Ciprofloxacin belongs to the quinolone group of antibiotics, and doxycycline and minocycline are tetracyclines. So, they are not affected by beta-lactamase.
However, amoxicillin is a beta-lactam antibiotic and beta-lactamase cleaves the beta-lactam ring present in amoxicillin. This results in the breakdown of the antibiotic and thus the area of erythema dramatically increased.
Co-amoxiclav contains amoxicillin and clavulanic acid which protects amoxicillin from beta-lactamase.

Codeine is easily absorbed from the gastrointestinal tract and converted to morphine and norcodeine in the liver via O- and N-demethylation. Morphine and norcodeine are excreted almost entirely by the kidney, primarily as conjugates with glucuronic acid.

By glucuronidation, phase II metabolism enzyme UDP-glucuronosyl transferase-2B7 converts morphine to morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) (UGT2B7).

Approximately 60% of morphine is converted to M3G, with the remaining 6-10% converted to M6G. M3G is inactive, but M6G is said to be 4 to 650 times more potent on the MOP receptor than morphine.

When codeine is consumed, cytochrome P450 2D6 in the liver converts it to morphine (CYP2D6).

Some people have DNA variations that increase the activity of this enzyme, causing codeine to be converted to morphine more quickly and completely than in others. After taking codeine, these ultra-rapid metabolisers are more likely to have higher than normal levels of morphine in their blood.

Respiratory depression/obstruction can be caused by high levels of morphine and M6G, especially in people who have a history of obstructive sleep apnoea. The estimated number of ultra-rapid metabolisers ranges from 1 to 7 per 100 people, but some ethnic groups may have as many as 28 per 100 people.

Respiratory inspiration causes a decreased pressure in the thoracic cavity, which in turn causes more blood to flow into the atrium.

Sitting up decreases venous because of the action of gravity on blood in the venous system.
Hypotension also decreases venous return.
A less compliant aorta, like in aortic stenosis increases end systolic left ventricular volume which decreases stroke volume.

Systemic vascular resistance = mean arterial pressure / cardiac output. Increased vascular resistance impedes the flow of blood back to the heart.

Increased venous return increases end diastolic LV volume as there is more blood returning to the ventricles.

A major source of caloric expenditure and oxygen consumption in the body is work of breathing (WOB) and 70% of this is to overcome elastic forces. The remaining 30% is for flow-resistive work

In a normal patient breathing normally, the total area of hysteresis pressure volume curve represents the flow-resistive WOB.

The area of the expiratory resistive work increases during an asthma attack making the compliance curve larger in area. The larger the area the greater the work required to breathe.

Noradrenaline also called norepinephrine belongs to the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter.

They have sympathomimetic effects acting via adrenoceptors (?1, ?2,?1, ?2, ?3) or dopamine receptors (D1, D2).

May cause reflex bradycardia, reduce cardiac output and increase myocardial oxygen consumption

The upper limb venous drainage is divided into superficial and deep. The superficial veins are accessible to draw blood for investigations. The cephalic, basilic, and median cubital veins are superficial veins.

The median cubital vein connects the cephalic vein and basilic vein. It is located anteriorly in the antecubital fossa and is preferred for venepuncture due to its palpability and ease of access.

The basilic vein and cephalic vein are the primary veins that drain the upper limb. They begin as the dorsal venous arch. The basilic vein originates from the ulnar side, while the cephalic vein originates from the radial side of the dorsal arch of the upper limb.

Second messengers relay signals to target molecules in the cytoplasm or nucleus when an agonist interacts with a receptor on the cell surface. They also amplify the strength of the signal. The most ubiquitous and abundant second messenger is calcium and it regulates multiple cellular functions in the body.

These include:
Muscle contraction (skeletal, smooth and cardiac)
Exocytosis (neurotransmitter release at synapses and insulin secretion)
Apoptosis
Cell adhesion to the extracellular matrix
Lymphocyte activation
Biochemical changes mediated by protein kinase C.

cAMP is either inhibited or stimulated by G proteins.

The receptors in the body that stimulate G proteins and increase cAMP include:

Beta (?1, ?2, and ?3)
Dopamine (D1 and D5)
Histamine (H2)
Glucagon
Vasopressin (V2).

The second messenger for the action of nitric oxide (NO) and atrial natriuretic peptide (ANP) is cGMP.

The second messengers for angiotensin and thyroid stimulating hormone are inositol triphosphate (IP3) and diacylglycerol (DAG).

The potential difference (amplitude) and bandwidth frequencies of bioelectric signals are typical.

