Why must vigilance continue into the post-operative period for both homo- and heterozygous patients?
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To avoid precipitating a crisis.
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Why must vigilance continue into the post-operative period for both homo- and heterozygous patients?
To avoid precipitating a crisis.
Are homozygous patients suitable candidates for day surgery?
No, homozygotes are not suitable candidates for day surgery.
What should be considered for homozygous patients undergoing intermediate to high-risk procedures post-operatively?
They should be considered for critical care post-operatively.
What should be administered to patients post-operatively?
Supplemental oxygen.
When should intravenous fluids be continued until?
Until the patient is eating and drinking.
How should effective analgesia be ensured post-operatively?
Using a multimodal approach and involving the pain team.
What are the common cardiovascular manifestations of rheumatoid arthritis (RA)?
Pericardial effusions are uncommon and usually asymptomatic, but can rarely cause tamponade. Valvular or myocardial involvement is rare.
What does 'atlanto-axial subluxation' mean?
Partial or incomplete dislocation of the joint between the first cervical vertebra (C1, atlas) and the second cervical vertebra (C2, axis).
What condition should be avoided post-operatively?
Hypothermia.
What is diabetes mellitus (DM)?
Diabetes mellitus (DM) is a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both.
What is the most common lung manifestation of rheumatoid arthritis?
Pleural effusions.
What percentage of patients with Down's Syndrome (DS) have congenital heart disease?
Up to 50%.
Why is inadequate analgesia for elderly surgical patients a concern?
It contributes to post-operative morbidity including delirium, cardiorespiratory complications, and failure to mobilize.
What is the atlas in the context of cervical vertebrae?
The atlas is the first cervical vertebra (C1) that holds up the skull and is unique because it has no body and is fused to C2 below it.
How is Type 1 diabetes characterized?
Type 1 diabetes is characterized by the loss of insulin-producing beta cells of the islets of Langerhans in the pancreas, usually via an immune or idiopathic mechanism. It typically presents in childhood and requires exogenous insulin administration to prevent ketosis.
What should be considered if respiratory abnormalities are found in a patient with rheumatoid arthritis?
Lung function testing.
What are common congenital heart abnormalities in patients with Down's Syndrome?
Atrial septal defect (ASD), ventricular septal defect (VSD), patent ductus arteriosus (PDA), and tetralogy of Fallot (TOF).
How should pain be assessed in elderly patients post-operatively?
Pain should be assessed regularly, with pain levels and sedation scores documented. Non-verbal cues should also be used due to potential cognitive impairment.
What is the axis in the context of cervical vertebrae?
The axis is the second cervical vertebra (C2) that forms a pivot on which C1 can rotate, allowing head movement.
What are the main characteristics of Type 2 diabetes?
Type 2 diabetes is characterized by insulin resistance, which may be combined with relatively reduced insulin secretion. Main risk factors include central obesity, increasing age, and family history.
What renal complication can rheumatoid arthritis cause?
Amyloidosis, which can lead to renal failure.
What is the benefit of using peri-operative analgesia protocols?
They improve patient satisfaction but should be individualized based on factors like previous chronic pain status and renal function.
Which congenital heart defect in Down's Syndrome patients does not cause a left-to-right shunt?
Tetralogy of Fallot (TOF).
What is the odontoid peg or dens?
A protrusion from the upper anterior surface of C2 that sticks up through where the body of C1 should be to articulate with the anterior arch of C1.
What is gestational diabetes?
Gestational diabetes is any degree of glucose intolerance with onset or first recognition during pregnancy.
What are the nervous system manifestations of rheumatoid arthritis?
Carpal tunnel syndrome, polyneuropathy, and compression of nerves at the cord or root.
What is the recommended approach to analgesia for elderly patients?
A multimodal approach, including local anesthetic infiltration, wound catheters, regional anesthetic techniques, and the WHO analgesic ladder.
What can left-to-right shunt defects in Down's Syndrome patients lead to?
Pulmonary hypertension.
What causes atlanto-axial subluxation in rheumatoid arthritis patients?
