl in outNICU will help foster joint efforts like thr!Tr ot Gregory and Carson and their associates. We thank Drs. Fernando Arias, Philip R. Dodge, and M. Michael Maurer for their editorial assistance.
676
Marshall et al.
REFERENCES
1. Desmond, M., Moore, J., Lindley, J., and Brown, C.: Meconium staining of the amniotic fluid: A marker of fetal hypoxia, Obstet. Gynecol. 9: 91, 1957. 2. Gregory, G., Gooding, C., Phibbs, R., and Tooley, W.: Meconium aspiration in infants-A prospective study, J. Pediatr. 85: 848, 1974. 3. Kachaner, J., Huault, G., Joly, J., and Saint-Martin: La de’tresse re’spiratoire du nouveau-& par inhalation massive de liquid amniotique: Etude de 65 observations, Arch. Franc. Pediatr. 26: 743, 1969. 4. Vidyasagar, D., Yeh, T., Harris, V., and Pildes, R.: Assisted ventilation in infants with meconium aspiration svndrome. Pediatrics 56: 208. 1975. 5. Fbx, W., Berman, L. S., Dowries, J., and Peckham, G.: The therapeutic application of end-expiratory pressure in the meconium aspiration syndrome, Pediatrics 56: 214, 1975. 6. Avery, M. E., and Fletcher, B. D.: The Lung and Its Disorders in the Newborn Infant, Philadelphia, 1974, W. B. Saunders Company, pp. 64-67. 7. Corbet, A. J., and Burnand, E. D.: Changes of venous admixture with inspired oxygen in hyaline membrane disease and foetal aspiration pneumonia, Aust. Paediatr. J. 9: 25, 1973.
July
15. 1978
Am. J. Obstet. Gynecol.
8. Gersony, W. M.: Persistence of the fetal circulation: A commentary, J. Pediatr. 82: 1103, 1973. 9. Brown, R., and Pickering, D.: Persistent transitional Lirculation, Arch. Dis. Child. 49: 883, 1974. 10. Goetzman, B., Sunshine, P., Johnson, J., Wennberg, R., Hackel, A., Merten, D., Bartoletti, A., and Silverman, N.: Neonatal hypoxia and pulmonary vasospasm: Response to tolazoline. 1. Pediatr. 89: 617. 1976. 11. Dawes, G. S::*Foetal and Neonatal Physiology, A Comparative Study of Changes at Birth, Chicago, 1968, Year Book Medical Publishers, Inc., pp. 85-87. 12. Stahlman, M. T.: Acute respiratory disorders in the newborn, in Avery, G., editor: Neonatology: Pathophysiology and Management of the Newborn, Philadelphia, 1975, J. B. Lippincott, p. 244. 13. Rose, A. L., and Lombroso, C. T.: Neonatal seizure states. A study of clinical pathological and electroencephalographic. features in 137 full t&m babies with a long-term follow-un. Pediatrics 45: 404. 1970. 14. Ting, P.: and Brady, J.: Tracheal suction in meconium aspiration, AM. J. OBSTET. GYNECOL. 122: 767, 1975. 15. Carson, B., Losey, R., Bowes, W., and Simmons, M.: Combined obstetrical and pediatric management of meconium staining, Pediatr. Res. 10: 459, 1976.
and follow-up
RICHARD
MARSHALL,
EILEEN
TYRALA,
study
M.D. M.D.
WILLIAM
McALISTER,
MICHAEL
SHEEHAN,
M.D. M.D.
