A Century of Technology in Anesthesia & Analgesia

Abstract

Technological innovation has been closely intertwined with the growth of modern anesthesiology as a medical and scientific discipline. Anesthesia & Analgesia, the longest-running physician anesthesiology journal in the world, has documented key technological developments in the specialty over the past 100 years. What began as a focus on the fundamental tools needed for effective anesthetic delivery has evolved over the century into an increasing emphasis on automation, portability, and machine intelligence to improve the quality, safety, and efficiency of patient care.

“In operating rooms of the future technical equipment probably will include a device by means of which the pulse may be counted with the aid of electronics and a beam of light may be projected on a scale on the operating room wall, so that any interested person in the room can immediately see exactly what the pulse rate is. The same means can be used for showing the blood pressure and also the degree of anoxemia or need for oxygen. A permanent record could even be made. At the moment, the proposal sounds complicated, but if the method were once in use, it would soon become part of everyday life and the anesthesiologist and surgeon would wonder how they got along without it.”

– John S. Lundy, MD. Factors that influenced the development of anesthesiology. Anesth Analg. 1946;25(1):38–43.

Introduction

The evolution of medicine in general and of anesthesiology in particular has been linked to the evolution of technology. The three stages of technological evolution, as defined by scholars Rodovan Richta and Masse Bloomfield, provide a helpful framework for understanding the development of technology in anesthesiology.^1,2 The first stage is “The Tool,” which gives the human user a mechanical advantage in executing a specific physical task. In anesthesiology, laryngoscopes, endotracheal tubes, and oral airways are just a few examples of tools. The second stage of technological development is “The Machine”—a tool that no longer requires human power but still relies on human control. Machines, prevalent since the Industrial Revolution, allow us to transcend the limitations of the human body. In anesthesiology, prime examples of machines are infusion pumps and anesthesia workstations. The third and final stage of Richta and Bloomfield’s classification is “Automation,” which is defined as a machine that substitutes human control with an automatic algorithm that is often a computer control system. In clinical anesthetic practice, full automation is still rare and only starting to be developed. However, many of our machines are effectively automated. Modern ventilators, for example, rely on minimal input from the physician, managing specific breath-to-breath actions on their own.³

Over the past century, Anesthesia & Analgesia, more than any other journal, has captured the evolution of technology in anesthesiology and perioperative medicine. This article will describe this development and highlight specific technological contributions made by the global anesthesia community since 1922. It will also describe the work of members of the Society for Technology in Anesthesia (STA) during the first two decades of the 21^st century.

Background

Since the early days, a symbiotic relationship between anesthesiologists, researchers, and manufacturers has been a powerful force in developing anesthesiology as a medical and scientific specialty. Many early physician anesthetists were tinkerers and innovators who relied on their relationship with manufacturers to produce new equipment or pharmaceuticals. In the United States, this triumvirate of clinicians, scientists, and industry representatives in fact catalyzed the formation of the largest organization that has been exclusively devoted to the research and educational aims of the specialty.

Founded in Cleveland, Ohio, in 1919, the National Anesthesia Research Society (NARS), the precursor to the International Anesthesia Research Society (IARS), had on its Board of Governors and Research Committee several prominent scientists, manufacturers, and practitioners of anesthesia (i.e. physicians and dentists, but not nurses).⁴ The first President of the NARS was Elmer McKesson, MD, physician anesthetist and inventor extraordinaire, who had designed his first anesthetic gas delivery apparatus and founded the McKesson Appliance Company a few years out from medical school.⁵ He also created the first uniform anesthesia record in the United States.⁶ The NARS was the brainchild of the charismatic Francis McMechan, MD, who served as the organization’s Executive Secretary, Research Committee Chair, and Editor of its official publication, Current Researches in Anesthesia and Analgesia (1922).^4,7

The main goal of the NARS was to promote and to exchange accurate and detailed clinical and research findings on anesthetic principles and practice.⁸ As stated in the society’s tenth and final objective, the NARS’ overarching mission was “[t]o use its influence in every possible way and to give its aid toward the advancement of the science, practice and teaching of anaesthesia.”⁸ The scientific aims of the NARS distinguished it from political societies of the day like the Association of American Anesthetists (AAA) and the New York Society of Anesthetists (NYSA), the precursor to the American Society of Anesthetists (ASA).⁹

When the NARS grew in size and stature and adopted more international members, it changed its name to the International Anesthesia Research Society (IARS) in 1925.^4,7 At the time, the IARS chose to restrict membership to clinicians and researchers but still retained close ties with manufacturers. With the name change, the IARS now became the official sponsor of Current Researches in Anesthesia and Analgesia.

