Abstract
The choice of the anesthetic technique in austere environments is dictated by the availability of medical personnel, electricity, oxygen, and supplies. TIVA appears to be a very promising, reliable alternative for the future of field anesthesia given its safety, simplicity, rapid setup, and small logistical footprint. Therefore, more anesthesia providers need to be trained and educated to be familiar and comfortable with administration of TIVA. Whenever regional nerve block anesthesia use is appropriate, it can be another excellent choice to provide better acute pain control and decrease postoperative complications in austere environments. There is no perfect analgesic, and hence multimodal approach for pain management is imperative. Early pain treatment has been proven to decrease chronicity, improve functionality, and reduce the risk of subsequent development psychological morbidities such as PTSD and depression. The chapter lists the recommendations on prevention and management of the consequences of sexual violence, reduction of HIV transmission, prevention of excess maternal and neonatal mortality and morbidity, and planning of comprehensive reproductive health services in the early days and weeks of an emergency.
Introduction
Anesthesiologists play a pivotal role controlling airways, performing resuscitation and providing anesthesia and analgesia, not only in the ORs with relatively controlled settings but sometimes also extending to practicing in austere environments or field conditions where care has to be provided on site[1]. Anesthesia delivery in below-standard conditions with limited resources is indeed challenging[2]. Field hospitals are usually established when natural disasters (earthquakes, hurricanes, and floods, and so on) occur or in the battlefields during wars[3,4,5]. Such events result in mass casualties as well as hospital damage and local infrastructure insults, compromising electricity, transport, and supply chains.
In the aftermath of natural disasters, local hospitals may need to be evacuated into temporary field hospitals due to building collapse or imminent collapse. Later on, main field hospitals are established and they usually start running within days. Foreign medical providers historically volunteer for humanitarian missions to help local medical staff to establish and operate field hospitals, as in the major earthquakes that occurred in Armenia (1988), Japan (1995), Pakistan (2003), China (2008), and Haiti (2010).
The medical system of the USA military provides five levels of care, between which patients are transferred. Level I occurs at the battlefield aid station, focusing mainly on providing advanced trauma life support, stopping blood loss, and evacuating the wounded soldiers. Level II occurs in main field hospitals near the frontline, in which surgical interventions are conducted. Level III facilities are known as combat evacuation or support hospitals, where more surgical subspecialties are available. The level IV service is being served at facilities located in USA allied countries, in which evacuated soldiers are evaluated and treated. Lastly, level V are hospitals in the USA, where soldiers are transferred to be treated depending on their wounds, screened for post-traumatic stress disorder (PTSD), and treated for any chronic pain they might be experiencing.
Most disaster or combat casualties present with acute traumatic injuries, in the form of lacerations, bone fractures, gunshot wounds, and injury to brain, spinal cord, and other organs requiring urgent surgical intervention. The predominant injury pattern reported in the literature involves a high incidence of limb injuries. Consequently, operations for traumatic limb injuries and for penetrating trauma rank among the most common interventions in austere environments, while endoscopic and cardiac procedures are rare and infrequently performed.
The field environment is often associated with limited medical supplies, equipment, and space, as well as shortage of electricity, oxygen, and trained personnel. Therefore, a combination of problems, anticipation, proper planning, and coping with difficult situations is required for a successful anesthesia care model. The number of patients in need often overwhelms the capacity. Thus, the key role is selection and triage. The surgeon has to identify and prioritize eligible patients and choose the adequate procedure that results in the desired outcome without unnecessary draining of resources or personnel. The anesthesiologist must develop an anesthetic plan and choose a modality that allows for effective anesthesia and analgesia, while avoiding unnecessary risks to the patient. The goal is to attempt to provide the safest anesthetic possible for surgeries to be performed, despite the constraints and limitations of technical equipment and supplies.
Anesthesia Options and Considerations
Many advances have been made in anesthesia delivery at the time of wars and disasters, from using ether, chloroform, thiopental, and halothane, to the more modern drugs and agents being used nowadays. Choosing the right anesthesia management type or modality is of paramount importance. Multiple anesthetic techniques have been successfully used in field hospitals, from monitored anesthesia care (MAC) to general anesthesia. Anesthetic management in this special population is not an easy task as most patients suffer from intravascular volume depletion secondary to bleeding and dehydration, electrolyte derangements, coagulopathies, and/or sepsis. Therefore, maintaining hemodynamic stability is imperative.
The various limitations in an austere environment always favor the utilization of compact, lighter weighted, reusable, and easily mobile items. Given the constricted availability and interruptions of supplies, the required anesthetic system should ideally be simple to operate, able to withstand extreme conditions, and rely minimally on electrical supplies and compressed gases.
General Anesthesia
General anesthesia is used in many cases and can be provided parenterally, via inhalation, or a balanced combination of both.
