metabolism in surgery

7/28/2019 Metabolism in Surgery

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Energy Metabolism and Normal Nutritional Requirements

FERNANDO L. LOPEZ, MD, FPCS

Professor of Surgery

UST Department of Surgery

Compiled and edited by Arvin 09-01-08

OBJECTIVES

To review normal protein, carbohydrate and lipid

metabolism

To understand the mechanisms that regulatesubstrate utilization and energy production

To demonstrate methods for calculating nutritional

requirements

NUTRIENTS

Protein 4 kcal / g

Carbohydrates

o enteral 4 kcal / g

o parenteral 3.4 kcal / g

Lipids 9 kcal / g

Water

Vitaminso Water soluble

o Fat soluble

Minerals

o Electrolytes

o Trace elements and ultra trace minerals

Amino Acids

• NON-ESSENTIAL

− Isoleucine − Alanine

− Phenylalanine

− Methionine− Histidine

− Tryptophan

− Tyrosine

− Aspartic Acid

− Glutamic Acid

− Cysteine

− Glycine

− Serine

− Proline

• CONDITIONALLY

ESSENTIAL

− Glutamine

− Arginine

• ESSENTIAL

− Leucine

− Lysine

− Valine

− Threonine

Chemical Structure of an Amino Acid

NITROGEN BALANCE

NB = IN – (UN + RNL)

NB: Nitrogen Balance

IN: Ingested Nitrogen

UN: 24-Hour Urine Nitrogen

RNL: Remaining Nitrogen Loss (3.1 g/d)

Respiratory Quotient (RQ)

RQ: Respiratory Quotient

VCO2: CO2 Produced

VO2: Oxygen Consumed

RQ

• Glucose oxidation

1 glucose + 6 O2 = 6 CO2 + 6 H20

6/6 = 1.0

• Fat oxidation

1 palmitate + 23 O2 = 16 CO2 + 16 H2O

16/23 = 0.7

• Protein oxidation

1 amino acid + 5.1 O2 = 4.1 O2 + 2.8 H2O

4.1/5.1 = 0.8

• Lipogenesis > 1.0 – 8.0

Nutrient Utilization

• Regulation

– Nutrient availability

– Hormonal environment

– Inflammatory state



Energy Substrate Utilization

Fasting state:

o Depends on nutrient availability

In stress:

o Depends on hormonal environment and

inflammatory response

Body Composition

Weight (kg) 70 60 Weight (kg) 70 60

Total Water (L) 42 31 Fat (kg) 12.5 17

Intracellular 28 19 BCM

Extracellular 14 12 Protein (kg) 12.5 9

Total Solids (kg) 28 28.8 Minerals (kg) 3 3

MALNUTRITION

In malnutrition, energy expenditure must be calculated

based on actual body weight.

OBESITY

In obesity, energy expenditure must be calculated on ideal

weight.

Calculating Basal Energy Expenditure

Harris-Benedict Equation

o Variables

gender, weight (kg), height (cm),

age (years)

Men:

66.47 + (13.75 x weight) + (5 x height) – (6.76 x age)Women:

655.1 + (9.56 x weight) + (1.85 x height) – (4.67 x age)

Calorie requirement = BEE x activity factor x stress factor

Calorie Calculation

“Rule of Thumb”

Calorie requirement = 25 to 30 kcal/kg/day

METABOLIC RESPONSE TO STARVATION AND TRAUMA:

NUTRITIONAL REQUIREMENTS

Objectives

Explain the differences between metabolic

responses to starvation and trauma

Explain the effect of trauma on metabolic rate and

substrate utilization

Determine calorie and protein requirements during

metabolic stress

Metabolic Reaction to Starvation

Hormone Source Change in

Secretion

Norepinephrine Sympathetic Nervous

System

↓ ↓ ↓

Norepinephrine Adrenal Gland ↑

Epinephrine Adrenal Gland ↑

Thyroid Hormone

T4

Thyroid Gland

(changes to

T3 peripherally)

