Delivery Room Management of the Apparently Vigorous Meconium-stained Neonate: Results of the Multicenter, International Collaborative Trial

Delivery Room Management of the Apparently Vigorous Meconium-stained Neonate: Results of the Multicenter, International Collaborative Trial

Thomas E. Wiswell

ABBREVIATIONS. MSAF, meconium-stained amniotic fluid; MAS, meconium aspiration syndrome; INT, intubated and suctioned; EXP, expectant management; FHR, fetal heart rate; OR, odds ratio; CI, 95% confidence interval.

Approximately 13% of liveborn infants are born through meconium-stained amniotic fluid (MSAF).[1,2] Of the neonates born through MSAF, 5% to 12% develop the meconium aspiration syndrome (MAS).[1,2] Reports from the mid-1970s suggested that intratracheal suctioning of meconium-stained infants could prevent development of MAS and decrease mortality from the disorder.[3,4] Although these latter investigations were only observational studies, after their publication the strategy of intubation and suctioning the tracheae of all meconium-stained infants was widely adopted. During the decade after the publication of these reports, the incidence of MAS and deaths attributable to the disorder declined significantly.[5]

In 1988, Linder and colleagues[6] reported that the apparently vigorous meconium-stained infant may not need intratracheal suctioning and that such therapy could be harmful. Despite major design flaws in the Linder trial,[7-10] Cunningham et al[11] proposed a standard of care in which only depressed meconium-stained neonates needing positive pressure ventilation would receive intratracheal suctioning in the delivery room. Although some investigators subsequently reported that such an approach could be deleterious,[12] others found a selective approach generally to result in good outcomes.[13,14] Essentially, however, there was no well-designed research supporting either universal or selective intubation of the meconium-stained neonate.

Potential complications of neonatal intubation[15] include bradycardia, perforation of the larynx or pharynx, dislocation of the vocal cords, hoarseness or stridor, hypoxemia, and apnea. Although these complications are believed to be rare, no studies have yet documented their frequency of occurrence.

We performed this investigation: 1) to assess whether intubation and suctioning of the apparently vigorous meconium-stained neonate would reduce the incidence of MAS, and 2) to determine the frequency of complications from delivery room intubation and suctioning of such infants.

METHODS

This was a prospective, randomized, controlled trial in which 12 centers enrolled patients between July 1995 and September 1997. The protocol was adopted for this investigation and approved by the institutional review boards of the participating sites. This was a no informed consent protocol. The rationale for this included: 1) wide acceptance of both proposed management strategies (universal vs selective intubation) as standards of care; 2) MSAF is frequently not noted until moments before delivery, obviating the ability to counsel parents; and 3) inherent difficulties in obtaining valid informed consent from a mother undergoing the pain of labor. We estimated that if we were to attempt to obtain informed consent, even during prenatal visits, at most we would only be able to enroll 70% of eligible infants. Moreover, the population of enrolled neonates would not be representative of the entire population of infants born through MSAF. Potentially, many infants at higher risk for developing MAS would be excluded (eg, those delivered via emergency cesarean section). The protocol satisfied the requirements for waiver of informed consent found in the Combined Federal Regulations developed by the Department of Health and Human Services for the protection of human research subjects (45 Combined Federal Regulations 46.116[d]). Because of the uniqueness of waiving informed consent, several invited ethicists and neonatologists were involved in the review process. In addition, the Steering Committee of the American Academy of Pediatrics/American Heart Association Neonatal Resuscitation Program wrote a supportive letter stating investigation was sorely needed and quite ethical to perform without requiring informed consent.

To incorporate the widespread varieties of clinical practice, participating sites were chosen in an effort to include both university-affiliated hospitals and predominantly clinical centers. The inclusion criteria were: 1) meconium presence in the amniotic fluid; 2) gestational age of [is greater than or equal to] 37 weeks; and 3) apparent vigor of the child in the delivery room immediately after birth, defined by a heart rate [is greater than] 100 beats per minute, as well as presence of spontaneous respirations and reasonable tone. Reasonable tone was believed to be present if the child was exhibiting either spontaneous movements or had some degree of extremity flexion. The degree of vigor was assessed within the first 10 to 15 seconds after delivery. The MSAF could be of any consistency. For this trial, MSAF consistency was classified in the following manner: 1) thin MSAF was a watery consistency fluid through which an individual potentially could read newspaper print if the fluid was on the paper; 2) moderate or moderately-thick MSAF was an opaque fluid without particles; and 3) thick MSAF was fluid of pea soup consistency or opaque fluid containing particulate material. Additionally, MAS was defined as respiratory distress in an infant born through MSAF whose symptoms could not be otherwise explained and who had consistent radiographic findings (eg, coarse, irregular infiltrates, hyperinflation, and/or segmental or lobar atelectasis). The obstetrical policy at all sites was to suction the oropharynx of each meconium-stained neonate with either a catheter (attached to wall suction) or bulb syringe before delivery of the infant’s shoulders or trunk.

