Biochem Flashcards
What is the acute phase response to injury?
A systemic reaction characterised by inflammation, fever, increased WBC count, changes in blood protein levels, and altered metabolic processes
Aimed at containing the injury site and initiating healing processes.
What is the primary aim of the acute phase response?
To contain the injury site and initiate healing processes
This involves the production of acute phase reactants from the liver.
What occurs locally at the injury site during the acute phase response?
Blood vessels dilate, allowing fluid and immune cells to leak out, causing swelling, redness, and pain.
What are cytokines?
Inflammatory signaling molecules released by cells at the injury site
Examples include interleukin-1 (IL-1), interleukin-6 (IL-6), and tumour necrosis factor-alpha (TNF-alpha).
What is the role of the liver in the acute phase response?
It produces increased levels of acute phase proteins in response to cytokines.
Name some examples of acute phase proteins.
- C-reactive protein (CRP)
- Fibrinogen
- Serum amyloid A (SAA)
- Alpha-1 antitrypsin
- Haptoglobin
- Complement proteins
What is the function of C-reactive protein (CRP)?
It binds to damaged cells and pathogens to facilitate their clearance by phagocytes.
What role does fibrinogen play in the acute phase response?
Involved in blood clotting and wound healing; converted to fibrin at the site of injury.
What is the function of serum amyloid A (SAA)?
Helps to recruit immune cells to sites of inflammation.
What does alpha-1 antitrypsin inhibit?
Inhibits proteases that could damage tissues during inflammation.
How does the acute phase response induce fever?
Pro-inflammatory cytokines like IL-1 and TNF-alpha act on the hypothalamus.
What is leukocytosis?
Increased WBC count, particularly neutrophils, which are important for phagocytosis.
What metabolic changes occur during the acute phase response?
Increased production of glucose and a shift to catabolic processes to provide energy for tissue repair.
What happens to plasma protein levels during the acute phase response?
Some proteins like albumin may decrease while acute phase proteins increase.
What are the roles of growth factors and cytokines in tissue repair?
Promote tissue repair, stimulate cell proliferation, and form new blood vessels (angiogenesis).
What are the effects of vasodilation and increased permeability?
Facilitate movement of immune cells and proteins to the injury site.
What is the purpose of coagulation in the acute phase response?
Upregulation of clotting factors to form blood clots and limit further blood loss.
How is the acute phase response resolved?
Activation of anti-inflammatory cytokines and production of specialised pro-resolving lipid mediators.
What is the importance of the acute phase response?
- Defence against infection
- Tissue repair
What can happen if the acute phase response is problematic?
- Chronic inflammation
- Severe systemic inflammation leading to SIRS
What is a common clinical tool for assessing inflammation?
Monitoring C-reactive protein (CRP) levels.
What are the two byproducts formed when cells use nutrients to produce energy?
Carbon dioxide and hydrogen
What determines the acidity and alkalinity in our body?
H+ ions measured by pH
What can changes in pH homeostasis cause?
Protein denaturation
Which clinical conditions can affect acid-base balance?
- Diabetes ketoacidosis
- Medications
- Treatments
- Diarrhoea
- Vomiting
True or False: Diet alone can cause acidosis or alkalosis.
False
What is a common cause of acid-base imbalance in critically ill patients?
Infection or acute illness
What is the relationship between potassium and bicarbonate?
They are negatively correlated
What happens to bicarbonate levels when potassium levels rise?
Bicarbonate levels go down
What indicates that dietary intervention is not useful when bicarbonate is less than 20?
Bicarbonate is too low and needs to be addressed first
What can cause respiratory alkalosis?
Excess CO2 exhalation
What is metabolic alkalosis caused by?
- Non-volatile alkali
- Exogenous alkali (e.g., NAHCO3 administration)
- Loss of acid
What can cause respiratory acidosis?
CO2 retention
What is a hallmark biochemical feature of refeeding syndrome?
Hypophosphatemia
What is C-reactive protein (CRP) an indication of?
