The musculocutaneous nerve is relatively protected in the axilla, hence injury to it is uncommon. A stab wound in the axilla is the most prevalent source of damage. Because of the activities of the pectoralis major and deltoid, the brachioradialis, and the supinator muscles, arm flexion and forearm flexion and supination are diminished but not completely lost. Over the lateral part of the forearm, there is a lack of sensation.

IV adrenaline 1 mg (10 mL of 1:10,000 solution) should be given after 3 shocks and every 3 – 5 minutes/after alternate shocks thereafter.

Extensor carpi ulnaris is a fusiform muscle in the posterior forearm. It spans between the elbow and base of the little finger. This muscle belongs to the superficial forearm extensor group, along with anconaeus, brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum and extensor digiti minimi muscles.Like all the muscles of this compartment, extensor carpi ulnaris works as an extensor of the wrist. Moreover, due to its specific course, this muscle also acts to adduct the hand.Extensor carpi ulnaris is innervated by the posterior interosseous nerve (C7, C8), a branch of the deep division of the radial nerve. The radial nerve stems from the posterior cord of the brachial plexus.Blood supply to the extensor carpi ulnaris muscle is provided by branches of the radial recurrent and posterior interosseous arteries, which stem from the radial and ulnar arteries, respectively.

Megaloblastic anemia results from inhibition of DNA synthesis during red blood cell production. When DNA synthesis is impaired, the cell cycle cannot progress from the growth stage to the mitosis stage. This leads to continuing cell growth without division, which presents as macrocytosis, with an increase in mean corpuscular volume (MCV). The defect in red cell DNA synthesis is most often due to hypovitaminosis, specifically vitamin B12 deficiency or folate deficiency.Folate is an essential vitamin found in most foods, especially liver, green vegetables and yeast. The normal daily diet contains 200 – 250 μg, of which about 50% is absorbed. Daily adult requirements are about 100 μg. Absorption of folate is principally from the duodenum and jejunum. Stores of folate are normally only adequate for 4 months and so features of deficiency may be apparent after this time.

The liver produces bile on a constant basis, which is then stored and concentrated in the gallbladder. In a 24-hour period, around 400 to 800 mL of bile is generated.Bile is involved in the following processes:Fats are broken down into fatty acids.Waste products are eliminated.Cholesterol homeostasis is the balance of cholesterol in the body.The enteric hormones cholecystokinin and secretin are primarily responsible for bile secretion. When chyme from an unprocessed meal enters the small intestine, they are released, and they play the following function in bile secretion and flow:Cholecystokinin promotes gallbladder and common bile duct contractions, allowing bile to reach the intestine.Secretin enhances the secretion of bicarbonate and water by biliary duct cells, increasing the amount of bile and its flow into the gut.Bile acids have a hydrophobic and hydrophilic area, making them amphipathic. Bile acids’ amphipathic nature allows them to perform the following crucial functions:Emulsification of lipid aggregates increases the surface area of fat and makes it easier for lipases to digest it.Lipid solubilization and transport: solubilizes lipids by creating micelles, which are lipid clumps that float in water.

Normal saline (sodium chloride 0.9%) contains:Na+150 mmol/LCl-150 mmol/L

Flow through a tube is dependent upon:The pressure difference across the ends of the tube (P1– P2)The resistance to flow provided by the tube (R)This is Darcy’s law, which is analogous to Ohm’s law in electronics:Flow = (P1– P2) / RResistance in the tube is defined by Poiseuille’s law, which is determined by the diameter of the tube and the viscosity of the fluid. Poiseuille’s law is as follows:Resistance = (8VL) / (πR4)Where:V = The viscosity of the fluidL = The length of the tubeR = The radius of the tubeTherefore, in simple terms, resistance is directly proportional to the viscosity of the fluid and the length of the tube and inversely proportional to the radius of the tube. Of these three factors, the most important quantitatively and physiologically is vessel radius.It can be seen that small changes in the radius can have a dramatic effect on the flow of the fluid. For example, the constriction of an artery by 20% will decrease the flow by approximately 60%.Another important and frequently quoted example of this inverse relationship is that of the radius of an intravenous cannula. Doubling the diameter of a cannula increases the flow rate by 16-fold (r4). This is the reason the diameter of an intravenous cannula in resuscitation scenarios is so important.*Please note that knowledge of the detail of Poiseuille’s law is not a requirement of the RCEM Basic Sciences Curriculum.

Aminoglycosides cross the placenta and are linked to poisoning of the 8th cranial nerve in the foetus, as well as permanent bilateral deafness.

