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Biomedical subjects

F G Mihm

Publications and source records attributed to F G Mihm.

At least 19 recordsLinked to original sources
PubMed2004

Measurement of cardiac output by transpulmonary arterial thermodilution using a long radial artery catheter. A comparison with intermittent pulmonary artery thermodilution.

Cardiac output can be measured accurately by transpulmonary arterial thermodilution using the PiCCO (Pulsion Medical Systems, Munich, Germany) system with a femoral artery catheter. We have investigated the accuracy of a new 50 cm 4 French gauge radial artery catheter and the ability to use the system with a shorter radial catheter. We studied 18 patients who had undergone coronary artery surgery and made three simultaneous measurements of cardiac output by arterial thermodilution and with a pulmonary artery catheter. The radial catheter was withdrawn in 5 cm increments and the measurements were repeated. We found close agreement between arterial thermodilution and pulmonary artery thermodilution with a mean (SD) bias of 0.38 (0.77) l x min(-1). Arterial thermodilution became unreliable once the catheter had been withdrawn by more than 5 cm. We conclude that cardiac output measurement with arterial thermodilution with a radial catheter is interchangeable with that derived from a pulmonary artery catheter, and that a centrally sited arterial catheter is required for accurate determination of cardiac output by transpulmonary arterial thermodilution.

Aged↗
PubMed1998

A multicenter evaluation of a new continuous cardiac output pulmonary artery catheter system.

OBJECTIVE: To validate a new system of continuous cardiac output monitoring. DESIGN: Multicenter, prospective, nonrandomized clinical study. SETTING: Four university hospitals. PATIENTS: Forty-seven adult intensive care unit patients. INTERVENTIONS: Pulmonary artery catheterization. MEASUREMENTS AND MAIN RESULTS: Continuous and bolus cardiac output measurements were obtained over 72 hrs. The 327 continuous cardiac output measurements compared favorably with bolus cardiac output measurements (bias = 0.12 L/min, precision = +/-0.84). The continuous cardiac measurement was not adversely affected by temperatures of <37 degrees C or >38 degrees C, high (>7.5 L/min) or low (<4.5 L/min) cardiac output values, or duration (72 hrs) of the study. CONCLUSIONS: This continuous cardiac output system provides a reliable estimate of cardiac output for clinical use if applied in conditions similar to this study. The combination of a continuous measure of cardiac output with other continuous physiologic monitoring (arterial and mixed venous oxygen saturation, oxygen consumption, etc.) may provide important information that no single parameter could achieve.

Adolescent↗
PubMed1989

Recovery of cardiopulmonary reflexes in monkeys undergoing heart-lung transplantation.

After heart-lung transplantation in primates, cardiopulmonary reflexes were tested and shown to be present. The Hering-Breuer and cough reflexes were tested, as well as responses to an inhaled respiratory stimulant, vasodilator, and an intravenous anticholinesterase and antimuscarinic agent. Recovery of these responses, except to the anticholinesterase agent, suggests that reinervation occurs in autotransplanted organs in primates. The Hering-Breuer reflex was present at 1.9 and 2.2 months after the operation in two animals subjected to autotransplantation. These cardiopulmonary reflex responses were also demonstrated in two allograft recipients studied at 15 and 16.9 months after the operation. Return of protective reflexes such as coughing may be an important mechanism to prevent aspiration pneumonitis and other complications in humans.

Ammonia↗
PubMed1988

Effect of heparinization of catheters on pulmonary artery oximetry.

A clinical study was performed in two phases to determine whether pulmonary artery oximeter catheters that were impregnated or bonded with heparin would affect the accuracy of measurements of in vivo mixed venous oxygen saturation (Sv-O2). In phase 1, 40 patients were catheterized with either a heparin-impregnated or a plain pulmonary artery catheter. Blood was sampled at random times to correlate in vivo with in vitro Sv-O2 measurements. In phase 2, 16 patients who were not receiving systemic heparin therapy or aspirin and who had no coagulopathies were catheterized with either a heparin-bonded or a plain pulmonary artery catheter in a blinded order. In phase 1, a total of 364 blood samples were obtained from 40 patients. Linear regression analysis of the pooled data demonstrated y = 0.98x - 0.01, r = 0.93, P less than 0.001, and n = 141 with heparin-impregnated catheters; and y = 0.87x + 8.0, r = 0.81, P less than 0.001, and n = 223 with plain catheters. The mean difference (in vivo minus in vitro) revealed a similar error (-1.3 +/- 0.4 versus -1.4 +/- 0.4, respectively, mean +/- SE). The 95% confidence limits of an individual value (+/- 8.1 versus +/- 12.3) suggested slightly greater accuracy with heparin-impregnated catheters. In phase 2, a total of 134 blood samples were obtained from 16 patients. Linear regression analysis showed nearly equal performance with heparin-bonded and plain catheters (r = 0.97 versus r = 0.98, respectively) with similar slopes (1.0 versus 1.1, respectively) but different intercepts (-0.6 versus -8.4, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Catheters, Indwelling↗
PubMed1988

Extra-adrenal pheochromocytoma: an unusual location.