St. Louis, Missouri One year’s experience with MAS in a neonatal intensive-care unit is analyzad with follow-up information. Seventeen pa!ients or 3.7 per cent of all admissions had MAS. Four patients (23.5 per cent) died of acute respiratory failure. Two patients with MAS and persistence of the fetal circulation required cardiac catheterization to exclude cyanotic congenital heart disease. No survivors had persistent chronic lung disease. However, two of three patients with MAS and seizures had significant psychomotor retardation at follow-up examination. (AM. J. OBSTET. GYNECOL. 131: 672, 1978.)
of amniotic fluid occurs in between 8.9 to 9.6 per cent of deliveries and often is associated with meconium staining of infants.‘, 2 In a prospective study, as many as 20 per cent of meconium-stained infants developed either pulmonary disease requiring increased ambient oxygen and/or a pneumothorax or pneumomediastinum during the first 3 days of life. We define meconium aspiration syndrome (MAS) by the following criteria: (1) the presence of meconiumstained infants, (2) abnormal chest roentgenograms consistent with aspiration pneumonitis, and (3) clinical respiratory distress in the first 24 hours of life. Previous investigations have described certain aspects of the clinical course of MAS5 but there is scant information about the prognosis of infants with MAS.3, I3 The clinical course of the acute illness and a follow-up study of all patients with MAS admitted to the neonatal intensive-care unit (NICU) at St. Louis Children’s Hospital in 1974 form the basis of this report. MECONIUM
STAINING
From the Edward Mallinckrodt Department of Pediatrics and the Mallinckrodt Institute of Radiology, Wa.shingta University School of Medicine, and the Division of Neaatology, St. Loub Children’s Hospital. Received
for
Accepted
December
publication
Reprint requests: Richard Children’s Hospital, 500 Missouri 63 1 IO.
672
July
11, 1977.
6, 1977. Marshall, M.D., S. Kingshighway,
St. Louis St. LOGY,
Methods The hospital charts of all patients admitted to the NICU St. Louis Children’s Hospital were reviewed by one investigator (M. S.). Out of 441 NICU admissions, 17 patients were judged to have MAS by the criteria described above. Obstetric records were reviewed to determine (1) use of fetal monitoring, (2) time when meconium was observed prior to delivery, (3) Apgar scores, (4) mode of suctioning, and (5) mode of resuscitation The neonatal hospital course of each patient was reviewed. Follow-up exminations on all available survivors (11 of 13) at 1 I to 18 months of age consisted of a general physical examination, chest radiographs, developmental history, Denver developmental examination, and a specific history to determine intercurrent respiratory illnesses. Analysis of the obstetric records revealed that meconium was noted in the amniotic fluid more than 1 hour prior to delivery in six of 17 cases. Only one of these six deliveries in which meconium was recognized was monitored thereafter. Fifteen infants were vertex presentations and delivery was accomplished easily; two infants were delivered with difficulty-one because of a shoulder dystocia and one because of a transverse lie. Information about the type of suctioning received in the delivery room was available for 14 of 17 patients. Six patients received bulb syringe suctioning of the nasopharynx and posterior oral pharynx. Four pa000%9378/78/06131-0672$00,50/OO
1978 The C. V. Mosby Co
Volume Number
Meconium aspiration syndrome
151 6
Fig. 2. Chest roentgenograms. A, Initial: narv infiltrates a1.e shown. R, One nwnth
673
widespread pulmo-
Fig. 1. Chest roentgenograms. ‘4, Initial; there are intrinsic pulmonary infiltrates. B, One vear later; complete resolution has occurred.
is ndrmal.
