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Biomedical subjects

M M Meguid

Publications and source records attributed to M M Meguid.

At least 127 records · Page 7Linked to original sources
PubMed1992

A critical appraisal of the usefulness of perioperative nutritional support.

Preoperative malnutrition is often associated with poor postoperative outcome, yet there is no consensus about whether perioperative nutritional support reduces postoperative complications to the level occurring in well-nourished patients undergoing similar procedures. This is partly because reports evaluating effect of perioperative nutritional support on postoperative outcome vary widely in number of patients studied, primary diagnosis, and duration and quality of perioperative nutritional support. These concerns warrant caution in interpreting reported results, even of randomized studies. However, analysis of published reports suggests that when total parenteral nutrition (TPN) is given to malnourished patients in adequate amounts for greater than or equal to 7-15 d preoperatively, significant improvements in both nutritional status and postoperative clinical outcome are likely to occur. Preoperative total enteral nutrition (TEN) is as effective as TPN in improving postoperative clinical outcome. Postoperative TPN, TEN, and ad libitum oral nutrition are equally effective in reducing postoperative complications. Potential candidates for surgery for whom prompt initiation of preoperative TPN or TEN may reduce operative morbidity and mortality irrespective of nutritional status can be identified on admission.

Enteral Nutrition↗
PubMed1992

Rapid bedside method to assess changes in postoperative fluid status with bioelectrical impedance analysis.

BACKGROUND: Estimates of daily postoperative fluid balance usually rely on properly recorded inputs, outputs, and daily weights or clinical signs. These may be imprecise (when poorly done) and are often considered tedious to perform. METHODS: We used bioelectric impedance analysis (BIA) to assess changes in body water shifts in cardiac patients after surgery. Nine consecutively admitted patients undergoing coronary artery bypass (seven men and two women; age range, 43 to 67 years) were studied. Body weight, fluid intake and output, and BIA variables (resistance and reactance) were measured daily. Relationships between body weight and changes in resistance and reactance and net change in fluid balance (in liters per day) were evaluated statistically by regression analysis. RESULTS: Mean body weights changed significantly, reflecting early operative fluid accumulation and later postoperative diuresis; net fluid balance correlated poorly (r = 0.48; p less than 0.05) with body weight, whereas both resistance (r = -0.82; p less than 0.001) and reactance (r = -0.92; p less than 0.0001) correlated highly with net fluid balance. CONCLUSIONS: BIA is useful as an accurate, rapid bedside method for assessing changes in hydration status sequentially after surgery in cardiac patients with complicated fluid shifts.

Adult↗
PubMed1992

Influence of parenteral feeding on spontaneous caloric intake and food selection in rats.

We compared spontaneous caloric intake (SCI) of rats exclusively receiving chow to SCI of rats given the choice of chow or Parmesan cheese, and then examined the influence of parenteral feeding on SCI and food selection. Six rats in a Chow Diet Group were offered Purina chow for 21 days, while five rats in a Choice Diet Group were offered Parmesan cheese or the same chow. Daily SCI (kcal/day) and body weight gain (BWG; g/day) were determined. Rats in the Choice Diet Group ate twice as much cheese as chow for the first 3 days of the experiment. Thereafter, SCI and BWG became comparable in both groups, with no significant differences for the rest of the study. In another group of nine rats, a central venous catheter was inserted. After 7 days, rats were offered chow and water ad libitum during the infusion of normal saline at 3 ml/hour for 3 days (Saline). Then, normal saline was replaced by a total parenteral nutrition (TPN) mixture of glucose, fat, and amino acid providing 85 kcal/day, and rats were randomized to eat either Chow Diet or Choice Diet. In both groups, SCI during TPN was significantly reduced as compared to the SCI on Saline. However, rats in the Choice Diet Group ate three times more chow than cheese during TPN. We conclude that a) food preference can increase SCI for short periods of time; b) TPN reduces SCI; c) TPN modifies food preference; and d) food preference does not increase SCI during TPN.

