Effect of starvation and elective surgery on hand dynamometry and circulating concentration of various proteins

CORP: Measurement of upper and lower limb muscle strength and voluntary activation

Muscle strength, the maximal force-generating capacity of a muscle or group of muscles, is regularly assessed in physiological experiments and clinical trials. An understanding of the expected variation in strength and the factors that contribute to this variation is important when designing experiments, describing methodologies, interpreting results, and attempting to replicate methods of others and reproduce their findings. In this review (Cores of Reproducibility in Physiology), we report on the intra- and inter-rater reliability of tests of upper and lower limb muscle strength and voluntary activation in humans. Isometric, isokinetic, and isoinertial strength exhibit good intra-rater reliability in most samples (correlation coefficients ≥0.90). However, some tests of isoinertial strength exhibit systematic bias that is not resolved by familiarization. With the exception of grip strength, few attempts have been made to examine inter-rater reliability of tests of muscle strength. The acute factors most likely to affect muscle strength and serve as a source of its variation from trial-to-trial or day-to-day include attentional focus, breathing technique, remote muscle contractions, rest periods, temperature (core, muscle), time of day, visual feedback, body and limb posture, body stabilization, acute caffeine consumption, dehydration, pain, fatigue from preceding exercise, and static stretching >60 s. Voluntary activation, the nervous system’s ability to drive a muscle to create its maximal force, exhibits good intra-rater reliability when examined with twitch interpolation (correlation coefficients >0.80). However, inter-rater reliability has not been formally examined. The methodological factors most likely to influence voluntary activation are myograph compliance and sensitivity; stimulation location, intensity, and inadvertent stimulation of antagonists; joint angle (muscle length); and the resting twitch.

Alpha-1 Antitrypsin Investigations Using Animal Models of Emphysema

Animal models of disease help accelerate the translation of basic science discoveries to the bedside, because they permit experimental interrogation of mechanisms at relatively high throughput, while accounting for the complexity of an intact organism. From the groundbreaking observation of emphysema-like alveolar destruction after direct instillation of elastase in the lungs to the more clinically relevant model of airspace enlargement induced by chronic exposure to cigarette smoke, animal models have advanced our understanding of alpha-1 antitrypsin (AAT) function. Experimental in vivo models that, at least in part, replicate clinical human phenotypes facilitate the translation of mechanistic findings into individuals with chronic obstructive pulmonary disease and with AAT deficiency. In addition, unexpected findings of alveolar enlargement in various transgenic mice have led to novel hypotheses of emphysema development. Previous challenges in manipulating the AAT genes in mice can now be overcome with new transgenic approaches that will likely advance our understanding of functions of this essential, lung-protective serine protease inhibitor (serpin).

Monitoring Nutrition in Critical Illness: What Can We Use?

BACKGROUND

Nutrition monitoring in the context of critical care presents unique challenges. Traditionally used anthropometric and biochemical markers may be difficult to obtain or confounded by factors such as fluid status and the inflammatory response. A previous survey identified 15 parameters in common use, all of which have confounding influences during critical illness.

MATERIALS AND METHODS

A literature search was conducted to assess current use of commonly used nutrition-monitoring parameters and to explore other possible methods that might be more useful. More than 1000 journal articles were reviewed to identify indicators of nutrition status or nutrition progress that have been used in ICU studies. The most recent 200 articles were examined to quantify the number of occurrences for each indicator. Each parameter was rated for availability and feasibility in the ICU.

RESULTS

There were 53 parameters found, including the 15 already identified as commonly used; 27 were used in ≥3 recent studies. Less-well-established nutrition indicators with potential for use in the ICU (moderate or high feasibility and availability) included ultrasound measurement of arm or leg muscle thickness, fatigue scoring with the Chalder scale, urinary creatinine assay, and serum insulin-like growth factor 1 level. None of these was among the commonly used indicators in recent studies.

CONCLUSION

This study identifies commonly used nutrition-monitoring parameters and discusses their feasibility and availability in the critical care setting. Further investigation of nutrition indicators in ICU is needed, ideally as part of a randomized trial to reduce the effect of the many possible confounding factors.

Biological markers of protein-energy malnutrition

The biological markers of undernutrition fall into three categories: (a) those that measure structure; (b) those that measure function; and (c) indices of the above two. Ideally a marker of nutritional status should have the following characteristics: specific to nutritional status; sensitive to changes in nutritional status; reproducible; simple to measure; inexpensive and widely available. Unfortunately there are no such markers, and therefore individuals involved in the assessment of nutritional status should be aware of the advantages and disadvantages of the markers they use. For example, body composition can be assessed using sophisticated techniques that make fewer assumptions than simple bedside techniques (1). However, these sophisticated techniques (eg neutron activation, and combinations of techniques such as hydro-densitometry, water dilution techniques and dual-energy X-ray absorptiometry) are not widely available and some of them are labour intensive. On the other hand simple bedside techniques, such as those based on skinfold thicknesses can be applied widely because they are easy and quick to perform, but they are probably not as accurate as the classic body composition techniques (hydro-densitometry or water dilution techniques) or other sophisticated methods based on the assessment of multiple body compartments (1). Therefore the choice of method depends not only on the availability of investigative tools, but also on the practicalities of using them in individuals, a small group of individuals, or large groups of individuals, (eg national surveys during famine and non-famine conditions). In this brief review only some aspects concerned with simple bedside or laboratory methods will be discussed.

