Effects of experimental hypercapnia on hippocampal long-term potentiation in anesthetized rats

Perioperative management of esophageal atresia/tracheo-esophageal fistula: An analysis of data of 101 consecutive patients

BACKGROUND

The perioperative management of esophageal atresia/tracheo-esophageal fistula by open or thoracoscopic approach can be complicated by metabolic derangements. Little is known, however, about the severity of derangements of vital and metabolic parameters in the perioperative period.

AIM

The aim of this study is to describe the perioperative courses of vital and metabolic parameters in 101 consecutive neonates undergoing surgical repair of esophageal atresia type C.

METHOD

In a retrospective cohort study, we extracted all data from the electronic anesthetic and medical charts of patients who underwent esophageal atresia type C repair within 30 days of life (2007-2017). We distinguished three types of surgery: primary open, primary thoracoscopic, and primary thoracoscopic surgery converted to open surgery. Descriptive analysis was applied.

RESULTS

The charts of 117 patients were reviewed: data of 101 were included. The perioperative anesthetic management was not standardized; various methods and medications were used for anesthesia induction and maintenance. Intraoperative blood gas analysis data of 72 patients were available and showed derangements regardless of type of surgery. The median pH-value decreased to 7.21 [IQR 7.14-7.30] and a pH-value below 7.20 was found in 29 patients; in four cases below 7.0, with the lowest value 6.83. The median PaCO₂ reached an upper level of 7.5kPa [IQR 5.8-9.2]; in 13 cases above 10.0kPa, with a peak value of 25.8kPa. These high PaCO₂ levels fluctuated with lowest measured PaCO₂ of median 5.6 [IQR 4.5-6.6], with the lowest value 2.8kPa. The median PaO₂ level reached an upper level of 16.9kPa [IQR 11.8-25.7], in 22 cases above 20.0kPa, with a peak value of 50.0kPa. These high levels fluctuated with lowest measured PaO₂ levels of median 8.3kPa [IQR 6.73-10.5]; the lowest PaO₂ value was 4.7 kPa.

CONCLUSION

Open and thoracoscopic correction of esophageal atresia were associated with periods of severe metabolic derangements. These events need to be taken into account for the evaluation of esophageal atresia (surgical) care and in evaluations of short- and long-term outcomes.

Neonatal exposure to high concentration of carbon dioxide produces persistent learning deficits with impaired hippocampal synaptic plasticity

Although respiratory complications with blood gas abnormalities contribute significantly to neurodevelopment in the immature brain, little is known about the mechanisms via which blood gas abnormalities, such as hypoxic hypercapnia, impair neurocognitive outcomes. To investigate the possible long-term consequences of neonatal exposure to hypoxic hypercapnia regarding learning ability, we investigated the effect of neonatal hypoxic hypercapnia on later functions in the hippocampus, which is a structure that has been implicated in many learning and memory processes. Neonatal rat pups (postnatal day 7; P7) were exposed to a high concentration of carbon dioxide (CO2; 13%) for 2 or 4h. Exposure to CO2 in P7 rat pups caused blood gas abnormalities, including hypercapnia, hypoxia, and acidosis, and disrupted later learning acquisition, as assessed in 10-week-old adult rats subjected to a Morris water maze test. Induction of long-term potentiation (LTP) in the synapses of the hippocampal CA1 area was also impaired, whereas the paired-pulse responses of population spikes exhibited a significant increase, in CO2-exposed rats, suggesting decreased recurrent inhibition in the hippocampus. Such long-lasting modifications in hippocampal synaptic plasticity may contribute to the learning impairments associated with perinatal hypoxic hypercapnia and acidosis.

Aminophylline, administered at usual doses for rodents in pharmacological studies, induces hippocampal neuronal cell injury under low tidal volume hypoxic conditions in guinea-pigs

OBJECTIVES

To establish whether aminophylline, administered at usual doses for rodents in pharmacological studies, induces brain injury in systemic hypoxaemia in guinea-pigs.

METHODS

 A hypoxaemia (partial oxygen tension of arterial blood (PaO₂) = 40-60 mmHg) model was developed by low tidal volume mechanical ventilation in guinea-pigs.

