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Biomedical subjects

P L Appel

Publications and source records attributed to P L Appel.

At least 37 records · Page 2Linked to original sources
PubMed1991

The relationship between ARDS, pulmonary infiltration, fluid balance, and hemodynamics in critically ill surgical patients.

Hypervolemia from fluid overload with resultant pulmonary edema is thought to be a frequent cause of Adult Respiratory Distress Syndrome (ARDS). However, ARDS may also occur as a result of the hypovolemic shock of surgery or trauma. To develop an appropriate rationale for fluid therapy in high-risk surgical patients, the relationship between fluid balance, hemodynamics, the onset of ARDS by physiologic criteria (shunt greater than or equal to 20%, and/or PaO2/FiO2 ratio less than 250) and the onset of pulmonary infiltration (PI) associated with ARDS were examined. Fifty patients were prospectively followed from admission throughout their hospitalizations; 38 (76%) had trauma and 12 (24%) were postoperative. Cardiac index, central venous pressure (CVP), wedge pressure (WP), and shunt (Qsp) were measured. All chest x rays were read by one staff radiologist who was blinded to the patients' identities. PI was graded from "0" to "4" (0 = no PI, 4 = maximum PI). The first x ray reading of "2" or greater was used as the time of onset of PI. ARDS by physiologic criteria occurred in 29 of 50 (58%) patients; 27 of these 29 (94%) also developed +2 or greater PI. The mean onset times of ARDS and of +2 PI were 40 +/- 41 hours and 40 +/- 38 hours, respectively. The ARDS patients had a significantly smaller net positive fluid balance than the non-ARDS patients over the first 40 hours after admission (+6,831 ml +/- 4,909 ml vs 12,440 ml +/- 7,817 ml, (P less than 0.01)).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

The efficacy of central venous and pulmonary artery catheters and therapy based upon them in reducing mortality and morbidity.

The purpose of this study was to (1) evaluate the relative cost effectiveness of the central venous pressure and flow-directed pulmonary artery catheters used to maintain normal hemodynamic values as therapeutic goals in the control groups vs supranormal values empirically observed in critically ill postoperative survivors in the protocol groups, and (2) to evaluate tissue perfusion and oxygenation in relationship to organ failure and mortality. In two prospective clinical trials there were no significant differences in outcome between the central venous pressure and pulmonary artery control groups that used normal values as therapeutic goals. However, there were marked and significant reductions in morbidity and mortality of the protocol groups using the supranormal cardiac index, oxygen delivery, and oxygen consumption values as goals. The cumulative oxygen debt was less and organ failures were fewer and less severe in the protocol groups than in the control groups.

Cardiac Output↗
PubMed1990

Measurement of tissue perfusion by oxygen transport patterns in experimental shock and in high-risk surgical patients.

Survivors of high-risk general (noncardiac) surgery were observed to have cardiac index (CI) values averaging 4.5 l/min.m2, oxygen delivery (DO2) of greater than 600 ml/min.m2, and oxygen consumption (VO2) of 170 ml/min.m2. In contrast, these values were relatively normal in patients who subsequently died. A very early predictive index based on these observations was found to predict outcome in 94% of high-risk patients. The hypotheses that increased DO2 and VO2 in the survivors represent compensatory physiologic responses and that these values were appropriate therapeutic goals were tested in prospective randomized clinical trials and found to reduce mortality and morbidity significantly. The optimal goals were more easily attained with colloids, red cells, dobutamine, and vasodilators, according to their capacity to improve tissue perfusion, as reflected by increased flow and oxygen transport. The extremely complex interactions between DO2 and VO2 are reviewed.

Animals↗
PubMed1990

Therapy of shock based on pathophysiology, monitoring, and outcome prediction.

High-risk patients who survived general (noncardiac) surgery were observed to have cardiac index (CI) values averaging 4.5 L/min.m2, oxygen delivery (DO2) greater than 600 ml/min.m2, and oxygen consumption (VO2) 170 ml/min.m2 during the first 2 or three days postoperatively. Patients who subsequently died maintained relatively normal CI, DO2, and VO2 values in this period. Values of other variables in survivors and nonsurvivors were not appreciably different. An index based on these observations correctly predicted outcome in 94% in a subsequent prospective study. Two hypotheses: a) that increased flow and oxygen transport represent compensatory physiologic responses to an earlier tissue oxygen debt, and b) that these survivors' values were appropriate therapeutic goals, were tested in prospective randomized clinical trials. The protocol group attained those therapeutic goals. This resulted in significantly reduced mortality and morbidity. Optimal goals were more easily attained with colloids, red cells, and an inotropic agent, dobutamine. Dobutamine was used because, in a prospective crossover clinical trial with dopamine at various doses, dobutamine produced greater increases in flow and flow-related variables. More importantly, it improved tissue perfusion as reflected by greater increases in VO2 and greater reductions in pulmonary and systemic vascular resistance.

