Principles in Critical Care Nutrition Kapil Zirpe, Subhal Dixit, Khalid Khatib, Anshu Joshi, Sadanand Kulkarni
INDEX
A
Acidosis 14
Acquired immune deficiency syndrome 224
Adrenocorticotropin releasing hormone 215
Aggravate inflammatory bowel disease 129
Airway 111
Albumin 127, 135, 284
Alcoholism 34
All-in-one
bags 48
system 47, 63
Aluminium hydroxide 35
Alzheimer's disease 213
American Diabetes Association 218, 219
American Society for Parenteral and Enteral Nutrition 51, 138, 221, 266
Amino acid 42, 54, 57, 63, 93, 94, 121, 133, 153, 203
aromatic 28
essential 57
Amyotrophic lateral sclerosis 216
Angiotensin converting enzyme 190
Anorexia 34
nervosa 224
Anthropometry 5, 136, 145
Antibiotics 175
Antioxidants 109, 113, 255, 257, 259
exogenous 256
Antiretroviral therapy 199
Aortoenteric fistula 167
Aortoesophageal fistulas 33
Appetite
loss of 97
stimulants 190
Arachidonic acid 263
Arginine 92, 170, 268, 270
Arrhythmias 59
Artificial nutrition 223, 250
support 14
Artificial tube feeding 190
Ascorbic acid 150
Aspiration 31, 33
risk of 87, 112
Azotemia 59, 125
B
Bariatric nutrition 187
Bariatric surgery 177, 178t, 187
Basal energy expenditure 135
Biochemical
complications 191, 228
monitoring 80
Biochemistry 5, 145
Bioenteric balloon insertion 180
Biotin 150
Bleeding 33, 228
Blenderized tube feeding 28
Blood
ammonia 59
glucose 64
control 115
Bloodstream infection
catheter related 45
central line-associated 68, 69
Body mass index 78, 100, 113, 145, 177, 195, 199, 223, 284
Bone markers 80
Bowel
anatomy of 169
movements 204
Brain injury, traumatic 112, 213
Branched chain amino acids 28, 57
Breathing 111
Burns 97, 211
pathophysiology of 118
C
Cachexia 34, 193, 194
Calcium 149, 150, 152, 174, 229
Calories 152
Cancer 34, 193, 194
development of 194
Candida albicans 65
Capric acid 263
Caprylic acid 263
Carbohydrates 54, 93, 121, 149, 152, 155, 173, 174, 189, 203, 207
requirements and glycemic control 121
Cardiac disease 157
Catalase 255
Catheter
misplacement of 231
thrombosis 231
Central insulin sensitivity 68
Central venous
access device, site of 45
catheter 67
lines, management of 69t
Chemoradiotherapy 234
Chemotaxis 70
Chinese Society of Clinical Oncology 236
Chloride 229
Cholestasis 231
Cholestyramine 175
Chronic obstructive pulmonary disease 157
Clinical nutrition, basics of 1
Clostridium difficile infections 32
Cobalamine 150
Collagenases 92
Complementary feeding 16
Computed tomography scan 195
Constipation 32, 228
Continuous renal replacement therapy 61, 276
Copper 95, 122, 155
Corticosteroids 127
Cortisol 11
Critical care nutrition 283
future of 289
Critical illness hyperglycemia, causes of 68
Crohn's disease 127, 128, 130, 173
Cyproheptadine 190
Cysteine 94
D
Daily estimated electrolyte requirements 229t
Daily nutrition requirements 147, 152
Dehydration 121, 228
Delayed bowel function recovery 134
Diabetes mellitus 27, 34, 94, 133, 218
Diarrhea 31, 101, 200, 228
drug induced 134
treatment of 175
Diet, components of 207
Dietary interventions, aims of 128
Disease specific
formulas 226
nutrition 209
Docosahexaenoic acid 65, 263, 266
Docosapentaenoic acid 263
Dronabinol 190
Drug nutrient interactions 216
Duodenal switch, laparoscopic 180
Dyselectrolytemia 228
Dysphagia 200, 213
E
Early enteral feeding, advantages of 123
Eicosapentaenoic acid 65, 113, 263, 264, 266
Electrolyte 42, 43, 161, 229
deficiency 60
disorders 49
disturbances 80, 101
imbalances 102
End stage liver disease 136t
Energy 6, 29, 93, 106, 107, 147, 152, 173, 188, 200, 229
and protein targets, calculation of 4, 6
intake 148, 150
