by William Shin
Illustration: ‘Breathing’ by Leana King
Use of Anesthetics
Anesthetics have been used to eliminate the fear of pain during surgery since 1846.1 Nitrous oxide was the first anesthetic agent used and since that time, many different agents of anesthetics have been developed, such as propofol and lidocaine, to provide different forms of pain relief during surgeries. Different types of anesthetics include regional, local and general anesthetics, and these different anesthetics can be administered in various ways, including topically, by inhalation, and through injection.2
There are various types of anesthetics used and the type used varies based on the type of surgical procedure being done. Local anesthetics are usually administered through injections or topically. They are used to stop the sense of pain in a particular area of the body. Regional anesthetics are usually administered via an injection and are used when only a portion of the body will undergo a surgical procedure. General anesthetics are typically administered via inhalation or an intravenous line (a thin plastic tube inserted into the patient’s vein), and are used when the patient’s unconsciousness is vital in ensuring the patient’s safety during a surgical procedure. General anesthetics not only block the perception of pain throughout the body, but also place the patient’s brain in a state of unconsciousness. As a result of the severity of general anesthetics, post-procedural complications such as amnesia and delirium may occur.3 Post-surgery complications are not the only issue documented in literature; intraoperative complications (complications present during surgeries) have been documented as well, one of which is most famously known as “Anesthetic Awareness.”
Anesthetic Awareness and Its Different Flavors
Anesthetic awareness is when the anesthetics administered on the patient fail and the patient is conscious and susceptible to certain stimuli. Any sort of consciousness during one’s surgery is a scary thought. Even if the sensation is not necessarily pain, the sight of a surgical procedure being administered on you, the sound of drills and the feeling of sheer helplessness as you lie there, unable to move, are all nothing short of deeply traumatizing. There are different flavors of anesthetic awareness: auditory, visual, pain, and paralysis. Among those who experienced consciousness intraoperatively (during the operation), 85%-100% experienced auditory awareness, 27%-46% experienced visual awareness, 41% experienced pain and 60%-89% experienced the paralysis.4 By far, most patients who experience anesthetic awareness experience auditory consciousness and this is nothing short of expected. General anesthetics affect one’s ability to hear only indirectly and therefore, when consciousness is experienced, the first sense to be affected would be one’s sense of hearing.5 Feelings of helplessness, fear and the ability to remember details about the surgery are also prevalent in those who experience consciousness during their surgery. One study found that helplessness, characterized by panic and the fear of dying, has a prevalence of 46% among individuals who experienced consciousness during surgery, while fear in general and ability to recall details of the operation were present at 78%-92% and 64% respectively.3 The prevalence of anesthetic awareness varies based on the study and ranges from around 0.1% to 1%.3 Although the prevalence of anesthetic awareness has decreased by a factor of approximately ten since the 1970s,3 it is still present as a terribly frightening thought for those who are going into any surgical procedure.
There are several comorbidities/risk factors that play into increasing one’s chances of experiencing awareness. An important comorbidity is cardiovascular complications. First and foremost, it is important to understand that most cases of anesthetic awareness arise from overly light doses of anesthesia administered during surgery. Light anesthetics must be administered to protect those with especially sensitive cardiovascular systems, increasing the chances of “waking up” during surgery. Another risk factor that calls for overly light administration of anesthetics and thereby leads to awareness is drug dependency, specifically addiction to opioids. There is also evidence that identifies obesity as a possible risk factor for awareness. Obesity makes it difficult to estimate the pharmacokinetics (how the anesthetics will affect the patient) of the anesthetic. One study done in 2009, which surveyed 271 patients who experienced awareness, also showed that women, specifically younger women, had an increased likelihood of experiencing awareness.5 Children are also eight-to-ten fold more prone to experience awareness,3 the reason being that anesthetics are much more rapidly redistributed throughout children’s bodies. Outside of populations that may pose as risk factors are certain procedures themselves that increase risk for consciousness during operations. For example, during Cesarean sections, mothers are given low doses of anesthetics for fear that the baby may experience respiratory depression or anesthetic overloading if too much regional anesthetic is administered.
