II. FINDINGS AND THEIR PATHOGENESIS

CHAPTER 10 — HYPOVOLEMIA   77



EBM BOX 10-1



Hypovolemia*

Finding†

(Reference)



Sensitivity

(%)



Specificity

(%)



Present



82

58-88



2.8

3.1



NS

0.4



58



NS



0.3



82

79



NS

3.5



0.5

0.3



73-99

82

82



NS

NS

NS



0.5

NS

0.5



Skin, Eyes, and Mucous Membranes

Dry axilla6

50

Dry mucous mem49-85

branes of mouth and

nose5,7

Longitudinal furrows

85

on tongue7

Sunken eyes7

62

Abnormal skin turgor

73

(subclavicular area)5

Neurologic Findings

Confusion5,7

Weakness7

Speech unclear or

rambling7



Likelihood Ratio‡

if Finding Is



49-57

43

56



Absent



*Diagnostic standard: For hypovolemia, serum urea nitrogen to creatinine ratio is >25;

osmolarity >300 mOsm/L, or serum sodium >145-150 mEq/L.

†Definition of findings: For abnormal skin turgor, see text.

‡Likelihood ratio (LR) if finding present = positive LR; LR if finding absent = negative LR.

NS, not significant.

Click here to access calculator.

HYPOVOLEMIA

Probability

Decrease

Increase

–45% –30% –15%

+15% +30% +45%

LRs



0.1



0.2



0.5



Normal skin turgor

Absence of tongue furrows



1



2



5



10



LRs



Abnormal skin turgor (subclavicular area)

Dry mucous membranes

Dry axilla



area was more accurate than testing skin over the forearms.5 Absence of

tongue furrows and presence of normal skin turgor decrease the probability

of hypovolemia (LR = 0.3 for both findings). The presence or absence of

sunken eyes, weakness, or abnormal speech had little diagnostic value in

these studies. The finding of confusion also lacked diagnostic value, although

it is strongly associated with mortality in elderly patients with hypovolemia.5

Although poor capillary refill time has been advanced as a reliable sign

of hypovolemia, it lacked diagnostic value in one study.7

The references for this chapter can be found on www.expertconsult.com.



REFERENCES    77.e1



REFERENCES

1. Mange K, Matsuura D, Cizman B, et al. Language guiding therapy: the case of dehydration

versus volume depletion. Ann Intern Med. 1997;127:848-853.

2. Osler W. The Principles and Practice of Medicine (facsimile by Classics of Medicine library).

New York, NY: D. Appleton and Co; 1892.

3. Dorrington KL. Skin turgor: do we understand the clinical sign? Lancet. 1981;1:264-265.

4. Aquilar OM, Albertal M. Images in clinical medicine: poor skin turgor. N Engl J Med.

1998;338(1):25.

5. Chassagne P, Druesne L, Capet C, et al. Clinical presentation of hypernatremia in elderly

patients: a case control study. J Am Geriatr Soc. 2006;54:1225-1230.

6. Eaton D, Bannister P, Mulley GP, Connolly MJ. Axillary sweating in clinical assessment of

dehydration in ill elderly patients. Br Med J. 1994;308:1271.

7. Gross CR, Lindquist RD, Woolley AC, et al. Clinical indicators of dehydration severity in

elderly patients. J Emerg Med. 1992;10:267-274.



CHAPTER



11



Protein–Energy Malnutrition

and Weight Loss

PROTEIN–ENERGY MALNUTRITION

I.  INTRODUCTION

The most common cause of malnutrition worldwide is an inadequate food

supply, although in industrialized countries the cause is more frequently

increased nutrient loss (e.g., malabsorption, diarrhea, nephrotic syndrome)

or increased nutrient requirements (e.g., fever, cancer, infection, or surgery), or both. Among patients admitted to surgical services in industrialized nations, 9% to 27% have signs of severe malnutrition.1,2



II.  FINDINGS

In children of developing nations, there are two distinct syndromes of protein–

energy malnutrition: marasmus (profound weight loss, muscle wasting, and

fat wasting) and kwashiorkor (abdominal distention, edema, and hypopigmented hair). In industrialized countries, however, most malnourished

patients have less dramatic findings and present instead with combinations

of low body weight, atrophy of muscle and subcutaneous fat, weakness, and

various laboratory abnormalities (e.g., low albumin or other serum proteins).

