Fetal breathing movements and the response to carbon dioxide in patients on methadone maintenance

Reduced fetal movements: the case of Fetomaternal Hemorrhage. Case series and proposal of a management protocol

Fetomaternal hemorrhage (FMH) was reported more than 60 years ago for the first time defined by the transfer or transfusion of fetal blood into the maternal circulation before or during delivery. The transfused volume is usually very small but when this value exceeds, it may be clinically significant. Antenatal diagnosis of severe FMH is difficult and it can be suspected in case of reduction of fetal movements, abnormal cardiotocography and ultrasound. FMH is associated to different adverse outcomes and admission to neonatal intensive care. The low incidence of FMH limits the studies, thus being able to rely only on diagnosis and retrospective studies. We present case series of FMH and analyze the steps with the purpose of defining a flow-chart for early diagnosis and management of FMH.

S-Methadone augments R-methadone induced respiratory depression in the neonatal guinea pig

Methadone is administered as a racemic mixture, although its analgesic and respiratory effects are attributed to R-isomer activity at the mu opioid receptor (MOP). Recently, we observed a four-fold increase in inspiratory time in 3-day-old guinea pigs following an injection of racemic methadone. We hypothesized that this effect was due to augmentation of R-methadone induced respiratory depression by the S-methadone isomer. In the current longitudinal study, we injected 3-, 7-, and 14-day-old neonatal guinea pigs with saline, R-methadone, S-methadone, or R- plus S-methadone in order to characterize the roles of the individual isomers, as well as the synergistic effects of co-administration. Using plethysmography, we measured respiratory parameters while breathing room air and during a 5% CO(2) challenge. S-Methadone alone had no respiratory effects. However, the R- plus S-methadone group showed greater respiratory depression and increased inspiratory time than the R-methadone group in the youngest animals, suggesting that the respiratory effects of R-methadone are augmented by S-methadone in early development.

Methadone-induced respiratory depression in the neonatal guinea pig

Respiratory depression, the most serious side-effect of opioid treatment, is well documented for morphine, the most commonly used opioid in neonatal care. Less is known about methadone, a clinically relevant opioid analgesic, especially during neonatal development. This study was undertaken to determine the neonatal respiratory effects of methadone. We hypothesize that methadone is equipotent to morphine, compared to our previous morphine results in the same animal model, but has a much longer duration of action, due to its longer elimination half-life. Neonatal guinea pigs (3-14 days old) randomly received a single subcutaneous dose of methadone or saline. Using a non-invasive plethysmographic method, we measured ventilatory and metabolic parameters before injection and at intervals for 32 hr after injection while pups breathed "room air" or 5% CO(2) gas mixtures. Methadone-induced depression of ventilation was most evident during 5% CO(2) challenge. The onset of drug effects was within 15 min for all ages and doses, but the duration of action decreased with age. While the depth of methadone-induced respiratory depression did not depend on pup age, the control of breathing was different in 3-day-old pups, where inspiratory time increased fourfold; twice that of older pups. We conclude that methadone induces a naloxone reversible respiratory depression in guinea pig neonates and, in the very young, causes an abnormal breathing pattern due to changes in respiratory timing. Methadone is more potent than morphine with respect to neonatal respiratory depression, but surprisingly, the duration of methadone action was not longer than morphine.

Opioids, sleep architecture and sleep-disordered breathing

Opioid use whether acute or chronic, illicit or therapeutic is prevalent in Western societies. Opioid receptors are located in the same nuclei that are active in sleep regulation and opioid peptides are suggested to be involved in the induction and maintenance of the sleep state. mu-Opioids are the most commonly used opioids and are recognized respiratory depressants that cause abnormal awake ventilatory responses to hypercapnia and hypoxia. Abnormal sleep architecture has been reported during the process of opioids induction, maintenance and withdrawal. During induction and maintenance of opioid use there is reduction of rapid eye movement (REM) sleep and slow wave sleep. More recently, central sleep apnoea (CSA) has been reported with chronic opioid use and 30% of stable methadone maintenance treatment patients have CSA. Given these facts, it is sobering to note the paucity of human data available regarding the effects of short and long-term opioid use on sleep architecture and respiration during sleep. In this manuscript, we review the current knowledge regarding the effects of mu-opioids on sleep and respiration during sleep and suggest research pathways to advance our knowledge and to explore the possible responsible mechanisms related to these effects.

