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Biomedical subjects

K K Tremper

Publications and source records attributed to K K Tremper.

At least 19 recordsLinked to original sources
PubMed1991

Effects of anemia on pulse oximetry and continuous mixed venous hemoglobin saturation monitoring in dogs.

The accuracy of pulse oximetry (for pulse hemoglobin oxygen saturation [SpO2]) and mixed venous oximetry (for mixed venous hemoglobin oxygen saturation [SvO2]) was assessed during progressive normovolemic anemia in dogs. Splenectomized mongrel dogs under general anesthesia were monitored with a three-wavelength pulmonary artery oximeter catheter (10 dogs) and a pulse oximeter (11 dogs). Data were collected while fractional inspired oxygen concentration (FIO2) was varied from 1.00 to 0.05 in seven steps. The dogs then underwent isovolemic hemodilution, and the FIO2 was again varied. This sequence continued until data no longer could be obtained. The accuracy of each device was assessed by determining the bias (the average difference between the continuous monitor oximeter and the bench oximeter) and the precision (the standard deviation of the difference). For the three-wavelength Oximetrix catheter (for hemoglobin oxygen saturation denoted here SoxO2), the overall bias (SoxO2 - SvO2) and precision were -0.7 +/- 8.6% for the 193 data points. The accuracy as assessed by bias and precision for SoxO2 was similar for hematocrits of 40-15%. (Bias +/- precision was 2.1 +/- 5.7% for hematocrits greater than 40%, and -1.1 +/- 7.5% for hematocrits of 15% to 19%). At hematocrits between 10 and 14%, the precision worsened to 12%, and for hematocrits less than 10% the bias +/- precision was -11.5 +/- 11.8%. The overall SpO2 accuracy was 0.2 +/- 7.6% for 178 points. The pulse oximeter's accuracy was similar, down to hematocrits of 10%. Below 10%, the bias and precision worsened to -5.4 +/- 18.8%.(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia↗
PubMed1991

Hyperventilation reduces transcutaneous oxygen tension and skin blood flow.

Transcutaneous oxygen tension (PtcO2) is often used to monitor neonates and infants in special care units and the operating room. The transcutaneous index (TCI = PtcO2/arterial oxygen tension [PaO2]) is known to depend both on age and on cardiac index but is assumed to be independent of other physiologic variables. In this study we have shown that TCI also depends upon arterial carbon dioxide tension (PaCO2). Five young pigs were anesthetized and paralyzed and their lungs mechanically ventilated while they were monitored with PtcO2 electrodes and serial arterial blood gas analyses. For a 45 degrees C PtcO2 sensor, the mean TCI during normocapnia was 0.78, whereas during hyperventilation (PaCO2 = 20 mmHg) the mean TCI was reduced 65%, to 0.27. The corresponding TCI values for a 43 degrees C sensor were 0.33 and 0.065, representing an 80% decrease in TCI during hyperventilation. Hypoventilation had little effect upon TCI as long as hypoxemia was avoided. Twelve awake adult volunteers with radial artery cannulas were monitored with PtcO2 sensors at several body sites and two sensor temperatures. For a 44 degrees C sensor on the chest, the mean TCI decreased from 0.77 at normocapnia to 0.60 at a PaCO2 of 17 mmHg, a 22% change. For the same sensor on the foot, TCI decreased from 0.63 to 0.32, a 49% change. For a 42 degrees C sensor under the same conditions, the corresponding TCI decreases were 51 and 64%. Six of the volunteers were also monitored with laser-Doppler skin blood flow probes located on the chest, hand, and foot.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Comparison of changes in transit time ultrasound, esophageal Doppler, and thermodilution cardiac output after changes in preload, afterload, and contractility in pigs.