Each motor unit contracts in an all or nothing fashion, i.e. if a motor unit is excited, it will stimulate all of its muscle fibres to contract. The force of contraction of a muscle is controlled by varying the motor unit recruitment (spatial summation), and by varying the firing rate of the motor units (temporal summation). During a gradual increase in contraction of a muscle, the first units start to discharge and increase their firing rate, and, as the force needs to increase, new units are recruited and, in turn, also increase their firing rate. For most motor units, the firing rate for a steady contraction is between 5 and 8 Hz. Because the unitary firing rates for each motor unit are different and not synchronised, the overall effect is a smooth force profile from the muscle. Increasing the firing rate of motor units is temporal summation where the tension developed by the first action potential has not completely decayed when the second action potential and twitch is grafted onto the first and so on. If the muscle fibres are stimulated repeatedly at a faster frequency, a sustained contraction results where it is not possible to detect individual twitches. This is called tetanus.

Klebsiellais a genus of non-motile,Gram-negative, rod-shaped bacteriawith a prominent polysaccharide-based capsule. They are routinely found in the nose, mouth and gastrointestinal tract as normal flora, however, they can also behave as opportunistic pathogens.Infections with Klebsiella spp. areusually nosocomial. They are an important cause of ventilator-associated pneumonia (VAP), urinary tract infection, wound infection and bacteraemia. Outbreaks of infections with Klebsiellaspp. in high-dependency units have been described and are associated with septicaemia and high mortality rates. Length of hospital stay and performance of invasive procedures are risk factors forKlebsiellainfections.Primary pneumonia withKlebsiella pneumoniaeis a rare,severe, community-acquired infection associated with a poor outcome.Klebsiella rhinoscleromatis causes a progressive granulomatous infection of the nasal passages and surrounding mucous membranes. This infection is mainly seen in the tropics.Klebsiella ozanae is a recognised cause of chronic bronchiectasis.Klebsiella organisms are resistant to multiple antibiotics including penicillins. This is thought to be a plasmid-mediated property. Agents with high intrinsic activity againstKlebsiellapneumoniaeshould be selected for severely ill patients. Examples of such agents include third-generation cephalosporins (e.g cefotaxime), carbapenems (e.g. imipenem), aminoglycosides (e.g. gentamicin), and quinolones (e.g. ciprofloxacin). These agents may be used as monotherapy or combination therapy. Aztreonam may be used in patients who are allergic to beta-lactam antibiotics.Species with ESBLs (Extended spectrum beta-lactamase) are resistant to penicillins and also cephalosporins such as cefotaxime and ceftriaxone.

Basophils are only occasionally seen in normal peripheral blood comprising < 1% of circulating white cells. However, they are the largest type of granulocyte. They have many dark cytoplasmic granules which overlie the nucleus and contain heparin and histamine. They have immunoglobulin E (IgE) attachment sites and their degranulation is associated with histamine release. Basophils are very similar in both appearance and function to mast cells.

Ciprofloxacin is recommended for use as meningococcal chemoprophylaxis in all age groups and in pregnancy, and is the most appropriate for this patient.However, rifampicin is the drug of choice for meningococcal chemoprophylaxis because it is licensed for chemoprophylaxis, but multiple doses are necessary and it is not readily available in community pharmacies. It also interacts with oral contraceptives.

Captopril is an angiotensin-converting enzyme (ACE) inhibitor, which inhibits the conversion of angiotensin I to angiotensin II.

Digoxin is excreted through the kidneys, and impaired renal function can lead to elevated digoxin levels and toxicity.The patient’s digoxin dose should be reduced in this case, and their digoxin level and electrolytes should be closely monitored.

Legionella species are ubiquitous, Gram-negative bacilli acquired primarily through inhalation. Infections caused by Legionella spp. produce a spectrum of symptoms ranging from mild upper respiratory tract infections to pneumonia. Legionella spp. are responsible for 2% to 15% of community-acquired pneumonia.Clinical manifestations of Legionella infections include febrile disease with pneumonia (legionnaires’ disease), febrile disease without pulmonary involvement (Pontiac fever), and asymptomatic infection.The mode of transmission and the number of infecting organisms in the inoculum play a role in the clinical features of the infection. In addition, host factors, such as a suppressed immune system, chronic lung disease, alcoholism, and heavy smoking, predispose individuals to legionnaires’ disease.Legionella spp. can tolerate chlorine concentrations of 3 mg/L, they resist water treatment and subsequently gain entry into and colonize human-made water supplies and distribution systems. Hot water systems, cooling towers, and evaporative condensers are major reservoirs. Other sources include cold water systems, ornamental fountains, whirlpool spas, humidifiers, respiratorytherapy equipment, and industrial process waters.

When more fluid is filtered out of the capillaries than can be returned to the circulation by the lymphatics, oedema occurs. Changes that increase capillary hydrostatic pressure or decrease plasma oncotic pressure will increase filtration. Arteriolar constriction reduces hydrostatic capillary pressure and transiently increase absorption of fluid. Dehydration increases plasma protein concentration and therefore increases plasma oncotic pressure and absorption. Capillary hydrostatic pressure and filtration are increased when there is increased venous pressure.

