Effects of subchronic versus acute in utero exposure to dexmedetomidine on foetal developments in rats

Unraveling the effects of prenatal anesthesia on neurodevelopment: A review of current evidence and future directions

Human brain development is a complex, multi-stage, and sensitive process, especially during the fetal stage. Animal studies over the last two decades have highlighted the potential risks of anesthetics to the developing brain, impacting its structure and function. This has raised concerns regarding the safety of anesthesia during pregnancy and its influence on fetal brain development, garnering significant attention from the anesthesiology community. Although preclinical studies predominantly indicate the neurotoxic effects of prenatal anesthesia, these findings cannot be directly extrapolated to humans due to interspecies variations. Clinical research, constrained by ethical and technical hurdles in accessing human prenatal brain tissues, often yields conflicting results compared to preclinical data. The emergence of brain organoids as a cutting-edge research tool shows promise in modeling human brain development. When integrated with single-cell sequencing, these organoids offer insights into potential neurotoxic mechanisms triggered by prenatal anesthesia. Despite several retrospective and cohort studies exploring the clinical impact of anesthesia on brain development, many findings remain inconclusive. As such, this review synthesizes preclinical and clinical evidence on the effects of prenatal anesthesia on fetal brain development and suggests areas for future research advancement.

Intrathecal dexmedetomidine versus magnesium sulphate for postoperative analgesia and stress response after caesarean delivery; randomized controlled double-blind study

BACKGROUND

Various adjuvants were added to intrathecal anaesthetics to improve quality of the block and postoperative analgesia. We hypothesized that intrathecal dexmedetomidine and magnesium sulphate (MgSO₄ ) may add similar effects. Our objectives were to compare their effects as adjuvants to intrathecal bupivacaine on postoperative analgesia, stress hormones, sedative properties and the neonatal outcome after caesarean section.

METHODS

A randomized double-blind controlled study; 90 parturients were divided into three groups. All patients received intrathecal hyperbaric bupivacaine 12.5 mg. NaCl 0.9% was added to intrathecal block in group C, 5 μg dexmedetomidine in the group D and 50 mg MgSO₄ in group M. Visual analogue scale (VAS) score, stress hormones were assessed within the first 12 postoperative hours, sensory block, and neonatal outcome were also assessed.

RESULTS

VAS scores were significantly lower in groups D and M. Onset of postoperative pain was significantly prolonged in group D. Time to peak sensory level was shorter in group D. Sedation score was significantly higher in group D only after 30 min of intrathecal block. Although stress hormones increased in all groups during intraoperative and postoperative periods, their levels were significantly lower in group D compared to other groups. No differences were noted regarding neonatal outcomes.

CONCLUSION

Intrathecal dexmedetomidine is superior to intrathecal MgSO₄ during caesarean section with regard to duration of analgesia, pain severity and stress hormone levels. Dexmedetomidine has a rapid onset and longer duration of sensory block compared to MgSO₄ . No significant adverse effects to the parturients or newborns.

Dexmedetomidine Ameliorates the Neurotoxicity of Sevoflurane on the Immature Brain Through the BMP/SMAD Signaling Pathway

Numerous studies have demonstrated that general anesthetics might damage the nervous system, thus, the effect of general anesthetics on the developing brain has attracted much attention. Dexmedetomidine (Dex) exhibits a certain neuroprotective effect, but the mechanism is obscure. In our study, pregnant rats on gestational day 20 (G20) were exposed to 3% sevoflurane for 2 h or 4 h, and the neuronal apoptosis in hippocampal CA1 region of the offspring rats was detected by quantification of TUNEL positive cells and cleaved-caspase3 (cl-caspase3). Different doses of Dex were intraperitoneally injected before sevoflurane anesthesia; then, the expression of apoptotic-related proteins including BCL-2, BAX and cl-caspase3 as well as amyloid precursor protein (APP, a marker of axonal injury), p-CRMP-2 and CRMP-2 were measured at postnatal days 0, 1and 3 (P0, P1, and P3, respectively). As an antagonist of the bone morphgenetic proteins (BMP) receptor, DMH1 was co-administered with sevoflurane plus Dex to investigate whether BMP/SMAD is associated with the neuroprotective effects of Dex. The results showed that prenatal sevoflurane anesthesia for 4 h activated apoptosis transiently, as manifested by the caspase3 activity peaked on P1 and disappeared on P3. In addition, the expressions of APP and p-CRMP-2/CRMP-2 in postnatal rat hippocampus were significantly increased, which revealed that prenatal sevoflurane anesthesia caused axonal injury of offspring. The long-term learning and memory ability of offspring rats was also impaired after prenatal sevoflurane anesthesia. These damaging effects of sevoflurane could be mitigated by Dex and DMH1 reversed the neuroprotective effect of Dex. Our results indicated that prenatal exposure to 3% sevoflurane for 4 h increased apoptosis and axonal injury, even caused long-term learning and memory dysfunction in the offspring rats. Dex dose-dependently reduced sevoflurane- anesthesia-induced the neurotoxicity by activating the BMP/SMAD signaling pathway.

