The discoveries that facilitated patient monitoring in the perioperative period occurred long before the introduction of clinical anesthesia. Respiratory patterns had been described since antiquity. The rise of scientific methods in Renaissance Europe led to the initial experiments in hemodynamics – specifically, animal experiments demonstrating that blood flows under pressure. The earliest source that cited correct observations of arterial and venous flow and pressures was William Harvey's De Motu Cordis, published in 1628.1 In the following century, Stephen Hales offered the first quantification of arterial blood pressure measured in the horse.2 The first cardiac catheterization was performed by Claude Bernard in 1844.3
Soon after the introduction of clinical general anesthesia by W. T. G. Morton in 1846 and John Snow in 1847, the need to monitor patients was recognized by the leaders of the new specialty. The first documented death under chloroform anesthesia (that of fifteen-year-old Hannah Greener in 1848) led the early practitioners to highlight the importance of monitoring simple vital signs – respiration, pulse, and skin color. Since that time, patient safety concerns have invariably driven the development of monitoring modalities and standards in perioperative monitoring practice. This chapter recounts important milestones of perioperative patient monitoring and the historical events and clinical developments that influenced them.
As news of the Boston public demonstration reached London late in 1846, John Snow, M.D. personally adopted the technique, publishing his series of eighty anesthetized patients, ranging in age from children to octogenarians, in Inhalation of the Vapour of Ether in Surgical Operations. He mentioned the customary monitoring under anesthesia to include respiration depth and frequency, muscle movements, skin color, and stages of excitation or sedation. Although the pulse was continually palpated, its characteristics were not considered worth studying.4 By 1855, the Edinburgh surgeon James Syme, M.D., lectured on the importance of monitoring respiration and explained in his surgical lectures that, in his opinion, chloroform was safer than ether anesthesia if it was administered properly. The key, however, to proper administration was monitoring the patient's respiration.5
Joseph Lister, M.D., the founder of the principles of antisepsis in surgery, was an eminent surgeon in Scotland and the United Kingdom from the 1850s through the 1890s. He protested against palpation of the pulse as “a most serious mistake. As a general rule, the safety of the patient will be most promoted by disregarding it altogether, so that the attention may be devoted exclusively to the breathing.”6 Dr. Lister's instruction to the senior students who served as his anesthetists was “that they strictly carry out certain simple instructions, among which is that of never touching the pulse, in order that their attention may not be distracted from the respiration.” His airway management strategy included “the drawing out of the tongue” and he believed that the services of special anesthetists were unnecessary if simple routines were followed by his assistants while administering chloroform.
Joseph Thomas Clover, M.D., was the leading clinical anesthetist in Victorian England during his professional life, from the beginning of his anesthesia practice in 1846 until his death in 1882. In 1864, the Royal Medico-Chirurgical Society established a committee to investigate chloroform fatalities, and as an expert assistant to that group, Dr. Clover described his innovations in apparatus and animal experimentation with anesthetics. He strongly advised that the pulse be continuously observed during an anesthetic and that irregularities such as a diminution should alert the anesthetist to discontinue the anesthetic. He also advised monitoring the pulse continuously while administering an anesthetic. “If the finger be taken from the pulse to do something else, I would give a little air.”7 James Young Simpson, M.D., also voiced caution during the administration of chloroform when snoring ensued and the pulse became “languid.”8
With continuing deaths associated with chloroform use, a group led by Edward Lawrie formed a commission in Hyderabad, India to investigate causes. In 1888, the first commission report asserted the safety of chloroform anesthesia.9 In 1889, the Second Hyderabad Chloroform Commission concluded that chloroform deaths were related to respiratory depression and not a directly injurious effect on the heart. The commission reported that anesthetists should be guided entirely by respiration, as pupil size and pulse were not significant enough to monitor.10,11
The earliest clinical account of auscultation in the operating room was reported in 1896 by Robert Kirk, M.D., of the Glasgow Western Infirmary. An ordinary binaural stethoscope lengthened by Indian rubber tubing was first used. Later, 200 patients anesthetized with chloroform were auscultated using a “phonendoscope” with timing of heart rate and rhythm by a watch.12 Dr. Kirk was involved at the time with the Glasgow Committee on Anesthetic Agents and saw the stethoscope as a clinical research tool to assess the effects of chloroform on cardiac physiology.
