Hypochondriasis is an illness anxiety disorder, and describes excessively worriedness about the presence of a disease. While the woman is concerned about her possibility of developing motor neurone disease, she understands that no symptoms have yet appeared. Hypochondriasis involves patients who refuse to accept that they don’t have the disease, even if the results come back negative.

Late Look Bias occurs when the data is gathered or analysed at an inappropriate time e.g. when many of the subjects suffering from a fatal disease have died. This type of biasness might occur in some retrospective studies of motor neurone disease, but is not applicable to this prospective study.

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. Of all the options, lead time-bias is a better answer.

The Hawthorne Effect refers to groups modifying their behaviour simply because they are aware of being observed. Any differences in the behaviour have not been mentioned in the question, and it is highly unlikely that a change in patient’s behaviour would have affected their length of survival in this case.

The correct option is lead-time bias. Even if the new blood test diagnoses the disease earlier, it doesn’t affect the outcome, as the survival time was still on average 43 months from the onset of symptoms in both groups. With the help of blood test, the disease was only detected 8 months earlier.

The vagus nerve is a mixed nerve with both autonomic and somatic effects. Its most important somatic effect is the motor supply to the larynx via recurrent laryngeal nerves. If one vagus nerve is damaged, the result will be the same as damage to a single recurrent laryngeal nerve, leading to hoarseness of voice.

The vagus exits the skull via the jugular foramen, accompanied by the accessory nerve.

Anal tone, erections, and urination are all controlled by the sacral parasympathetic and would not be affected by the loss of the vagus. Parasympathetic controlled pupillary constriction is via the oculomotor nerve and would not be affected by the loss of the vagus.

ANOVA is based upon within group variance (i.e. the variance of the mean of a sample) and between group variance (i.e. the variance between means of different samples). The test works by finding out the ratio of the two variances mentioned above. (Commonly known as F statistic).

Ondansetron is a serotonin antagonist at the 5HT3 receptor. 5HT3 receptors in the gastrointestinal tract and in the vomiting centre of the medulla participate in the vomiting reflex. They are particularly important in vomiting caused by chemical triggers such as cancer chemotherapy drugs.

The nucleus solitarius is the recipient of all visceral afferents, and an essential part of the regulatory centres of the internal homeostasis, through its multiple projections with cardiorespiratory and gastrointestinal regulatory centres. It participates in the reflexes of the nerves innervating the nucleus, so it mediates cough reflex, carotid sinus reflex, gag reflex, and vomiting reflex.

Number needed to treat can be defined as the number of patients who need to be treated to prevent one additional bad outcome.

It can be found as:

NNT=1/Absolute Risk Reduction (rounded to the next integer since number of patients can be integer only).

where ARR= (Risk factor associated with the new drug group) — (Risk factor associated with the currently available drug)

So,

ARR= (165/1050)-(132/1044)

ARR= (0.157-0.126)

ARR= 0.031

NNT= 1/0.031

NNT=32.3

With regards to compensatory response to blood loss, the following sequence of events take place:

1. Decrease in venous return, right atrial pressure and cardiac output
2. Baroreceptor reflexes (carotid sinus and aortic arch) are immediately activated
3. There is decreased afferent input to the cardiovascular centre in medulla. This inhibits parasympathetic reflexes and increases sympathetic response
4. This results in an increased cardiac output and increased SVR by direct sympathetic stimulation. There is increased circulating catecholamines and local tissue mediators (adenosine, potassium, NO2)
5. Fluid moves into the intravascular space as a result of decreased capillary hydrostatic pressure absorbing interstitial fluid.

A slower response is mounted by the hypothalamus-pituitary-adrenal axis.
6. Reduced renal blood flow is sensed by the intra renal baroreceptors and this stimulates release of renin by the juxta-glomerular apparatus.
7. There is cleavage of circulating Angiotensinogen to Angiotensin I, which is converted to Angiotensin II in the lungs (by Angiotensin Converting Enzyme ACE)

Angiotensin II is a powerful vasoconstrictor that sets off other endocrine pathways.
8. The adrenal cortex releases Aldosterone
9. There is antidiuretic hormone release from posterior pituitary (also in response to hypovolaemia being sensed by atrial stretch receptors)
10. This leads to sodium and water retention in the distal convoluted renal tubule to conserve fluid
Fluid conservation is also aided by an increased amount of cortisol which is secreted in response to the increase in circulating catecholamines and sympathetic stimulation.

Soda-lime contains mostly calcium hydroxide (about 94%) and remaining sodium hydroxide.

CO2 + Ca(OH)2 → CaCO3 + H2O + heat
Here in this exothermic reaction, we can see that the production of calcium carbonate does not require heat.

When soda lime is allowed to dry with subsequent use of desflurane, isoflurane, and enflurane, it can lead to the generation of carbon monoxide.

Silica hardens the granules and can thus prevent disintegration.

The size of soda-lime granules is 4-8 mesh because it allows sufficient surface area for chemical reaction to occur without critically increasing the resistance to airflow.

