Clinical Biochem 2 Flashcards
Insulin and Na
Insulin increases Na reabsorption in kidney eg obesity/ NIDDM, HPT
During starvation kr low car diets sodium excretion, >urination
Potassium
Normal range 3.5-5mmol/L
Intracellular
Acid base balance
Glucose metabolism (k stimulates insulin release)
Renal function
Neuromuscular endocrine disorders
Levels maintained via kidneys- aldosterone >excretion
Causes of high/ low serum K
High (hyperkalaemia)
Renal failure: impaired excretion
Metabolic acidosis: K moves out of cells, including renal tubular cells resulting in decreased excretion of K
Diabetic ketoacidosis, insulin deficiency
>dietary K, supplemented (with Mx)
K sparing diuretics, HPT medications
Haemolysed blood specimens
Low (hypokalaemia) Excess K excretion due to diuretics Steroid excess GI losses eg vomiting, diarrhoea Insulin therapy Refeeding syndrome K excretion
Other electrolytes
Ca, Mg, PO4
Specific homeostatic mechanisms to regulate blood levels
Serum levels are usually not an indicator of dietary intake or body stores
Significance in nutrition:
Related to clinical management in sick patients
Example: refeeding syndrome
Calcium (serum/ plasma)
2.15-2.6mmol/L
Not an indicator of dietary intake or body stores (bone density)
High serum Ca (hypercalcaemia)
Hyperparathyroid hormone (>PTH>bone resorption > Ca absorption)
Malignancy
Medication eg Ca channel blockers, thiazides, lithium
Excess Vit D and Ca from supplements
Low serum Ca (hypocalcaemia) Low albumin (fluc to bones
Magnesium (serum / RBC)
Serum 0.7-1.1mmol/L
Stores do not readily exchange with blood Mg
Equilibrium with no stores may take weeks
Day to day supply of Mg is dependent on diet
Serum and RBC Mg only pick up severe deficiency
Symptoms of mild deficiency: LOA, nausea, fatigue, cramps, numbness, tingling, abnormal heart rhythms, personality changes
Low Mg (hypomagnesaemia) can cause low serum Ca and K. NIDDM, diarrhoea, Crohns, IBD, stress, Mx (diuretics and antibiotics), alcoholism, old age (absorption, renal excretion), low Vit D, heavy periods, excessive sweating, severe burns
High Mg (rare) Renal failure, thyroid, addisons, antacids, laxatives, supplements, (cardiac arrest, low BP,
Phosphate
0.8-1.5mmol/L
Assists Dx of renal disorders, acid bass balanced detects endocrine skeletal and calcium disorders
Causes high PO4 Reduced excretion fur to renal failure High dietary intake combined with renal failure Excess Vit D intake (>absorption PO4) Starvation Hypoparathyroidism Cancer (>release from bone) T1DM (inadequate insulin, ketoacidosis)
Causes of low PO4 Poor diet, alcoholism, vomiting, malabsorption Hypomagnasaemia Antacids (bind PO4) Hyperparathyroidism
Urea
2.5-8mmol/L
Product of protein catabolism: made by liver. Dietary protein, muscle protein eg in muscle breakdown or wasting.
Excreted in urine (marker of renal function, creatine more widely used)
High urea seen in:
Renal failure (impaired excretion), including dialysis patients
Dehydration
Excessive protein catabolism, high protein intake
GI bleeding
Low urea seen in:
Low protein catabolism (malnutrition, already low protein stores) low dietary protein intakes
Vomiting
Malabsorption
Liver failure
Serum and urinary urea levels o not indicate protein status
Creatine
40-130mmol/L
Breakdown product of creation phosphate in muscle (marker muscle wasting)
Serum creatine is the most commonly used marker of renal function.
Serum creatine used to calculate creatine clearance- a marker of GFR
In renal impairment
In renal impairment < creatine excretion
Increased serum levels of creatine
High serum creatine
CKD, high protein intake, dehydration, muscle breakdown, haemorrhage
Low serum creatine
Minimal clinical significance
Often seen in malnutrition/ low muscle weight or wastage- low creatine turnover due to low stores
Liver function (damage) tests
Enzymes released by dead or dying liver cells are LFTs including ALT, GGT, AST, ALP, LDH, bilirubin which breaks down haem from haemoglobin liver/pancreatic function, and total serum protein and albumin therefore elevated upon liver injury/ disease
Often due to hepatitis, cirrhosis, inflamed liver or gut problems, infection etc.
