Anesthesia

Excerpts from Counting Backwards – A Doctor’s Notes on Anesthesia by Henry Jay. This book caught my attention just to know more about this medical procedure which provides amnesia during invasive procedure on the body.

History
The inventions dates back to Jabir Ibn Hayyan, a resident of Persia in 8th century who nearly synthesized ether by combining Sulphur and alcohol. It still remains a speculation but he was a prolific author and said to have written some 3000 books and inspired a word ‘Gibberish’ (Geber being Latinized name of Jabir). In 1540, Valerus Cordus, a German physician combined fortified wine and sulphuric acid to form what he called oleum dulce vitriol – sweet oil of vitriol but was recognized for its anesthetic properties yet. Another 2 centuries later inhaling gases as a means of therapy flourished – by inhaling fumes of ether, this ether frolics provided relief and euphoria. In 1842, A Georgia doctor, Crawford Long brought ether frolics to his community and found during a fun party, some inhalants who got bruised never reported pain during its ‘subdued time’ and later one of his acquaintance sought his advice to remove a lump and as he dreaded pain, a novel idea was hatched and implemented, a towel saturated with ether was held under patients nose and asked to breathe and surgery was completed painless and safe. It went undocumented. On Oct 16,1846, Morton demonstrated publicly this method of inhaling gas for surgery and published a patent and called the procedure “Letheon” after river Lethe in Greek mythology which when its water drunk causes loss of memory. A month later, the term “Anesthesia” Greek for “without sensibility” was coined by Oliver Wendell Holmes (suggested via a letter) stuck and used now. Right now Sevoflurane is the choice of anesthetic gas compared to desflurane and isoflurane. Comes in variety of scents – bubblegum, cherry, strawberry or orange. 

Tools of the Trade
Anesthesia machine is CPU weighing many hundreds of pounds and stands about 5 ft high with 3 ft square base with 6 inch wheels anchored to a sturdy iron base. It has dials , switches and buttons to regulate gas flow and switch between modes of breathing. Plus a screen to monitor gas composition, rate and volume of breath. Also during anesthesia, patent’s airway needs to remain open and unobstructed that’s no snoring. Endotracheal tubes that help arrest snoring along with Laryngoscope which lights the path through the mouth to the vocal cords. IV anesthesia medications, narcotics for pain relief, relaxants for temporary paralysis (succinylcholine), Atropine/Epinephrine to speed up heart and antibiotics. Suction catheters to remove mouth secretions and a backup to the backup – the Ambu Bag – when squeezed, pushes a breath to a desperate patient in need – this is useful when gas flow or the electrical supply has failed and revert to manual mode.

Anesthesia and Its Adjuncts – The 5-As
The term anesthesia does encompass all goals of care, there are more adjuncts that are added to ether for full care and these side medicines create 5 effects called as 5-As of Anesthesia:

  • Anxiolysis, relieving stress created by an upcoming surgical procedure
  • Amnesia, preventing memory formation during anesthesia care
  • Analgesia, relieving pain during the procedure and after to include acute and chronic pain relief
  • Akinesia, preventing a patent’s movement during a procedure
  • Areflexia, stopping adrenaline surge and swings in blood pressure and heart rate while under anesthesia

Railroad Tracks
Anesthesiologists dream railroad tracks, no doubt, that’s what they want for a patient during their care. The rails are ticks and dots representing the patient’s blood pressure and heart rate as recorded during the progress of anesthetic care without variance. From “Your Patient is ready” – the comment made at that first painless surgery in 1846 and still used today – to “I’m finished” is to achieve the railroad tracks before handing over the patient to physician to take over.