1920s and 1930s: Tools for a Developing Profession

Under the direction of the talented and visionary Dr. Francis McMechan, Current Researches in Anesthesia and Analgesia enjoyed two glorious decades as the sole physician anesthesia journal in the United States. Thus, the journal reflected the salient scientific and professional issues that affected the physician anesthesia community at the time.¹⁰

Physician anesthetists in 1920s and 30s were still in the formative stages of professionalization.⁹ San Francisco-based Mary Botsford, MD, presciently surmised in her Presidential Address at the annual Congress of Anesthetists in 1931: “A perfectly safe, efficient and possibly automatic anesthetic may be a future discovery and a medical robot will perhaps be capable of its administration,” she said. “In the meantime,” she continued, “the crying need for better anesthesia resolves itself into a need for better anesthetists.”¹¹ Dr. Botsford’s view of the future was surprisingly clairvoyant. She augured the future while also highlighting the main focus of physician anesthetists of the day—developing the foundational knowledge and techniques needed for safe and effective anesthetic delivery.

At the same time, technology was needed to accomplish this end. The primary technological themes that emerged in Current Researches in Anesthesia and Analgesia in the 1920s and 1930s were: 1) the invention of fundamental tools to facilitate anesthetic delivery and patient safety, 2) the growing use of monitoring devices (i.e. the sphygmomanometer and electrocardiogram) for physiological assessment, 3) a preliminary recognition of the need for standardization of anesthesia equipment, 4) methods to mitigate explosion risk during the era of flammable anesthetics (i.e. ether, ethylene, cyclopropane) (Table 1).

Table 1:

Technology in Anesthesia & Analgesia: Major Themes in the Past Century

Time Period	Themes
1922–1939	Invention of fundamental tools to facilitate anesthetic delivery and patient safety Growing use of monitoring devices (i.e. the sphygmomanometer and electrocardiogram) for physiological assessment A preliminary recognition of the need for standardization of anesthesia equipment Methods to mitigate explosion risk during the era of flammable anesthetics (i.e. ether, ethylene, cyclopropane)
1940–1959	Continued refinement of tools for inhalational, regional, and intravenous anesthetic delivery Birth of continuous electrocardiography (ECG) and electroencephalography (EEG) Eventual use of electricity for external cardiac defibrillation Early twitch monitoring to assess degree of neuromuscular blockade Origins of technological improvement and standardization on a systemic scale
1960–1979	Continued introduction of new tools and machines for safer and more efficient anesthetic delivery Rapid development of new monitoring and measuring devices with increasing portability and automation Proliferation of research on the physiological effects of various anesthetic agents Technology’s role in facilitating effective resuscitation and treatment measures Early use of computers for scheduling, knowledge sharing, and data processing
1980–1999	Continued refinement of tools and machines for anesthetic delivery and airway management Consolidation of the foundational monitoring devices in anesthesia (i.e. pulse oximeter and capnograph) Use of computer processing to develop simulation for crisis management, to improve health system efficiency, and to conduct large-scale outcomes trials
2000–2022	Development of advanced physiological monitoring systems The electronic health record Use of clinical research methodologies to evaluate technological impact on patient outcomes Applications of computer science, robotics, and control engineering to the perioperative environment Promotion of patient safety and cybersecurity through coordination between devices (device interoperability) and health informatics systems

At first, the devices featured in Current Researches in Anesthesia and Analgesia mainly took the form of handmade or manufactured tools that improved anesthetic delivery. In the 1920s, most physician anesthetists were only beginning to experiment with endotracheal intubation.^12,13 While ether was still mainly given by the “open-drop” technique, anesthetics like nitrous oxide or ethylene were administered with oxygen by gas delivery machines connected to face masks. Thus, newer gas machines and masks were often devised to optimize anesthetic delivery.^14,15

The most impactful article from this era was likely “A New Intratracheal Catheter” (1928).¹³ Written by anesthesia giants Ralph Waters, MD, and Arthur Guedel, MD, it celebrated the ability of a new cuffed endotracheal tube to keep a dog alive underwater after anesthetic induction with ethylene. Soon, Dr. Waters would use this innovation to pioneer single-bronchial intubation and lung isolation during thoracic surgery.¹⁶

The cuffed endotracheal tube prevented aspiration and facilitated leak-free ventilation. Before its popularization, creative ways to pack the posterior pharynx with accessory gauze, sponges, bulbs, or cuffs had been devised.¹⁷ However, given the high risk of laryngospasm associated with intubating the trachea during the pre-curare era, Canadian anesthesiologist Beverley Leech, MD, invented the supraglottic “Pharyngeal Bulb Gasway” to enable air-tight gas delivery without an endotracheal tube.¹⁸ Featuring a core metal airway surrounded by a soft rubber bulb that would mold to the pharynx, the Leech Airway was an early precursor to the modern laryngeal mask airway (LMA). By the 1930s, closed-circuit systems with carbon-dioxide absorbers—Dr. Waters’ to-and-fro soda lime canister and Brian Sword, MD’s circle system (1930)—also allowed for rebreathing of gases in the setting of leak-free ventilation.¹⁹