Infants were randomized to intubation and intratracheal suctioning (INT) or to expectant management (EXP). Computer-generated random numbers were used for assignment to these groups. Group selection was determined by drawing assignments from a sealed opaque envelope, which was opened immediately before deliveries complicated by meconium staining. When a neonate did not meet the criteria for apparent vigor, the child was excluded from the study and randomization assignment was discarded. Infants assigned to the INT group were intubated immediately after birth following the assessment for vigor. A standard meconium suction device, the Neotech aspirator (Neotech, Inc, Chatsworth, CA) was connected to the proximal end of the child’s endotracheal tube and attached to wall suction set at 80 to 120 mm Hg negative pressure. Suction was applied continuously for 1 to 5 seconds and as the endotracheal tube was withdrawn. If meconium was suctioned from the trachea, the procedure was repeated until no additional meconium-stained fluid could be retrieved. Infants randomized to EXP had routine delivery room care. After initial stabilization and assessment, EXP infants potentially could manifest signs of respiratory distress. Therefore, health care providers were allowed to intubate and suction such infants if they believed it was clinically indicated. Extensive antenatal, intrapartum, and postnatal data were collected on a standardized form that was forwarded to a central facility for entry into a database. All investigators remained blinded to results until completion of the trial. An independent data safety and monitoring committee assessed data one third and two thirds of the way through enrollment.

Data Analysis

Published data from several sources[1,2,5,6,13,14] were used to calculate sample size. We hypothesized that compared with EXP, intratracheal suctioning of apparently vigorous meconium-stained neonates would decrease the incidence of MAS from 3% to 1%. To demonstrate such a difference, at [Alpha] = .05 with 90% power, a minimum of 1029 infants were needed in each group (2058 total). The INT and EXP groups were analyzed on an intention to treat basis. Univariate analyses, including 2-group t test, Wilcoxon rank sum test, two-tailed Fisher’s exact test, and the Mantel-Haenszel [chi square] test, were initially used to compare the groups. Stepwise logistic regression was subsequently used to evaluate the effect of various factors on the occurrence of MAS or other respiratory disorders independent of the potentially confounding effects of other variables. The logistic regressions were conducted on SAS Version 6.08,[16] and goodness of fit was determined by the Hosmer-Lemeshow statistic.[17]

RESULTS

A total of 2094 infants were enrolled in the trial, 1051 in the intubate group and 1043 in the expectant management group. Of the 12 participating sites, 6 enrolled between 197 and 408 neonates, whereas the remaining 6 sites cumulatively enrolled a total of 227 infants. Of the 6 sites that enrolled 197 or more infants, 4 kept data concerning all meconium-stained infants (both apparently vigorous and those that were not). Fully 74% of all meconium-stained infants from these 6 sites fit the criteria of being apparently vigorous at the time of initial evaluation. Selected antenatal and intrapartum characteristics for the entire population are presented in Table 1. There were no differences between groups in maternal age, maternal gravidity or parity, amount of prenatal care, presence of oligohydramnios, consistency of MSAF, use of amnioinfusion therapy, application of electronic fetal heart rate (FHR) monitoring during labor, occurrence of abnormal FHR monitoring, use of oropharyngeal suctioning, or method of delivery.