requirement 155, 203, 206
calculation of 113
estimation of 120
supply 41
Enteral feeding 174
laboratory monitoring of 79
tubes, monitoring 78
Enteral formula 26, 201
Enteral nutrition 15, 25, 26, 31, 39, 51, 77, 128, 138, 163, 170, 190, 214, 219, 234, 158, 283
complications of 31, 31t
dosing of 114
metabolic complications of 36t
planning of 224
route of 225
support 19
use of 234
Enteral tube feeding 21
contraindications of 21
indications of 21
Enterocutaneous fistula 167
Enterostomy tube 228
feeding 225
Epistaxis 31, 32
Erosion 33
Esophageal ulceration 33
Esophagectomy 103
European Association for Palliative Care 236
European Society for Clinical Nutrition and Metabolism 265
European Society for Enteral and Parenteral Nutrition 3, 9, 51, 97, 138
European Society of Surgical Oncology 236
Excessive carbohydrates, adverse effects of 208
Extensive mesenteric ischemia 173
Extracorporeal membrane oxygenation 160
F
Fat 94, 121, 147, 152, 174, 188, 200, 203
malabsorption 134
requirements 122
Fatty acid 170
deficiency 65
essential 60
dietary 263t
monounsaturated 263
polyunsaturated 262264
saturated 263
Fatty liver 125
Feeding
complications of 100
initiation of 99
intolerance 216
solutions, choice of 26
Fiber 149
containing formulas 226
intake 152
Fibroblasts 85
Fistula, anatomy of 169
Fluid 14, 29, 207
balance 77
imbalance 102
intake 148
overload 85, 228
retention 59
Fluoroscopic gastrostomy 225
Folic acid 150, 152, 163
Food and Drug Administration 69
Fructo oligosaccharides 27
G
Gamma-linolenic acid 113
Gastric
banding, laparoscopic 180
distension 101
intolerance 108
residual volume 108, 116
role of 108
Gastrointestinal
complications 31
fistulae 167
function, evaluation of 26
malignancies 51, 224
tract, function of 112
Gastrostomy 21, 31, 78
percutaneous 214
surgical 225, 235
Ghrelin 11
G-linolenic acid 263
Glomerular filtration rate 146, 148, 202
Glucagon 11
Glucose 79
intolerance formulae 27
Glucosuria 121
Glutamine 54, 94, 170, 236, 266, 268
Glutathione 255
peroxidase 255
Gravity infusion 226
Growth hormone 135, 190
H
Harris-Benedict equation 162, 206
Healing, phases of 91
Heart failure, congestive 258
Hemodialysis 151
Hemostasis 92
Heparin 54
Hepatic
complications 71
encephalopathy 132, 138
failure 56, 102
formulae 28
steatosis 59, 231
HIV infection 199
Home artificial nutrition 235
Home enteral nutrition 26, 223
implementation of 226
Home nutritional support 171
Home parenteral nutrition 228
Hormones 11
Hospital malnutrition, preventing and treating 249
Hospital Nutrition Steering Committee 241
Hydration status 80
Hyperammonemia 170
Hypercapnia 59, 231
Hypercatabolic state 97, 134
Hypercatabolism 85
Hyperemesis gravidarum 209
Hyperglycemia 36, 49, 59, 68, 85, 100, 102, 125, 160, 170, 218, 219t, 222, 231
pharmacologic management of 221
post-traumatic 113
prevention of 220
Hyperinsulinemia 9, 59
Hyperkalemia 36
Hyperlipidemia 102
Hypermetabolism 85
Hypernatremia 36
Hyperphagic diet 175
Hyperphosphatemia 36, 149
Hypertonic saline 216
Hypertriglyceridemia 42
Hypoalbuminemia 168, 206
Hypocaloric feeding 106
degree of 6
Hypoglycemia 36
Hypokalemia 35, 36, 231
Hypomagnesemia 70
Hyponatremia 35, 36
Hypophosphatemia 35, 36, 231
Hypoxia 14
I
Immune
cells 85
dysfunction 59, 205
modulating formulae, role of 109
Immunonutrients 103, 161, 163, 170
Indirect calorimetry 120, 206, 207, 209
Infections 59, 88, 228
catheter related 231
Inflammation 9, 92
Inflammatory bowel disease 102, 126, 126t, 127129, 135, 224
Insulin 11, 54
therapy 35
Intensive care
subpopulation of 102
unit 3, 4, 9, 21, 51, 69, 157, 159, 275, 278
