Cardiac arrest is a common event on earth, but with the development of space travel for recreational purposes and the plan to colonize other planets – particularly Mars – the need for the provision of basic and advanced life support during the journey, and the establishment of settlements has to include medical response and out-of-hospital care. This does, however, raise the question whether the current procedures and techniques being utilized on earth can be used to the same effect in a microgravity environment. Microgravity is the condition in which people or objects appear to be weightless, such as in space. This article will explore some key components of resuscitation and the challenges that may be faced by transferring these from earth into the weightless environment that is space.

Chest Compressions

Once cardiac arrest has been established, chest compressions need to be initiated. On earth compressions require kneeling alongside the patient and exerting pressure on the sternum with both hands. In microgravity this force cannot be exerted in the same way, as the weight and strength of the health care provider or bystander cannot be pushed downwards. The American Heart Association therefore researched the ideal method to perform CPR (cardiopulmonary resuscitation) in space and found the handstand method to be the most effective. This conclusion was further supported by Jay et al (2003). The technique requires the rescuer to essentially perform a handstand on the patient’s chest and pushing himself from the opposite end of the spacecraft with his legs towards the patient’s chest. However, this will only be a viable option in certain sizes of spacecraft or accommodation, and moving the patient might be required to perform efficient handstand compressions. Electrical/battery powered mechanical chest compression devices are likely to be of significant benefit in microgravity, as gas powered devices would require specialised refilling equipment.

Source: integrisequipment.com/LUCAS_2_Chest_Compression_System_p/99576-000011.htm

Defibrillation

In the event of a particularly hairy chest, shaving chest hair is required to improve adhesion of the defibrillation pads and reduce impedance, thus improving the transfer of current into the chest. On earth the hairs will simply fall to the ground and no longer be a concern. In microgravity these hairs will “float” around within the spacecraft or building, and can enter ventilation systems and other critical infrastructure. They may even lead to cross contamination between patients within the same area. Self-adhesive defibrillation pads are the most commonly utilised option for defibrillation and are likely to be the best choice in microgravity as well. Defibrillation paddles and gel are likely to result in potentially dangerous situations, thus their use should ideally be avoided.

Cannulation & vascular access

During cardiac arrest management drug administration is currently still recommended, thus making it essential to obtain vascular access. The procedure creates the problem that any bodily fluids (such as blood) and cleaning products to prepare the skin for cannulation may float freely around the area, enter critical systems, and may not provide the same level of cleanliness as it would on earth, as contaminants would be moving around in the same fashion. Once the catheter has been inserted the disposal of the contaminated sharp is the next point of concern. Most of the sharps containers in practice are not designed to completely contain the sharps from “floating” out of it due to their design. Unless they are redesigned this would allow these sharps to re-emerge and pose a risk to everyone within the vicinity. If pharmacological interventions, such as epinephrine (adrenaline), are removed from practice, then this challenge would of course become less of a concern.

Pharmacology & Drug Therapy

Regardless whether microgravity and exposure to various ultraviolet rays can negatively affect pharmacological agents used during cardiac arrest management, the biggest challenge at this time is the current shelf life. Twelve, 18, or 36 months are simply not sufficient to allow for extended space exploration missions, as their lifetime could have been exceeded by the time the destination is reached. Even regular resupply attempts would not be beneficial unless shelf life can be extended; they would be expired soon after they reached places like a clinic or hospital on Mars, for example, before placing them on a craft departing for planets even further away. 

Assuming this is resolved, once drugs have been drawn up with a syringe or when using a pre-filled syringe, air bubbles will need to be removed before the drug can be administered. On earth, flicking the syringe moves the air bubbles towards the top and it can be expelled, but how could this be achieved in microgravity? A technique such as flicking the syringe and thereby propelling the bubble forwards might be the answer here. Administration of intravenous fluids would also have to be adjusted, as free flow (gravity-fed) administration of fluids would not be possible. Equipment such as pressure infusers or infusion pumps are most likely needed to achieve effective, controlled fluid administration rates. In the meantime, bolus administration via a 50 ml syringe could be considered, but this is a time consuming technique.

Source: ebay.com/itm/Medical-500ml-Blood-Pressure-Infusion-Bag-Pressure-Infuser-Bag-Infusor-Bag-Home-/401430581064

Airway Management

Simple steps, such as the insertion of a supraglottic airway, have now become standard practice in many countries during cardiac arrest. However, the risk of aspiration is significantly higher in microgravity, as gastric content, just like everything else, is not pulled or pushed towards a particular area of the body through the force of gravity. This does impact the management options in cardiac and respiratory arrest, as protection from aspiration is therefore a bigger concern than on earth. NASA astronauts are trained to intubate as part of their pre-flight training – possibly for this reason – as uncuffed, non-tracheal airway devices do not provide the benefit of aspiration protection.

Assuming a return of spontaneous circulation (ROSC), particularly following basic life support (BLS) resuscitation without advanced interventions, placing the patient in the recovery position is recommended in first aid and other courses, if no other intervention other than monitoring is required or the patient has no gag reflex. This does not provide any benefit in space, as the recovery position requires gravity to perform its job of aspiration and airway protection. So how could the airway be protected in such a case? Does intubation have to be the standard method of aspiration protection? What about patients with a decreased level of consciousness and a gag reflex – do they need to be sedated and intubated?

Patient Positioning to Manage Shock

Shock management guidelines, particularly in emergency care and first aid, often recommend the use of leg elevation to manage shock (Trendelenburg position), despite it not showing benefits in improving systolic blood pressure. When exposed to microgravity its value would undoubtedly be even less. But could previously discarded techniques to manage shock and hypotension, such as Military Anti Shock Trousers (MAST) or the Pneumatic Anti Shock Garment (PASG) make a return to assist with managing shock in microgravity?

Management of cardiac arrest in microgravity, while very similar to management on earth, presents the healthcare provider with multiple challenges that have not yet been fully explored or researched. Hence, best practice standards have yet to be established. Solutions may include the revival of novel techniques or development of new approaches, but this remains to be seen. The age of resuscitation in microgravity research is yet to come.

References

Jay , GD, Lee, P, Goldsmith, H, Battat, J, Maurer, J, Suner, S. 2003, CPR effectiveness in microgravity: comparison of three positions and a mechanical device. Aviation, Space, and Environmental Medicine. https://www.ncbi.nlm.nih.gov/pubmed/14620476

NASA, 2017, nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-microgravity-58.html


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