For spinal anesthesia, needles of varying material—steel, platinum, gold—were used,²⁰ and tools like George Pitkin’s “tiltometer” measured the patient’s reclining angle to adjust the level of blockade.²¹ Epidural needles only began to appear in Current Researches in Anesthesia and Analgesia in the late 1930s, after a Brazilian anesthetist reported success with the Dogliotti loss-of-resistance technique for several gynecological procedures.²²

The 1930s also saw the birth of modern intravenous (IV) anesthesia in Germany with the development of the barbiturates Evipan and Pentothal.^23,24 The initial tool of choice for IV anesthetic delivery was a simple venipuncture needle through which intermittent boluses could be given. The physician anesthetist would keep a close eye on the patient throughout the surgery, and an assistant would often help lift the patient’s chin in cases of airway obstruction.

In the 1920s and 30s, evaluation of patients still relied primarily on physical examination. The physician anesthetist determined anesthetic depth by observing the patient for Guedel’s “eye signs,” cough and gag reflexes, and increasing degrees of muscle relaxation (pre-curare).²⁵ For preoperative cardiac evaluation, basic auscultation of heart sounds and palpation of the pulse were prioritized. Some physicians used a “breath holding test” to determine cardiorespiratory reserve; some calculated indices of operative risk based on systolic and diastolic blood pressure readings. Pulmonary assessment consisted of lung auscultation and frequent examination of the patient for signs of airway obstruction or cyanosis.

However, these early decades also saw a growing use monitoring tools to promote patient safety and to assess preoperative risk. Frequent measurement of intraoperative blood pressure by using a sphygmomanometer and listening for Korotkoff sounds slowly gained acceptance in anesthetic practice as an aid to diagnosing, preventing, and treating shock.²⁶ While the electrocardiogram (ECG) had yet to enter routine practice, it began to be used with increasing frequency for preoperative evaluation or for research studies.^27,28

Early articles in Current Researches in Anesthesia and Analgesia often conveyed individual anesthetists’ delight in the process of discovery—the joy of installing a bag-pressure gauge to prevent lung overdistention during ventilation,²⁹ the amazement at reviving a patient in cardiac arrest by delivering an electrical shock through a needle that pierced the ventricle.³⁰ But in general, the technology and techniques of anesthetic administration were incredibly varied. In 1931, Australian anaesthetist Geoffrey Kaye, MD, called for the standardization of gas equipment, as machines as different as the Heidbrink, McKesson, Walton, Boyle, Shipway, Magill, Schmidt-Sudeck-Draeger, Metric, and Safety, were used around the world.^31,32

In the era before nonflammable halogenated hydrocarbon anesthetics, methods to mitigate fire risk were also a publication focus. The main techniques proposed were rebreathing and grounding systems to protect everyone in the operating room.^33,34 As early as the 1930s, some researchers recognized the potential value of halogenated hydrocarbon anesthetics given their potency and non-explosivity—18 different agents were tested on laboratory mice in a preliminary study.³⁵

A remarkable invention that enabled continuous monitoring and recording of pulse rate and respirations was published in the journal in late 1939 and served as a harbinger of things to come. William Neff, MD, future Chair of Anesthesia at Stanford University, built this device from a polygraph, or lie detector.³⁶ Based on the premise that intercostal muscle paralysis was a reliable sign of deep surgical anesthesia, sensors placed on the patient’s chest and abdomen were connected to pens that recorded the pattern of thoracic and abdominal respirations. As the anesthesia was deepened, the amplitude of the thoracic breathing waveforms declined, while those of the abdomen increased.³⁶ Another pen could be activated by the blood pressure cuff to record the patient’s pulse. Half a year later, Dr. Neff added to this device a continuous blood pressure recorder that relied on an optical-electrical mechanism to activate a sphygomanometer.³⁷

1940s and 1950s: New Machines and Continuous Monitoring

In the 1940s and 1950s, there was an influx into the specialty of new physician anesthetists who had first administered anesthesia during World War II. During this period of growth, the journal highlighted several key technological themes: 1) the continued refinement of tools for inhalational, regional, and intravenous anesthetic delivery, 2) the birth of continuous monitoring of electrical signals from the heart and the brain, 3) the eventual use of electricity for external cardiac defibrillation, 4) early glimmers of twitch monitoring to assess the degree of neuromuscular blockade, 5) the origins of technological improvement and standardization on a systemic scale.