tients received tracheal suctioning under direct larynoscopic visualization of the cords. One of the infants who died had direct tracheal suctioning. Three of the six infants who lived and required respiratory therapy had direct tracheal suctioning. Two patients were thought to be postterm by dates before delivery. However, pediatric physical examination suggested that seven infants were postmature. Three of the four deaths occurred in patients who were recognized as postmature after birth. Apgar scores at 1 and 5 minutes were higher in survivors and in more infants who did not require the respirator. Patients were divided into three categories: Group I, survivors who did not require respirator therapy (N = 7); Group II, survivors who required respirator therapy (N = 6); Group III. those who died (N = 4). Salient features of the clinical course are summarized in Table I. Patients in Group II who survived required the res-
pirator for a mean of 5.2 days. Those who died on the respirator did so within 24 hours. Group I1 patients were exposed to higher concentrations of inspired oxygen then were thostb in Group I. Calculations were made to estimate the percentage of cardiac output that was shunted right-to-left at the time initial blood gases were determined! Shunting was greatest in the patients who died. Patients in Group II had more shunting than patients in (iroup 1, who did not require the respirator. Two patients in Group II had clinical courses of particular interest which will be presented in detail. ‘They both had inadequate oxygenation on 100 per cent inspired oxygen, suggesting the possibility that they had cardiac disease superimposed upon MRS. .& an exarnpie, A. M. was born after a labor complic;~trd by maternal fever and shoulder dystocia. .Fhr I and .? minute Apgar scores were 1 and 5 despite tracheal suctioning done under direct visualization. ‘l‘his patient was plactd on the Bournes respirator immediately after
later.
the chest
film
674
Table
Marshall
et al.
I. Salient
July 1.5, I978 Am. J. Obstet. Gynerol.
features
of clinical
courses Apgar
Birth wt. (Gm.)
Group I, living, no respirator (N = 7) Group II, living, respirator (N -7) Group III, dead, respirator
scores
Resp.
rate
60, tachypaea 1 min.
(days)
Duration resp. therapy (days)
7.2
f 1.0
3.4 + 1.4
18.7
f 1.1
-
2.8 Y!I 0.7
4.3
+ 1
9.8 2 3.5
54.3
+ 9.7
5.2 + 2.3
1.8 -+ 0.3
2.5 t 0.8
-
80.
2 15
3,385
f 289
4.6
2,353
~~228
3,538
2 213
r 1.1
5 min.
Cardiac output, shunted R-L, initial blood gases (%,J
-
(N =4)
birth and required 100 per cent inspired oxygen with a positive end-expiratory pressure of 4 cm. H,O to maintain a Pa, of less than 45 mm. Hg. Cardiac catheterization on day 2 demonstrated systemic pressure in the right ventricle, patent foramen ovale, and a large patent ductus arteriosus. She gradually improved but required respirator care for 11 days. Another patient, M. C., was born postmaturely with gross meconium staining and had 1 and 5 minute Apgar scores of 4 and 4, respectively. Meconium was suctioned from the trachea in the delivery room under direct visualization. Shortly after birth, she was placed on a Bournes respirator with 100 per cent inspired oxygen and 3 cm. HZ0 positive end-expiratory pressure. Inadequate oxygenation resulted in cardiac catheterization, whereupon she was found to have elevated pulmonary artery and right ventricular pressure with a large right-to-left shunt at the ductus arteriosus. At 30 hours of age her oxygenation improved, and she was extubated by 4 days of age. Follow-up information was available for 11 of the surviving patients. Ten patients were examined by either of two investigators (R. M. or E. T.) and detailed information was obtained from the private physician of one patient. Only two patients showed any significant developmental delay. Both of these infants had neonatal seizures while receiving respirator care. One of the patients, E. A., had been noted to have a decreased fetal heart rate in a postmature pregnancy. The infant was heavily meconium stained and flaccid at birth, with 1 and 5 minute Apgar scores of 2 and 6, respectively. Large amounts of meconium were suctioned from the trachea under direct vision, but the infant had spontaneous respirations at 1 minute. Severe seizures occurred at 9 hours of age, associated with severe apnea that required the use of a respirator. When seen on follow-up examination at 13 months of age, he was microcephalic (head circumference more than 2 S.D. below the mean) and had significant delay in motor function.
