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Biomedical subjects

C Weissman

Publications and source records attributed to C Weissman.

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↗
PubMed1992

Flow-volume relationships during spontaneous breathing through endotracheal tubes.

OBJECTIVE: Breathing spontaneously through an endotracheal tube is often equated with "breathing through a straw." The objective of this study was to examine whether endotracheal tubes functionally act as tubular resistors in patients during tidal breathing, machine-initiated breaths, and vital capacity maneuvers. DESIGN: Descriptive study. SETTING: University hospital surgical ICU. PATIENTS: Eighteen mechanically ventilated, critically ill, postoperative patients (34 to 87 yrs). MEASUREMENTS: Flow-volume loops were recorded during tidal and machine breaths, as well as during vital capacity maneuvers. The loops were inspected visually for evidence of air flow limitation. Expiratory characteristics were examined using the ratio of expiratory volume in 1 sec to the expiratory volume in 0.5 sec and the ratio of expiratory volume in 1 sec to peak expiratory flow rate. The ratio of expiratory volume in 1 sec to that in 0.5 sec (greater than 1.5) and the ratio of expiratory volume in 1 sec to peak expiratory flow rate (greater than 10 mL/L/min) are seen with upper airway obstruction. MAIN RESULTS: Mean spontaneous tidal volume was 361 +/- 92 (SD) mL and vital capacity was 1104 +/- 16 mL, while the ratio of expiratory volume in 1 sec to that in 0.5 sec was 1.57 +/- 0.17 and 1.7 +/- 0.1 (p less than .05), respectively. The ratio of expiratory volume in 1 sec to peak expiratory flow rate was 9.9 +/- 1.7 during tidal breathing and 12.9 +/- 1.2 (p less than .05) during vital capacity maneuvers. CONCLUSIONS: Endotracheal tubes of the diameters used in these adult postoperative patients (7 and 8 mm) cause only minimal limitation to air flow during the small volumes and low-flow rates observed during tidal breathing. Evidence of greater air flow limitation was seen during vital capacity maneuvers.

Adult↗
PubMed1992

Postthoracotomy respiratory muscle mechanics during incentive spirometry using respiratory inductance plethysmography.

We undertook this study to characterize the postthoracotomy compartmental displacement and respiratory mechanical changes occurring during and after the performance of the incentive spirometry maneuver. We also evaluated the effect of recumbency angle on compartmental recruitment. Sixteen patients were randomized to perform incentive spirometry either at 30 degrees or 60 degrees recumbency angle. They were studied using respiratory inductance plethysmography to measure tidal volume, respiratory frequency, inspiratory time, rib cage motion/tidal volume ratio, inspiratory duty cycle, and inspiratory flow. Patients were studied before surgery and on postoperative days 1 and 3. Statistical analysis was accomplished using multiple measures ANOVA with post-hoc Student's t-tests when appropriate. Preoperative incentive spirometry augmented VT by increasing both VT/TI and TI. Postoperatively, the incentive recruitment of VT was reduced, a result of a decrease in TI and TI/TTOT; VT/TI was unchanged. There was postoperative decrease of AB and AB/VT during incentive spirometry, greatest in the 60 degrees group. Our results characterize the nature of the respiratory recruitment afforded by incentive spirometry, before and after thoracotomy. We also found evidence of postthoracotomy diaphragmatic derecruitment during incentive spirometry exacerbated by a high recumbency angle.

Female↗
PubMed1992

Patterns of sedation and analgesia in the postoperative ICU patient.

Control of pain, discomfort, and agitation is an integral part of the postoperative management of critically ill patients. We examined the sedative and analgesic practices in a surgical ICU during two six-month periods, one in 1986-1987 and the other in 1989-1990. Narcotics, especially morphine and Fentanyl, were the most commonly used drugs. The amount of Fentanyl received by the endotracheal patients in the 1986-1987 group was quite large, 5.5 +/- 4.3 (SD) mg/day. The use of midazolam during the second survey period was associated with a reduced dose of narcotics in artificially ventilated patients receiving continuous intravenous Fentanyl and morphine. The use of epidural Fentanyl, especially following thoracic surgery, was greatly increased during the second study period. More work is needed to assess the effects and effectiveness of ICU sedative and analgesic regimens.