TABLE 1. Antenatal and Intrapartum Population Characteristics

Intubate (n = 1051)

Maternal age (mean [+ or -] standard

deviation) 25.4 [+ or -] 1.3

Maternal birth history

Gravidity, median (range) 2 (1-9)

Parity, median (range) 1 (0-8)

Prenatal care

<5 visits 130 (12.4%)

[is greater than or equal to] 5 visits 921 (87.6%)

Presence of oligohydramnios 28 (2.7%)

Meconium consistency

Thin 447 (42.5%)

Moderately thick 301 (28.6%)

Thick 303 (28.8%)

Electronic fetal heart rate monitoring 820 (78.0%)

performed

Abnormal electronic fetal heart rate 274 (33.4%)

during labor

Use of amnioinfusion 73 (6.9%)

Oropharyngeal suctioning before delivery

of shoulders

Not performed (n = 94) 46 (4.4%)

Performed (n = 2000) 1005 (95.6%)

Method of delivery

Vaginal, overall (n = 1639) 817 (77.7%)

Noninstrumented, (n = 1394) 705 (67.1%)

Vacuum-assisted (n = 113) 52 (4.9%)

Forceps-assisted (n = 115) 54 (5.1%)

Both vacuum- and forceps-assisted (n = 17) 6 (.6%)

Cesarean, overall (n = 455) 234 (22.3%)

Elective (n = 130) 62 (5.9%)

For fetal distress (n = 325) 172 (16.4%)

Expectant (n = 1043)

Maternal age (mean [+ or -] standard

deviation) 24.9 [+ or -] 1.4

Maternal birth history

Gravidity, median (range) 2 (1-13)

Parity, median (range) 1 (0-12)

Prenatal care

<5 visits 139 (13.3%)

[is greater than or equal to] 5 visits 904 (86.7%)

Presence of oligohydramnios 18 (1.7%)

Meconium consistency

Thin 453 (43.4%)

Moderately thick 307 (29.4%)

Thick 283 (27.1%)

Electronic fetal heart rate monitoring 829 (79.5%)

performed

Abnormal electronic fetal heart rate 269 (32.4%)

during labor

Use of amnioinfusion 65 (6.2%)

Oropharyngeal suctioning before delivery

of shoulders

Not performed (n = 94) 48 (4.6%)

Performed (n = 2000) 995 (95.4%)

Method of delivery

Vaginal, overall (n = 1639) 822 (78.8%)

Noninstrumented, (n = 1394) 689 (66.1%)

Vacuum-assisted (n = 113) 61 (5.8%)

Forceps-assisted (n = 115) 61 (5.8%)

Both vacuum- and forceps-assisted (n = 17) 11 (1.1%)

Cesarean, overall (n = 455) 221 (21.2%)

Elective (n = 130) 68 (6.5%)

For fetal distress (n = 325) 153 (14.7%)

Significance

Maternal age (mean [+ or -] standard

deviation) NS

Maternal birth history

Gravidity, median (range) NS

Parity, median (range) NS

Prenatal care

<5 visits NS

[is greater than or equal to] 5 visits NS

Presence of oligohydramnios NS

Meconium consistency

Thin NS

Moderately thick NS

Thick NS

Electronic fetal heart rate monitoring NS

performed

Abnormal electronic fetal heart rate NS

during labor

Use of amnioinfusion NS

Oropharyngeal suctioning before delivery

of shoulders

Not performed (n = 94) NS

Performed (n = 2000) NS

Method of delivery

Vaginal, overall (n = 1639) NS

Noninstrumented, (n = 1394) NS

Vacuum-assisted (n = 113) NS

Forceps-assisted (n = 115) NS

Both vacuum- and forceps-assisted (n = 17) NS

Cesarean, overall (n = 455) NS

Elective (n = 130) NS

For fetal distress (n = 325) NS

NS indicates not significant.

Selected characteristics of the infant population are presented in Table 2. There were no differences between groups in racial background, gender, or 5-minute Apgar scores. The INT group subjects were significantly more likely to have lower 1-minute Apgar scores (P [is less than] .0018). A total of 62 meconium-stained infants (3.0%) developed MAS, and an additional 87 (4.2%) were diagnosed with other respiratory disorders including: transient tachypnea of the newborn (n = 52), delayed transition from fetal circulation (n = 16), sepsis or pneumonia (n = 10), persistent pulmonary hypertension of the newborn (n = 3), pulmonary edema (n = 3), pneumothorax (n = 2), hypovolemia (n = 1), and blood aspiration (n = 1). Across sites there was little variation in the frequency of MAS (2.2%-3.5%) or other respiratory disorders (3.4%-5.2%). There were no significant differences between INT and EXP in the incidence of MAS (3.2% vs 2.7%, respectively) or other respiratory disorders (3.8% vs 4.5%, respectively). Additionally, the thicker the MSAF consistency, the more likely the development of either MAS or other respiratory disorders. However, even in the presence of the thickest consistency MSAF, intratracheal suctioning was no better than expectant management in preventing respiratory illness. Moreover, when we put the primary endpoint (development of MAS) into a logistic regression model with other risk factors for the disorder, the results were identical; there were no differences between the intubation and expectant management groups in the incidence of MAS. Two infants required extracorporeal membrane oxygenation, I in each group. Five deaths occurred: 2 in the INT group and 3 in the EXP group. Four deaths were caused by respiratory failure, and 1 was attributable to overwhelming infection.

