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K K Tremper

Publications and source records attributed to K K Tremper.

At least 55 records · Page 3Linked to original sources
PubMed1989

Changes in cardiac output after acute blood loss and position change in man.

Thoracic bioimpedance cardiac output (Qtbi) was measured at 1-min intervals in 27 volunteers before, during, and after withdrawing 500 ml (3.7 to 8.5 ml/kg; mean 5.8) of blood. The effects of passive leg raising (PLR) and standing on Qtbi were measured before and after blood withdrawal. Arterial oxygen saturation (SaO2), transcutaneous oxygen tension (PtcO2), mean arterial BP (MAP), and heart rate (HR) were also measured before and after blood withdrawal. Thoracic bioimpedance cardiac index (CI) decreased 18% (0.8 +/- 0.1 L/min.m2, p less than .0001) and stroke volume index (SI) decreased 22% (14.8 +/- 2.7 ml/beat.m2, p less than .0001) after blood withdrawal. HR, MAP, SaO2, and PtcO2 were not significantly different after blood withdrawal. Before blood withdrawal PLR increased CI 6.8% (0.3 +/- 0.1 L/min.m2, p less than .0001); after blood withdrawal PLR increased CI 11.1% (0.4 +/- 0.1 L/min.m2, p less than .0001). PLR can increase stroke volume and cardiac output in hypovolemic humans.

Acute Disease↗
PubMed1989

Thoracic bioimpedance and Doppler cardiac output measurement: learning curve and interobserver reproducibility.

Nine previously untrained health professionals learned to measure cardiac output (Qt) by suprasternal continuous-wave Doppler ultrasound (QtDopp) and by thoracic bioimpedance (Qtbi). Each received standardized written, videotaped, and individual instruction. First the novice, then the reference examiner, measured QtDopp or Qtbi in triplicate in an adult male subject. The reference examiner was blind to the novice measurements and the novice was not informed of the reference measurements. Each novice repeatedly measured QtDopp or Qtbi in different subjects until the mean novice QtDopp or Qtbi was within 10% of the corresponding mean reference measurement in three of four consecutive subjects. The novice observers required an average of 12.9 +/- 3.5 trials to learn to measure QtDopp, and an average of 8.4 +/- 4.5 trials to learn to measure Qtbi. The likelihood of novice agreement with the reference improved with experience. The same degree of intraobserver variability as reported for Qt measured by thermodilution (coefficient of variance less than or equal to 10%) was achieved with Qtbi in 150 (99%) of 152 triplicate measurements and QtDopp in 216 (97%) of 222 triplicate measurements. More importantly, interobserver agreement (within 10%) was achieved with both Qtbi and QtDopp. Reproducible noninvasive Qt measurement will allow these techniques to be used to monitor trend changes in Qt.

Cardiac Output↗
PubMed1989

Pulse oximetry.

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History, 20th Century↗
PubMed1988

Comparison of three oxygen monitors in detecting endobronchial intubation.

Rapid and reliable detection of inadvertent endobronchial intubation is an essential function of oxygen monitoring. We have studied the detection of this event by using three oxygen monitoring techniques: pulse oximetry, transcutaneous measurement of oxygen tension, and intraarterial fiberoptic measurement of oxygen tension. Four dogs were anesthetized, intubated, and monitored with these three techniques and with arterial and central venous cannulas. Endotracheal tubes were moved from the trachea into the right mainstem bronchi at several inspired oxygen fraction (FIO2) values for each dog, and the responses of the oxygen monitors were recorded for 20 minutes thereafter. The pulse oximeter showed little change in oxygen saturation (SpO2) during endobronchial intubation at FIO2 values above 0.3. SpO2 decreased by an average of 1.3 +/- 2.1% at an FIO2 of 1.0 and by 4.0 +/- 4.1% at an FIO2 of 0.5. Simultaneously measured transcutaneous oxygen tensions decreased by 42 to 64% and the optode reading decreased by 64 to 79%. At lower FIO2 values, the changes in SpO2 were more significant: a decrease of 6.0 +/- 6.3% at an FIO2 of 0.3 and of 9.8 +/- 6.1% at an FIO2 of 0.2. The transcutaneous oxygen and optode readings decreased by 31 to 45% under these conditions. Endobronchial intubations at FIO2 values greater than 0.3 may not yield immediate decreases in arterial saturation and hence may go undetected by pulse oximetry. Transcutaneous oxygen tension decreases significantly with endobronchial intubation at any FIO2. The experimental, intraarterial optode consistently yielded the greatest changes with the fastest time response.

