بسم الله الرحمن الرحيم Community Medicine
Lec-7-
Learning objectives
At the end of this lecture student would be able to : 1-Determine the meaning of energy balance. 2-Enumerate causes of under nutrition & conditions need nutritional modification . 3-Outline the main determinants of total energy requirement . 4-Illustrate factors affecting & method of estimation of basal metabolic rate . 5-Discuss factors condition the response to inadequate nutrient intake . 6-Determine undesirable practices that affect nutritional health of hospitalized patients . 7-Mention lines of nutritional status assessment . To a level accepted to the accreditation standard of the College .
Nutritional Requirements
Energy balance : it means energy intake that maintains a steady body weight. To formulate a plan for nutritional management ,one must consider the nutritional requirements of the patient and the impact of disease on these requirements.A-Energy insufficiency is reflected by weight loss. B-Energy over abundance causes weight gain.
Conditions need modification in nutritional requirements :-
1.Infection. 2.Trauma. 3.Surgery. 4.Alcohol abuse. 5.Malabsorption.Estimation of energy requirement
1.Inadequate intake. 2.Inadequate absorption. 3.Increased metabolic requirements imposed by disease through: a.)Excessive loss of nutrients. b.)Drug - nutrient antagonism.Although malnutrition ,literally means abnormal nutrition (either excessive or inadequate energy balance ),in general the term refers to under nutrition. Causes of under nutrition could be :-
Total daily energy requirement consist of:- 1.Basal metabolic rate (BMR) also called Resting Metabolic Rate (RMR). It is a measure of the amount of energy expended at rest and without food .It accounts for about 2/3rd of total energy requirement. 2.Energy of activity It is a measure of the energy expended to support a variety of physical activities .It accounts for about 1/3rd of total energy expenditure and vary from 1.5 to 8.5 Kcal/Kg/hour.
3.Diet-induced thermo genesis (DIT)
It is also called thermal effect of food. Previously termed specific dynamic action.It is the increase in energy expenditure above basal values associated with consuming food.Two main types:- a.) Obligatory thermo genesis (digestion,transport and food processing).b.) Facultative thermo genesis (energy for weight maintenance and prevention of obesity).
Diet induced thermo genesis is the greatest for protein then for carbohydrates and least for fats. Resting Metabolic Rate (RMR) is affected by:- 1.Body size (height & weight). 2.Age. 3.Sex. 4.Habits.
Mixed diet cause 6-10% increase above basal values as heat.
Example:- A 45 years old ,70Kg male office worker presents with rheumatoid arthritis of mild severity. His caloric intake is good,but recent activity has been limited. Resting Energy Expenditure = 1800 Kcal Activity Related Expenditure = 400 Kcal Illness related expenditure (10% of REE) = 180 Kcal Diet Induced Thermo genesis (10% of 2380) = 238 Kcal
Total is 2618 Kcal
Harris and Benedict method for calculating BMR BMR woman =655+(9.5*W(Kg))+(1.8*H(Cm))-(4.7*A(Year)) BMR man = 660+(13.7*W(Kg))+(5*H(Cm))-(6.8*A(Years))
Note : The predicted basal metabolic rate may be over or under estimate the measured values by 20% or even 30% for any individual.
Estimation of additional energy expenditure by activity
Factors that condition the response to inadequate nutrient intake :A.)Nutritional Factors 1.Underlying adequacy of reserves /depot of that nutrient. 2.Severity of the inadequate intake & duration of deprivation. 3.Concurrent deficiencies of other nutrients .
1.Fever,infection,trauma and other conditions associated with increased requirements and catabolic processes. 2.Malabsorptive , mal-digestive states.
B.)Underlying illness
3.Illness associated with excessive loss of nutrients e.g. protein-losing enteropathy , nephritic syndrome & enteric fistulae. 4.Conditions associated with altered metabolism of nutrient e.g. Diabetes Mellitus & hyperthyroidism.
C.)Physiologic state
1.Pregnancy & lactation. 2.Growth and development during infancy, childhood and adolescence.Undesirable Practices that affect nutritional health of hospitalized patients:
1.Failure to record height & weight in hospital chart. 2.Diffusion of responsibility for patient care. 3.Prolonged use of intravenous feeding (glucose & saline). 4.Failure to observe and record patients dietary intake. 5.Withholding meals because of diagnostic tests.
6.Use of enteral or parentral feedings of uncertain composition and inadequate amounts. 7.Ignorance of the composition of nutritional products. 8.failure to recognize increased nutritional needs due to injury or illness.
9.Lack of communication and interaction between physician ,nurse and dietician.
10.Delay of nutritional support until the patient is in a state of sever depletion.
11.Limited availability of laboratory tests to assess nutritional status & failure to use those that are available.
12.Limited emphasis on nutrition education in medical schools.
Assessment of nutritional status There are five lines of investigations and assessment for nutritional status :-
I.Clinical way of investigation i.e. performing clinical examination for a sample of population such as school children ,factory workers , farmers.
This method can help in finding level of nutritional status of that community.Well nourished person is alert ,active ,have firm muscles , bright eyes and smooth elastic skin.Poorly fed person is inert , lethargic , flobby muscles and have rough skin. For such surveys , a clinical card which contain all important points has to be filled in for each individual.
II.Biochemical & Laboratory examinations
This method is used at the same time with the first method. e.g. Hemoglobin ,PCV, vitamins level in serum & intermediate metabolites of nutrients in certain dietary deficiencies.
III.Vital Statistics
Such as mortality rates e.g. Infant mortality rate , neonatal mortality rate ,still birth rate,….etc.All such rates can be used as indirect indices for general population nutritional status.During famine , crude death rate shows a considerable increase while infant mortality rate becomes higher in badly nourished communities .
IV.Study of Anthropometric Data
It includes:- 1.Weight for age method by using: a.Growth chart (percentile) It is a rapid method and sensitive to any deterioration in child health within few days.So it is valuable in diagnosing acute malnutrition. b.Standard Deviation Units (Z Scores). It is useful in comparing child weight ,age & sex with the median weight value , (-1SD,-2SD,-3SD) of the normalized reference weight for age for each sex by WHO tables.A child with length or height bellow (90%) of the reference population suggests a stunted child which occur in a chronically undernourished individual.
3.Weight for height method by using: a.Weight for height wall chart. It is used for acute malnutrition screening. b.Z Scores for weight and height (S.D.) -2SD means serious acute malnutrition. -3SD Means critical and severe malnutrition.
2.Length or height for age method
4.Mid -arm circumference method : usually about 16 mm in one year old child and 17mm in five years old child.
It is a good indicator for muscle growth , otherwise protein energy malnutrition can be diagnosed easily through this method .
5.Combination of weight /height & height /age methods
Thin child (wasted) low weight /height Normal height/ageIt means acute seriously ill child. Stunted child Normal weight /height Low height/ageIt means a chronic problem .Now healthy but short.
Thin and stunted Low height /age Low weight /heightIt means having both acute and chronic problems of malnutrition V.Dietary Surveys
It includes quantitative information about food intake of the community.Both food and physiologic tables are used here .Three main levels of dietary surveys are present : 1.National Survey . 2.Family Survey . 3.Individual Survey.