A.  ARM MUSCLE CIRCUMFERENCE

Arm muscle circumference is a decades-old anthropometric measurement

of the amount of muscle in the arm, which theoretically reflects the total

amount of muscle or protein in the body. The clinician measures the upper

arm circumference (Ca, using a flexible tape measure) and the triceps skinfold thickness (h, using calipers) and estimates the arm muscle circumference (AMC) with the following formula*:

AMC = Ca − πh

*This formula assumes that the arm is a cylinder of only skin and muscle (i.e., disregards the

humerus). To derive this formula: (1) AMC = πd1 (d1 = diameter of muscle component of

the arm); (2) d1 = d2 – h (d2 = diameter of arm; h = skinfold thickness, which, since the skin

is pinched, actually includes a double layer of skin and subcutaneous tissue); (3) therefore,

AMC = πd1 = π(d2 – h) = πd2 − πh = Ca − πh. If the clinician desires to directly enter the

skinfold thickness in millimeters (mm) (as it is measured), 0.314 is substituted for π in the

formula (i.e., AMC and Ca are measured in centimeters [cm]).



78



CHAPTER 11 — PROTEIN–ENERGY MALNUTRITION AND WEIGHT LOSS   79



Age- and sex-standardized values of the normal AMC have been published.3 The technique for forearm muscle circumference is similar.

B.  GRIP STRENGTH

Based on the hypothesis that malnutrition influences the outcome of surgical patients and that muscle weakness is an important sign of malnutrition,

Klidjian in 1980 investigated 102 surgical patients and demonstrated that

hand grip strength accurately predicts postoperative complications.4 In his

method, the patient squeezes a simple hand-held spring dynanometer three

times, resting 10 seconds between each attempt, and the clinician records

the highest value obtained. (Patients with arthritis, stroke, or other obvious causes of weakness are excluded.)

Age- and sex-standardized values of normal grip strength have been published.5 Clinical studies of grip strength always test the nondominant arm,

but this may be unnecessary because studies show that both arms are similar.5



III.  CLINICAL SIGNIFICANCE

EBM Box 11-1 addresses the accuracy of physical examination in predicting significant postoperative complications among patients undergoing

major surgery. In these studies, complications are significant if they prolong

hospital stay, threaten the patient’s life, or cause death (e.g., sepsis, wound

infections, myocardial infarction, or stroke).

In these studies, the findings of reduced arm or forearm muscle circumference (likelihood ratio [LR] = 2.5 to 3.2), reduced grip strength (LR =

2.2), and low body weight (LR = 2) all modestly increase the probability

of postoperative complications. Normal grip strength decreases the probability of complications (LR = 0.4). Interestingly, the presence of recent

weight loss has little diagnostic value in predicting complications, possibly because this finding is seen not only in patients with weight loss from

malnutrition (which should increase complications) but also in overweight

patients who voluntarily lose weight before surgery (which should decrease

complications).