Adult↗
PubMed1992

Evaluation of respiratory inductive plethysmography in the measurement of breathing pattern and PEEP-induced changes in lung volume.

STUDY OBJECTIVE: To assess the accuracy of the respiratory inductive plethysmography in the measurement of PEEP-induced changes in end-expiratory lung volume during mechanical ventilation and its accuracy and stability in the measurement of ventilation during controlled mechanical ventilation and spontaneous breathing. DESIGN: An open comparison between two methods using a criterion standard. Either a pneumotachometer (mechanically ventilated patients) or a spirometer (spontaneously breathing subjects) was used as the reference method. SETTING: Tertiary care center; a multidisciplinary intensive care unit and a metabolic research unit. PATIENTS: Six mechanically ventilated, paralyzed postoperative open heart surgery patients, six spontaneously breathing COPD patients, and eight healthy volunteers. INTERVENTIONS: Stepwise increases and reductions of PEEP from zero to 12 cm H2O during controlled mechanical ventilation; repeated validation of the calibration of the respiratory inductive plethysmography (RIP) in both mechanically ventilated and spontaneously breathing subjects. MEASUREMENTS AND RESULTS: The baseline drift of the RIP in vitro was 10 ml/150 min and in a ventilated model it was 20 ml/150 min. In mechanically ventilated patients, the mean error of the calibration after 150 min was within +/- 5 percent. Change in end-expiratory lung volume (EELV) during the stepwise increase of PEEP up to 12 cm H2O was 849 +/- 136 ml with the RIP and 809 +/- 125 ml with the pneumotachometer (PT), and during the stepwise reduction of PEEP it was 845 +/- 124 ml and 922 +/- 122, respectively (not significant [NS]. The mean difference between methods in the measurement of change in EELV was -6.6 +/- 3.5 percent during increasing and 6.6 +/- 6.7 percent during decreasing PEEP (NS). Both in mechanically ventilated and spontaneously breathing subjects, the difference between methods was significant for VT and VT/TI. The difference in VT was -2.2 +/- 0.2 percent during mechanical ventilation, -1.1 +/- 0.5 percent in spontaneously breathing COPD patients, and 2.9 +/- 0.4 percent in healthy volunteers (NS between groups). CONCLUSIONS: The RIP is sufficiently accurate for the measurement of PEEP-induced changes in EELV during controlled mechanical ventilation. The accuracy of tidal volume measurement is similar during mechanical ventilation and spontaneous breathing. The calibration of the RIP is stable enough for bedside monitoring of changes in lung volumes.

Adult↗
PubMed1992

Assessing hypermetabolism and hypometabolism in the postoperative critically ill patient.

To determine whether a patient is hypermetabolic or hypometabolic, measured resting energy expenditure is compared with estimated (or predicted) energy expenditure. The latter is calculated using equations derived from measurements made in groups of healthy individuals. Body weight or body surface area are among the variables used in these equations. Yet, in critically ill patients, body weight often rises because of fluid resuscitation. This study examined the differences between using preoperative, postoperative, and ideal body weights on the determination of hypermetabolism and hypometabolism in mechanically ventilated, critically ill patients. When the elevated postoperative weights were used instead of the preoperative ones to predict energy expenditure, the degree of hypermetabolism was underestimated. Subtracting the weight of the cumulative net fluid balance from the postoperative weight was found to accurately reflect preoperative weight. The influence of various predictive equations on the magnitude of hypermetabolism was also explored. In conclusion, it is important, when determining hypermetabolism or hypometabolism, to consider the influence of the specific predictive equation used and the effect of resuscitation fluid.

Aged↗
PubMed1991

Subthreshold argon-laser irradiation elicits a pronounced vitreal prostaglandin E2 response.