Blood Volume↗
PubMed1989

Prediction of below-knee amputation wound healing using noninvasive laser Doppler velocimetry.

Preoperative laser Doppler velocimetry (LDV) measurements of calf and brachial skin perfusion were performed in 29 patients prior to undergoing below-knee amputation; dual calf measurements on the anterior and posterior skin flaps were routinely obtained. Patients' ages ranged from 24 to 83 years; 16 had diabetes, 13 were smokers, 6 had hypertension, and 2 had known coronary artery disease. Anterior and posterior calf LDV values greater than or equal to 20 mV were associated with successful below-knee amputation wound healing in 25 of 26 patients; all 3 patients with either anterior or posterior calf LDV values less than 20 mV had below-knee amputations that failed to heal. Calculation of calf-brachial LDV indexes did not increase predictive accuracy compared to calf LDV measurements alone, although patients with wounds that failed to heal tended to have lower calf-brachial indexes. Preoperative noninvasive LDV may be used to aid in predicting the likelihood of successful healing after below-knee amputation.

Adult↗
PubMed1989

Diagnosis of traumatic thoracic aortic rupture: a 10-year retrospective analysis.

A 10-year retrospective analysis of 82 patients with suspected thoracic aortic rupture (TAR) due to blunt chest trauma was performed to define which symptoms and signs were helpful in making an early diagnosis. Symptoms and signs associated with TAR included midscapular back pain (in the absence of thoracic spine fracture), unexplained hypotension, upper extremity hypertension, bilateral femoral pulse deficits, and initial chest tube output in excess of 750 mL. Chest roentgenographic signs seen with significantly greater frequency in the 12 patients with TAR than in 70 patients without such rupture included a widened paratracheal stripe (7 patients), deviation of the nasogastric tube or central venous pressure line (5 patients), blurring of the aortic knob (9 patients), abnormal paraspinous stripe (6 patients), and rightward tracheal deviation (5 patients). Mediastinal widening of greater than 8 cm occurred in 11 of the 12 patients with TAR (sensitivity, 92%); its specificity, however, was only 10% (11 true-positive and 63 false-positive results). In patients in hemodynamically stable condition who display these findings, immediate aortography should be considered. The presence of myocardial contusions, intraabdominal injuries, and pelvic fractures also occurred more frequently in patients with TAR. We conclude that a detailed history, physical examination, and chest roentgenography, with rapid progression to aortography in suspicious cases, represent the safest and most reliable approach to patients with TAR.

Accidents, Traffic↗
PubMed1989

Testicular oximetry: a new method for the assessment of tissue perfusion and viability following torsion and detorsion.

This study evaluated the use of a polarographic surface PO2 electrode to assess testicular perfusion and viability following torsion and detorsion. Adult male Sprague-Dawley rats were divided into groups and subjected to unilateral testicular torsion and detorsion of varying degrees and durations. Rats subjected to sham torsion or 720 degrees torsion did not show significant decreases in testicular PO2 after 15 minutes, whereas those subjected to 1,080 degrees torsion or spermatic cord ligation uniformly decreased their testicular PO2 to 0 mm Hg within 10 minutes. Testicular PO2 values were similar in rats subjected to 60 minutes of 720 degrees torsion followed by detorsion and those undergoing 15 minutes of 1,080 degrees torsion and detorsion. Rats subjected to breathing 100% oxygen uniformly increased their testicular PO2 to an average of more than twice room-air values. However, rats subjected to 1,080 degrees torsion for 6 hours followed by detorsion did not increase their testicular PO2 when subjected to breathing 100% oxygen, whereas those subjected to 720 degrees torsion for 6 hours followed by detorsion did increase their testicular PO2 when subjected to breathing 100% oxygen. The latter rats did not show microscopic changes associated with acute testicular infarction, whereas the former did.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1989

Multisensor transcutaneous oximetric mapping to predict below-knee amputation wound healing: use of a critical Po2.

