Biomedical subjects
Publications and source records attributed to J S Gravenstein.
Mass spectrometry of respired gases puts a powerful analytic tool into the hand of the clinician. However, serious misinterpretations may result if the principle of operation and certain weaknesses of spectrometry are not appreciated. The potential pitfalls of clinical mass spectrometry are related to the need to have one unit serve many patients and to the design of the spectrometer and its algorithms.
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We assessed the analgesic effectiveness of a single intramuscular injection of dezocine, 10 mg or 15 mg; morphine, 10 mg; or a placebo in 160 patients with moderate to severe postoperative pain. Dezocine, 10 mg, was as effective as and had approximately the same duration of action as morphine, 10 mg. Dezocine, 15 mg, was more effective than 10 mg of either dezocine or morphine as assessed by three efficacy scales (verbal and analog pain intensity and pain relief), and both drugs were significantly (p less than 0.05) more effective than placebo as assessed by the three efficacy scales and the overall evaluation of the investigator. A small percentage of patients suffered nausea and became sedated; the drugs and placebo, however, did not differ statistically with respect to the side effects. Blood pressure, heart rate, and respiratory rate generally were slightly decreased by both drugs.
In order to evaluate the possible physiologic significance of intra- and postoperative hypotension, we monitored arterial blood pressure and heart rate continuously for 36 hr starting the night before and ending the morning after operation in 34 gynecologic patients. The lowest pressures that occurred during physiologic sleep were compared with the lowest arterial pressures that occurred during anesthesia without deliberate hypotension. Two values were calculated: a preoperative baseline pressure, i.e., the average value recorded during the second hour of monitoring on the night before surgery, and a preanesthetic standard pressure, i.e., the average value of 15 consecutive measurements made at 1-min intervals in the operating room before the induction of anesthesia. The results indicate that a systolic pressure 10% below the PAS during anesthesia does not constitute physiologically significant hypotension because this range resembles the range that occurs spontaneously during unmedicated sleep or sleep aided with a mild hypnotic. These physiologic nadirs in blood pressure are assumed to be tolerated well by the patient. Intraoperative pressures in elderly patients frequently drifted below sleep-associated levels of blood pressure and may, therefore, constitute physiologically significant hypotension.
Anesthesia personnel of 15 southeastern academic departments reported significantly less use of marijuana and cocaine among their staffs than did a class of medical students describing their own use. The chairmen reported that between 1% and 2% of anesthesia personnel came to their attention because of drug or alcohol abuse. Of 44 persons known to abuse drugs or alcohol, seven were reported to have died secondary to abuse.
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When anesthesia made its triumphant entry more than 130 years ago, it established inhalation as a major and important route for the uptake of drugs. A brief review of the colorful history of medicinal inhalations shows that man has inhaled at least as long as written records exist, not only to sustain life but also to modify life.
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ECG monitoring during anesthesia detects many arrhythmias, even in healthy patients. The clinical significance of these arrhythmias is uncertain. However, a conservative analysis of the cost of ECG monitoring in the USA reveals that the prevention of cardiac arrests occurring in 1 of 3,500 cases is quite cost effective. Routine ECG monitoring for all anesthetics in the USA is recommended.
In 12 patients with heart disease, hypercarbia was induced for carotid endarterectomy. Anesthesia was maintained with nitrous oxide in oxygen and methoxyflurane. In addition to intra-arterial measurements of blood pressure, cardiac output, systolic time intervals (STI), and pressure time indices (PTI) were determined in order to assess cardiovascular responses in these patients. Internal carotid stump blood pressure was measured in five patients before and after induction of hypercarbia. Mild elevation of the Paco2 level affected systolic time intervals but not heart rate and blood pressure. When Paco2 levels reached 56 to 65 torr, systolic but not diastolic blood pressure rose significantly, heart rate and cardiac output increased, while the shortening in the preejection period (PEP), left ventricular ejection time (LVET), and the decrease in the PEP/LVET ratio signified increased mechanical cardiac activity. Hypercarbia caused intense sympathetic stimulation as demonstrated by twofold to threefold increases in plasma catecholamine levels. Stump blood pressure was elevated. Cardiac oxygen demand was significantly increased, while coronary filling time was shortened, as indicated by the increase in the tension time index and shortening in the diastolic time. This signified a relative myocardial underperfusion. Thus, while hypercarbia to levels of 66 to 70 torr increased internal carotid artery stump pressure, it also caused increased cardiac mechanical activity and concomitant unfavorable balance between myocardial oxygen consumption and supply. The measurement of STI and the computation of PTI provided early detection of alterations in cardiac function.
We hypothesized that telemedicine -- medicine practiced from a distance using telecommunications -- can solve some problems related to the scarcity and maldistribution of specialists in critical care medicine. Using a two-way audiovisual link between a small private hospital and a large university medical center, we have provided daily consultations by an intensivist to patients in the small institution. During the first 175 days of the project we found: 1) regular consultations in critical care can be provided using the audiovisual link; 2) current technology is adequate but expensive; 3) telemedicine consultations can be made acceptable to users and providers; 4) telemedicine can be a valuable educational resource; 5) telemedicine can influence the process and probably the outcome of patient care; 6) the audiovisual link is superior to the telephone for these consultations; and 7) telemedicine can serve as an important link between a small hospital and a large medical center favorably influencing the quality of care in the critical care unit of the small hospital.
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Twenty-four patients with severe, 24 with moderate, and 24 without heart disease were selected for measurements of systolic time intervals (STI) and blood pressure before and during anesthesia. In all patients anesthesia was induced with thiopental, 4 mg/kg. After tracheal intubation, 12 patients from each heart-disease class received halothane-N2O-O2 (halothane) and 12 patients from each class morphine-d-tubocurarine-N2O-O2 (MS-dTc). Thiopental increased the pre-ejection period (PEP), decreased left ventricular ejection time (LVET), and accelerated heart rate (HR). These changes were similar in patients with and without heart disease. Halothane and and MS-dTc lowered systolic blood pressure and increased PEP/LVET. With halothane but not with MS-dTc these changes were more pronounced in patients who had heart disease. Changes of the PEP/LVET ratio during halothane anesthesia were a better discriminating variable among patients without, with moderate, and with severe heart disease than were changes in systolic blood pressure.
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