Psittacosis is a type of infection that can be transmitted from animals to humans, known as a zoonotic infection. It is caused by a bacterium called Chlamydia psittaci. This infection is most commonly seen in people who own domestic birds, but it can also affect those who work in pet shops or zoos.

The typical presentation of psittacosis includes symptoms similar to those of pneumonia that is acquired within the community. People may experience flu-like symptoms along with severe headaches and sensitivity to light. In about two-thirds of patients, an enlargement of the spleen, known as splenomegaly, can be observed.

Infected individuals often develop a reddish rash with flat spots on their face, known as Horder’s spots. Additionally, they may experience skin conditions such as erythema nodosum or erythema multiforme.

The recommended treatment for psittacosis is a course of tetracycline or doxycycline, which should be taken for a period of 2-3 weeks.

Suxamethonium, also called succinylcholine, is a type of drug used to block neuromuscular transmission. It acts as an agonist by binding to acetylcholine receptors at the neuromuscular junction. Unlike acetylcholine, suxamethonium is not broken down by acetylcholinesterase, which means it stays bound to the receptors for a longer time, leading to prolonged inhibition of neuromuscular transmission. Eventually, suxamethonium is metabolized by plasma cholinesterase.

Further Reading:

Rapid sequence induction (RSI) is a method used to place an endotracheal tube (ETT) in the trachea while minimizing the risk of aspiration. It involves inducing loss of consciousness while applying cricoid pressure, followed by intubation without face mask ventilation. The steps of RSI can be remembered using the 7 P’s: preparation, pre-oxygenation, pre-treatment, paralysis and induction, protection and positioning, placement with proof, and post-intubation management.

Preparation involves preparing the patient, equipment, team, and anticipating any difficulties that may arise during the procedure. Pre-oxygenation is important to ensure the patient has an adequate oxygen reserve and prolongs the time before desaturation. This is typically done by breathing 100% oxygen for 3 minutes. Pre-treatment involves administering drugs to counter expected side effects of the procedure and anesthesia agents used.

Paralysis and induction involve administering a rapid-acting induction agent followed by a neuromuscular blocking agent. Commonly used induction agents include propofol, ketamine, thiopentone, and etomidate. The neuromuscular blocking agents can be depolarizing (such as suxamethonium) or non-depolarizing (such as rocuronium). Depolarizing agents bind to acetylcholine receptors and generate an action potential, while non-depolarizing agents act as competitive antagonists.

Protection and positioning involve applying cricoid pressure to prevent regurgitation of gastric contents and positioning the patient’s neck appropriately. Tube placement is confirmed by visualizing the tube passing between the vocal cords, auscultation of the chest and stomach, end-tidal CO2 measurement, and visualizing misting of the tube. Post-intubation management includes standard care such as monitoring ECG, SpO2, NIBP, capnography, and maintaining sedation and neuromuscular blockade.

Overall, RSI is a technique used to quickly and safely secure the airway in patients who may be at risk of aspiration. It involves a series of steps to ensure proper preparation, oxygenation, drug administration, and tube placement. Monitoring and post-intubation care are also important aspects of RSI.

Lithium is a commonly prescribed medication for bipolar disorder, as it helps stabilize mood. The recommended therapeutic range for lithium levels is typically between 0.4 and 0.8 mmol/l, although this range may vary depending on the laboratory. For maintenance therapy and treatment in older individuals, the lower end of the range is usually targeted. Toxic effects of lithium are typically observed when levels exceed 1.5 mmol/l. It is important to monitor lithium levels one week after starting therapy and after any dosage adjustments.

One potential side effect of lithium is the development of nephrogenic diabetes insipidus, a condition that affects the kidneys’ ability to concentrate urine. However, lithium does not cause diabetes mellitus. Another known side effect is hypothyroidism, which is a decrease in thyroid hormone production, but it does not lead to hyperthyroidism, an overactive thyroid.

Signs of lithium toxicity include nausea, vomiting, diarrhea, tremors, ataxia (loss of coordination), confusion, increased muscle tone, clonus (repetitive, involuntary muscle contractions), nephrogenic diabetes insipidus, convulsions, coma, and renal failure. It is crucial to be aware of these symptoms and seek medical attention if they occur.

Acute kidney injury (AKI), previously known as acute renal failure, is a sudden decline in kidney function. This results in the accumulation of urea and other waste products in the body and disrupts the balance of fluids and electrolytes. AKI can occur in individuals with previously normal kidney function or those with pre-existing kidney disease, known as acute-on-chronic kidney disease. It is a relatively common condition, with approximately 15% of adults admitted to hospitals in the UK developing AKI.

The causes of AKI can be categorized into pre-renal, intrinsic renal, and post-renal factors. The majority of AKI cases that develop outside of healthcare settings are due to pre-renal causes, accounting for 90% of cases. These causes typically involve low blood pressure associated with conditions like sepsis and fluid depletion. Medications, particularly ACE inhibitors and NSAIDs, are also frequently implicated.