Charles K. Teter, D.D.S., described the benefits of using a stethoscope during anesthesia, especially in poor-risk patients.13 He praised the convenience of the flat Kehler stethoscope, which “will usually stay without being held” on the precordium. When necessary, adhesive tape prevented its being dislodged. Dr. Teter praised the stethoscope because “uninterrupted information will be given to any and all change[s] in the heart beat and respiration.” He expressed his feeling of confidence when “every variation of heart sound is at once discernable, and what might be serious complications can be averted by the premonitory symptoms thus made manifest.”13
The strong advocacy of routine, continuous monitoring of cardiac and respiratory sounds under anesthesia by Harvey Cushing, M.D., gave impetus to the widespread clinical use of intraoperative auscultation14 (see Figure 1.1). An esophageal stethoscope was described in 1893 by Solis-Cohen15 for diagnostic purposes, but it was not adopted as a routine monitoring technique until nearly seventy-five years later.
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Once the idea that monitoring patients under anesthesia was clinically useful and early tools were developed to do so, the anesthetic record could not be far behind. B. Raymond Fink, M.D., credits the first anesthetic record to A. E. Codman, M.D., at the Massachusetts General Hospital in 189416 (Figure 1.2). Dr. Codman's chief, F. B. Harrigan, M.D., recommended recording the patient's pulse during an anesthetic. This practice was encouraged by Dr. Cushing, who published a classic paper in 1902 reproducing an actual patient's anesthetic record.17 Dr. Cushing's initiatives were not accepted easily, and opponents to the newer devices to measure temperature, pulse, blood pressure, and the auscultation of the heart were castigated by an editorial in the British Medical Journal claiming that “by such methods we pauperize our senses and weaken clinical acuity.”18
In 1901, during a visit to Italy, Harvey Cushing met Scipione Riva-Rocci, who, a few years earlier, had developed a practical sphygmomanometer for measuring blood pressure indirectly.19 Subsequently, Cushing recommended the routine use of this sphygmomanometer to determine blood pressure during anesthesia.20 Because the return-to-flow method was employed by palpation of the radial pulse, only the systolic pressure could be determined. Furthermore, this was inaccurate, as the cuff used was a bicycle inner tube, which gave excessively high values owing to the ratio of the region of compression to arm circumference. At that time, however, normal values for systolic blood pressure were unknown and the instrument provided the first clinical example of following trends of blood pressure change during surgery.
In 1905, Korotkoff described the sounds heard when flow occurs distal to the deflating cuff.21 This, together with the use of a wider cuff advocated by von Recklinghausen,22 allowed more accurate determination of blood pressure and is the basis of current auscultatory blood pressure monitoring. Further advances in the indirect measurement of blood pressure largely involved the development of alternative means of “sensing” systolic and diastolic points and automating the process.
In 1931, von Recklinghausen23 described a semiautomated device for measuring blood pressure, known as an oscillotonometer. A double-cuff system was used, with the proximal cuff occluding the artery and the distal cuff acting as the sensor to detect the onset of arterial pulsations. The introduction of ultrasound into clinical medicine in the 1940s allowed the application of the Doppler principle to detect blood flow24 and movement of the arterial wall under the distal edge of the sphygmomanometer cuff.25 The Arteriosonde (Roche) used ultrasound at 3 mHz that reflected off the vibrating arterial wall, which the practitioner heard as an electronically conditioned audible signal. The device was accurate and found its greatest application for measurement of blood pressure in infants.26 The
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Although Snow and other early leaders of the specialty described the monitoring of depth of anesthesia, the individual given greatest credit for standardizing the process was Arthur Guedel, M.D. The eye signs of ether anesthesia were the most significant contribution to his schematic approach to identifying signs of anesthesia.28 The eye signs included the activity of motor muscles of the eyeball, pupillary dilation, and, later, the eyelid reflex. The eyelid reflex was tested by gently raising the upper eyelid with the finger. If the reflex was present, the eyelid would attempt to close at once or within a few seconds. The corneal and eyelash reflexes known today were not mentioned.29
The setting for these contributions was the complete lack of trained anesthesia specialists when the United States entered World War I.30 Dr. Guedel experienced a crush of casualties from a major battle, where his staff of three physicians and one dentist ran as many as forty operating room tables at a time. He concluded that additional anesthesia care providers would have to be trained quickly to meet this overwhelming need and created a school that trained physicians, nurses, and orderlies in open-drop ether.29 He prepared a chart of his version of the signs and stages of ether anesthesia, the most common agent in use at the time because of its wide margin of safety (Figure 1.3). Armed with their charts, the trainees went out to nearby hospitals to work on their own, as Dr. Guedel made weekly motorcycle rounds to check on his trainees at the six hospitals for which he was responsible.30
Poiseuille, in 1828, described the mercury manometer.31 In 1847, Karl Ludwig made use of Poiseuille's device and applied it to his invention of the kymograph.32 A column of mercury on the kymograph moved, and thus directed a floating needle against a moving drum. This device allowed animal hemodynamic physiology to be recorded continuously for research purposes. The application to humans, however, was limited by problems of vascular access and control of bleeding and infection. Almost one century later, direct recording of arterial blood pressure continued to be difficult, even though problems of sepsis and coagulation were solved.
