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Biomedical subjects

A I Hyman

Publications and source records attributed to A I Hyman.

At least 19 recordsLinked to original sources
PubMed1992

Caloric requirements and supply in critically ill surgical patients.

OBJECTIVE: To compare the caloric intake with the caloric requirements in postoperative patients being fed enterally via nasoenteric tubes, parenterally, or by both enteral and parenteral methods. DESIGN: Descriptive study. SETTING: Surgical ICU in a university teaching hospital. PATIENTS: Sample of 22 mechanically ventilated postoperative patients, mean age 62 +/- 17 yrs, selected from among those patients routinely scheduled to receive enteral or parenteral nutrition or both, for greater than or equal to 4 days. The patients were studied for a total of 144 study days. INTERVENTION: Eight patients received total parenteral nutrition, eight patients received enteral nutrition, and six patients received both parenteral and enteral nutrition. MEASUREMENTS: Resting energy expenditure was measured by using indirect calorimetry, and daily nutritional intake was quantitated. RESULTS: The patients who received parenteral, or enteral plus parenteral nutrition received an average of 80% of their caloric requirements, while those patients who received only enteral nutrition received only 68% of their caloric requirements. There was more day-to-day variation in nutrient intake in the enteral group (40% +/- 56%) than in the parenteral group (12.2% +/- 24%, p less than .001). CONCLUSIONS: Enteral nutrition delivered via nasoenteric tubes as the sole delivery method in postoperative critically ill patients resulted in an inadequate and inconsistent nutrient supply. The use of parenteral or parenteral plus enteral nutrition resulted in more stable and adequate feeding than feeding by enteral nutrition alone.

Adult↗
PubMed1989

Variation in the resting metabolic rate of mechanically ventilated critically ill patients.

There has been increasing interest in the nutritional support of the critically ill patient. The day-to-day variation in resting energy expenditure (REE) was studied over a 3-5-day period in 17 postoperative mechanically ventilated critically ill patients to gain insight as to how often caloric intake should be reassessed, whether changes observed over 3-5 days are of sufficient magnitude to make frequent adjustments in caloric intake, and what factors are associated with large alterations in metabolic rate. REE was measured daily for 3-5 days, and the percent variation in REE [(highest REE--lowest daily REE)/(lowest daily REE) x 100] calculated. The variation ranged from 4 to 56%, and on further analysis two distinct groups were identified, one with a mean variation of 12 +/- 4% (SD) (range 4-18%) and the other with a mean variation of 46 +/- 8% (range 37-56%). The former group was clinically stable, whereas the latter was not. Clinically stable patients need less frequent measurements than those who are more ill, but when designing a nutritional regimen for them, at least 20-25% should be added to the REE, 15% to account for day-to-day variation and 5-10% for activity.

Adolescent↗
PubMed1988

Attenuation of the hemodynamic responses to chest physical therapy.

Chest physiotherapy (CPT) is a commonly used technique in mechanically ventilated critically ill patients. This study examines the hemodynamic and metabolic changes associated with CPT and measures the attenuation by two doses of intravenous fentanyl (1.5 micrograms/kg and 3.0 micrograms/kg) on these changes. Heart rate, systolic and mean blood pressures, cardiac output, oxygen consumption (VO2), and carbon dioxide production (VCO2) all increased during CPT. Decreases in arterial pH and VE and increases in PaCO2 were also observed. The higher, but not lower dose, of fentanyl significantly attenuated increases in blood pressure and heart rate during CPT and no substantial hemodynamic changes occurred once CPT had stopped. The increases in VO2 and VCO2 were not attenuated. Short acting narcotics attenuate the hemodynamic responses to stressful stimuli such as CPT.

Analgesia↗
PubMed1987

Do oxygen consumption and carbon dioxide production affect cardiac output after cardiopulmonary bypass?

This study examines the oxygen consumption (VO2) and carbon dioxide production (VCO2) occurring before, during, and after cardiopulmonary bypass (CPB) and whether they correlate with changes in cardiac output. Twenty-three patients undergoing open heart surgery were studied. Group 1 (N = 11) received fentanyl citrate, 50 micrograms/kg, intravenously during the induction of anesthesia. Group 2 (N = 12) received 100 micrograms/kg of fentanyl citrate intravenously. We measured VO2, VCO2, as well as hemodynamic and biochemical factors. Initial statistical analyses failed to show any differences in the VO2, VCO2, hemodynamic, or biochemical factors between groups 1 and 2. Therefore, the data from both groups were combined. In comparing the average (for all data) of the post-CPB with the pre-CPB periods in both groups for the metabolic factors, there were 9.0%, 11.5%, and 2.4% increases in the VO2, VCO2, and respiratory quotient, respectively. There was an 80% increase in total serum lactate levels seen in the post-CPB periods when compared with the pre-CPB periods. Serum triglyceride and free fatty acid levels measured in the post-CPB period decreased 39% and 25%, respectively, when compared with the pre-CPB periods. Although there were no changes in the cardiac outputs following CPB, the post-CPB periods showed a 37% increase in central venous pressure when compared with the pre-CPB periods. These data suggest that although there are significant metabolic and biochemical sequelae to CPB, the modest increases in post-CPB VO2, and VCO2 did not affect cardiac output following cardiovascular surgery. Increasing doses of narcotic do not have an effect on those relationships.