Nothing by Mouth
First death due to anesthesia happened in 1848 the moment a patient inhaled the gas and an autopsy later revealed the patient’s lungs were found to be congested with blood and fluid. Possible caused could be heart related but also might be due to aspiration – stomach contents finds its way into wind pipe, trachea leading to “dry drowning”
The separate paths leading to the stomach and the lungs work on the either/or principle. Only one path may be open at a time, and eating and breathing are kept separate through a series of coordinated actions including muscles and reflexes. The vocal cords at the entrance to the trachea snap shut when food or drink enters the mouth. This reflex, the laryngeal adductor reflex, is beyond our active control and prevents any- thing in the mouth from going down the wrong pipe. To swallow, sphincters made of muscle in the esophagus relax and the contents of the mouth slide down into the stomach.
Gastroesophageal reflux—commonly referred to as GER D (for “gastroesophageal reflux disease”) and also known simply as heartburn—occurs when these sphincters fail and the stomach contents rise in reverse back up the esophagus. Silent aspiration results when the laryngeal adductor reflux fails. Food and drink entering the trachea can block the airway, preventing oxygen in the air from entering the bloodstream. Aspiration also pre- disposes a person to pneumonia.
Everyone experiences aspiration occasionally by accident. Either excited or impatient, we sometimes fill our mouths with too much food or drink, or too fast, or with a full mouth, and on a startle the contents go down the wrong pipe. Instead of passing down the esophagus into the stomach, the oral contents slide past the vocal cords and into the trachea, the windpipe. The system of protection that keeps the lungs clean and clear has failed. This is aspiration.
Acid is the anesthesiologist’s enemy. The stomach is capable of withstanding the acid it produces as an aid in digestion. But other tissue is not immune to this acid. Herein lies the risk of anesthesia, which relaxes muscles and turns off reflexes. The cinched esophageal sphincters relax, allowing the contents of the stomach to flow to the mouth while the laryngeal adductor reflex no longer guards the entrance to the trachea. To prevent aspiration under anesthesia, the stomach must be empty.
Nil per os. “Nothing by mouth.” The pre-anesthesia routine in decades gone by was to write and order: “NPO after midnight.” With first-scheduled cases in the morning, this worked fine. For afternoon cases, the patient might be left dehydrated. Today, a kinder, gentler sliding timescale is used, depending on the procedure schedule and the type of food or drink. Clear fluids are frequently allowed up to two hours before anesthesia; they don’t fill the stomach with acid and might actually aid in passing its contents out and along the intestines. Fatty foods produce the greatest amount of acid, requiring eight hours to clear acid from the stomach.

Amount of Anesthetic Agent
THE DOSE OF THE ANESTHESIA gas is measured as a percentage of the overall inhaled gases (as mixed with air and oxygen). The minimum alveolar concentration (MAC) is the percentage of gas inhaled that prevents fifty percent of patients from responding to a painful stimulus. Whether it’s a mouse, red-tailed hawk, monitor lizard, elephant, or human, regardless of species or size, the percentage of inhaled gas necessary to achieve the state of chemical coma is remarkably similar. Greater change exists with advancing age than between species: once you hit maturity, the older you are, the less gas you need. The same cannot be said for the anesthesia drugs administered by injection. Differences in species alter the IV (intravenous) or 1M (intramuscular) dose of the drugs necessary to provide anesthesia. More to the point, the required amount of drug increases as the level of oxygen consumed increases. Small species tend to consume oxygen in amounts that are magnitudes higher per pound or kilogram than the amounts that larger species consume and, as a result, anesthetizing small species requires larger doses of drug. The dose per pound of an anesthesia drug injected into a human might kill an elephant but leave a mouse unfazed and staring at you, wondering what just happened.

Pain Relief as a Right to be Sought
His call – paraphrased:
Most anesthesiologists had failed to understand or treat pain in non communicative patients. Those unable to speak for themselves had no advocates for comfort. Their families were either incapable of understanding them or, like most anesthesiologists, fearful of overmedicating. Hence, change from being a reactive analgesic administrator—depending on others beyond the patient to provide guidance for pain relief— to an activist, making pain relief as an important decision, with every intent to prevent as much moaning as possible. Instead of steering clear of overdosing, define its limits with greater precision.

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