Combined obstetric and pediatric approach to prevent meconium aspiration syndrome BONITA
S.
CARSON,
ROSALIND
W.
WATSON
A.
MICHAEL D~nw,
M.D.
LOSEY,
BOWES, A.
R.N. JR.,
SIMMONS,
M.D. M.D.
Colorado
Routine intrapartum pharyngeal suctioning with a DeLee catheter of injknts ulith ~ne~oniu~n staining has signa$cantly redwed the incidence and severity of rn+coGun aspiration ,svndrome (MAS). There haue been no aduerse sequelae to this procedure, ujhich is cajried out u~hi.!e the injkt’s head is on the perineum, prior to the onset of respirationx Routine ,suctioning of the trachea under direct vision ajter delivers i.7 rarely necessary but should be done of meconium is visualized at the voral rorok Tracheobron&ial lavage with saline may add to the re.spiratoT morbidity. No deaths or severe cases of MAS have occurred since institution of he obstetric .suctioning procedure.
(AM. J. OBSTET. GYNECOL. 126: 712, 1976.)
M E c o N I u M aspiration syndrome (MAS) is a variety of aspiration pneumonia which occurs most frequently in term or post-term newborn infants who have passed meconium in utero. Affected infants often develop progressive respiratory failure with significant hypoxemia during the first 2 to 3 days of life. Death rates as high as 28 per cent have been reported for MAS.’ Despite improvements in ventilation therapy and more recent developments in respiratory management,’ therapy is often prolonged and ineffective once meconium aspiration is established. Therefore, prevention of the aspiration is potentially the most effective form of management of the syndrome. Several studies have demonstrated the value of immediate postdelivery suctioning of the trachea under
From the Division of P&natal Medicine, Departments Pediatk and Obstetrics-Gynecology, UniuersiQ of Colorado Medical Center.
direct laryngoscopic visualization in reducing the incidence of MAS.3-’ Bronchotracheal saline lavage after direct suctioning6 and the use of corticosteroids7 in the management of MAS have also been suggested. However, no technique which eliminates MAS has yet been reported. Animal evidence suggests that MAS syndrome does not occur until the initiation of air breathing.’ Therefore, complete removal of meconium prior to initiation of effective respirations might prevent the syndrome. Tracheal suctioning under direct laryngoscopic vision has been a standard part of our management of meconium staining. In May, 1974, intrapartum nasopharyngeal suctioning was added to our management. As soon as the baby’s head appears on the perineum, and prior to the delivery of the shoulders, the obstetrician passes a DeLee suction catheterthrough the nares to the level of the nasopharynx and aspirates any mucus or meconium. He then suctions the mouth and hypopharynx in a similar manner. The delivery is then completed routinely. In the case ot cesarean section, the procedure is the same: the infant is suctioned as soon as the head is delivered through the uterine incision, prior to delivery of the thorax, The purpose of this study was to compare the effectiveness in the prevention of MAS of this combined obstetric and pediatric suctioning approach with the previous approach of direct tracheal suctioning alone.
of
Supported in part by United St&es Public Health Sewice Grady HD-00781 and HD-00429. Michael A. Simmons is an Established investigator of the American Heart Association. Rpc&edJor Acwpted
publication Ju&
April
22, 1976.
14, 1976.
Reprint requests: Michael A. Simmons, M.D., Department of Pediatrics, C-218, Uniuer.$ of Colorada Medtial Center, 4200 E. Ninth Ave., Denver, Colorado 80.220.
