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Nutrition in Surgery
Dr. Liang Low
MMC
28.06.2003
Introduction
? Basic physiology
? Assessment of patients who are malnourished
? Methods of nutritional support: enteral vs parenteral
? Supplementation with key nutrients
Introduction:
? Malnutrition occurs in approx.40% of hospitalised patients
? Can lead to increased post-operative morbidity and mortality
* Impairment of skeletal, cardiac, respiratory muscle function
* Impairment of immune function
* Atrophy of GIT
* Impaired healing
Introduction:
? 3 basic questions to be answered:
* Can we identify which patients will benefit from nutritional support?
* When, and how long should the support be given?
* By what route should support be given?
Patho-physiology
? Proteins and amino acids
* Require daily intake 0.8 g kg-1 ie. 56 g for a 70 kg person
* Essential: a.a only obtained by dietary source
* Non-essential: can be endogenously synthesised
* 'conditionally essential': a.a unable to be synthesised under certain conditions eg. Stress, surgery
* L-alanine, L-glutamate, L-asparate
Patho-physiology
? Fatty acids
* Short, medium chain FA directly enter portal system
* Long chain FA transported as triglycerides
* Essential FA unable to be synthesised ie. Linoleic and linolenic acid.
* Deficiency causes skin, kidney disorders
Patho-physiology
? Energy requirements:
* Total daily expenditure - 25-30 kcal kg-1
* Resting metabolic rate
* Activity energy expenditure
* Diet induced energy expenditure
? Sources:
* Fats9 kcal g-1
* Protein4 kcal g-1
* Carbohydrates4 kcal g-1
* Alcohol 7 kcal g-1
Patho-physiology
? Energy requirements:
* Respiratory quotient (RQ) estimates utilisation of energy sources
* RQ = VCO2/VO2(litres per unit time)
* RQ = 1, utilising CHO
* RQ = 0.7, utilising fat
* Ideally 0.8, indicating mixed substrate utilisation
Patho-physiology
? Energy requirements:
* BMR calculated by Harris-Benedict equation
* 66.47 + [13.75 x W] + [5 xH] - [6.76xA]
* Additional caloric needs calculated by an injury factor,eg.
* Minor operation 1.2 x BMR
* Trauma1.3 x BMR
* Sepsis 1.6 x BMR
* Burns2.1 x BMR
Patho-physiology
? Vitamins
* Key metabolic roles
* Fat soluable (A, D, E, K) or water soluable
Patho-physiology
* Trace elements
* Zinc - wound healing, protein and nucleic acid synthesis
* Fe - energy transfer
* Copper - collagen synthesis
* Selenium - anti-oxidant enzyme system
Patho-physiology
* Changes in trauma and sepsis
* Catabolic phase
* Increase resting energy expenditure
* Loss of body nitrogen, muscle breakdown
* Increase glucose production (glycogenolysis), deplete liver stores
* Increase lipolysis
* Early anabolic phase
* Late anabolic phase
Nutritional assessment
? Identify those patients who are malnourished or at risk for malnutrition
* Recent weight loss > 10 - 15%
* Those expecting near or complete starvation for > 5 days
* Anticipation of a long recovery, prolonged time to return to oral intake
Nutritional Assessment
? History and examination
? Anthropometric measures
* > 10 % loss of 'well' body weight
* Body mass index : weight (kg)/ height 2 (m2)
* <18 kg/m2 assoc. With prolonged ICU, increased post-operative complications, higher readmission rates
* Mid-arm circumference, skin fold thickness
* Poor accuracy, specificity, reproducibility
Nutritional assessment
? Serum proteins
* Albumin
* Reflects synthesis, degradation, losses, exchange between intracellular and extracellular compartments
* Half life 21 days - limited ability to reflect acute changes
* < 3.5 g/dL assoc. increased morbidity
Nutritional assessment
? Serum proteins
* Tranferrin (1/2 life 7 days), Pre-albumin (1/2 life 2 days)
* More accurately reflect acute changes
* Limited by erratic responses to stress, sepsis, cancer
Nutritional assessment
? Nitrogen balance
= N intake - N loss
= (dietary protein x 0.16) - (urea nitrogen (urine) + 4 g (stool/skin) )
* Positive balance indicates anabolic state
* Negative balance indicates catabolic state
* Aim to provide non-protein sources of fuel to allow protein to be used for anabolic processes
Nutritional assessment
? Body composition
? Bioelectrical impedance
* Electrical current passed through water and electrolyte compartments of lean tissue
* Change in voltage estimates total body resistance (lean body mass)
? Immunocompetence
* Decreased skin reactivity to tuberculin
Nutritional assessment
? Functional capacity and muscle power
* Hand grip strength
Nutritional assessment
? Subjective global assessment (SGA)
* Clinical assessment by Abassi
* Weight loss over past 6 months, characterised as severe (>10%), moderate (5-10%), mild (<5%)
* Dietary intake, incl calories and nutrients
* Gastrointestinal symptoms ie. Impaired eating
* Functional capacity: bedridden, less active, fully active
* Physical signs- fat loss in triceps, muscle wasting in temporalis, deltoids, quadriceps
Nutritional assessment
? Carney and Meguid
Arch surg 137, Jan 2002
'tests of functional capacity, hand grip strength, total body nitrogen, bioelectrical impedence, dual x-ray absorptiometry are impractical.....simple and effective strategy is SGA combined with a few easily attainable objective parameters such as albumin and BMI'
Indications for nutritional support
? No strict criteria
? Consideration of pre-operative support
* Serum albumin < 30-32 gL-1
* Weight loss of>15 %......（后略) ......