Animals↗
PubMed1991

Effect of intravenous or intragastric nutrients on food intake in rats.

A series of experiments were performed to determine which components of total parenteral nutrition (TPN) reduce spontaneous food intake (SFI) and to what degree. In Experiment 1, rats were infused with TPN (15% dextrose + 5% fat + 4.3% amino acid) or with one of its three components given independently at the final concentration of TPN for 3 days via an intravenous (iv) catheter. Each solution, at 3 ml/hr, provided a different amount of calories (TPN = 85, dextrose = 37, fat = 36, and amino acid = 12 kcal/day), representing about 120, 50, 50, and 20% of the rat's spontaneous caloric intake, respectively. TPN, dextrose, and fat significantly reduced SFI compared to the infusion of normal saline; however, amino acid failed to reduce SFI. Experiment 2 was carried out to investigate the relative contributions that pre- and postabsorptive mechanisms make in the regulation of SFI. Each rat in four different groups was infused with one of four isocaloric nutrient solutions through an iv catheter and a gastrostomy (ig) for separated periods of time. Nutrient solutions at 3 ml/hr provided each 32 kcal/day (50% of requirements): 13% dextrose, 4.5% fat, 11.4% amino acid, and a mixture (6.4% dextrose + 1.6% fat + 1.7% amino acid). Each solution, either iv or ig, reduced SFI compared to normal saline infused via the same route. However, neither the route of administration nor the nature of different nutrients caused significant differences in SFI reduction.

Animal Nutritional Physiological Phenomena↗
PubMed1991

Change in meal size, number and duration after neural isolation of liver and with TPN.

The abundant neural connections between the liver and hypothalamus suggest that the liver contributes to spontaneous food intake (SFI) regulation. This hypothesis was tested in rats after total liver denervation (TLD) and infusing TPN. A sham operation (SO) or TLD was performed in Fischer rats, placed in metabolic cages fitted with an Eater Meter to measure SFI, meal number (MN), size (MZ), and duration (MD). Rats had free access to chow and water. After 22 days, a jugular catheter was placed and normal saline continuously infused for 10 days (days 22-32). Then TPN-100, providing 100% of rats daily energy needs, was infused for 3 days (days 32-35). During the post-SO/TLD and postjugular catheterization periods and during TPN-100, SFI was the same in SO controls and TLD group. However, TLD rats had decreased MZ and MD (interpreted as early satiety) and increased MN (interpreted as increased hunger) to maintain the same SFI as control rats. Although total SFI was not influenced by TLD, it significantly affected feeding pattern, suggesting that the neural isolation of the liver from the brain produces altered hypothalamic regulation of not only the onset of feeding, but also satiety.

Animals↗
PubMed1991

Effects of continuous graded total parenteral nutrition on feeding indexes and metabolic concomitants in rats.

The influence of graded amounts of total parenteral nutrition (TPN) on food intake and feeding indexes was investigated in 90 rats housed in Automated Computerized Rat Eater Meter metabolic cages with free access to water and chow. When food intake was stable after catheter placement, 10 control rats continued with the 3 ml/h normal saline used for catheter patency, whereas study rats were given graded TPN continuously for 3 days, amounting to the equivalent of 26% (TPN-26), 53% (TPN-53), 81% (TPN-81), or 114% (TPN-114) of their daily caloric needs. TPN consisted of glucose, fat, and amino acids in the caloric ratio of 50:30:20. In study rats, the graded TPN depressed food intake, meal number, meal size, and eventually food consumption rate, meal sniffs, and intermeal sniffs in a dose- and time-dependent manner. During graded TPN, rats decreased total food intake by eating fewer, smaller, shorter meals at a decreasing consumption rate; sniffing activities were correspondingly curtailed. Stopping TPN led to normalization of feeding indexes. Blood glucose did not change while plasma insulin rose with graded TPN. A decrease in hepatic glycogen and an increase in hepatic triglycerides occurred. Plasma valine, phenylalanine, and methionine rose in a TPN dose-dependent manner. TPN-26 and TPN-53 significantly decreased whole brain amino acids; with TPN-114 no change occurred. Brain influx of tryptophan remained unchanged, but a progressive decrease in brain influx of tyrosine occurred. Whole brain dopamine and serotonin were depressed with TPN-26 and TPN-81 but were normal with TPN-114.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1990

Liver biochemical and histological changes with graded amounts of total parenteral nutrition.

