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Question 1
Correct
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A 58-year-old man with a long history of depression presents with a deliberate overdose of verapamil tablets, which he is prescribed for a heart condition.What is verapamil's mechanism of action?
Your Answer: L-type calcium channel blockade
Explanation:Overdosing on calcium-channel blockers should always be taken seriously and regarded as potentially fatal. Verapamil and diltiazem are the two most lethal calcium channel blockers in overdose. These work by binding the alpha-1 subunit of L-type calcium channels, preventing calcium from entering the cell. In cardiac myocytes, vascular smooth muscle cells, and islet beta-cells, these channels play an important role.The standard ABC approach should be used to resuscitate all patients as needed. If life-threatening toxicity is expected, intubation and ventilation should be considered early on. If hypotension and shock are developing, early invasive blood pressure monitoring is recommended.The primary goal of specific treatments is to support the cardiovascular system. These are some of them:1. Fluid resuscitation: Give up to 20 mL of crystalloid per kilogramme of body weight.2. Calcium supplementationThis can be a good way to raise blood pressure and heart rate temporarily.via central venous access: 10% calcium gluconate 60 mL IV (0.6-1.0 mL/kg in children) or 10% calcium chloride 20 mL IV (0.2 mL/kg in children)Boluses can be given up to three times in a row.To keep serum calcium >2.0 mEq/L, consider a calcium infusion.3. Atropine: 0.6 mg every 2 minutes up to 1.8 mg is an option, but it is often ineffective.4. HIET (high-dose insulin-euglycemic therapy):The role of HIET in the step-by-step management of cardiovascular toxicity has changed.5. Vasoactive infusions:This was once thought to be a last-ditch measure, but it is now widely recommended that it be used sooner rather than later.Insulin with a short half-life 50 mL of 50 percent glucose IV bolus plus 1 U/kg bolus (unless marked hyperglycaemia present)Short-acting insulin/dextrose infusions should be continued.Glucose should be checked every 20 minutes for the first hour, then hourly after that.Regularly check potassium levels and replace if they fall below 2.5 mmol/L.Titrate catecholamines to effect (inotropy and chronotropy); options include dopamine, adrenaline, and/or noradrenaline infusions.6. Sodium bicarbonate: Use 50-100 mEq sodium bicarbonate (0.5-1.0 mEq/kg in children) in cases where a severe metabolic acidosis develops.7. Cardiac pacing: It can be difficult to achieve electrical capture, and it may not improve overall perfusion.Bypass AV blockade with ventricular pacing, which is usually done at a rate of less than 60 beats per minute.8. Intralipid transportCalcium channel blockers are lipid-soluble agents, so they should be used in refractory cases.
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This question is part of the following fields:
- Cardiovascular Pharmacology
- Pharmacology
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Question 2
Incorrect
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In the treatment of hypertensive episodes in pheochromocytoma, which of the following medication types is administered as first-line management:
Your Answer: Beta-blockers
Correct Answer: Alpha-blockers
Explanation:The first line of management in controlling blood pressure and preventing intraoperative hypertensive crises is to use a combination of alpha and beta-adrenergic inhibition. In phaeochromocytoma, alpha-blockers are used to treat hypertensive episodes in the short term. Tachycardia can be managed by the careful addition of a beta-blocker, preferably a cardioselective beta-blocker, once alpha blockade has been established. Long term management of pheochromocytoma involves surgery.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 3
Correct
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A 20-year-old female presents with painful wrist following a fall while skating. X-rays shows fracture of the ulna.The initial phase of bone healing is?
Your Answer: Haematoma at the fracture site
Explanation:Haemorrhage occurs into the fracture site from the ruptured vessels in the bone marrow and those supplying the periosteum immediately after fracture. This hematoma formation is the first phase of bone healing.The 4 stages of bone healing are:Haematoma at the fracture site (provides a framework for healing)Callus formationLamellar bone formationRemodelling
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This question is part of the following fields:
- General Pathology
- Pathology
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Question 4
Incorrect
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A 70-year-old patient diagnosed with Cushing's syndrome, has a history of weight gain, hypertension, and easy bruising.Which of the following statements about Cushing's syndrome is NOT true?