The other patient, R. P., had meconium staining after a vaginal delivery. Apgar score was 1 at both 1 and 5 minutes. He was intubated and placed on a respirator before transfer to St. Louis Children’s Hospital, where he remained on the respirator for 15 days. Seizures developed on the second day of life. On followup examination at 8 months, length and head circumference were at the third percentile and the patient performed at the 6 to 7 month level. All other children had normal developmental parameters on follow-up examination. All patients at the time of discharge from the neonatal unit had no evidence of clinical pulmonary disease. No patient had significant intercurrent pulmonary problems as determined by careful questioning of parents at the followup examination. Initial chest roentgenogram (Figs. 1 and 2) demonstrated pulmonary infiltrates ranging from mild to severe. Air trapping was present when the disease was more than mild. Follow-up chest roentgenograms were obtained on eight of the 11 children. Two asymptomatic patients had evidence of small residual densities suggestive of old inflammatory lung disease. However, the amount of pulmonary disease on the original chest roentgenogram had no correlation with patient survival, residual seen on followup roentgenogram, or subsequent neurologic abnormalities.
Comment MAS is a significant clinical problem in neonatal intensive-care units. During 1974, 3.7 per cent of admissions to a regional referral neonatal intensive-care unit at St. Louis Children’s Hospital had MAS. From the obstetric viewpoint, about 8 to 10 per cent of all pregnancies will be accompanied by meconium staining of the amniotic fluid. i* 2 About 20 per cent of pregnancies with meconium-stained fluid (or 1 to 2 per cent of all pregnancies) may result in patients with MAS.
Meconium
Days before back on
Duration sq@. oqp above 507~ (days)
Duration supP1. oqgen below 5OYe
0
1.1 2 0.6
1.1 f 0.6
3.0 + 2
5.3 t- 2.4
8.3 -c 2.7
fdW
-
room air
-
The typical patient with MAS is a term or postterm infant with a birth weight about 2,500 grams. Cardiorespiratory symptoms usually dominate the early clinical course of most of these patients. The underlying pathophysiology responsible for the clinical respiratory distress observed is not clear. The hypoxemia observed with MAS might be related to true right-toleft shunts in which blood goes into the arterial system without going through ventilated areas of lung. Alternatively, hypox,:mia might he due’ to a ventilationperfusion abnormality in which there is a mismatch between blood How and ventilation. Corbet and Burnand7 demonstrated that hypoxemia in 12 patients with MAS was related to both true right-to-left shunts and ventilation-perfusion abnormalities. However, they suggested that ventilation-perfusion abnormalities were more significant than right-to-left shunts.’ Our data from calculated initial shunts do not permit us to distinguish between these two possible explanations for hypoxemia. However, it is of interest that in our study those patients with the most severe initial shunts either died or required the respirator (see Table I). Two of‘ our patients required cardiac catheterization to exclude the possibility that their hypoxemia was caused bv congenital heart disease. In both cases, elevated pulmonary artery pressures were found without structural heart defects. Our patients fit the description of the recently described syndrome of persistence of the fetal or transitional circulation (PFC).Hz ’ PFC patients. usually term infants, present with profound cyanosis and hypoxemia within the first 24 hours of’ life; many conditions have been associated with PFC, hut the consistent abnormality has been elevated pressure in the pulmonary artery with right-to-left shunting through the ductus arteriosus and foramen ovale. The association we described between the MAS and PFC has recently been suggested but has not been substantiated previously by cardiac catheterization.‘O It could be that MAS resulted in hypoxemia, which is
aspiration