Anti-D is an IgG antibody that targets the antigen Rhesus D (RhD). Plasma from rhesus-negative donors who have been immunised against the anti-D-antigen is used to make anti-D immunoglobulin.Only RhD negative women are given Anti-D Ig. Women who are RhD negative do not have the RhD antigen on their RBC. If a foetus has the RhD antigen (i.e. is RhD positive) and the mother is exposed to foetal blood, she may develop antibodies to RhD that pass through the placenta and attack foetal red cells (resulting in newborn haemolytic disease). Anti-D is given to bind and neutralise foetal red cells in the maternal circulation before an immune response is triggered. In the event of a sensitising event, 500 IU Anti-D Ig should be administered intramuscularly. The following are examples of potentially sensitising events:BirthHaemorrhage during pregnancyMiscarriageEctopic pregnancyDeath within the wombAmniocentesisChorionic villus samplingTrauma to the abdomenThe sooner anti-D is given in the event of a sensitising event, the better; however, it is most effective within 72 hours, and the BNF states that it is still likely to have some benefit if given outside of this time frame.At 28 and 34 weeks, RhD negative women should receive routine antenatal prophylaxis. This is regardless of whether they have previously received Anti-D for a sensitising event during the same pregnancy.Prophylactic anti-D is not necessary before 12 weeks gestation, as confirmed by scan, in uncomplicated miscarriage (where the uterus is not instrumented), or mild, painless vaginal bleeding, as the risk of foeto-maternal haemorrhage (FMH) is negligible. In cases of therapeutic termination of pregnancy, whether by surgical or medical means, 250 IU of prophylactic anti-D immunoglobulin should be given to confirmed RhD negative women who are not known to be RhD sensitised.

Co-amoxiclav consists of amoxicillin with the beta-lactamase inhibitor clavulanic acid. Clavulanic acid itself has no significant antibacterial activity but, by inactivating beta-lactamases, it makes the combination active against beta-lactamase-producing bacteria that are resistant to amoxicillin.The most common adverse effects of co-amoxiclav include nausea, vomiting, skin rash and diarrhoea. Pseudomembranous colitis should be considered if a person develops severe diarrhoea during or after treatment with co-amoxiclav. Cholestatic jaundice can occur either during or shortly after the use of co-amoxiclav. An epidemiological study has shown that the risk of acute liver toxicity was about 6 times greater with co-amoxiclav than with amoxicillin. Cholestatic jaundice is more common in patients above the age of 65 years and in men; these reactions have only rarely been reported in children. Jaundice is usually self-limiting and very rarely fatal.

Examples of type I reactions include:Allergic rhinitisAllergic conjunctivitisAllergic asthmaSystemic anaphylaxisAngioedemaUrticariaPenicillin allergy

Angiotensin II acts to directly increase Na+reabsorption from the proximal tubule (by activating Na+/H+antiporters).

Antacids are contraindicated in hypophosphataemia. Liquid preparations are more effective than tablet preparations. Magnesium-containing antacids tend to be laxative whereas aluminium-containing antacids tend to be constipating. Antacids are best taken when symptoms occur or are expected, usually between meals and at bedtime. Antacids should preferably not be taken at the same time as other drugs since they may impair absorption.

Angiotensin-converting enzyme (ACE) inhibitors prevent angiotensin I from being converted to angiotensin II. Angiotensin II has a variety of effects:Sympathetic activity has increased.Vasoconstriction in the arteriesSecretion of VasopressinSecretion of aldosteroneThe increase in systemic blood pressure is caused by arteriolar vasoconstriction. Vasopressin stimulates water reabsorption in the kidneys as well as the thirst sensation. In the distal convoluted tubules and collecting ducts, aldosterone causes the reabsorption of sodium and water from the urine in exchange for potassium secretion. As a result, ACE inhibitors lower systemic blood pressure while also causing hyperkalaemia.Angiotensin-converting enzyme inhibitors (ACE inhibitors) are used in a variety of clinical settings, including heart failure. According to a meta-analysis, ACE inhibitors reduce death, MI, and overall admission in patients with heart failure by 28%.ACE inhibitors are also used in the following clinical settings:HypertensionChronic kidney diseaseDiabetic nephropathy Following a myocardial infarctionIn the presence of renal artery stenosis, ACE inhibitors are contraindicated because they can cause or exacerbate renal failure.The most common side effect of ACE inhibitors is a dry cough caused by increased bradykinin production. There is, however, no known link to fibrosis of the lungs.