Your Answer: The commonest cause is iatrogenic corticosteroid administration
Correct Answer: Menorrhagia is a common feature
Explanation:Cushing’s syndrome is a group of symptoms and signs brought on by long-term exposure to high amounts of endogenous or exogenous glucocorticoids.Iatrogenic corticosteroid injection is the most prevalent cause of Cushing’s syndrome.Cortisol levels fluctuate throughout the day, with the greatest levels occurring around 0900 hours and the lowest occurring at 2400 hrs during sleep. The diurnal swing of cortisol levels is lost in Cushing’s syndrome, and levels are greater throughout the 24-hour period. In the morning, levels may be normal, but they may be high at night-time, when they are generally repressed.Insulin resistance causes hyperglycaemia, which is a frequent symptom. Insulin resistance can produce acanthosis nigricans in the axilla and around the neck, as well as other skin abnormalities.In contrast to menorrhagia, elevated testosterone levels are more likely to produce amenorrhoea or oligomenorrhoea. Infertility in women of reproductive age can also be caused by high androgen levels.A dexamethasone suppression test or a 24-hour urine free cortisol collection can both be used to establish the existence of Cushing’s syndrome.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 5
Correct
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Metabolic hyperaemia harmonizes local blood flow with local O2 demand. If there is an increase in metabolic rate, the production of vasoactive metabolites increases. These metabolites act locally on the surrounding arterioles, causes vasodilation and an increase blood supply.Which of these metabolites is the most potent vasodilator in skeletal muscle?
Your Answer: K +
Explanation:Hyperaemia is the process where the body adjusts blood flow to meet the metabolic needs of different tissues in health and disease. Vasoactive mediators that take part in this process include K+, adenosine, CO2, H+, phosphates and H2O2. Although the mechanism is not clear, all these mediators likely contribute to some extent at different points.Specific organs are more sensitive to specific metabolites:K+ and adenosine are the most potent vasodilators in skeletal musclesCO2 and K+ are the most potent vasodilators in cerebral circulation.
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This question is part of the following fields:
- Cardiovascular Physiology
- Physiology
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Question 6
Incorrect
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The movement of molecules across the cell membrane relies greatly on active transport.Which of the following statements about active transport is correct?
Your Answer: Primary active transport involves the use of an electrochemical gradient
Correct Answer: Active transport occurs in glucose absorption from the gut
Explanation:The movement of a material against a concentration gradient, i.e. from a low to a high concentration, is known as active transport. Primary active transport is defined as active transport that involves the use of chemical energy, such as adenosine triphosphate (ATP). Secondary active transport occurs when an electrochemical gradient is used.The sodium-potassium pump, calcium ATPase pump, and proton pump are all key active transport systems that use ATP. An electrochemical gradient is used by the sodium-calcium co-transporter, which is an example of secondary active transport.The sodium-dependent hexose transporter SGLUT-1 transports glucose and galactose into enterocytes. Secondary active transport is exemplified here.
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 7
Correct
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At rest, skeletal muscle accounts for between 15-20% of cardiac output and accounts for around 50% of body weight. This can increase to nearly 80% of cardiac output during exercise. Skeletal muscle circulation is highly controlled and has a number of specialized adaptations as a result of this high degree of disparity during exercise, in combination with the diversity in the size of skeletal muscle around the body.What is the primary mechanism for boosting skeletal muscle blood flow during exercise?
Your Answer: Metabolic hyperaemia
Explanation:In skeletal muscle, blood flow is closely related to metabolic rate. Due to the contraction of precapillary sphincters, most capillaries are blocked off from the rest of the circulation at rest and are not perfused. This causes an increase in vascular tone and vessel constriction. As metabolic activity rises, this develops redundancy in the system, allowing it to cope with greater demand. During exercise, metabolic hyperaemia, which is induced by the release of K+, CO2, and adenosine, recruits capillaries. Sympathetic vasoconstriction in the active muscles is overridden by this. Simultaneously, blood flow in non-working muscles is restricted, preserving cardiac output. During exercise, muscle contractions pump blood through the venous system, raising the pressure differential between arterioles and venules and boosting blood flow via capillaries.Capillary angiogenesis is evident when muscles are used repeatedly (e.g. endurance training). It is a long-term effect, not a quick fix for increased blood flow.The local partial pressure of alveolar oxygen is the primary intrinsic control of pulmonary blood flow (pAO2). Low pAO2 promotes arteriole vasoconstriction and vice versa. The hypoxic pulmonary vasoconstriction (HPV) reflex allows blood flow to be diverted away from poorly ventilated alveoli and towards well-ventilated alveoli in order to maximize gaseous exchange.
