Glycyrrhizic acid alleviates the meconium-induced acute lung injury in neonatal rats by inhibiting oxidative stress through mediating the Keap1/Nrf2/HO-1 signal pathway.

Meconium aspiration syndrome (MAS) is a disease closely related to inflammation and oxidative stress. Glycyrrhizic acid (GA) is a triterpenoid isolated from licorice with multiple bioprotective properties. In the present study, impacts of GA against MAS rats, as well as the potential mechanism, will be investigated. MAS model was established on newborn rats, followed by the treatment of 12.5, 25, and 50 mg/kg GA. The wet/dry weight ratio of lung tissues was calculated. The production of IL-6, IL-1ß, TNF-α, malonaldehyde (MDA), superoxide dismutase (SOD), glutathione (GSH) was measured using ELISA assay. HE staining was used to evaluate the pathological state of lung tissues and TUNEL assay was used to detect the apoptotic state. The protein expression of Nrf2, Keap1, HO-1, Bcl-2, Bax, and cleaved-Caspase3 was measured by Western blotting assay. The elevated W/D ratio, release of inflammatory factors, lung injury score, and apoptotic index, as well as the activated oxidative stress and suppressed Keap1/Nrf2/HO-1 pathway, in MAS rats were significantly alleviated by GA. After introducing the inhibitor of Nrf2, ML385, the protective property of GA on the pathological state, apoptotic index, and oxidative stress in MAS rats was pronouncedly abolished. Taken together, glycyrrhizin alleviated GAH in rats by suppressing Keap1/Nrf2/HO-1 signaling mediated oxidative stress.

Placental histology of acute versus continuous meconium exposure - Association with obstetric and neonatal outcomes.

OBJECTIVE: We aimed to compare obstetric and neonatal outcomes of deliveries complicated by meconium stained amniotic fluid (MSAF), according to placental histology of continuous vs. acute meconium associated changes. METHODS: This was a retrospective cohort study of singleton deliveries complicated by MSAF at a single university-affiliated medical center during 2008-2018. Obstetric and neonatal outcomes were compared between cases with placental acute vs. continuous meconium exposure associated changes (columnar epithelial changes and meconium-laden macrophages, respectively). Regression analysis was used to identify independent associations with adverse neonatal outcomes. RESULTS: The medical records of 294 deliveries at our institution were reviewed, along with medical records of the neonates and the histopathological reports of their placentas. Ninety-two cases were classified as an acute placental reaction to meconium (acute exposure group) and 200 as continuous placental exposure (continuous exposure group). Patient demographics did not differ between groups. Placentas from the continuous exposure to meconium were associated with a higher rate of placental weight <10th percentile (p = 0.03) while the acute exposure group was associated with a shorter time between rupture of membranes and delivery (p = 0.02). and higher rates of non-reassuring fetal heart rate in labor (p = 0.003), and of adverse neonatal outcome (p = 0.02). In multivariable analysis adverse neonatal outcome was associated with acute histologic exposure to meconium independent of background confounders (aOR = 1.51, 95% CI 1.12-3.67). CONCLUSIONS: Acute histological changes of MSAF were independently associated with adverse neonatal outcomes as compared to continuous histologic MSAF.

Preventive Effects of Probiotic Supplementation on Neonatal Hyperbilirubinemia Caused by Isoimmunization.

OBJECTIVE: Probiotic supplementation can help to improve recovery from jaundice by reducing enterohepatic circulation through the regulation of intestinal microbial flora. The aim of our study was to investigate the effect of probiotic supplementation on neonatal hyperbilirubinemia caused by isoimmunization alone. STUDY DESIGN: Sixty neonates were randomly divided into a placebo group and a probiotic group (Lactobacillus rhamnosus GG). Serum total bilirubin (STB) levels were measured at birth and at 4, 8, 16, 24, and 36 hours of treatment (and at 48, 60, and 72 hours if necessary). Duration of phototherapy, rephototherapy requirements, and daily meconium evacuation were recorded. RESULTS: STB and rebound STB levels at 36 hours were lower in the probiotic group than in the placebo group (p = 0.01 and p = 0.006, respectively). Meconium evacuation was more frequent in the probiotic group than in the placebo group on the second and third days of life (p = 0.002 and 0.009, respectively). CONCLUSION: Probiotics do not affect STB levels in the first 24 hours of life or duration of phototherapy in neonates with jaundice caused by blood group incompatibility. The effect of probiotic supplementation by reducing enterohepatic circulation occurs at 36 hours of life in newborns with isoimmunization.