syndrome
675
known to increase pulmonary vascular !.t.ristanct..” Little information is available on the morbidity associated with MAS. Stahlman” mentiontd that “nt*urological sequelae are not uncommon airrr MAS.” Kachaner and associate9 reported on 65 patients with MAS seen in Paris from 1965 to IY6ix. f:ollow-up information was available on 28 (43 per < ent) patients and 19 (68 per cent) of the 28 were oxen bet\+ecn 2 and 4 months of age. ‘Two patients had rcspn.arorv abnormalities and one patient had psychomc~tc~t- retardation and seizures. Two of our three survivot \ with neonatal seizures had significant developmental deficits. ‘l‘he presumed etiology of the seizures tr-il h M.4S was hypoxic-ischemic encephalopathy. Our ob$iervations are consistent with those of Rose and I.omhroso.“’ who reported significant sequelae in ahout %I per c.tbnt of survivors with neonatal seizurtrq l-esultirrg f’rcjm hypoxic-ischemic encephalopaths. Reported mortality rates ti,r MAS v;try t rem 1Y to :\4 per cent. ‘, I4 The mortality ratr in our \t.rit.s \\;ts f;)rlt of I’i (23.5 per cent). .4lI patients died within 21 hours of admission in acute respiratory 1-lilu~~~ despite assisted ventilation from the respirator,. <)III results cornpare favorably with others for sur\,iv,tl \\ itI1 M.4S patients on the respirator. Mortalit) l’dtc\ JS high as 30 per cent have been reported, but in OIII‘ ,cGs :56 per cent of MAS patients on the respirator d~cd.’ Recent data suggest that effect& prrtn;tt;tl collahoration can markedly reduce the mortalit v I ;ite nssociated with MAS. In the deliver\ gloom. i ircg01.y a11t1 colleagues” suctioned both upper and loTtc*r ;rirwavs ot 80 patients with meconium-st?intftl flultl. -ihose l)atients with meconium reco\rered tram the t t,ac.hca or an abnormal chest roentgenogram rccrivcd thoractc ph),siotherapy and postural drainage. I’hcrc q\ 1‘t.c no deaths in their 80 patients. Carson and ~olleag~~ec” rcc:entl\ reported on a combined obstetric and peciiatric approach to meconium-stained infants. i )bstetricians suctioned the oral nasopharynx it-hilt: the :ttf,tnt’s head, was still on the perineum. The latynr \;;$4 ro~ltineh inspected by the pediatricians and tracheal stwtiw w;ts performed if meconium was present. l‘11er~ wc’rc IIO deaths in 23 patients with respiratory cli\trt.ss trorn the 661 deliveries with tneconium-stained fluid. I‘hese lesults contrast to an earlier eaperiencr \vithottt ;I wmbined approach when I I per cent ot‘ p:ttict:ts \\.irh LIAS died.” It is our hope that the experienc-r reportctl in outNICU will help foster joint efforts like thr!Tr ot Gregory and Carson and their associates. We thank Drs. Fernando Arias, Philip R. Dodge, and M. Michael Maurer for their editorial assistance.
676
Marshall et al.
REFERENCES
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8. Gersony, W. M.: Persistence of the fetal circulation: A commentary, J. Pediatr. 82: 1103, 1973. 9. Brown, R., and Pickering, D.: Persistent transitional Lirculation, Arch. Dis. Child. 49: 883, 1974. 10. Goetzman, B., Sunshine, P., Johnson, J., Wennberg, R., Hackel, A., Merten, D., Bartoletti, A., and Silverman, N.: Neonatal hypoxia and pulmonary vasospasm: Response to tolazoline. 1. Pediatr. 89: 617. 1976. 11. Dawes, G. S::*Foetal and Neonatal Physiology, A Comparative Study of Changes at Birth, Chicago, 1968, Year Book Medical Publishers, Inc., pp. 85-87. 12. Stahlman, M. T.: Acute respiratory disorders in the newborn, in Avery, G., editor: Neonatology: Pathophysiology and Management of the Newborn, Philadelphia, 1975, J. B. Lippincott, p. 244. 13. Rose, A. L., and Lombroso, C. T.: Neonatal seizure states. A study of clinical pathological and electroencephalographic. features in 137 full t&m babies with a long-term follow-un. Pediatrics 45: 404. 1970. 14. Ting, P.: and Brady, J.: Tracheal suction in meconium aspiration, AM. J. OBSTET. GYNECOL. 122: 767, 1975. 15. Carson, B., Losey, R., Bowes, W., and Simmons, M.: Combined obstetrical and pediatric management of meconium staining, Pediatr. Res. 10: 459, 1976.