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This question is part of the following fields:
- Cardiovascular Physiology
- Physiology
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Question 8
Correct
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Question 9
Incorrect
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A 35-year-old man presents with haemoptysis, night sweats, and weight loss. Further examinations were done and a diagnosis of tuberculosis is suspected. Which of the following statements is considered correct regarding Mycobacterium tuberculosis?
Your Answer: It Gram stains red
Correct Answer: It is impervious to decolourisation with acid
Explanation:Mycobacterium tuberculosis are part of the Mycobacteriaceae family. They are described to have the characteristics of a Gram-positive cell wall but they are not easily stained with Gram stain. This is because their cell wall contains a high lipid content, and this lipid allows the Mycobacteria to bind to alkaline stains with the application and help of heat. Once stained, they are able to resist decolorization even with the use of acid alcohol as the decolourizer, making them very difficult to decolorize, that is why they are known to be acid-fast.The Ghon complex is a non-pathognomonic radiographic finding on a chest x-ray that is significant for pulmonary infection of tuberculosis. The location of the Ghon’s focus is usually subpleural and predominantly in the upper part of the lower lobe and lower part of the middle or upper lobe. Skeletal tuberculosis of the spine is referred to as Pott disease.The risk of reactivation TB is about 3.3% during the first year after a positive PPD skin test and a total of 5% to 15% thereafter in the person’s lifetime. Progression from infection to active disease varies with age and the intensity and duration of exposure. Reactivation TB occurs when there is an alteration or suppression of the cellular immune system in the infected host that favoursreplication of the bacilli and progression to disease.
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This question is part of the following fields:
- Microbiology
- Specific Pathogen Groups
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Question 10
Correct
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After what time period should intravenous phenytoin be used as second-line treatment of status epilepticus?
Your Answer: 25 minutes
Explanation:If seizures recur or fail to respond after initial treatment with benzodiazepines within 25 minutes of onset, phenytoin sodium, fosphenytoin sodium, or phenobarbital sodium should be used.
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This question is part of the following fields:
- Central Nervous System
- Pharmacology
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Question 11
Incorrect
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A range of one standard deviation above and below the mean includes what approximate percentage of the sample values:
Your Answer: 0.78
Correct Answer: 0.68
Explanation:A range of one SD above and below the mean (+/- 1 SD) includes 68.2% of the sample values.A range of two SD above and below the mean (+/- 2 SD) includes 95.4% of the sample values.A range of three SD above and below the mean (+/- 3 SD) includes 99.7% of the sample values.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 12
Correct
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Doxycycline is indicated first line for treatment of which of the following infections:
Your Answer: Chlamydia
Explanation:Doxycycline may be used first line for chlamydia, pelvic inflammatory disease (with metronidazole and ceftriaxone), acute bacterial sinusitis, exacerbation of chronic bronchitis, moderate-severity community acquired pneumonia and high-severity community acquired pneumonia (with benzylpenicillin).
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 13
Correct
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A 25-year old male is brought to the emergency room after a traffic accident. Upon examination, there was tenderness and erythema on the right acromioclavicular joint, with notable step deformity. On radiographic imaging, there is a superior elevation of the clavicle, a twice than normal coracoclavicular distance, and absence of fracture.Which of the following structure/s is/are likely to have ruptured?
Your Answer: Acromioclavicular ligament, coracoclavicular ligament and joint capsule
Explanation:Acromioclavicular joint injuries account for more than forty percent of all shoulder injuries. Mild injuries are not associated with any significant morbidity, but severe injuries can lead to significant loss of strength and function of the shoulder. Acromioclavicular injuries may be associated with a fractured clavicle, impingement syndromes, and more rarely neurovascular insults.The AC joint is a diarthrodial joint defined by the lateral process of the clavicle articulating with the acromion process as it projects anteriorly off the scapula. The joint is primarily stabilized by the acromioclavicular ligament, which is composed of an anterior, posterior, inferior, and superior component. Of note, the superior portion of the AC ligament is the most important component for the stability of the AC joint. Supporting structures include two coracoclavicular ligaments (trapezoid and conoid ligaments), which provide vertical stability, as well as the coracoacromial ligament.Patients with an AC joint injury typically present with anterosuperior shoulder pain and will describe a mechanism of injury of blunt trauma to the abducted shoulder or landing on an outstretched arm, suggestive of this type of injury. They may describe pain radiating to the neck or shoulder, which is often worse with movement or when they try to sleep on the affected shoulder. On examination, the clinician may observe swelling, bruising, or a deformity of the AC joint, depending on the degree of injury. The patient will be tender at that location. They may have a restriction in the active and passive range of motion secondary to pain. Piano key sign may be seen, with an elevation of the clavicle that rebounds after inferior compression.Standard X-rays are adequate to make a diagnosis of acromioclavicular joint injury and should be used to evaluate for other causes of traumatic shoulder pain.