Evaluation of Impact of Perinatal Factors on Time to First Meconium Passage in Nigerian Neonates.

Background: Delayed meconium passage is usually a signal to congenital distal bowel dysfunction. Timing of meconium passage may vary depending on race, sex and several perinatal factors. Understanding the timing and associated perinatal factors in any given population will help in prompt diagnosis and adequate management of cases in that population. Objectives: To determine the timing of first meconium passage amongst Nigerian neonates, and evaluate the impact of various associated perinatal factors. Materials and Methods: A cross-sectional study using interviewer-administered questionnaires to obtain data from mothers of apparently normal infants attending the postnatal clinic of the University of Nigeria Teaching Hospital, Enugu, Nigeria. Data acquisition and analysis were done using SPSS version 20. A P-value of < 0.05 was adjudged statistically significant. Results: There were 276 male and 277 female infants. Mean birth weight was 3.4kg and mean gestational age at delivery 38.8weeks. The median age at presentation was 42days. Preterm deliveries were in 6.3%(32/510) and 3.7%(20/536) weighed less than 2.5kg at birth. Sixty-five percent (339/519) had spontaneous vertex delivery and 35%(180/519) had caesarean delivery. Passage of first meconium was within 24hours in 56.6%(307/543) and in 48hours 91.3%(496/543) had passed meconium. Fifty-four percent (54%, 288/537) commenced breastfeeding within 24hours and 85% (n=456/537) within 48hours. Exclusive breastfeeding was done in 61.5%(326/533) of subjects. Timing of first meconium passage was significantly affected by gestational age at delivery (p<0.001), mode of delivery (p<0.01), birth weight (p=0.02), first minute APGAR score (p<0.001), timing of commencement of breastfeeding (p<0.001) and feeding before breastfeeding is commenced (p = 0.02). Conclusion: Compared to other studies, we found smaller proportion of neonates passing meconium in the first 24 hours. Term neonates, birth weight ≥ 2.5kg, spontaneous vertex delivery, high Apgar score, commencement of breastfeeding within 24 hours of birth, feeding before breastfeeding is commenced, are perinatal factors associated with earlier first meconium passage.

Should we look for Hirschsprung disease in all children with meconium plug syndrome?

BACKGROUND: Meconium plug syndrome (MPS) is associated with Hirschsprung disease (HD) in 13-38% of cases. This study sought to assess institutional variation in utilization of rectal biopsy in children with MPS and the likelihood of diagnosing HD in this population. METHODS: Patients with MPS on contrast enema in the first 30 days of life from the Pediatric Health Information System database in 2016-2017 were included. Institutional rates of rectal biopsies performed during the initial admission were calculated and then used to predict institutional rates of early HD diagnoses using Poisson regression. RESULTS: Of 373 newborns with MPS, 106 (28.4%) underwent early rectal biopsy, of whom 43 (40.5%) had HD. Fifty-seven (15.3%) were ultimately diagnosed with HD. Eight (14%) of these patients had a delayed diagnosis. HD rates between institutions did not differ significantly (range 0-50%, p=0.52), but usage of early rectal biopsy did (range 0-80%, p=0.03). Each additional early biopsy increased the early HD diagnosis rate by 35% (ß=0.30, 95% CI 0.15-0.45, p<0.0001). CONCLUSION: The incidence of HD is increased in children with MPS. There is significant hospital variability in the utilization of early rectal biopsy, and opportunity exists to standardize practice. TYPE OF STUDY: Study of Diagnostic test Level of Evidence: Level III.

The relation of fetal colon and rectum diameters with labor in healthy late-third trimester pregnancies.