Intermittent bolus feeding 226
Intestinal fistula 228
Intrabronchial placement 227
Intraperitoneal supplements 153
Intravenous fat emulsions 63, 266
Iron 95, 147, 150
J
Jejuno-colonic anastomosis 176
Jejuno-ileocolonic anastomosis 176
Jejunostomy 31, 235
surgical 225
K
Kidney 144
disease 144, 146
function 80
injury 56
Krebs's cycle 14
L
Lactulose 28
Laryngospasm 33
Lauric acid 263
Lean body mass, loss of 205
Leptin 11
Linoleic acid 262, 263
conjugated 263
Lipid 42, 54, 106, 149, 207, 208
adverse effects of 209
emulsion 56, 65, 65t
Lipolysis 133
Liver
disease 132, 134t, 135, 138
failure 210
transplantation 132, 140t
Long chain triglycerides 60, 65
Loperamide 175
Lymphoid tissue 87
Lysine 94
M
Macronutrients 200
Magnesium 43, 80, 95, 115, 134, 152, 174, 229
Magnetic resonance imaging scan 61, 195
Malabsorption 133, 168
syndromes 34
Maldigestion 34
Malignancy 224
Malnutrition 9, 85, 132, 193, 233
assessment of 127
cancer related 193
causes of 10t, 126, 126t
chronic 34
consequences of 127
correction of 95
effects of 158
impact of 205
management of 189
pathophysiology of 9, 215
risk of 105
screening tool 234
universal screening tool 3
Manganese 95
Medium-chain triglycerides 57, 58, 140
Megestrol acetate 190
Metabolic bone disease 71, 231
Metalloproteinases 92
Methionine 94
Micronutrient 109, 155, 174, 200, 259
deficiency 35, 134t
correction of 130
requirements 122, 204
role of 109
Mid-arm muscle circumference 145, 284
Minerals 29, 94, 149, 150, 189
Mini-nutritional assessment 105, 234
scale 189
Motor neurone diseases 213
Multi-chamber bags 48, 63, 64
Multi-lumen central venous catheters 230
Multiple bottle system 47
Multiple organ dysfunction syndrome 162, 255
Myocardial infarction, acute 157
Myristic acid 263
N
N-3 fatty acids 264266
Nasoduodenal tubes 24
Nasoenteral feeding tubes 31, 225
Nasogastric tube 31, 174, 200, 235
Nasojejunal tube 24, 235
Nausea 32, 228
Needle catheter jejunostomy 21
Nervous system 135
Neuroinflammation 112
Neuromuscular dysfunction 59
Niacin 150, 152, 200
Nicotinic acid 150
Nitrogen balance 209
N-methyl-d-aspartate 115
Non-essential amino acids 57
Non-ketotic coma 170
Non-nasogastric feeding 115
Non-protein energy 57
Nonsteroidal anti-inflammatory drugs 67
Normalized protein nitrogen appearance 145
Nucleic acid 266
Nucleosides 170
Nucleotides 170
NUTRIC score 22, 52, 52t, 120, 159t
Nutrients 14, 150
absorption 179
deficiency of 60
in wound healing 93
requirement of 173
requirements 154
Nutrition 5, 103
assessment 4
stage of 4
care process, course of 77
delivery
methods of 200
principles of 200
formula 49
goals of 205
in chronic
hemodialysis 150
kidney disease 146
in motor neuron diseases 216
in peritoneal dialysis 152
in stroke 213
in traumatic brain injury 214
intervention, monitoring of 77
monitoring of 101
provision of 3
risk score 3, 4, 159
route of 124, 128, 164
screening 3, 4, 242
status assessment 113
support 118
in nonsurgical oncology 233
route of 107, 114
team 195, 248
therapy 51, 113, 116
evaluation of 250
monitoring of 250
Nutritional
absorption 134
assessment 3, 52, 119, 233
goals of 205
care, future of 288
deficiencies 183, 183t, 228
interventions 140, 151, 169
management, rationale of 169
monitoring 77
requirements 228
assessment of 159, 284
calculation of 98
estimation of 106, 188
monitoring of 284
screening and assessment 86
status 10, 11t
assessment of 97, 135, 136t, 158, 189
monitoring 205
optimization of 168
supplementation 129
support 78, 144, 160
during cancer surgery 197
in acute pancreatitis 162
in AIDS 199
in bariatric surgery 177
in burns 118
