Protein and glucose fuel kinetics and hormonal changes in elderly trauma patients

Effect of age, stress and protein supply on plasma amino acids during continuous enteral nutrition; a pragmatic study in rats

BACKGROUND & AIMS

As life expectancy increases, an increasing older population may require surgery with perioperative nutritional management. While little is known about the combined effect of age and stress on amino acid metabolism during enteral nutrition, we hypothesized that blood amino acid bioavailability may be influenced not only by the characteristics of the ingested protein but also by intestinal ageing and splanchnic sequestration of amino acids. Plasma amino acid kinetics were thus evaluated in aged and adult rats receiving continuous enteral nutrition before and after standardized surgical stress.

METHODS

Sixteen 5-month-old and sixteen 21-month-old male rats were used. After a gastrostomy, the insertion of a jugular vein catheter and a one-week recovery, the animals were enterally fed with commercially available formulas containing whole milk proteins or a whey hydrolysate for 24 h before (healthy state) and 18 h after a standardized laparotomy (surgical stress). Data were analyzed by 3-factor ANOVA.

RESULTS

In all rats, enteral nutrition was associated with a marked increase in plasma alanine, threonine, lysine and proline (+50 to +150 μmol/L; p < 0.001), and a decrease in glycine (≈-80 μmol/L; p < 0.01). For most amino acids, their availability depended first on the amino acid composition of each protein and second on surgical stress. Aging was only associated with higher tyrosine and threonine availability (p < 0.001). There was only limited statistical interaction between age and surgical stress.

CONCLUSION

In rats, plasma amino acid availability during continuous enteral nutrition is determined by the nature of the protein source and the occurrence of stress. The effects of aging on plasma amino acid availability seem very limited. Commonly used formulas therefore appear to be as suitable for elderly patients as for adult patients.

Elderly patients may benefit from tight glucose control

BACKGROUND

While minimizing hyperglycemia in critically injured patients improves outcomes, it is debatable whether postinjury glucose control should aim for conventional glucose control levels (≤180 mg/dL) or tight glucose control levels (81-108 mg/dL). We queried our 17-year prospective database of patients at risk for postinjury multiple organ failure to examine the association between glucose levels and adverse outcomes.

METHODS

Acutely injured patients admitted to a Level I trauma center intensive care unit from 1992 to 2008 who were more than 15 years of age, had Injury Severity Scores >15, and who survived >48 hours were eligible for the study. Multiple logistic regression was used to determine the independent association of glucose control with adverse outcomes (death, ventilator-free days, intensive care unit-free days, and major infections), adjusted for Injury Severity Score, age, and red blood cell transfusion in the first 12 hours.

RESULTS

Overall, 2,231 patients were eligible, of whom 153 (6.9%) died. The mean age was 37.8 ± 0.4 years, and the median Injury Severity Score was 27 (interquartile range, 21-35). The majority (77%) of these patients maintained mean glucose within conventional glucose control levels and only 10% achieved mean glucose levels within tight glucose control levels. Nonsurvivors required greater doses of insulin to control glucose levels and had greater mean insulin to glucose ratios (t test; P = .025). After adjusting for confounders, mean glucose remained significantly associated with the studied adverse outcomes. Age significantly modified all these associations with older patients seeming to benefit more from tight glucose control levels than their younger counterparts.

CONCLUSION

Age is an effect modifier of the association between glucose levels and adverse outcomes. Future studies including larger samples of elderly trauma patients are needed to determine the ideal levels for glucose control in this growing population.

Hyperglycemia Has a Stronger Relation with Outcome in Trauma Patients than in Other Critically Ill Patients

BACKGROUND

Acute hyperglycemia is associated with adverse outcome in critically ill patients. Glucose control with insulin improves outcome in surgical intensive care unit (SICU) patients, but the effect in trauma patients is unknown. We investigated hyperglycemia and outcome in SICU patients with and without trauma.

METHODS

A 12-year retrospective study was performed at a 12-bed SICU. We collected the reason for admission, Injury Severity Scores (ISS), and 30-day mortality rates. Glucose measurements were used to calculate the hyperglycemic index (HGI), a measure indicative of overall hyperglycemia during the entire SICU stay.

RESULTS

In all, 5234 nontrauma and 865 trauma patients were studied. Trauma patients were younger, more frequently male, and had both lower median admission glucose (123 versus 133 mg/dL) and HGI levels (8.9 vs. 18.4 mg/dL) than nontrauma patients (p < 0.001). Mortality was 12% in both groups. Area under the receiver-operator characteristic for HGI and mortality was 0.76 for trauma patients and 0.58 for nontrauma patients (p < 0.001). In multivariate analysis, HGI correlated better with mortality in trauma patients than in nontrauma patients (p < 0.001). Head-injury and nonhead-injury trauma patients showed similar glucose levels and relation between glucose and mortality.

CONCLUSIONS

The relation of hyperglycemia and mortality is more pronounced in trauma patients than in SICU patients admitted for other reasons. The different behavior of hyperglycemia in these patients underscores the need for evaluation of intensive insulin therapy in these patients.