As evidenced by numerous papers in Current Researches in Anesthesia and Analgesia, anesthesiologists of the 1940s and 50s continued to modify every aspect of the technical delivery of inhalational anesthetics. New laryngoscope blades and handles,^38,39 modified endotracheal tubes,^40,41 bronchial blockers,⁴² and improved adapters and valves were made.^43,44 While powerful positive-pressure ventilators had yet to be conceived, the inadequacy of negative-pressure iron lungs used during the Danish poliomyelitis epidemic of 1952–53 sparked a new interest in developing mechanical ventilators.^45,46

Modern anesthetic vaporizers were a technological marvel. Sir Robert Macintosh’s Oxford ether vaporizer (1941) obviated the need for hefty gas or oxygen cylinders by enabling delivery of portable liquid anesthetics like ether and chloroform at controlled concentrations.⁴⁷ Initially a product of Dr. Macintosh’s experience with anesthetizing wounded soldiers during the Spanish Civil War, the compact Oxford vaporizer was mass-produced during World War II to facilitate precise anesthetic delivery in the field. In the next decade, Lucien Morris’ Copper Kettle vaporizer (1952) would allow for even finer control of volatile anesthetic delivery.⁴⁸ The introduction of vaporizers set the stage for the British introduction of halothane (1956), the first nonflammable halogenated hydrocarbon anesthetic to be used in clinical practice.⁴⁹

Tools for regional and IV anesthetic delivery were also refined. As continuous spinal anesthesia techniques were popularized, continuous caudal and lumbar epidural methods soon followed.^50,51 Softer catheters that could fit through larger Tuohy needles were developed.⁵² In addition, as barbiturates continued to be given parenterally,²⁴ more efficient IV anesthetic delivery (tubing and syringe) sets were crafted.⁵³

In the 1940s and 50s, physiological monitoring capabilities improved. Core temperature monitoring became more routine.⁵⁴ The oscilloscope now allowed for continuous ECG recording; anesthesiologists advocated for its intraoperative use.⁵⁵ By 1959, there was even a report of new dual cardiac monitor-pacemaker that could produce a continuous ECG tracing, as well as a blinking light and audible signal for each heartbeat. The device could also begin external pacing when the pulse fell below a preset minimum.⁵⁶ In the 1950s, Mayo Clinic anesthesiologists began to examine electroencephalography (EEG) changes during anesthetic induction and emergence for the first time, and a new era of depth-of-anesthesia monitoring was born.^57,58 Temperature probes, along with continuous ECG and EEG recording, would contribute to the feasibility of open-heart surgery with hypothermia and extracorporeal circulation in the late 1950s.^59,60

Finally, examination of cardiac electrical activity gave way to the novel use of electricity as a treatment for cardiac arrest in the 1950s. While open cardiac massage was still the mainstay of resuscitation,^61,62 the introduction of external pacemakers and defibrillators began to obviate the need for thoracotomy in some cases of arrest.⁶³

Another important development of the 1950s was a nascent interest in twitch monitoring to determine degree of neuromuscular blockade. In the 1940s, curare had revolutionized anesthetic practice by allowing for lighter anesthesia and smoother conditions for intubation and surgery. The introduction of succinylcholine had soon followed. In 1956, Current Researches in Anesthesia and Analgesia published an early study of skeletal muscle responses to electrical stimulation of the ulnar nerve following succinylcholine administration.⁶⁴

Finally, during this era, the journal also began to feature system-wide technological improvements. In addition, as physicians increasingly accepted the idea of giving oxygen not only to prevent hypoxia and cyanosis, but also to treat respiratory conditions like pneumonia, efforts were initiated to build hospital-wide oxygen pipeline delivery systems.⁶⁵ In the late 1950s, anesthesiologists in the United States began to organize at the national level to tackle a longstanding need for equipment standardization.⁶⁶

1960s and 1970s: Automated Monitors and the Origins of Physiological Research

The 1960s and 1970s were a vibrant time for the specialty of anesthesiology and the IARS journal, which was renamed Anesthesia and Analgesia…Current Researches in 1957. The publication’s main technological themes during this era were: 1) the continued introduction of new tools and machines for safer and more efficient anesthetic delivery, 2) the rapid development of new monitoring and measuring devices with increasing portability and automation, 3) the proliferation of research on the physiological effects of various anesthetic agents, 4) technology’s role in facilitating effective resuscitation and treatment measures, 5) the early use of computers for scheduling, knowledge sharing, and data processing.

Anesthetic hardware in the 1960s and 1970s became increasingly machine-oriented, greatly aiding anesthetic delivery. Certainly, new tools were still introduced to the market: better-fitting face masks,⁶⁷ plastic intravenous catheters,⁶⁸ thinner spinal needles,⁶⁹pre-packaged neuraxial anesthesia kits,⁷⁰ modern anesthesia carts,⁷¹ bacterial filters for anesthesia circuits,⁷² and pre-packaged polyvinyl chloride (PVC) endotracheal tubes with thin inflatable cuffs.⁷³ However, most new anesthesia equipment during this era were machines that decreased the need for human input, both physical and cognitive. Blood warmers,⁷⁴ pressurized transfusion systems,^75,76 and meters to detect intravenous drip rate facilitated transfusion and intravenous therapies. Patient-controlled analgesia devices were also introduced.⁷⁷ In the 1960s, rudimentary positive-pressure ventilators began to be made,⁷⁸ and by the 1970s, manual ventilation finally gave way to routine use of simple and cost-effective mechanical respirators like the Bird and Air-Shields ventilators.⁷⁹ Jet ventilation equipment and techniques were also developed.⁸⁰ In addition, gas scavenging systems began to protect clinicians from occupational exposure.⁸¹