Anesthesia, Inhalation↗
PubMed1988

Acute cardiovascular response to passive leg raising.

Cardiac output by thoracic bioimpedance, heart rate, BP, oxygen saturation, and transcutaneous oxygen tension were measured at 1-min intervals in 45 patients before and after passive leg raising (PLR). Mean cardiac index increased only 0.09 +/- 0.02 (SEM) L/min.m2 (p less than .001), mean transcutaneous oxygen tension increased 1.6 +/- 0.6 torr (p less than .01), and mean oxygen saturation decreased 0.5 +/- 0.2% (p less than .01) after PLR. There were no significant changes in heart rate or systolic BP. Seven (16%) patients had increased cardiac index greater than 10% after PLR.

Aged↗
PubMed1987

Continuous fiberoptic arterial oxygen tension measurements in dogs.

An experimental study using a new fiberoptic sensor for the continuous intraarterial measurement of oxygen tension is described. This "optode" sensor uses the phenomenon of fluorescence quenching to determine the oxygen tension of the surrounding medium. To assess the accuracy of this device, we anesthetized 4 dogs and monitored them continuously with arterial catheters and an intraarterial optode probe, and intermittently with arterial blood gas analysis. The inspired oxygen fraction was varied from 1.0 to 0.1, and arterial blood gases were measured for comparison with the optode reading. Two hundred ninety data sets yielded a correlation coefficient of 0.96, with a linear regression slope of 0.98 and intercept of 5.1 mm Hg. In the 72 data sets from the last dog, the bias and precision of the optode arterial oxygen tension values were -10.3 mm Hg and 20.0 mm Hg, respectively. The optode probe was easily inserted through a 20-gauge catheter and did not interfere with continuous arterial pressure measurement or blood sampling. This study suggests that the optode has great potential as a continuous, real-time monitor of arterial oxygen tension.

Animals↗
PubMed1987

Noninvasive monitoring of carbon dioxide: a comparison of the partial pressure of transcutaneous and end-tidal carbon dioxide with the partial pressure of arterial carbon dioxide.

This study compares two noninvasive techniques for monitoring the partial pressure of carbon dioxide (PCO2) in 24 anesthetized adult patients. End-tidal PCO2 (PetCO2) and transcutaneous PCO2 (PtcCO2) were simultaneously monitored and compared with arterial PCO2 (PaCO2) determined by intermittent analysis of arterial blood samples. PETCO2 and PtcCO2 values were compared with PaCO2 values corrected to patient body temperature (PaCO2T) and PaCO2 values determined at a temperature of 37 degrees C (PaCO2). Linear regression was performed along with calculations of the correlation coefficient (r), bias, and precision of the four paired variables: PETCO2 versus PaCO2 and PaCO2T (n = 211), and PtcCO2 versus PaCO2 and PaCO2T (n = 233). Bias is defined as the mean difference between paired values, whereas precision is the standard deviation of the difference. The following values were found for r, bias, and +/- precision, respectively. PETCO2 versus PaCO2: 0.67, -7.8 mm Hg, +/- 6.1 mm Hg; PETCO2 versus PaCO2T: 0.73, -5.8 mm Hg, +/- 5.9 mm Hg; PtcCO2 versus PaCO2: 0.87, -1.6 mm Hg, +/- 4.3 mm Hg; PtcCO2 versus PaCO2T: 0.84, +0.7 mm Hg, +/- 4.8 mm Hg. Although each of these PCO2 variables is physiologically different, there is a significant correlation (P less than 0.001) between the noninvasively monitored values and the blood gas values. Temperature correction of the arterial values (PaCO2T) slightly improved the correlation, with respect to PETCO2, but it had the opposite effect for PtcCO2. In this study, the chief distinction between these two noninvasive monitors was that PETCO2 had a large negative bias, whereas PtcCO2 had a small bias. We conclude from these data that PtcCO2 may be used to estimate PaCO2 with an accuracy similar to that of PETCO2 in anesthetized patients.