OBJECTIVE: To investigate the associations of fetal colon-rectum diameters with labor and fetal distress or meconium passage in healthy pregnancies in the late 3rd trimester. STUDY DESIGN: A total of 162 healthy, singleton pregnant women at ≥360/7 weeks who were in the latent-phase of labor (n = 69) or those not in labor (n = 93, controls) at the time of ultrasound examination were enrolled. Fetal colon (ascending, transverse, descending, sigmoid) and rectum diameters, Doppler indices of materno-fetal vessels were measured. Data were analyzed according to the mode of delivery. RESULTS: Fetal colon-rectum diameters were smaller in women in labor compared to controls (p = 0.001). Positive correlations were observed between fetal colon-rectum diameters and interval between ultrasound and labor onset in the control group except for those who had scheduled cesarean sections (C/S) (p = 0.001). Similar colon-rectum measurements were obtained in fetuses delivered via cesarean section due to fetal distress or to other indications (p > 0.05). In women who had uterine contractions during ultrasound examination; later delivered by vaginal route, no association was observed between Apgar scores and colon-rectum diameters during latent-phase (p > 0.05), and also there were significant positive correlations between different segments of colon-rectum diameters and duration of neonatal meconium passage (p < 0.05). CONCLUSION: Fetal colon and rectum diameters are smaller during labor and the measurements tend to diminish as the labor approaches, but do not indicate fetal distress.

Umbilical Cord Blood pH in Intrapartum Hypoxia.

OBJECTIVE: To determine the association of cord arterial blood pH with neonatal outcome in cases of intrapartum fetal hypoxia. STUDY DESIGN: Descriptive analytical study. PLACE AND DURATION OF STUDY: Gynaecology Unit-II, Civil Hospital, Karachi, from September 2011 to November 2012. METHODOLOGY: All singleton cephalic fetuses at term gestation were included in the study. Those with any anomaly, malpresentation, medical disorders, maternal age < 18 years, multiple gestation and ruptured membranes were excluded. Patients with abnormal cardiotocography and/or meconium stained liquor were enrolled as index case and immediate next delivery with no such signs as a control. Demographic characteristics, pH level < or > 7.25, neonatal outcome measures (healthy, NICU admission or neonatal death), color of liquor and mode of delivery recorded on predesigned proforma. Statistical analysis performed by SPSS 16 by using independent-t test or chi-square test and ANOVA test as needed. RESULTS: A total of 204 newborns were evaluated. The mean pH level was found to be significantly different (p=0.007) in two groups. The pH value 7.25 had significant association (p < 0.001) with the neonatal outcome. However, the association of neonatal outcome with severity of acidemia was not found to be significant. Grading of Meconium Stained Liquor (MSL) also did not relate positively with pH levels as 85.7% of grade I, 68.9% of grade II and 59.4% of grade III MSLhad pH > 7.25. Majority (63.6%) cases needed caesarean section as compared to 31.4% controls. CONCLUSION: There is a significant association of cord arterial blood pH at birth with neonatal outcome at pH < or > 7.25; but below the level of pH 7.25 it is still inconclusive.

Does visceral osteopathic treatment accelerate meconium passage in very low birth weight infants?- A prospective randomized controlled trial.

BACKGROUND: To determine whether the complementary approach of visceral manipulative osteopathic treatment accelerates complete meconium excretion and improves feeding tolerance in very low birth weight infants. METHODS: This study was a prospective, randomized, controlled trial in premature infants with a birth weight <1500 g and a gestational age <32 weeks who received a visceral osteopathic treatment 3 times during their first week of life or no treatment. RESULTS: Passage of the last meconium occurred after a median of 7.5 days (95% confidence interval: 6-9 days, n = 21) in the intervention group and after 6 days (95% confidence interval: 5-9 days, n = 20,) in the control group (p = 0.11). However, osteopathic treatment was associated with a 8 day longer time to full enteral feedings (p = 0.02), and a 34 day longer hospital stay (Median = 66 vs. 100 days i.e.; p=0.14). Osteopathic treatment was tolerated well and no adverse events were observed. CONCLUSIONS: Visceral osteopathic treatment of the abdomen did not accelerate meconium excretion in VLBW (very low birth weight)-infants. However infants in the osteopathic group had a longer time to full enteral feedings and a longer hospital stay, which could represent adverse effects. Based on our trial results, we cannot recommend visceral osteopathic techniques in VLBW-infants. TRIAL REGISTRATION: Clinical trials.gov: NCT02140710.

Newborn meconium and urinary metabolome response to maternal gestational diabetes mellitus: a preliminary case-control study.