in cancer 193
in cardiac disease 157
in chronic pancreatitis 162
in extensive gut resection 173
in gastrointestinal fistulas 167
in kidney transplant recipients 153
in liver disease 132
in liver transplant 132
in neurological disorders 213
in pregnancy 202
in pulmonary disease 157
in renal disease 144
in sepsis 105
in trauma 111
in wound healing 91
modes of 19, 37
monitoring of 75, 77, 125
team 232, 248, 249
timing of 123
therapy 137, 174, 175
in liver transplant 138
Nutritious foods 9
O
Obesity 102, 210
Oleic acid 263
Omega-3 fatty acids 262, 265, 268
Oral nutritional
supplements 15, 86, 108, 190, 200, 234, 265
support 219
Organ function, derangement of 97
Overfeeding 124
complications of 125t
Oxygen consumption 85
P
Pain, abdominal 101
Palmitic acid 263
Palmitoleic acid 263
Pancreas 162
Pancreatitis 102, 162, 210
Pantothenic acid 95, 150, 152
Parathyroid hormone 231
Parenteral fluid balance 77
Parenteral micronutrients 275, 278
Parenteral nutrition 37, 39, 40, 47, 54, 59, 60, 60t, 67, 77, 80, 101, 111, 128, 163, 170, 191, 195, 196, 200, 220, 221, 230, 258, 277
administering 41
central 44
complications of 58, 59t, 67, 124t
components of 56t
compounding 63
contraindications of 39
formulae 63
implementation of 230
indications of 39, 235
planning of 51
preparation of 230
solutions 65
use of 235
Parkinson's disease 213
People living with HIV 199, 201
Percutaneous endoscopic gastrostomy 190, 216, 225
Perioperative nutritional
components of 86t
interventions 86
support 85
Perioperative parenteral nutrition 86, 88
Peripheral parenteral nutrition 15, 44
Peripheral veins 44, 49
Peripherally inserted central catheter 230, 235
Phagocytosis 70
Pharmaconutrients 161
Phosphate 42, 229
Phosphorus 79, 149, 150, 152
Pneumonia 111
Pneumothorax 227
Polymeric formulae 27
Polytrauma 97
Polyuria 121
Post bariatric surgery 182t
Post pyloric tube 24, 31, 225
Post-liver transplantation period 140
Postoperative nutritional supplementation 181
Postpyloric feeding 108
Potassium 43, 49, 79, 80, 149, 150, 152, 229
Pre-albumin 135, 189
micronutrients 284
Pre-liver transplantation period 140
Preoperative carbohydrate loading 86, 87
Preoperative metabolic optimization 86, 87
Prokinetics 109
administration of 101
Proline 94
Prostaglandins 264
Protein 6, 93, 106, 107, 147, 152, 153, 173, 188, 200, 204, 207, 208
adverse effects of 208
energy malnutrition 132
diagnosis of 132
intake 148, 151
dietary 145
requirement 121, 155, 229
restriction 148
Proton pump inhibitors 175
Pump controlled techniques 226
Pyridoxine 152
hydrochloride 150
R
Radiation enteritis 224
Radiotherapy 237
Randomized controlled trials 21
Reactive oxygen species 255
Recommended daily allowance 93, 257
Refeeding syndrome 5, 12, 14, 34, 34t, 70, 228
risk of 80, 119
Renal disease 144
Renal failure 101, 210
Renal replacement therapy 56, 144
Respiratory distress syndrome, acute 157, 266
Respiratory failure 157, 101, 210
Retinol 134, 150
Riboflavin 95, 150, 152, 204
Ribonucleic acid 258
Roux-en-y gastric bypass 179
laparoscopic 180
S
Selenium 109, 122, 134, 150, 155, 256, 257
supplementation 256
Sensory stimuli 116
Sepsis 80, 102, 211
acute phase of 106, 107
control 168
shock, severe 105, 108, 109
Septic
complications 54
shock, severe 105, 108, 109
Sequential organ failure assessment 52, 159
Serum
albumin 145, 189
lactate 14
levels 79
potassium 49
Short bowel syndrome 16, 173, 224, 228
Short nutritional assessment questionnaire 159
Simple starvation 9
Single bottle system 47
Sinusitis 31, 32
Skin 167
fold thickness 145
Sleeve gastrectomy, laparoscopic 180