Degeneration of the bursa next to the transverse ligament of the atlas, causing the ligament to weaken and allowing the odontoid peg to move and potentially impinge on the spinal cord.
How is hypertension defined?
Hypertension is defined as a systolic blood pressure (SBP) >140 mmHg or a diastolic blood pressure (DBP) >90 mmHg.
What are impaired glucose tolerance (IGT) and impaired fasting glucose (IFG)?
IGT and IFG are intermediate conditions where glucose levels do not meet the criteria for diabetes but are too high to be considered normal. They indicate a high risk of developing diabetes later.
What are the haematological complications associated with rheumatoid arthritis?
Anaemia of chronic disease and anaemia secondary to gastrointestinal blood loss caused by NSAID use.
Why should NSAIDs be used with caution in elderly patients?
Due to the risk of gastric bleeding and nephrotoxicity. They should be used at the lowest dose and for the shortest duration, with proton pump inhibitors prescribed and U&Es monitored.
What should be done if congenital heart disease is suspected in a Down's Syndrome patient before surgery?
Patients must be investigated and optimized by a cardiologist.
What are the key blood test findings that help confirm a diagnosis of sickle cell anaemia?
Low Hb (6–8 g/dL), high reticulocyte count (10–20%), elevated bilirubin, presence of target cells, sickled cells, and Howell–Jolly bodies on blood film.
What is the function of the transverse ligament of the atlas?
It is a thick, strap-like ligament attached to each side of the anterior arch of the atlas, looping behind the odontoid peg to hold it snugly against the arch.
What percentage of people over the age of 65 have hypertension?
Almost 50% of people over the age of 65 have hypertension.
What are the criteria for impaired fasting glucose (IFG)?
Fasting plasma glucose levels between 5.6–6.9 mmol/L.
What eye condition is associated with rheumatoid arthritis?
Keratoconjunctivitis sicca (dry eyes).
Why is it important to identify whether a fall was mechanical or secondary to another cause in elderly patients?
To determine if the fall was due to a mechanical issue or a secondary cause like syncope.
How should morphine and other opiates be administered to elderly patients?
Cautiously and with dose adjustments, especially in patients with renal impairment, respiratory compromise, or cognitive impairment.
Why might prophylactic antibiotics be considered at induction for Down's Syndrome patients?
To prevent endocarditis.
Why is atlanto-axial subluxation potentially catastrophic?
Because the vertebrae of C1 and C2 can move out of their correct positions and impinge on the spinal cord, leading to cord compression at a high level.
What is the purpose of the Sickledex test in diagnosing sickle cell anaemia?
The Sickledex test induces sickling by adding sodium metabisulfite to the sample, confirming the presence of HbS but cannot differentiate between HbAS and HbSS.
Why is there a low threshold for invasive blood pressure monitoring in elderly patients?
Because large blood loss or fluid shifts are expected and/or an underlying cardiovascular disease is suspected.
What are the risks associated with untreated hypertension?
Untreated hypertensive patients are at significantly increased risk of stroke, myocardial infarction, heart failure, renal failure, and hypertensive retinopathy.
What are the criteria for impaired glucose tolerance (IGT)?
Glucose levels between 7.8–11.1 mmol/L (2 hours post glucose load).
What should be done for patients on steroid therapy in the peri-operative period?
They may need steroid supplementation.
What should be done with implantable defibrillators (ICDs) before surgery?
ICDs need to be turned off prior to surgery.
What are the features of post-operative delirium in elderly patients?
Acute confusion, disorientation, restlessness, agitation, fear, disturbed sleep, and hallucinations, often worse at night.
What factors can make venipuncture difficult in Down's Syndrome patients?
Obesity and/or learning difficulties.
What is rheumatoid arthritis (RA)?
RA is a multi-system disease causing symmetrical deforming inflammatory polyarthropathy.
What are the acute complications of diabetes?
Diabetic ketoacidosis (DKA), hyperosmolar non-ketotic state (Honk), and hypoglycaemia.
How common are symptoms of atlanto-axial subluxation in rheumatoid arthritis patients?
Symptoms are actually rare, even though atlanto-axial subluxation is reasonably common on X-ray.