The end-product method of measuring whole-body protein turnover: a review of published results and a comparison with those obtained by leucine infusion

The present review summarizes the results of all published papers on whole-body protein turnover in man measured by [15N]glycine and the end-product method using both urea and ammonia. It begins with a short account of the underlying assumptions and the justification for the use of [15N]glycine. The results are then compared with those of a large sample of measurements by the 'gold standard' precursor method with continuous infusion of [13C]leucine. The pros and cons of the two methods are compared and it is suggested that there is a place for further work by the less invasive end-product method, particularly for population studies of the genetic, environmental and functional determinants of whole-body rates of protein synthesis.

The current status of road user injuries among the elderly in Germany: a medical and technical accident analysis

BACKGROUND

The incidence and treatment of injuries involving the elderly road user are of increasing importance for all fields of trauma care to ensure the best possible outcomes.

METHODS

Traffic accident reports were analyzed through technical and medical investigation for the involvement of elderly citizens.

RESULTS

In 12,309 documented traffic accidents between 1985 and 1998, 1,843 elderly citizens (65 years and older) were involved, 1,260 of which were reported to have been injured. The mean Injury Severity Score among the injured elderly citizens was 7.3. Of the injured elderly road users, 39.5% were car occupants, 27.4% were bicyclists, 29.6% were pedestrians, 1.8% were truck occupants, and 1.7% were motorcyclists. Of the elderly road users in cars, 53% were not injured, in contrast to only 1.1% of the bicyclists and 0.8% of the pedestrians. Serious or severe injuries (Maximum Abbreviated Injury Scale, >/=2] occurred for 36.5% of the injured elderly road users as car occupants (unrestrained, 58%; restrained, 34%), 57.4% as bicyclists, and 65.4% as pedestrians

CONCLUSION

A high rate of motor injuries is associated with vehicle accidents and increased levels of severity among the elderly population. This finding is especially evident for elder pedestrians and bicyclists. Also of note, the elderly even appear to be at risk for sustaining an increased level of injury severity when they are restrained or belt protected.

Age-related differences in the metabolic response to injury

OBJECTIVE

To investigate the effect of age on the metabolic response to injury.

METHODS

Fifty-two trauma patients meeting entrance criteria were prospectively enrolled. Patients were grouped by age: elderly, >60 years; and young, < or =60 years. After 4 days of nutrition support, physiologic and laboratory data were collected. Energy and nitrogen metabolism, and body composition were evaluated.

RESULTS

Elderly patients demonstrated a reduced incidence of fever (48% vs. 77%,p = 0.027). Independent of body composition, temperature, and injury severity, oxygen consumption was 8% lower in the elderly (p = 0.0032). However, nitrogen loss and myofibrillar catabolic rate was not altered by age. Elderly subjects were more often hyperglycemic (38% vs. 0%, p < 0.0001) and azotemic (62% vs. 22%, p = 0.004), despite similar carbohydrate and protein intake.

CONCLUSION

Fever is less common and oxygen consumption lower in elderly trauma patients. Postinjury myofibrillar protein catabolism and nitrogen loss are not influenced by aging. Metabolic complications of nutrition support (hyperglycemia, azotemia) are more common in elderly trauma patients.

Protein metabolism in rats during long-term dietary restriction: influence of aging

BACKGROUND

Protein depletion is frequent in the elderly, but the underlying mechanisms are not yet fully understood. In particular, it is unknown whether there is a defect of adaptation to a restriction of food intake in the elderly. This study was performed to compare the effects of 6-week dietary restriction (DR) on protein metabolism in both adult and aged rats.

METHODS

Adult (3-month-old) and aged (22-month-old) rats were acclimatized for 2 weeks and then fed a standard diet for 6 weeks, either ad libitum (control adult [C(Adult)] and aged [C(Aged)] rats) or with only 50% of the average intake of the second week of acclimatization (restricted adult [R(Adult)] and aged [R(Aged)] rats). Protein metabolism, in terms of tissue protein content, nitrogen balance, and 3-methylhistidine (3-MH) urinary excretion, was evaluated.

RESULTS

C(Adult) rats gained 30.4% of initial weight, whereas the body weight (BW) of C(Aged) rats was maintained. DR induced a rapid decrease in BW during the first 2 weeks in R(Adult) rats, but afterward BW remained stable. In R(Aged) rats, BW loss was linear during the 6 weeks and significantly higher than for R(Adult) rats (p<.01). In both restricted groups, muscle protein content was moderately affected by DR, whereas DR induced a marked decrease in visceral protein content. Nitrogen balance was decreased by DR but stayed positive in R(Adult) rats, whereas it became null in R(Aged) rats.

CONCLUSIONS

In terms of protein metabolism, aged rats adapted less efficiently than adult rats to a long-term dietary restriction.

Metabolic response to severe injury

BACKGROUND

Severe injury is associated with a complex sequence of metabolic events. The accurate quantification of these changes and a developing understanding of their aetiology has been the product of much work by researchers over the past 60 years. An understanding of these phenomena is vital to the practising surgeon because of the plethora of new metabolic modulators threatening to become part of clinical practice.

METHODS

This review describes the clinical picture of the metabolic response to severe injury and then outlines modern understanding of the underlying processes.

RESULTS AND CONCLUSION

The need for further research before introduction of new technologies is emphasized.