Small intestinal bacterial overgrowth, risk of 130
Society of Critical Care Medicine 28, 221, 266
Sodium 80, 85, 147, 149, 150, 152, 229
levels of 70
Standard parenteral nutrition 47
Standard polymeric formulas 225
Staphylococcus aureus 64
Starvation, pathophysiology of 9
Stearic acid 263
Stearidonic acid 262, 263
Steatosis 102
Stress starvation malnutrition 9
Stroke 213
Sucralfate 35
Superoxide dismutase 255
Supplemental enteral nutrition 129
Surgery 265
Surgical intensive care unit 266
Swallowing, assessment of 116
Systemic inflammatory response syndrome 162, 255
T
Teduglutide 175
Theophylline 35
Thiamine 95, 109, 152, 163, 204
deficiency 70
hydrochloride 150
Thioredoxin 255
Three-chamber bags 48
Thrombophlebitis 44
Thyroid 11
stimulating hormone 11
Tiger tube 225
Total parenteral nutrition 15, 258
Total protein 284
Trace elements 42, 54, 61t, 115, 150, 151, 155, 230
deficiency 60, 168
requirements 122t
Tracheoesophageal fistula 227
Trans-fatty acids 263
Transitional feeding 227
Transnasal access 21
Transthyretin 189
Trauma 211
index 78
Triceps skinfold thickness 284
Tube
blockage 227
clogging 31, 34
displacement 31
malposition 31, 33
Tumor 94
necrosis factor 111, 195
Tunneled central venous catheter 230
Two-chamber bags 48
U
Ulceration 33
V
Vaccenic acid 263
Venous access devices 45
Visceral protein 284
Vision 249
Vitamin 19, 42, 54, 56, 94, 109, 149, 150, 151, 155, 168, 169, 230
A 94, 95, 122, 152, 155, 174, 204, 256258
B complex 155
B1 79
C 94, 95, 109, 122, 152, 155, 189, 204, 256, 258, 259
D 109, 134, 147, 152, 174, 189, 204
requirement 230
E 95, 122, 152, 174, 256, 258, 259
supplementation 259
K 134, 150, 152, 174
requirements 122t, 204
role of 109
Vocal cord dysfunction 33
Vomiting 32, 101, 228
W
Weak respiratory muscles 205
Weight loss, causes of 194
Wound
acute 91
care 169
chronic 91, 92
healing 91, 94, 94t, 95t
surgical 91
types of 91
Z
Zinc 95, 109, 115, 122, 134, 150, 152, 155, 256, 257
deficiencies 163
supplementation 258
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Chapter Notes

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1Basics of Clinical Nutrition
SECTION OUTLINE
  1. Nutritional Assessment and Techniques Used in Nutritional Assessment
  2. Pathophysiology of Malnutrition, Starvation, Metabolic Derangements in Diseased (Simple Starvation, Stress Starvation Malnutrition and the Response to Injury)
  3. Need of Artificial Nutrition Support (Common Indications of Nutritional Support According to Healthcare Setting and Disease)2

Nutritional Assessment and Techniques Used in Nutritional AssessmentCHAPTER 1

Daniella Bear
 
INTRODUCTION
The provision of nutrition support to the critically ill patient is a fundamental aspect of their care. Although the optimal strategy has not yet been agreed, undertaking a thorough nutrition assessment can greatly assist the clinician to make the safest and the most appropriate choice regarding the route, timing, and amount of nutrition support. Whilst most intensive care units (ICU) will have a feeding protocol in place to allow enteral feeding to commence as soon as hemodynamic stability has been achieved, it is now generally accepted that patients who are expected to stay for more than 72 hours undergo a full nutrition assessment to allow individualization of their nutrition prescription.1
An initial nutrition assessment consists of three elements:
  1. Nutrition screening to determine nutrition risk
  2. Nutrition assessment to determine the nutrition status of the patient
  3. Calculation of energy and protein targets