TABLE 2. Infant Population Characteristics

Intubate (n = 1051)

Racial background

White 483 (46.0%)

Black 234 (22.3%)

Hispanic 253 (24.1%)

Asian 73 (6.9%)

Other 8 (0.8%)

Gender

Male 530 (50.4%)

Female 521 (49.6%)

Range of 1-min Apgar scores

1-3 36 (3.5%)

4-6 139 (13.2%)

7-10 876 (83.3%)

Range of 5-min Apgar scores

1-3 0 (0%)

4-6 14 (1.3%)

7-10 1037 (98.7%)

Occurrence of MAS (n = 62)

Overall 34/1051 (3.2%)

Thin MSAF 5/447 (1.1%)

Moderately-thick MSAF 7/301 (2.3%)

Thick MSAF 22/303 (7.3%)

Occurrence of other respiratory

disorders (n = 87)

Overall 40/1051 (3.8%)

Thin MSAF 6/447 (1.3%)

Moderately-thick MSAF 10/301 (3.3%)

Thick MSAF 24/303 (7.9%)

Occurrence of any type of respiratory

distress (n = 149)

Overall 74/1051 (7.0%)

Thin MSAF 11/447 (2.5%)

Moderately-thick MSAF 17/301 (5.6%)

Thick MSAF 46/303 (15.2%)

Expectant (n = 1043)

Racial background

White 483 (46.3%)

Black 251 (24.1%)

Hispanic 233 (22.3%)

Asian 68 (6.5%)

Other 8 (0.8%)

Gender

Male 523 (50.1%)

Female 520 (49.9%)

Range of 1-min Apgar scores

1-3 14 (1.3%)

4-6 51 (4.9%)

7-10 978 (93.8%)

Range of 5-min Apgar scores

1-3 0 (0%)

4-6 8 (0.8%)

7-10 1035 (99.2%)

Occurrence of MAS (n = 62)

Overall 28/1043 (2.7%)

Thin MSAF 2/453 (0.4%)

Moderately-thick MSAF 6/307 (2.0%)

Thick MSAF 20/283 (7.1%)

Occurrence of other respiratory

disorders (n = 87)

Overall 47/1043 (4.5%)

Thin MSAF 8/453 (1.8%)

Moderately-thick MSAF 15/307 (4.9%)

Thick MSAF 24/283 (8.5%)

Occurrence of any type of respiratory

distress (n = 149)

Overall 75/1043 (7.2%)

Thin MSAF 10/453 (2.2%)

Moderately-thick MSAF 21/307 (6.8%)

Thick MSAF 44/283 (15.5%)

Significance

Racial background

White NS

Black NS

Hispanic NS

Asian NS

Other NS

Gender

Male NS

Female NS

Range of 1-min Apgar scores

1-3 P = .0018

4-6 P = .0001

7-10 P < .0001

Range of 5-min Apgar scores

1-3 NS

4-6 NS

7-10 NS

Occurrence of MAS (n = 62)

Overall NS

Thin MSAF NS

Moderately-thick MSAF NS

Thick MSAF NS

Occurrence of other respiratory

disorders (n = 87)

Overall NS

Thin MSAF NS

Moderately-thick MSAF NS

Thick MSAF NS

Occurrence of any type of respiratory

distress (n = 149)