The purpose of this study was to compare how well changes in cardiac output (CO) measured by esophageal Doppler (Doppler) and thermodilution (TD) followed changes in CO measured by transit time ultrasound (TTU). Simultaneous Doppler, TD, and TTU measurements of CO were made before and after changes in preload, afterload, or contractility in seven piglets. Mean changes in each CO method for each type of change in CO were compared by analysis of variance. Changes in TTU CO, TD CO, and Doppler CO were compared by correlation, linear regression, and bias and precision statistics. Of 86 TTU changes in CO greater than 10%, Doppler changed the same direction as TTU 59 times, changed in an opposite direction 6 times, and changes less than 10% 21 times. Thermodilution changed in the same direction as TTU 72 times, in the opposite direction 4 times, and changed less than 10% 10 times. Changes (% delta) in TTU and TD measurements of CO were not significantly different in any group. Changes in Doppler CO and TTU CO were different for two afterload and contractility groups. Percent changes in Doppler CO had a correlation coefficient (r) = 0.74, m = 0.72, and bias (mean % delta Doppler CO - mean % delta TTU CO) = 6.3 +/- 29.7 with % delta TTU CO. Percent changes in TD CO had an r = 0.90, m = 0.92, and bias = 5.7 +/- 19.1 with % delta TTU CO. Cardiac output measured by Doppler underestimated changes in CO due to changes in preload and contractility and exaggerated changes in CO due to changes in afterload.

Analysis of Variance↗
PubMed1990

Detection of venous air embolism by continuous intraarterial oxygen monitoring.

In a recent study, we compared a new intraarterial fiberoptic "optode" probe to continuously measure arterial oxygen and carbon dioxide tensions and pH with intermittently drawn blood samples in patients undergoing surgery. In one patient with a diagnosis of Arnold-Chiari type I malformation with outflow obstruction of the fourth ventricle, a major pulmonary air embolism occurred while the patient was undergoing suboccipital craniectomy and cervical laminectomy in the prone position. Three hours after the incision the optode-displayed oxygen tension decreased from a stable value of 225 +/- 8 mm Hg to 63 mm Hg over a 10-minute period. During the same interval, carbon dioxide tension increased and end-tidal carbon dioxide decreased; shortly thereafter, transcutaneous oxygen tension decreased also. Within 20 minutes after the inspired gas mixture was changed to 100% oxygen, the patient's respiratory variables returned to near baseline. No further complications ensued. This is the first time continuously monitored arterial oxygen tension values during a pulmonary embolism have been reported. With further refinement, intraarterial optode probes will add another valuable method of detecting pulmonary air embolism.

Adult↗
PubMed1990

Noninvasive cardiac output: simultaneous comparison of two different methods with thermodilution.

The authors attempted to simultaneously measure cardiac output by thermodilution (COtd), thoracic bioimpedance (CObi), and suprasternal Doppler ultrasound (COdopp) in 68 patients. Subgroups separately compared included patients whose lungs were mechanically ventilated, patients undergoing cardiac surgery, aortic surgery, patients with dysrhythmias, and patients with sepsis. The authors also studied the value of the ventricular ejection time (VET) in evaluating the agreement of CObi and COdopp with COtd. Simultaneous CObi and COtd were available in a total of 56 patients (416 data sets) with an overall correlation coefficient r = 0.61, regression slope (m) of 0.52, intercept (y) of 2.46, and mean (CObi-COtd) difference (bias) of -0.67 +/- 1.72 (SD) l/min. Simultaneous COdopp and COtd were available in 59 patients (446 data sets) with an overall r = 0.51, m of 0.53, y of 2.05, and bias of -0.79 +/- 1.95 l/min. CObi agreed most closely with COtd in patients whose lungs were mechanically ventilated, who had not undergone cardiac or aortic surgery, and with VET difference less than 40 ms (16 patients, 99 data sets; r = 0.74; m = 0.97; y = 0.15; bias = -0.02 +/- 1.53 l/min). COdopp agreed most closely with COtd in patients whose lungs were mechanically ventilated, who had not undergone cardiac or aortic surgery, and in sinus rhythm with VET difference less than 40 ms (10 patients, 45 data sets; r = 0.82; m = 0.98; y = -0.07; bias = -0.82 +/-1.03 l/min). VET by radial artery can help evaluate the reliability of CObi and COdopp.

