Lawrence J. Saidman

Alveolar oxygen and carbon dioxide concentrations during simulated breathing through a T-piece. Effect of breathing pattern, fresh gas flow, and reservoir volume.

Using a model to simulate a patient breathing spontaneously through a T-piece from a Puritan nebulizer delivering 44, 74 or 100% oxygen, we evaluated the effects of oxygen flow, ventilatory pattern, and open-ended reservoir (“tail-piece”) volume, on FAO2 and FACO2.The FAO2 approaches Fio2. with higher oxygen flows into the nebulizer, lower tidal volumes, lower respiratory flow rates, or larger reservoirs. However, with shallow rapid respiration a greater reservoir volume increases FACO2 as well. Most importantly, when the nebulizer setting is changed from 40 to 70% or from 70 to 100%, only a negligible increase in FAO2 is achieved at an oxygen flow of 5 L/min without the use of a reservoir. We conclude that the T-piece is most safely used with a Puritan nebulizer when the oxygen flow is set at 14L/min (Flush), and the reservoir volume is at least 200 ml.

1910–1950: Anesthesia Before, During, and After Two World Wars

A renaissance in anesthesia, particularly in the US and GB, occurred between 1910 and 1950. World War I drew physicians into anesthesia and forced some technical improvements such as the Boyles anesthetic machine and a use of blood transfusions. Guedel developed his technique for defining depth of anesthesia. As the numbers of anesthetists grew in the US, two societies arose: the American Society of Anesthesiologists and the International Anesthesia Research Society, and in Great Britain the Association of Anaesthetists of Great Britain and Ireland. Academic departments developed at the University of Wisconsin (Waters chair); Harvard (Beecher) and Oxford (Macintosh). In combination, the societies and academic departments increased recognition of the role of the anesthetist and improved quality through education and examination for certification/credentialing. Similar developments occurred in the rest of the world in subsequent years.

1860–1910: The Specialty of Anesthesia Develops Slowly

The discovery of anesthesia ultimately enabled remarkable advances in surgical care, but did not immediately change operations. At first, surgeons still pulled teeth, managed injuries, amputated limbs, and performed brief operations requiring momentary but deep levels of anesthesia. So the anesthetist drove the level of anesthesia down and then allowed it to “bounce” up, the surgeon operating at deeper levels of anesthesia. Further advances required improvements.

Significant Developments in the 1990s

The 1990s advanced safety, control and understanding of clinical anesthesia. Two new, poorly soluble inhaled anesthetics, sevoflurane and desflurane allowed a more precise control over the anesthetic state. Sevoflurane did so without cardiorespiratory stimulation. Both protected the heart from hypoxia. An older anesthetic, isoflurane, could reverse mental depression. We learned that all these anesthetics acted on central pattern generators in the ventral spinal cord to make patients immobile despite ongoing surgery. We also learned that the Meyer-Overton theory correlating lipophilicity and anesthetic potency didn’t always work, indirectly suggesting that inhaled anesthetics operated on proteins. Two new muscle relaxants, recuronium and cis-atracurium added to safety by acting more rapidly and for shorter times.

History to 1798

Surgeons in ancient times undertook diverse operations, usually at great speed to diminish the duration of suffering. Skulls from 5,000 BCE show trephination, the removal of a piece of bone from the head. Egyptians in 3,600 BCE performed circumcisions and tracheotomies. In 1700 BCE, Babylonians excised tumors. Egyptians cauterized breast tumors and excised peripheral aneurysms. The Roman surgeon, Galen, in the second Century CE, treated cataracts to restore sight, and he cut out the uvula to cure chronic coughing. Surgeons in Europe might be physicians, monks or barbers who in the thirteenth and fourteenth centuries wrote books on surgery. They gained recognition by their study of the anatomy of cadavers. Thus, in 1543 Vesalius published “On the Fabric of the Human Body”, demolishing centuries of errors, and opening the door to the performance of accurate surgery.

