*5.1.2 Fluid shift*

Although not documented, headward fluid shift and facial oedema can complicate the intubating conditions [16]. Drug distribution during spinal anaesthesia may also be altered due to the cephalad fluid shift and is therefore not recommended, in microgravity [38].

#### *5.1.3 Gastrointestinal system*

Space motion sickness accompanies gastroesophageal reflux in astronauts, sometimes lasting the entire mission. It may even persist after their return to Earth. The gastroesophageal reflux along with decreased gastrointestinal motility puts the crew at a risk for pulmonary aspiration, both during and after flight [16, 17].

#### *5.1.4 Pharmacology in the space environment*

Both the pharmacokinetics and pharmacodynamics of drugs are altered in weightlessness [39].

Cardiovascular changes, weight changes, changes in hormonal, electrolyte and immunoglobulin levels, decrease in the amount of microsomal P-450 as well as its dependent enzymes are some of the factors that cause changes to the pharmacokinetic and pharmacodynamic properties of drugs in space [16, 40]. As a result, the corresponding drug dosages need to be altered as well [39].

Also, long term storage of drugs may render them ineffective or even toxic [16].

A notable mention: the depolarising muscle relaxant succinylcholine is contraindicated due to disuse atrophy of muscles and changes in the neuromuscular junction, and the increased risk of hyperkalemia after prolonged exposure to microgravity [17, 39]. Instead, rocuronium is recommended to be used as an alternative [16, 41].

#### *5.1.5 Choice of anaesthetic technique*

One of the limiting aspects of the anaesthesia protocol for microgravity is that it should be carried out by a small crew of non-medical personnel, with limited training. In several low-income countries, anaesthetic procedures are regularly performed by non-medical personnel, with relatively low complications. Simplified versions of the protocols—one which can easily be followed by non-physicians must be developed.

The worst case scenario approach should be the basis for making the choice of the anaesthetic technique. It must be borne in mind that astronauts who may require anaesthesia in space may have to be managed by nonmedical personnel with limited training, in case the crew medical officer (CMO) is incapacitated or deceased. In addition, they maybe hypovolemic, deconditioned, at a risk for rhythm disturbances and gastric aspiration, and intolerant to succinylcholine [16].

Although ultrasound guided regional anaesthesia may be used safely and successfully, it requires considerable training [16, 38, 42, 43]. Spinal anaesthesia is not feasible in microgravity, its safety and efficacy is unpredictable because the heavy local anaesthetic solutions used depend on gravity. Epidural anaesthesia may be used, but it also requires considerable training and absolute asepsis, and therefore carries significant risks [16].

General anaesthesia with endotracheal intubation is suitable for all types of surgical conditions and is the recommended choice of anaesthetic technique.

Intubation, in general, is facilitated by use of general anaesthesia and muscle relaxants [16]. Furthermore, use of video laryngoscopy also increases the intubation success rate especially among new users [44, 45].

#### **5.2 Technical considerations**

#### *5.2.1 Fluid generation and handling*

Intravenous (IV) fluids have a limited shelf life and usually remain unused during that period. Shipping and storing them is expensive due to the added weight and the wastage of valuable storage volume. It is however expedient, and necessary to be able to generate IV fluids on demand using drinking water. This process was successfully tested on the ISS (project IVGEN) [16, 46].

Fluids and gases do not separate in space, owing to their different densities, which complicates fluid handling and drug preparation. Hence most drugs and intravenous fluids exist as a foamy liquid [16, 17].

It is advisable that injectable drugs be carried in prefilled syringes. Needleless vial adapters that allow direct drug aspiration into the syringe without the need for a needle to pierce the vial septum are also preferred. Experiments have been successfully conducted by NASA Scientific and Technical Information Program for removal of air bubbles [16, 17, 47].

Another important concern is that many medical devices such as anaesthetic vaporisers and suction equipment, that depend on gravity induced separation of fluids and gases, do not function properly in microgravity [17, 37].

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*Challenges to Airway Management in Space DOI: http://dx.doi.org/10.5772/intechopen.98932*

included in the ISS medical gear [16].

*5.2.3 Closed cabin atmospheres*

in such space operations [17].

*5.2.4 Medical equipment*

*5.2.5 Use of restraints*

capability [48, 49].

*5.2.6 Telemedicine and information technology*

During a medical emergency, vascular access may be difficult to obtain. In space,

securing the body of the IV administrator as well as mastering fine motor skills to perform the required task can be a challenge. Also, microgravity causes small objects to float away. Sharp objects such as IV cannulae can present a potential

Using ultrasound to obtain central venous access either autonomously or robotically is currently under development. An intraosseous access kit has also been

A spacecraft offers a tightly sealed environment. Medical procedures requiring the use of oxygen would risk oxygen enrichment in the closed cabin atmosphere, increasing the risk of explosion and fire. Use of a closed ventilation circuit limits the dumping of oxygen in the cabin. Volatile anaesthetics cannot be used in such an environment, as a gas leak can contaminate the on-board closed loop environment and therefore general anaesthesia must be provided by the technique of total intravenous anaesthesia (TIVA) [16, 17, 38]. Xenon may find utility as an anaesthetic gas

Advanced medical care requires equipment such as a monitor, ventilator, suction equipment, and oxygen concentrator. Equipment carried to space must comply with specific spaceflight standards. There are a number of stipulations in terms of weight, size, and power consumption. For perspective: It costs about US\$ 22,000 USD to transport one kilogramme of material into low Earth orbit. Drugs that do not need refrigeration and that which have a long shelf life are preferable, in this regard [16, 17].

Airway management is made possible during spaceflight using restraints, allowing the operator's hands to be free to hold and guide the endotracheal tube into the airway [38]. Use of restraints are absolutely necessary to hold instruments, patients and personnel in place. For surgical procedures, it has been demonstrated that it is possible to restrain instruments in microgravity using various supplies ensuring sterility, operator accessibility, safe waste disposal, while maintaining ergonomic

Telemedicine, as a medium for healthcare delivery, has tremendously improved and finds great many applications, in the current healthcare setting. Today, availing a virtual opinion, of an expert, at a remote location, is fairly uncomplicated. This becomes very useful during spaceflight operations. However, a delay of about 20 minutes to receive one way communication is to be expected during a journey to Mars [4]. Since anaesthetic procedures and airway management require prompt and expedient responses, telemedicine—with its inherent latency issues—may not prove to be the most optimal solution. Hence, other advanced on-board information

systems will need to supplement telemedicine technology in space [17].

*5.2.2 Vascular access*

hazard to the crew [47].
