Central chemoreception refers to the detection of changes in CO2/H+ within the brain and the associated effects on breathing. In the conscious animal the response of ventilation to changes in the brain’s interstitial fluid (ISF) pH is very sensitive. Note that a small change in cerebrospinal fluid (CSF) pH from 7.30 to 7.25 is associated with a doubling of alveolar ventilation; it is a very sensitive reflex response. Note also that the relationship of alveolar ventilation to ISF pH is essentially the same for both types of stimulation, metabolic acid-base disorders and primary CO2 stimulation.

Seasonal affective disorder (SAD) is a type of depression that’s related to changes in seasons. SAD begins and ends at about the same time every year. For most people with SAD, the symptoms start in the fall and continue into the winter months, sapping the person’s energy and making him feel moody. Less often, SAD causes depression in the spring or early summer.

Treatment for SAD may include light therapy (phototherapy), medications and psychotherapy.

Signs and symptoms of SAD may include:
Feeling depressed most of the day, nearly every day
Losing interest in activities you once enjoyed
Having low energy
Having problems with sleeping
Experiencing changes in your appetite or weight
Feeling sluggish or agitated
Having difficulty concentrating
Feeling hopeless, worthless or guilty
Having frequent thoughts of death or suicide.

Seasonal affective disorder is diagnosed more often in women than in men. And SAD occurs more frequently in younger adults than in older adults.

Factors that may increase your risk of seasonal affective disorder include:
Family history. People with SAD may be more likely to have blood relatives with SAD or another form of depression.
Having major depression or bipolar disorder. Symptoms of depression may worsen seasonally if you have one of these conditions.
Living far from the equator. SAD appears to be more common among people who live far north or south of the equator. This may be due to decreased sunlight during the winter and longer days during the summer months.

Azathioprine therapy can cause acute myelosuppression. Toxicity is in part caused by the incorporation of azathioprine-derived 6-thioguanine nucleotides (6-TGN) into deoxyribonucleic acid (DNA). The enzyme thiopurine methyltransferase (TPMT) plays an important role in azathioprine catabolism.

Tiotropium is a specific long-acting antimuscarinic agent indicated as maintenance therapy for patients with COPD (chronic obstructive pulmonary disease).
It should be used cautiously in patients with narrow-angle glaucoma, prostatic hyperplasia or bladder neck obstruction.
The most frequently encountered adverse effects of tiotropium include pharyngitis, bronchitis, sinusitis, dry mouth, cough, and headaches. Paradoxical bronchospasm may also occur as a rare side-effect.
Dry mouth occurs in up to 14% of patients taking tiotropium, in keeping with its anticholinergic profile.
Rarer side-effects include tachycardia, blurred vision, urinary retention, and constipation.

V/Q scanning carries a slightly increased risk of childhood cancer compared with CTPA – 1/280,000 versus less than 1/1,000,000 – but carries a lower risk of maternal breast cancer. The rest of the options are true.

The patient has hyperthyroidism and its most common cause is Grave’s Disease.
Grave’s Disease is an autoimmune disease due to circulating autoantibodies known as TSH receptor stimulating autoantibodies or Thyroid-stimulating immunoglobulins (TSIs) that bind to and activate thyrotropin receptors, causing the thyroid gland to grow and the thyroid follicles to increase the synthesis of thyroid hormone.

Anti–Mi-2 antibodies are highly specific for dermatomyositis, but sensitivity is low; only 25% of patients with dermatomyositis demonstrate these antibodies. A positive antinuclear antibody (ANA) finding is common in patients with dermatomyositis, but is not necessary for diagnosis. Anti-Jo-1 antibodies are mostly associated with polymyositis. Anti Scl-70 antibodies and anti centromere antibodies are most commonly found in systemic scleroderma.

To differentiate VT from SVT with aberrant conduction the following electrocardiographic features should be looked for:

Evidence of preceding atrial activity for SVT. Oesophageal leads are helpful if P waves are hidden in the QRS complex.
QRS duration more than 140 ms for VT.
QRS morphology: Features of QRS morphology that favour SVT are RBBB or triphasic patterns like rSR in V1 and qRS in V6. Monophasic pattern like R or qR in V1 and rS or QS in V6 or multiple morphology QRS complexes favour VT.
AV dissociation for VT.

Venesection should be done (essentially blood-letting) to decrease the too-high ferratin level. IV Desterrioxamine would have the opposite effect. ASA does not have to do with ferritin. You do not just watch this and recheck. And you do not want to make the patient anaemic.

The patient has small cell lung cancer presented by paraneoplastic syndrome; Ectopic ACTH secretion.