Effect and placental transfer of dexmedetomidine during caesarean section under epidural anaesthesia

Objective To investigate the neonatal effect and placental transfer of dexmedetomidine during caesarean section under epidural anaesthesia. Methods Forty parturients with a single newborn who were scheduled for caesarean section were enrolled. Patients received 0.5 µg/kg dexmedetomidine 10 min after epidural anaesthesia, followed by 0.5 µg/kg/h until abdominal closure (Dex group) or infusion of normal saline (NS group). Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were monitored before infusion (T0), 10 min after infusion (T1), at delivery (T2), and at the end of the operation (T3). Umbilical vein and artery blood was collected. Apgar scores were evaluated at 1 and 5 min after delivery. Results SBP, DBP, and HR in the Dex group were decreased at T3 compared with T0 (116 ± 10.4 vs 111 ± 9.2 mmHg, 74 ± 6.7 vs 66 ± 7.9 mmHg, 91 ± 12.1 vs 71 ± 8.4 beats/min, respectively, P < 0.05). HR was lower at T1, T2, and T3 in the Dex group compared with the NS group ( P < 0.05). There were no significant differences in blood gases and Apgar scores between the groups ( P > 0.05). Conclusion Dexmedetomidine during caesarean section under epidural anaesthesia is beneficial to parturients. The placental transfer rate is 0.68.

Neuroprotection and neurotoxicity in the developing brain: an update on the effects of dexmedetomidine and xenon

Growing and consistent preclinical evidence, combined with early clinical epidemiological observations, suggest potentially neurotoxic effects of commonly used anesthetic agents in the developing brain. This has prompted the FDA to issue a safety warning for all sedatives and anesthetics approved for use in children under three years of age. Recent studies have identified dexmedetomidine, the potent α2-adrenoceptor agonist, and xenon, the noble gas, as effective anesthetic adjuvants that are both less neurotoxic to the developing brain, and also possess neuroprotective properties in neonatal and other settings of acute ongoing neurologic injury. Dexmedetomidine and xenon are effective anesthetic adjuvants that appear to be less neurotoxic than other existing agents and have the potential to be neuroprotective in the neonatal and pediatric settings. Although results from recent clinical trials and case reports have indicated the neuroprotective potential of xenon and dexmedetomidine, additional randomized clinical trials corroborating these studies are necessary. By reviewing both the existing preclinical and clinical evidence on the neuroprotective effects of dexmedetomidine and xenon, we hope to provide insight into the potential clinical efficacy of these agents in the management of pediatric surgical patients.

Dexmedetomidine mitigates isoflurane-induced neurodegeneration in fetal rats during the second trimester of pregnancy

Dexmedetomidine has significant neuroprotective effects. However, whether its protective effects can reduce neurotoxicity caused by isoflurane in fetal brain during the second trimester of pregnancy remains unclear. In this study, timed-pregnancy rats at gestational day 14 spontaneously inhaled 1.5% isoflurane for 4 hours, and were intraperitoneally injected with dexmedetomidine at dosages of 5, 10, 20, and 20 μg/kg 15 minutes before inhalation and after inhalation for 2 hours. Our results demonstrate that 4 hours after inhaling isoflurane, 20 μg/kg dexmedetomidine visibly mitigated isoflurane-induced neuronal apoptosis, reversed downregulation of brain-derived neurotrophic factor expression, and lessened decreased spatial learning and memory ability in adulthood in the fetal rats. Altogether, these findings indicate that dexmedetomidine can reduce neurodegeneration induced by isoflurane in fetal rats during the second trimester of pregnancy. Further, brain-derived neurotrophic factor participates in this process.