A 14-year-old boy with a retrohepatic para-aortic pheochromocytoma demonstrates the potential difficulties of localization in an unusual extra-adrenal site of pheochromocytoma. Ultrasonography, computed tomography, metaiodobenzylguanidine scanning, and angiography with venous sampling failed to define the true anatomic location of this tumor. Collateral venous drainage produced confusing venous sampling data and represents a potential pitfall in the interpretation of these studies.

Abdominal Neoplasms↗
PubMed1988

Pulmonary effects of crystalloid and colloid resuscitation from hemorrhagic shock in the presence of oleic acid-induced pulmonary capillary injury in the dog.

The effects of resuscitation with crystalloid and colloid solutions in the presence of increased pulmonary capillary permeability were studied. Twenty-four hours after oleic acid administration, dogs were anesthetized and bled to produce hemorrhagic shock. One hour later, resuscitation was performed with saline, 5% albumin, or 6% hydroxyethyl starch solution to restore and then maintain cardiac output at pre-oleic acid values for 6 h. Dogs were recovered and, 24 h later, were reanesthetized for final measurements. Oleic acid administration resulted in increases in pulmonary artery pressure, pulmonary vascular resistance, and extravascular lung water (EVLW). Resuscitation from hemorrhagic shock restored pulmonary hemodynamics to pre-hemorrhage levels and did not affect EVLW, PaO2, shunt fraction, dead-space-to-tidal-volume ratio, or pulmonary compliance. There were no differences in these parameters related to the choice of resuscitation fluid. Saline resuscitation markedly reduced plasma oncotic pressure and the plasma oncotic-pulmonary artery occlusion pressure gradient. Values for these two variables were markedly lower with saline than with colloid resuscitation. The authors conclude that the pulmonary effects of crystalloid and colloid solutions are similar in the presence of moderate increases in pulmonary capillary permeability.

Animals↗
PubMed1987

Care of the adult patient during transport.

Interhospital transport of the critically ill patient involves maintaining the same quality of care that was present before transport. This requires planning for equipment, space, and personnel needs during transport, and instituting adequate pathophysiologically based treatment and stabilization prior to transport. Under such conditions, transport can be safely accomplished and have a positive impact on patient care.

Adult↗
PubMed1987

Thermal dye double indicator dilution measurement of lung water in man: comparison with gravimetric measurements.

The thermal dye double indicator dilution technique for estimating lung water was compared with gravimetric analyses in nine human subjects who were organ donors. As observed in animal studies, the thermal dye measurement of extravascular thermal volume (EVTV) consistently overestimated gravimetric extravascular lung water (EVLW), the mean (SEM) difference being 3.43 (0.59) ml/kg. In eight of the nine subjects the EVTV -3.43 ml/kg would yield an estimate of EVLW that would be from 3.23 ml/kg under to 3.37 ml/kg over the actual value EVLW at the 95% confidence limits. Reproducibility, assessed with the standard error of the mean percentage, suggested that a 15% change in EVTV can be reliably detected with repeated measurements. One subject was excluded from analysis because the EVTV measurement grossly underestimated its actual EVLW. This error was associated with regional injury observed on gross examination of the lung. Experimental and clinical evidence suggest that the thermal dye measurement provides a reliable estimate of lung water in diffuse pulmonary oedema states.

Adolescent↗
PubMed1987

Nasal continuous positive airway pressure in atelectasis.

Nasal continuous positive airway pressure (CPAP) has been widely and safely used in the treatment of sleep disorders but has not been previously utilized for therapy of pulmonary atelectasis in adults. We observed three patients with significant atelectasis which was refractory to conventional chest physiotherapy. Bronchoscopy was not a viable therapeutic option in any patient. Therapy with continuous nasal CPAP was initiated at 10 to 15 cm H2O. The patients tolerated the therapy well and had prompt resolution of atelectasis. Nasal CPAP may be an effective modality for therapy of pulmonary atelectasis in spontaneously breathing patients, particularly when conventional therapies are not tolerated or are ineffectual.

Adult↗
PubMed1987

Leukotriene D4 increases extravascular lung water in the dog.

