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Biomedical subjects

J S Gravenstein

Publications and source records attributed to J S Gravenstein.

At least 37 records · Page 2Linked to original sources
PubMed1993

Acceptable ranges for vital signs during general anesthesia.

OBJECTIVE: Define the ranges for normal vital signs during general anesthesia. METHODS: We studied 50 patients undergoing general anesthesia. We asked residents to state desirable ranges for each patient's systolic and diastolic blood pressure (BP), heart rate (HR), SpO2, and PETCO2 during induction, intubation, maintenance, and emergence from anesthesia. We called these ranges the clinical operating range (COR) and observed the frequency, duration, and magnitude of transgressions of these CORs. We also recorded whether the transgressions were treated or tolerated, or whether the COR values were changed. RESULTS: Upper COR values in the maintenance phase for systolic BP were 38% +/- 20% above the preoperative values and 30% +/- 20% above the values recorded just before induction of anesthesia. Lower COR values in the maintenance phase for systolic BP were 27% +/- 9% below preoperative, and 31% +/- 11% below preinduction values. For HR, upper and lower COR values in the maintenance phase were 53% +/- 44% above and 38% +/- 17% below preinduction values, respectively. Transgressions of COR values for BP and HR were common, treatment frequent, and redefinition of COR values rare. CONCLUSION: Clinicians recognize ranges for vital signs during uneventful anesthesia. These CORs may differ from one stage of anesthesia to the next. Transgressions of these ranges are common. Not all transgressions are treated.

Adolescent↗
PubMed1993

Perioperative monitoring with pulse oximetry and late postoperative cognitive dysfunction.

In a randomized, blinded clinical study, we have used objective and subjective measures to determine if perioperative monitoring with pulse oximetry--by virtue of its potential to lessen hypoxaemia--would decrease late postoperative cognitive dysfunction. We investigated 736 adult patients undergoing elective procedures (other than cardiac, neurosurgical or for cancer) under regional or general anaesthesia, allocated randomly to undergo (group I) or not to undergo (group II) pulse oximetry monitoring in the operating theatre and recovery room. Cognitive function was evaluated using the Wechsler memory scale (WMS) and continuous reaction time (RT) test the day before surgery, and on the 7th day after operation or at discharge if that occurred before postoperative day 7. A questionnaire sent 6 weeks after surgery elicited patients' subjective perceptions regarding cognitive abilities. There were no significant differences between the two groups in either the total WMS score, the score for each WMS subtests or RT test. The questionnaire revealed that 7% in group I and 11% in group II believed cognitive abilities had decreased (ns). For the 40 patients whose WMS scores were 10 points less after than before operation, a follow-up study was undertaken 3 months after surgery. At that time, the median WMS score had returned to the preoperative value. We conclude that, for these 736 patients, subjective and objective measures did not indicate less postoperative cognitive impairment after perioperative monitoring with pulse oximetry.

Adolescent↗
PubMed1993

[Anesthesia simulators and training devices].

Simulators and training devices are used extensively by educators in 'high-tech' occupations, especially those requiring an understanding of complex systems and co-ordinated psychomotor skills. Because of advances in computer technology, anaesthetised patients can now be realistically simulated. This paper describes several training devices and a simulator currently being employed in the training of anaesthesia personnel at the University of Florida. This Gainesville Anesthesia Simulator (GAS) comprises a patient mannequin, anaesthesia gas machine, and a full set of normally operating monitoring instruments. The patient can spontaneously breathe, has audible heart and breath sounds, and palpable pulses. The mannequin contains a sophisticated lung model that consumes and eliminates gas according to physiological principles. Interconnected computers controlling the physical signs of the mannequin enable the presentation of a multitude of clinical signs. In addition, the anaesthesia machine, which is functionally intact, has hidden fault activators to challenge the user to correct equipment malfunctions. Concealed sensors monitor the users' actions and responses. A robust data acquisition and control system and a user-friendly scripting language for programming simulation scenarios are key features of GAS and make this system applicable for the training of both the beginning resident and the experienced practitioner. GAS enhances clinical education in anaesthesia by providing a non-threatening environment that fosters learning by doing. Exercises with the simulator are supported by sessions on a number of training devices. These present theoretical and practical interactive courses on the anaesthesia machine and on monitors. An extensive system, for example, introduces the student to the physics and clinical application of transoesophageal echocardiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesiology↗
PubMed1993

Future areas for recommendations.