Preoperative transcutaneous oxygen tension (tcPo2) measurements of calf and brachial skin were performed on 40 patients before they underwent below-knee amputation (BKA); dual calf measurements on the anterior and posterior skin were obtained. Both anterior and posterior calf tcPo2 values were significantly lower in patients with unsuccessful wound healing after BKA compared to those with successful healing (p less than 0.01). Successful wound healing occurred in 50% (6/12) of patients with calf tcPo2 values less than 20 torr and in 96% (27/28) of patients with calf tcPo2 values greater than 20 torr. Calculation of a critical Po2 index (defined as the lesser of the anterior and posterior calf/brachial tcPo2 ratios) resulted in improved predictive accuracy; 100% (6/6) of patients with a critical Po2 index of 0.20 or less had unsuccessful wound healing after BKA, whereas 97% (33/34) of patients with a critical Po2 index greater than 0.20 had successful healing. The use of a critical Po2 index greater than 0.20 as predictive of successful healing after BKA was associated with a sensitivity, specificity, and overall accuracy of 100%, 86%, and 98%, respectively, compared to 82%, 86%, and 83%, respectively, by use of absolute calf tcPo2 values. In conclusion, multisensor transcutaneous oximetric mapping is an accurate method for predicting wound healing success after BKA. Measurement of both anterior and posterior calf tcPo2 should be performed; calf tcPo2 values less than 20 torr may indicate local ischemia, but ischemia should be confirmed by comparison of calf tcPo2 with brachial tcPo2 before the patient is denied BKA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Incidence, physiologic description, compensatory mechanisms, and therapeutic implications of monitored events.

We described 663 unanticipated monitored circulatory events in 247 high-risk surgical patients by simultaneous invasive and noninvasive hemodynamic and oxygen transport monitoring systems. Unanticipated monitored events were defined as sudden reductions (greater than 20%) in cardiac index (CI), PaO2, SaO2, transcutaneous PO2 (PtcO2), and PtcO2/PaO2 index, or decreases to the lower limits of satisfactory values, specifically: PaO2 less than 70 torr, SaO2 less than 95%, PtcO2 less than 50 torr, and PtcO2/PaO2 less than 0.6. Essentially, monitored events are the small variations superimposed on the overall physiologic patterns that describe the entire course of critical illnesses. Monitored events are described by their baseline values just before each event, at the nadir of the event, and at the recovery from the event. To simplify presentation of complex changes in many variables, the circulatory changes were evaluated in terms of cardiac, pulmonary, and peripheral perfusion functions. Common patterns of these monitored events and the incidence of these patterns in high-risk surgical patients were described. Before the unanticipated monitored event, there were normal or increased heart, lung, and perfusion functions in about three fourths of the events. At the nadir, cardiac functions decreased in about two thirds, perfusion decreased in over half, and lung function fell in only one quarter of the events. Recovery occurred with increased cardiac function in two thirds, improved perfusion in over half, and increased lung function in less than one fifth of these monitored events. Noninvasive and invasive hemodynamic and oxygen transport variables were measured simultaneously to evaluate compensatory and decompensatory patterns.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Gas Analysis↗
PubMed1989

Comparison of hemodynamic and oxygen transport effects of dopamine and dobutamine in critically ill surgical patients.

Hemodynamic and oxygen transport effects of dopamine and dobutamine were studied in a series of 25 critically ill postoperative general surgical patients by a prospective, randomized crossover design after maximal response to fluids had been obtained. Dopamine increased MAP, HR, CI, PvO2, DO2, and Qsp while decreasing PaO2. Dobutamine increased HR, CI, SI, stroke work, DO2, VO2, and Qsp while decreasing PAWP and SVRI and PVRI. In general, the effects of the two drugs were greater in patients in the first 72 hours after surgery. The effects of dobutamine on flow and oxygen transport were greater than those of dopamine, especially in the early postoperative period. The effects were smaller and not significant in patients more than three days after surgery, as well as in those with sepsis, respiratory failure, renal failure, age over 65 years, and hyperdynamic states, in part because of the small number of patients in each group. These data are consistent with the hypothesis that the beta 2-adrenergic action of dobutamine vasodilates the previously constricted peripheral circulation, enhances tissue perfusion by improving micro-circulatory flow distribution, and improves DO2 and VO2.

Adult↗
PubMed1988

Non-invasive conjunctival PCO2 and PO2 monitoring during hyper- and hypoventilation.