Which test is considered definitive for diagnosing sickle cell anaemia?
Electrophoresis, as it determines the type and proportion of HbS present.
Why is depth of anaesthesia monitoring useful in elderly patients?
Because the dose of anaesthetic agents required to induce and maintain anaesthesia decreases with age, but the deleterious cardiovascular effects increase.
What percentage of hypertension cases are primary (essential) hypertension?
Primary (essential) hypertension accounts for 90% of cases.
What are some other specific types of diabetes?
Other specific types include genetic defects of beta-cell function, genetic defects in insulin action, diseases of the exocrine pancreas, endocrinopathies, drug- or chemical-induced diabetes, infections, uncommon forms of immune-mediated diabetes, and other genetic syndromes sometimes associated with diabetes.
Why should disease-modifying anti-rheumatic drugs (DMARDs) not be stopped without discussion with the patient's rheumatologist?
Because their benefits may outweigh their risks, despite causing immunosuppression which may delay wound healing and increase the risk of infection.
How should diabetic patients be prioritized on the operating list?
Diabetic patients should be prioritized to minimize starvation time.
How often should pacemakers (PPMs) be checked before surgery?
Pacemakers should have been checked within the last 6 months.
What are some causes of post-operative delirium?
Drugs, infection, metabolic imbalances, hypoperfusion, hypoxia/hypercarbia, and pain.
What can be used to ease venipuncture in Down's Syndrome patients?
Topical local anaesthetic agents applied to potential venipuncture sites.
Which gender is more commonly affected by rheumatoid arthritis?
Women are more commonly affected than men.
Which type of diabetes is more commonly associated with diabetic ketoacidosis (DKA)?
Type 1 diabetes.
What pre-operative measures should be taken for a patient with sickle cell disease?
Involve the haematology team, assess disease severity, aim for HbS <40% and Hb 10–12 g/dL for major surgery, cross-match blood early, ensure vaccinations and regular penicillin and folic acid, keep nil by mouth duration minimal, and avoid sedatives.
How should the dose of induction agents, inhalational agents, benzodiazepines, and opioids be adjusted for elderly patients?
Reduced doses should be used due to increased sensitivity and prolonged effects.
What are some secondary causes of hypertension?
Secondary causes of hypertension include renal disease (e.g., renal artery stenosis), endocrine disease (e.g., Conn’s syndrome/phaeochromocytoma), and pregnancy-related disease (e.g., pre-eclampsia).
What are the key aspects of post-operative care for patients with rheumatoid arthritis?
Continue rheumatoid medication if possible, keep patients well hydrated and monitor renal function, give early and regular physiotherapy, and provide DVT prophylaxis while immobile.
What should patients on oral hypoglycaemic agents do if starvation times are limited to one meal?
They should continue only metformin and pioglitazone as normal on the day of surgery and omit all others.
What is post-operative cognitive dysfunction (POCD) and how does it present?
POCD resembles dementia and can present weeks or months after surgery, with features including changes in mood and behavior, and impairments in memory, learning, language, and motor function.
Why is gastro-oesophageal reflux disease (GORD) a concern in elderly surgical patients?
GORD can increase the risk of aspiration during surgery.
What gastrointestinal issues are more frequent in Down's Syndrome patients and increase the risk of aspiration during anaesthesia induction?
Gastro-oesophageal reflux, duodenal atresia, and gastric paresis.
What percentage of the population worldwide is affected by rheumatoid arthritis?
Approximately 2% of the population worldwide.
Which type of diabetes is more commonly associated with hyperosmolar non-ketotic state (Honk)?
Type 2 diabetes.
How should oxygenation be managed peri-operatively in patients with sickle cell disease?
Pre-oxygenate well and maintain oxygenation with an appropriate FiO2.
What are the classifications of hypertension based on systolic and diastolic pressure?
Stage 1 (mild): 140–159/90–99 mmHg, Stage 2 (moderate): 160–179/100–109 mmHg, Stage 3 (severe): 180–209/110–119 mmHg, Stage 4: >210/>120 mmHg, Isolated systolic hypertension: >150/<90 mmHg.