Overall NS

Thin MSAF NS

Moderately-thick MSAF NS

Thick MSAF NS

Of 1051 INT infants, 17 (1.5%) were not intubated for several reasons, most commonly excessively difficult intubation. None of these 17 infants subsequently developed respiratory distress. Of 1043 EXP infants, 64 (6.1%) were intubated after the initial assessment period because they developed clinical symptoms that included respiratory distress, poor respiratory effort, and evidence of meconium blocking the upper airway. These 64 infants were intubated between 1 and 7 minutes of age. Of the 64 infants, 11 (17%) subsequently developed either MAS (n = 4) or other respiratory disorders (n = 7). Of 1098 successfully intubated infants (1034 from the INT group and 64 from the EXP group), 42 (3.8%) had a total of 51 complications of the procedure. Complications included bradycardia (n = 26), hoarseness or stridor (n = 14), laryngospasm (n = 6), apnea (n = 2), bleeding at the vocal cords (n = 2), and cyanosis (n = 1). Most complications were transient, lasting 15 to 60 seconds. Hoarseness or stridor lasted between 2 minutes and 12 hours.

Stepwise logistic regression revealed an association between several factors and subsequent occurrence of respiratory distress (Fig 1). Infants delivered via cesarean section were significantly more likely to develop MAS compared with vaginally delivered infants (odds ratio [OR]: 1.89; 95% confidence interval [CI]: 1.10,3.22). Among infants delivered via cesarean section, there was no difference in the occurrence of respiratory disorders between those electively delivered compared with those delivered operatively for fetal distress. Infants whose mothers had [is less than] 5 prenatal visits were significantly more likely to develop MAS compared with infants whose mothers had [is greater than or equal to] 5 prenatal visits (OR: 6.56; CI: 3.91,11.00). The occurrence of MAS increased significantly with increasing consistency of MSAF. Infants born through moderately thick MSAF were significantly more likely to develop MAS compared with those born through thin consistency MSAF (OR: 2.79; CI: 1.11,7.03). Neonates born through thick MSAF were significantly more likely to develop MAS compared with those born through either thin consistency MSAF (OR: 9.85; CI: 4.39,22.08) or moderately thick MSAF (OR: 3.93; CI: 1.88,6.65). When oropharyngeal suctioning was not performed before delivery of the shoulders, neonates were significantly more likely to develop MAS (OR: 3.35; CI: 1.55,7.27). The incidence of MAS in infants who did not have oropharyngeal suctioning was 8 of 94 (8.5%) compared with 54 of 2000 (2.7%) of infants who had such suctioning (P = .013). Among infants who had oropharyngeal suctioning, there were no differences in the occurrence of respiratory illnesses between those suctioned with a catheter and those suctioned with a bulb syringe. Among the 1098 infants who were successfully intubated, 373 (34.0%) were noted to have meconiura present in the trachea. These infants were significantly more likely to develop MAS compared with those who did not have meconium present in the trachea (OR: 3.49; CI: 1.78,6.84). Of the 1649 infants whose mothers had electronic FHR monitoring performed, when abnormalities in FHR were noted the infants were more likely to developed MAS (OR: 1.92; CI: 1.10,3.34). Amnioinfusion was performed in the mothers of 138 (6.6%) meconium-stained infants., virtually only in the presence of thick-consistency MSAF. However, use of amnioinfusion did not result in any decrease in the incidence of MAS or other respiratory disorders. The meconium-stained neonates with 1-minute (OR: 10.03; CI 5.97,16.86) or 5-minute (OR: 21.35; CI: 8.65,53.04) Apgar scores of [is less than] 7 were significantly more likely to develop MAS, as were those born in the presence of oligohydramnios (OR: 4.26; CI: 1.62, 11.18). Male infants were significantly more likely than female infants to have MAS (OR: 2.48; CI: 1.42,4.34).

[Figure 1 ILLUSTRATION OMITTED]