Adult↗
PubMed1987

The effect of carbon monoxide inhalation on pulse oximetry and transcutaneous PO2.

Five dogs were anesthetized, intubated, and ventilated with various mixtures of oxygen, nitrogen, and carbon monoxide. Each dog was monitored with arterial and pulmonary artery catheters, a transcutaneous PO2 analyzer, and two pulse oximeters. An IL-282 Co-oximeter was used to periodically measure arterial oxyhemoglobin (O2Hb) and carboxyhemoglobin (COHb) as percentages of the total hemoglobin. The PaO2, PaCO2, and pHa were measured in the same blood specimens using standard electrodes. When the inspired oxygen concentration was reduced in the absence of COHb, the pulse oximeter saturation (SpO2) estimated O2Hb with reasonable accuracy. COHb levels were then varied slowly from 0-75% in each dog. As the COHb level increased and oxyhemoglobin decreased, both pulse oximeters continued to read an oxygen saturation of greater than 90%, while the actual O2Hb fell below 30%. In the presence of COHb, the SpO2 is approximately the sum of COHb and O2Hb, and, thus, may seriously overestimate O2Hb. The pulse oximeter, as the sole indicator of blood oxygenation, should, therefore, be used with caution in patients with recent carbon monoxide exposure. On the other hand, transcutaneous PO2 falls linearly as COHb increases, and reaches about one-fifth of its initial value at the highest COHb levels despite the maintenance of constant arterial PO2.

Animals↗
PubMed1987

Transcutaneous oxygen measurement: experimental studies and adult applications.

Transcutaneous PO2 sensors have been developed over the past ten years from the same basic electrodes used in conventional blood-gas machines. The skin is heated to enable the skin surface sensors to respond quickly to the gas tensions beneath them. PtcO2 is a variable that reflects the PO2 in the peripheral tissue. PtcO2 has its own range of normal values, and it responds to cardiopulmonary changes that affect tissue oxygenation. In most patients, those without decreased cardiac output, PtcO2 follows the trend of PaO2 and decreases relative to PaO2 with increasing patient age (see Table 2). In the presence of severely reduced cardiac output and peripheral perfusion, the PtcO2 values will deviate from their relationship with the arterial tensions and become blood flow dependent, thus providing quantitative information regarding blood flow. The technique of PtcO2 monitoring likely will gain wider acceptance because it is a noninvasive and continuous monitor that provides useful information regarding tissue oxygenation.

Adult↗
PubMed1987

Pulse oximetry: applications and limitations.