There are certain preventative measures taken to decrease the likelihood of experiencing anesthetic awareness. One is to maintain a quiet operating room and/or place headphones on the ears of the patient during the operation.3 This would help prevent auditory awareness. However, the recording being played in the headphones is also extremely important because certain words can trigger a particular perception and may cause the headphones to be deleterious rather than helpful. For example, the word “pain” should not be within the message, even when the overall message is “you do not feel pain.” The negative connotations associated with the word “pain” may overwhelm the meaning of the entire message.
Another preventative measure is to administer benzodiazepines. Administering benzodiazepines does not necessarily ensure that anesthetic awareness will not occur; however, failure to administer benzodiazepines significantly increases the risk of awareness.3 Avoiding the use of muscle relaxants whenever possible is also a way to decrease the likelihood of being “awake” during surgery. Studies have shown that muscle relaxants almost double the rate of anesthetic awareness from 0.1% to 0.18%.7 This does pose to be a difficult solution, however, because using muscle relaxants is, more often than not, unavoidable when under general anesthesia since these relaxants are the only method by which movements, reflexes and defensive tension can be prevented.
Intraoperative awareness can lead to postoperative sequelae (conditions resulting from previous conditions) and the duration of each complication exists in different amounts depending on the individual. Studies have reported that within populations who experienced anesthetic awareness, sleep problems were prominent. It was reported that 19% experienced any type of sleep disturbance and 21% experienced nightmares.6 In the same study, it was reported that psychological symptoms might also present themselves post-operation, most prominently in the form of PTSD. It was reported that 22% succumbed to PTSD with other studies reporting even higher incidence rates at 33%.7 Intraoperative consciousness of any sort can be extremely traumatizing. There is a certain degree of helplessness felt when one is able to perceive certain stimuli and yet is physically unable to react. It is this precise feeling of helplessness while being conscious during your own surgery that makes anesthetic awareness so traumatic. Although the prevalence of anesthetic awareness is relatively low, it is important to conduct further research into better preventative measures so that patients do not have to experience anesthetic awareness and be subject to sleep disruptions and PTSD.
1. Robinson DH, Toledo AH. Historical Development of Modern Anesthesia. Journal of Investigative Surgery. 2012; 25(3): 141-149. https://www.ncbi.nlm.nih.gov/pubmed/22583009. Accessed October 5 2016.
2. Types of Anesthetics and Your Anesthesiologist. Johns Hopkins Medicine Web site. http://www.hopkinsmedicine.org/healthlibrary/conditions/surgical_care/types_of_anesthesia_and_your_anesthesiologist_85,P01391. Accessed October 5 2016.
3. Saniova B, Drobn M, Sulaj M. Delirium and postoperative cognitive dysfunction after general anesthesia. Medical Science Monitor. 15(5): CS81-7. https://www.ncbi.nlm.nih.gov/pubmed/19396043. Accessed October 18, 2016.
4. Bischoff P, Rundshagen I. Awareness during general anesthesia. Deutsches Ärzteblatt International. 2011; 108(1): 1-7. http://www.aerzteblatt.de/pdf/DI/108/1/m1.pdf. Accessed October 5, 2016.
5. Chaiwat O, Vacharaksa K, Prakanrattana U. Awareness under general anesthesia. Journal of the Medical Association of Thailand. 2002; 85(3): S948-55. https://iths.pure.elsevier.com/en/publications/awareness-under-general-anesthesia. Accessed October 5, 2016.
6. Ghonelm MM. et al. Awareness during anesthesia: risk factors, causes and sequelae: a review of reported cases in the literature. Anesthesia & Analgesia. 2009; 108(2): 527-535. https://www.ncbi.nlm.nih.gov/pubmed/19151283. Accessed October 5, 2016.
7. Sandin RH. et al. Awareness during anesthesia: a prospective case study. Lancet. 2000; 355(9205); 707-711. https://www.ncbi.nlm.nih.gov/pubmed/10703802. Accessed October 18, 2016.