1844–1846: The Discovery and Demonstration of Anesthesia

Gardner Colton, a Columbia University medical student, began the discovery of anesthesia by offering (for pay) a public entertainment, a demonstration of the intoxicating effect of nitrous oxide. The dentist Horace Wells attended a demonstration in Hartford, observing that while inebriated, Samuel Cooley injured himself, apparently not feeling the injury as it occurred. Seeking a means to practice painless dentistry, Wells asked Colton to attend his office the next day, and to administer nitrous oxide to Wells while an associate, John Riggs, pulled one of Wells’ teeth. Wells felt no pain, and then gave nitrous oxide to several of his patients, practicing painless dentistry on most of them. His success prompted him to approach the great surgeon Warren at the Massachusetts General Hospital (MGH), requesting that he allow Wells to attempt a public demonstration at the Harvard Medical School. The demonstration failed, the audience denouncing Wells for his “humbug.”

1846–1860: Following the Discovery of Anesthesia

Four things soon followed the discovery of ether anesthesia. First, within weeks to months, ether was used in distant and disparate parts of the world’Europe, Australia, Mexico and Latin America. Second, for the moment, nitrous oxide was abandoned. Third, in 1847 Simpson discovered the anesthetic properties of chloroform that, for a time, replaced the pungent, flammable ether, especially in the UK. Fourth, the discovery of anesthesia was one thing, but how to deliver it safely was another. We needed a guidebook, a description of the clinical characteristics of anesthesia that might allow control of the anesthetic state. In 1847, Snow supplied just that for ether. In 1858, he similarly described the degrees of chloroform anesthesia, in the process analyzing the dangers of this more dangerous anesthetic and teaching how to avoid disaster. He, more than anyone, laid the groundwork for the specialty we call anesthesiology.

History Reflected in the Evolving Approaches to Anesthesia for a Patient Undergoing Cholecystectomy

The evolving nature of modern anesthesia shows the progression of drugs used (inhaled anesthetics, induction agents, anxiolytics, opioids, neuromuscular blocking drugs), the means of their delivery (for both injected and inhaled agents), approaches to anesthetic and surgical practice (in patient vs. out patient; long stay vs. short stay), control over the anesthetic state and postoperative pain, and means to manage the airway and postoperative nausea and vomiting. They hint at the evolution of patient, surgeon, and anesthetist and the interactions among the three. But beyond surface appearances, they do not show the profound changes wrought in the quality and education of the anesthetist and surgeon, the improvement in outcomes, the amazing decreases in mortality and morbidity. They do not consider the implications of those changes to the future of the specialty.

Major Anesthesia-Related Events in the 2000s and Beyond

The dramatic scientific and technologic advances of anesthesia in preceding decades slowed in the 2000s, with maturation of the specialty and associated subspecialties. Certificates attesting expertise in anesthesiology and subspecialities now require or will require recertification. Except for sugammadex, no new anesthesia-related drugs were released for use, and few new drugs are on the horizon. New uses for old drugs were found such as administering ketamine to lessen postoperative dependence on opioids, and substituting intrathecal 2-chloroprocaine for lidocaine to avoid lidocaine-associated transient neurologic syndrome. The 2000s saw technical advances such as the GlideScope, the first of many video-laryngoscopes, and increased adoption of ultrasound-assisted regional anesthesia. Several societies recommended ultrasound guidance for insertion of central venous catheters.

Major Anesthetic Themes in the 1950s

Increasing anesthesiologist numbers and diversity in the 1970s led to subspecialty societies and journals. Women constituted a rising fraction of anesthesiolgists. The practice of anesthesia became more diverse with an expanding application of outpatient surgery, establishment of regional anesthesia in everyday practice, and a rising use of anesthesia outside the operating room. Our understanding of anesthetic drugs and how to best use them changed. In the US, and to a lesser extent elsewhere, the minimally hepatotoxic enflurane replaced halothane. We explored neuromuscular pharmacokinetics and clinically defined recovery from neuromuscular blockade. Dantrolene treatment of malignant hyperthermia was initiated. We incorrectly thought we might understand how inhaled anesthetics acted. We found opioid receptors in the spinal cord, leading to intrathecal opioid administration to provide analgesia. Patients received opioid analgesia on demand.