Low levels of plasma proteins: malnutrition or inflammation?

Levels of several plasma proteins, including albumin, transferrin, and transthyretin (prealbumin), have been proposed as markers for protein energy malnutrition. However, many other factors, especially inflammatory disease and drug or hormone therapy, affect levels of these proteins. These factors probably account for the majority of low levels of transthyretin. Levels of albumin and other proteins may be helpful in determining increased risk of morbidity and mortality, but better markers are needed for diagnosis of protein energy malnutrition per se.

International Federation of Clinical Chemistry. Laboratory assessment of protein-energy status

Laboratory and non-laboratory methods for assessing protein-energy nutritional status are reviewed. These are classified into methods for assessing adequacy of recent nutritional intake, methods for assessing whole body status, and tests which assist in the interpretation of these assessments. Each measurement is critically discussed in terms of the rationale for its use, the method of analysis, reference values, technical interference and limitations of methods, the effects of nutritional status and of other factors on the results, its overall usefulness in nutritional assessment, and its value relative to other methods. Non-laboratory tests such as dietary assessment, indirect calorimetry, functional tests and the many methods available for assessment of body composition, including anthropometry, bioelectrical impedance and isotope and imaging techniques, are compared with the clinical chemistry tests in common use, such as nitrogen balance, plasma protein measurements and urinary markers of muscle metabolism. This review provides comprehensive and practical advice on the use and limitations of these tests in the assessment of protein-energy nutritional status of a group, or of an individual patient.

Postoperative fatigue

Uncomplicated major surgery is followed by a pronounced increased feeling of fatigue extending throughout the first month in about one-third of patients. Postoperative fatigue correlates with the degree of surgical trauma but is not related to duration of general anesthesia and surgery or to preoperative nutritional status, age, or sex. Fatigue also correlates with postoperative deterioration in nutritional parameters and impaired adaptability of heart rate during exercise. Furthermore, a postoperative decrease in muscle force and endurance is related to postoperative fatigue, whereas psychological factors are of minor importance. These findings suggest postoperative fatigue to be mediated by the endocrine-metabolic response to surgery, impaired nutritional intake, or immobilization, but the relative role of these factors remains to be established. Until then, therapeutic measures against the development of postoperative fatigue should aim at reducing the surgical stress response, effective treatment of pain to facilitate mobilization, and exercise to increase postoperative nutritional intake.

Plasma-specific proteins: their response to surgical trauma and tumour load, and modification of this response by post-operative metabolic support

Concentrations of plasma proteins with short half-life have been suggested as indicators of nutritional state in surgical patients. Trauma also affects the circulating concentrations of these proteins. Serum concentrations of retinol binding protein (RBP), pre-albumin and transferrin were determined pre- and post-operatively on different supporting regimens. The circulating concentration of these liver proteins displayed no differential effect of the supporting regimen during the first 5 post-operative days. None of the patients with tumour demonstrated any indication of hepatic metastases pre-operatively or at the time of laparotomy but, as a group, had lower pre-operative concentrations of RBP (p < 0.001) and pre-albumin (p < 0.01) than patients with no tumour load. In addition 55% of patients (15:27) with tumour had RBP concentrations <3.5 mg/dl; all of the non-tumour bearing patients (13/13) had RBP concentrations >3.5 mg/dl. RBP and pre-albumin appear to act as non-specific tumour markers, but not to serve a useful function as short-term nutritional markers of post-operative support.

Effect of starvation on work capacity and voluntary skeletal muscle function in man

Post-operative fatigue is a well-known clinical problem even after uncomplicated surgery. In the multifaceted post-operative state, several factors other then the surgical trauma may influence muscular function, such as an insufficient nutritional intake. The aim of this study was to investigate the effect of fasting on work capacity and voluntary skeletal muscle function. Eight healthy lean volunteers, age range 25-43 years, were studied the day before starvation, at the end of the fasting period of 5 days, and after another 3-4 days on a normal diet. Hand grip strength was assessed as maximum voluntary contraction (MVC) and physical working capacity was investigated with successively increased work load on a cycle ergometer until near exhaustion. After 5 days of total starvation, MVC remained unchanged but physical working capacity was reduced from 220 +/- 18 watt to 199 +/- 22 watt (p < 0.05). Corresponding heart rate, estimated effort and leg tiredness were not changed. A poor nutritional intake per se may therefore be a less important factor causing post-operative muscle fatigue than the operation itself.

When is serum albumin worth measuring?