KEY FINDINGS

Under hypoxic conditions, aminophylline significantly increased the concentration of brain-specific creatine kinase in the serum in a dose- and time-dependent manner. A reduced number of hippocampal neuronal cells in the CA1 region, an increase in the concentration of neuron-specific enolase (NSE) in cerebrospinal fluid (CSF), an increase in lipid hydroperoxides and a decrease in the ratio of glutathione to glutathione disulfide in the brain tissues were also observed. These effects were not observed when aminophylline at the same doses was administered under normoxic conditions (PaO₂ = 80-100 mmHg). There was no difference in either serum or CSF concentrations of theophylline between normoxic and hypoxic conditions. Another methylxanthine, caffeine, did not increase the concentration of NSE in CSF.

CONCLUSIONS

Aminophylline potentially induces brain damage under hypoxic conditions. We suggest that aminophylline treatment has adverse effects in patients with hypoxaemia subsequent to respiratory disorders such as asthma.

Snoring and obstructive sleep apnoea in children: why should we treat?

Frequent and loud snoring is a very frequent condition in prepubertal children affecting approximately 10% of all 2-8 year old children. If polysomnographical evaluations are performed in these snoring children, approximately 10% will be diagnosed with obstructive sleep apnoea (OSA). The pathophysiology of OSA in children is still poorly understood. Indeed, while adenotonsillar hypertrophy is certainly a major contributor to OSA, other factors need to be implicated for OSA to develop. In recent years, it has become apparent that OSA and snoring are not as innocuous as previously thought. Indeed, epidemiological and pre-post treatment analyses have identified substantial morbidities that primarily affect cardiovascular and neurobehavioural systems, namely pulmonary hypertension, systemic elevation of arterial blood pressure, nocturnal enuresis, reduced somatic growth, behavioural problems that resemble attention deficit-hyperactivity disorder, as well as learning and cognitive deficits. These problems are associated with marked increases in healthcare-related costs. More importantly, if timely diagnosis and intervention are not implemented, some of these morbid complications may not be completely reversible, leading to long-lasting residual consequences.

Neuroplasticity in respiratory motor control

Although recent evidence demonstrates considerable neuroplasticity in the respiratory control system, a comprehensive conceptual framework is lacking. Our goals in this review are to define plasticity (and related neural properties) as it pertains to respiratory control and to discuss potential sites, mechanisms, and known categories of respiratory plasticity. Respiratory plasticity is defined as a persistent change in the neural control system based on prior experience. Plasticity may involve structural and/or functional alterations (most commonly both) and can arise from multiple cellular/synaptic mechanisms at different sites in the respiratory control system. Respiratory neuroplasticity is critically dependent on the establishment of necessary preconditions, the stimulus paradigm, the balance between opposing modulatory systems, age, gender, and genetics. Respiratory plasticity can be induced by hypoxia, hypercapnia, exercise, injury, stress, and pharmacological interventions or conditioning and occurs during development as well as in adults. Developmental plasticity is induced by experiences (e.g., altered respiratory gases) during sensitive developmental periods, thereby altering mature respiratory control. The same experience later in life has little or no effect. In adults, neuromodulation plays a prominent role in several forms of respiratory plasticity. For example, serotonergic modulation is thought to initiate and/or maintain respiratory plasticity following intermittent hypoxia, repeated hypercapnic exercise, spinal sensory denervation, spinal cord injury, and at least some conditioned reflexes. Considerable work is necessary before we fully appreciate the biological significance of respiratory plasticity, its underlying cellular/molecular and network mechanisms, and the potential to harness respiratory plasticity as a therapeutic tool.

Behavioural and neurocognitive implications of snoring and obstructive sleep apnoea in children: facts and theory

The pathophysiology of obstructive sleep apnoea (OSA), a common condition in children, is poorly understood. While adenotonsillar hypertrophy is certainly a major contributor, other factors are needed for OSA to develop. OSA has been associated with substantial morbidities primarily affecting cardiovascular and neurobehavioural systems which may not be completely reversed with appropriate treatment. This paper reviews the available information and attempts to provide the rationale for early diagnosis and treatment of OSA in children.