Serum total protein (made by liver)
Consist of albumins and globulins
Reference range 60-80gL
Does not correlate with whole body protein status
Low total serum protein is not specific for low body protein status or intake
Elevated levels do not mean high body protein stores or high dietary intake- could be elevated in dehydration.
Albumin
Most abundant of the blood proteins
Serum reference range 35-50g/L
50/50 intracellular/ extracellular
Serum albumin produced by liver
Protein in highest concentration in blood
Hinds water and regulated blood vol by maintaining oncotic pressure and microvascular integrity
Transports hormones, fatty acids, bike salts, bilirubin, calcium and drugs
Maintains acid base balance, is an antioxidant and anticoagulant.
Low serum albumin
Rarely an indicator of low dietary protein intake
Does not respond directly to increasing protein intakes
Most cases related to illness not nutritional status.
Nah however indicate someone with increased requirements not getting enough
Hypoalbumineria
In associate with peripheral oedema
In chronic illness associated with inflammation - serum albumin may be low for similar reasons to acute illness/ infection
Chronic liver disease; impaired hepatic synthesis of albumin, kidney failure enteropathy. Elderly have decreased albumin synthesis
Hyperalbumineria
Shift from extravascular to intravascular space
Serum albumin may actually increase starvation
Dehydration
Anabolic steroids
Vit A deficiency
Nitrogen balance
A measure of net protein metabolism status
Based on assumption that almost all of the body’s nitrogen is in proteins
Nitrogen balance is the net balance between nitrogen intake (from dietary protein) AND nitrogen losses (urinary and faecal excretion, other small losses)
Application- monitoring responses to nutrition therapy, eg if goal is rehab, is patient in pos nitrogen balance?
Not useful for measuring total body protein stores/ status
Post nitrogen balance associated with muscle gains, growth, late pregnancy.
Neg nitrogen balance associated with protein catabolism, severe illness, trauma etc.
Measuring nitrogen balance 24 hour urinary urea
Usually measured over 24 hour
Protein intake must be quantified, issues with accuracy of measurements and estimations
24 hour urinary collection analysed for N and other metabolites
Stool collected if possible
Assumptions made for other losses; skin, endogenous
But is expensive and time consuming, hard to get complete samples and applications often limited to ICU and research
Does indicate inflammation
CRP (C reactive protein) <5mg/L
Made my liver in response to acute inflammatory stimuli eg cytokines
Blood levels rise in response to inflammation ref range <5mg/L
Marker or acute systemic inflammation usually due to infections, injury, arthritis, bowel problems and diet
Plays a role in defence against infection and innate immunity
Activates compliment system to remove pathogens/ immobilise antigens
Assistance with clearing necrotic and apoptotic cells. Decreased with exercise, healthy diet etc
May be due to metabolic syndrome, bowel problems, digest with high Gi/ trans fat/ protein B12/ Fe
High sensitivity CRP <1mg/L
CRP test- gross inflammation
HsCRP- low levels of CRP (chronic), predictor of increased heart attack risk, stroke, atherosclerosis, even when cholesterol levels are okay in patients without history of CHD. <1mg/L low risk, 1-3mg/L average risk, >3mg/dL high risk
Application- CVD?, low grade chronic infection?, diet high in GI trans fat protein, B12
Erythrocyte sedimentation rate (ESR)
Detects chronic non specific inflammatory, infectious and necrotic processes
Measurement of the rate at which RBC settle in saline solution plasma over a specific period of time
Inflammation increases content of protein (fibrinogen made in liver) within plasma causing RBCs to stack up on one another increasing their weight
Used to monitor disease progression and treatment efficacy
- chronic sever inflammatory disorders eg crohns, injury, chronic infections
- metastatic cancer
- autoimmune disease
- severe anaemias and B12 deficiency
CPR and ESR
Raised ESR and normal CRP
- chronic inflammation was present but has recently resolved
Raised ESR and CRP
- currently active chronic inflammatory state
Normal ESR and raised CRP
- acute inflammation as ESR not yet responded