712
Prevention of meconium aspiration syndrome
Methods The charts and computerized coding sheets of all infants born no earlier than 38 weeks of gestational age were reviewed to identify those infants who: (1) had meconium-stained amniotic fluid or skin; (2) had been coded as having a respiratory illness (pneumonia, aspiration, transient tachypnea, pneumothorax, or respiratory- distress syndrome); and (3) had died or had illness significant enough to require more than 4 days of hospitalization. A diagnosis of MAS was made on the basis of’ presence of meconium in the trachea, subsequent respiratory distress, and an abnormal chest x-ray consistent with Md4S.‘. I” All babies who died with clinical MAS had the diagnosis confirmed histologically. The ilhless was judged *‘mild” if oxygen therapy was given f&- 48 hours or less at an inspired oxygen concentration no greater than 40 per cent. Patients who required more than 40 per cent oxygen or oxygen therapy fi)r more than 48 hours but who did not require assisted ventilation were categorized as “moderately” ill. Those bahies who required assisted ventilation or who died were termed ‘Severe.” The patients were divided into three groups, according to the predominant management of meconium staining at the time of their deliveries: Group I. July, 1970. through April, 1974: deep suctioning hy obstetrician not done; suction under direct vision b:, pediatrician common but not invariable; tracheobronchial lavage not done. Group II. May, 1975, through March, 1975: deep suctioning by obstetrician usually done; direct tracheal suctioning follo\\.ed bv tracheobronchial lavage routine. Group III. April, 1975, to November, 1975 (prospective study): deep suctioning by obstetrician done consistently: suction under direct vision by pediatrician done, if indicated: lavage done on randomized basis. During the Group III phase, three of the authors attended deliveries \\ith the house staff to verify meconium at the level of’ the vocal cords. If meconium was present at the cords, the infant was promptly intubated and suctioned. If meconium was found below the cords at the time of intubation, the infant was lavaged on a ranclom basis, informecl consent having been obrained from the parents prior to delivery. Over the 6 month period, only two inf’ants in Group III qualified for intulyation according to the protocol.
Results As shown in Table I, during the first study period (Group I, from July, 1970, until the obstetric procedure was introduced in May, 1974) there were 947 cases of meconium staining among 7,585 term births
713
Table I. Comparison of the incidence and severity MAS among three groups of infants in u hich meconium staining was managed differently Group I
Group II
Term births 7,.%.? 2,320 947 (12.5%) 381 (ltj.4’$1 Meconium staining (per cent incidence) MAS, total cases 18 7 Mild Moderate Severe M.4S deaths
9 3 6 5*
4 c> i 0
of
Group III I.681 27:s (16.W) I I 0 0 0
*Twenty-eight per cent of MAS cases (0..52 per cent of all with mecnnium staining). (incidence of 12.5 per cent). Of the infants with meconium staining, 18 developed VAS (incidence of 1.9 per cent), resulting in five deaths (UAS mortality rate of 28 per cent). During the second time period (Group II), when the obstetric suctioning had been instituted and pediatric suctioning under direct vision was almost invariable, there rvere 2,320 term births with 381 cases of meconium staining (incidence of 16.4 pet cent). Seven of the 381 i&ants with meconium staining developed MAS (incidence of 1.8 per cent). but there were no deaths. Of the seven infants with MAS in Group Ii, only two were suctioned prior to deliver!, accorcling to our protocol because of precipitate delivery or omission by the obstetrician. Each of the infants who was suctioned developed only mild MAS. .I%e severe case of MAS during this time occurred in an mfant who was not suctioned prior to delivery and who was intubated and given positive-pressure assisted ventilation hefore the trachea was suctioned. Each of the seven infants with MAS in Group II received tracheohronchial lavage with normal saline. An additional five infants with meconium staining were identified who had no meconium in the trachea on direct visualization but who were nevertb&ss lavaged, with clear return. These five infants suhseclucntly required oxygen (25 to 35 per cent) for 24 to 48 hours. All had chest x-rays interpreted as consistent Gth iatrogenic wet lung.‘“~ ” Our clinical impression that the lavage procedure was increasing morbiditv led to the prospective study of infants Cth me(.onium staining from ,4pril. 1975, to November, 1975 (Ckroup III). During the 6 month period when the prospective protocol was in effect, among 2i3 infdnts with meconium staining, only two infants \vere identified who had meconium present at the cords and who thus qualified for intubation. Only one of these inf:mts devel-
Table II. Comparison of the three groups of infants with MAS with regard to hospital days, Apgar scores, and mode of delivery
No. of patients with MAS Mean hospital days of
18 9.7
7 8.3
8
9.2 0.5
4.4 3.9
3 5
4.7 6.6
5.1 6.6
5 9
6 1
1 0
I
survivors
Intensive care Low-risk
nursery
Mean Apgar scores At 1 min. At 5 min.