Effects of opioid dependence and tobacco use on ventilatory response to progressive hypercapnia

Respiratory depression is a serious medical risk of opioid use. Most opioid abusers also smoke cigarettes, perhaps further compromising breathing. Differences in ventilatory response to nonhypoxic hypercapnia were studied in healthy volunteers with limited substance use (LU), tobacco smokers (SM), and opioid-dependent, methadone-maintained smokers (OD). The last two groups had similar current cigarette use and all groups were similar in gender and body mass index. Because previous data suggest that SM are sensitive to hypoxia but not hypercapnia, it was predicted that only the OD group would exhibit decreased carbon dioxide (CO(2)) sensitivity. All subjects rebreathed CO(2) during three identical sessions (four trials per session). Fractional end-tidal (Fet) CO(2) levels during repeated 4-min exposures to progressive hypercapnia (6% to 10%) were similar across groups. Ventilatory response (breathing rate, tidal volume and minute volume) linearly increased with FetCO(2) concentration and did not differ significantly across sessions. Relative to the LU and SM groups (which did not significantly differ), the CO(2)-minute volume and CO(2)-breathing rate functions were significantly shifted rightward (decrease in intercept but not slope) for OD subjects. These data are consistent with the hypothesis that chronic opioid exposure and/or short-term methadone maintenance (but not tobacco or nicotine use) produces a specific decrease in CO(2) sensitivity, primarily through an inhibitory effect on respiratory frequency.

Clinical management of methadone dependence during pregnancy

This is a review of the literature regarding the clinical management of pregnant women maintained on methadone treatment. The prevalence of opiate use, definition of opiate dependence, common concerns regarding methadone use in pregnancy, and maternal/fetal harm are addressed. Recommendations for nurses are synthesized from the clinical literature, clinical experiences, and the empirical literature. These recommendations address: antepartum issues including treatment, dosage and pharmacological considerations, medical conditions and lab tests, intrapartum issues, postpartum concerns including breastfeeding, neonatal withdrawal, and developmental effects associated with methadone.

Opioid dependence during pregnancy. Effects and management

This article describes the complex problems associated with opioid dependence during pregnancy. Medical, obstetric, and psychosocial problems are presented. Methadone maintenance for the treatment of opioid dependence is described in this article. Specific issues of appropriate methadone dose during pregnancy, medical withdrawal, and the relationship of methadone dose and the severity of neonatal abstinence also are discussed.

Control of breathing in babies of narcotic- and cocaine-abusing mothers

To learn if chemoreceptor control of breathing is abnormal in babies whose mothers took narcotics, cocaine, or both drugs during pregnancy, we performed hypoxia and hypercapnia challenges on 28 babies (greater than or equal to 36 weeks gestation). Six babies were exposed to narcotics, six to cocaine, nine to both drugs, and seven babies were controls. Studies were done at 3 and 8 weeks and 3 and 5 months of age. Gestational ages were similar, but birth weight was lower in the cocaine group. Respiratory rate was higher in both groups of cocaine-exposed babies at 3 weeks. End-tidal partial pressure of CO2 (PCO2) was decreased and partial pressure of O2 (PO2) increased at 3 and 8 weeks in babies exposed to narcotics plus cocaine. At 3 weeks, babies exposed to narcotics plus cocaine had a shift to the left in CO2 response with a normal slope; at 8 weeks, both intercept and slope were decreased. Responses to hypoxia were similar among the four groups. Babies exposed to narcotics plus cocaine before birth have abnormalities in control of breathing in the first months after birth.

Opioids and the developing organism: a comprehensive bibliography, 1984-1988

A comprehensive bibliography of the literature concerned with opioids and the developing organism for 1984-1988 is presented. Utilized with companion papers (Neurosci. Biobehav. Rev. 6:439-479; 1982; 8:387-403; 1984), these articles cover the clinical and laboratory references beginning in 1875. For the years 1984, 1985, 1986, 1987, and 1988, a total of 877 citations were recorded. A series of indexes accompanies the citations in order to make the literature more accessible. These indexes are divided into clinical and laboratory topics, and subdivided into such topics as the type of opioid explored and the general area of biological interest (e.g., physiology).

Analysis of components of fetal breathing cycles

The duration of the inspiratory phase (Ti) and the expiratory phase (Te) together with the relative amplitude (Amp) of successive breathing movements of the chest wall or abdominal wall were measured by real-time ultrasound in 12 fetuses of normal gestation. The observations were performed at 33-39 gestational weeks. The distributions of Ti, Te, the duration of the breathing cycle (Ttot), Amp and the ratios Amp/Ti and Ti/Te were all considerably skewed. Correlations between these variables differed markedly in different fetuses. Running correlations, however, showed the presence of alternations with time in the correlations between Ti and Te, and between Amp and Ttot. These findings suggest the possibility of central nervous system mechanisms controlling these events, operating over time spans considerably longer than the individual breathing cycle.