We sought to determine whether an excess in energy intake as total parenteral nutrition would result in liver biochemical and histological changes in the presence of a functional gastrointestinal tract. Three groups of rats were given amounts of total parenteral nutrition that provided either 25% (total parenteral nutrition-25), 100% (total parenteral nutrition-100), or 200% (total parenteral nutrition-200) of a rat's energy requirements. Rat chow and water were available ad libitum. Food intake decreased in proportion to the amount of total parenteral nutrition infused; it ceased with total parenteral nutrition-200. Liver glycogen and triglyceride concentrations were higher with high energy intake (total parenteral nutrition-100 and total parenteral nutrition-200), while total liver nitrogen concentrations remained unchanged. No cholestasis, inflammation, or fibrosis was seen histologically. Fatty vacuoles were increased with total parenteral nutrition (more so with total parenteral nutrition-200) but a prompt return to normal liver features was observed after cessation of total parenteral nutrition and the resumption of normal food intake.

Animals↗
PubMed1990

Automated computerized rat eater meter: description and application.

A real-time Automated Computerized Rat Eater Meter was developed by modifying commercially available metabolic cages. Food access via a feeding tunnel was monitored by photocells. Food consumption was measured by an electronic scale. The signals thus generated were processed by a computer. This allowed us to continuously measure the spontaneous feeding behavior of free-feeding nondeprived Fischer rats for a sum total of 35 study days. Based on our data, we defined a meal as an episode of food consumption preceded and followed by at least 5 minutes of no feeding. Fischer rats showed periodic nychthemeral eating behavior. Food consumption, number of meals, meal sniffs, intermeal sniffs, and, consequently, eating activity were greater during the dark cycle than the light cycle. Meal duration, meal size, and thus food consumption rates remained constant throughout both cycles. Our modification of commercially available metabolic cages provides unique data for continuously monitoring rat feeding patterns over prolonged periods of time.

Animals↗
PubMed1990

Nutritional support in surgical practice: Part I.

Critical evaluation of the therapeutic benefit gained from provision of nutritional support requires knowledge regarding the nutritional status of those to whom it was given. The apparent effect of giving parenteral nutrition or enteral nutrition depends not only on how much and how well it is given, but also on how depleted the recipient is. Thus, nutritional assessment requires close examination before proceeding to assess the efficacy and potential benefits of the remedial measures of parenteral nutrition or enteral nutrition. Although preoperative malnutrition is associated with a poor operative outcome, there appears to be no consensus as to whether perioperative nutritional support can reduce postoperative complications to the level occurring in well-nourished patients undergoing similar procedures. This is partly because reports evaluating the effect of perioperative nutritional support on postoperative outcome vary widely as to numbers of patients studied, primary diagnoses, and the duration and quality of perioperative nutritional support. In Part I, these issues are explored in patients who are undergoing operations for cancer, trauma, or burns. Enteral nutrition appears to be as effective as parenteral nutrition in improving operative outcome, as compared with ad libitum oral nutrition. Postoperative enteral nutrition and parenteral nutrition are equally effective in reducing postoperative complications.

Enteral Nutrition↗
PubMed1990

Nutritional support in surgical practice: Part II.