Mode of delivery Vaginal
Cesarean section
15 3
oped MAS (l/273 or 0.4 per cent), and his disease was milcl. During this 6 month period, iatrogenic wet lung disease secondary to lavage did not occur. With the use of both a binomial probability function md the Fisher exact test, the difference in incidence of MAS between Group I (no OB suction, no lavage) and Group III (OB suction, no lavage) was significant (P < 0.05). Group II was not included in this analysis due to the variable imposed by the introduction of layage and the probability that lavage itself was contributing to the respiratory morbidity. Stzatistical comparisons of retrospective data cannot establish cause-and-effect relationships. Such conclusions are particularly tenuous in areas of medicine undergoing rapid changes in techniques and approaches. Clearly, in our institution there has been a significant reduction in MAS incidence and severity associated with the introduction of intrapartum suctioning. A cause-and-effect relationship cannot be established definitively without a prospective, randomized clinical trial. In the 8 months since the completion of the study reported here, there have been no cases of MAS at our institution. Given the apparent risk-free benefit of this logical suctioning procedure, we do not feel that such a clinical trial would be justified. Table II compares hospital days, Apgar scores, and mode of delivery among the three study groups of MAS babies. There were no differences in hospital days or in 1 minute Apgar scores among the three groups. The differences between Groups I and II in intensive-care days is partially accounted for by the availability of more sophisticated nursing care in the low-risk unit beginning in July, 1973. The introduction of obstetric suctioning, and the secondary small delay before completion of delivery, did ‘not reduce the infants’ Apgar scores. Table II shows that the Apgar scores among MAS infants were the same before and after the introduction of intrapartum suctioning. In
Table III. Protocol for combined pediatric management
obstetric
and
as the baby’s head appears on the perineum, the obstetrician passes a DeLee suction catheter through the nares to the level of the nasopharynx and aspirates any mucus or meconium, then suctions the mouth and hypopharynx 2. Immediately after delivery the pediatrician suctions the oropharynx with a bulb and, if meconium is present, 1. As soon
inspects assistant
the cords monitors
by direct the heart
laryngoscopy while an rate 3. If meconium is present at the cords, direct suctioning the trachea with either a DeLee catheter or mouth-endotracheal tube is performed 4. Usual measures of ventilation and resuscitation are carried out
addition, the mean Apgar scores among Group III who did not develop respiratory were 7.4 at 1 minute and 8.9 at 5 minutes.
of
infants in morbidity
Comment Gooding and associates* demonstrated in newborn puppies that two conditions must exist before MAS can occur: (I) meconium must be present in the trachea and (2) the animal must breathe. Although gasping in utero has been shown to occur with hypoxic stress,‘* the net amount of meconium-stained amniotic fluid inhaled in utero is probably not great enough to produce MAS. Indeed, these investigators were unable to produce MAS in their model with intrauterine gasping of meconium-laden amniotic fluid.* Therefore, it is logical to remove meconium from the trachea befc>re the infant breathes. While immediate tracheal suctioning after delivery has been shown to reduce the morbidity and mortality rates from M.4S,“-’ the addition of tracheal suctioning prior to delivery of the thorax further reduces the chance that MAS might occur. Our results demonstrate that thorough suctioning in this manner is effective in preventing the aspiration of meconium into the infant’s trachea, since no effective gasping seems to occur even after delivery of the head onto the perineum. Indeed, in only two instances during our prospective study was meconium still present after the obstetric maneuver. This is in sharp contrast to the 56 per cent incidence ofmeconium in the trachea found by Gregory and associates’ in babies who breathed prior to suctioning. The presence of meconium at the cords has proved in our study to be a good guideline as to which infants should be intubated. Gregory and associate? reported a 10 per cent incidence of tracheal meconium in infants who had no supraglottic or pharyngeal meconium. We cannot state how many of our infants had tracheal meconium when the pharynx was clear, since we did
Volume Number
1%
Prevention
of meconium
aspiration
syndrome
715
6
Manipulation of an infant’s airway b\ ~1ccp suctioning. laryngoscopy, and intubation has of’tel> heen Ascouraged because of the fear of larvltxoq)a>m and reflex bradycardia. We have not been able LC>documcbnt any sequelae of either the obstetric such-ioning procedure or the pediatric management when 1n~q~erly performed. Gregory and associates ” like\& did not report any untoward sequelae of the trach&
S.
