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Biomedical subjects

S H Rosenbaum

Publications and source records attributed to S H Rosenbaum.

18 recordsLinked to original sources
PubMed1992

Failure of negative dipyridamole thallium scans to predict perioperative myocardial ischaemia and infarction.

Three cases of postoperative myocardial infarction are reported in patients with normal or fixed defects on preoperative dipyridamole thallium scans (interpreted as "negative" for active cardiac ischaemic risk). All patients were monitored with an ambulatory electrocardiographic recorder from the evening before surgery through the first two postoperative days. Two of the patients demonstrated preoperative or early postoperative ischaemia, suggesting that the test was a false negative. The third patient did not demonstrate ischaemia during the period of monitoring, but developed a myocardial infarction during the third postoperative day, suggesting progression of the underlying coronary artery disease. Preoperative dipyridamole thallium imaging may result in false negative scans in selected high-risk populations.

Aged↗
PubMed1992

ST segment depression during labor and delivery.

ECG changes suggestive of myocardial ischemia are common during cesarean delivery under regional anesthesia. To determine the time course, duration, and significance of these ECG changes, we monitored 111 parturients with continuous ambulatory ECG (Holter) during and after cesarean delivery. Twenty-two parturients undergoing vaginal delivery were similarly monitored. ST segment depression was present in 25% of patients undergoing cesarean delivery but was not found in those patients delivering vaginally. ST segment elevation was not detected in either group. The incidence of ST segment depression during cesarean delivery was similar with epidural (29%), spinal (17%), and general (18%) anesthesia, occurring most commonly in the 30 min following delivery (P less than 0.001). Transthoracic echocardiographic imaging was performed in 23 patients undergoing cesarean section. Five of the 23 patients had seven episodes of intraoperative ST segment depression. Regional wall motion abnormalities were not present in any patient. A decrease in ejection fraction area greater than 15% from baseline or from previous interval ejection fraction area was present during four episodes of ST change. Three episodes of ST depression were not associated with significant decreases in ejection fraction area. Precordial Doppler monitoring for detection of venous air embolism in 25 patients revealed no association between the occurrence of venous air embolism and ST segment depression. We conclude that although significant myocardial impairment during cesarean delivery does not occur, episodes of ST depression may not all be merely an artifact of parturition.

Anesthesia, Conduction↗
PubMed1991

The predictive value of preoperative silent ischemia for postoperative ischemic cardiac events in vascular and nonvascular surgery patients.

Silent ischemia has been shown to be predictive of postoperative cardiac events in vascular surgery patients. However, no controlled data regarding its predictive value in nonvascular surgery patients are available. We studied 67 vascular surgery and 79 nonvascular surgery patients, all of whom had increased risk for cardiac disease, to determine whether the occurrence of preoperative silent myocardial ischemia is predictive of morbid postoperative cardiac events in a diverse surgical group. The presence of preoperative silent ischemia in both nonvascular and vascular surgical patients had similar predictive value (0.38 and 0.38, respectively) for postoperative morbid cardiac events. The absence of preoperative silent ischemia predicted an excellent outcome in patients undergoing nonvascular surgery (0.99), but was a less robust predictor in our vascular patients (0.86). These data suggest that the functional status of the coronary circulation is one of the most important determinants of outcome.

Aged↗
PubMed1990

A parallel software architecture for building intelligent medical monitors.

Intensive care units become more complicated each day as the number of devices developed to monitor various aspects of a patient's status continues to increase. Intelligent monitors attempt to reduce this complexity by interpreting the data and presenting a high level summary to the clinician. We propose an innovative parallel software architecture for constructing intelligent medical monitors: the process trellis. The process trellis is an explicitly parallel structure, and therefore can take advantage of the performance gains available from parallel computing hardware. It does not, however, presuppose any expertise in parallel programming on the part of the application programmer. A prototype cardiovascular monitor has been built using this parallel software architecture. Preliminary testing of the monitor has shown that real-time cardiovascular monitoring, including data calculations, symbolic classification, and interpretation can be accomplished in real-time.

Expert Systems↗
PubMed1990

Emergency tracheal intubation in the postanesthesia care unit: physician error or patient disease?