Chorioretinal production of prostaglandin type E2 (PGE2) as well as changes in vitreal protein and PGE2 concentrations were studied following retinal irradiation with low-power laser energy that caused ophthalmoscopically invisible ("subthreshold") laser burns. This was compared with changes following ophthalmoscopically visible ("suprathreshold") laser burns. Our results demonstrate that with in eyes exposed to the lower-power levels, the enhancement in vitreal PGE2 concentration persisted for a longer period and was more pronounced than in eyes exposed to the suprathreshold levels (a 3-fold and a 2-fold increase above baseline values, respectively). Protein leakage into the vitreous was noted only in the suprathreshold group, indicating a blood-retinal barrier (BRB) disruption. The findings of persistent, excessive PGE2 vitreal levels with no protein leakage in the subthreshold group suggest a possible anti-inflammatory role for PGE2 following low-power laser exposure.

Animals↗
PubMed1991

Argon laser irradiation of rabbits' eyes-changes in prostaglandin E2 levels.

Laser irradiation of the eye is a widely used therapeutic measure in various ocular disorders. We investigated in laser-treated rabbits' eyes the changes in prostaglandin E2 (PGE2) levels of the tissue affected by the laser (the retina/choroid) and of its adjacent vitreous over a two-week period. The parameters studied were; PGE2 in vitro production by the retina/choroid, as well as PGE2 and protein levels in the vitreous, the latter indicative of a break in the blood retinal barrier (BRB). The effect of noncoherent light exposure used for illumination, and that of the mechanical manipulation involved (sham exposure) were also studied. Following laser exposure vitreal PGE2 levels were increased two-fold above baseline (days three and 14), whereas light exposure resulted in a single peak. PGE2 in vitro production by the retina/choroid in the laser-exposed group was elevated throughout the observation period, peaking twice (days 3 and 14), in the light-exposed group the enhanced production was evident during a shorter period, whereas in the sham group it remained unchanged from baseline. An elevation in vitreal protein levels to above baseline levels occurred in both the laser- and, to a lesser degree, in the noncoherent light-exposed groups, but not in the sham group. Our study demonstrated an enhanced PGE2 in vitro production by retina/choroid of laser-exposed eyes, which might be attributable to the additive effect of the laser induced trauma, and the noncoherent light photochemical changes; the clinical significance of the recurrent increase in vitreal PGE2 levels in laser-treated eyes might be related to its anti-inflammatory properties.

Animals↗
PubMed1991

Prostaglandin E2 changes in the retina and optic nerve of an eye with injured optic nerve.

Changes in arachidonic acid metabolism were studied in the optic nerve, the chorioretina, and in the vitreous following crush injury to the optic nerve of rats. Crush injury led to: (i) a 3.9-fold increase in optic nerve prostaglandin type E2 in vitro production which peaked on day 5 and was followed by a gradual decline, but was still significantly higher than baseline levels by day 12; (ii) a two-fold increase in the chorioretina prostaglandin type E2 in vitro production which peaked on day 1, and resumed baseline levels by day 3; (iii) a 3.5-fold increase in vitreous prostaglandin type E2 levels on day 1 which remained at 1.5-2 times higher than baseline levels for the rest of the study period (12 days). The findings indicate that the pattern of changes in prostaglandin type E2 production by the optic nerve (consisting mostly of white matter) is different from that described for injured brain tissues. The prolonged accumulation of vitreal prostaglandin type E2 in eyes with damaged optic nerve may lead to undesirable effects on the retina beyond those directly manifested in the retina by altered axonal flow in the injured optic nerve.

Animals↗
PubMed1991

Prolonged corticosteroid treatment exerts transient inhibitory effect on prostaglandin E2 release from rabbits' eyes.

