AC1 guided learning Flashcards
What are the contents of the normal U&E test?
- Sodium (Na)
- Potassium (K+)
- Creatinine (Cr)
- Urea (U)
- eGFR
What additional tests to U&E are commonly requested which also come under the umbrella of biochemistry?
This is not a complete list, but common biochemical tests are: - Uric acid - Calcium/bone profile - Hormone panels - Blood glucose monitoring tests Creatinine Kinase
what systems are investigated through U&Es?
- Renal damage such as Acute Kidney Injury
- Bone turn over through calcium release
- Endocrine conditions which can cause electrolyte imbalances e.g. Addison’s
What can cause hyperkalaemia?
Tissue damage Acute kidney injury Haemolysis Addison’s disease Drugs
what can cause hypokalaemia?
High levels of insulin
Diarrhoea
Conns syndrome
Poor diet
what can cause hyponatraemia?
Water intoxication
Addison’s disease
Nephrotic syndrome
what can cause hypernatraemia?
Dehydration
Perspiration
High salt diet
Diabetes inspidous
what can cause raised urea?
AKI
Dehydration
CKD
what can cause raised creatine kinase?
Strenous exercise
Muscle death
Crush injuries
Sustained muscle contraction –e.g. tetany
what is creatine kinase?
CK is an enzyme responsible for utilization of ATP, particularly in muscles, producing photocreatine as an energy store for the muscle
what can cause raised creatinine?
Renal impairment,
Hypotension,
dehydration
Note creatinine is both generated and excreted by the kidneys
If a patient is found to have mildly raised potassium, what action should be taken?
- Review for possible medications associated with hyperkalaemia, and consider continued prescription
- Repeat blood test – in a serum sample with only mildly raised potassium, the likeliest cause is going to be complications in phlebotomy, e.g. tourniquet on too long, excess shaking in transit damaging blood cells, tube heating
Assuming hyperkalaemia is substantiated, what three physiological mechanisms give rise to hyperkalaemia? Give examples of each.
- Reduced excretion o Renal failure/impaired renal function o Drugs o Addison’s disease - Increased intake o Normally only issues with parenteral or IV fluids excess as it would be expected a healthy patient would be able to increase excretion - Excessive production – main source is break down od cells: o Haemolysis o Tumour lysis o Rhabdomyolysis o Drugs o Blood transfusion
Which common medications can cause hyperkalaemia?
- Spironolactone
- ACEi
- ARBs
- Omeprazole
- NSAIDs
What is a pneumothorax?
A pneumothorax is the presence of air in the intra-pleural space.
The intra-pleural pressure will increase (become less negative) and will eventually approach zero or even become positive.
Lack of negative intra-pleural pressure means the lungs collapse (remember their natural tendency is to collapse but they are held open by the negative intra-pleural pressure!) and also means that the chest wall tends to spring out.
What are the common causes of pneumothorax?
- spontaneous and idiopathic
- spontaneous and secondary to an underlying lung disease e.g. COPD, TB, asthma, lung abscess, cystic lung disease, lung cancer
- traumatic i.e. following injury to the chest wall.
What are the common symptoms associated with pneumothorax?
- sudden onset, unilateral chest pain, which is often pleuritic
- acute dyspnoea.
Signs of pneumothorax?
- reduced chest expansion of the affected side
- resonance or hyper-resonance on percussion over affected side
- absent breath sounds
additional for tension:
- deviation of trachea
- tachycardia
- hypotension
symptoms? of pulmonary fibrosis?
clinical signs of pulmonary fibrosis?
changes on CXR?
spirometry pattern?
progressive SOB
Digital clubbing can be seen and late, often fine, inspiratory crackles can be heard on auscultation of the lungs.
The disease is one of the interstitium and so you evidence of involvement of the supporting tissue of the lung parenchyma resulting in fine or coarse reticular opacities or small nodules.
restrictive pattern, FEV1/FVC normal or increased (as both reduced)
Joyce, a 57 year old woman who works as a cleaning lady. She has increasing shortness of breath which is starting to affect her ability to work and look after her grandchildren. Joyce is an infrequent attender at the General Practice, but often uses the walk in centre attached to the hospital where she works. The GP notes that the patient has been attending the walk in centre with ‘chest infections’ about every four months for a couple of years.
Joyce describes a cough, present throughout the year which is productive of sputum, two to three tablespoons a day. The sputum is often white, but can be yellow-green and this tends to be when she goes to the walk in centre.
DDx??
• Bronchiectasis • COPD • Asthma • GORD • Alpha 1 antitrypsin • Lung abscess - malignancy
preferred Dx is Bronchiectasis- this sputum production is every day (making COPD less likely) and is copious. There is no wheeze and no evidence of heart burn or waterbrash. Alpha-1-antitrypsin would normally have presented earlier and also affect the liver.
Ix for bronchiectasis?