The correct answer is the clotting cascade, which occurs via a positive feedback mechanism. As clotting factors are attracted to a site, their presence attracts further clotting factors. This continues until a functioning clot is formed.

This patient has presented with symptoms of hypothyroidism and symptoms include weight gain, lethargy, cold intolerance, dry skin, coarse hair and constipation. It can be treated by replacing the missing thyroid hormone with levothyroxine which is a synthetic version of thyroxine (T4).

Serum carbon dioxide (CO2) is controlled via a negative feedback mechanism as well. Chemoreceptors can detect when the serum CO2 is high, and send an impulse to the respiratory centre of the brain to increase the respiratory rate. As a result, more CO2 is exhaled which lowers the serum concentration.

Cortisol is also released according to a negative feedback mechanism. Cortisol acts on both the hypothalamus and the anterior pituitary. Its action serve to decrease the formation of corticotrophin releasing hormone (CRH) and adrenocorticotropic hormone (ACTH), respectively. CRH acts on the anterior pituitary to release ACTH. This then acts on the adrenal gland to cause the release of cortisol. Thus, inhibition of CRH and ACTH formation results in high levels of cortisol which inhibit its further release.

Blood pressure (BP) is controlled via a negative feedback mechanism. Low BP results in renin-angiotensin-aldosterone system (RAAS) activation. This leads to vasoconstriction and retention of salt and water which increased BP.
Blood sugar is controlled via a negative feedback mechanism. A rise in blood sugar causes insulin to be released. Insulin acts to transport glucose into the cell which lowers blood sugar.

T3 is produced by peripheral de-iodination of T4. It is more active than T4.

TBG, like most binding proteins, is increased in pregnancy. Because of this, measurement of free thyroid hormone concentration is more important than total.

T4 and T3 concentrations are decreased in Illness and starvation.

L-T4 that is the active molecule while D-T4 is inactive.

Half life (T½) is the time required to change the amount of drug in the body by one-half (or 50%) during elimination. The time course of a drug in the body will depend on both the volume of distribution and the clearance.

Extrapolating the values from the plasma concentration vs time:

Plasma concentration at 0 hours = 800 mcg/mL
Plasma concentration at 2 hours = 400 mcg/mL
Plasma concentration at 4 hours = 200 mcg/mL
Plasma concentration at 6 hours = 100 mcg/mL
Plasma concentration at 8 hours = 50 mcg/mL
Plasma concentration at 10 hours = 25 mcg/mL
Plasma concentration at 12 hours = 12.5 mcg/mL
Plasma concentration at 14 hours = 6.25 mcg/mL

Tracheal tubes are made of either disposable plastic or reusable red rubber.

The tube size refers to the internal diameter (ID) in mm which is marked on the outside of the tube (some manufacturers mark the external diameter on the outside).

Plastic tubes have a radiopaque line spanning the entire length of the tube, which allows their position to be identified on x-rays. The bevel located at the end of the tube is left-facing and oval in shape, which improves the view of the vocal cords during intubation.

Oxford tubes are L-shaped and have a bevel that faces posteriorly. They have thick walls that increase the external diameter, making for a wider internal diameter.

RAE (Ring, Adair, and Elwyn) tubes are preformed and can either be north or south facing and cuffed or uncuffed. The cuffed RAE tubes have one Murphy eye, whereas the uncuffed has two Murphy eyes. Uncuffed tubes are primarily used in paediatric anaesthesia and the two Murphy eyes ensure adequate ventilation- should the tube be too long.

Krebs’ cycle (tricarboxylic acid cycle or citric acid cycle) is a sequence of reactions to release stored energy through oxidation of acetyl coenzyme A (acetyl-CoA). Some of the products are carbon dioxide and hydrogen atoms.

The sequence of reactions, known collectively as oxidative phosphorylation, only occurs in the mitochondria (not cytoplasm).

The Krebs cycle can only take place when oxygen is present, though it does not require oxygen directly, because it relies on the by-products from the electron transport chain, which requires oxygen. It is therefore considered an aerobic process. It is the common pathway for the oxidation of carbohydrate, fat and some amino acids, required for the formation of adenosine triphosphate (ATP).

Pyruvate enters the mitochondria and is converted into acetyl-CoA. Acetyl-CoA is then condensed with oxaloacetate, to form citrate which is a six carbon molecule. Citrate is subsequently converted into isocitrate, alpha-ketoglutarate, succinyl-CoA, succinate, fumarate, malate and finally oxaloacetate.

The only five carbon molecule in the cycle is Alpha-ketoglutarate.

Standard wire gauge cannulas for intravenous and intraarterial use are available (SWG or G). The SWG is a former imperial unit (which requires metric conversion). The cross sectional area of wires is becoming more popular as a size measurement.

The number of wires that will fit into a standard hole template is referred to as SWG.

This standard sized hole can accommodate 22 thin wires side by side (each wire the diameter of a 22 gauge cannula)
In the same hole, 14 thicker wires would fit (each wire the diameter of a 14 gauge cannula)

While the diameter and thus radius of a parallel sided tube are the most important determinants of fluid flow rate, they are not commonly used to compare cannula sizes.