During this era, advancements in electricity and engineering stimulated the production of increasingly automatic and portable monitoring devices. The 1960s saw the rise of continuous ECG oscilloscopes,⁸² pulse rate indicators,⁸³ precordial and esophageal stethoscopes,^84,85 pacemakers and defibrillators,⁸⁶ semi-automated blood pressure cuffs,⁸⁷ photoelectric plethysmographs,⁸⁸ and rapid blood-gas analyzers.⁸³ Recorders could now display multiple vital signs at once.⁸⁹ In the 1970s, hemodynamic assessment became even more streamlined. ECG, blood-pressure, and pulse rate could now be displayed continuously on a single monitor.⁹⁰ In 1976, the Dinamap, the first fully automated non-invasive blood-pressure device, was invented, and other models would follow.⁹¹ EEG could now be assessed with more compact machines,⁹² and the Swan-Ganz catheter enabled convenient assessment of a full range of hemodynamic variables.^93,94 End-tidal carbon-dioxide monitoring systems began to be conceived in the 1970s.⁹⁵

As an example, monitoring systems at the National Institutes of Health (NIH) as early as the 1960s reflected the most advanced technology available, with electrical input to consoles capable of displaying measurements of arterial blood pressure, venous pressure, heart rate, respiratory rate, continuous ECG and EEG, temperature, end-tidal carbon-dioxide, plethysmography waveforms, blood loss, and blood flow (when pump oxygenators were used).⁹⁶ Blood-gas analyzers were readily available; John Severinghaus, MD, and his technician A. Freeman Bradley had designed the first three-function blood-gas analyzer, which allowed for simultaneous measurement of pH, pO₂, and pCO₂, in the 1950s while Severinghaus was the NIH Director of Anesthesia Research.

With the revolution in medical electronics and growing interest in EEG, anesthesiologists of the 1960s and 1970s also experimented with electrical anesthesia, using both direct and alternating currents to induce an anesthetic state in both animals and humans.^58,97,98 However, many clinicians considered the adverse effects associated with this method—hypertension, electrode displacement, muscle spasms—to be undesirable.^97,99

Interestingly, the proliferation of external defibrillators in the 1950s and the unintentional production of an arterial pulse by paddle placement on the anterior chest led to the acceptance of closed-chest cardiac compressions as a primary resuscitation technique in the 1960s. Anesthesia and Analgesia…Current Researches highlighted some of the work of Peter Safar, MD, and James Elam, MD, in combining external compressions and defibrillation with mouth-to-mouth resuscitation to develop the foundations of modern cardiopulmonary resuscitation.^100–103 Soon, several devices capable of delivering closed-chest compressions were designed, but one paper determined them to be suboptimal to manual compressions at the time.¹⁰⁴

Also in the 1960s, the increased sophistication of monitoring devices and vascular catheters led to a novel treatment for venous air embolism. In the setting of acute air embolism during craniectomy in the sitting position, John Michenfelder, MD, and colleagues at Mayo Clinic had astounding success with aspirating air from a central venous catheter positioned under electrocardiographic guidance.¹⁰⁵ Intraoperative use of an esophageal stethoscope to detect an acute murmur, along with evidence of hypotension and a ventricular arrhythmia, had enabled the initial diagnosis.¹⁰⁵

In addition, sophisticated monitoring technologies and rapid, accurate ways to measure concentrations and solubilities of volatile agents led to a proliferation of research studies on the physiological effects of anesthetics and their uptake and distribution. For example, the journal in the 1960s published several papers on ECG and EEG effects of intubation and physiological derangements under different anesthetics, most notably halothane.^106–108 Other articles studied anesthetic effects on cardiac function, using strain-gauge manometers to measure ventricular pressures and an indicator-dilution technique to determine cardiac output.^109,110 As the National Halothane Study was examining the question of halothane hepatotoxicity on a large multicenter scale, several smaller studies on the anesthetic effects on liver and kidney function were also published.^111,112 New techniques like gas chromatography and infrared analysis enabled precise measurement of vapor concentrations,^113,114 enabling studies on the uptake and distribution of oxygen and anesthetic agents.¹¹⁵

In the 1970s, studies of the physiological effects not only of halothane, but also of newer agents like methoxyflurane and enflurane, abounded.^116–118 However, the latter two anesthetics were short-lived, as evidence quickly emerged of high-output renal failure due to methoxyflurane, and seizure activity due to enflurane. Physiological studies of new IV agents like ketamine and etomidate also proliferated.^119–121