WEIGHT LOSS

I.  INTRODUCTION

Involuntary weight loss reflects either diuresis, decreased caloric intake, or

the increased caloric requirements of malabsorption, glucosuria, or a hypermetabolic state. In series of patients presenting with involuntary weight

loss (exceeding 5% of their usual weight), organic disease is diagnosed in

65% of patients (most commonly, cancer and gastrointestinal disorders,

although virtually any chronic disease may cause weight loss) and psychiatric disorders are diagnosed in 10% of patients (depression, anorexia

nervosa, schizophrenia). In 25% of patients, the cause remains unknown

despite at least 1 year of follow-up.13-17



80   PART 3 — GENERAL APPEARANCE OF THE PATIENT



EBM BOX 11-1



Protein–Energy Malnutrition and Major Surgical

Complications*

Likelihood Ratio‡

if Finding Is



Finding (Reference)†



Sensitivity

(%)



Specificity

(%)



Present



Absent



Body Weight

Weight loss >10%4,6–9

Low body weight4,7,8,10



15-75

11-35



47-88

83-97



1.4

2.0



NS

NS



26-38



83-91



2.5



0.8



14-42



85-97



3.2



0.8



33-90



46-93



2.2



0.4



Anthropometry

Upper arm muscle

circumference <85%

predicted4,7,8

Forearm muscle

circumference <85%

predicted4,7,8

Muscle Strength

Reduced grip

strength4,5,7,8,11,12



*Diagnostic standard: In each of these studies, disease is defined as a major postoperative

complication, including those prolonging hospital stay, threatening the patient’s life, or

causing death.

†Definition of findings (all findings from preoperative physical examination): For weight

loss >10%, (recalled usual weight − measured weight)/(recalled usual weight) >10%); for

low body weight, weight-for-height less than normal lower limit,10 <90% of predicted,4 or

<85% of predicted7,8; for predicted arm muscle circumference, published standardized values3;

for forearm muscle circumference <85%, <20 cm in men and <16.3 cm in women4,8; and for

reduced grip strength, specific thresholds differ but all correspond closely to published age- and

sex-standardized abnormal values from reference.5

‡Likelihood ratio (LR) if finding present = positive LR; LR if finding absent = negative LR.

NS, not significant.

Click here to access calculator.

PROTEIN-ENERGY MALNUTRITION

Probability

Decrease

Increase

–45% –30% –15%

+15% +30% +45%

LRs



0.1



0.2



0.5



Normal grip strength



1



2



5



10



LRs



Forearm circumference <85% predicted

Upper arm circumference <85% predicted

Reduced grip strength

Low body weight



CHAPTER 11 — PROTEIN–ENERGY MALNUTRITION AND WEIGHT LOSS   81



II.  CLINICAL SIGNIFICANCE

Weight loss is rarely due to occult disease, and most diagnoses are made

during the initial evaluation, including the patient interview, physical

examination, and basic laboratory testing.13,14,16,17

In patients with involuntary weight loss, the presence of alcoholism

(LR = 4.5) and cigarette smoking (LR = 2.2) increases the probability

that an organic cause will be discovered during 6 months of follow-up,

whereas prior psychiatric disease (LR = 0.2) and a normal initial physical

examination (LR = 0.4) decrease the probability of discovering organic

disease.18 Also, the patient’s perceptions of the weight loss—whether he

or she significantly underestimates or overestimates it—help predict the

final diagnosis. The patient is asked to estimate his or her weight before

the illness (W) and the amount of weight lost (E). The observed weight

loss (O) is the former weight (W) minus the current measured weight.

Significant underestimation of weight loss, defined as (O – E) greater than

0.5 kg, predicts an organic cause of weight loss with a sensitivity of 40%,

specificity of 92%, positive LR of 5.4, and negative LR of 0.6.19 Significant

overestimation of weight loss, defined as (E – O) greater than 0.5 kg, predicts

a nonorganic cause of weight loss with a sensitivity of 70%, specificity of

81%, positive LR of 3.6, and negative LR of 0.4.19

The references for this chapter can be found on www.expertconsult.com.



REFERENCES    81.e1



REFERENCES

1. Baker JP, Detsky AS, Wesson DE, et al. Nutritional assessment: a comparison of clinical

judgment and objective measurements. N Engl J Med. 1982;306(16):969-972.