What is the recommended administration method for intravenous induction agents in elderly patients?
They should be administered slowly and at a reduced dose due to increased arm–brain circulation time.
What should patients on insulin do if starvation times are limited to one meal?
They should continue intermediate or long-acting insulins and either halve or omit short-acting insulins, depending on the type of insulin regimen.
What is the process of 're-enablement' in post-operative care?
Re-enablement involves early mobilization, rehabilitation, physiotherapy, and occupational therapy to return a patient to their pre-operative functional level, requiring a multidisciplinary team approach.
How can joint replacements affect surgery in elderly patients?
Joint replacements can affect the placement of the diathermy pad and patient positioning for surgery.
What measures can be taken to reduce the risk of aspiration in Down's Syndrome patients during anaesthesia induction?
Consider early nasogastric tube (NGT) placement, pre-medicating with prokinetic agents and antacids, and/or using a rapid sequence induction technique.
Why must care be taken when moving patients with RA or removing sticky tape?
Steroid therapy causes thinning of the skin, making it fragile and prone to tearing.
What are the chronic vascular complications of diabetes?
Accelerated atherosclerosis, cerebrovascular disease, coronary artery disease, hypertension, and peripheral vascular disease.
What are the key considerations for maintaining normothermia during surgery for patients with sickle cell disease?
Use fluid warmers and warming blankets, and minimize shivering to reduce oxygen consumption.
What lifestyle changes might be recommended for managing primary hypertension?
Lifestyle changes may include weight reduction, increased exercise, and dietary changes such as reducing salt intake.
Why are elderly patients more prone to hypotension during surgery?
Because their autonomic responses are blunted.
What should be done if starvation times are expected to exceed one meal?
All patients should receive a Variable Rate Intravenous Insulin Infusion (VRIII).
What are some general health issues more common in Down's Syndrome patients?
Obesity, increased incidence of hypothyroidism, impaired immunity, increased incidence of leukaemia, and increased incidence of hepatitis B.
Why is it important to review drug history and allergies in elderly patients?
Polypharmacy is common and there is an increased risk of drug interactions.
What should be monitored closely when positioning RA patients on the operating table?
Pressure areas must be closely monitored.
What are the early signs of diabetic nephropathy?
Proteinuria and elevated serum creatinine.
Why should arterial tourniquets be used with caution in patients with sickle cell disease?
They can cause circulatory stasis, leading to venous sludging and sickling.
What are some considerations for intravenous access in elderly patients?
Veins are more mobile, cannulas are more prone to tissuing, and skin is more prone to damage on removal of cannula dressings.
What classes of antihypertensive medication might be prescribed?
Classes of antihypertensive medication include diuretics (e.g., bendroflumethiazide), β-adrenoceptor antagonists (e.g., atenolol), angiotensin-converting enzyme inhibitors (e.g., ramipril), angiotensin II inhibitors (e.g., losartan), calcium channel antagonists (e.g., amlodipine), α-adrenoceptor antagonists (e.g., doxazosin), and potassium channel activators (e.g., nicorandil).
How often should blood glucose be measured intra-operatively and in the immediate post-operative period?
Blood glucose should be measured hourly.
What does the premorbid level of exercise tolerance indicate in elderly patients?
It provides an indication of cardiopulmonary reserve.
Why might RA patients be unable to use devices like patient-controlled analgesia pumps?
Due to stiffness, deformity, joint pain, and lack of fine motor control.
What are the symptoms of autonomic neuropathy in diabetic patients?
Postural hypotension and impaired gastric motility.
Why is intravenous regional anaesthesia contraindicated in sickle cell disease?
Because prolonged venous stasis would result in sickling through the limb.
Why should all elderly patients be pre-oxygenated before surgery?
Because age causes a gradual increase in closing capacity, increasing the risk of desaturation.
What should be done if pre-operative glucose is above 12 mmol/L?
Check blood and urinary ketones. If <3+, administer subcutaneous insulin and reassess; if >3+, cancel surgery and treat as diabetic ketoacidosis (DKA).
Why is knowledge of social circumstances important in elderly surgical patients?