The use of agents like halothane and succinylcholine had given rise to a new life-threatening reaction to anesthesia—malignant hyperthermia, with initial reports arising out of Australia by Denborough et al. in the early 1960s.¹²² While improved monitoring capabilities and the invention of the blood-gas analyzer also enabled definition of the physiological manifestations of malignant hyperthermia (MH) in the 1960s, MH diagnosis and treatment modalities began to be investigated in porcine models in the 1970s.^123–125 Finally, as methods of reversing neuromuscular blockade were examined,^126,127 techniques of monitoring depth of blockade improved dramatically with the discovery of train-of-four analysis and the development of compact, non-invasive twitch monitors that used cutaneous electrodes.^128,129

During this era, computer processing also began to be used in earnest. Preliminary reports of computer analysis emerged in the journal in the late 1960s, but at the time, data still had to be collected manually and sent to large processing centers for interpretation.^130,131 Even the National Halothane Study, a major achievement in computer processing, had relied on initial data preparation by hand before analysis could occur at Computation Centers at Stanford and Harvard. The development of microprocessors in the early 1970s was a monumental achievement. During this decade, computers began to schedule operating-room cases and personnel, interpret ECGs, analyze physiological data, and store and make readily available vast quantities of biomedical literature.^132–136

By the end of the 1970s, anesthetic practice and patient monitoring had become significantly more machine-driven. Anesthesiology as a medical and scientific discipline had indisputably come into its own. As Dr. Nicholas Greene, Immediate Past Editor-in-Chief of Anesthesiology, took leadership of Anesthesia and Analgesia…Current Researches, the journal was well poised to enter the digital era. In 1979, it underwent another name change to Anesthesia & Analgesia, and in 1980, publication increased from bimonthly to monthly, reflecting the growing research productivity of the global anesthesia community.

The 1980s and 1990s: Pulse Oximetry, Computers, and Simulation

Technological advances in anesthesia accelerated during the 1980s and 1990s, the era of the computer and Internet revolutions. They went hand-in-hand with the development of numerous anesthetics and drugs that are still in use today: the inhalational agents isoflurane, desflurane, and sevoflurane; the intravenous sedatives midazolam, propofol, and dexmedetomidine; the local anesthetic ropivacaine; and the neuromuscular blockers vecuronium, cisatracurium, and rocuronium. The concept of the anesthesiologist as a perioperative physician also began to be popularized in the 1990s.¹³⁷

The main technological themes in Anesthesia & Analgesia in the late 20^th century were: 1) the continued refinement of tools and machines for anesthetic delivery and airway management, 2) the consolidation of the foundational devices for monitoring in anesthesia, exemplified by the pulse oximeter and capnograph, 3) the use of computer processing to develop simulation for crisis management, to improve efficiency in health systems, and to conduct large-scale outcomes trials.

As the anesthesiologist’s armamentarium of safe and effective drugs grew, anesthesia tools and machines also became more intelligent. New laryngoscopes, double-lumen tubes, flexible bronchoscopes, and the laryngeal mask airway (LMA) were invented to facilitate airway management.^138,139 Delivery of volatile anesthetics became increasingly precise and physiologically attuned, as even more efficient vaporizers and multimodal ventilators began to be used.^140–142 The 1990s finally saw the emergence of the modern anesthesia workstation, which for the first time combined advanced monitoring with vaporizers and a positive-pressure ventilator, all within a closed-circuit breathing system. In addition, this period saw the rise of ultrasound technology in enabling transesophageal echocardiography and in facilitating regional block and invasive line placement.^143,144

In the 1980s and 1990s, monitoring capabilities also multiplied, and Anesthesia & Analgesia reflected this trend. While oxygen analyzers within anesthesia circuits ensured adequate oxygen delivery,¹⁴⁵ the pulse oximeter now dazzled clinicians everywhere, affording instantaneous, continuous, and non-invasive determination of oxygen saturation.^146,147 Capnography soon followed, and by the 1990s, end-tidal carbon-dioxide monitoring with waveform displays achieved routine use.¹⁴⁸ Processed EEG also offered a convenient way to assess depth of anesthesia, especially in cases of a “balanced” or total intravenous anesthetic technique.¹⁴⁹ Finally, 1996 saw the journal’s first publication of a study that used arterial pressure waveform analysis and systolic pressure variation to assess intravascular volume status.¹⁵⁰

In the late 20^th century, delivery technology for intravenous fluids, transfusions, and anesthetics also became more mechanistic and automated. Syringe infusion pumps permitted precise titration of medications,¹⁵¹ and new autotransfusion systems facilitated resuscitation of patients who bled during surgery.¹⁵² While an early report of computer-controlled regulation of a sodium nitroprusside infusion according to blood pressure measurements appeared in the journal in 1985,¹⁵³ the 1990s saw a proliferation of studies on various target-controlled infusion (TCI) devices.¹⁵⁴ This change was heralded by growing clinical use of propofol in the 1990s, along with deepening knowledge of propofol pharmacokinetics.