Nutrition in Surgery
Dr. Liang Low
MMC
28.06.2003
Introduction
? Basic physiology
? Assessment of patients who are malnourished
? Methods of nutritional support: enteral vs parenteral
? Supplementation with key nutrients
Introduction:
? Malnutrition occurs in approx.40% of hospitalised patients
? Can lead to increased post-operative morbidity and mortality
* Impairment of skeletal, cardiac, respiratory muscle function
* Impairment of immune function
* Atrophy of GIT
* Impaired healing
Introduction:
? 3 basic questions to be answered:
* Can we identify which patients will benefit from nutritional support?
* When, and how long should the support be given?
* By what route should support be given?
Patho-physiology
? Proteins and amino acids
* Require daily intake 0.8 g kg-1 ie. 56 g for a 70 kg person
* Essential: a.a only obtained by dietary source
* Non-essential: can be endogenously synthesised
* 'conditionally essential': a.a unable to be synthesised under certain conditions eg. Stress, surgery
* L-alanine, L-glutamate, L-asparate
Patho-physiology
? Fatty acids
* Short, medium chain FA directly enter portal system
* Long chain FA transported as triglycerides
* Essential FA unable to be synthesised ie. Linoleic and linolenic acid.
* Deficiency causes skin, kidney disorders
Patho-physiology
? Energy requirements:
* Total daily expenditure - 25-30 kcal kg-1
* Resting metabolic rate
* Activity energy expenditure
* Diet induced energy expenditure
? Sources:
* Fats9 kcal g-1
* Protein4 kcal g-1
* Carbohydrates4 kcal g-1
* Alcohol 7 kcal g-1
Patho-physiology
? Energy requirements:
* Respiratory quotient (RQ) estimates utilisation of energy sources
* RQ = VCO2/VO2(litres per unit time)
* RQ = 1, utilising CHO
* RQ = 0.7, utilising fat
* Ideally 0.8, indicating mixed substrate utilisation
Patho-physiology
? Energy requirements:
* BMR calculated by Harris-Benedict equation
* 66.47 + [13.75 x W] + [5 xH] - [6.76xA]
* Additional caloric needs calculated by an injury factor,eg.
* Minor operation 1.2 x BMR
* Trauma1.3 x BMR
* Sepsis 1.6 x BMR
* Burns2.1 x BMR
Patho-physiology
? Vitamins
* Key metabolic roles
* Fat soluable (A, D, E, K) or water soluable
Patho-physiology
* Trace elements
* Zinc - wound healing, protein and nucleic acid synthesis
* Fe - energy transfer
* Copper - collagen synthesis
* Selenium - anti-oxidant enzyme system
Patho-physiology
* Changes in trauma and sepsis
* Catabolic phase
* Increase resting energy expenditure
* Loss of body nitrogen, muscle breakdown
* Increase glucose production (glycogenolysis), deplete liver stores
* Increase lipolysis
* Early anabolic phase
* Late anabolic phase
Nutritional assessment
? Identify those patients who are malnourished or at risk for malnutrition
* Recent weight loss > 10 - 15%
* Those expecting near or complete starvation for > 5 days
* Anticipation of a long recovery, prolonged time to return to oral intake
Nutritional Assessment
? History and examination
? Anthropometric measures
* > 10 % loss of 'well' body weight
* Body mass index : weight (kg)/ height 2 (m2)
* <18 kg/m2 assoc. With prolonged ICU, increased post-operative complications, higher readmission rates
* Mid-arm circumference, skin fold thickness
* Poor accuracy, specificity, reproducibility
Nutritional assessment
? Serum proteins
* Albumin
* Reflects synthesis, degradation, losses, exchange between intracellular and extracellular compartments
* Half life 21 days - limited ability to reflect acute changes
* < 3.5 g/dL assoc. increased morbidity
Nutritional assessment
? Serum proteins
* Tranferrin (1/2 life 7 days), Pre-albumin (1/2 life 2 days)
* More accurately reflect acute changes
* Limited by erratic responses to stress, sepsis, cancer
Nutritional assessment
? Nitrogen balance
= N intake - N loss
= (dietary protein x 0.16) - (urea nitrogen (urine) + 4 g (stool/skin) )
* Positive balance indicates anabolic state
* Negative balance indicates catabolic state
* Aim to provide non-protein sources of fuel to allow protein to be used for anabolic processes
Nutritional assessment
? Body composition
? Bioelectrical impedance
* Electrical current passed through water and electrolyte compartments of lean tissue
* Change in voltage estimates total body resistance (lean body mass)
? Immunocompetence
* Decreased skin reactivity to tuberculin
Nutritional assessment
? Functional capacity and muscle power
* Hand grip strength
Nutritional assessment
? Subjective global assessment (SGA)
* Clinical assessment by Abassi
* Weight loss over past 6 months, characterised as severe (>10%), moderate (5-10%), mild (<5%)
* Dietary intake, incl calories and nutrients
* Gastrointestinal symptoms ie. Impaired eating
* Functional capacity: bedridden, less active, fully active
* Physical signs- fat loss in triceps, muscle wasting in temporalis, deltoids, quadriceps
Nutritional assessment
? Carney and Meguid
Arch surg 137, Jan 2002
'tests of functional capacity, hand grip strength, total body nitrogen, bioelectrical impedence, dual x-ray absorptiometry are impractical.....simple and effective strategy is SGA combined with a few easily attainable objective parameters such as albumin and BMI'
Indications for nutritional support
? No strict criteria
? Consideration of pre-operative support
* Serum albumin < 30-32 gL-1
* Weight loss of>15 %......（后略) ......
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