It helps in discharge planning.
How can temporomandibular joint involvement affect RA patients during anaesthesia?
It may limit mouth opening.
What is the risk associated with peripheral neuropathy in diabetic patients?
Increased risk of tissue damage and ulceration.
How should hydration be managed peri-operatively in patients with sickle cell disease?
Give intravenous fluids to maintain hydration and prevent venous sludging.
What airway management challenges are more common in elderly patients?
Edentulous patients are more difficult to face-mask ventilate, and neck stiffness, cervical spondylosis, or arthritis may limit neck extension, making airway maintenance and intubation more difficult.
What is the target blood glucose range during surgery?
The target blood glucose should be 6–10 mmol/L, with an acceptable range of 4–12 mmol/L.
Why should all elderly patients have a nutritional assessment on admission?
Good nutrition facilitates healing and recovery.
What is atlanto-axial subluxation and how common is it in RA patients?
Atlanto-axial subluxation is a condition where the first and second cervical vertebrae become misaligned, occurring in up to 25% of RA patients.
What is a common musculoskeletal complication in diabetic patients that can affect intubation?
Stiff joint syndrome due to collagen glycosylation.
What is the importance of maintaining good analgesia in patients with sickle cell disease during surgery?
Good analgesia reduces catecholamine surges and minimizes oxygen consumption; these patients may be opioid tolerant and benefit from early pain management review.
Why is meticulous care in patient positioning important for elderly patients?
To protect pressure points with adequate padding as the risk of neuropraxia and pressure sores is increased.
What is the purpose of the Mini Mental State Score in elderly patients?
To identify early onset dementia and memory impairment.
What should be used to enable early resumption of usual diet and self-managed diabetes regimen?
Multimodal analgesia and anti-emetics should be used.
What is Down's syndrome (DS) and how common is it?
Down's syndrome is one of the most common chromosomal abnormalities, occurring in approximately 1 in 700 live births. It is due to the presence of either a whole or part of an extra 21st chromosome, termed trisomy 21.
What should be assessed in RA patients to ensure neck stability before anaesthesia?
Assess the patient's range of neck movement and consider cervical spine X-rays if there is any doubt about neck stability.
What are the aims of pre-operative assessment for diabetic patients?
Determine the severity of systemic complications, assess blood glucose control, and exclude ketoacidosis.
What measures should be taken to prevent hypothermia in elderly patients during surgery?
Use fluid warmers and body warmers routinely and undertake intra-operative temperature monitoring.
What should be noted from the observation chart review in elderly patients?
Baseline blood pressure, as patients are prone to intra-operative hypotension.
What principles should be implemented for early mobilisation and resumption of normal diet?
The principles of the Enhanced Recovery Programme should be implemented.
What is the primary cause of Down's syndrome?
The primary cause of Down's syndrome is non-disjunction of the chromosomes (95%), but it can also be due to translocation.
What is a sign of potential anterior subluxation in RA patients?
A gap of >3 mm between the odontoid peg and the arch of the atlas in lateral flexion.
What are diabetic patients at increased risk of during the peri-operative period?
Silent myocardial infarction (MI), stroke, pressure sores, infections, and ketogenesis.
What type of anaesthetic agents are preferred for maintenance in elderly patients?
Short-acting agents like desflurane and sevoflurane, as MAC is reduced in the elderly.
What is the minimum data set required for investigations in elderly surgical patients?
ECG, FBC, U&Es, and blood sugar.
Why might patients with Down's syndrome be anxious and uncooperative during anaesthesia?
Patients with Down's syndrome may have learning difficulties, leading to anxiety and uncooperativeness. Establishing rapport, tailoring explanations to their level of understanding, and considering pre-medication with an anxiolytic or sedative agent can help.
When is a Variable Rate Intravenous Insulin Infusion (VRIII) indicated?
VRIII is indicated if starvation time is expected to be more than one meal or if diabetes is decompensated.
What should be done if there is actual or potential subluxation in an RA patient's neck?
Use manual in-line stabilisation when manipulating the airway and consider awake fibre-optic intubation.
Why is good pre-operative glycaemic control important for diabetic patients?