Blood Gas Analysis↗
PubMed1987

Metabolic and respiratory changes during weaning from mechanical ventilation.

Weaning from mechanical ventilation is a procedure performed daily in intensive care units. This study sought to determine whether among postoperative patients there were any differences in the changes in oxygen consumption (VO2) and carbon dioxide production (VCO2) between those patients in whom mechanical ventilation was successfully discontinued and those in whom it was continued or reinstituted. A stepwise reduction in mandatory breaths (from 10 to 12 to 4 to 6), followed by a period of continuous positive airway pressure (CPAP), was the weaning method. In the group of patients (N = 18) who were successfully weaned, VO2 and VCO2 increased 10 +/- 8 (SD) percent and 10 +/- 9 percent, respectively, while VE decreased 9 +/- 8 percent and PaCO2 was unchanged when values at an IMV of 10 to 12 were compared with those on CPAP. In the group (N = 17) who were not successfully weaned, VO2 and VCO2 increased 8 +/- 10 percent and 6 +/- 9 percent, respectively, while PaCO2 rose (37.9 +/- 4 to 42.5 +/- 2.9) significantly (p less than 0.02). There was a significantly greater decrease (15 +/- 3 percent) in VE than in the other group. Changes in VO2 or VCO2 did not aid in predicting which patients would be successfully weaned.

Adult↗
PubMed1987

Nutritional care of the critically ill patient with respiratory failure.

Nutritional support is an integral part of the therapy for lung dysfunction because malnutrition can predispose an already critically ill patient to pneumonia and respiratory failure. Physicians must, however, be sensitive to the changes in cardiac and respiratory function that certain nutrients can cause.

Critical Care↗
PubMed1986

The effects of posture on the metabolic and ventilatory response to low level steady state exercise.

Low level exercise is frequently used to assess cardiac and pulmonary function. This study examines the differences in both metabolic and respiratory patterns between the sitting and supine position. Six normal male subjects were studied in both positions during four levels of exercise (12.5, 25, 37.5 and 50 W). Oxygen consumption (VO2), carbon dioxide production (VCO2) and minute ventilation (VE) were greater when sitting as were the ventilatory equivalents to O2 (VE/VO2) and CO2 (VE/VCO2). Respiration was compared at equivalent workloads; the greater minute ventilation observed during sitting was due to greater tidal volumes (VT) and mean inspiratory flows (VT/TI). Expiratory time (TE) was longer and inspiratory duration shorter under most conditions when sitting. When breathing patterns were compared at similar degrees of minute ventilation, VT, TE and VT/TI were greater when sitting, while respiratory frequency (fR) was slower.

Carbon Dioxide↗
PubMed1986

Response to tubular airway resistance in normal subjects and postoperative patients.

Critically ill patients must often breathe spontaneously through an endotracheal tube that acts as a fixed inspiratory and expiratory tubular airway resistor. Although this practice is common, its effect on the pattern of breathing is not known. The mean breathing patterns of seven normal, healthy male subjects and eight male patients who had undergone upper abdominal surgery 2-4 days previously were studied breathing through a mouthpiece fitted in random order with a 5, 6, 7, 8, or 15 mm diameter (17 mm long) resistor. These diameters were selected because they simulate the pressure-flow relationships of adult endotracheal tubes. With the 15 mm aperture, the patients had a greater breathing frequency (f) than did the normal subjects (21 +/- 5 [SD] vs. 14 +/- 4 breaths/min, P less than 0.01) as well as a smaller mean tidal volume (VT). In both groups, minute ventilation (VE) and f progressively decreased as resistance was increased by decreasing the aperture size from 15 to 16 mm. In the normal subjects but not the patients, VT also progressively decreased. When the diameter was decreased from 6 mm to 5 mm, there were increases in VT and decreases in f that were more marked in the normal subjects. In both groups, the changes in VE were accompanied by decreases in mean and peak inspiratory and expiratory flow rates. Throughout the study, oxygen consumption (VO2) and carbon dioxide production (VCO2) did not change. This, coupled with the decreases in VE resulted in decreases in the ventilatory equivalents to CO2 and O2 (VE/VCO2, VE/VO2).(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1986

Resting metabolic rate of the critically ill patient: measured versus predicted.

