CEREBRAL GAS EMBOLISM (CGE)

The aim with this website is to provide information to ensure that clinicians understand the risk and can take the necessary preventative steps to avoid iatrogenic gas embolism. Diving related gas embolism is managed in the same way and prevention depend on safe diving practices which is taught during training.

Cerebral gas embolism (CGE) is not as uncommon as most clinicians think and is recognised by NHS England to benefit from Hyperbaric Oxygen therapy (HBOT) and is funded to be treated in selected hyperbaric units.

We are particularly interested to learn more about retrograde cerebral venous gas embolism (CVGE). All cases with air in the cerebral venous sinuses and tracts will be of great interest to us. The natural course and also response to hyperbaric treatment is still unknown. These may represent a large part of cases of CGE responding to a hyperbaric oxygen despite significant delays.

At present, the aim to offer Hyperbaric Oxygen therapy (HBOT) within 6 hours, is seldom attainable in the UK. However it is important to realise that many cases still benefit several hours beyond this golden window.

This can only improve if Clinicians have a clear action plan to deal with this potentially fatal disaster.

Cerebral Gas Embolism may have a fatal outcome and is often difficult to diagnose. Physicians with training in Diving Medicine are trained to have a high index of suspicion in case of diving related accidents or illness. Victims of trauma or iatrogenic gas embolism often are at a disadvantage of late diagnoses and suboptimal management. If they survive the acute insult, the risk of cerebral gas embolism (CGE) may still have devastating results. This is a potentially lethal complication of many invasive medical procedures. Our understanding of the aetiology, pathology and therapy is still evolving.

The incidence in most health care systems is unknown.

Hyperbaric units may have the most accurate estimation of the incidence⁽¹⁾, since most clinicians accept Hyperbaric Therapy (HBO) as the only useful treatment.

Causes of Cerebral Gas Embolism (CGE):

Virtually any medical procedure, including peripheral intravenous cannulation, could potentially allow air or gas to enter the circulation.

Any unexpected neurological event happening in healthcare or particularly a peri-procedural ‘stroke’ should elicit a careful consideration of gas embolism as a cause.

The main mechanisms of CGE are:

1. Injection of air /gas directly into the arterial system.

2. Paradoxically, from the venous system through an intracardiac right-to-left shunt, or where intracardiac shunt is excluded, AV malformations in the lungs or overwhelming of the pulmonary capillary filter mechanism.

   1. Retrograde Cerebral Venous Gas Embolism (RCVGE) (First described by Ploner⁽²⁾ and Schlimp⁽³⁾).

Schlimp et al⁽³⁾ and later Fracasso et al⁽⁷⁾ designed a laboratory model, explaining the flow dynamics that allow retrograde cerebral venous gas embolism. This may not answer all the questions, but potentially explain a very import issue. We aim to get a better understanding of CVGE with the help of interested clinicians reporting their cases.

The first case report of RCVGE treated with HBO was published in 2012⁽⁸⁾. A review of textbooks, Review Articles and Editorials of cerebral gas embolism indicates a lack of recognition of this variant of CGE⁽⁹⁾.

One case recovered with HBO⁽⁸⁾, others became forensic medicine literature⁽⁷⁾. Further cases should be reported in peer reviewed journals, but will also be appreciated in this register. Anonymity is guaranteed and could also be done by phone, e-mail or snail mail.

Example:

Air in the ophthalmic vein and central venous sinus (8)

Prevention:

The incidence of iatrogenic CGE is relatively low, with the reported incidence extremely low in most countries. In fact nobody have an idea of the real incidence. Presumably every case would be investigated by clinical risk managers when it occurs. A root cause analysis should be done and we will appreciate any ideas coming from such an analysis to be published on the website, and eventually in the literature to help others avoid this dreadful complication.

These ideas are not scientifically proven, but makes sense, based on analysis of real cases as well as near missed cases. Above all, they do not cost a lot of money, and can prevent morbidity and mortality for patients and save healthcare individuals and organisations a large amount of distress, embarrassment, and even money.

1. Avoid 'excessive' pressures when inflating any body cavity with gas, e.g. laparoscopies, thoracoscopies, gastrointestinal endoscopies.

2. Consider using carbon dioxide for insufflation in gastrointestinal endoscopies.

3. Adding colour to contrast material. Working in dimmed light, make it difficult to ensure all air is expelled from contrast injecting systems.

4. Use of tissue glue and/ or a purse string suture to close the orifice left when a big line e.g. dialysis line is removed. This applied particularly in older patients where the elasticity of the tissue does not allowed for closure of the tract in the expected 30 to 60 minutes. This could be done for all lines, because the watertight dressing often does not last very long.

5. Continuous vigilance, careful monitoring and care by an experienced neuro anaesthetist in cases where neurosurgery in the sitting position has to be done

6. Before any intravenous injection or infusion is started, the syringe or infusion set should be flushed by the person administering it, not assuming that the person setting it up has primed it or drawn up the drug even if the syringe is labelled.

7. When setting up invasive pressure measurement transducer systems, 2 people should check that the system is primed, and free of air bubbles. Gas bubbles flushed into the the arterial system under pressure is extremely dangerous. Two nurses are checking drugs and doing the same for arterial lines will add to safety without significant additional work.