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Biomedical subjects

C Weissman

Publications and source records attributed to C Weissman.

At least 109 records · Page 6Linked to original sources
PubMed1986

Ventilatory effects of the stress hormones in normal man.

The ventilatory responses to catecholamine infusions have been well studied. Increases in plasma levels of cortisol and glucagon during stress may exert a synergistic effect with epinephrine. We examined the effect of epinephrine and a combined hormone infusion in four normal postabsorptive subjects. On three separate occasions each subject was assigned randomly to receive a 5.5-h infusion of saline (control), epinephrine (1.2 micrograms/m2 . min), or epinephrine plus cortisol (5 mg/m2 . min) plus glucagon (3 mg/kg . min). Oxygen consumption (VO2), CO2 production, minute ventilation (VE), tidal volume (VT), frequency (f), inspiratory flow, and inspiratory time during room-air breathing and inhalation of 2% and 4% CO2 were measured before infusion and during the last 2 h of infusion, using a noninvasive canopy system. VO2 increased significantly (p less than .05) from the control condition during both combined and epinephrine infusions (23% and 11%, respectively). The increase in VE was related linearly to the increase in VO2, and was primarily due to an increase in VT; however, there was a small rise in f. The VE-PaCO2 regression during CO2 inhalation was shifted leftward to an equal degree during both infusions. These data indicate that cortisol and glucagon augment the calorigenic action of epinephrine; ventilatory effects are augmented in relation to the changes in VO2.

Adult↗
PubMed1986

Semistarvation and exercise.

Nutritional intake plays an important role in determining metabolic and respiratory demands during both rest and exercise. This study examines the effects in normal subjects of 4 days of semistarvation with 440 kcal/day of intravenously infused dextrose followed by the infusion of 480 kcal/day of amino acids for 48 h on the metabolic and ventilatory response to exercise (1.25, 2.50, and 5.0 kg . m/s.). After 4 days of the dextrose infusion, arterial PCO2 (P less than 0.05), and the ventilatory equivalent for CO2 (VE/VCO2, P less than 0.05) were decreased at rest compared with control measurements made prior to the dextrose infusion. During all three levels of steady-state exercise, arterial PCO2 was significantly lower (P less than 0.05) than observed before the start of the dextrose infusion. The subsequent infusion of amino acids resulted in increases in O2 consumption (V02; P less than 0.05) and minute ventilation (VE; P less than 0.05), a decrease in arterial PCO2 (P less than 0.05), and little change in CO2 production (VCO2) at rest. During low levels of exercise, compared with the values obtained following the 4 days of dextrose infusion, there were larger increases in VE and VO2, whereas VCO2 changed little. Mechanical efficiency (kcal work/kcal energy utilized) during exercise increased after 4 days of dextrose and returned to near control levels with the amino acid infusion. The adaptive response characteristic of semistarvation with dextrose appears to be altered when isocaloric amounts of amino acids are subsequently administered for short periods.

Adult↗
PubMed1986

The energy expenditure of the mechanically ventilated critically ill patient. An analysis.

This study characterizes the pattern of caloric expenditure of a group of 19 mechanically ventilated critically ill patients after surgery. Continuous measurements of metabolic rate were used to examine the total energy expended over an eight-hour period (10 AM to 6 PM) on 21 occassions. This allowed for determination of the energy expended during activity, rest, and sleep. The patients were observed to be resting, defined as lying motionless with eyes open and responsive to surrounding events, for 44 +/- 4 percent (SE) of the studied period. Sleeping, a state where the patient was not aroused by surrounding events, was observed for 17 +/- 3 percent of the studied period. Total energy expenditure was 4.8 +/- 1.8 percent greater than resting energy expenditure (REE). The REE was 13.1 +/- 2.3 percent above sleeping energy expenditure (awakeness factor), while activity energy expenditure was 17.1 +/- 2.9 percent above REE (activity factor). The respiratory quotient (RQ) during activity in the 15 patients receiving infusions of physiologic saline solution or 5 percent dextrose solution was significantly less (p less than 0.02) than the RQ during rest. This appears to be due to increased fat oxidation during activity.

Critical Care↗
PubMed1986

Forms of malnutrition in stressed and unstressed patients.