The peptide leukotrienes have been detected in animals that have received endotoxin injections and also have been associated with patients suffering from the adult respiratory distress syndrome (ARDS). The ability of leukotriene D4 (LTD4) to cause pulmonary capillary permeability changes was investigated in ten anesthetized mongrel dogs. Four dogs were used as controls and six dogs received intravenous LTD4 (0.25 microgram/kg). There was a variable response in that two treated animals showed no apparent effect of LTD4. Analysis of the results from the remaining four treated animals demonstrated a significant increase in extravascular lung water (EVLW) that peaked 3 hr after LTD4 from 5.4 +/- 0.6 to 10.3 +/- 0.5 ml/kg (P less than .01). In these four dogs, EVLW increased before slight, but statistically significant, rises in pulmonary artery wedge pressure (4 +/- 1 to 9 +/- 1 mm Hg, P less than .01) and mean pulmonary artery pressure (13 +/- 1 to 17 +/- 1 mm Hg, P less than .01) occurred. During the same period, cardiac output decreased 56 +/- 7% (P less than .01), but no change in airway resistance was observed. This study is the first in vivo demonstration that LTD4 directly alters pulmonary fluid balance in the dog. We conclude LTD4 can cause increases in EVLW and may be an important mediator of the permeability changes observed in various clinical events that lead to the adult respiratory distress syndrome.

Animals↗
PubMed1986

New methods for whole blood oximetry.

New techniques for determining the hematocrit (Hct) and oxygen saturation (SO2) of whole blood from backscattered light measurements are described. First, theoretical and experimental results are presented which show that the empirical linear relationship between SO2 and the infrared-red backscattered light intensity ratio on which previous instruments have been based is an inadequate description primarily because it does not account for the strong effects of Hct and transducer geometry. Then it is shown that the ratio of backscattered intensities from two appropriately positioned infrared sources can be plotted against the infrared-red intensity ratio to produce a family of calibration curves from which SO2 and Hct can be independently determined. Finally, a practical implementation of an oximetry system which employs a microelectronic catheter-tip optical sensor and a microprocessor-based signal processor is proposed.

Biomedical Engineering↗
PubMed1986

The thermal-dye method of lung water measurement is reliable at a low cardiac output.

The measurement of lung water by the thermal-dye double indicator dilution technique was evaluated in dogs with normal and edematous lungs during a state of reduced cardiac output. The technique used cold indocyanine green dye to measure extravascular thermal volume (EVTV) as an estimate of extravascular lung water (EVLW). Anesthesia was maintained with pentobarbital. In 15 of 21 animals, pulmonary edema was first induced with oleic acid (0.75 to 0.18 ml/kg). Cardiac output (CO) was then decreased by a combination of propranolol and slow exsanguination (mean CO reduction to 36% of baseline). Extravascular lung water produced in this model ranged from 1.4 to 30.2 ml/kg. Predetermination measurements of EVTV correlated closely with EVLW as determined by gravimetric analysis (EVTV = 1.1 EVLW + 4.7 ml/kg, n = 21, r = 0.93, P less than 0.001). Thermodilution cardiac output measured in the abdominal aorta (used in the calculation of the EVTV) correlated well with simultaneous measurements of cardiac output by both indocyanine green dye dilution and pulmonary artery thermodilution (r = 0.86 and r = 0.88, respectively, pretermination). The thermal-dye technique appears to provide an accurate reflection of lung water in normal and edematous lungs, even in the presence of a low cardiac output.

Animals↗
PubMed1986

Hypothermic preservation of the heart and lungs with Collins solution: effect on cardiorespiratory function following heart-lung allotransplantation in dogs.

The effect of preserving the heart and lungs with hypothermia and Collins solution was studied in 13 mongrel dogs undergoing combined heart-lung transplantation. The five control animals who underwent an immediate transplant following Collins solution perfusion had small increases in extravascular lung water when measured 2.5 hours posttransplant as seen in a previous study. The eight animals who had hypothermic preservation following Collins solution perfusion had significantly higher extravascular lung water than controls (16.3 +/- 1.8 ml/kg in preserved animals; 11.2 +/- 1.7 ml/kg in controls p less than 0.05). The level of lung water reached at 2.5 hours postoperatively was similar to that reached with a previously reported, unacceptable preservation technique. Survival beyond this point was poor due to severe pulmonary edema. We conclude that the use of this solution, given under the experimental conditions which we describe, is not acceptable for hypothermic preservation of the heart and lungs for combined transplantation.

Animals↗
PubMed1986

Anaesthesia for heart transplantation. A retrospective study and review.

The anaesthetic records of 261 heart transplant recipients were reviewed. Data collected included demographic characteristics, physical status, results of preoperative cardiac catheterization studies, anaesthetics agents and incidences of complications which may have been related to anaesthetic management. Forty-five patients received a volatile agent (methoxyflurane 31, enflurane 10, halothane 4) and 216 patients were anaesthetized with a high-dose narcotic technique (morphine 122, fentanyl 71, hydromorphone 14, meperidine 9). Hypotension and arrhythmias were correlated with use of volatile and narcotic anaesthetics, respectively. No mortality was associated with anaesthetic management.

Adolescent↗