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This question is part of the following fields:
- Anatomy
- Upper Limb
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Question 14
Incorrect
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A 20-year-old male has an anaphylactic reaction following a wasp sting.What type of hypersensitivity reaction is this?
Your Answer: Type III
Correct Answer: Type I
Explanation:Anaphylaxis is an example of a type I hypersensitivity reaction. It is IgE mediated. It requires a prior exposure to the antigen. The initial exposure sensitizes the body to the antigen and a second exposure to that antigen leads to an anaphylactic reaction.Massive calcium influx into the cells leads to mast cell degranulation. The Immunoglobulin antigen complex binds to Fc receptors on the surface of mast cells. The result is mast cell degranulation and release of histamine, proteoglycans and serum proteases from cytoplasmic granules.
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This question is part of the following fields:
- General Pathology
- Pathology
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Question 15
Correct
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Which of the following statements is correct with regards to Horner's syndrome?
Your Answer: Miosis occurs due to paralysis of the dilator pupillae muscle.
Explanation:The characteristics of Horner’s syndrome are pupil constriction, partial ptosis and anhidrosis.
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This question is part of the following fields:
- Anatomy
- Head And Neck
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Question 16
Incorrect
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A 60-year-old man with trauma to his cervical spine suffers from damage to the ansa cervicalis, resulting to paresis of his infrahyoid muscles.All of the following are considered infrahyoid muscles, except:
Your Answer: Sternothyroid
Correct Answer: Mylohyoid
Explanation:Infrahyoid muscles are also known as “strap muscles” which connect the hyoid, sternum, clavicle and scapula. They are located below the hyoid bone on the anterolateral surface of the thyroid gland and are involved in movements of the hyoid bone and thyroid cartilage during vocalization, swallowing and mastication. They are composed of four paired muscles, organized into two layers.Superficial layer consists of the sternohyoid and omohyoidDeep layer consists of the sternothyroid and thyrohyoid.
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This question is part of the following fields:
- Anatomy
- Head And Neck
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Question 17
Correct
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Which of the following is the primary indication for loop diuretics?
Your Answer: Acute pulmonary oedema
Explanation:Loop diuretics have long been the cornerstone of pulmonary oedema treatment, with furosemide being the most commonly used of these drugs. Premedication with drugs that decrease preload (e.g., nitro-glycerine [NTG]) and afterload (e.g., angiotensin-converting enzyme [ACE] inhibitors) before the administration of loop diuretics can prevent adverse hemodynamic changes.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 18
Incorrect
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During bedside rounds, an 82-year old female in the Medicine Ward complains of pain and tingling of all fingers of the right hand. The attending physician is considering carpal tunnel syndrome.Which of the following is expected to undergo atrophy in carpal tunnel syndrome?
Your Answer: The hypothenar eminence
Correct Answer: The thenar eminence
Explanation:Carpal tunnel syndrome (CTS) is an entrapment neuropathy caused by compression of the median nerve as it travels through the wrist’s carpal tunnel. It is the most common nerve entrapment neuropathy, accounting for 90% of all neuropathies. Early symptoms of carpal tunnel syndrome include pain, numbness, and paraesthesia’s. These symptoms typically present, with some variability, in the thumb, index finger, middle finger, and the radial half (thumb side) of the ring finger. Pain also can radiate up the affected arm. With further progression, hand weakness, decreased fine motor coordination, clumsiness, and thenar atrophy can occur.The muscles innervated by the median nerve can be remembered using the mnemonic ‘LOAF’:L– lateral two lumbricalsO– Opponens pollicisA– Abductor pollicisF– Flexor pollicis brevisIn the early presentation of the disease, symptoms most often present at night when lying down and are relieved during the day. With further progression of the disease, symptoms will also be present during the day, especially with certain repetitive activities, such as when drawing, typing, or playing video games. In more advanced disease, symptoms can be constant.Typical occupations of patients with carpal tunnel syndrome include those who use computers for extended periods of time, those who use equipment that has vibration such as construction workers, and any other occupation requiring frequent, repetitive movement.