These are the following:

ECG: A bandwidth of 0.5-50 Hz is usually sufficient in monitoring mode, but a typical diagnostic bandwidth is 0.05-150 Hz (up to 200 Hz) with a typical voltage range of 0.1-4 millivolts (100-4000 microvolts).
EEG has a frequency range of 0.5-100 Hz and a voltage range of 0.5-100 microvolts.
EMG has a frequency range of 0.5 to 350 Hz and a voltage range of 0.5 to 30 millivolts.

Prior to display, these small signals will need to be amplified and processed further.

Number needed to treat (NNT) is a time specific epidemiological measure that indicates how many patients would be require for an intervention to prevent one additional bad outcome. A perfect NNT would be 1, where everyone improves with treatment, thus the higher the NNT, the less effective the treatment.

Thus if you treat 1000 patients then you will expect to have 50 fewer strokes.

The structures in the porta hepatis from anterior to posterior are:

The ducts: Most anterior are the left and right hepatic ducts.

The arteries: Next are the left and right hepatic arteries

The veins: Next is the portal vein

The epiploic foramen of Winslow lies most posterior at the porta hepatis.

The cephalic vein is one of the primary superficial veins of the upper limb. It overlies most of the fascial planes as it is located in the superficial fascia along the anterolateral surface of the biceps.

It originates in the anatomical snuffbox from the radial side of the superficial venous network of the dorsum of the hand. It travels laterally up the arm to join the basilic vein via the median cubital vein at the elbow.

Near the shoulder, it passes between the deltoid and pectoralis major muscles. It pierces the coracoid membrane (continuation of the clavipectoral fascia) to terminate in the axillary vein’s first part.

The National Institute for Health and Care Excellence (NICE) has published guidelines on infective endocarditis prophylaxis (IE). The goal was to create clear guidelines for antibiotic prophylaxis in patients undergoing dental procedures as well as certain non-dental interventional procedures. A number of studies have found an inconsistent link between recent interventional procedures and the development of infective endocarditis in both dental and non-dental procedures.

Antibiotic prophylaxis against infective endocarditis is not advised or required in the following situations:

Dental patients undergoing procedures
Patients undergoing procedures involving the upper and lower gastrointestinal tracts, the genitourinary tract (including urological, gynaecological, and obstetric procedures, as well as childbirth), and the upper and lower respiratory tract (including ear, nose and throat procedures and bronchoscopy).

Antibiotic resistance can be exacerbated by the indiscriminate use of prophylactic antibiotics, but this is not the primary reason for avoiding their use in these situations.

To reduce the risk of endocarditis, any patient who is at risk of developing IE should be investigated and treated as soon as possible. Patients with the following conditions are at risk of developing IE:
acquired valvular heart disease with regurgitation or stenosis
previous valve replacement
structural congenital heart disease
past history of IE, or
hypertrophic cardiomyopathy (HOCM)

It would also be appropriate for high-risk dental procedures and those with severe gingival disease.

Although this patient may not have structural heart disease, ABs should be administered on a case-by-case basis.

Recall bias introduced when participants in a study are systematically more or less likely to recall and relate information on exposure depending on their outcome status.

In procedure bias, the researcher decides assignment of a treatment versus control and assigns particular patients to one group or the other non-randomly. This is unlikely to have occurred in this case, although it is not mentioned specifically.

Self Selection or volunteer bias occur when those subjects are selected to participate in the study who are not the representative of the entire target population. those subjects may be from high socio-economic status and practice those activities or lifestyle that improves their health.

Lead-time bias occurs when a disease is detected by a screening test at an earlier time point rather than it would have been diagnosed by its clinical appearance. In this bias, earlier detection improves the survival time in the intervention group.

In general practice, majority of phase 3 trials and some of the trials conducted in phase 2 are randomized. Because phase 4 trials require a huge sample size, they are not randomized as much. The primal reason behind conducting phase 3 trials is to test the efficiency and safety in a significant sample population. At this point it is assumed that the drug is effective up to a certain extent.

During a case-control study, subjects that exhibit outcomes of interest are compared with those who don’t show the expected outcome. The extent of exposure to a particular risk factor is then matched between cases and controls. If the exposure among cases surpasses controls, it becomes a risk factor for the outcome that is being studied.

Pilot studies are conducted on a lower and much smaller level, to assess if a randomized controlled trial of the crucial components of a study will be plausible.

Phase 4 trials are the ones that are conducted after its established that the drug is effective and is approved by the regulating authority for use. These trials are concerned with the side effects and potential risks associated with the long term usage of the drug.