Computer processing began to be used for a wide range of developments. David Gaba, MD, and colleagues created a high-fidelity mannequin simulator using real operating-room equipment and a cardiovascular modeling algorithm to train anesthesiologists in crisis management.¹⁵⁵ Simulation-based education gained widespread interest in the 1990s.¹⁵⁶ Anesthesia & Analgesia also published several studies that used computer simulation for an entirely different purpose—health systems research and specifically, greater efficiency in operating-room scheduling.¹⁵⁷

The 1990s also saw the parallel rise of clinical outcomes research in anesthesia with the crystallization of the concept of the anesthesiologist as a perioperative physician. With sophisticated monitoring technology in hand, anesthesiologists began to investigate ways that specific physiological variables could be adjusted to affect perioperative outcomes. As growing numbers of large computer databases were created to store and process patient information, complex computer analyses could now reveal associations between controllable patient variables (like intraoperative hemodynamics) and specific measures of morbidity and mortality.^158,159

2000 to 2022: Automated Anesthesia, Advanced Monitors, and Artificial Intelligence

On January 1, 2001, Anesthesia & Analgesia created a new section on Technology, Computing, and Simulation as it became the official journal for the Society for Technology in Anesthesia (STA).¹⁶⁰ The STA had been founded in 1988 to promote and study the application of technology to modern anesthesiology.¹⁶⁰ Steven Barker, PhD, MD, a Past President of the STA, became the first Section Editor and served in this role from 2001 to 2006. Subsequent Section Editors were Jeffrey Feldman, MD (2007 to 2009), Dwayne Westenskow, PhD (2009 to 2013), Maxime Cannesson, MD, PhD (2013 to 2019), and Thomas Hemmerling, MD (2019 to present).

The evolution of technology in anesthesiology and perioperative medicine since 2000 has mainly centered around five key topics: 1) the development of advanced physiological monitoring systems, 2) the electronic health record, 3) the use of clinical research methodologies to evaluate the impact of technologies on patient outcomes, 4) applications of computer science, robotics, and control engineering to the perioperative environment, and 5) the promotion of patient safety and cybersecurity through coordination between technologies (device interoperability) and health informatics systems.

The past twenty years have seen a wealth of technological innovations in society, medicine, and anesthesiology. The major trend has been a transition from hardware to software, with steady movement toward the concept of digital health. Anesthesia & Analgesia has been at the forefront of these advances by publishing some of the most important papers on technology in anesthesia, and STA members have made significant contributions.

Since 2000, the field of physiological monitoring has evolved dramatically. Physiological signals that had previously been used to guide clinical decision-making for decades have been analyzed in novel ways to obtain new information. The morphological analysis of the arterial pressure waveform has led to software development to measure pulse pressure variation (PPV) and stroke volume variation (SVV).^{150,161–164} In the same vein, revived interest in photoplethysmography and analysis of the pulse oximeter waveform has also provided novel physiological insights^165–169 and has opened the door to many new fields of investigation.^170–174

Many new monitoring systems have proliferated during the past two decades, and today we can measure the whole of human physiology continuously and non-invasively.¹⁷⁵ At this stage, the main question has become: which monitors actually improve patient outcomes? It is likely that the next decade will focus heavily on this topic, which has already begun to be explored in earnest. For example, Anesthesia & Analgesia has published several clinical studies on goal-directed therapy using non-invasive cardiac output monitors and the pleth variability index, which is derived from the pulse oximeter waveform.^176–179 In addition, the journal has also featured quality improvement studies that focus on the role of new monitoring systems in improving patient safety.^180,181

The Electronic Health Record (EHR) and the Anesthesia Information Management Systems (AIMS) have transformed our specialty¹⁸² and now offer promising developments in descriptive, predictive, and prescriptive analytics that we are only beginning to understand. Data collected through these systems has already facilitated operating room management,^183,184 anesthesia billing,¹⁸⁵ and documentation.^185–187 Live data input into AIMS has also enabled the development of clinical decision support systems to improve the quality and safety of care by modifying physician behavior.^188–192 In spite of a beneficial effect overall, these innovative systems have not been immune to potential downsides such as data inaccuracy^193,194 and clinician burnout.¹⁹⁵

In the past five years, Anesthesia & Analgesia has published numerous studies on artificial intelligence (AI) and machine learning that focus on the use of perioperative EHR and AIMS data for diverse applications, including: the digital phenotyping of diseases,^196–199 outcomes prediction,^200,201 and the forecasting of vital signs. The journal has also widely explored the topic of implementing data warehouses and collaborative research based on EHR and AIMS information.^202,203 The Multicenter Perioperative Outcomes Group (MPOG), which has integrated EHRs from multiple centers across the United States and Europe in order to facilitate quality improvement, is the most successful example of this approach.²⁰⁴ Finally, with the rapid rise of AI applications in anesthesiology and perioperative medicine, the journal has also highlighted the ethical issues involved with developing such systems.²⁰⁵ In May 2020, Anesthesia & Analgesia published a special issue on “Anesthesia and Artificial Intelligence,” which covered most of these topics.^{196,200,204–215}