CARSON,
ROSALIND
W.
WATSON
A.
MICHAEL D~nw,
M.D.
LOSEY,
BOWES, A.
R.N. JR.,
SIMMONS,
M.D. M.D.
Colorado
Routine intrapartum pharyngeal suctioning with a DeLee catheter of injknts ulith ~ne~oniu~n staining has signa$cantly redwed the incidence and severity of rn+coGun aspiration ,svndrome (MAS). There haue been no aduerse sequelae to this procedure, ujhich is cajried out u~hi.!e the injkt’s head is on the perineum, prior to the onset of respirationx Routine ,suctioning of the trachea under direct vision ajter delivers i.7 rarely necessary but should be done of meconium is visualized at the voral rorok Tracheobron&ial lavage with saline may add to the re.spiratoT morbidity. No deaths or severe cases of MAS have occurred since institution of he obstetric .suctioning procedure.
(AM. J. OBSTET. GYNECOL. 126: 712, 1976.)
M E c o N I u M aspiration syndrome (MAS) is a variety of aspiration pneumonia which occurs most frequently in term or post-term newborn infants who have passed meconium in utero. Affected infants often develop progressive respiratory failure with significant hypoxemia during the first 2 to 3 days of life. Death rates as high as 28 per cent have been reported for MAS.’ Despite improvements in ventilation therapy and more recent developments in respiratory management,’ therapy is often prolonged and ineffective once meconium aspiration is established. Therefore, prevention of the aspiration is potentially the most effective form of management of the syndrome. Several studies have demonstrated the value of immediate postdelivery suctioning of the trachea under
From the Division of P&natal Medicine, Departments Pediatk and Obstetrics-Gynecology, UniuersiQ of Colorado Medical Center.
direct laryngoscopic visualization in reducing the incidence of MAS.3-’ Bronchotracheal saline lavage after direct suctioning6 and the use of corticosteroids7 in the management of MAS have also been suggested. However, no technique which eliminates MAS has yet been reported. Animal evidence suggests that MAS syndrome does not occur until the initiation of air breathing.’ Therefore, complete removal of meconium prior to initiation of effective respirations might prevent the syndrome. Tracheal suctioning under direct laryngoscopic vision has been a standard part of our management of meconium staining. In May, 1974, intrapartum nasopharyngeal suctioning was added to our management. As soon as the baby’s head appears on the perineum, and prior to the delivery of the shoulders, the obstetrician passes a DeLee suction catheterthrough the nares to the level of the nasopharynx and aspirates any mucus or meconium. He then suctions the mouth and hypopharynx in a similar manner. The delivery is then completed routinely. In the case ot cesarean section, the procedure is the same: the infant is suctioned as soon as the head is delivered through the uterine incision, prior to delivery of the thorax, The purpose of this study was to compare the effectiveness in the prevention of MAS of this combined obstetric and pediatric suctioning approach with the previous approach of direct tracheal suctioning alone.
of
Supported in part by United St&es Public Health Sewice Grady HD-00781 and HD-00429. Michael A. Simmons is an Established investigator of the American Heart Association. Rpc&edJor Acwpted
publication Ju&
April
22, 1976.
14, 1976.
Reprint requests: Michael A. Simmons, M.D., Department of Pediatrics, C-218, Uniuer.$ of Colorada Medtial Center, 4200 E. Ninth Ave., Denver, Colorado 80.220.