Pre-renal:
– Volume depletion (e.g., severe bleeding, excessive vomiting or diarrhea, burns)
– Oedematous states (e.g., heart failure, liver cirrhosis, nephrotic syndrome)
– Low blood pressure (e.g., cardiogenic shock, sepsis, anaphylaxis)
– Cardiovascular conditions (e.g., severe heart failure, arrhythmias)
– Renal hypoperfusion: NSAIDs, COX-2 inhibitors, ACE inhibitors or ARBs, abdominal aortic aneurysm
– Renal artery stenosis
– Hepatorenal syndrome

Intrinsic renal:
– Glomerular diseases (e.g., glomerulonephritis, thrombosis, hemolytic-uremic syndrome)
– Tubular injury: acute tubular necrosis (ATN) following prolonged lack of blood supply
– Acute interstitial nephritis due to drugs (e.g., NSAIDs), infection, or autoimmune diseases
– Vascular diseases (e.g., vasculitis, polyarteritis nodosa, thrombotic microangiopathy, cholesterol emboli, renal vein thrombosis, malignant hypertension)
– Eclampsia

Post-renal:
– Kidney stones
– Blood clot
– Papillary necrosis
– Urethral stricture
– Prostatic hypertrophy or malignancy
– Bladder tumor
– Radiation fibrosis
– Pelvic malignancy
– Retroperitoneal

Cellulitis is a common cause of swelling in one leg. It is characterized by red, hot, tender, and swollen skin, usually affecting the shin on one side. Other symptoms may include fever, fatigue, and chills. It is important to consider deep vein thrombosis (DVT) as a possible alternative diagnosis, as it can be associated with cellulitis or vice versa. Unlike cellulitis, DVT does not typically cause fever and affects the entire limb below the blood clot, resulting in swelling in the calf, ankle, and foot. Necrotizing fasciitis is a rare condition. Gout primarily affects the joints of the foot, particularly the first metatarsophalangeal joint. Erythema migrans usually produces a distinct target-shaped rash.

Further Reading:

Cellulitis is an inflammation of the skin and subcutaneous tissues caused by an infection, usually by Streptococcus pyogenes or Staphylococcus aureus. It commonly occurs on the shins and is characterized by symptoms such as erythema, pain, swelling, and heat. In some cases, there may also be systemic symptoms like fever and malaise.

The NICE Clinical Knowledge Summaries recommend using the Eron classification to determine the appropriate management of cellulitis. Class I cellulitis refers to cases without signs of systemic toxicity or uncontrolled comorbidities. Class II cellulitis involves either systemic illness or the presence of a co-morbidity that may complicate or delay the resolution of the infection. Class III cellulitis is characterized by significant systemic upset or limb-threatening infection due to vascular compromise. Class IV cellulitis involves sepsis syndrome or a severe life-threatening infection like necrotizing fasciitis.

According to the guidelines, patients with Eron Class III or Class IV cellulitis should be admitted for intravenous antibiotics. This also applies to patients with severe or rapidly deteriorating cellulitis, very young or frail individuals, immunocompromised patients, those with significant lymphedema, and those with facial or periorbital cellulitis (unless very mild). Patients with Eron Class II cellulitis may not require admission if the necessary facilities and expertise are available in the community to administer intravenous antibiotics and monitor the patient.

The recommended first-line treatment for mild to moderate cellulitis is flucloxacillin. For patients allergic to penicillin, clarithromycin or clindamycin is recommended. In cases where patients have failed to respond to flucloxacillin, local protocols may suggest the use of oral clindamycin. Severe cellulitis should be treated with intravenous benzylpenicillin and flucloxacillin.

Overall, the management of cellulitis depends on the severity of the infection and the presence of any systemic symptoms or complications. Prompt treatment with appropriate antibiotics is crucial to prevent further complications and promote healing.

The orbicularis oculi muscle encircles the eye socket and extends into the eyelid. It is composed of two parts: the orbital part, which forcefully closes the eye, and the palpebral part, which gently closes the eye. The innervation of the orbicularis oculi muscle is provided by the facial nerve. In the event of facial nerve damage, the orbicularis oculi muscle loses its functionality. As the sole muscle responsible for closing the eyelids, this can have significant clinical implications. The inability to shut the eye can lead to dryness of the cornea and the development of exposure keratitis. While mild cases can be managed with regular use of eye drops, severe cases may require surgical closure of the eye.

The primary way hepatitis A is transmitted is through the ingestion of fecal matter containing the virus. On the other hand, all the other organisms mentioned in this question are typically transmitted through sexual contact.

Bullous pemphigoid (BP) is a chronic autoimmune disorder that affects the skin, causing blistering. It occurs when the immune system mistakenly attacks the basement membrane of the epidermis. This attack is carried out by immunoglobulins (IgG and sometimes IgE) and activated T lymphocytes. The autoantibodies bind to proteins and release cytokines, leading to complement activation, neutrophil recruitment, and the release of enzymes that destroy the hemidesmosomes. As a result, subepidermal blisters form.