We similarly used stepwise logistic regression to assess whether any of the aforementioned factors were independent predictors of other causes of respiratory distress (Fig 2). We found the following factors to be independently significantly related to the development of other respiratory disorders: cesarean delivery (OR: 3.78; CI: 2.45,5.84); [is less than] 5 prenatal visits (OR: 2.11; CI: 1.26,3.53); moderately thick versus thin consistency of MSAF (OR: 2.71; CI: 1.40,5.26); thick versus thin MSAF (OR: 5.65; CI: 3.08,10.34); thick versus moderately thick MSAF (OR: 2.08; CI: 1.27,3.42); not performing oropharyngea] suctioning (OR: 2.61; CI: 1.27,4.13); meconium presence in the trachea (OR: 5.49; CI: 2.96,10.54); no use of FHR monitoring (OR: 2.76; CI: 1.77,4.28); abnormal FHR monitoring when performed (OR: 4.69; CI: 2.57,8.56); 1-minute (OR: 8.10; CI: 5.18,12.64) or 5-minute (OR: 17.70; CI: 7.34,42.62) Apgar score of [is less than or equal to] 6; and oligohydramnios (OR: 2.92; CI: 1.13,7.59). Although the frequency of other respiratory disorders was increased among male neonates, this was not an independently significant risk factor (OR: 1.49; CI: .96,2.31). The incidence of other respiratory disorders was 9 of 94 (9.6%) in infants who did not have oropharyngeal suctioning compared with 78 of 2000 (3.9%) of infants who had such suctioning (P = .007).

[Figure 2 ILLUSTRATION OMITTED]

Of the infants with MAS, 30 (48%) needed support with either mechanical ventilation (n = 24) or continuous positive airway pressure (n = 6) compared with 13 (15%) of those with other respiratory disorders (P [is less than] .0001). The need for increasing levels of respiratory support was significantly related to MSAF consistency but not to other variables (Table 3). We assessed the relationship between the level of experience and training of the clinicians performing intubation and suctioning to the occurrence of MAS. Of the 1098 intubation procedures, 176 (16.0%) were performed by pediatric residents, 147 (13.4%) by neonatology fellows, 467 (42.5%) by attending neonatologists, 305 (27.8%) by neonatal nurse practitioners, and the remaining 3 (.3%) were performed by an obstetrician, a respiratory therapist, and an anesthesiologist, respectively. There were no significant differences in the occurrence of MAS or other respiratory distress based on the differing levels of experience and training.

TABLE 3. Maximum Respiratory Support Needed and Relationship to Consistency of MSAF Among 149 Infants Apparently Vigorous Meconium-Stained Infants With Respiratory Distress

Thin Consistency MSAF

(n = 900)

No support 12 (1.3%)

Oxygen only 5 (.6%)

CPAP only 1 (.1%)

Mechanical ventilation only 3 (.3%)

CPAP or mechanical ventilation 4 (.4%)

Moderately-Thick Consistency

MSAF (n = 608)

No support 3 (.5%)

Oxygen only 29 (4.8%)(*)

CPAP only 2 (.3%)

Mechanical ventilation only 4 (.7%)

CPAP or mechanical ventilation 6 (1.0%)

Thick Consistency MSAF

(n = 586)

No support 2 (.3%)

Oxygen only 55 (9.4%)([dagger])

CPAP only 11 (1.9%)([double dagger])

Mechanical ventilation only 22 (3.8%)([sections])

CPAP or mechanical ventilation 33 (5.6%)([parallel])

CPAP indicates continuous positive airway pressure.

(*) Infants with respiratory distress born through moderately-thick MSAF were significantly more likely to require oxygen than those born through thin MSAF (P (.0001).

([dagger]) Infants with respiratory distress born through thick consistency MSAF were significantly more likely to require oxygen than those born through either thin MSAF (P (.0001) or moderately-thick MSAF (P = .0023).

([double dagger]) Infants with respiratory distress born through thick consistency MSAF were significantly more likely to require CPAP than those born through either thin MSAF (P = .0006) or moderately-thick MSAF (P = .0216).

([sections]) Infants with respiratory distress born through thick consistency MSAF were significantly more likely to require mechanical ventilation than those born through either thin MSAF (P (.0001) or moderately-thick MSAF (P = .0005).

([parallel]) Infants with respiratory distress born through thick consistency MSAF were significantly more likely to require either CPAP or mechanical ventilation than those born through either thin MSAF (P < .0001) or moderately-thick MSAF (P < .0001).