712
Prevention of meconium aspiration syndrome
Methods The charts and computerized coding sheets of all infants born no earlier than 38 weeks of gestational age were reviewed to identify those infants who: (1) had meconium-stained amniotic fluid or skin; (2) had been coded as having a respiratory illness (pneumonia, aspiration, transient tachypnea, pneumothorax, or respiratory- distress syndrome); and (3) had died or had illness significant enough to require more than 4 days of hospitalization. A diagnosis of MAS was made on the basis of’ presence of meconium in the trachea, subsequent respiratory distress, and an abnormal chest x-ray consistent with Md4S.‘. I” All babies who died with clinical MAS had the diagnosis confirmed histologically. The ilhless was judged *‘mild” if oxygen therapy was given f&- 48 hours or less at an inspired oxygen concentration no greater than 40 per cent. Patients who required more than 40 per cent oxygen or oxygen therapy fi)r more than 48 hours but who did not require assisted ventilation were categorized as “moderately” ill. Those bahies who required assisted ventilation or who died were termed ‘Severe.” The patients were divided into three groups, according to the predominant management of meconium staining at the time of their deliveries: Group I. July, 1970. through April, 1974: deep suctioning hy obstetrician not done; suction under direct vision b:, pediatrician common but not invariable; tracheobronchial lavage not done. Group II. May, 1975, through March, 1975: deep suctioning by obstetrician usually done; direct tracheal suctioning follo\\.ed bv tracheobronchial lavage routine. Group III. April, 1975, to November, 1975 (prospective study): deep suctioning by obstetrician done consistently: suction under direct vision by pediatrician done, if indicated: lavage done on randomized basis. During the Group III phase, three of the authors attended deliveries \\ith the house staff to verify meconium at the level of’ the vocal cords. If meconium was present at the cords, the infant was promptly intubated and suctioned. If meconium was found below the cords at the time of intubation, the infant was lavaged on a ranclom basis, informecl consent having been obrained from the parents prior to delivery. Over the 6 month period, only two inf’ants in Group III qualified for intulyation according to the protocol.
Results As shown in Table I, during the first study period (Group I, from July, 1970, until the obstetric procedure was introduced in May, 1974) there were 947 cases of meconium staining among 7,585 term births
713
Table I. Comparison of the incidence and severity MAS among three groups of infants in u hich meconium staining was managed differently Group I
Group II
Term births 7,.%.? 2,320 947 (12.5%) 381 (ltj.4’$1 Meconium staining (per cent incidence) MAS, total cases 18 7 Mild Moderate Severe M.4S deaths
9 3 6 5*
4 c> i 0
of
Group III I.681 27:s (16.W) I I 0 0 0
*Twenty-eight per cent of MAS cases (0..52 per cent of all with mecnnium staining). (incidence of 12.5 per cent). Of the infants with meconium staining, 18 developed VAS (incidence of 1.9 per cent), resulting in five deaths (UAS mortality rate of 28 per cent). During the second time period (Group II), when the obstetric suctioning had been instituted and pediatric suctioning under direct vision was almost invariable, there rvere 2,320 term births with 381 cases of meconium staining (incidence of 16.4 pet cent). Seven of the 381 i&ants with meconium staining developed MAS (incidence of 1.8 per cent). but there were no deaths. Of the seven infants with MAS in Group Ii, only two were suctioned prior to deliver!, accorcling to our protocol because of precipitate delivery or omission by the obstetrician. Each of the infants who was suctioned developed only mild MAS. .I%e severe case of MAS during this time occurred in an mfant who was not suctioned prior to delivery and who was intubated and given positive-pressure assisted ventilation hefore the trachea was suctioned. Each of the seven infants with MAS in Group II received tracheohronchial lavage with normal saline. An additional five infants with meconium staining were identified who had no meconium in the trachea on direct visualization but who were nevertb&ss lavaged, with clear return. These five infants suhseclucntly required oxygen (25 to 35 per cent) for 24 to 48 hours. All had chest x-rays interpreted as consistent Gth iatrogenic wet lung.‘“~ ” Our clinical impression that the lavage procedure was increasing morbiditv led to the prospective study of infants Cth me(.onium staining from ,4pril. 1975, to November, 1975 (Ckroup III). During the 6 month period when the prospective protocol was in effect, among 2i3 infdnts with meconium staining, only two infants \vere identified who had meconium present at the cords and who thus qualified for intubation. Only one of these inf:mts devel-
Table II. Comparison of the three groups of infants with MAS with regard to hospital days, Apgar scores, and mode of delivery
No. of patients with MAS Mean hospital days of
18 9.7
7 8.3
8
9.2 0.5
4.4 3.9
3 5
4.7 6.6
5.1 6.6
5 9
6 1
1 0
I
survivors
Intensive care Low-risk
nursery
Mean Apgar scores At 1 min. At 5 min.