A Wrights Respirometer measures the volume of air exhaled over the course of one minute of normal breathing

It is unidirectional and measures tidal volume and minute volume of gas flow in one direction. It is placed at the expiratory side (lower pressure than inspiratory side therefore lower chances of gas leaks)

Slits are arranged such that incoming gas will rotate the vane at a rate of 150 revolutions per litre of flowing gas

The Wright respirometer tends to over-read at high flow rates and under-read at low flows because of mechanical causes like friction and inertia and the accumulation of water vapour

The ideal flow for accurate readings is 2 L/min for the respirometer. The respirometer reads the tidal volume and minute volume with a ±5–10% accuracy within the range of 4–24 L/min.

An ankle block is commonly used for anaesthesia and postoperative analgesia when operating on bunions. It results in the selective block of the superficial peroneal, deep peroneal, and posterior tibial nerves.

The deep peroneal nerve supplies sensory input to the web space between the first and second toes (L4-5).

The L2-S1 nerve, often known as the superficial peroneal nerve, is a mixed motor and sensory neuron. It gives sensory supply to the anterolateral region of the leg, the anterior aspect of the 1st, 2nd, 3rd, and 4th toes, and innervates the peroneus longus and brevis muscles (with the exception of the web space between 1st and 2nd toes).

The sensory area of the saphenous nerve (L3-4) in the foot stretches from the proximal portion of the midfoot on the medial side to the proximal part of the midfoot on the lateral side.

The lateral side of the little (fifth) toe is innervated by the sural nerve’s sensory supply (S1-2). The heel, medial (medial plantar nerve), and lateral (lateral plantar nerve) soles of the foot are all served by the posterior tibial nerve.

When there is a fall in ionised plasma calcium levels, the chief cells of the parathyroid glands are stimulated to secrete parathyroid hormone (PTH).

50% of extracellular calcium occurs as non-ionised, protein- (albumin-)bound calcium.

The degree of ionisation increases with low ph and decreases with high pH.

There is increased renal calcium excretion with secretion of calcitonin.

The superior mesenteric artery branches from the abdominal aorta just 1-2 cm below the origin of the celiac trunk. It lies posterior to the body of the pancreas and splenic vein and is separated from the aorta by the left renal vein. It passes forwards and inferiorly, anterior to the uncinate process of the pancreas and the third part of the duodenum, to enter the root of the small bowel mesentery and supply the midgut.

The important landmarks of vessels arising from the abdominal aorta at different levels of vertebrae are:

T10 – oesophageal opening in the diaphragm

T12 – Coeliac trunk, aortic hiatus in the diaphragm

L1 – Left renal artery

L2 – Testicular or ovarian arteries

L3 – Inferior mesenteric artery

L4 – Bifurcation of the abdominal aorta

The laryngeal folds are comprised of two types of folds; the vestibular fold and the vocal fold. The vocal folds are mobile, and concerned with voice production. They are formed by the mucous membrane covering the vocal ligament. They are avascular, hence, are white in colour.

The internal branch of the superior laryngeal nerve provides sensation above the vocal cords. Lesions to this nerve may lead to loss of sensation above the vocal cords and loss of taste on the epiglottis.

The recurrent laryngeal nerve supplies the lateral and posterior cricoarytenoid, the thyroarytenoid. It also provides sensation below the vocal cords. Lesions to this nerve may cause respiratory obstruction, hoarseness, inability to speak and loss of sensation below the vocal cords.

The external branch of the superior laryngeal nerve supplies the cricothyroid muscle.

The glossopharyngeal nerve contains both sensory and motor components, and provides somatic innervation to the stylopharyngeus muscle, visceral motor innervation to the parotid gland, and carries afferent sensory fibres from the posterior third of the tongue, pharynx and tympanic cavity.

The patient likely suffers from pulmonary embolism due to her history of frequent international travels. A filter is placed in the inferior vena cava to decrease the risk of future episodes of pulmonary embolism. The IVC filter is a small, wiry device that can catch blood clots and stop them from going into the heart and lungs. Your IVC is a major vessel that brings deoxygenated blood from the lower body to the heart, from where it is pumped into the lungs.

The filter is placed via a thin catheter inserted into the femoral vein in the groin. The catheter is gently moved up into your IVC, and a filter is introduced.

The IVC is a retroperitoneal organ.

A decrease in the functional residual capacity (FRC) is the most important physiologic change to consider for such patients.

FRC is the sum of the expiratory reserve volume and the residual volume. It is the resting volume of the lung, and is an important marker for lung function. During this time, the alveolar pressure is equal to the atmospheric pressure. When morbidly obese individuals lie supine, the FRC decreases by as much as 40% because the abdominal contents push the diaphragm into the thoracic cavity.