PCM can be usefully considered in terms of edematous (kwashiorkor-like) and nonedematous (marasmic) forms, as long as the limitations of the traditional terms are kept in mind. The body composition of subjects with undernutrition, or total starvation, both appear to maintain an extracellular fluid volume at a normal level, which increases as a percentage of the shrinking body weight. This is in contrast to patients with hospital malnutrition, in whom there is often an absolute increase in the extracellular volume while the body cell mass is shrinking. Data from the starvation literature suggest that the adult subject must gain approximately 10% of his or her body weight as extracellular expansion before edema is clinically evident. Preliminary evidence indicates that the hospitalized patient with the edematous form of malnutrition is at greater risk for complications and death when undergoing an operation, or requiring intensive care. The depleted patient who shows a rise in a depressed serum albumin after 7 to 10 days of TPN will have an improved prognosis when undergoing the stress of an elective operation. This improvement appears to be more the result of decreasing the expanded extracellular fluid volume than achieving a major increase in protein stores. The severely catabolic patient, particularly during episodes of major infection, can be expected to benefit by a nutritional intake that is carefully designed to provide calorie and nitrogen equilibrium. Nutritional intake high enough to guarantee positive balances of calories and nitrogen should be delayed until the acute catabolic stimulus has subsided, at which time the nutritional objective is to rebuild lost tissue.

Adaptation, Physiological↗
PubMed1985

Stimulation of oxidative drug metabolism by parenteral refeeding of nutritionally depleted patients.

To determine whether intravenous nutritional repletion can influence oxidative drug metabolizing capacity, antipyrine metabolism was studied in 6 malnourished patients on the second day of a 2-day baseline period and on the last day of two sequential, 8-day intravenous nutritional repletion periods. During the baseline period they received 5% dextrose, 440 kcal per day, intravenously. During the repletion periods they received 20 mg of nitrogen per kilocalorie of baseline resting energy expenditure and, in random order, dextrose to provide a total caloric intake of either 0.95 or 1.75 times baseline resting energy expenditure. There were no statistically significant differences between the high- and low-dextrose repletion regimens in their effects on antipyrine metabolism. Seven days of nutritional repletion resulted in a 42% decrease in mean half-life (range 12%-52%) and an 87% increase in mean metabolic clearance rate (range 29%-155%) for antipyrine. An additional 8 days of nutritional repletion resulted in no further change in these pharmacokinetic parameters.

Adult↗
PubMed1985

Evaluation of a non-invasive method for the measurement of metabolic rate in humans.

Measurements of oxygen consumption (VO2) and carbon dioxide production (VCO2) can be used to calculate energy expenditure. Such data are useful in the nutritional management of a variety of pathological conditions. This study is an evaluation in vitro and in vivo of the mating of a canopy and a Beckman metabolic measurement cart 1 (MMC). The canopy allows for the collection of expired gases without facial attachments. Studies in vitro demonstrated the necessity of calibrating the CO2 analyser at the concentrations used in such a system (0.50-0.80% CO2). Measurements of VO2 were within + 12% to -8% of predicted values, and when calibrated at 0.50% and 0.75% CO2, measurements of VCO2 were within + 2% and -7% of predicted values. The studies in vivo revealed that VO2 and VCO2 were within +/- 11% of the values obtained by using a canopy-spirometer-computer system. The MMC plus canopy may provide an alternative method for the clinical measurement of VO2 and VCO2, especially in subjects unable to tolerate a tight-fitting mask for prolonged periods.

Adult↗
PubMed1985

Ventilatory and metabolic effects of glucose infusions.

It has been demonstrated that total parenteral nutrition (TPN) results in increased O2 consumption (VO2), CO2 production (VCO2) and minute ventilation (VE). TPN consists of a mixture of glucose and amino acids. The individual role of each of these nutrients in mediating these changes has not been well established. To examine the effects of the individual nutrients, continuous infusions of glucose in hypo- and hypercaloric amounts were given to four normal volunteer subjects and four acutely ill patients for a six-day period, with three days on each dietary intake. After each three-day period, gas exchange, VO2, VCO2, and ventilatory variables (VE), tidal volume (VT), frequency (f), mean inspiratory flow (VT/TI), inspiratory time (TI) and expiratory time (TE) were measured. With the high carbohydrate diet, CO2 production increased 18 percent (p greater than .05) and 7 percent (p greater than .05) in the normal subjects and the patients, respectively. VO2 did not change, while the RQ rose. VE rose in parallel with VCO2, with no significant change in ventilatory sensitivity to CO2. In light of previous observations, these results suggest that during administration of TPN, the protein component plays a major role in the observed ventilatory changes: a) by bringing about a rise in VO2, which acts to magnify the effect of an increased RQ on VCO2, and b) by increasing ventilatory sensitivity to CO2.

Adult↗
PubMed1984

Abdominal aortic cross-clamping. Metabolic and hemodynamic consequences.