Mode of delivery Vaginal
Cesarean section
15 3
oped MAS (l/273 or 0.4 per cent), and his disease was milcl. During this 6 month period, iatrogenic wet lung disease secondary to lavage did not occur. With the use of both a binomial probability function md the Fisher exact test, the difference in incidence of MAS between Group I (no OB suction, no lavage) and Group III (OB suction, no lavage) was significant (P < 0.05). Group II was not included in this analysis due to the variable imposed by the introduction of layage and the probability that lavage itself was contributing to the respiratory morbidity. Stzatistical comparisons of retrospective data cannot establish cause-and-effect relationships. Such conclusions are particularly tenuous in areas of medicine undergoing rapid changes in techniques and approaches. Clearly, in our institution there has been a significant reduction in MAS incidence and severity associated with the introduction of intrapartum suctioning. A cause-and-effect relationship cannot be established definitively without a prospective, randomized clinical trial. In the 8 months since the completion of the study reported here, there have been no cases of MAS at our institution. Given the apparent risk-free benefit of this logical suctioning procedure, we do not feel that such a clinical trial would be justified. Table II compares hospital days, Apgar scores, and mode of delivery among the three study groups of MAS babies. There were no differences in hospital days or in 1 minute Apgar scores among the three groups. The differences between Groups I and II in intensive-care days is partially accounted for by the availability of more sophisticated nursing care in the low-risk unit beginning in July, 1973. The introduction of obstetric suctioning, and the secondary small delay before completion of delivery, did ‘not reduce the infants’ Apgar scores. Table II shows that the Apgar scores among MAS infants were the same before and after the introduction of intrapartum suctioning. In
Table III. Protocol for combined pediatric management
obstetric
and
as the baby’s head appears on the perineum, the obstetrician passes a DeLee suction catheter through the nares to the level of the nasopharynx and aspirates any mucus or meconium, then suctions the mouth and hypopharynx 2. Immediately after delivery the pediatrician suctions the oropharynx with a bulb and, if meconium is present, 1. As soon
inspects assistant
the cords monitors
by direct the heart
laryngoscopy while an rate 3. If meconium is present at the cords, direct suctioning the trachea with either a DeLee catheter or mouth-endotracheal tube is performed 4. Usual measures of ventilation and resuscitation are carried out
addition, the mean Apgar scores among Group III who did not develop respiratory were 7.4 at 1 minute and 8.9 at 5 minutes.
of
infants in morbidity
Comment Gooding and associates* demonstrated in newborn puppies that two conditions must exist before MAS can occur: (I) meconium must be present in the trachea and (2) the animal must breathe. Although gasping in utero has been shown to occur with hypoxic stress,‘* the net amount of meconium-stained amniotic fluid inhaled in utero is probably not great enough to produce MAS. Indeed, these investigators were unable to produce MAS in their model with intrauterine gasping of meconium-laden amniotic fluid.* Therefore, it is logical to remove meconium from the trachea befc>re the infant breathes. While immediate tracheal suctioning after delivery has been shown to reduce the morbidity and mortality rates from M.4S,“-’ the addition of tracheal suctioning prior to delivery of the thorax further reduces the chance that MAS might occur. Our results demonstrate that thorough suctioning in this manner is effective in preventing the aspiration of meconium into the infant’s trachea, since no effective gasping seems to occur even after delivery of the head onto the perineum. Indeed, in only two instances during our prospective study was meconium still present after the obstetric maneuver. This is in sharp contrast to the 56 per cent incidence ofmeconium in the trachea found by Gregory and associates’ in babies who breathed prior to suctioning. The presence of meconium at the cords has proved in our study to be a good guideline as to which infants should be intubated. Gregory and associate? reported a 10 per cent incidence of tracheal meconium in infants who had no supraglottic or pharyngeal meconium. We cannot state how many of our infants had tracheal meconium when the pharynx was clear, since we did
Volume Number
1%
Prevention
of meconium
aspiration
syndrome
715
6
Manipulation of an infant’s airway b\ ~1ccp suctioning. laryngoscopy, and intubation has of’tel> heen Ascouraged because of the fear of larvltxoq)a>m and reflex bradycardia. We have not been able LC>documcbnt any sequelae of either the obstetric such-ioning procedure or the pediatric management when 1n~q~erly performed. Gregory and associates ” like\& did not report any untoward sequelae of the trach&