On admission, a group of high-risk patients who are potential candidates for surgery can be identified, in whom prompt initiation of preoperative enteral or parenteral nutrition may reduce postoperative morbidity and mortality irrespective of the nutritional status. Among these are patients with inflammatory bowel disease, gastrointestinal fistulas, and pancreatitis. Substantial nutritional support has little or no direct effect upon the pathogenesis of the disease, but the discontinuance of oral intake may well have a beneficial effect on the basic disease process. Thus, the provision of enteral or parenteral nutrition gives the patient an optimal opportunity to marshal host defenses in support of healing. In organ system failures, e.g., acute renal failure, liver failure, and pulmonary failure, appropriate nutritional support may assist the patient in coping with the abnormal intermediary metabolism resulting from such failure until satisfactory organ system function returns. From this review, it seems reasonably clear that the initially malnourished patient is less able to successfully withstand the adverse effects of vigorous therapy and/or severe illness than is the well-nourished individual. Hence, correction of malnutrition, either before initiating therapy or concomitant with the treatment, is very likely to be beneficial.

Acute Disease↗
PubMed1989

Ability of a benign tumor to decrease spontaneous food intake and body weight in rats.

Malignant tumors induce anorexia and decrease spontaneous food intake and weight loss. Whether these effects are in part due to the tumor's physical size was investigated by inducing a benign cystic tumor mass with carrageenan in rats and then studying them for 21 days. Forty-two control rats were given subcutaneous injection of 3 ml of normal saline. Fifty-six study rats were given 3 ml of a 1.5% carrageenan solution subcutaneously, both in the right flank. Daily spontaneous food intake, body weight, and tumor weight were measured. Eight study and six control rats were randomly sacrificed on days 1, 3, 5, 7, 10, 14, and 21. Blood was obtained by cardiac puncture for albumin determination, and the tumor, carcass, liver, and spleen were removed and weighed. Tumor and tissue samples were histologically examined. All rats injected with carrageenan developed a benign cystic tumor mass. Early cystic wall consisted mainly of foamy macrophages with a light lymphoplasmacytic chronic inflammatory infiltrate and moderate vascularization. At day 21, cystic wall was more compact. The vasculature had collapsed and there were more pronounced fibroblastic response and collagen bundles. Average tumor weight by day 21 was 41 g. Average spontaneous food intake was depressed by about 15% from day 8 on in study rats as compared to controls. A significant decrease in carcass weight of 15.2% was observed in study as compared to control rats at day 21. Serum albumin was significantly decreased in study rats after day 5. Liver weight was significantly lower and spleen weight higher in study rats as compared to controls. These data suggest that some characteristics associated with cancer anorexia can be found in the absence of malignancy.

Animals↗
PubMed1989

Comparisons of body composition derived from anthropometric and bioelectrical impedance methods.

This study compared bioelectrical impedance analysis (BIA) measurements with current bedside techniques for determination of body composition in 18 normal volunteers to evaluate the relative usefulness of these methods as adjuncts to assessment in surgical nutrition. Anthropometrics (weight, height, and two skinfold thicknesses) and age and sex were used to derive body density (D) or total body water (TBW) by two methods. Method 1: D was calculated from the logarithm of skinfold thickness according to Durnin and Womersley, adapted for age and sex. Method 2: TBW was calculated from height, weight, and sex according to Hume and Weyers. Resistance and reactance were measured with a four terminal impedance plethysmograph; from these data plus height, weight, and sex, lean body mass (LBM) was derived. In each instance, Siri's and Pace and Rathburn's equations were used to derive the remaining parameters of body composition: D, total body fat (TBF), TBW, and LBM. Using the paired t-test, no statistically significant differences were seen in any parameter determined by the different methods. These results show that D, TBW, TBF, and LBM in a population of healthy individuals under steady-state conditions can be estimated by anthropometric-derived formulas with the same relative accuracy as that provided from estimates based upon BIA measurements.

Adult↗
PubMed1989

Natural killer cell activity in rats infused with Intralipid.