This paper critically examines the usefulness of serum albumin measurement in the light of current laboratory practice and knowledge of the pathophysiology of albumin metabolism. The main conclusions and recommendations are as follows: (i) Albumin measurement forms a limited, but useful part of the investigation of liver disease; a normal serum albumin concentration makes the diagnosis of cirrhosis unlikely, while a low level in viral hepatitis suggests either severe hepatocellular damage or other complications. (ii) Albumin measurement is essential in selecting patients for, and in determining the amount and frequency of, albumin replacement. (iii) Serum albumin concentration provides a useful indication of prognosis in myeloma. (iv) In the long-term management of patients undergoing enteral or parenteral nutrition, serum albumin concentration is one of several parameters which, together, are useful in predicting the outcome of treatment. (v) The serum albumin concentration may provide a clue to the aetiology of unexplained oedema. (vi) Serum albumin measurement is useful in indicating the level of ionised calcium and of unbound unconjugated bilirubin.

A new prognostic index in surgery and parenteral feeding: the ratio of triiodothyronine to reverse triiodothyronine in serum (T3/rT3 ratio)

Serum concentrations of albumin, triiodothyronine (T3), and reverse triiodothyronine (rT3) were measured in 46 patients on the first day after routine gastrointestinal surgery, and the molar ratio T3/rT3 was calculated. The median value of this ratio, but not of albumin, was significantly lower in 11 who subsequently suffered major septic complications than in the remainder. Measurement of the ratio correctly predicted the outcome of 80% of individuals. The T3/rT3 ratio, midarm muscle circumference (MAMC), triceps skin fold (TSF) and serum concentrations of albumin and transferrin were measured in 23 patients at referral for parenteral feeding. Median values of T3/rT3 ratio, MAMC and transferrin, but not of the other parameters, were significantly lower in nine who died than in survivors. Measurements of the ratio, MAMC and transferrin correctly predicted the outcome of 87%, 78% and 74% of individuals, respectively.

The effect of starvation on skeletal muscle function in man

Measuring skeletal muscle function may be a diagnostic aid to detect malnutrition. To evaluate this hypothesis 11 lean women were studied before and after 5 days of total starvation. Skeletal muscle function was assessed as hand grip strength and as adductor pollicis muscle function after electrical stimulation of the ulnar nerve. The muscle function variables were force of contraction at 5, 10, 20 and 50 Hz stimulation, relaxation rate and endurance. In addition some currently used anthropometric and biochemical nutritional indices were serially determined. Hand grip strength was decreased (p < 0.05) and the function of the adductor pollicis muscle was altered with a higher contraction force at 10 Hz (p < 0.01), a slower relaxation rate (p < 0.05) and a reduced endurance (p < 0.05). These changes were all within the normal ranges. Triceps skin fold and arm muscle circumference were not changed after a mean weight loss of 3.3 kg (p < 0.05). However blood glucose, insulin and triiodothyronine all decreased (p < 0.01) indicating a metabolic adaptation to starvation. Prealbumin (p < 0.05) and fibronectin (p < 0.01) were also lowered. In conclusion, skeletal muscle function was significantly altered after five days of total starvation. However, to identify short term nutritional depletion in clinical practice the changes in muscle function were too small to be diagnostically useful.

Effects of surgery and nutritional support on some lymphocyte and PMN leucocyte functions in man

The purpose of the present study was to evaluate the effect on some leucocyte functions of 1) an elective surgical procedure; 2) nutritional repletion provided by parenteral alimentation (TPN). The rates of cellular proliferation and protein synthesis in lymphocyte cultures were measured by the incorporation of respectively 3H-thymidine and 3H-leucine; both measures were performed without and with additions of mitogenic agents. Random migration and chemotaxis of PMN leucocytes were measured under agarose. In 10 well-nourished patients, both lymphocyte proliferation and protein synthesis in stimulated cultures decreased after elective surgery, respectively by 50% (p < 0.01) and by 32% (p < 0.05) while random migration of PMN leucocytes was increased by 50% (p < 0.02). Stimulated lymphocyte proliferation and protein synthesis measured in 10 nutritionally depleted non-cancer patients prior to TPN were lower in comparison to the values obtained in a control population (respectively p < 0.006 and p < 0.04). These parameters rose progressively during TPN and reached the normal range after 3 weeks. Before TPN, PMN leucocyte random migration was slower in depleted patients than in control subjects; this parameter reached normal values after one week of TPN, while chemotaxis tended to decrease. Both parameters were in the normal range after 3 weeks of TPN. Conclusions 1) an elective operation depresses lymphocyte functions but stimulates PMN leucocyte random migration in well-nourished patients; 2) in depleted patients, previously depressed leucocyte responses are restored within 3 weeks of adequate nutritional support.

The measurement of albumin in serum and plasma

This publication was prepared at the invitation of the Analytical Methods Working Party of the Scientific Committee of the Association of Clinical Biochemists, but does not necessarily reflect the views of the Scientific Committee.