In humans, the retina and choroid (the photoreceptor and its vascular layers, respectively), are affected by an immunogenic inflammatory reaction--uveitis, associated with excessive levels of prostaglandin E2 (PGE2), and treated for prolonged periods with corticosteroids, known for their inhibitory effect on prostaglandins (PGs) production. In order to assess whether this drug retains its inhibitory effect during chronic use, we investigated the effect of long-term systemic administration of corticosteroids on PGE2 release by the choroid and retina of rabbits' eyes. We used eyes traumatized by laser irradiation, in which the inflammatory reaction is associated with an enhanced PGE2 in vitro release by the choroid-retina throughout a 2-week period; levels peaked on days 1 and 7 to values 2.2- and 5.5-fold, respectively, greater than baseline. Systemic corticosteroid administration to laser-exposed rabbits curtailed the excessive PGE2 release during the first post-laser week; later the amounts released progressively increased to levels 5.5-fold higher than baseline (day 14), whereas in the corresponding untreated laser group, levels were significantly lower. PGE2 tissue content on days 7 and 14 in steroid-treated and untreated laser groups were similarly elevated. We conclude that during prolonged systemic corticosteroids treatment the steroidal inhibitory effect on enhanced PGE2 formation by the retina-choroid of laser injured eyes is transient; it is evident during the early phase following drug administration, whereas later excessive PGE2 release is resumed.

Animals↗
PubMed1991

Respiratory patterns after cholecystectomy. Effects of posture and CO2 stimulation.

A marked reduction in the ratio of abdominal to rib cage motion has been observed after upper abdominal surgery. This study seeks to determine the effects on respiratory pattern of stimulation with CO2 and a change in posture from supine to semirecumbent posture (hips flexed, head of bed elevated at 30 degrees to the horizontal) in patients having undergone cholecystectomy. Canopy spirometry and respiratory inductive plethysmography were used to measure minute ventilation, tidal volume, and rib cage and abdominal motion in 14 otherwise healthy women, prior to elective cholecystectomy and on the first and third postoperative days. Preoperatively, the relative contribution of the chest wall compartment to tidal volume (Vc/VT) was increased both by moving from the supine to the semirecumbent posture and by stimulation with 4 percent inhaled CO2. On the first postoperative day, there was a reduction in abdominal motion. In contrast to what happened in the preoperative period, there was no change in the relative contribution of the rib cage and abdomen when the patients moved from the supine to semirecumbent position. With CO2 stimulation, there was a further increase in the already increased absolute tidal volume of the chest. On the third postoperative day, there was an increase in abdominal motion in the supine and sitting position and during 4 percent CO2 stimulation. These results demonstrate that the response to a change in posture and to 4 percent CO2 stimulation are markedly altered in the postoperative period by the reduction in abdominal motion.

Carbon Dioxide↗
PubMed1991

The oxygen uptake-oxygen delivery relationship during ICU interventions.

There is much interest in the relationship between oxygen delivery and oxygen consumption in the critically ill patient. This interest is occasioned by the observation that patients with sepsis and the adult respiratory distress syndrome have a linear or "supply-dependent" relationship instead of the normally observed biphasic or "supply-independent" relationship. These relationships are only valid when subjects are at rest, since during exercise, as VO2 increases, so do DO2 and the oxygen extraction ratio (ER, VO2/DO2). We examined the VO2-DO2 relationship in a group of 16 mechanically-ventilated surgical ICU patients while they were at rest and during activities that increase VO2. At low levels of activity, where mean VO2 increased from 207 +/- 38 (SD) ml/min at rest to 241 +/- 44 ml/min, there were significant increases in mean DO2 but not mean ER. With the greater (greater than 50 percent) increases in VO2 seen with chest physical therapy, there were increases in both DO2 and ER. When the VO2-DO2 relationship during low levels of exercise and rest are plotted, a linear pattern emerges that could be misinterpreted as a "supply dependent" pattern. Therefore, it is important to pay close attention to the activity state of a patient when examining the VO2-DO2 relationship.

Aged↗
PubMed1991

Continual trending of Fick variables in the critically ill patient.