Pemphigus, on the other hand, is a group of autoimmune disorders characterized by blistering of the skin and mucosal surfaces. The most common type, pemphigus vulgaris (PV), accounts for about 70% of cases worldwide. PV is also autoimmune in nature, with autoantibodies targeting cell surface antigens on keratinocytes (desmogleins 1 and 3). This leads to a loss of adhesion between cells and their separation.

Here is a comparison of the key differences between pemphigus vulgaris and bullous pemphigoid:

Pemphigus vulgaris:
– Age: Middle-aged people (average age 50)
– Oral involvement: Common
– Blister type: Large, flaccid, and painful
– Blister content: Fluid-filled, often haemorrhagic
– Areas commonly affected: Initially face and scalp, then spread to the chest and back
– Nikolsky sign: Usually positive
– Pruritus: Rare
– Skin biopsy: Intra-epidermal deposition of IgG between cells throughout the epidermis

Bullous pemphigoid:
– Age: Elderly people (average age 80)
– Oral involvement: Rare
– Blister type: Large and tense
– Blister content: Fluid-filled
– Areas commonly affected: Upper arms, thighs, and skin flexures
– Nikolsky sign: Usually negative
– Pruritus: Common
– Skin biopsy: A band of IgG and/or C3 at the dermo-epidermal junction

The following provides a summary of common causes for different acid-base disorders.

Respiratory alkalosis can be caused by hyperventilation, such as during periods of anxiety. It can also be a result of conditions like pulmonary embolism, CNS disorders (such as stroke or encephalitis), altitude, pregnancy, or the early stages of aspirin overdose.

Respiratory acidosis, on the other hand, is often associated with chronic obstructive pulmonary disease (COPD), life-threatening asthma, pulmonary edema, sedative drug overdose (such as opiates or benzodiazepines), neuromuscular disease, obesity, or other respiratory conditions.

Metabolic alkalosis can occur due to vomiting, potassium depletion (often caused by diuretic usage), Cushing’s syndrome, or Conn’s syndrome.

Metabolic acidosis with a raised anion gap can be caused by lactic acidosis (such as in cases of hypoxemia, shock, sepsis, or infarction), ketoacidosis (such as in diabetes, starvation, or alcohol excess), renal failure, or poisoning (such as in late stages of aspirin overdose, methanol or ethylene glycol ingestion).

Lastly, metabolic acidosis with a normal anion gap can be a result of conditions like diarrhea, ammonium chloride ingestion, or adrenal insufficiency.

An overdose of Amitriptyline can lead to the development of an anticholinergic toxidrome. This toxidrome is characterized by various symptoms, which can be remembered using the phrase ‘mad as a hatter, hot as hell, red as a beat, dry as a bone, and blind as a bat’. Some of these symptoms include a dry mouth and an elevated body temperature.

Further Reading:

Tricyclic antidepressant (TCA) overdose is a common occurrence in emergency departments, with drugs like amitriptyline and dosulepin being particularly dangerous. TCAs work by inhibiting the reuptake of norepinephrine and serotonin in the central nervous system. In cases of toxicity, TCAs block various receptors, including alpha-adrenergic, histaminic, muscarinic, and serotonin receptors. This can lead to symptoms such as hypotension, altered mental state, signs of anticholinergic toxicity, and serotonin receptor effects.

TCAs primarily cause cardiac toxicity by blocking sodium and potassium channels. This can result in a slowing of the action potential, prolongation of the QRS complex, and bradycardia. However, the blockade of muscarinic receptors also leads to tachycardia in TCA overdose. QT prolongation and Torsades de Pointes can occur due to potassium channel blockade. TCAs can also have a toxic effect on the myocardium, causing decreased cardiac contractility and hypotension.

Early symptoms of TCA overdose are related to their anticholinergic properties and may include dry mouth, pyrexia, dilated pupils, agitation, sinus tachycardia, blurred vision, flushed skin, tremor, and confusion. Severe poisoning can lead to arrhythmias, seizures, metabolic acidosis, and coma. ECG changes commonly seen in TCA overdose include sinus tachycardia, widening of the QRS complex, prolongation of the QT interval, and an R/S ratio >0.7 in lead aVR.

Management of TCA overdose involves ensuring a patent airway, administering activated charcoal if ingestion occurred within 1 hour and the airway is intact, and considering gastric lavage for life-threatening cases within 1 hour of ingestion. Serial ECGs and blood gas analysis are important for monitoring. Intravenous fluids and correction of hypoxia are the first-line therapies. IV sodium bicarbonate is used to treat haemodynamic instability caused by TCA overdose, and benzodiazepines are the treatment of choice for seizure control. Other treatments that may be considered include glucagon, magnesium sulfate, and intravenous lipid emulsion.

There are certain things to avoid in TCA overdose, such as anti-arrhythmics like quinidine and flecainide, as they can prolonged depolarization.