Critically ill patients requiring mechanical ventilation are particularly susceptible to malnutrition. A knowledge of the energy requirements of these patients is essential in designing nutritional regimens. This study examines 45 resting energy-expenditure measurements performed in a group (n = 40) of postoperative, critically ill patients who were hemodynamically stable, noncomatose, and receiving mechanical ventilation. It examines in particular to what degree the resting energy expenditure of such patients can be predicted using the Harris-Benedict and Aub-Dubois formulae. Resting energy expenditure was measured using indirect calorimetry. There was only a moderate correlation between measured resting energy expenditure and that predicted using the Harris-Benedict (r = 0.57) and Aub-Dubois (r = 0.59) formulae. There was little correlation between the ratio of the measured to the predicted (Harris-Benedict) resting energy expenditure and age, or the ratio of actual to ideal body weight and body weight. The measured resting energy expenditure differed widely (70-140%) from predicted, reflecting the many complex factors that influence these patients' metabolic rate. The role of standard predictive formulae in such patients is as an arbitrary reference point to be used to define hypermetabolism (measured greater than predicted) and hypometabolism (predicted greater than measured).

Adolescent↗
PubMed1986

The metabolic and ventilatory response to the infusion of stress hormones.

Sepsis and trauma result in increases in epinephrine, glucagon, and cortisol secretion as well as alterations in respiratory pattern that is characterized by increased minute ventilation, decreased tidal volume, and increased frequency. Six male subjects were infused for 5.5 hours with cortisol, epinephrine, and glucagon in amounts designed to simulate plasma levels seen in patients following trauma. During the initial 20 minutes of the hormone infusion, minute ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2) increased above preinfusion values. VCO2 increased more than VO2 resulting in an increase in respiratory quotient (RQ) from 0.93 to 1.14. The increase in VE was due to increased tidal volume and not frequency (f). After 4.5 hours, the VE, VO2, and VCO2 were still above preinfusion levels but the RQ had decreased to 0.98 because of a decrease in VCO2. Frequency had increased from 19 +/- 4.8 breaths/min preinfusion to 22 +/- 4.7 after 4.5 hours. After 4.5 hours, VT was still above preinfusion levels while pH and PaCO2 had decreased below them. The latter was associated with an increase in serum lactate. At no time was a decrease in tidal volume observed. Therefore, the infusion of these hormones does not simulate all the alterations observed during trauma and sepsis.

Adult↗
PubMed1986

Cardiovascular changes during transport of critically ill and postoperative patients.

We examined cardiovascular changes in 37 patients transported to an ICU after major general or vascular surgery (n = 14), open heart surgery (n = 13), or carotid endarterectomy (n = 10). Cardiovascular variables were also measured in a control group of 11 patients transported from an ICU for diagnostic or therapeutic procedures. All patients were followed for 30 min before transport until approximately 30 min after they arrived at their destinations. During this period, systolic BP and heart rate significantly increased only in patients recovering from major general/vascular surgery or carotid endarterectomy. These changes were apparently related to acute emergence from inhalational anesthesia (isoflurane plus nitrous oxide), since the other surgical patients were anesthetized with narcotic anesthesia, and the control group did not receive any anesthesia.

Blood Pressure↗
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

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↗
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 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↗
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

Morphine and postoperative rewarming in critically ill patients.

Morphine sulfate (MSO4) has been demonstrated to attenuate the stress response. MSO4 might be useful in minimizing the stress associated with the perioperative period, particularly that due to awakening from anesthesia and rewarming. Two groups of critically ill patients who developed hypothermia (35.8 degrees C) during a surgical procedure were studied. The control group was observed during routine medical management. Group II received 1 or 4 mg/kg MSO4 followed by an infusion of 0.2 or 0.5 mg/kg/hr. During the postoperative rewarming period the control group patients demonstrated a major increase in metabolic demand and myocardial work. In group II patients the infusion of MSO4 resulted in a lower metabolic rate. This was associated with a significantly longer rewarming time and a significant reduction in shivering, heat loss, heart rate, mean arterial pressure, and rate-pressure product. Infusion of MSO4 in critically ill patients during the perioperative period suppressed metabolic demands and myocardial work while preserving cardiovascular function.

Aged↗