- Disease activity
- Effectiveness of pharmacological treatment
What does a high level of CRP indicate?
An inflammatory response or stress/infection
What is the normal range for CRP levels?
< 5-10 mg/l
How can albumin levels relate to mortality risk?
Lower albumin = greater mortality risk
What can cause low levels of albumin?
- Reduced synthesis
- Increased catabolism
- Abnormal losses
- Overhydration
What is the primary function of albumin?
Maintaining colloid oncotic pressure
What are the three types of fluid in total body water distribution?
- Interstitial volume
- Transcellular volume
- Intravascular/plasma volume
What can cause hypovolemia?
- Increased body water and salt losses
- Diuretics
- Diabetes insipidus
What is hyponatremia?
Low sodium levels
What can cause hyperkalemia?
- Acidosis
- Increased intake
- Renal causes
What is the effect of insulin on potassium levels?
Potassium moves into the cell
What is the relationship between magnesium and potassium?
Magnesium deficiency can lead to potassium depletion
What is refeeding syndrome?
Potentially fatal shifts in fluids and electrolytes during refeeding of malnourished patients
What are the clinical manifestations of refeeding syndrome?
- Hypophosphatemia
- Hypomagnesemia
- Hypokalaemia
- Fluid retention
- Respiratory failure
Who is at risk for refeeding syndrome?
- Elderly patients
- Alcohol excess
- Chronic malnourished patients
- Patients with diabetes on insulin
What should be checked together when assessing phosphate levels?
- Calcium
- Magnesium
What is the corrected calcium formula?
Co Ca = [Ca] + 0.02 x (40 - [Albumin])
What is the primary role of calcium in the body?
Main mineral involved in various physiological processes
What are the effects of thiazide diuretics?
- ↓Na+, Cl- cotransport
- ↑K+ loss
- ↓Ca++ excretion
What is the significance of blood tests during starvation?
Normal serum electrolytes may not indicate low risk of feeding
What occurs during the refeeding phase?
Rapid conversion to glucose as a main source of energy
What condition do patients suffer from that leads to malabsorption?
Patients who suffer from malabsorption
What is a key factor in managing patients with malabsorption?
Dietetic assessment is key
Refeeding syndrome guidance is primarily based on what?
Expert opinion
What type of guidelines exist specifically for ED clinics regarding refeeding?
Completely separate refeeding guidelines
According to PENG 2018 guidance, at what calorie range should nutrition support be initiated?
10-20kcal/kg
What should be taken into account when feeding obese patients?
Avoid over-feeding; use ideal/adjusted weight for calculations
In specialized units, what higher energy intake may be appropriate for AN patients?
20-40kcal/kg
What does NICE 2006 recommend checking regarding refeeding syndrome?
Local policies
How were recommendations for refeeding syndrome formulated?
Based on previous published reviews and expert consensus
What is the rationale for disagreement with supplementation of electrolytes before feeding?
Most deficits are intracellular and cannot be corrected without low energy provision
What should be monitored during refeeding?
Refeeding bloods (K, P, Mg, Ca), U+E, glucose load, blood glucose, fluid balance, nutrient provision, vital signs
What is the recommended calorie intake for extreme cases according to NICE 2006?
5-10kcal/kg
How should feed be increased during refeeding?
Gradually to requirement but monitor closely
What type of oral nutritional supplements should be avoided at the initiation of feeding?
Fat free ONS
What micronutrient should be provided from the onset of feeding?
Thiamine
What is the recommendation for thiamine dosage at the onset of feeding?
300mg a day + VitB co strong
What should be monitored in patients at risk of refeeding syndrome?
Individualised dietetic assessment is key
What is crucial for managing patients with refeeding syndrome?
Monitoring
What should be balanced in the management of refeeding syndrome?
Balance between refeeding and delay feeding
What should be looked at in the conclusions for refeeding syndrome management?
Trends, biochemistry, fluid balance, medications, acid-base balance, patient signs and symptoms
True or False: There is a lack of standardization in the literature on refeeding syndrome.
True