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This question is part of the following fields:
- Anatomy
- Upper Limb
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Question 19
Correct
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As a response to low blood pressure, the baroreceptor reflex will facilitate vasoconstriction by activating which receptor?
Your Answer: Alpha1
Explanation:The rate of baroreceptor firing slows down when blood pressure falls too low. This causes an increase in sympathetic stimulation of the heart, resulting in an increase in cardiac output. It also causes vasoconstriction by activating alpha 1 receptors in smooth muscle, which causes sympathetic stimulation of peripheral vessels. Alpha2 receptors can be found in both the brain and the peripheral nervous system. They control sympathetic outflow in the brain stem. Beta1 receptors, which are found on the cell membrane of cardiac muscle cells, stimulate heart rate and myocardial contractility. The smooth muscle cell membrane contains beta2 receptors, which promote smooth muscle relaxation in the lungs causing bronchodilation, GI tract, and peripheral blood vessels.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 20
Incorrect
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A 32-year-old woman with a history of bipolar disorder exhibits lithium toxicity symptoms.Which of the following is the MOST LIKELY feature to be present?
Your Answer: Xanthopsia
Correct Answer: Clonus
Explanation:Lithium toxicity manifests itself in the following ways:AtaxiaClonusComaConfusionConvulsionsDiarrhoeaIncreased muscle toneNausea and vomitingNephrogenic diabetes insipidusRenal failureTremor
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This question is part of the following fields:
- CNS Pharmacology
- Pharmacology
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Question 21
Correct
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In the emergency room, a patient was diagnosed with acute bacterial tonsillitis. Which of the following postinfectious complications is most commonly linked to Streptococcus pyogenes:
Your Answer: Glomerulonephritis
Explanation:Poststreptococcal glomerulonephritis (PSGN) is caused by prior infection with specific nephritogenic strains of group A beta-haemolytic streptococcus. The clinical presentation of PSGN varies from asymptomatic, microscopic haematuria to the full-blown acute nephritic syndrome, characterized by red to brown urine, proteinuria (which can reach the nephrotic range), oedema, hypertension, and acute kidney injury.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 22
Incorrect
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What is the partial pressure of oxygen if it makes up 20.9 percent of the ambient air composition and the atmospheric pressure of ambient air is 760 mmHg?
Your Answer:
Correct Answer: 159 mmHg
Explanation:Ambient air is atmospheric air in its natural state. Ambient air is typically 78.6% nitrogen and 20.9% oxygen. The extra 1% is made up of carbon, helium, methane, argon and hydrogen. The partial pressure of any gas can be calculated using this formula: P = atmospheric pressure (760 mmHg) x percent content in the mixture. Atmospheric pressure is the sum of all of the partial pressures of the atmospheric gases added together: The formula for atmospheric pressure is: Patm = PN2 + PO2 + PH2O + PCO2. The atmospheric pressure is known to be 760 mmHg. The partial pressures of the various gases can be estimated to have partial pressures of approximately 597.4 mmHg for nitrogen, 158.8 mm Hg for oxygen, and 7.6 mmHg for argon.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 23
Incorrect
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Which of the following statements is correct regarding gentamicin?
Your Answer:
Correct Answer: Gentamicin is ineffective against anaerobic bacteria.
Explanation:Gentamicin is the aminoglycoside of choice in the UK and is a parenterally administered, broad spectrum antibiotic typically used for moderate to severe gram negative infections. However, it is inactive against anaerobes. There is poor activity against haemolytic streptococci and pneumococci. It is usually given in conjunction with a penicillin or metronidazole (or both) when used for the blind treatment of undiagnosed serious infections. Nephrotoxicity and ototoxicity are the main toxic effects due to damage to the vestibulocochlear nerve (CN VIII).It is contraindicated in myasthenia gravis and should be used with great care in renal disease as it may result in accumulation and a higher risk of toxic side effects.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 24
Incorrect
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During her pregnancy, a 28-year-old lady was given an antibiotic. The neonate was prematurely born with cyanosis and ashen grey coloured skin as a result of this. Other symptoms were hypotonia, low blood pressure, and poor feeding.From the following antibiotics, which one is most likely to cause this side effect?