The discovery of plastic “nonthrombogenic” sterile tubing and its medical applications occurred in 1945–46. In 1949, Lyle Peterson and Robert Dripps described the technique of percutaneous placement of a plastic catheter for continuous measurement of arterial blood pressure during anesthesia and surgery.33
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The technique of surgical cut-down was used to gain access to peripheral arteries during cardiac surgery in the 1950s. In 1960, the catheter-over-the-needle technique was introduced, and the wide medical application of polytetrafluoroethylene (PTFE; Teflon, Dupont, Inc.) Teflon made possible convenient percutaneous access, leading to easier and smoother percutaneous placement of cannulae for continuous monitoring of arterial blood pressure by surgeons, anesthesiologists, and intensive care specialists. Simultaneous technological advances in pressure transducers, continuous flush systems, and transistor-based display and recording equipment made invasive arterial monitoring commonplace.
In 1918, Heard and Strauss34 reported two cases of atrioventricular rhythm, one of which occurred immediately following ether anesthesia. They reported that “no other cases of nodal rhythm have been observed by us in a series of 21 cases in which electrocardiographic records have been taken during anesthesia.” No further details were given. Levine35 reported two cases of paroxysmal atrial tachycardia under ether anesthesia, documented by electrocardiography.
The first prospective study of the practical use of the electrocardiograph (ECG) for monitoring patients in the operating room was reported in 1922. Lennox, Graves, and Levine36 studied fifty operations performed on forty-nine patients at the Peter Bent Brigham Hospital in Boston. The monitoring method was onerous. The electrocardiographer was summoned by a buzzer in the operating room at the beginning and end of the operation and during critical moments in the operation. ECG tracings were produced by a string galvanometer, at average intervals of 2.5 minutes. For a permanent record, photographic paper had to be exposed to light. The heart rate calculated from the ECG tracings was much higher than the count of the anesthetist. The most marked discrepancies usually occurred during induction of anesthesia, when the pulse rate was taken by a nurse from the ward. Abnormalities of conduction (displacement of pacemaker) were found in 15 (30%) of the cases and 11 cases developed premature beats, seven of them ventricular in origin. None of these premature beats was noted by the anesthetist. Analysis of the patients’ characteristics, type of surgery, and type of anesthesia failed to demonstrate predisposing factors apart from alterations in vagal tone.
The value of the electrocardiogram during surgery was demonstrated by further similar studies.37–39 The intermittent nature of the recording and the inevitable delay in developing ECG tracings on photographic paper, however, limited the usefulness of these observations for diagnosis and therapy. Direct-writing ECG recorders eliminated the delay associated with processing films but were impractical for obtaining continuous records.40
In 1952, Himmelstein and Scheiner described a cardiotachoscope, which permitted continuous display of the ECG on a cathode ray screen.41 The heart rate, obtained by measuring the time interval between successive beats, appeared as a moving line on the calibrated screen of a cathode ray tube. A direct writing cardiograph could be attached to the instrument to obtain permanent records.
