Fatal errors in nitrous oxide delivery

[Nitrous oxide as a party drug]

In recent years, reports of health problems associated with nitrous oxide consumption have significantly increased. In Germany, nitrous oxide (N2O) is easily available in cartridges without legal restrictions. The main reason for its popularity in the party scene are the euphoric, psychedelic effects of the gas. In addition to severe and sometimes irreversible health problems associated with long-term use of nitrous oxide, e.g., anemia and nerve damage, life-threatening or fatal consequences of acute nitrous oxide consumption can also occur: accidents under the influence of nitrous oxide, pneumothorax, pneumopericardium and shock due to an explosive increase in airway pressure when inhaled directly from the cartridge. But the most common cause of severe complications is asphyxia as the gas is usually inhaled pure from large balloons and without oxygen. The resulting hypoxia during use may be perpetuated by the diffusion hypoxia that occurs during the reoxygenation period. Nitrous oxide as a cause in accidental or intoxication events is usually not detectable but can only be identified as a trigger based on the patient's history or the circumstances. Acute medical treatment is symptomatic.

Nitrous oxide intoxication: systematic literature review and proposal of new diagnostic possibilities

Background

Nitrous oxide (N2O), also called “laughing gas,” is the most commonly used inhalation anesthetic in dentistry. The N2O is no longer used, because of the long-term neurologic and cardiovascular sequelae. Due to its sedative and euphoric properties, N2O is often used for recreational use or in some erotic activities. Accidental deaths are mainly associated with the uses of N2O: death can occur from sudden cardiac arrhythmia or, most commonly, acute asphyxiation due to hypoxia. This paper aims to study the literature concerning deaths due to N2O intoxication and highlight pathological findings useful for diagnosis when the crime scene investigation does not reveal any evidence.

Materials and methods

The authors conducted the literature search by PubMed and Scopus databases, searching for articles from 1 January 1970 to 1 March 2020 using the key terms: “Nitrous oxide,” “Laughing gas,” “Hypoxic damage,” “Nitrous oxide anesthesia,” and “Nitrous oxide death.”

Results and discussion

A total of 244 articles were collected. Only 26 articles were included in the systematic review. Most of the deaths from intoxication are due to asphyxiation; the diagnosis is often difficult and immunohistochemistry could be helpful. Nitrous oxide increases the intracellular adhesion molecule expression, E- and P-Selectin (markers of the early inflammatory response), and HIF-1 α (indicative of oxidative stress during ischemia-reperfusion).

Conclusion

The macroscopic and microscopic signs of N2O intoxication are non-specific, but N2O has been proven to cause hypoxic damage to the brain. The suspicion of the presence of the gas in the environment should guide the pathologist. Tissue analyzes provide important information; immunohistochemical stains can confirm hypoxic damage through the use of markers such as HIF-1 α, E-Selectin, and P-Selectin.

Failures of the Oxygen Supply

Oxygen supply failures are potentially life-threatening and are often associated with death or brain damage. Knowledge of how oxygen is supplied is essential for understanding how failures are caused and their management. Even though safety mechanisms exist to reduce the likelihood of a supply failure, events still occur. Simulation studies have identified knowledge and performance gaps in management of supply failures. A straightforward approach to immediate management of these critical events is provided.

Delivery of anoxic gas mixtures in anaesthesia: case report and review of the struggle towards safer standards of care

In 1983 a patient at The Alfred Hospital, Melbourne died during general anaesthesia for emergency surgery, in the weeks following maintenance to the operating theatre gas supply. In the ensuing investigation, it was revealed that he had been given 100% nitrous oxide throughout the anaesthetic due to the inadvertent crossing of the nitrous oxide and oxygen pipelines during the repair work. In this article we review the published literature on the delivery of hypoxic and anoxic gas mixtures, and the associated morbidity and mortality. We explore the developments that took place in the delivery of anaesthetic gases, and the unforeseen dangers associated with these advances. We consider the risks to patient safety when technological advances outpaced the implementation of essential safety standards. We investigate the events that pushed the development of safer standards of anaesthetic practice and patient monitoring, which have contributed to modern day theatre practice. Finally, we consider the risks that still exist in the hospital environment, and the need for on-going vigilance.