Aorta↗
PubMed1989

Pulse oximetry for monitoring during ward analgesia: epidural morphine versus parenteral narcotics.

A pulse oximeter was used to monitor oxygen saturation in 20 women following cesarean delivery. The patients were randomly assigned to one of two groups. Group A received conventional parenteral narcotics for relief of postoperative pain and group B received epidural morphine. All patients were monitored overnight, and data were stored continuously. There were no statistically significant differences in the low saturation values between the two groups. However, the group A desaturation episodes occurred an average of 2.7 +/- 1.9 hours after the parenteral narcotics were administered, and the group B desaturation episodes occurred an average of 13.7 +/- 5.9 hours after the epidural morphine was administered.

Adult↗
PubMed1989

Pulse oximetry.

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Anesthesiology↗
PubMed1989

Effects of methemoglobinemia on pulse oximetry and mixed venous oximetry.

The performance of three commercially available pulse oximeters was assessed in five anesthetized dogs in which increasing levels of methemoglobin were induced. Hemoglobin oxygen saturation in each dog was monitored with three pulse oximeters (Nellcor N-100, Ohmeda 3700, and Novametrix 500) and a mixed venous saturation pulmonary artery catheter (Oximetrix Opticath). Arterial and mixed venous blood specimens were analyzed for PaO2, PaCO2, and pHa using standard electrodes. An IL-282 Co-oximeter was used on the same specimens to determine oxyhemoglobin and methemoglobin as percentages of total hemoglobin. Methemoglobin levels of up to 60% were induced by intratracheal benzocaine. As MetHb gradually increased while the dogs were breathing 100% inspired oxygen, the pulse oximeter saturation (SpO2) overestimated the fractional oxygen saturation (SaO2) by an amount proportional to the concentration of methemoglobin until the latter reached approximately 35%. At this level the SpO2 values reached a plateau of 84-86% and did not decrease further. When, at fixed methemoglobin levels, additional hemoglobin desaturation was induced by reducing inspired oxygen fraction, SpO2 changed by much less than did SaO2 (regression slopes from 0.16 to 0.32). Thus, at high methemoglobin levels SpO2 tends to overestimate SaO2 by larger amounts at low hemoglobin saturations. Plots of SpO2 versus functional saturation (oxyhemoglobin/reduced hemoglobin plus oxyhemoglobin) show an improved but still poor relationship (regression slopes from 0.32 to 0.46). The Oximetrix Opticath pulmonary artery catheter behaves similarly but provides somewhat better agreement with functional saturation than do the pulse oximeters in the presence of methemoglobinemia. Pulse oximetry data (SpO2) should be used with caution in patients with methemoglobinemia.

Animals↗
PubMed1989

Transcutaneous and liver surface PO2 during hemorrhagic hypotension and treatment with phenylephrine.

Transcutaneous PO2 (PtcO2) and liver surface PO2 (PIO2) were measured in six mongrel dogs during hemorrhagic shock, normotensive shock, and volume resuscitation. Normotension was produced during extreme hypovolemia by an infusion of phenylephrine. PtcO2 and PlO2 were compared to each other and to hemodynamic and oxygen transport variables. PtcO2 and PlO2 correlated well with cardiac index (CI) r = .71 and .86, respectively; n = 60) and with each other (r = .79; n = 60). Heart rate, mean arterial pressure (MAP), and PaO2) correlated less with PtcO2 or PlO2. During the normotensive shock period, PtcO2, PIO2, CI, oxygen delivery (DO2), and oxygen consumption (VO2) were all severely decreased, while PaO2 and MAP were normal and lactic acid concentrations were elevated. It was concluded that PtcO2 follows changes in PlO2 during hypotensive and normotensive low cardiac output shock in mongrel dogs. Low PtcO2 values are associated with low values of PlO2, DO2, VO2, and rising lactic acid concentrations in dogs. These animal data imply that low PtcO2 values encountered in clinical monitoring during anesthesia and surgery may correspond to decreased blood volume, blood flow, and PlO2.

Animals↗
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↗