We continually monitored components of the Fick equation (oxygen consumption, arterial and mixed venous oxygen saturation) simultaneously in ten hemodynamically stable, mechanically ventilated postoperative patients in order to evaluate our ability to continually calculate cardiac output (Qc) from its Fick determinants. Qc underestimated (p less than 0.001) cardiac output calculated from intermittent CO-oximeter measurements (6.2 vs 6.4 L/min) with good correlation (r = .96), while it consistently overestimated (p less than 0.05) thermodilution cardiac output (Qtd) (6.2 vs 5.9 L/min, r = .84). Measured oxygen consumption correlated with Qtd (r = .78) nearly as well as did Qc, while mixed venous oxygen saturation correlated poorly with Qtd (r = -.10). Trends of multiple Fick variables were helpful in interpreting changes in a single parameter. We conclude that continual trending of Fick variables in critically ill patients is both feasible and useful and that Qc agrees well with both traditional Fick cardiac output computed from CO-oximetry data and thermodilution measurements. Finally, measured oxygen consumption, available continuously, correlates well with changes in cardiac output in this subset of critically-ill patients.

Adult↗
PubMed1990

Different pathways mediate virus inducibility of the human IFN-alpha 1 and IFN-beta genes.

Multimerization of GAAANN generates sequences frequent in virus-inducible promoters. We distinguished different types of (GAAANN)4 sequences mediating virus inducibility. Type I (NN = GT, GC, CT, or CC) responds to IFNs and to IRF-1 and causes silencing. Type II (NN = TG) and type III (NN = CG) neither silence nor respond to IRF-1 or IFN. Type III mediates constitutive transcription and binds the constitutive IEFga factor, whereas type II binds the novel "TG protein". IFN-beta and IFN-alpha 1 promoters contain different response elements: The former has a type I-like sequence (PRDI) and an NF-kappa B-binding sequence (PRDII); the latter has a type II-like "TG sequence" and possibly additional elements but does not bind NF-kappa B. Type I, type II, and NF-kappa B elements represent three distinct terminal pathways mediating virus induction.

Animals↗
PubMed1990

Low-energy laser irradiation--a new measure for suppression of arachidonic acid metabolism in the optic nerve.

Helium-neon low-energy laser (LEL) irradiation, known for its therapeutic effects in arthritis, wound healing, and muscular strain, was applied to eyes of rats that had sustained an optic nerve crush injury. Crush injury to the optic nerve resulted in a long-lasting in vitro elevation of prostaglandin E2 (PGE2) production (1.8-3.9-fold above control values during the 12 day study period). LEL irradiation per se had no effect in vitro on PGE2 production by the optic nerve; however, LEL irradiation of eyes with crushed optic nerve inhibited the enhanced production of PGE2 and leukotriene B4 in vitro by 55% and 75% during the late and immediate phase after trauma, respectively. Our findings of the suppressive effect of LEL irradiation on arachidonic acid metabolism are reminiscent of the actions of steroidal and nonsteroidal anti-inflammatory drugs, and might indicate, for the first time, the possible biochemical mechanisms associated with the clinical anti-inflammatory effects of LEL irradiation.

Animals↗
PubMed1990

The correlation between excessive vitreal protein levels, prostaglandin E2 levels, and the blood retinal barrier.

Changes in vitreal protein and prostaglandin E2 (PGE2) concentrations, as well as chorioretinal in vitro PGE2 production, were studied in rabbit eyes following Neodymium (Nd):YAG laser retinal exposure. Laser exposure was associated with an enhanced vitreal PGE2 concentration throughout a two-week observation period, with highest levels on days 1 and 7 after exposure (a 5.3 and 4.7 increase above baseline, respectively). A transitory 50% elevation above baseline in vitreal protein levels was observed in the laser-exposed eyes during the second week after exposure. Laser exposure was also associated with an enhancement in the in vitro chorioretinal PGE2 production, which varied throughout the observation period, and was more pronounced during the first week after exposure, when levels were four times higher than baseline. Initially PGE2 vitreal levels were closely related to excessive in vitro production. However, during the second week after exposure, evidence of such correlation was lacking, but PGE2 vitreal levels coincided with a small increase in vitreal protein levels. It is suggested that disruption of the blood retinal barrier by the long-term exposure to mildly elevated vitreal PGE2 levels was accountable for protein leakage, which might have affected PGE2 removal mechanisms.

Animals↗