In order to evaluate potential applications of non-invasive fiberoptic conjunctival carbon dioxide (Pcj,CO2) and polarographic oxygen (Pcj,O2) sensors, we studied the effects of graded hyper- and hypoventilation on Pcj,CO2 and Pcj,O2 values in dogs. Pcj,CO2 values correlated well with Pa,CO2 (r = 0.95, n = 114); the mean Pcj,CO2--Pa,CO2 gradient was 4 +/- 3 (S.D.) Torr. Both hyper- and hypoventilation resulted in decreased Pcj,O2 values, whereas decreased Pa,O2 was observed only during hypoventilation; thus, the Pcj,O2/Pa,O2 index decreased during hyperventilation but was maintained during hypoventilation. Because both cerebral and conjunctival capillary beds vasoconstrict during hyperventilation, this methodology may assist in the non-invasive monitoring of cerebral oxygenation during cerebral resuscitation and surgery. Non-invasive Pcj,CO2 monitoring, which reflects Pa,CO2 during changes in ventilation, may be used to simplify ventilator management and weaning, as well as guide appropriate timing of arterial blood gas analysis in hemodynamically stable patients.

Animals↗
PubMed1988

Comparison of transcutaneous oximetry, vascular hemodynamic measurements, angiography, and clinical findings to predict the success of peripheral vascular reconstruction.

The present study examined prospectively the prognostic value of preoperative clinical findings, angiography, and conventional vascular hemodynamic and transcutaneous oximetry measurements in a consecutive series of patients undergoing lower extremity vascular reconstruction. A total of 25 variables were independently evaluated in each limb. Follow-up at least 6 months after operation was carried out in all patients. The postocclusive transcutaneous oxygen recovery time was found to be the most accurate predictor of short-term femoropopliteal bypass graft success. Preoperative foot transcutaneous oxygen recovery time values were significantly worse in patients whose femoropopliteal bypass grafts failed than in those in whom the outcome was successful (p less than 0.03). Transcutaneous oxygen recovery time values were also valuable in patients who underwent aortofemoral bypass; patients with isolated aortoiliac disease had significantly better foot transcutaneous oxygen recovery time values than those with combined aortoiliac and femoropopliteal disease (p less than 0.05). Foot transcutaneous oxygen recovery time values were also found to correlate well with the severity of symptoms (p less than 0.01), as did ankle-brachial Doppler pressure indices. Although the other variables analyzed provided useful diagnostic information, none were as accurate as the postocclusive transcutaneous oxygen recovery time in predicting the outcome of peripheral vascular reconstruction. As a means of more accurately classifying patients with peripheral vascular disease, we recommend the complimentary use of clinical findings, angiography, and hemodynamic and transcutaneous oximetry measurements. Because transcutaneous oxygen tension reflects the balance between local oxygen supply and demand, it may help to better define risk factors preoperatively in physiologic terms.

Aged↗
PubMed1988

Increased incidence of cardiac contusion in patients with traumatic thoracic aortic rupture.

A retrospective analysis of all patients with traumatic thoracic aortic rupture (TAR) admitted to the hospital over a consecutive 10-year period was performed in order to define the incidence, morbidity, and mortality of associated cardiac contusion (CC) in patients with TAR. Of the 13 patients with TAR, eight (62%) had associated CC. All patients with CC had two or more of the following positive findings: abnormal ECG, elevated myocardial-band creatinine kinase levels, abnormal radionuclide angiography/left ventricular segmental wall motion studies, or cardiac damage seen at surgery and postmortem examination. Four patients with TAR suffered cardiac arrest; all of the latter patients had associated CC. After successful repair of the TAR, five of six patients with combined TAR and CC developed adult respiratory distress syndrome (ARDS), whereas only one of five patients with isolated TAR had ARDS. All patients with isolated TAR survived, whereas three of eight patients suffering combined TAR and CC died perioperatively, secondary to cardiac arrest. In patients with TAR, the presence of associated CC occurs with increased frequency, is associated with increased morbidity (cardiac arrest, ARDS), and results in increased operative mortality secondary to cardiac instability. A branch-chain decision tree (clinical algorithm) was developed as a means of improving management of patients with combined TAR and CC, including indications for preoperative pulmonary artery catheterization.

Acute Disease↗
PubMed1988

Noninvasive measurement of tissue carbon dioxide tension using a fiberoptic conjunctival sensor: effects of respiratory and metabolic alkalosis and acidosis.