2. Detsky AS, McLaughlin JR, Baker JP, et al. What is subjective global assessment of nutritional status? JPEN. 1987;11(1):8-13.

3. Frisancho AR. New norms of upper limb fat and muscle areas for assessment of nutritional

status. Am J Clin Nutr. 1981;34:2540-2545.

4. Klidjian AM, Foster KJ, Kammerling RM, et al. Relation of anthropometric and dynamometric variables to serious postoperative complications. Br Med J. 1980;281:899-901.

5. Webb AR, Newman LA, Taylor M, Keogh JB. Hand grip dynamometry as a predictor

of postoperative complications reappraisal using age standardized grip strengths. JPEN.

1989;13(1):30-33.

6. Windsor JA, Hill GL. Weight loss with physiologic impairment: a basic indicator of surgical risk. Ann Surg. 1988;207(3):290-296.

7. Klidjian AM, Archer TJ, Foster KJ, Karran SJ. Detection of dangerous malnutrition.

JPEN. 1982;6(2):119-122.

8. Hunt DR, Rowlands BJ, Johnston D. Hand grip strength—A simple prognostic indicator

in surgical patients. JPEN. 1985;9(6):701-704.

9. Katelaris PH, Bennett GB, Smith RC. Prediction of postoperative complications by clinical and nutritional assessment. Aust N Z J Surg. 1986;56:743-747.

10. Hickman DM, Miller RA, Rombeau JL, et al. Serum albumin and body weight as predictors of postoperative course in colorectal cancer. JPEN. 1980;4(3):314-316.

11. Davies CWT, Jones DM, Shearer JR. Hand grip—a simple test for morbidity after fracture

of the neck of the femur. J Royal Soc Med. 1984;77:833-836.

12. Mahalakshmi VN, Ananthakrishnan N, Kate V, et al. Handgrip strength and endurance

as a predictor of postoperative morbidity in surgical patients: can it serve as a simple bedside test? Int Surg. 2004;89:115-121.

13. Rabinovitz M, Pitlik SD, Leifer M, et al. Unintentional weight loss: a retrospective analysis of 154 cases. Arch Intern Med. 1986;146:186-187.

14. Marton KI, Sox HC, Krupp JR. Involuntary weight loss: diagnostic and prognostic significance. Ann Intern Med. 1981;95:568-574.

15. Lankisch PG, Gerzmann M, Gerzmann JF, Lehnick D. Unintentional weight loss: diagnosis and prognosis: the first prospective follow-up study from a secondary referral centre.

J Intern Med. 2001;249:41-46.

16. Thompson MP, Morris LK. Unexplained weight loss in the ambulatory elderly. J Am

Geriatr Soc. 1991;39:497-500.

17. Metalidis C, Knockaert DC, Bobbaers H, Vanderschueren S. Involuntary weight loss:

does a negative baseline evaluation provide adequate reassurance? Eur J Intern Med.

2008;19:345-349.

18. Bilbao-Garay J, Barba R, Losa-Garcia JE, et al. Assessing clinical probability of organic

disease in patients with involuntary weight loss: a simple score. Eur J Intern Med.

2002;13:240-245.

19. Ramboer C, Verhamme M, Vermeire L. Patients’ perception of involuntary weight loss:

implications of underestimation and overestimation. Br Med J. 1985;291:1091.



CHAPTER



12



Obesity

I. INTRODUCTION

Obesity increases the risk of coronary artery disease, diabetes, hypertension, osteoarthritis, cholelithiasis, certain cancers, and overall mortality.1

Clinicians have recognized the hazards of obesity for thousands of years.

(According to one Hippocratic aphorism, “Sudden death is more common

in those who are naturally fat than in the lean.”2) Two thirds of adults in

the United States are overweight or obese.3



II. FINDINGS AND THEIR SIGNIFICANCE

Several different anthropometric parameters have been used to identify

those patients at greatest risk for the medical complications of obesity. The

most important ones are body mass index, skinfold thickness, waist-to-hip

ratio, waist circumference, and sagittal diameter.