In the future we may anticipate continued efforts to define standards addressing anaesthesia equipment, organization, and the qualification of personnel. Many standards will be revised and/or expanded, as experience with these standards accumulates. In addition to these external standards, we foresee efforts to seek consensus among clinicians on the definition of appropriate clinical patterns. In the long run, these efforts to define practice guidelines may lead to re-assessment of what and how we teach newcomers to anaesthesia, and how to assess the quality of anaesthesia care.

Anesthesiology↗
PubMed1993

Technology and the growth of anaesthesiology as a specialty.

Clinical monitoring techniques have affected patients, influenced other specialties; and changed the specialty of anaesthesia. Patients now fare better, the progress of surgery has been facilitated, and anaesthesiology itself has felt the impact of these developments. Technological advance stimulates our understanding of physiological processes, which is a foundation for progress yet to come. The complexity and abundance of equipment threatens to overwhelm the modern anaesthesiologist, a problem now being addressed without risk to patients by using simulators in training. By extrapolation from the last 30 years of progress, prospects in the specialty are breathtaking, though much needs to be done, particularly in countries struggling to advance anaesthesiology in the face of severe restrictions in personnel and resources.

Anesthesiology↗
PubMed1991

Comparative effects of cuff size and tightness of fit on accuracy of blood pressure measurements.

To determine the effect of snugness of cuff wrap on the accuracy of blood pressure (BP) measurements, we performed two studies on 6 healthy volunteers. In both studies, control values were obtained from the right upper arm with cuffs of appropriate size and snug fit. Study 1 had two phases. In the first, cuffs of appropriate size were wrapped snugly around the upper left arm of seated subjects. The effects of two other degrees of cuff snugness on the measurement of BP were evaluated by placing a filled 250-mL intravenous fluid bag between the cuff and arm over the triceps, measuring BP, then draining the same bag of half its contents and then all of its contents without rewrapping the cuff ("loose," "very loose" fit), each time measuring BP. The second phase of study 1 was identical in procedure, except that the cuffs used on the left arm were one size too small. In study 2, the experimental cuffs were placed just above the right ankle. To alter the signal-to-noise ratio, BP was raised or lowered: the standing position elevated mean BP by an average of 90 mm Hg, and elevation of the legs decreased mean BP by an average of 43 mm Hg. In study 1, we found that appropriately sized cuffs, whether wrapped tightly or loosely, gave correct BP readings. Cuffs snugly wrapped, but too small for the subject, gave high BP readings, on the average by approximately 10 mm Hg. Loose wrapping of small cuffs gave variable results in individual subjects that exaggerated systolic BP from 2 to 80 mm Hg. In study 2, elevating the legs or standing decreased or increased BP consistently. Loose wrapping of appropriately sized cuffs around the ankles of the subjects had no additional significant effect on BP.

Ankle↗
PubMed1991

The automated anesthesia record.

The handwritten anesthesia record requires the attention of the anesthesiologist. During critical moments, however, the anesthesiologist may be too busy to record data by hand; handwritten records, therefore, can be inaccurate. The volume of data that must be monitored during anesthesia today makes it impossible to record data by hand often enough to enable a meaningful review of the anesthetic procedure. Automated systems, therefore, are required for the correct capture of intraoperative data; such systems are now becoming available.

Anesthesia↗
PubMed1990

Monitoring for disconnection: ventilators with bellows rising on expiration can deliver tidal volumes after disconnection.

Anesthesia ventilators with bellows that rise on expiration (standing bellows) are favored over ventilators with bellows that descend during expiration (hanging bellows). Standing bellows will not rise if there is a disconnection, and thus they facilitate detection of disconnections. Yet, during a disconnection of ventilators with standing bellows, mechanical inspiration compresses the empty bellows beyond its resting position; with expiration the elastic bellows recoils and aspirates up to 140 ml, depending upon the fresh gas flow. Tidal volumes recorded after disconnection ranged from 50 to 140 ml (mean, 112.2 +/- 9.22 [SD]) at adult settings and from 55 to 90 ml (mean, 69.8 +/- 4.28 [SD]) at pediatric settings. Thus, spirometers that measure tidal volume (VT) in the expiratory limb of the breathing system may falsely indicate an expiratory VT after a disconnection of the breathing system at the Y-piece or the endotracheal tube. Existing low-pressure alarms and capnography alarms provide redundant warning of disconnection, however, should the ventilator continue to deliver small VTs after a disconnection.