We address the question of whether an oxygen debt develops during a period of abdominal aortic cross-clamping that may explain observed hemodynamic changes. Group 1 received morphine sulfate (1 mg/kg) during induction of anesthesia. Group 2 received same dose of morphine sulfate. Group 3 received 4 mg/kg of morphine sulfate. We measured the oxygen consumption (VO2) and the carbon dioxide production levels (VCO2), as well as hemodynamic and biochemical parameters. In groups 1 and 3, VO2 and VCO2 decreased 10% to 13% following abdominal aortic cross-clamping compared with values measured before cross-clamping. In group 2, VO2 and VCO2 decreased 3% and 7%, respectively. On unclamping, the greatest increase in VO2 was observed in group 3 (26%), while in groups 1 and 2, VO2 rose 18% and 5%, respectively. In all three groups, metabolic changes were not paralleled by hemodynamic or temperature changes. Results indicate that oxygen debt developed during abdominal aortic cross-clamping, but this has no effect on hemodynamic changes seen after unclamping. Higher dosage of narcotic administered during anesthetic induction did not temper increase in metabolic rate observed after unclamping.

Aged↗
PubMed1984

Effect of protein intake on ventilatory drive.

Previous studies have demonstrated that if isotonic amino acid infusions were administered at a rate that approximated normal daily protein requirements, a leftward shift of the minute ventilation X PaCO2 relationship occurred. This study examined the effect of the administration of parenteral nutrition, at a fixed caloric intake and two levels of nitrogen (N) intake, on the ventilatory response to CO2 in nutritionally depleted patients. The intent was to determine whether increasing protein intake from normal to twice normal requirements would result in a further enhancement of the ventilatory response to CO2. Eight patients with nutritional depletion (greater than 10% weight loss) were studied. The resting energy expenditure (REE) was measured during administration of 5% dextrose, using principles of indirect calorimetry. Each patient received parenteral nutrition for a 2-week period. Two diets were examined for a 1-week period each: 1) a high N intake-15 mg nitrogen per kcal REE (approximately 21 g/day), or b) a low N intake--7.5 mg nitrogen per kcal REE (approximately 11 g/day). The initial diet was assigned randomly. Total energy intake was set at 1.35 X REE as measured during administration of 5% dextrose solution. Nonprotein calories were administered as 50% glucose and 50% fat. Breathing patterns at rest and during inhalations of 2 and 4% CO2 were analyzed using a canopy-computer-spirometer system. With an increased nitrogen intake there was a significant reduction in resting arterial PaCO2 from 39.9 to 37.6 mmHg (P less than 0.05) with no significant change in pH.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Effects of parenteral nutritional regimens on oxidative drug metabolism.

To determine whether the caloric source of intravenous nutrition can influence oxidative drug metabolizing capacity, antipyrine metabolism was studied in six healthy volunteers, who were taking no food or liquid by mouth, after they had been administered an intravenous nutritional regimen of 5% dextrose, 440 kcal/day, for 4 days and after they had been switched to an essentially isocaloric intravenous nutritional regimen of amino acids ( Aminosyn 3.5%) for 1 day. The change in intravenous nutritional regimen resulted in a 21% decrease in mean half-life (range: 3-32%), a 20% decrease in mean area under the concentration-time curve (range: 4-42%), and a 24% increase in mean metabolic clearance rate (range: 2-71%) for antipyrine. These results show that the change from intravenous dextrose to intravenous amino acids for only 1 day produced in all subjects an increase in antipyrine metabolism. Interestingly, there was marked variability in the responsiveness of the different subjects to the change in intravenous caloric source.

Amino Acids↗
PubMed1984

Ventilatory effects of biceps vibration during leg exercise in healthy humans.

The ventilatory effects of biceps tendon vibration were studied in healthy human subjects at rest and at two levels of light leg exercise. This was performed with intent to add the ventilatory effects of selective stimulation of muscle spindles to nervous and humoral respiratory inputs from contracting muscles. Tendon vibration performed in individuals at rest elicited a marked increase in respiratory frequency and in the ratio between inspiratory time and total breath duration with variable changes in tidal volume; this was in agreement with previous results (Jammes et al., 1981). When stimulation of biceps proprioceptors was performed during steady state exercise, the changes in ventilatory timing were attenuated, but variations in tidal volume often occurred. These results suggest that, when respiratory centers are being entrained by performance of work, further activation of muscle receptors exerts complex effects on the breathing pattern with a lack of facilitatory influences in ventilation and gas exchange.

Adult↗
PubMed1984

Effect of respiratory apparatus on respiration.