With the advent of continuous ECG monitoring devices, the routine use of the ECG to detect abnormalities of rhythm and rate became practical, albeit too expensive for routine use. Several reviews and studies42,43 documented the type and incidence of dysrhythmias that could occur during anesthesia. Lead II was usually monitored because the axis paralleled the normal P wave vector, facilitating easy recognition of dysrhythmias. The application of the ECG to detect myocardial ischemia during anesthesia was first proposed by Kaplan and King.44 In patients undergoing stress tests, Blackburn45 had previously found that the majority of ischemic episodes could be detected by precordial lead V5 of a 12-lead electrocardiogram. Kaplan46 demonstrated successful use of a modified CM5 lead in anesthetized patients. This lead was practical with three-lead ECG systems, then in common clinical use in the operating room.
Werner Forssmann is credited with being the first person to pass a catheter into the heart of a living person47, using himself as the subject. He passed a ureteral catheter through one of his left antecubital veins, guiding it by fluoroscopy into his right atrium, and then confirming the position by chest roentgenogram. In 1930, Klein reported eleven catheterizations of the right side of the heart, including catheterization of the right ventricle and measurement of cardiac output in humans, using Fick's principle.48 In the 1940s, catheterization of the right side of the heart began to be used to investigate problems of cardiovascular physiology by Cournand,49 who later received the Nobel prize (together with Forssmann) for his pioneering efforts.
In 1947, Dexter50 and Werko51 reported on oxygen saturation in the pulmonary artery and demonstrated, for the first time, the value of the pulmonary artery wedge pressure in estimating left atrial pressure. In 1970, a balloon-tipped flow-guided catheter technique was introduced by Swan and Ganz, making possible the use of the catheter outside the catheterization laboratory in intensive care units and operating rooms.52
As related by John W. Severinghaus, respiratory physiology became important when World War II pilots trying to fly higher than their enemies became hypoxic (without cabin pressurization), lost consciousness, and crashed. Physicist Glen Millikan (1906–1947) developed oximetry in 1940 as a pilot warning device, but the technology became practical only when pulse oximetry was introduced in approximately 1980. The polio epidemics drove the development of artificial ventilation, with the need for carbon dioxide analysis to guide the ventilation of a paralyzed patient. The mid-20th-century advances in the use of hypothermia and cardiopulmonary bypass necessitated frequent monitoring of oxygenation and acid–base status.53
Severinghaus built a cuvette for the carbon dioxide electrode and mounted it in a 37°C water bath. His modifications of Stow's invention cut analysis time from an hour to two minutes. Clark had built a successful bubble-type blood oxygenator to perfuse livers.54 To measure PO2 in the oxygenator, he turned to polarography. In 1954, Clark made an electrically insulated polarographic sensor with cathode and reference electrode combined, permitting it to work in either air or liquid.
With Clark's approval, Severinghaus used his electrode and his modification of Stow's carbon dioxide electrodes in a blood gas analyzer. Severinghaus displayed the first blood PO2 and PCO2 analyzer at the fall American Society of Anesthesiologists meeting in 1957.55 The addition of a pH electrode completed the modern arterial blood analysis device.
In the 1960s, with the advent of oxygen therapy and positive pressure ventilation of premature infants, it became apparent that excessive oxygenation was associated with blindness. Transcutaneous blood gas monitoring was developed primarily to avoid oxygen-induced retinopathy of prematurity. A skin surface oxygen electrode heated to 44°C accurately monitored PaO2.56 Severinghaus further developed a transcutaneous PCO2 electrode57 and combined oxygen and carbon dioxide electrodes under a single membrane.58
At the time when d-tubocurarine (1942), alcuronium (1964), and pancuronium (1967) were the staple relaxants, Christie and Churchill-Davidson59 and Katz60 first popularized the use of peripheral nerve stimulation in the mid-1960s (the Block-Aid monitor) to evaluate neuromuscular function. This device applied a twitch (every four seconds) or tetanic stimulation (30 Hz on demand). These investigators popularized the observation and recording of adductor responses from the thumb, elicited via the ulnar nerve at the wrist.60 Shortly thereafter, Ali and others (1971)61 introduced train-of-four (TOF) stimulation, and Lee (1975)62 further popularized this technique by quantifying and correlating depth of blockade (percent twitch inhibition) according to the TOF count.