Chest wall compliance is expected to reduce because of fat deposition surrounding adjacent structures.

Inspiratory reserve volume (IRV) is expected to increase, and peak expiratory flow is expected to decrease, however the decrease in FRC is more important to consider because of the risk of hypoxia secondary to premature airway closure and ventilation-perfusion mismatch.

Tramadol is weak agonist at the mu receptor. It inhibits the neuronal reuptake of serotonin and norepinephrine, and inhibits pain neurotransmission. It is given for moderate pain, chronic pain syndromes, and neuropathic pain.

Fluoxetine is a selective serotonin reuptake inhibitor (SSRI). It inhibits the neuronal reuptake of serotonin by inhibiting the serotonin transporter (SERT). It is the drug of choice for major depressive disorder, and is given for other psychiatric disorders such as anxiety, obsessive-compulsive, post-traumatic stress, and phobias.

When tramadol is given with SSRIs, serotonin syndrome may occur. Serotonin syndrome is characterized by fever, agitation, tremors, clonus, hyperreflexia and diaphoresis. The onset of symptoms may occur within a few hours, and the first-line treatment is sedation, paralysis, intubation and ventilation.

The trochlear nerve (CN IV) is the fourth and smallest cranial nerve. It’s role is to provide somatic motor innervation of the superior oblique muscle which is responsible for oculomotion.

Injury to the trochlear nerve will result in vertical diplopia, which worsens when looking downwards or inwards. This diplopia presents as an upward deviation of the eye with a head tilt away from the site of the lesion.

The abducens nerve (CN VI) provides somatic motor innervation for the lateral rectus muscle which functions to abduct the eye. Injury to this nerve will cause diplopia and an inability to abduct the eye, causing the patient to have to rotate their head to look sideways.

The facial nerve (CN VII) provides sensory, motor and parasympathetic innervations. It’s motor aspect controls the muscles of facial expression. Damage will cause paralysis of facial expression.

The oculomotor nerve (CN III) provides motor and parasympathetic innervations. Its motor component controls most of the other extraocular muscles. Damage to it will result in ptosis, dilatation of the pupil and a down and out eye position.

The ophthalmic division of the trigeminal nerve (CN VI) is responsible for sensory innervation of skin, mucous membranes and sinuses of the upper face and scalp.

The statement Epinephrine is formulated as 1 in 1000 solution means 1 gm epinephrine is present in 1000 ml of solution.

Both incidence and prevalence are indicators of the disease frequency. While incidence tells us about the number of cases reported per population in a provided time period, prevalence is the factor you should be vigilant about as it tells us about the total number of cases that have been reported in a population at a particular point of time.

If there is no change in preload and myocardial contractility, there will be decrease in end-diastolic volume and stroke volume. So there must be increase in end-systolic volume.

Only on rare occasions has it been found that the prevalence and incidence were same. Incidence can be greater than prevalence in acute cases only. In case of chronic diseases prevalence is far greater than incidence. One needs to have a deeper understanding of both the concepts to understand the health literature.

Ketamine, a phencyclidine derivative, is an antagonist at the NMDA receptor. It causes depression of the CNS that is dose dependent and induces a dissociative anaesthetic state with profound analgesia and amnesia.

Ketamine has a chiral centre usually presented as a racemic mixture with two optical isomers, S (+) and R (-) forms. These isomers are in equal proportions. The S (+) isomer is about three times more potent than the R (-) form. The S (+) form is less likely to cause emergence delirium and hallucinations.

Ketamine is extensively metabolised by hepatic microsomal cytochrome P450 enzymes producing norketamine as its main metabolite. Norketamine has a one third to one fifth as potency as its parent compound.
It increases the CMRO2, cerebral blood flow and potentially increase intracranial pressure.

A thermocouple, or a thermal junction, is temperature measuring device consisting of a pair of dissimilar metal (bimetallic) wires or strips joined together. Typically, copper and constantan (an alloy of 55% copper and 45% nickel) are used. When there is contact between these metals, a small voltage is generated in the order of millivolts. The magnitude of the thermojunction electromotive force (emf) is proportional to applied temperature (the Seebeck effect). This physical principle is applied in the measurement of temperature. The electromotive force at the measuring junction is proportional to temperature.

Two wires with different coefficients of expansion, joined together, can be used as a switch for thermostatic control.

Semiconductors are NOT used in thermocouple. The resistance of the measuring junction of a thermocouple is irrelevant.

Normally, the oesophagus is lined by non-keratinized stratified squamous epithelium. This epithelium can undergo metaplasia and convert to the columnar epithelium (stomach’s lining) in long-standing GERD that leads to Barret’s oesophagus.