Small cell lung cancer (SCLC), previously known as oat cell carcinoma is a neuroendocrine carcinoma that exhibits aggressive behaviour, rapid growth, early spread to distant sites, exquisite sensitivity to chemotherapy and radiation, and a frequent association with distinct paraneoplastic syndromes.
Common presenting signs and symptoms of the disease, which very often occur in advanced-stage disease, include the following:
– Shortness of breath
– Cough
– Bone pain
– Weight loss
– Fatigue
– Neurologic dysfunction
Most patients with this disease present with a short duration of symptoms, usually only 8-12 weeks before presentation. The clinical manifestations of SCLC can result from local tumour growth, intrathoracic spread, distant spread, and/or paraneoplastic syndromes.
SIADH is present in 15% of the patients and Ectopic secretion of ACTH is present in 2-5% of the patients leading to ectopic Cushing’s syndrome.

Sarin acts by inhibiting acetylcholinesterase.

Sarin gas is a highly toxic synthetic organophosphorus compound which causes inhibition of the enzyme acetylcholinesterase
Sarin gas is a highly toxic synthetic organophosphorus compound which causes inhibition of the enzyme acetylcholinesterase. This results in high levels of acetylcholine (ACh).

The effects of excessive ACh can be remembered by the mnemonic DUMBELLS:
Diarrhoea
Urination
Miosis/muscle weakness
Bronchorrhea/Bradycardia
Emesis
Lacrimation
Salivation/sweating

Organophosphate insecticide poisoning:
One of the effects of organophosphate poisoning is inhibition of acetylcholinesterase
Features can be predicted by the accumulation of acetylcholine (mnemonic = SLUD)
Salivation
Lacrimation
Urination
Defecation/diarrhoea
cardiovascular: hypotension, bradycardia
miosis, muscle fasciculation.

Organophosphate poisoning is treated with the anti-muscarinic atropine.

Renal osteodystrophy is a metabolic bone disease often affecting long-term dialysis patients. The kidneys are no longer able to maintain the calcium levels in the blood, thus the PTH increases as the body attempts to raise blood calcium levels. Osteomalacia in these cases is most likely caused by the diminished activity of renal 1-a-hydroxylase that is important for hydroxylation of Calciferol to calcitriol (Vitamin D). This bioactive form of Vitamin D is responsible for increasing intestinal absorption of calcium.

Infections of the superficial skin around the eyes are called periorbital, or preseptal, cellulitis. It is predominantly a paediatric disease. Erysipelas is a bacterial skin infection involving the upper dermis which extends into the superficial cutaneous lymphatics. Sinusitis is in sinuses. Orbital infections and conjunctivitis are within the eye.

Uhthoff’s phenomenon is worsening of vision following a rise in body temperature.
Lhermitte’s sign describes paraesthesia in the limbs on neck flexion.
Oppenheim’s sign is seen when scratching of the inner side of leg leads to extension of the toes. It is a sign of cerebral irritation and is not related to multiple sclerosis.
Werdnig-Hoffman’s disease is also known as spinal muscular atrophy.

All the clinical features are suggestive of tricuspid regurgitation. The pansystolic murmur of mitral regurgitation is best heard at the apex.

Among the given options the most appropriate management in this patient would be ethanol and haemodialysis.

Ethanol competes with ethylene glycol for alcohol dehydrogenase and thus, helps manage a patient with ethylene glycol toxicity.

Ethylene glycol is a type of alcohol used as a coolant or antifreeze
Features of toxicity are divided into 3 stages:
Stage 1: (30 min to 12 hours after exposure) Symptoms similar to alcohol intoxication: confusion, slurred speech, dizziness (CNS depression)
Stage 2: (12 – 48 hours after exposure) Metabolic acidosis with a high anion gap and high osmolar gap. Also tachycardia, hypertension
Stage 3: (24 – 72 hours after exposure) Acute renal failure

Management has changed in recent times:
Fomepizole, an inhibitor of alcohol dehydrogenase, is now used first-line in preference to ethanol.
Ethanol has been used for many years works by competing with ethylene glycol for the enzyme alcohol dehydrogenase this limits the formation of toxic metabolites (e.g. glycolaldehyde and glycolic acid) which are responsible for the hemodynamic/metabolic features of poisoning.
Haemodialysis has a role in refractory cases.

Chicken pox in adults may manifest with acute encephalitis, causing the confusional syndrome known as delirium. Blisters on the trunk favour the diagnosis. The trip to Italy however seems unimportant since the incubation period of chicken pox is 10 to 21 days.