Air Pressure↗
PubMed1990

Work and rest cycles in anesthesia practice.

A questionnaire inquiring about existing and desirable work and rest patterns appeared in a newsletter mailed to about 22,000 anesthesiologists and anesthesiology residents and 24,000 nurse anesthetists (CRNA). Almost 3,000 anonymous replies were received and analyzed. Respondents reported mean work weeks of 47.5 h (CRNA) to 69.8 h (residents), longest continuous period of administering anesthesia without a break of 6.6 h (CRNA) to 7.7 h (residents), and longest period of administering anesthesia with or without breaks of 14.1 h (CRNA) to 20 h (resident). However, the respondents considered it safe to administer anesthesia without a break for 4.2 (CRNA) to 5.2 h (anesthesiologists) and with break for 12.8 h (CRNA) to 15 h (residents). A substantial number of respondents believed that they work at least occasionally beyond their perceived self-limitations. The majority of respondents recalled having made errors in the administration of anesthesia that they attributed to fatigue. These results may not be representative of work patterns or attitudes among American anesthesia providers because of the small sample size and the resultant potential for bias. Yet, the subject deserves attention and further study because fatigue can affect professional performance, ability to learn, and family life.

Anesthesiology↗
PubMed1989

The uses of the anesthesia record.

The typical, handwritten anesthesia record of the 1980s does not satisfy its many users. The document is used for clinical care by the anesthetist, nurses, physicians, and technicians in postanesthesia, intensive, and postoperative surgical care units; for historical information by the billing officer, the statistician, and the anesthetist in preparation for a future anesthetic; and for the review of the quality of care by clinical peers and lawyers. For all of these users the typical record contains some to much unnecessary information and lacks some to much needed information. Electronic capture, storage, retrieval, and formatting of data can generate electronic displays or paper records tailored to answer the needs of specific users. The anesthetist in particular will benefit from a well-designed system that takes the place of the traditional handwritten anesthesia record.

Anesthesiology↗
PubMed1989

Sampling intervals for clinical monitoring of variables during anesthesia.

Although five minutes is the sampling interval mentioned by the American Society of Anesthesiologists for monitoring blood pressure and heart rate during anesthesia, most patients are monitored more closely by continuous auscultation and with the help of automated instruments. Yet this difference between the interval recommended and that actually used indicates that sampling intervals are not defined clearly enough. Therefore, we present three methods with which to determine sampling intervals during monitoring. To explore the feasibility of these methods we examined data gathered every 7.5 seconds during three typical, noncatastrophic physiologic perturbations induced in an anesthetized dog. We chose hypercapnia secondary to rebreathing, hypotension secondary to deep anesthesia, and hypoxemia secondary to a low concentration of inspired oxygen as realistic examples of what can occur during operation and anesthesia. We studied three variables: respired carbon dioxide, femoral arterial blood pressure, and oxygen saturation of hemoglobin (pulse oximeter). The data obtained during monitoring were subjected to three methods of analysis: (1) recording of sets of data, with various starting times, at five-minute intervals only (moving grid); (2) Fourier analysis; and (3) analysis of slopes. For the data of the experiment, the Fourier analysis yielded, on average, longer sampling intervals than did the analysis of slopes.

Anesthesia, General↗
PubMed1989

Modern trends in monitoring in anaesthesia: its benefits and costs.

Many monitoring devices, including peripheral arterial catheters, multichannel electrocardiographs, pulmonary artery catheters, capnographs, and pulse oximeters, have vied for acceptance in modern operating rooms. Considerable costs are associated with the use of these monitors. These costs are not limited to the purchase price of the equipment, but extend to the cost of any complications. The use of new equipment is fostered by the belief that new monitors improve the care of patients. However, for some invasive monitoring modalities, it is difficult to demonstrate clinical benefit.

Anesthesia↗