Recently, the number of women suffering from gestational diabetes mellitus (GDM) has risen dramatically. GDM attracts increasing attention due to its potential harm to the heath of both the fetus and the mother. We designed this case-control study to investigate the metabolome response of newborn meconium and urine to maternal GDM. GDM mothers (n = 142) and healthy controls (n = 197) were recruited during June-July 2012 in Xiamen, China. The newborns' metabolic profiles were acquired using liquid chromatography coupled to mass spectrometry. The data showed that meconium and urine metabolome patterns clearly discriminated GDM cases from controls. Fourteen meconium metabolic biomarkers and three urinary metabolic biomarkers were tentatively identified for GDM. Altered levels of various endogenous biomarkers revealed that GDM may induce disruptions in lipid metabolism, amino acid metabolism, and purine metabolism. An unbalanced lipid pattern is suspected to be a GDM-specific feature. Furthermore, the relationships between the potential biomarkers and GDM risk were evaluated by binary logistic regression and receiver operating characteristic analysis. A combined model of nine meconium biomarkers showed a great potential in diagnosing GDM-induced disorders.

Effect of Meconium on the Contractility of the Superior Mesenteric Artery: A Clue to Intestinal Damage in Gastroschisis.

INTRODUCTION: Intestinal damage has been shown to occur when intra-amniotic meconium concentration exceeds threshold level. However, the mechanism of the meconium-induced intestinal damage is still unclear. Intestinal ischemia can cause intestinal damage in gastroschisis. This study was aimed to determine the effects of intra-amniotic meconium on the contractility of superior mesenteric artery (SMA). MATERIALS AND METHODS: Eighteen-day-old fertilized chick embryos (Gallus Domesticus) were extirpated and intestines were harvested. The SMA specimens were prepared as 4 mm segments in the organ bath with Krebs-Henseleit buffer. The isometric contraction responses of the SMA specimens were evaluated with norepinephrine, different meconium concentrations, and clear amniotic fluid. Maximum isometric contractions responses (MICR) of the SMA specimens were recorded with an amplifier system on a computer. RESULTS: In the norepinephrine group, MICR was found as 2.92 ± 0.57 mN. While MICR of the 1/100 meconium group (highest meconium concentration) was found as 1.56 ± 0.40 mN, MICR of the clear amniotic fluid group was 0.41 ± 0.07 mN. The MICR of the norepinephrine group was significantly increased compared with the 1/100 meconium and clear amniotic fluid groups. MICR of the 1/100 meconium group was also found to be significantly increased compared with clear amniotic fluid group. No statistically significant difference was found among the meconium subgroups. CONCLUSION: Intra-amniotic meconium in fetuses with gastroschisis might cause ischemic intestinal damage by reducing the intestinal blood flow. Further studies are needed to show the outcomes of the vasoactive effect of meconium on the SMA blood flow.

Accuracy of the lamellar body count in amniotic fluid contaminated by meconium.

OBJECTIVE: To determine whether meconium-contaminated amniotic fluid falsely elevates the lamellar body count in fetal lung maturity testing. METHODS: Thirty mothers undergoing amniocentesis for fetal lung maturity testing were prospectively consented. A 2 mL portion of the patient's sample was mixed with a 10% meconium solution and the meconium-stained sample was then run in tandem with the patient's sample used in clinical management. Pure meconium samples without amniotic fluid were also run through the cell counter for analysis. RESULTS: Following meconium contamination, the lamellar body count value increased in 67% of the cases, decreased in 23% and remained the same in 10%. There were 13 test results that had "immature" values in the uncontaminated patient management sample group and nine of these (69%) became elevated to a "mature" level (a false elevation) following the addition of meconium. All of the 10 pure liquid meconium samples devoid of amniotic fluid processed by the cell counter identified and quantified some particle the size of platelets. CONCLUSIONS: The lamellar body count test result is not reliable in meconium-stained amniotic fluid specimens. There is some unknown particle found in meconium that is the size of platelets/lamellar bodies that can falsely elevate the test result. Currently, the only reliable fetal lung maturity test in meconium-stained amniotic fluid is the presence of phosphatidylglycerol.

The passage of meconium alone is not a sign of correctly positioned anus.

OBJECTIVE: The aim of this study is to determine the consequences of delayed presentation of anorectal malformations and emphasize the causes of delayed diagnosis of these malformations. METHODS: We retrospectively reviewed 54 neonatal patients with a diagnosis of anorectal malformations. Group 1 consisted of 35 patients diagnosed within the first 48 h of life and Group 2 included 19 patients diagnosed after 48 h of life. RESULTS: Obstructive symptoms at the time of diagnosis, overall complications and the mean postoperative hospitalization period in Group 2 were markedly higher than that of Group 1. A comprehensive neonatal examination within the first 48 h of life was performed in 32 (91.4%) patients in Group 1 and 5 (26.3%) of the patients in Group 2 (p < 0.001). CONCLUSIONS: The passage of meconium is not the only sign of correctly positioned anus. A careful physical examination and awareness of this anomaly are of great importance in making a timely diagnosis of anorectal malformations.