Comparison of Intrathecal Dexmedetomidine with Morphine as Adjuvants in Cesarean Sections

To compare the effects of intrathecal dexmedetomidine and intrathecal morphine as supplements to bupivacaine in cesarean sections under spinal anesthesia. Full-term parturients (n=120) undergoing elective cesarean sections under spinal anesthesia were randomly allocated into three groups: Group B received 10 mg bupivacaine, Group BD received 10 mg bupivacaine plus 5 µg dexmedetomidine, and Group BM received 10 mg bupivacaine plus 100 µg morphine. The onset and regression time of sensory and motor blockade, postoperative analgesia, and side effects were recorded. Group BD showed quicker onset time and a longer sensory and motor blockade than other groups (BD vs. B and BD vs. BM, p<0.05). The mean time of sensory regression to the S1 segment was 253.21±42.79 min in group BD, 192.50±40.62 min in group BM and 188.33±37.62 min in group B (p<0.001). Group BD showed an analgesia duration (time to requirement of first rescue analgesic) (17.59±6.23 h) similar to that of group BM (16.78±5.90 h) but longer than that of group B (3.53±1.68 h) (p<0.001). The incidence of pruritus was significantly higher in group BM compared with groups BD and B (p<0.001). Less shivering was observed in group BD than in groups BM and B (p=0.009). So intrathecal dexmedetomidine (5 µg) prolonged the motor and sensory blockade, provided a similar analgesic effect and reduced pruritus and shivering compared with morphine (100 µg) in cesarean sections.

Dexmedetomidine protects spatial learning and memory ability in rats

BACKGROUND

The authors tested the hypothesis that combined use of dexmedetomidine on fetal rats during isoflurane exposure in maternal anesthesia can attenuate the abnormal spatial learning and memory abilities in adults via the renin-angiotensin-aldosterone system.

METHODS

Fifty timed-pregnancy rats were randomly assigned to five groups (Dex+Iso, Sal+Iso, Sal+Oxy, Dex+Oxy, and a control group ) on embryonic day 14 to receive five different dispositions, i.e. combined injection of dexmedetomidine (Dex) or saline (Sal) and inhalation of isoflurane (Iso), oxygen (Oxy), or normal air for 4 h (n = 10).

RESULTS

The latency time(s) from day 1 to day 4 all showed a decreasing tendency in all four groups. The synaptic count of the Sal+Iso group was significantly lower than the Control group (p < 0.05), suggesting that severe neurodegeneration occurred under the influence of fetal isoflurane exposure. In contrast, the synapse count of the Dex+Iso group was near to that of Control group. The rats are protected in neurodevelopmental, normal development.

CONCLUSION

Combine use of dexmedetomidine during exposure to isoflurane in utero during middle-pregnancy can attenuate the impairment of spatial learning and memory abilities for the rats in adulthood.

Respiratory Failure and Mechanical Ventilation in the Pregnant Patient

Fewer than 2% of all peripartal patients need intensive care unit admission. But due to some anatomic and physiologic changes in pregnancy, respiratory failure can be promoted. This article reviews several obstetric and nonobstetric diseases that lead to respiratory failure and the treatment of these. Furthermore, invasive and noninvasive ventilation in pregnancy is discussed and suggestions of medication during ventilation are given.

Intraoperative conditions and quality of postoperative analgesia after adding dexmedetomidine to epidural bupivacaine and fentanyl in elective cesarean section using combined spinal-epidural anesthesia

This study was designed to evaluate the effect of adding dexmedetomidine to regular mixture of epidural drugs for pregnant women undergoing elective cesarean section with special emphasis on their sedative properties, ability to improve quality of intraoperative, postoperative analgesia, and neonatal outcome.

When one drug affects 2 patients: a review of medication for the management of nonlabor-related pain, sedation, infection, and hypertension in the hospitalized pregnant patient

One of the most difficult challenges health care providers encounter is drug selection for pregnant patients. Drug selection can be complex as efficacy and maternal side effects must be weighed against potential risk to the embryo or fetus. Verification of an individual drug's fetal safety is limited as most evidence is deduced from epidemiologic, prospective cohort, or case-control studies. Medication selection for the pregnant inpatient is a particularly complex task as the illnesses and conditions that require hospitalization mandate different medications, and the risk versus benefit ratio can vary significantly compared to the outpatient setting. Some degree of acute pain is not uncommon among inpatients. Acetaminophen is generally considered the drug of choice in pregnancy for mild to moderate acute pain, while most opioids are thought to be safe for short-term use to manage moderate to severe pain. Providing sedation is particularly challenging as the few options available for the general population are further limited by either known increased risk of congenital malformations or very limited human pregnancy data. Propofol is the only agent recommended for continuous sedation, which has a Food and Drug Administration classification as a pregnancy category B medication. Treatment of infections in hospitalized patients requires balancing the microbiology profile against the fetal risk. Older antimicrobials proven generally safe include beta-lactams, and those with proven fetal risks include tetracyclines. However, little to no information regarding gestational use is available on the newer antimicrobials that are frequently employed to treat resistant infections more commonly found in the inpatient setting. Management of maternal blood pressure is based on the severity of blood pressure elevations and not the hypertensive classification. Agents generally considered safe to use in hypertensive pregnant patients include methyldopa, labetolol, and hydralazine, while angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, hydrochlorothiazide, and atenolol should be avoided.