Health Hazards and Nitrous Oxide: A Time for Reappraisal

1991 | PMID: 1809046

“Although N2O was for many years believed to have no toxicity other than that associated with its anesthetic action, bone marrow depression in patients administered N2O for extended periods of time and neurological abnormalities in health care workers who inhaled N2O recreationally have disproved this notion. Retrospective surveys of dental and medical personnel have also linked occupational exposure to N2O with a number of health problems and reproductive derangements. Nitrous Oxide reacts with the reduced form of vitamin B12, thereby inhibiting the action of methionine synthase, an enzyme that indirectly supports methylation reactions and nucleic acid synthesis. Many, if not all, of the nonancsthetic-related adverse effects of N2O may be ascribed to this action. Animal and human studies indicate that the toxic effects of N2O are concentration- and time-dependent.”

General Anesthesia May Impair Kids’ Language Learning

“The present findings suggest that general anesthesia for a surgical procedure in early childhood may be associated with long-term diminution of language abilities and cognition, as well as regional volumetric alterations in brain structure,” the authors wrote.

“A 2013 study published in Pediatric Anesthesia found that the “odds of a formal diagnosis of learning disability by age 12 years in apparently healthy children exposed to general anesthesia for minor surgery during infancy were 4.5 times greater than their peers who had never been exposed to anesthesia.”

THE ALTERNATIVE: REGIONAL ANESTHESIA

“Previous studies have shown no cognitive impairment following regional anesthesia. A 2014 study published in Anesthesia & Analgesia found no link between duration of surgery in an infant under spinal anesthesia and scores on academic achievement tests in elementary school. “We also found no relationship between infant [spinal anesthesia] and surgery with [very poor academic achievement] on elementary school testing,” the authors wrote.”

Using General Anaesthetic on Infants Could Harm Their Memory for Life - Study

“General anaesthesia before the age of one may impair memory later in childhood, possibly life-long, a study has suggested. This was the conclusion of scientists who compared the recollection skills of two groups of children — some who had undergone anaesthesia in infancy and others who had not. The children, aged six to 11 and divided into two groups of 28 each, were tested over a period of 10 months for their ability to recollect specific drawings and details therein. The children who had been anaesthetised as babies had about 28 percent less recollection on average than their peers, and scored 20 percent lower in tests that assessed how much detail they could remember about the drawings. “The children did not differ in tests measuring intelligence or behaviour, but those who had received anaesthesia had significantly lower recollection scores,” said a media summary provided by the journal Neuropsychopharmacology, which published the results. Recollection plays a role in autobiographical memory, classroom learning and reading comprehension. “Thus, even subtle recollection deficits may have immediate consequences and reduce the child’s potential to learn over time, which future studies should examine more closely,” wrote the University of California team.”

Anesthesia-Induced Developmental Neurotoxicity in Children: Past, Present, and Future

2019 | PMID: 31369429 | DOI: 10.1097/CM9.0000000000000377

“Since 1999, a large body of evidence from various animal models indicates a link between anesthesia exposure in early stage of life and subsequent neurodevelopmental impairments; namely, almost all commonly used intravenous and inhalational anesthetics, including gamma aminobutyric acid agonists and N-methyl-D-aspartate antagonists, can induce dose and age dependent neuronal apoptosis and death in vitro.”

”Alarmingly, these neurotoxic effects by neonatal exposure to anesthesia may result in the long-term detrimental functional outcomes in later childhood or adulthood, such as deficits in memory, learning, attention, and motor function.”

“It is both a responsibility and an opportunity for specialties such as anesthesiology, surgery, and neurology to work together to address this critical public health issue closely related to clinical anesthesia of pediatric and pregnant patients until a clear solution about the source of this potential harm to the developing brain is obtained.”

Pediatric Anesthesia Neurotoxicity: An Overview of the 2011 SmartTots Panel

2011 | PMID: 22021791 | DOI: 10.1213/ANE.0b013e3182326622

“Through the years, care of millions of premature infants and young children has resulted in numerous exposures to a variety of anesthetic and sedative agents. These agents, designed to achieve the substantial depth of neuronal inhibition required for complete loss of consciousness and insensitivity to pain, are often a necessary component of successful treatment. However, data collected in animal models over the past decade suggest that general anesthetics damage developing neurons. Emerging animal and human data also suggest an association between early exposure to general anesthesia and long-term impairment of cognitive development. Consequently, the prudence of administering anesthesia to this population is now being scrutinized. Because general anesthesia cannot often be avoided when young children are diagnosed with conditions requiring surgery, or undergo time in intensive care units, the scientific community is focused on gaining a thorough understanding of the mechanisms of action so that we may take full advantage of the beneficial effects of anesthetics and sedatives without potentially devastating neurotoxic outcomes.”

The Role of Vitamin B12 in the Management and Optimization of Treatment in Patients With Degenerative Cervical Myelopathy

2019 | PMID: 31192102 | DOI: 10.1177/2192568218758633

ON THE BASIS OF PREOPERATIVE PLANNING:

“N2O irreversibly oxides the cobalt ion at the center of B12, and impedes its crucial cofactor function for methionine synthetase. This enzyme is required for the formation of tetrahydrofolate (THF) and methionine. THF is involved in thymidine synthesis and DNA production, while methionine is required for the methylation of myelin sheath phospholipids. Consequently, patients with already low levels of B12 or methylene-tetrahydrofolate-reductase deficiency are particularly at risk for perioperative myelopathy due to N2O administration. Given that N2O can be used during spine surgery, this points to the necessity of routinely monitoring B12 levels in patients with DCM to optimize surgical outcomes and prevent perioperative or postoperative neurological deficit development. Recognition of this phenomenon is important, as intramuscular injection of B12 has been shown to rapidly reverse SACD symptoms.”

RESULTS:

“Vitamin B12 deficiency can result in subacute combined degeneration of the spinal cord (SACD), and several case reports have pointed to patients with both DCM and SACD. Both SACD and reversible compressive injury due to DCM necessitate remyelination in the spinal cord, a process that requires adequate vitamin B12 levels. Basic science research on nerve crush injuries have shown that vitamin B12 levels are altered after nerve injury and that vitamin B12 along with dexamethasone or nonsteroidal anti-inflammatory drugs can reduce Wallerian degeneration. Furthermore, it has been suggested that a combination of B-vitamins can reduce glutamate-induced neurotoxicity.”

CONCLUSIONS:

“Given the high prevalence of clinical and subclinical vitamin B12 deficiency in the elderly, the role of vitamin B12 in myelination, and vitamin B12 deficiency as a differential diagnosis of DCM, it is important to investigate what role vitamin B12 levels play in patients with DCM in terms of baseline neurological function and whether optimization of vitamin B12 levels can improve surgical outcome.”