Following this, it is recommended that the patients are monitored frequently and adjustments made to their nutrition prescription accordingly. This chapter will outline the steps and techniques involved in undertaking a nutrition assessment of the critically ill patient.
 
NUTRITION SCREENING
Nutrition screening aims to identify those patients who may benefit the most from nutrition support, a concept defined as nutrition risk.2 This is an important consideration given many patients in the ICU will have short admissions. And therefore provision of scant resources in the healthcare setting, such as specialist staffing, can be directed where they may be most useful.
There are several tools available for use in the ICU, each with their own limitations. The Malnutrition Universal Screening Tool (MUST) is a five-step screening tool that requires knowledge of the patient's weight, height, and any history of weight loss. These are all factors that are difficult to obtain in the fluid overloaded, sedated ICU patient. In addition, obese patients score low on MUST which may not reflect their true nutrition risk in the ICU setting whereby, these patients are frequently underfed and may have higher protein needs than adequately nourished patients.
The Nutrition Risk Score (NRS) 2002 is recommended by both The European Society for Parenteral and Enteral Nutrition (ESPEN)3 and the American Society for Parenteral and 4Enteral Nutrition (ASPEN).1 NRS 2002 is a two-part screening tool that includes severity of illness as a variable, but is likely not sensitive enough for most critically ill patients as an APACHE II score more than 10 automatically classifies the patient as high risk. Similar to the MUST, it also requires height, weight, and previous dietary history making this a difficult tool to use in the ICU setting.
Finally, the Nutrition Risk in the Critically ill (NUTRIC) Score has been proposed as a more desirable screening tool in critical illness2, 4 and is also recommended by ASPEN.1 NUTRIC includes variables such as severity of illness and organ failure, body mass index (BMI), age, and length of stay in hospital prior to ICU admission. Whilst it does not include any nutrition specific variables, the last point is intended as a surrogate for malnutrition. NUTRIC has not yet been prospectively validated in the critically ill and its main limitation is the time taken to calculate the severity of illness and organ failure scores at the bedside making it a tool most likely to be used in the research setting at present.
As there is currently no ideal nutrition screening tool to determine the nutrition risk of critically ill patients, it is important to consider all variables included in current screening tools as well as additional factors which may influence the nutritional risk of the patient such as muscle mass, projected length of stay on the ICU and the specific injury or illness which may influence nutritional status (e.g., trauma or burns). Considering each of these factors together can help make an informed judgment of the nutrition risk of individual patients.
Whichever is chosen, a screening tool or clinical judgment, it is recommended that nutrition screening should be undertaken within 48 hours of admission to the ICU (Table 1).
 
NUTRITION ASSESSMENT
Following nutrition screening, a full nutrition assessment should be undertaken by a suitably qualified individual in those patients considered to be a high nutrition risk.
Table 1   Considerations and suggested frequency for each element of the nutrition assessment.