Your Answer:
Correct Answer: Chloramphenicol
Explanation:Grey baby syndrome is a rare but causes significant adverse effect caused by the build-up of chloramphenicol in neonates (particularly preterm babies).The following are the main characteristics of ‘grey baby syndrome’:Skin that is ashy grey in colour.Feeding problemsVomitingCyanosisHypotensionHypothermiaHypotoniaCollapse of the cardiovascular systemDistension of the abdomentrouble breathing
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 25
Incorrect
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Which of the following is NOT an adverse effect of amitriptyline:
Your Answer:
Correct Answer: Hypokalaemia
Explanation:Adverse effects include:Antimuscarinic effects: Dry mouth, Blurred vision, Constipation, Urinary retention, Sedation, ConfusionCardiovascular effects: Heart block, Arrhythmias, Tachycardia, Postural hypotension, QT-interval prolongation, Hepatic impairment, Narrow-angle glaucoma
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This question is part of the following fields:
- Central Nervous System
- Pharmacology
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Question 26
Incorrect
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Damage to this nerve affects the flexor digitorum longus.
Your Answer:
Correct Answer: Tibial nerve
Explanation:Like all muscles in the deep posterior compartment of the leg, flexor digitorum longus muscle is innervated by branches of the tibial nerve (root value L5, S1 and S2) which is a branch of sciatic nerve.
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This question is part of the following fields:
- Anatomy
- Lower Limb
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Question 27
Incorrect
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Oculomotor (CN III) palsy with sparing of the pupillary reflex is most likely caused by which of the following:
Your Answer:
Correct Answer: Diabetes mellitus
Explanation:Compressive causes of CN III palsy cause early pupillary dilatation because the parasympathetic fibres run peripherally in the nerve and are easily compressed. In diabetes mellitus the lesions are ischaemic rather than compressive and therefore typically affect the central fibres resulting in pupillary sparing.
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This question is part of the following fields:
- Anatomy
- Cranial Nerve Lesions
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Question 28
Incorrect
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Which of the following statements regarding forest plots is true? Select ONE answer only.Which of the following statements regarding forest plots is true? Select ONE answer only.
Your Answer:
Correct Answer: Larger studies are associated with smaller horizontal lines
Explanation:Forest plots are graphical displays designed to illustrate the relative strength of treatment effects in multiple individual studies addressing the same question.
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This question is part of the following fields:
- Evidence Based Medicine
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Question 29
Incorrect
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What type of visual field defect are you likely to see in a lesion of the visual cortex:
Your Answer:
Correct Answer: Contralateral homonymous hemianopia with macular sparing
Explanation:A lesion of the visual cortex will result in a contralateral homonymous hemianopia with macular sparing.
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This question is part of the following fields:
- Anatomy
- Central Nervous System
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Question 30
Incorrect
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One of your patients is in resuscitation and is suffering from kidney failure. The intensive care outreach team arrives to assess them and determines that a dopamine infusion is necessary.Dopamine primarily acts on which of the following receptors at low doses?
Your Answer:
Correct Answer: Dopamine receptors
Explanation:Dopamine is a catecholamine that occurs naturally and is used to treat low cardiac output, septic shock, and renal failure. It is both adrenaline and noradrenaline’s immediate precursor.Dopamine acts on D1 and D2 dopamine receptors in the renal, mesenteric, and coronary beds at low doses (1-5 g/kg/min). Dopamine causes a significant decrease in renal vascular resistance and an increase in renal blood flow at these doses. Within this dose range, it is also involved in central modulation of behaviour and movement.Dopamine stimulates beta- and alpha-adrenergic receptors directly and indirectly at higher doses. Beta-stimulation predominates at a rate of 5-10 g/kg/min, resulting in a positive inotropic effect that increases cardiac output and coronary blood flow. Alpha-stimulation predominates at infusion rates greater than 15 g/kg/min, resulting in peripheral vasoconstriction and an increase in venous return and systolic blood pressure.Below is a summary of the mechanisms and effects of various inotropic agents:InotropeMechanismEffectsAdrenaline (epinephrine)Beta-1 and -2 agonist at increasing doses;Alpha-agonist at high dosesIncreased cardiac output;Vasoconstriction at higher dosesNoradrenaline (norepinephrine)Mainly alpha-agonist;Beta-1 and -2 agonist at increasing dosesVasoconstriction;Some increased cardiac outputDopamineDopamine agonist at low doses;Beta-1 and -2 agonist at increasing doses;Alpha-agonist at high dosesIncreased cardiac output;Vasoconstriction at higher dosesDobutamineMainly beta-1 agonistIncreased cardiac output
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This question is part of the following fields:
- Cardiovascular Pharmacology
- Pharmacology
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SESSION STATS - PERFORMANCE PER SPECIALTY