Poor pre-operative glycaemic control is associated with greater post-operative mortality and morbidity.
What are the challenges in fluid management for elderly patients during surgery?
Reduced homeostatic compensation for blood and/or fluid loss, and patients may be prone to both dehydration and fluid overload.
What is vaso-occlusive crisis in sickle cell disease?
Sickled cells obstruct blood flow to an organ or tissue, causing pain and potential organ damage.
What is more important than the choice of anaesthesia (regional or general) in elderly patients?
The technique used must be administered responsively, taking into account the patient’s physiological status.
What is the recommended intravenous fluid for a VRIII?
0.45% sodium chloride with 5% glucose and either 0.15% potassium chloride (KCl) or 0.3% KCl.
What are the key respiratory system considerations for anaesthesia in patients with Down's syndrome?
Key considerations include atlanto-axial and atlanto-occipital instability, micrognathia, small mouth, macroglossia, short neck, excessive salivation, adeno-tonsillar hypertrophy, oro-pharyngeal hypotonia, and subglottic and tracheal stenosis.
How can crico-arytenoid involvement affect RA patients?
It can cause hoarseness and limit airflow, potentially causing stridor in severe cases.
What should be measured to assess blood glucose control in the preceding 2 months for diabetic patients?
Glycosylated haemoglobin (HbA1c) levels.
Why are most sickle cell patients on lifelong prophylactic penicillin?
Most patients have infarcted their spleens by an early age, increasing their risk of infections.
What should be done if capillary blood glucose (CBG) is <4 mmol/L during VRIII?
Reduce VRIII to 0.5 mL/h and administer 10% dextrose. Stop the infusion only if a long-acting insulin has been continued.
How should the head be positioned during intubation for patients with Down's syndrome?
Great care must be taken when positioning the head during intubation due to atlanto-axial and atlanto-occipital instability. Pre-operative symptoms of spinal cord compression should be assessed, and flexion-extension views of the C-spine may be considered.
What happens to blood glucose levels intra-operatively due to the surgical stress response?
Blood glucose levels rise.
What pre-operative assessment might be requested if crico-arytenoid involvement is a concern in RA patients?
A pre-operative nasendoscopic assessment of the larynx by ENT surgeons.
What is sequestration crisis in sickle cell disease?
Painful splenic enlargement results in anaemia and abdominal distension, managed supportively.
What should be done once the patient is eating and drinking after surgery?
Revert back to their regular medication, with possible dose adjustments and a period of overlap between VRIII and subcutaneous insulin administration.
What anatomical features in patients with Down's syndrome can contribute to difficulties during intubation?
Micrognathia, small mouth, macroglossia, and short neck can contribute to difficulties during intubation. A difficult airway trolley with appropriate emergency drugs should be ready and available.
What peri-operative management considerations should be made for diabetic patients undergoing elective surgery?
Maintain blood glucose during fasting, correct metabolic derangements, ensure good glycaemic control, and manage post-operative fluid/nutrition intake.
What triggers aplastic crisis in sickle cell disease?
Infection with parvovirus B19, which arrests red cell production for 2-3 days.
How should insulin be prescribed according to safety recommendations?
Insulin should be prescribed according to National Patient Safety Agency (NPSA) recommendations for safe use of insulin.
What should be considered to manage excessive salivation in patients with Down's syndrome during anaesthesia?
Excessive salivation can obscure the view during laryngoscopy and pose an aspiration risk. Pre-medicating with an anti-sialogogue should be considered.
What is haemolytic crisis in sickle cell disease?
The rate of red cell breakdown increases, usually seen in those with co-existing G6PD deficiency.
What are the implications of adeno-tonsillar hypertrophy and oro-pharyngeal hypotonia in patients with Down's syndrome during anaesthesia?
Adeno-tonsillar hypertrophy and oro-pharyngeal hypotonia may lead to obstructive sleep apnoea. Features of this condition should be elicited during pre-operative assessment, and upper airway obstruction can worsen after anaesthesia and opioids, necessitating extended recovery or HDU environment post-operatively.
What are the respiratory complications of sickle cell disease?