The aetiology of meconium-stained amniotic fluid: pathologic hypoxia or physiologic foetal ripening? (Review).

INTRODUCTION: Despite the many efforts to study the (patho)physiology of meconium release before delivery, it still remains an indistinct subject. Some studies have reported a relationship between hypoxia and MSAF, whilst others have not. The most common association found however, is between MSAF and the term of gestation. METHODS: MEDLINE, EMBASE and the Cochrane library were electronically searched. Papers about the (patho)physiology of meconium-stained amniotic fluid in English were included. Papers about management strategies were excluded (see elsewhere this issue). RESULTS: Different theories have been proposed including acute or chronic hypoxia, physiologic foetal ripening and peripartum infection. CONCLUSION: We suggest that meconium-stained amniotic fluid should be regarded as a symptom rather than a syndrome becoming more prevalent with increasing term and which might be associated with higher levels of infection or asphyxia.

Reasons for exclusion of 6820 umbilical cord blood donations in a public cord blood bank.

BACKGROUND: To provide information for umbilical cord blood (UCB) banks to adopt optimal collection strategies and to make UCB banks operate efficiently, we investigated the reasons for exclusion of UCB units in a 3-year recruitment period. STUDY DESIGN AND METHODS: We analyzed records of the reasons for exclusion of the potential UCB donation from 2004 to 2006 in the Tzu-Chi Cord Blood Bank and compared the results over 3 years. We grouped these reasons for exclusion into five phases, before collection, during delivery, before processing, during processing, and after freezing according to the time sequence and analyzed the reasons at each phase. RESULTS: Between 2004 and 2006, there were 10,685 deliveries with the intention of UCB donation. In total, 41.2% of the UCB units were considered eligible for transplantation. The exclusion rates were 93.1, 48.4, and 54.1% in 2004, 2005, and 2006, respectively. We excluded 612 donations from women before their child birth, 133 UCB units during delivery, 80 units before processing, 5010 units during processing, and 421 units after freezing. There were 24 UCB units with unknown reasons of ineligibility. Low UCB weight and low cell count were the first two leading causes of exclusion (48.6 and 30.9%). The prevalence of artificial errors, holiday or transportation problem, low weight, and infant problems decreased year after year. CONCLUSION: The exclusion rate was high at the beginning of our study as in previous studies. Understanding the reasons for UCB exclusion may help to improve the efficiency of UCB banking programs in the future.

Clinical parameters, intestinal function, and IGF1 concentrations in colostrum-deprived and colostrum-fed newborn pony foals.

Colostrum (COL) contains cytokines and growth factors that may enhance intestinal development in neonates. The hypothesis of this study was that besides providing immunoglobulins, COL is important for intestinal function and meconium release in foals. Newborn foals were either fed COL (n = 5) or an equal amount of milk replacer (MR, n = 7) during the first 24 hours of life. To ensure passive immunity, all foals received 1 L plasma. Postnatal development, meconium release, intestinal motility, white blood cell count, insulin-like growth factor 1, and intestinal absorptive function (xylose absorption test) were evaluated. Clinical findings and meconium release were not affected by feeding of COL or MR. Ultrasonography revealed a slightly larger jejunum and stomach in group COL versus MR (P < 0.05). The percentage of polymorphonuclear leucocytes was higher in foals of group MR versus group COL (P < 0.05) and the percentage of lymphocytes was lower in MR compared with COL foals (P < 0.05). Plasma insulin-like growth factor 1 concentration increased during the first 14 days after birth in both groups. A xylose absorption test on Day 5 revealed similar increases in plasma xylose concentrations after oral intake. In conclusion, feeding of COL versus MR was without effect on meconium release and intestinal absorptive function. Differences between foals fed COL and MR with regard to intestinal function are apparently without clinical relevance. In foals that have not received maternal COL, there is no major risk of intestinal problems if they are fed MR and provided with immunoglobulins by transfusion of plasma.

The influence of genetics on cystic fibrosis phenotypes.