↓ ↓ ↓

Energy Expenditure in Starvation

Metabolic Response to Trauma

METABOLIC RESPONSE TO TRAUMA: EBB PHASE

Characterized by hypovolemic shock

Priority is to maintain life/homeostasis

o ↓ Cardiac output

o ↓Oxygen consumption

o ↓ Blood pressure

o ↓ Tissue perfusion

o ↓ Body temperature

o ↓ Metabolic rate

METABOLIC RESPONSE TO TRAUMA: FLOW PHASE

↑ Catecholamines ↑ Glucocorticoids

↑ Glucagon

Release of cytokines, lipid mediators

Acute phase protein production

Metabolic Response to Trauma



Severity of Trauma: Effects on Nitrogen

Losses and Metabolic Rate

Metabolic Response to Starvation and Trauma

Starvation Trauma or Disease

Metabolic rate ↓ ↑↑

Body fuels conserved wasted

Body protein conserved wasted

Urinary nitrogen ↓ ↑↑

Weight loss slow rapid

The body adapts to starvation, but not in the presence of

critical injury or disease.

Calorie Distribution Shift in Catabolism

Normal Catabolic

Fat 25% 30%Protein 15% 25%

Carbohydrate 60% 45%

Determining Calorie Requirements

Indirect calorimetry

Harris-Benedict x stress factor x activity factor

25-30 kcal/kg body weight/day

Metabolic Response to Starvation and Trauma: Nutritional

Requirements

Injury Stress Factor

Minor surgery 1.00 – 1.10Long bone fracture 1.15 – 1.30

Cancer 1.10 – 1.30

Peritonitis/sepsis 1 10 – 1 30

Severe infection/multiple trauma 1.20 – 1.40

Multi-organ failure syndrome 1.20 – 1.40

Burns 1.20 – 2.00

Activity Activity Factor

Confined to bed 1.2

Out of bed 1.3

Metabolic Response to Overfeeding

Hyperglycemia

Hypertriglyceridemia

Hypercapnia

Fatty liver

Hypophosphatemia, hypomagnesemia, hypokalemia

Macronutrients during Stress

CARBOHYDRATEAt least 100 g/day needed to prevent ketosis

Carbohydrate intake during stress should be

between 30%-40% of total calories

Glucose intake should not exceed 5 mg/kg/min

FAT

Provide 20%-35% of total calories

Maximum recommendation for intravenous lipid

infusion: 1.0 -1.5 g/kg/day

Monitor triglyceride level to ensure adequate lipid

clearance

PROTEIN

Requirements range from 1.2-2.0 g/kg/day during

stress

Comprise 20%-30% of total calories during stress

Determining Protein Requirements for Hospitalized Patients

Role of Glutamine in Metabolic Stress

Considered “conditionally essential” for critical

patients

Depleted after trauma

Provides fuel for the cells of the immune system and

GI tract

Helps maintain or restore intestinal mucosal

integrity

Role of Arginine in Metabolic Stress

• Provides substrates to immune system

• Increases nitrogen retention after metabolic stress

• Improves wound healing in animal models

• Stimulates secretion of growth hormone and is a

precursor for polyamines and nitric oxide

• Not appropriate for septic or inflammatory patients

Key Vitamins and Minerals

Vitamin A Wound healing and tissue

repair

Vitamin C Collagen synthesis, wound

healing

B Vitamins Metabolism, carbohydrate

utilization

Pyridoxine Essential for protein

synthesis

Zinc Wound healing, immune

function, protein synthesis

Vitamin E Antioxidant

Folic Acid, Iron, B12 Required for synthesis and

replacement of red blood

cells



Nutritional Assessment

Medical history

Physical examination

Biochemical markers

Anthropometric measures

Tools for Nutritional Evaluation

Malnutrition Screening Tool (MST)1

Malnutrition Universal Screening Tool (MUST)2

DETERMINE for screening and assessment3

Subjective Global Assessment (SGA)4

Patient-Generated SGA (PG-SGA)5

Mini Nutritional Assessment (MNA)6

Nutritional Risk Index (NRI)7

Subjective Global Assessment

NUTRITIONAL ASSESSMENT

BIOCHEMICAL MARKERSSerum albumin

Serum transferring

Serum prealbumin

Total lymphocyte count

Serum cholesterol

Nitrogen balance

ANTHROPOMETRIC MEASURES

Height, Weight, TSF, MAC

BMI NOMOGRAM

Underweight <18.5Normal 18.5 - 25

Overweight 25 - 30

Obese >30

NUTRITIONAL RISK ASSESMENT FORM

Evaluation of Weight Change

Time Significant Weight

Loss

Severe Weight

Loss

1 week 1% to 2% > 2%

1 month 5% >5%

3 months 7.5% 7.5%

6 months 10% 10%

* Values charted are for percent weight change:

Percent weight change = (usual weight - actual weight) x 100usual weight

Nutritional Requirements

Indirect Calorimetry

Harris-Benedict formula with Long modification

Short Method

Underweight: ABW x 25 - 30 kcal/kg

Overweight: IBW x 25 -30 kcal/kg

Protein Requirements

Non-Stressed - 0.8 gm/kg/day

Mildly Stressed - 1-1.2 gm/kg/day

Severely Stressed - 1.5-2 gm/kg/day

Protein should comprise approximately20% of the

total calories during stress

Non-Protein Calories

Carbohydrate

Fats

NPC combinations

o acute stress: 70% carbo 30% fato usual: 60% carbo 40% fat

o infections: 50% carbo 50% fat

o pulmonary: 40% carbo 60% fat

Vitamin and Mineral Requirements

Micronutrient, trace element, vitamin and mineral

requirements of metabolically stressed patients are

elevated above normal

Give vitamin and mineral requirements daily

Nutritional Interventions

Nutritional counselingOral supplementation

Enteral tube-feeding

Parenteral feeding

Enteral or Parenteral:

Selecting the Route of Delivery

“If the gut works, use it.”



The rationale for early EN

Use of the gut stimulates GALT & MALT resulting in

enhanced immune response

Early feeding can trigger gut immunity and thereby

improve outcomes

Delay or failure may promote a proinflammatory

state with disease severity & morbidity

Enteral Formulas: Categories

Polymeric formulaso Commercial

o Blenderized

Oligomeric formulas

Disease-specific formulas

Modular formulas (concentrated protein and

carbohydrate preparations)

Polymeric Formulas

Contain intact macronutrients and require digestion:

o Intact proteins

o Polysaccharides

o Disaccharideso Polyunsaturated fatty acids (PUFA)

o Medium-chain triglycerides (MCT)

o Vitamins and minerals

Oligomeric Formulas

Hydrolyzed macronutrients facilitate digestion and

absorption

Components Glucose polymers

Amino acids

– Glutamine

– Arginine

Peptides

Monosaccharides

Disaccharides

Polyunsaturated fatty acids

Medium-chain triglycerides

Vitamins and minerals

Also called “elemental,” “semi-elemental,”

“All in One” Parenteral Formulas

Optimal utilisation of calories

Minimizes metabolic complications

o reduced volume load

o reduced CO2 production

o avoidance of hyperglycaemia

o less fat synthesis

Permits peripheral administration

Access for Parenteral Nutrition

Central PN

Percutaneous

Subclavian / Jugular

Femoral

PIC line

Cutdown

Basilic vein

External jugular

Aseptic technique required at

all times

Peripheral PN

Any peripheral vein

Aseptic technique

required at all times

Best removed after 48 –

72 hrs

Take home message (1)

ROUTINE SCREENING

Assessment of risk for nutrition related

complications

High index of suspicion

Consider nature of illness and over-all condition of

patient in the context of a second insult

ACCURATE ASSESSMENT

Accurate calculation of calorie & protein

requirements

Strict monitoring of actual feed delivery is more

effective than overestimation of patient

requirements

Overfeeding may be more harmful than

underfeeding !

ROUTE OF DELIVERY

Early & preferential use of EN, combined with PN

whenever necessaryMONITORING IMPLEMENTATION

Pre-op: Monitor actual intake as an index of success

Post-op: Monitor clinical parameters

DOCUMENT THE ENTIRE PROCESS !

What is our measure of success?

Surgical nutrition will become an established routine

in patient care

Surgical nutrition will become systematic and

organized w/ multidisciplinary participation

Patient outcomes will improve

The objective proof will be DOCUMENTATION

-arvin 09-01-08

metabolism in surgery

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