Sputum culture: to look for micro-organisms present and their sensitivity to antibiotics
Blood tests to confirm infection: Full blood count and CRP/ESR
High-resolution CT (HRCT) scanning is the criterion standard for the diagnosis of bronchiectasis
Changes on CT for bronchiectasis?
- Cylindrical bronchiectasis has parallel tram track lines, or it may have a signet-ring appearance composed of a dilated bronchus cut in a horizontal section with an adjacent pulmonary artery representing the stone
- The diameter of the bronchus lumen is normally 1-1.5 times that of the adjacent vessel; a diameter greater than 1.5 times that of the adjacent vessel is suggestive of bronchiectasis
- Varicose bronchiectasis has irregular or beaded bronchi, with alternating areas of dilatation and constriction
- Cystic bronchiectasis has large cystic spaces and a honeycomb appearance; this contrasts with the blebs of emphysema, which have thinner walls and are not accompanied by proximal airway abnormalities ‘
• What are the organs of the haematolymphoid system?
o Thymus (organ) o Bone Marrow o Lymph nodes (organ) o Spleen (organ) o Mucosa associated lymphoid tissue
What are four major functions of the spleen?
o Production of an immunological response against blood borne antigens
o Removal of particulate matter and aged or defective blood cells from the circulation
o Recycling iron back to the marrow
o Extra-medullary haematopoiesis in the fetus and during certain bone marrow diseases
The spleen essentially performs the same function for blood that lymph nodes perform for the lymph
What is lymph?
. The lymph is formed by the excess fluid that is left in tissues due to the differences in hydrostatic and oncotic pressures from the arterial to venous ends of a capillary bed. Lymph will be greatest where the vessels are leaky e.g. during inflammation. Lymph will also contain dead cells, fragments of degraded tissue and any antigens that have broken through the physical barrier of the skin/mucosa.
What are antigen presenting cells?
o Non-professional (all cells nucleated cells of the body)- express MHC Class 1. Viral antigens of cancer antigens would be expressed by these cells in associated with the MHC Class 1 and would invoke a response by cytotoxic T cells.
o Professional APC (e.g. dendritic cells, macrophages, Langerhans cells) take in external antigen, process it and present it bound to MHC Class II receptors. Class II+ antigen promote T helper cell response, which then activate B cells.
What are B cells?
o B cells are derived from the bone marrow. Stimulated B cells will mature into plasma cells (antibody factories). The antibodies will be of one of five classes (Ig- G, A, D, M and E). The Ig will then be secreted into the circulation (a proportion will remain bound to B cell membrane to act as the B-Cell receptor). Once activated B cells will mitotically divide producing a mixture of plasma cells and memory B cells (capable of mounting a secondary immune response: more rapid, greater magnitude and produces IgG that the primary immune reponse)
What are T cells?
T cells o have effector and regulatory functions. T cells migrate from the bone marrow to the thymus where they develop into mature T cells (or undergo apoptosis if they are self-reactive). T cells then move into the secondary lymphoid organs e.g. lymph nodes and MALT, but are constantly circulating round. The major classes of T cells are:
♣ T helper cells- help other cells to perform their effector functions by secreting interleukins:
• TH1- promote a cell mediated reaction
• TH2- promote humoral immunity
• TH17- acute inflammation
♣ T cytotoxic cells- kill viral and cancer cells. Require help from TH cells to become active.
where are B cells and T cells in a lymph node?
B cells are in the follicles
Plasma cells are in the medulla
T cells are in the paracortex
What are the characteristic microanatomical features of the spleen?
♣ Red pulp: interconnected sinuses that are the tributaries of the splenic vein. The blood cells enter the parenchyma from capillaries, squeeze through the walls of the sinuses and drain out via the splenic vein (open circulation)
♣ White pulp (20% of mass): periarteriolar lymphoid sheaths consistently mainly of TH1 cells. There is a prominent marginal zone of medium cells.
What is a retrovirus?
A retrovirus is an RNA virus that replicates and produces its viral RNA from a DNA copy that is spliced into the host cell DNA. This requires the enzyme reverse transcriptase (transcription is the process of making RNA from DNA).
How is HIV transmitted?
Virus is found in blood, semen, cervical and vaginal secretions (it may also be in other body fluids, but there is no evidence linking these to transmission events). Transmission is most likely when the virus load (level) is highest.
The major modes of transmission are: unprotected penetrative sexual intercourse (>=90% of transmissions) (particularly high for recipients of anal sex), via infected blood and blood products (including sharing contaminated needles) and vertical transmission
What does vertical transmission mean? How likely is it?
Vertical transmission is the passing of the disease from mother to child. Most of this occurs in late pregnancy or during delivery. The likelihood depends on maternal viral load; if the mother’s HIV is suppressed, then transmission is <2%. Vertical transmission is more likely if the mother has primary HIV(see below), late stage HIV, other sexually-transmitted disease, or breast-feeds her infant.