Technological advances in genetics have made feasible and affordable large studies to identify genetic variants that cause or modify a trait. Genetic studies have been carried out to assess variants in candidate genes, as well as polymorphisms throughout the genome, for their associations with heritable clinical outcomes of cystic fibrosis (CF), such as lung disease, meconium ileus, and CF-related diabetes. The candidate gene approach has identified some predicted relationships, while genome-wide surveys have identified several genes that would not have been obvious disease-modifying candidates, such as a methionine sulfoxide transferase gene that influences intestinal obstruction, or a region on chromosome 11 proximate to genes encoding a transcription factor and an apoptosis controller that associates with lung function. These unforeseen associations thus provide novel insight into disease pathophysiology, as well as suggesting new therapeutic strategies for CF.

Bowel habit in preterm newborns: effect of new formulas.

Preterm infants may pass meconium only after the first 48 hours of life, even in absence of any gastrointestinal disease. The role of various factors in determining the time of meconium elimination has been recently assessed. Gestational age and start of feeding had been demonstrated to influence first meconium timing. The aim of our study was to evaluate time of first meconium passage and the time to achieve regular bowel movements (RBM), correlating these two events to different factors such as gestational age (GA), sex, type of delivery [caesarean section (CS) vs spontaneous delivery (SD)], 1' and 5' Apgar score (1'AS, 5'AS), time and type of feeding, oxygen requirement and any mode of respiratory support.

Neonatal outcome in meconium stained amniotic fluid-one year experience.

OBJECTIVES: To determine the effect of clear liquor and meconium stained liquor on mode of delivery, and to evaluate neonatal outcome. METHODS: It was a Cross sectional analytical study, conducted in the department of Obstetrics and Gynaecology, Shaikh Zyed Federal Postgraduate Medical Institute/Hospital, Lahore and Shaikh Zaid Women Hospital Larkana, from April 2006 to March 2007. Two hundred and fifty patients from Larkana and 250 patients from Lahore in clear liquor group were included in the study. Similarly 125 patients from each city, that is 250 patients which had meconium stained liquor were included in group 2. The subjects with meconium stained amniotic fluid and clear amniotic fluid were registered as group 1 and 2. The socio demographic information, fertility history and gestational age of subjects were recorded. The investigations and information regarding mode of delivery and duration of labour were also noted. All babies delivered were attended by paediatricians. RESULTS: In this study 500 cases with clear liquor and 250 cases of meconium stained liquor were selected from two cities, Lahore and Larkana. Out of these 55 (22%) patients had grade I meconium stained liquor, 140 (56%) patients and 55 (22%) patients had grade II and grade III meconium stained liquor respectively. The mode of delivery is significantly affected by meconium staining of liquor. The effect of meconium stained liquor was significant on time of delivery. There were 40 (16%) post date deliveries in meconium stained liquor as compared to 1% in subjects with clear liquor. The effect of meconium staining of liquor was significant on Apgar score, neonatal admission, meconium aspiration syndrome and neonatal deaths. CONCLUSION: Meconium stained amniotic fluid (MSAF), is associated with increased neonatal morbidity and mortality. Caesarean sections were performed twice as frequently in women presenting with MSAF.

Role of meconium in the reaction of airways smooth musculature in the newborn with meconium aspiration syndrome (MAS).

The role of meconium in the respiratory system was studied in newborns, who died from various causes (250 up to 3000 g of weight). We monitored tracheal rings response to dopamine, serotonin and ethanol in different concentrations (dopamine: 0,05 mg/ml, 0,5 mg/ml, 5 mg/ml; serotonin (5-HT): 10-4, 10-3, 10-2, 10-1 mol/dm3; ethanol: 0,02 ml, 0,5 ml, 1,0 ml; 96%). Tracheal smooth musculature tonus (TSM) was examined in 48 tracheal preparations taken after the newborn exitus due to different reasons. Based on functional researche of isolated preparations of tracheas, it may be concluded that: aspiration of meconium has not changed the response of TSM to dopamine, serotonin and ethanol (p>0,1) in comparison with the control group, which have died due to different lung inflammatory processes (e.g. pneumonia, bronchopneumonia, atelectasis, cerebral hemorrhage). The results suggest that meconium does not potentiate the constricting action of dopamine, serotonin and ethanol in tracheobronchial system. Meconium causes mild relaxation of the TSM through a mechanism that is not intermediated by the products of cyclooxygenases (prostaglandins, prostacyclins) from the tracheal epithelium or proteins. Also, as it seems, the direct activity of many tested acids in the smooth musculature has no significant impact on increase of the airways tonus in MAS syndrome.