Stage of nutrition assessment
Considerations
Frequency
Nutrition screening
Appropriate screening tool for patient case mix (e.g., NRS 2002 or NUTRIC), or consider variables separately to form judgment of nutrition risk
Within 48 hours of admission to the ICU
Nutrition assessment
Consider anthropometry, biochemistry, clinical and dietary variables
Initial assessment within 48–72 hours of admission and then a minimum of weekly thereafter or when clinical condition changes
Calculation of energy and protein targets
Consider the most appropriate equation in the absence of indirect calorimetry
Individualized calculation within 48–72 hours of admission to the ICU and then a minimum of weekly thereafter or when clinical condition changes
(ICU, intensive care unit; NRS, Nutrition Risk Score; NUTRIC, Nutrition Risk in the Critically Ill.)
5However, it should be noted that a patient's nutritional status and hence nutrition risk may change over the course of their admission and therefore it is imperative that all patients are monitored frequently and care plans adapted accordingly. A low nutrition risk patient on admission is not necessarily a low risk patient for the entirety of their admission. In addition, patients staying in the ICU for more than 7 days should undergo a full nutrition assessment.
A nutrition assessment should consider each of the following aspects. These should be considered on initial nutrition assessment and when monitoring the patient and the nutrition care plan should be formulated and adapted accordingly (Table 1).
 
Anthropometry
Ideally, an accurate weight and height would contribute to a thorough nutrition assessment. However, due to the clinical condition of the patient, this is often not possible or may be highly inaccurate due to large fluid shifts. However, it may be possible to obtain a recent weight and height from medical notes or family members and attempts should be made to do this.
Muscle mass may be an important predictor of outcome and potentially the response to nutrition support.5,6 At present, tools to assess muscle mass at the bedside, such as muscle ultrasound or computed tomography, are reserved for the research setting only. However, utilizing techniques such as the Subjective Global Assessment (SGA) which include a visual assessment of muscle wasting, has been shown to predict outcome in ICU patients and should therefore be considered.7
 
Biochemistry
Biochemical indices should be utilized with caution in the presence of inflammation during critical illness. Measures such as albumin are unreliable indicators of nutritional status and those that may be more reliable, such as pre-albumin, are not routinely measured.
A review of the patient's electrolyte status should be undertaken during a nutrition assessment as this can give clues as to the patient's nutritional status and response to nutrition therapy (e.g., refeeding syndrome). Although, like other biochemical indices, should be interpreted in the context of clinical condition as several factors, unrelated to the provision of nutrition support, may alter electrolyte status. Fluctuations in blood sugar levels should also be noted and monitored.
 
Clinical
The patient's clinical status and admission reason can provide valuable information during a nutrition assessment. For example, patients admitted with burns or trauma can experience a significant and rapid decline in their nutritional status. Factors such as temperature, rehabilitation, and certain medications (e.g., sedation) can provide details regarding fluctuations in energy expenditure or the need to adjust the nutrition prescription. It is also imperative to evaluate and monitor any extended periods of fasting and gastrointestinal intolerance as this may require alterations to the nutrition plan.
 
Nutritional
Previous nutrition intake should be considered where this information can be obtained from either recent medical notes or family members, however, inaccuracies associated with this 6should be noted. The cumulative energy and protein balance should be calculated at least twice per week during ICU admission, but ideally daily if this can be done via an electronic medical notes system. The aim should be to meet more than 80% of the prescribed target, otherwise plans should be put in place to achieve this. Non-nutritive energy sources such as propofol, citrate, and intravenous glucose should be included in this calculation as failure to do so may lead to overfeeding.
 
CALCULATION OF ENERGY AND PROTEIN TARGETS
The final step in a thorough nutrition assessment is to determine the individual energy and protein targets for the patient so that the most appropriate feeding regimen can be put in place. Optimal energy and protein targets are not yet known for critically ill patients, although guidelines are recommended adjusting energy targets according to the phase of critical illness. This is difficult given the lack of consensus on how to define the different phases. For this reason, energy and protein targets should be individualized and revised over the course of admission both when clinical condition changes and when the patient is discharged to the ward.