The main symptom of dermatomyositis include skin rash and symmetric proximal muscle weakness (in over 90% of patients) which may be accompanied by pain and tenderness. It occurs more commonly in females. Skin findings include:
Gottron’s sign – an erythematous, scaly eruption occurring in symmetric fashion over the MCP and interphalangeal joints
Heliotrope or lilac rash – a violaceous eruption on the upper eyelids and in rare cases on the lower eyelids as well, often with itching and swelling
Shawl (or V-) sign is a diffuse, flat, erythematous lesion over the back and shoulders or in a V over the posterior neck and back or neck and upper chest, which worsens with UV light.
Erythroderma is a flat, erythematous lesion similar to the shawl sign but located in other areas, such as the malar region and the forehead.
Periungual telangiectasias and erythema occur.

The prompt is suggestive of celiac disease as an aetiology. The antibody that is used primarily to suggest this diagnosis is anti-tissue transglutaminase antibody. You can also check anti-gliadin and anti-endomyseal antibodies, although anti-TTG antibodies are now the preferred test. To get an official diagnosis you must have a tissue diagnosis (biopsy). Anti-smooth muscle antibodies would be seen in autoimmune hepatitis. Anti-thyroid antibodies are not at all related to this, and are associated with thyroid. Anti-nuclear antibodies are non-specific.

The principal mechanism by which strontium inhibits osteoclast activity is by enhancing the secretion of osteoprotegerin (OPG) and by reducing the expression of the receptor activator of nuclear factor κB ligand (RANKL) in osteoblasts.

Osteoporosis is defined as low bone mineral density caused by altered bone microstructure ultimately predisposing patients to low-impact, fragility fractures.

Management:
Vitamin D and calcium supplementation should be offered to all women unless the clinician is confident they have adequate calcium intake and are vitamin D replete
Alendronate is the first-line treatment. Around 25% of patients cannot tolerate alendronate, usually due to upper gastrointestinal problems. These patients should be offered risedronate or etidronate.
Strontium ranelate and raloxifene are recommended if patients cannot tolerate bisphosphonates.
Other medications that are useful in the treatment of osteoporosis are denosumab, teriparatide, raloxifene, etc.

The patient most likely suffers from antiphospholipid syndrome. The clinical criteria consist of vascular thrombosis and pregnancy morbidity. Vascular thrombosis is defined as one or more clinical episodes of arterial, venous, or small-vessel thrombosis in any tissue or organ confirmed by findings from imaging studies, Doppler studies, or histopathology. ASD, VSDs would cause paradoxical emboli and stroke, however the recurrent pregnancy loss in this case is strongly suggestive of antiphospholipid syndrome. The ECG would be normal in most cases associated with anti phospholipid syndrome.

Immune thrombocytopenic purpura (ITP) refers to thrombocytopaenia occurring in the absence of toxic exposure or other diseases associated with low platelets and involves IgG-type antibodies. It is characterised by normal or increased marrow megakaryocytes, shortened platelet survival, and the absence of splenomegaly. Autoimmune haemolytic anaemia (AIHA) occurs commonly in association with ITP. Leukemic transformation, however, does not occur in ITP.

In neonatal ITP, IgG antibodies are passively transferred across the placenta. The infant platelet count may be normal at birth but decreases within 12–24 hours. It is rarely severe enough to induce bleeding diathesis in the infant.

The duration of these cell cycle phases varies considerably in different kinds of cells. For a typical rapidly proliferating human cell with a total cycle time of 24 hours, the G1 phase might last about 11 hours, S phase about 8 hours, G2 about 4 hours, and M about 1 hour. The proliferation of most animal cells is similarly regulated in the G1 phase of the cell cycle. In particular, a decision point in late G1, called the restriction point in animal cells, is the point at which the cell becomes committed to the cell cycle and after which extracellular proliferation stimulants are no longer required.. Although the proliferation of most cells is regulated primarily in G1, some cell cycles are instead controlled principally in G2.

The statement that fits the characteristics of doxapram is, epilepsy is a contraindication for doxapram use. Concurrent use with theophylline may increase agitation not relaxation.

Doxapram is a central respiratory stimulant. In clinical practice, doxapram is usually used for patients who have an acute exacerbation of chronic obstructive pulmonary disease (COPD) who are unsuitable for admission to the intensive therapy unit for ventilatory support. Doxapram infusion may buy an extra 24 h to allow for recovery.

Contraindications include: ischaemic heart disease, epilepsy, cerebral oedema, acute stroke, asthma, hypertension, hyperthyroidism, and pheochromocytoma.
The infusion may worsen agitation and dyspnoea and lead to hypertension, nausea, vomiting and urinary retention.

Drug interactions:
Concomitant administration of doxapram and aminophylline (theophylline) can cause increased skeletal muscle activity, agitation, and hyperactivity.