Anaesthesia machine: checklist, hazards, scavenging

From a simple pneumatic device of the early 20(th) century, the anaesthesia machine has evolved to incorporate various mechanical, electrical and electronic components to be more appropriately called anaesthesia workstation. Modern machines have overcome many drawbacks associated with the older machines. However, addition of several mechanical, electronic and electric components has contributed to recurrence of some of the older problems such as leak or obstruction attributable to newer gadgets and development of newer problems. No single checklist can satisfactorily test the integrity and safety of all existing anaesthesia machines due to their complex nature as well as variations in design among manufacturers. Human factors have contributed to greater complications than machine faults. Therefore, better understanding of the basics of anaesthesia machine and checking each component of the machine for proper functioning prior to use is essential to minimise these hazards. Clear documentation of regular and appropriate servicing of the anaesthesia machine, its components and their satisfactory functioning following servicing and repair is also equally important. Trace anaesthetic gases polluting the theatre atmosphere can have several adverse effects on the health of theatre personnel. Therefore, safe disposal of these gases away from the workplace with efficiently functioning scavenging system is necessary. Other ways of minimising atmospheric pollution such as gas delivery equipment with negligible leaks, low flow anaesthesia, minimal leak around the airway equipment (facemask, tracheal tube, laryngeal mask airway, etc.) more than 15 air changes/hour and total intravenous anaesthesia should also be considered.

Oxygen concentrators performance with nitrous oxide at 50:50 volume

BACKGROUND AND OBJECTIVES

Few investigations have addressed the safety of oxygen from concentrators for use in anesthesia in association with nitrous oxide. This study evaluated the percent of oxygen from a concentrator in association with nitrous oxide in a semi-closed rebreathing circuit.

METHODS

Adult patients undergoing low risk surgery were randomly allocated into two groups, receiving a fresh gas flow of oxygen from concentrators (O293) or of oxygen from concentrators and nitrous oxide (O293N2O). The fraction of inspired oxygen and the percentage of oxygen from fresh gas flow were measured every 10 min. The ratio of FiO2/oxygen concentration delivered was compared at various time intervals and between the groups.

RESULTS

Thirty patients were studied in each group. There was no difference in oxygen from concentrators over time for both groups, but there was a significant improvement in the FiO2 (p<0.001) for O293 group while a significant decline (p<0.001) for O293N2O. The FiO2/oxygen ratio varied in both groups, reaching a plateau in the O293 group. Pulse oximetry did not fall below 98.5% in either group.

CONCLUSION

The FiO2 in the mixture of O293 and nitrous oxide fell during the observation period although oxygen saturation was higher than 98.5% throughout the study. Concentrators can be considered a stable source of oxygen for use during short anesthetic procedures, either pure or in association with nitrous oxide at 50:50 volume.

[False positive death certification. Does the Lazarus phenomenon partly explain false positive death certification by rescue services in Germany, Austria and Switzerland?]

Apart from misdiagnosis, the Lazarus phenomenon, a spontaneous return of circulation after cardiac arrest, is a potential cause for false positive death certification. Because of medicolegal consequences and thus a negative publication bias, the incidence of false positive death certification is unknown. As a false positive death certification results in criminal prosecution and thus media interest, numerous media archives in Germany, Austria and Switzerland were searched for such reports. A total of nine cases of false positive death certification in these three countries were identified since the early 1990s of which eight occurred in an emergency medical service system setting. Apart from a lack of diligence of emergency physicians, a Lazarus phenomenon could be the reason for such incidents. As definite signs of death will not have developed only a few minutes after stopping CPR it might be difficult for an emergency physician to definitely certify a patient's death in an out-of-hospital setting with 100% safety. Thus, prehospital death certification poses a risk of error and subsequent legal prosecution of the emergency physician, as a Lazarus phenomenon may still occur in this phase. Delegation of death certification from emergency physicians to qualified physicians in a follow-up examination might increase both legal safety for emergency physicians in the field and patient safety.