Inhalation Anesthesia
In general, mechanical ventilators have limited portability, and their use requires the availability of electricity, compressed gas, suction, and scavenging systems, which all add to the constraints of its utility in postdisaster scenarios. In response to these limitations, manual ventilation is frequently used, especially during the early phases of surgical interventions. Many devices have been developed along the continuous search for a durable, dependable, and portable system, which can minimize the logistical footprint. In military fields, the draw-over anesthesia system, Ohmeda Universal Portable Anesthesia Complete (UPAC), has been one of the most reliable devices for inhalation anesthetics since the 1970s[6]. The UPAC does not require power or gas flow for operation. It is designed to deliver volatile inhalation agents to spontaneously breathing patients using their inspiratory efforts to draw ambient air through the vaporizer, but it can be used with a portable ventilator, such as the lightweight, battery-powered Impact Uni-Vent 754 Eagle, and supplemental oxygen can be added if necessary. Despite being a dependable device, it is very difficult to find replacement parts as the UPAC is no longer being manufactured. Other examples of draw-over anesthetic vaporizers used in austere conditions include the Oxford Miniature Vaporizer, the Diamedica Draw-over Vaporizer, and the vaporizer of the Universal Anesthesia Machine. Military forces are now increasingly using conventional compact anesthesia machines, such as Dräger Fabius Tiro M, Narkomed M, and others, which are more sophisticated, a lot heavier than draw-over devices, and require electrical power for operation. The need for oxygen supply adds to the logistical burden[7]. Compressed gas cylinders are heavy to be ported from one place to another, require refill or replacement, and carry some explosive hazards. Consequently, portable oxygen generators that can be used to fill oxygen cylinders and concentrators that can generate oxygen via room air concentration were developed. Many oxygen concentrators, such as Saros, Eclipse, and DeVilbiss, are able to provide uninterrupted supply of oxygen in harsh environments. However, with all the progress and advancements in anesthesia delivery over the years, inhalation anesthesia is still considered a challenge in an austere environment[8].
Total Intravenous Anesthesia
Total intravenous anesthesia (TIVA) is becoming a more desirable method for the induction and maintenance of general anesthesia in deployed settings[9]. It can be used to provide sedation, amnesia, analgesia, and akinesia without the use of volatile anesthetic gases. Its small logistical footprint and the lack of need for bulky anesthesia machines, sophisticated vaporizers, heavy equipment, or power supply make TIVA preferable over inhalation anesthesia on the battlefield, where space, electricity, and resupply are potential issues. The main limitation of TIVA is that its administration requires anesthesia providers who are familiar with TIVA. In addition, existence of an adequate intravenous access is mandatory.
TIVA provides more hemodynamic stability, does not trigger malignant hyperthermia, decreases the incidence of nausea and vomiting, and carries less waste-disposal burden compared to volatile gas anesthetics. Other advantages of the total intravenous technique include easy titration due to predictable pharmacokinetics and dynamics, and reduction of recovery time. Many induction agents, such as propofol and etomidate, can be bolused or continuously infused through pumps to maintain anesthesia. Benzodiazepines, narcotics, and muscle relaxants are often used as adjuncts in intravenous anesthesia. The ability to maintain patients on the same intravenous agents without interruption allows easier en route control during patient transport. A popular infusion recipe is the mix of propofol and ketamine. This admixture (ketofol) results in relevant reduction in postoperative nausea, vomiting, and pain compared to inhalation anesthesia. The high-quality emergence and decreased recovery are also among the most documented benefits of TIVA. All these previously stated desirable qualities lead to fewer postoperative interventions, reduced cost, and lowered workload on medical personnel, thus making TIVA a very reliable technique in an austere environment.
Ketamine
Ketamine is one of the most unique agents used in TIVA or MAC. It is a noncompetitive antagonist of the N-methyl-D-aspartate receptor, with rapid onset and short half-life that can provide analgesia, amnesia, and hypnosis while maintaining hemodynamics, airway reflexes, and spontaneous ventilation. The increase in heart rate and blood pressure caused by ketamine can be beneficial in hypotensive patients and can also be neuroprotective by improving cerebral perfusion. It helps in temperature conservation by causing peripheral vasoconstriction. In addition to potentiating the effects of opioids, ketamine can provide significant pain relief itself and therefore spares narcotic use and decreases the potential risk of opioid-induced hypotension and respiratory depression, which can be lethal in polytrauma patients. Its use can have some potential side effects, which providers need to be aware of, particularly with higher doses, such as the tendency for causing excessive salivation, and psychotomimetic effects like hallucinations and nightmares. Ketamine is traditionally believed to cause a possible increase in intracranial cerebrospinal fluid pressure and intraocular pressure. Therefore, despite conflicting evidence, ketamine should be used with extreme caution in patients with traumatic brain and eye injuries. Ketamine can be administered orally, intramuscularly, or intravenously, either as a sole agent or in combination with other medications, especially when ventilators are unavailable. It can also be used in supplementation of regional anesthesia in some cases. Ketamine MAC is well tolerated in general, with a low rate of complications or adverse events, making it a very useful drug in the field environment[10].
Related posts:
Chapter 6 – Training and Accreditation
Chapter 3 – Definitions, Needs, Scenarios, Functional Concept, and Modes of Deployment
Chapter 11 – Auxiliary Medical Services in a Field Hospital
Chapter 7 – Personnel
Chapter 17 – Wound Management in a Field Hospital Environment
Chapter 25 – Infectious Diseases and Public Health in a Field Hospital
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