Excessive sweating points towards a morphine overdose.

Morphine is considered the classic opioid analgesic with which other painkillers are compared. Like other medications in this class, morphine has an affinity for delta, kappa, and mu-opioid receptors.
Most commonly used in pain management, morphine provides major relief to patients afflicted with pain.

Among the more common adverse effects of morphine use is constipation. Other side effects include nausea, vomiting, drowsiness, and confusion. Psychological and physical dependence may occur.

Other side effects include bronchospasm, angioedema, urinary retention, ureteric or biliary spasm, dry mouth, sweating, rash, facial flushing, vertigo, tachycardia, bradycardia, palpitations, orthostatic hypotension, hypothermia, restlessness, mood change, hallucinations, seizures (adults and children) and miosis, headache and allergic reactions (including anaphylaxis) and decreased libido or potency.

Raised intracranial pressure occurs in some patients. Muscle rigidity may occur with high doses. Elevated liver enzymes may occur due to biliary sphincter constriction. Large doses can lead to respiratory depression, circulatory failure, and coma.

Treatment of opioid overdose:
Initial treatment of overdose begins with supportive care.
Naloxone is a pure competitive antagonist of opiate receptors and has no agonistic activity. The drug is relatively safe and can be administered intravenous, intramuscular, subcutaneous or via the endotracheal tube.
Alternatively, nalmefene and naltrexone maybe considered.

Triamterene is a potassium-sparing diuretic that can cause hyperkalaemia, therefore, it was stopped in this patient. With all other lab results returning normal values and a normal ECG, management will simply require repeating the U & E after one week since the Triamterene has already be stopped.

The water deprivation test (i.e., the Miller-Moses test), is a semiquantitative test to ensure adequate dehydration and maximal stimulation of ADH for diagnosis. It is typically performed in patients with more chronic forms of Diabetes Insipidus (DI). The extent of deprivation is usually limited by the patient’s thirst or by any significant drop in blood pressure or related clinical manifestation of dehydration.

In healthy individuals, water deprivation leads to a urinary osmolality that is 2-4 times greater than plasma osmolality. Additionally, in normal, healthy subjects, administration of ADH produces an increase of less than 9% in urinary osmolality. The time required to achieve maximal urinary concentration ranges from 4-18 hours.

In central and nephrogenic DI, urinary osmolality will be less than 300 mOsm/kg after water deprivation. After the administration of ADH, the osmolality will rise to more than 750 mOsm/kg in central DI but will not rise at all in nephrogenic DI. In primary polydipsia, urinary osmolality will be above 750 mOsm/kg after water deprivation.
A urinary osmolality that is 300-750 mOsm/kg after water deprivation and remains below 750 mOsm/kg after administration of ADH may be seen in partial central DI, partial nephrogenic DI, and primary polydipsia.

The two statements that fit the characteristics of doxapram are, epilepsy is a contraindication for doxapram use and concurrent use with theophylline may increase agitation.

Doxapram is a central respiratory stimulant. In clinical practice, doxapram is usually used for patients who have an acute exacerbation of chronic obstructive pulmonary disease (COPD) who are unsuitable for admission to the intensive therapy unit for ventilatory support. Doxapram infusion may buy an extra 24 h to allow for recovery.

Contraindications include: ischaemic heart disease, epilepsy, cerebral oedema, acute stroke, asthma, hypertension, hyperthyroidism, and pheochromocytoma.
The infusion may worsen agitation and dyspnoea and lead to hypertension, nausea, vomiting and urinary retention.

Drug interactions:
Concomitant administration of doxapram and aminophylline (theophylline) can cause increased skeletal muscle activity, agitation, and hyperactivity.

Absolute risk reduction (ARR) – also called risk difference (RD) – is the most useful way of presenting research results to help your decision-making. Absolute risk reduction = (Control event rate) – (Experimental event rate) = 0.15 = 15%

Primary hyperaldosteronism, also known as Conn’s Syndrome, is one of the most common causes of secondary hypertension (HTN).
The common clinical scenarios in which the possibility of primary hyperaldosteronism should be considered include the following:
– Patients with spontaneous or unprovoked hypokalaemia, especially if the patient is also hypertensive
– Patients who develop severe and/or persistent hypokalaemia in the setting of low to moderate doses of potassium-wasting diuretics
– Patients with treatment-refractory/-resistant hypertension (HTN)
Patients with severe hypokalaemia report fatigue, muscle weakness, cramping, headaches, and palpitations. They can also have polydipsia and polyuria from hypokalaemia-induced nephrogenic diabetes insipidus. Long-standing HTN may lead to cardiac, retinal, renal, and neurologic problems, with all the associated symptoms and signs.