Robotic and closed-loop anesthesia systems have also been featured in several articles. Notable examples include the Kepler Intubation System, which enabled robot-assisted tracheal intubation, and the Magellan system, which performed robot-assisted ultrasound-guided nerve blocks.^216,217 Numerous manuscripts on fully automated anesthetic delivery have also been published,²¹⁸ from automated general anesthesia,^219,220,206 to automated sedation for transcatheter aortic valve replacement,²²¹ and from simple pilot studies²²² to randomized controlled trials.^223,224

At the same time, Anesthesia & Analgesia has also led the way in publishing articles from Food and Drug Administration (FDA) authors that delineate the regulatory pathways that need to be passed to make automated anesthesia systems commercially available.²²⁵ Although it is unclear when these systems will be able to enter clinical practice, regulatory barriers have now been identified and discussed extensively. One identified obstacle is the fragmented state of the technological ecosystem in present-day operating rooms. For example, current drug infusion devices and monitoring systems do not communicate and thus live in radically different regulatory environments.

In recent years, there has been a growing interest among clinicians, biomedical engineers, and medical device manufacturers to increase interoperability between various medical devices (e.g. monitors and drug delivery devices) and health information technology systems. The ultimate hope is to improve patient safety and also to preserve cybersecurity by facilitating coordination between different technologies and by preventing leakage of electronic data as it transfers from one device to another.^226,227

Conclusion

Over the past century, Anesthesia & Analgesia has highlighted a technological evolution in anesthesiology that has corresponded with Richta and Bloomfield’s progressive stages of “The Tool,” “The Machine,” and “Automation.” As anesthesiologists developed their professional identity in 1920s and 1930s, the primary focus was on developing effective tools and techniques for anesthetic delivery. The 1940s and 1950s signaled the growth of “machines” in anesthesia—modern anesthetic vaporizers, the blood-gas analyzer, and continuous electrocardiography and electroencephalography. In the 1960s and 1970s, “automation” entered the picture, as simple mechanical ventilators and automated non-invasive blood-pressure devices began to be used routinely. During this period, new monitoring and measuring technologies also led to a proliferation of research studies on the physiological effects of specific anesthetic agents. The 1980s and the 1990s, the era of the computer revolution, witnessed the emergence of advanced machines like the anesthesia workstation, the ultrasound, the pulse oximeter, the capnograph, and the mannequin simulator. Anesthetic delivery technology also became more automated, and target-controlled infusion (TCI) devices gained momentum.

As anesthesiologists entered the 21^st century, Anesthesia & Analgesia affiliated with the Society for Technology in Anesthesia and created a new section on Technology, Computing, and Simulation. Anesthetic software development facilitated advanced physiological monitoring of arterial pressure and pulse oximeter waveforms, and also led to the production of non-invasive cardiac output monitors. As interest in artificial intelligence has grown, the electronic health record and information systems have enabled large-scale health systems research, as well as the prediction of outcomes and hemodynamic shifts. Finally, as a powerful manifestation of “Automation,” Richta and Bloomfield’s third and final stage of technological evolution, numerous papers have also been published on robot-assisted anesthetic procedures and fully automated, “closed-loop” anesthesia.

Anesthesia & Analgesia has played a significant role in highlighting the technological changes that have shaped our specialty over the past 100 years. These advances have allowed anesthetic delivery to become safer, smoother, and more efficient—both simpler and more refined. At the same time, as medical technology evolves, and as our specialty leads the way, it will be paramount to take into account the potential downsides of these technological developments and their impact on patients and practitioners. We are confident that Anesthesia & Analgesia will continue to drive this conversation. The future remains a mystery, but it is bright with possibility.

Glossary of Terms

STA

Society for Technology in Anesthesia

NARS

National Anesthesia Research Society

IARS

International Anesthesia Research Society

AAA

Association of American Anesthetists

NYSA

New York Society of Anesthetists

ASA

American Society of Anesthetists

LMA

laryngeal mask airway

ECG

electrocardiogram

IV

intravenous

EEG

electroencephalography

PVC

polyvinyl chloride

NIH

National Institutes of Health

MH

malignant hyperthermia

TCI

target-controlled infusion

PPV

pulse pressure variation

SVV

stroke volume variation

EHR

Electronic Health Record

AIMS

Anesthesia Information Management System

AI

artificial intelligence

MPOG

Multicenter Perioperative Outcomes Group

FDA

Food and Drug Administration