The effect of Intralipid on the natural killer (NK) cell activity of healthy male Fisher 344 adult rats was investigated. They were cannulated via the right jugular vein and continuously infused for five days with: normal saline plus heparin, 5% Intralipid plus heparin, or 10% Intralipid plus heparin. Control groups comprised of cannulated rats receiving no infusion and rats undergoing no operative procedures. Following the five-day infusion, rats were exsanguinated under ether anesthesia and mononuclear cells (MNC) harvested from the peripheral blood. NK activity was measured in a standard four hour 51Cr release assay against YAC-1 target cells. NK cell activity in rats infused with 5% Intralipid did not differ significantly from rats in both control groups or rats infused with saline. Infusion of rats with 10% Intralipid resulted in a significant increase in NK activity compared with all other groups.

Animals↗
PubMed1989

Evaluation of nutritional status.

Most of the methods used for nutritional assessment provide information regarding body composition abnormalities. In addition to clinical evaluation, straight-forward physical measurements (such as body weight, anthropometric measures) and biochemical or immunological determinations are used. Sophisticated laboratory measurements are, at present, useful primarily for research purposes. Based on the results of nutritional assessment, a diagnosis as to type of malnutrition (and its treatment) may be made. Nutritional assessment criteria are also used to evaluate the effectiveness of nutritional support.

Body Composition↗
PubMed1989

Cannulation of inferior vena cava for long term central venous access.

Nineteen patients had a Silastic (silicone rubber) catheter placed into the inferior vena cava (IVC) by way of a vein of a lower extremity. All patients needed long term venous access but had conditions precluding access to the superior vena cava (SVC) or access sites of the upper torso. Precautions regarding operative technique for the placement of the catheter include incisions through healthy skin, maintenance of aseptic technique at the site of access, an atraumatic subcutaneous tunnel at least 25 centimeters in length and a long acting local analgesic effect. Catheters were in situ for a total of 2,215 days (a mean of 111 days per catheter). Catheters were also used to administer intravenously medications, blood and blood products, chemotherapeutic agents, parenteral nutrition and for sampling of blood. Four complications occurred: one instance each of catheter sepsis and infection of the subcutaneous tract and two of thromboses of the IVC. No deaths occurred. The complication rate was 0.18 per cent per catheter-day. Long term access to the IVC is feasible without undue concern in conditions in which access to the SVC is precluded but long term central access is essential.

Adult↗
PubMed1988

Amino acid profiles in tumor-bearing and pair-fed nontumor-bearing malnourished rats.

To investigate the metabolic and organ changes accompanying growth of a malignant tumor, ten male Fisher 344 rats weighing 150 to 200 g were inoculated subcutaneously with 10(6) viable MCA sarcoma cells (tumor-bearing). Ten other rats (controls) were similarly inoculated with saline. Both groups were allowed food and water ad libitum. An additional ten rats (pair-fed) were inoculated with saline and fed the same mean daily food intake as the tumor-bearing rats. Thirty-five days after inoculation the rats were killed by exsanguination. Livers, spleens, and tumors were weighed, and amino acid profiles and biochemical parameters were measured. Liver and spleen weights in tumor-bearing rats were significantly greater than control rats (P less than 0.05 and P less than 0.01, respectively). Liver weight in pair-fed rats was significantly less than control rats (P less than 0.01), but spleen weight was greater (P less than 0.01). Amino acid profiles of tumor-bearing rats and pair-fed rats were different from each other and from those of control rats. Branched-chain amino acids were lowest in tumor-bearing rats and significantly different from control and pair-fed rats. Lysine was significantly higher (P less than 0.01) and arginine significantly lower (P less than 0.05) in tumor-bearing rats compared with control rats. These different plasma amino acid profiles and changes in serum biochemistry of cachectic tumor-bearing rats compared with malnourished pair-fed rats suggest specific tumor effects on host metabolism not mediated solely by anorexia.

Amino Acids↗