Calcitonin is a 32 amino acid polypeptide that is primarily synthesised and released by the parafollicular cells (C-cells) of the thyroid gland in response to rising or high levels of plasma Ca2+ions. Its primary role is to reduce the plasma calcium concentration, therefore opposing the effects of parathyroid hormone.Secretion of calcitonin is stimulated by:- Increased plasma calcium concentration- Gastrin- Pentagastrin- The main actions of calcitonin are:- Inhibition of osteoclastic activity (decreasing calcium and phosphate resorption from bone)- Stimulation of osteoblastic activity- Decreases renal calcium reabsorption- Decreases renal phosphate reabsorption

The UK national census is an example of a cross-sectional study.Cross-sectional studies can be used to assess the prevalence of a condition, and support or refute inferences of cause and effect.Cross-sectional studies are observations of the frequency and characteristics of a disease in a given population at one particular point in time. Cross-sectional studies do not differentiate between cause and effect and also do not establish the sequence of events.Cross-sectional studies cannot be used to calculate the relative risk of a condition.

The purine nucleoside adenosine is used to diagnose and treat paroxysmal supraventricular tachycardia. Adenosine works by stimulating A1-adenosine receptors and opening potassium channels that are sensitive to acetylcholine. This causes the atrioventricular (AV) node’s cell membrane to become hyperpolarized, slowing conduction by inhibiting calcium channels.Patients who have had a heart transplant are extremely sensitive to the effects of adenosine and should start with a lower dose of 3 mg, then 6 mg, and finally 12 mg. Dipyridamole potentiates the effects of adenosine, so it should be used with caution in patients who are taking it.The use of adenosine is contraindicated in the following situations:AsthmaCOPD (chronic obstructive pulmonary disease)Decompensated heart failure Long QT syndromeAV block in the second or third degreeSinusitis is a condition in which the sinuses become (unless pacemaker fitted)Hypotension that is severeIt has a half-life of less than 10 seconds and acts quickly within that time frame. The actions last between 10 and 20 seconds. Because of the short half-life of the drug, any side effects are usually only temporary. These are some of them:a feeling of impending doomFlushing of the faceDyspnoeaUncomfortable chestTastes metallic

Heroin is injected into the veins and is the most commonly abused drug. Acute intoxication with opioid overuse is the most common cause of death by drug overdose. The clinical features of opioid overdose are:1. Decreased respiratory rate2. Reduced conscious level or coma3. Decreased bowel sounds4. Miotic (constricted) pupils5. Cyanosis6. Hypotension7. Seizures8. Non-cardiogenic pulmonary oedema (with IV heroin usage)The main cause of death secondary to opioid overdose is respiratory depression, which usually occurs within 1 hour of the overdose. Vomiting is also common, and aspiration can occur.Naloxone is a short-acting, specific antagonist of mu(μ)-opioid receptors. It is used to reverse the effects of opioid toxicity. It can be given by a continuous infusion if repeated doses are required and the infusion rate is adjusted according to the vital signs. Initially, the infusion rate can be set at 60% of the initial resuscitative IV dose per hour.Naloxone has a shorter duration of action (6-24 hours) than most opioids, and so close monitoring according to the respiratory rate and depth of coma with repeated injections is necessary. When repeated doses are needed in opioid addicts, naloxone administration may precipitate a withdrawal syndrome with abdominal cramps, nausea and diarrhoea, but these usually settle within 2 hours.An initial dose of 0.4 to 2 mg can be given intravenously and can be repeated at 2 to 3-minute intervals to a maximum of 10mg. If the intravenous route is inaccessible, naloxone can be administered via an IO line, subcutaneously (SQ), IM, or via the intranasal (IN) route.

Fibrinolytic drugs act as thrombolytics by activating plasminogen to form plasmin, which degrades fibrin and so breaks up thrombi.

An intention to treat (ITT) analysis is one in which all patients are included in the analysis, classified according to the group into which they were randomised, even if they were withdrawn from the study and did not actually receive the treatment, did not comply with treatment or drop-out. Intention to treat analysis is a more reliable estimate of true treatment effectiveness by replicating what happens in the ‘real world’ (e.g. noncompliance and protocol violations commonly affect therapies).

Cholera has an incubation period of 12 hours to 6 days.Other infectious disease that have an incubation period of less than 1 week include:Staphylococcal enteritis (1-6 hours)Salmonella enteritis (12-24 hours)Botulism (18-36 hours)Gas gangrene (6 hours to 4 days)Scarlet fever (1-4 days)Diphtheria (2-5 days)Gonorrhoea (3-5 days)Yellow fever (3-6 days)Meningococcaemia (1-7 days)Brucellosis has an incubation period of 7-21 days.Measles has an incubation period of 14-18 days.Falciparum malaria usually has an incubation period of 7-14 days. The other forms of malaria have a longer incubation period of 12-40 days.Rubella has an incubation period of 14-21 days.

ACE inhibitors have many uses and are generally well tolerated. They are indicated for:Heart failureHypertensionDiabetic nephropathySecondary prevention of cardiovascular events