A mouthpiece plus noseclip (MP + NC) is frequently used in performing measurements of breathing patterns. Although the effects the apparatus exerts on breathing patterns have been studied, the mechanism of the changes it causes remains unclear. The current study examines the effects on respiratory patterns of a standard (17-mm-diam) MP + NC during room air (RA) breathing and the administration of 2 and 4% CO2 in normal volunteers and in patients 2-4 days after abdominal operation. When compared with values obtained with a noninvasive canopy system, the MP + NC induced increases in minute ventilation (VE), tidal volume (VT), and mean inspiratory flow (VT/TI), but not frequency (f) or inspiratory duty cycle, during both RA and CO2 administration. The percentage increase in VE, VT, and VT/TI caused by the MP + NC decreased as the concentration of CO2 increased. During RA breathing, the application of noseclip alone resulted in a decrease in f and an increase in VT, but VE and VT/TI were unchanged. The changes were attenuated during the administration of 2 and 4% CO2. Reducing the diameter of the mouthpiece to 9 mm abolished the alterations in breathing pattern observed with the larger (17-mm) diameter MP.

Adult↗
PubMed1984

Effect of routine intensive care interactions on metabolic rate.

The alterations in metabolic (oxygen consumption [VO2] and carbon dioxide production [VCO2]) and hemodynamic (heart rate and blood pressure) parameters caused by various common intensive care activities were examined in a group of 23 mechanically-ventilated critically-ill patients. The observed variations in metabolic rate can be classified into four categories as follows: (a) the lowest energy expenditure, which was associated with sleeping in the majority (83 percent) of instances; (b) resting, which was defined as a state where the patient was lying motionless with eyes open and responding to surrounding events, where VO2 and VCO2 averaged 9.1 +/- 7.5(SD) percent and 7.5 +/- 7.3 percent, respectively, above the lowest values; (c) a variety of routine daily care activities (eg, bathing, performing a physical examination) that although not particularly painful, caused arousal from the resting state. During these situations, VO2 and VCO2 averaged about 20 percent above lowest values; and (d) chest physical therapy, which was associated with metabolic increases of 35 percent above lowest values as well as increases in both heart rate and blood pressure. This study demonstrates that routine daily ICU activities can significantly alter metabolic rate, and thus, it is important to couple such measurements with astute observations of the patients' activity state. In addition, we have defined an activity state--resting--that can be used in the calculation of energy expenditure as well as for intrapatient and interpatient comparisons.

Carbon Dioxide↗
PubMed1984

Arachidonic acid metabolism by retinas of rats with streptozotocin-induced diabetes.

Arachidonic acid metabolism via the cyclooxygenase pathway and the effects of aspirin and indomethacin were studied in whole retinas of rats with streptozotocin-induced diabetes. Diabetes was induced by intravenous injection of streptozotocin (60 mg/kg) and the animals were examined 5-6 weeks later. Whole retinas of nondiabetic and diabetic animals were incubated for 1 1/2 hours, and the amounts of prostacyclin and prostaglandin E2 (PGE2) accumulated in the media were measured. The amounts of PGE2 in the media of diabetic retinas was significantly lower than levels in media of nondiabetic group. However, the amounts of prostacyclin accumulated in the media of nondiabetic and diabetic retinas did not differ significantly. Addition of arachidonic acid (A.A.) to the incubation media caused an enhancement in the amounts of PGE2 and prostacyclin in the incubation media of both diabetic and nondiabetic retinas. Addition of indomethacin or aspirin to the incubation media caused a reduction of prostacyclin and PGE2 levels in the media of both groups.

Animals↗
PubMed1983

Hypercalcemia and hypercalciuria in a critically ill patient.

A case of unexplained intermittent hypercalcemia and hypercalciuria in a patient with a prolonged critical illness is presented. The differential diagnosis and workup of this disorder under such circumstances are discussed. The influences of immobilization and total parenteral nutrition (TPN) are explored.

Abscess↗
PubMed1983

Artifacts in measurement of resting energy expenditure.

Measurements of gas exchange have been demonstrated to be clinically useful in the care of critically ill and malnourished patients. Using principles of indirect calorimetry, resting energy expenditure (REE) can be calculated from gas exchange data and used as the basis for designing a nutritional support regimen as well as for following the patient's metabolic state. This study demonstrates that a relatively minor procedure, such as percutaneous muscle biopsy, can induce temporary but major increases in gas exchange and lead to an overestimation of REE. Four studies were performed on 3 healthy adult subjects admitted to the Surgical Metabolism Unit for nutritional study. A percutaneous muscle biopsy was performed with the subject inside a canopy with continuous recording of oxygen consumption (VO2) and carbon dioxide production (VCO2). After the muscle biopsy, VCO2 and VO2 increased 93 and 103% (at their peak value), respectively. The mean duration that these changes persisted at least 15% above control was 10.6 +/- 7.8 (SD) and 11.4 +/- 5.9 min of VCO2 and VO2, respectively. Thus, considerable artifacts in the estimation of REE can occur due to painful stimuli.

Adult↗