To evaluate potential clinical applications of a newly developed, noninvasive fiberoptic conjunctival carbon dioxide (PcjCO2) sensor designed to measure continuously tissue PCO2 in a vascular bed supplied by the internal carotid artery, we studied the effects of graded respiratory and metabolic alkalosis and acidosis on PcjCO2 in a hemodynamically stable canine model. Respiratory changes were induced by varying the frequency of ventilation and metabolic changes were induced by incremental infusions of sodium bicarbonate and hydrochloric acid. Continuous measurement of end-tidal carbon dioxide tension (PETCO2) was also performed. During respiratory alkalosis and acidosis, PcjCO2 values correlated well with PaCO2 (r = 0.96, n = 106); linear regression analysis of PcjCO2 vs. PaCO2 produced a slope of 1.01 and a y-intercept of 3.94 over a PaCO2 range of 12 to 76 torr. The mean PcjCO2-PaCO2 gradient was 4 +/- 3 (SD) torr. PETCO2 values also correlated well with PaCO2 (r = 0.91), as well as with PcjCO2 values (r = 0.91). Both PcjCO2 and PETCO2 showed a much weaker correlation with PaCO2 during metabolic alkalosis and acidosis, partly because the variation in PaCO2 was less. Moreover, the PcjCO2-PaCO2 gradient increased during the metabolic portion of the study up to a mean of 10 +/- 8 (SD) torr during metabolic acidosis, implying a build-up and/or lack of washout of CO2 from the conjunctival tissues, despite the normal physiologic range of PaCO2 values. We conclude that in a hemodynamically stable canine model, PcjCO2 and PETCO2 values correlate well with PaCO2 during pure respiratory alkalosis and acidosis; the correlation weakens significantly, however, with metabolic alterations in tissue CO2 levels.

Acidosis, Respiratory↗
PubMed1988

Multicomponent noninvasive physiologic monitoring of circulatory function.

A multicomponent noninvasive monitoring system for high-risk critically ill patients was developed and tested in a series of 58 high-risk surgical patients. The system was comprised of a thoracic electric bioimpedance (TEB) method for cardiac output estimation, laser-Doppler velocimeter for small vessel flow, transcutaneous oxygen (PtcO2) sensor for tissue oxygenation, pulse oximeter for arterial hemoglobin saturation (SaO2) and finger pressor sensor for arterial pressure. In a series of critically ill patients, this noninvasive system was compared with the widely used invasive monitoring system with systemic and pulmonary artery catheters. Despite theoretical limitations of TEB as a measure of cardiac output, there was a satisfactory correlation (r = .83) of cardiac output measured by thermodilution (TD) and TEB throughout a wide range of severe illnesses. Moreover, changes in TEB cardiac output satisfactorily tracked changes in TD cardiac output (r = .91). There was poor correlation between TD cardiac output and BP or heart rate. The incidence of abruptly changing physiologic patterns was observed with simultaneously monitored invasive and noninvasive systems. Descriptions were made of the central circulation, peripheral perfusion, and pulmonary function; common interactive responses of these circulations were also evaluated. Monitored events defined as abrupt reductions in these variables often occurred from reduced cardiac output, PtcO2 or PtcO2/PaO2 index, and infrequently from unanticipated reductions in SaO2. Recovery from the nadir of the monitored event was associated usually with improvements in flow, PtcO2, or both. Hemodynamic and oxygen transport patterns of a few commonly encountered patterns are described.

Adolescent↗
PubMed1988

Tissue oxygen debt as a determinant of lethal and nonlethal postoperative organ failure.

The aim of this study was to evaluate the concept that tissue oxygen debt reflected by inadequate oxygen consumption (VO2) in the intraoperative and immediate postoperative periods is a common determinant of multisystem organ failure and death. We measured the cumulative tissue oxygen debt during and immediately after 100 consecutive high-risk surgical operations in 98 patients and correlated these data with the subsequent development of lethal and nonlethal organ failure complications. The tissue VO2 deficit was calculated as the measured VO2 minus the estimated VO2 requirements corrected for both temperature and anesthesia; the net cumulative VO2 deficit was calculated as the integrated area under the VO2 deficit-time curve. The maximum cumulative VO2 deficit averaged 33.5 +/- 36.9 (SD) L/m2 in nonsurvivors, 26.8 +/- 32.1 L/m2 in survivors with organ failure, and 8.0 +/- 10.9 L/m2 in survivors without organ failure. The time postoperatively to reach the maximal cumulative VO2 deficit and the duration of the VO2 deficit was greatest in nonsurvivors, less in survivors with organ failure, and least in survivors without organ failure. Although many associated clinical conditions as well as innumerable physiologic mechanisms and biochemical mediators play important roles in tissue injury, tissue oxygen debt reflected by insufficient VO2 appears to be the primary event as well as a major determinant of organ failure and outcome.

Aged↗