DISCUSSION

In this trial, we found routine suctioning of the apparently vigorous meconium-stained infant to be no better than expectant management in preventing MAS or other respiratory disorders. Additionally, we found the infrequent complications of routine intubation and suctioning to be minor and short-lived. MAS is a common cause of respiratory distress in newborn infants around the world.[1,2] Historically, as many as 62% of infants born through MSAF subsequently suffered respiratory distress.[18] Although intratracheal suctioning of the meconium-stained neonate was proposed initially in 1960,[19] it was not until the mid-1970s that direct tracheal suctioning was reported to be effective in preventing MAS.[3,4] Although the latter reports only represented anecdotal experience, not prospective, randomized, controlled trials, after their publication there was widespread acceptance of the practice of intubating and suctioning the tracheae of all meconium-stained infants. In the subsequent decade, the incidence of MAS and deaths attributable to the disorder significantly declined.[5] In 1988, Linder and colleagues[6] suggested that nondepressed meconium-stained infants would not benefit from intratracheal suctioning. A number of issues were raised concerning their trial.[7-10] They did not randomize all enrolled subjects. They excluded all infants delivered via cesarean section or vaginally with instrument assistance. There was a remarkably high incidence of meconiumstained infants with 1-minute Apgar scores of [is greater than or equal to] 9 ([is greater than] 90%), as well as a remarkably low frequency of MAS (.7%). Nevertheless, based on the results of the Linder trial, selective intubation was proposed as a standard of care.[11] Several authors[13,14] retrospectively reviewed delivery room management in their own institutions and concluded that a selective approach was justified. However, others[12,20] concluded that universal intubation and suctioning was the best strategy to prevent morbidity and mortality.

We were not surprised to find a high rate of respiratory disorders other than MAS to occur among infants born through MSAF. Fleischer et al[21] and Yoder[14] similarly described non-MAS respiratory illnesses to be more common among infants born through MSAF compared with those delivered through clear amniotic fluid. Because we found risk factors for these other disorders to be virtually identical to those for MAS, we speculate that many of the illnesses were not distinctly different entities but were actually part of the overall spectrum of MAS. The range of roentgenographic findings among infants with MAS are diverse,[22,23] varying from consolidation or diffuse, patchy infiltrates to a hypovascular or even a virtually normal appearance. There is often no association between the degree of radiographic abnormalities and the severity of MAS.[22,23] We believe that when clinicians do not appreciate classic roentgenographic MAS features (ie, diffuse, patchy infiltrates) in sick neonates born through MSAF, they occasionally mistakenly attribute the respiratory distress to disorders other than MAS.

Lower 1-minute Apgar scores among INT infants likely represented the consequence of the intubation procedure itself. Several neonates assigned to EXP also had low 1-minute scores after having initially fulfilled the enrollment criteria for apparent vigor within 10 to 15 seconds of birth. Most of the latter infants had clinical symptoms that investigators believed necessitated intubation and suctioning. Meconium-stained infants delivered operatively were at greater risk for respiratory distress compared with those delivered vaginally. Infants of mothers with few prenatal visits were also at greater risk for respiratory disorders. The current work supports the important role of oropharyngeal suctioning before delivery of an infant’s shoulders in preventing MAS or other respiratory problems, a strategy first addressed by Carson and colleagues.[24] Oropharyngeal suctioning with a bulb syringe and a catheter attached to wall suction were equally effective. The presence of abnormal FHR monitoring indicated a greater risk for adverse pulmonary outcomes.

Use of amnioinfusion did not prevent MAS in infants born through MSAF. Although initial reports from the late 1980s and early 1990s indicated that amnioinfusion for thick-consistency MSAF would prevent MAS.[25] several recent reports have not found this therapy to be of benefit.[26] The current investigation confirms the direct relationship between MSAF consistency and occurrence of respiratory distress, as well as the level of respiratory support needed. The presence of oligohydramnios, as well as 1- or 5-minute Apgar scores of [is less than] 7, are similarly associated with an increased risk for subsequent respiratory distress. This is the first report of a greater propensity for MAS in male compared with female infants.

The current investigation was performed without informed consent being obtained from the infants’ parent(s). Our assumption that informed consent could not be obtained from [is greater than or equal to] 30% of eligible infants was confirmed by the recent work of Liu.[27] In an abstract, he described results from a trial assessing the need for intubation in 356 neonates born through thin-consistency meconium. Liu was only able to obtain informed consent from 47% of the parents of eligible infants. The goal of informing and obtaining consent from patients or their surrogates in research studies is of indisputable importance. However, this goal is often difficult to achieve in many situations, such as in an emergency department when a critically-ill patient first arrives or before the occurrence of an unexpected event like MSAF noted at the time of cesarean delivery. Under the usual rules of evidence in medicine, mandatory interventions should be those for which there is credible evidence that the benefits outweigh the risks. However, throughort medicine (including neonatology) unproven therapies are broadly prescribed in clinical practice without independent monitoring, without consent, and with little effort to inform the patients (or surrogates) of what is known and not known about the therapy.[28] The best attempts to assess the validity of certain therapies may be impossible under the usual rules for obtaining informed consent.[29] Ironically, some institutional review boards may not permit research without informed consent, yet in the same institution widespread clinical application of unproven therapies is practiced. Under such constraints, potentially answerable questions may never be answered. Suboptimal or even harmful therapies may be adopted and used widely.