The pulse oximeter estimates arterial hemoglobin saturation by measuring the light absorbance of pulsating vascular tissue at two wavelengths. The relationship between measured light absorbances and saturation was developed empirically and is built into the oximeter software. Studies in human volunteers have shown good performance of the device in healthy adults for saturations in the range of 70 to 100%. Studies in the operating room and intensive care unit have established its clinical accuracy and usefulness. The pulse oximeter has already found a number of clinical applications outside of the operating room, such as monitoring during patient transport, respiratory monitoring during narcotic administration, and evaluation of home-oxygen therapy. To use this monitor to its full potential, we must be aware of its limitations as well as its advantages. Because of the nature of the HbO2 dissociation curve, saturation measurements will not be sensitive to changes in PaO2 when the PaO2 is greater than 100 torr. This also implies that the pulse oximeter may fail to detect an inadvertent endobronchial intubation in the operating room. It may take minutes to detect an esophageal intubation in a well-preoxygenated patient. When desaturation does occur, the pulse oximeter detects it quickly, accurately, and reliably. Since the pulse oximeter uses two wavelengths of light, it cannot distinguish more than two hemoglobin species. Thus, COHb and MetHb will cause errors in SpO2 if present in large amounts. Intravenously administered dyes can also cause errors because of their absorbance properties, particularly methylene blue and indocyanine green. The pulse oximeter may be unable to detect an adequate signal during abnormal hemodynamic conditions. The pulse oximeter is one of the most important advances in noninvasive monitoring because it provides a means of continuously and quickly assessing arterial blood oxygenation. It is easy to use and interpret, requires little setup time, and poses no additional risks to the patient. Pulse oximetry may soon be a standard of practice for routine monitoring in any clinical setting in which the patient is at risk of hypoxemia.

Blood Gas Monitoring, Transcutaneous↗
PubMed1987

Cardiovascular effects of anesthesia and operation.

Anesthesia and surgery have a wide range of effects on the cardiovascular system. Even in healthy patients having minor operations, anesthetic agents can cause significant cardiac depression and hemodynamic instability. Virtually all anesthetic agents have intrinsic myocardial depressant properties, although some may mask this with sympathetic stimulation. The vasodilatory effects of the volatile agents can result in serious hypotension when combined with this negative inotropy. In the patient with pre-existing cardiac disease, these cardiovascular anesthetic effects become much more serious. These patients will not tolerate wide swings of hemodynamic variables, and the cardiodepressant effects of anesthetics are more pronounced in them. The stress of anesthesia and surgery frequently unmasks previously undiagnosed heart disease. Surgery itself provides many insults to the cardiovascular system, and these may be additive with the effects of anesthesia. These include loss of blood and other volume shifts, release of various substances into the circulation, hypothermia, sudden changes in cardiac preload and afterload, myocardial ischemia, and effects of drugs or blood products given for surgical reasons. The signs and symptoms of these surgical stresses to the cardiovascular system are often masked by anesthesia.

Anesthesia, Inhalation↗
PubMed1986

Effects of anesthetic agents on the drift of a transcutaneous oxygen tension sensor.

Both halothane and nitrous oxide can be reduced at the cathode of a polarographic oxygen electrode, causing the electrode current to drift upward and report falsely high oxygen tension. Because transcutaneous oxygen tension is measured by a heated oxygen electrode, there is a potential for significant upward drift of these values. To examine the clinical significance of this drift, the following study was performed. Transcutaneous oxygen tension sensors were calibrated at oxygen tensions of 0 mm Hg and 157 mm Hg (room air) just before clinical use during anesthesia. This calibration was rechecked immediately upon removal of the sensor from the patient at the end of the anesthesia. The predominant anesthetic agent used and the duration of monitoring were noted from the record. Data were collected from 208 patients representing a total of 463.6 hours of anesthesia. The patients were divided into five groups based on anesthetic administered: halothane, enflurane, isoflurane, nitrous oxide-narcotic, and local/regional. The mean zero point recalibration value was 0.4 mm Hg or less for all agents except halothane, for which it was 1.8 +/- 3.2 mm Hg. This halothane drift was significantly greater than that for the other agents (P less than 0.01). Room air recalibration was not significantly different in any of the five groups, varying from 160 +/- 4.9 mm Hg for halothane to 157 +/- 4.9 mm Hg for enflurane. All these drift values are within the manufacturer's specifications. We conclude that the drift of the transcutaneous oxygen tension sensor due to anesthetic agents is not clinically significant. However, caution should be exercised when halothane is used during an extremely long period of anesthesia.

Anesthetics↗