How does the HIV virus cause disease?
HIV has specific tropism for CD4 positive T lymphocytes and also infects monocyte-macrophage lineage cells This infection and then destruction of immune system cells is responsible for the clinical manifestations.
Viral replication, killing of infected cells by cytotoxic T lymphocytes and natural killer cells and increased apoptosis in infected and uninfected CD4 T cells all leads to decline in CD4 positive T lymphocytes.
What are the stages of HIV infection?
Primary HIV infection, often called seroconversion, happens 10-30 days after exposure. It may be symptomatic with some (up to 70% of patients) or all (only 5-10% of patients) of: fever, pharyngitis, flu-like symptoms, generalized lymphadenopathy and maculopapular rash.
The infection then enters the asymptomatic phase, which may last up to 10 years or possible more, the virus is replicating in this time but not causing clinically overt disease. Sometimes persistent, generalized lymphadenopathy is present during this ‘asymptomatic” stage. The development of clinically overt symptoms signals the entry to the category of AIDS-related illness, or AIDS. The CDC (Communicable Disease Center) staging of HIV disease is different, using both CD4 T cell count (see question 6) and presence or absence of AIDS-defining condition (see question 8). The WHO stage is slightly different again. These are both surveillance definitions rather than ones used for patient care.
what are some aids-defining illnesses?
Candidiasis of bronchi, trachea or lungs. Lymphoma, Burkitt’s (or equivalent term).
Candidiasis, oesophageal.
Lymphoma, immunoblastic (or equivalent term).
Cervical carcinoma, invasive. Lymphoma, primary, of brain.
Coccidioidomycosis, disseminated or extrapulmonary.
Mycobacterium avium complex (MAC) or M. kansasii, disseminated or extrapulmonary.
Cryptococcosis, extrapulmonary. Mycobacterium tuberculosis, any site (pulmonary or extrapulmonary).
Cryptosporidiosis, chronic intestinal (>1 month’s duration).
Mycobacterium, other species or unidentified species, disseminated or extrapulmonary.
Cytomegalovirus (CMV) disease (other than liver, spleen or nodes).
Pneumocystis jirovecii pneumonia.
CMV retinitis (with loss of vision). Pneumonia, recurrent.
Encephalopathy, HIV-related. Progressive multifocal leukoencephalopathy.
Herpes simplex: chronic ulcer(s) (>1 month’s duration); or bronchitis, pneumonitis or oesophagitis.
How do we diagnose HIV?
HIV antigen testing (quick)
Antibody to HIV detection (After 1-2 months)
Older HIV tests relied on detection of antibody to HIV, using ELISA. However, the seroconversion to antibody positivity takes 1-2 months on average, leading to the “seroconversion window” when diagnosis could be missed because no antibody is present.
The testing strategy requires 1 screening test followed by 2 confirmatory tests on the same sample using different targets, plus a 2nd specimen from the patient.
Newer tests and testing strategies detect HIV antigen, usually the p24 envelope protein, they are therefore positive earlier than the antibody based tests
HIV RNA can also be detected in blood using PCR. This can be quantitative and is used for monitoring viral loads.
DDx for a maculopapular rash in a child?
Viral exanthem– rubella, measles, scarlet fever, roseola infantum, erythema infectiosum/fifth disease
Drug eruption
Allergic reaction
What the white spots on the tongue pathognomic in measles called?
Koplik spots. They are pathognomic for measles and occur 1-2 days before the rash onset. They are usually located near the lower pre-molars. The spots are small greyish-white surrounded by an erythematous base.
What is the normal heart rate for a 4 year old?
110-160 bpm
What are the Sx of measles?
- m/p rash, starting on neck and face and spreading to trunk and limbs.
- fever
- prodome: malaise, rhinorrhea, conjunctivitis
- koplik spots
What protection does the MMR provide against measles?
90%
How is measles spread?
airborne or droplet transmission
how long is incubation period of measles?
8-14 days
how long is a patient with measles infectious?
from start of prodromal symptoms to 4 days after rash onset
HCPs in contact with infectious patient with evidence of protection can continue to work normally, but HCPS without MMR should be excluded from work from 5th day after exposure until 21 days after exposure (unless they are found to be IgG positive)
how is measles managed?
supportive treatment - hydration and anti-pyretics
advice verbally and written to keep patient away from susceptible individuals until 5 days after rash onset, and advise on deterioration and complications
send saliva smple to lab to confirm diagnosis, and notify
what are the complications of measles?
otitis media 8% pneumonia 3% diarrhoea 8% convulsions 0.5% encephalitis 0.1% death 0.02
What endocrine response would you expect to fluid deprivation ?
1) Hypothalamic osmoreceptors notice a change in osmolality (more concentrated) and respond by releasing antidiuretic hormone.
Activation of the renin-angiotensin-aldosterone system in response to drop in pressure