CONCLUSION

We conclude that intratracheal suctioning of apparently vigorous meconium-stained infants does not result in a decreased incidence of respiratory distress compared with expectant management. The complication rate of intubation is relatively low and complications are minor and transient in nature. Until proven otherwise, endotracheal intubation and suctioning should still be performed in infants born through MSAF if they are not vigorous, if they need positive pressure ventilation, or if they develop symptoms of respiratory distress subsequent to initial assessment.

ACKNOWLEDGMENTS

This investigation was supported by grants from: the Steering Committee of the American Heart Association/American Academy of Pediatrics Neonatal Resuscitation Program; and the American Pediatric Society/Society for Pediatric Research Multicenter Trials Initiative.

We thank Dr Arnold Heyman (Neotech, Inc, Chatsworth, CA) who supplied the meconium aspirators for this investigation, Lynn Lynam, RN, PhD (Ohmeda, Inc, Columbia, MD) who provided vacuum regulators for several international sites to standardize negative wall-suction pressure, Drs Louis D. Pollack and Jon E. Tyson for their suggestions and encouragement, and the members of the obstetrical and neonatology services, as well as the delivery room staffs, at the participating hospitals. Without their cooperation and recognition of the need to study this important issue, this investigation could never have been accomplished. We also thank the following individuals: Nancy Vecchione; William Holt, RN; Adriana Aguilar, MD; Paul Foschiatti MD; Patricia Nemer, MD; Cynthia Villasis, MD; Raj Sharma, MD; Richard Rothchild, MD; Ramon Mir, MD; Fabiana Oliveira, MD; Sharon Hulman, RN; Chris Catts, RN; Giselle Yecco, RN; and Diane Rose, RN.

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Thomas E. Wiswell, MD(*); Catherine M. Gannon, MD(*); Jack Jacob, MD([double dagger]); Leonard Goldsmith, DO([sections]); Edgardo Szyld, MD([parallel]); Kerry Weiss, MD([paragraph]); David Schutzman, MD(#); Gerard M. Cleary, DO(*); Panayot Filipov, MD(**); Isabel Kurlat, MD([double dagger])([double dagger]); Carlos L. Caballero, MD([subsections]); Soraya Abassi, MD([parallel])([parallel]), Daniel Sprague, MD([paragraphs]); Charles Oltorf, MD(##); and Michael Padula, BA(*)

From the Neonatology services at (*) Thomas Jefferson University, Philadelphia, Pennsylvania; ([double dagger]) Providence Alaska Medical Center, Anchorage, Alaska; ([sections]) West Jersey Hospital, Voorhees, New Jersey; ([parallel]) Diego Paroissien Hospital, Buenos Aires, Argentina; ([paragraph]) Mercer Medical Center, Trenton, New Jersey; (#) Fitzgerald Mercy Hospital, Darby, Pennsylvania; (**) Flushing Hospital, Flushing, New York; ([double dagger])([double dagger]) University Hospital, Buenos Aires, Argentina; ([subsections]) Clinicas Hospital, Asuncion, Paraguay; ([parallel])([parallel])Pennsylvania Hospital, Philadelphia, Pennsylvania; ([paragraphs]) Desert Samaritan Medical Center, Phoenix, Arizona; and (##) Scott and White Memorial Hospital, Temple, Texas.

The results from this trial were presented in part at the Annual Meeting of the American Academy of Pediatrics; October 16, 1998; San Francisco, CA. A summary of that presentation was published in the October 1998 issue of the newsletter NRP Instructor Update.

Received for publication Feb 11, 1999; accepted Apr 26, 1999.

Reprint requests to (T.E.W.) Discovery Laboratories, Inc, 350 S Main St, Suite 307, Doylestown, PA 18901. E-mail: twiswell@discoverylabs.com

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