A. BODY MASS INDEX

1. Findings

The body mass index (BMI, or Quetelet index) is the patient’s weight in

kilograms divided by the square of the height in meters (kg/m2). If pounds

and inches are used, the quotient should be multiplied by 703.5 to convert the units to kg/m2. An individual is overweight if the BMI exceeds 25

kg/m2, and obese if the BMI exceeds 30 kg/m2.4

The BMI was derived by a 17th century Belgian mathematician and

astronomer, Lambert-Adolphe-Jacques Quetelet, who discovered that this

ratio best expressed the natural relationship between weight and height.5

2. Clinical Significance

The BMI is an easy and reliable measurement that correlates well with

precise measures of total body fat (r = 0.70 to 0.96), much better than other

formulas of weight (W) and height (H) (e.g., W/H, W/H3, W/H0.3).6 The

BMI also correlates significantly with a patient’s cholesterol level, blood

pressure, incidence of coronary events, and overall mortality.1,7-10

The arbitrary cutoff of 25 kg/m2 was chosen in part because it reflects

the level at which there is a significant increase in mortality, although

increased rates of some complications such as diabetes appear at lower cutoffs.7,11 Many studies of BMI and mortality revealed a J-shaped relationship

82



CHAPTER 12 — OBESITY   83



(i.e., both lean and overweight patients have increased mortality), but the

increased risk of lean individuals is related to their age, cigarette use, and

illness-related weight loss.9,10

B. SKINFOLD THICKNESS

Another measure of obesity is “total skinfold thickness,” which is estimated

by adding together the skinfold thickness (measured with calipers) of multiple sites (mid-biceps, mid-triceps, subscapular, and suprailiac areas). These

sums are then converted by formulas into estimates of total body fat, which

correlate well with more precise measures (r = 0.7 to 0.8).6 Skinfold measurements are rarely used today, partly because they are too complex but mostly

because relatively few studies show that the number is clinically significant.

C. WAIST-TO-HIP RATIO

1. Findings

The waist-to-hip ratio (WHR) is the circumference of the waist divided by

that of the hips. It is based on the premise that the most important characteristic of obesity is its distribution, not its quantity. Abdominal obesity

(also called android, upper body, or apple-shaped obesity; Fig. 12-1) has

a much worse prognosis than gluteal-femoral obesity (also called gynoid,

lower body, or pear-shaped obesity).

Most authorities measure the waist circumference at the midpoint

between the lower costal margin and the iliac crest and the hip circumference at the widest part of the gluteal region. Adverse health outcomes

increase significantly when the WHR exceeds 1 in men and 0.85 in women,

values that are close to the top quintiles in epidemiologic studies.13

The French diabetologist Jean Vague is usually credited with making the

observation in the 1940s that abdominal obesity, common in men, is associated with worse health outcomes than obesity over the hips and thighs,

more common in women. (American life insurance companies, however,

made the same observation in the late 1800s.14) Vague’s original “index

of masculine differentiation,” a complicated index based on skinfold and

limb circumferences,12 is no longer used, having been replaced by the much

simpler WHR in the 1980s.

2. Clinical Significance

Even after controlling for the effects of BMI, the WHR correlates significantly with blood pressure, cholesterol level, incidence of diabetes mellitus,

stroke, coronary events, and overall mortality.8,13,15

3. Pathogenesis

The main contributor to abdominal obesity is visceral fat (i.e., omental,

mesenteric, and retroperitoneal fat), not subcutaneous fat. Visceral fat is

metabolically active, constantly releasing free fatty acids into the portal

circulation, which probably contributes to hyperlipidemia, atherogenesis,

and hyperinsulinemia.16 Gluteal-femoral fat, on the other hand, is metabolically inactive except during pregnancy and the postpartum period,