The TOF technique has remained the most useful method of evaluation of neuromuscular function in clinical anesthesia practice for more than thirty years because of its simplicity and ease of evaluation and because the stimulus pattern creates its own internal standard each time the response is evaluated; that is, the strength of the fourth response is simply compared with that of the first without the need for establishment of a baseline prior to the administration of neuromuscular blocking drugs.63
As recounted by Ellison Pierce, the latest historical drivers of improvements in anesthesia monitoring were a combination of media attention to anesthetic deaths and a malpractice insurance rate crisis of the 1970s and 1980s.64 The field of anesthesia safety research was advanced in 1978 with the publication of Jeffrey Cooper's first paper describing critical incident analysis applied to anesthesia.65 Cooper stated, “Factors associated with anesthetists and/or factors that may have predisposed anesthetists to err have, with a few exceptions, not been previously analyzed. Furthermore, no study has focused on the process of error – its causes, the circumstances that surround it, or its association with specific procedures, devices, etc. – regardless of final outcome.”
Data for this first critical incident technique study were obtained from 47 interviews of staff and resident anesthesiologists. In a follow-up paper published in 1984, the database was enlarged to include 139 practitioners and 1089 descriptions of preventable critical incidents.66 Cooper proposed corrective strategies to lessen the likelihood of an incident occurring, including using appropriate monitoring instrumentation and vigilance.67
Major mortality studies have come from the United Kingdom, where Lunn and associates established a confidential, anonymous system to report anesthesia deaths associated with surgery. Their initial report was published in 1982, and anesthesia was considered partly or totally causative of mortality in one or two cases per 10,000 and to be totally causative in nearly 1 per 10,000. Their monitoring-related findings were that that large numbers of patients did not have blood pressure recorded intraoperatively and did not have intraoperative monitoring with the electrocardiogram.68
The Closed Claims Project of the American Society of Anesthesiologists (ASA) found that adverse respiratory events constituted the single largest class of injury, some 35 percent of the total.69 The first three mechanisms of adverse respiratory events were inadequate ventilation (38%), esophageal intubation (18%), and difficult intubation (17%), and the majority of respiratory claims were lodged before widespread adoption of pulse oximetry and capnography. The reviewers concluded that better monitoring would have prevented adverse outcomes in three-quarters of the respiratory claims, compared with only around 10 percent in the nonrespiratory cases.
There is indirect evidence that the advent of ASA basic monitoring standards has diminished the incidence of adverse respiratory events in anesthesia. Eichhorn reviewed 1 million anesthetics administered to ASA physical status 1 and 2 patients at the various Harvard hospitals between 1976 and 1985, and noted 11 major intraoperative anesthesia accidents (2 cardiac arrests, 4 cases of severe brain damage, and 5 deaths).70 The most common cause (7 of 11) was an unrecognized lack of ventilation. He concluded that these seven, as well as one other, in which oxygen was discontinued inadvertently, would have been prevented by “safety monitoring.” Of the next 300,000 anesthetics after the institution of the Harvard capnography and pulse oximetry monitoring standards in 1985, there were no major preventable intraoperative anesthesia injuries.
The evidence-based monitoring standards and guidelines that emerged in the 1980s and 1990s have changed the practice of anesthesia and evolved over time. The ASA and peer organizations embraced evidence-based standards and practice parameters related to basic monitoring standards, transesophageal echocardiography, and pulmonary artery catheterization (http://www.asahq.org/publicationsAndServices/sgstoc.htm, accessed February 7, 2011).
In conclusion, the history of anesthesia monitoring is a fascinating prelude to the remainder of this text. A remarkable group of perioperative physicians who were dedicated to improving patient outcomes persevered to advance the specialty, despite resistance from peers who did not share their vision. The gradual advance in the quality and sophistication of instrumentation and the regression of clinician observations of physical signs is another theme that is remarked on by every chronicler of anesthesia history. The recent decades have also brought the rise of standards in monitoring practice. The history of anesthesia clearly shows how safer anesthesia practices have arisen through improved patient monitoring. The lesson to be taken from this chapter is that we still have the capacity for further improvements in perioperative patient safety, and that we will remember most clearly those perioperative physicians who advance that goal.
The author is indebted to Selma Harrison Calmes, M.D., Lydia A. Conlay, M.D., Ph.D., Doris K. Cope, M.D, James C. Erickson III, M. Ellison C. Pierce, Jr., M.D., John Severinghaus, M.D., and George Silvay, whose writings served as the source material for this chapter. Additionally, the staff of the Wood Library–Museum of Anesthesiology, Park Ridge, IL, were instrumental in providing research and support.
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