Inadequate airway maintenance has been a major factor in perioperative morbidity. To determine the incidence and etiology of emergency tracheal intubations in the postanesthesia care unit (PACU), we retrospectively reviewed 13,593 consecutive admissions to our PACU from October 1986 through October 1988. Twenty-six patients (26/13,593 = 0.19%) required the insertion of an endotracheal tube while in the PACU. Seventy-seven percent (20/26) of the intubations occurred within 1 h of extubation and/or admission to the PACU. Intubation was more common at the extremes of age; 54% of those intubated were more than 60 yr old (P = 0.003); 19% were less than 3 yr old (P less than 0.05). Twenty-three percent of the intubated patients had undergone otolaryngologic procedures (P = 0.008). Interestingly, 73% of the intubations occurred during the months of January through June (P = 0.016). Median PACU admission scores were lower for the intubated group (P less than 0.001). There was no association between intubation and gender (P = 0.74), anesthetic technique (P = 0.41), or anesthetic agent (P = 0.49). Of the 26 intubations, 18 (69%) were considered to be directly related to anesthetic management. Despite the extremely low incidence of emergency tracheal intubation in a heterogeneous group of patients admitted to our PACU, preventable anesthesia-related etiologic factors including excessive sedative or anesthetic effect, inappropriate fluid management, persistent muscle relaxant effect, and upper airway obstruction contributed to the majority of these intubations.

Adolescent↗
PubMed1988

Intravenous fat emulsions and lung function: a review.

Numerous studies have reported varying degrees of apparent pulmonary dysfunction when iv fat emulsions (IVFE) are given. These changes have generally not been of sufficient magnitude to carry clinical significance. The lung dysfunction observed has been attributed to an associated hyperlipemia. Recent studies, however, suggest that the associated impairment in lung function is due to alterations in pulmonary vascular tone (which results in ventilation/perfusion inequalities) caused by an IVFE-related increase in prostaglandin (PG) production. The polyunsaturated fatty acids in the IVFE serve as precursors to the PGs. Due to the varied effects of PGs on inflammation and pulmonary vasomotor tone, infusion of IVFE could have profound physiologic and pharmacologic actions aside from the provision of lipid calories. In some circumstances, IVFE may, in fact, be beneficial to the lung via alterations in

Animals↗
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

Improved exercise tolerance with long-term parenteral nutrition in cystic fibrosis.

Two cystic fibrosis (CF) patients with severe pulmonary disease and malnutrition were followed during a course of long-term home total parenteral nutrition (TPN), which included iv fat emulsion. They gained 7 and 12 kg in body weight, respectively, and their ability to participate in daily activities increased. Progressive exercise testing before and during TPN showed a marked increase in maximal work load: 100% and 30%, respectively. At any given work load, oxygen uptake was increased while the respiratory quotient remained lower after the course of TPN. We believe that the lower respiratory quotient and greater oxygen consumption during exercise were due to a reduction in anaerobic metabolism after TPN.

Adult↗
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

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↗
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↗
PubMed1979

Patterns of ventilation in postoperative and acutely ill patients.

Acutely ill patients commonly increase minute ventilation (V) to varying degrees. The pattern of breathing utilized to increase V was analyzed in normal subjects and acutely ill surgical patients. V = tidal volume (VT) x frequency (f), or V = inspiratory flow x (TI/TTOT, inspiratory time/total cycle time). CO2 inhalation and exercise were used to induce supine hyperventilation in normal subjects. This was compared to hyperventilation in acutely ill surgical patients. Measurements were made of O2 consumption, CO2 production, V, VT, f, inspiratory flow, TI, and TTOT. With small increases in V (up to twice control), normal subjects increased inspiratory flow and TI/TTOT with both CO2 and exercise. CO2 inhalation increased VT with no change in f, while exercise increased both VT and f. When V increased beyond twice control, TI/TTOT remained constant and increases in inspiratory flow accounted for the entire increase in V. In acutely ill patients with increased V, average f was elevated and VT decreased, but there was no constant relationship of f and VT with increasing V. However, TI/TTOT was relatively constant at 0.40- 0.46; therefore, in order to increase V, inspiratory flow had to increase! Patients also showed a tendency to breathe at a relatively fixed VT while normal subjects did not show this phenomenon, even with increases of up to 3 times control V. Continuous, rapid analysis of gas exchange and breathing patterns holds promise for early detection of patients with V inappropriate to metabolic demands, and serves as a sensitive indicator of abnormal patterns used by acutely ill patients to increase V.

Acute Disease↗