 
Energy
Studies investigating full feeding versus trophic or hypocaloric feeding over the first week of critical illness have not shown a benefit in terms of mortality or length of stay.8, 9 Despite this, some degree of hypocaloric feeding is currently advocated over the first week of ICU admission to reduce the risk of overfeeding that may be associated with the endogenous production of glucose. The currently accepted definition for hypocaloric feeding is 70% of measured energy expenditure or 80% using a predictive equation. Again, this is in relation to a reduction in mortality only, the effect of this feeding strategy on muscle wasting and recovery is not known.
The gold standard for determining energy targets is indirect calorimetry, although its use is not widespread due to the associated cost, labor, and exclusions. For this reason, predictive equations are most often used. There are several equations available for use in critically ill patients (Table 2), all with their limitations. Whichever equation is chosen, it is important to use the equation in exactly the way it was validated to obtain the most accurate result. This includes checking whether actual, ideal, or adjusted weight was used and the patient population in which the equation was derived (e. g., trauma).
 
Protein
Protein targets have been recently revised and are now higher than previous recommendations. There is a lack of robust evidence to support the higher targets and clinical judgement should be utilized in this case. A minimum of 1.2 g/kg/day is recommended with higher targets for specific patient groups (Table 3).7
Table 2   Common equations for use in critical care and considerations for their use.
Equation
Formula
Considerations for use
Harris–Benedict
Males: (13.7516 x W) + (5.003 x H) – (6.755 x A)
Females: 655.0955 + (9.5634 x W) + (1.8496 x H) – (4.6756 x A)
  • Developed in a non-clinical population
  • Sometimes used with the addition of a stress factor which can be subjective
Ireton–Jones (1992)
(5 x W) – (10 x A) + (281 x sex) + (292 x trauma) + (851 x burn) + 1925
  • Developed for trauma and burns patients only
Ireton–Jones (1997)
(5 x W) – (11 x A) + (244 x sex) + (239 x trauma) + (840 x burn) + 1784.
Penn State (1998)
(Harris–Benedict x 1.1) + (Tmax x 140) + (VE x 32) – 5340
Uses actual body weight in non-obese and adjusted bodyweight (25%) in obese
  • Use clinical variables which may reflect the fluctuations in energy expenditure
  • Requires a decision for which edition to use in which patient group as some versions particularly inaccurate in different populations (e. g., elderly and extremes of bodyweight)
Penn State (2003)
(Harris–Benedict x 0.85) + (Tmax x 175) + (VE x 33) – 6344
Penn State (m)
(Mifflin-St Jeor x 0.96) + (Tmax x 167) + (Ve x 31) – 6212
ACCP
25 kcal x kg
  • Unclear which weight to use which may lead to overfeeding in obese patients
  • Static equation which is difficult to re-assess when no weight is available for the patient
Mifflin-St Jeor
Males: (10 x W) + (6.25 x H) –(5 x A) + 5
Females: (10 x W) + (6.25 x H) – (5 x A) - 161
  • Required for various editions of the Penn State equation
(W = weight in kg; H = height in cm; A = Age in years; For sex, 1 is male, 0 is female; trauma present = 1 no trauma = 0; burns present = 1, no burns = 0; Tmax = maximum body temperature last 24 hours; VE = minute ventilation in L/min at time of measurement; Kcal = calorie; ACCP = American College of Chest Physicians).
Table 3   Recommended protein targets in critical illness.
Patient group
Protein target
General ICU
1.2–1.5 g/kg
Continuous renal replacement therapy
1.5–1.7 g/kg
Burns
1.5–2.0 g/kg
Trauma
1.3–1.5 g/kg
Obese
2.0–2.5 g/kg*
(ICU, Intensive care unit)
*Ideal body weight.
8
 
CONCLUSION
Nutrition screening to determine nutrition risk followed by a thorough nutrition assessment is recommended within 48 hours of admission to the ICU. Patients should be monitored frequently throughout their ICU admission and feeding regimens adjusted accordingly. Assessment and monitoring should not only include factors directly associated with nutritional status, biochemical and clinical factors that may provide information as to the patient's nutritional status or tolerance of their feeding regimen.
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