Acute chest syndrome, which manifests as pleuritic pain, cough, dyspnoea, haemoptysis, and fever. Recurrent episodes can lead to pulmonary hypertension and chronic respiratory failure.
Why might a smaller than predicted endotracheal tube be used in patients with Down's syndrome?
Subglottic and tracheal stenosis in patients with Down's syndrome may necessitate the use of a smaller than predicted endotracheal tube.
What cardiovascular complications are associated with sickle cell disease?
Hypertension and left ventricular hypertrophy.
What gastrointestinal complications can occur in sickle cell disease?
Acute sequestration syndrome of red blood cells in the liver or spleen, haemosiderosis secondary to repeated transfusions, and gallstones secondary to chronic haemolysis.
What is sickle cell anaemia?
Sickle cell anaemia is a haemoglobinopathy with autosomal recessive inheritance caused by a point mutation on the gene coding for normal haemoglobin (HbA) on chromosome 11, resulting in the formation of an abnormal β-haemoglobin chain referred to as 'HbS'.
What are the genitourinary complications of sickle cell disease?
Haematuria, renal failure secondary to acute papillary necrosis, and priapism.
What causes the formation of HbS in sickle cell anaemia?
A point mutation on the gene coding for normal haemoglobin (HbA) on chromosome 11, causing the substitution of valine for glutamic acid at position 6 on the β-haemoglobin chain.
What neurological complications can arise in sickle cell disease?
Stroke and meningitis.
What is the difference between homozygotes (HbSS) and heterozygotes (HbAS) in sickle cell anaemia?
Homozygotes (HbSS) have only abnormal haemoglobin, while heterozygotes (HbAS) have both abnormal and normal haemoglobin and are said to have 'sickle cell trait'.
Why are sickle cell patients at increased risk of infection by encapsulated organisms?
Splenic infarction increases the risk, necessitating vaccination and daily oral penicillin.
What populations are most likely to carry the sickle cell trait?
25% of West Africans, 10% of African Americans, and those of East Indian, Middle Eastern, and Mediterranean origin.
What are the ocular complications of sickle cell disease?
Proliferative retinopathy.
How does sickle cell trait confer protection against falciparum malaria?
The lifespan of red blood cells carrying HbS is reduced, preventing the malaria parasite from completing its life cycle within the red blood cells.
What musculoskeletal complications are associated with sickle cell disease?
Deformity of skull and long bones secondary to compensatory hyperplasia, bone pain, osteomyelitis commonly caused by Salmonella, and avascular necrosis, most commonly affecting the hip joint.
What is 'sickling' in the context of sickle cell anaemia?
At low partial pressures of oxygen, deoxygenated HbS polymerises, becomes insoluble, and precipitates to form elongated crystals or 'tactoids', causing red blood cells to become rigid and form a 'sickle' shape.
What skin complication is common in sickle cell disease?
Ulceration.
What factors increase the process of sickling in sickle cell anaemia?
Hypoxia, acidosis, dehydration, and hypothermia.
What are the challenges in managing chronic pain in sickle cell disease?
Opioid tolerance and pain management issues.
At what partial pressures of oxygen (PaO2) does HbS polymerise in homozygotes and heterozygotes?
In homozygotes, HbS polymerises at PaO2 between 5 and 6 kPa, while in heterozygotes, sickling occurs at much lower PaO2 of 2–3 kPa.
What are the consequences of sickled blood cells in sickle cell anaemia?
Sickled blood cells increase blood viscosity, reduce flow, and occlude smaller capillaries, causing venous thrombosis and distal organ infarcts. They also have a reduced lifespan of 10–20 days, leading to anaemia and jaundice.
What is the typical lifespan of red blood cells in sickle cell disease compared to normal red blood cells?
10–20 days for sickled red blood cells compared to the normal lifespan of 120 days.
What is a 'sickle cell crisis'?
Periods where the disease worsens in homozygotes with sickle cell disease.
At what age do clinical features of sickle cell disease typically appear, and why?
From 6 months of age, as adult haemoglobin begins to replace fetal haemoglobin, which has no β chains.