The circumference of French gauge (FG) catheters (urinary or chest drains) is measured. Sizes of double lumen tracheal tubes are FG. Internal diameter is used to measure single lumen tubes.

The response of cerebral blood flow (CBF) to hyperoxia (PaO2 >15 kPa, 113 mmHg), the cerebral oxygen vasoreactivity is less well defined. A study originally described, using a nitrous oxide washout technique, a reduction in CBF of 13% and a moderate increase in cerebrovascular resistance in subjects inhaling 85-100% oxygen. Subsequent human studies, using a variety of differing methods, have also shown CBF reductions with hyperoxia, although the reported extent of this change is variable. Another study assessed how supra-atmospheric pressures influenced CBF, as estimated by changes in middle cerebral artery flow velocity (MCAFV) in healthy individuals. Atmospheric pressure alone had no effect on MCAFV if PaO2 was kept constant. Increases in PaO2 did lead to a significant reduction in MCAFV; however, there were no further reductions in MCAFV when oxygen was increased from 100% at 1 atmosphere of pressure to 100% oxygen at 2 atmospheres of pressure. This suggests that the ability of cerebral vasculature to constrict in response to increasing partial pressure of oxygen is limited.

Increases in arterial blood CO2 tension (PaCO2) elicit marked cerebral vasodilation.

CBF increases with general anaesthesia, ketamine anaesthesia, and hypoviscosity.

There are different effects of electrocution and these can be shown in the table below.

Current Effect
1 mA Tingling
5 mA Pain
15 mA Tonic muscle contraction
50 mA Respiratory arrest
100 mA Ventricular fibrillation and cardiac arrest

Work up bias involves comparing the novel diagnostic test with the current standard test. A portion of the patients undergo the standard test while others undergo the new test as the standard test is costly. The result can be alteration in specify and sensitivity.

Selection bias is when randomisation is not achieved.

Attention bias refers to the person’s failure to consider various alternatives when he pre occupied by some other thoughts.

Instrument bias is related to the experience and extent of familiarization of the participating individuals with the test.

Co intervention bias is characterized by the groups receiving different co interventions.

Daptomycin alters the curvature of the membrane, which creates holes that leak ions. This causes rapid depolarization, resulting in loss of membrane potential. Thus it interferes with the outer membrane of gram-positive bacteria resulting in cell death.

Automated blood gas analysers are commonly used to analyse blood gas samples, and they measure specific components of the arterial blood gas sample, whether directly or indirectly.

The following are the components of arterial blood gas:

pH = measured (directly determined) acid-base balance of the blood

PaO2 = measured partial pressure of oxygen in arterial blood

PaCO2 = measured partial pressure of carbon dioxide in arterial blood

HCO3 = calculated (indirectly determined) concentration of bicarbonate in arterial blood

Base excess/deficit = calculated relative excess or deficit of base in arterial blood

SaO2 = calculated arterial oxygen saturation unless a co-oximetry is obtained, in which case it is measured

An epidemic is declared when the increase in a give disease is above a certain level in a specific interval of time.

An endemic is the general, usual level of a disease in a population at a particular time.

A pandemic is an epidemic that is spread across many countries and continents.

A preplanned preinduction strategy includes the consideration of various interventions designed to facilitate intubation should a difficult airway occur. Non-invasive interventions intended to manage a difficult airway include, but are not limited to: (1) awake intubation, (2) video-assisted laryngoscopy, (3) intubating stylets or tube-changers, (4) SGA for ventilation (e.g., LMA, laryngeal tube), (5) SGA for intubation (e.g., ILMA), (6) rigid laryngoscopic blades of varying design and size, (7) fibreoptic-guided intubation, and (8) lighted stylets or light wands.

Most supraglottic airway devices (SADs) are designed for use during routine anaesthesia, but there are other roles such as airway rescue after failed tracheal intubation, use as a conduit to facilitate tracheal intubation and use by primary responders at cardiac arrest or other out-of-hospital emergencies. Supraglottic airway devices are intrinsically more invasive than use of a facemask for anaesthesia, but less invasive than tracheal intubation. Supraglottic airway devices can usefully be classified as first and second generation SADs and also according to whether they are specifically designed to facilitate tracheal intubation. First generation devices are simply ‘airway tubes’, whereas second generation devices incorporate specific design features to improve safety by protecting against regurgitation and aspiration.

Work up bias involves comparing the novel diagnostic test with the current standard test. A portion of the patients undergo the standard test while others undergo the new test as the standard test is costly. The result can be alteration in specify and sensitivity.

Recall bias is specifically appropriate to the case control studies that is when ever the memories retrieved by the participants differ in accuracy.

Not publishing the results of a valid study just because they are negative or uninteresting can be termed as publication bias.

When information gathering is ill suited with respect to time i.e. collecting the data regarding a fatal disease many years after the death of its patients, it is termed as Late – look bias.

The case in point is an instance of lead time bias when upon comparing two tests, one is able to detect the condition earlier than the other but the overall outcome doesn’t change. There is a possibility that this will make the survival rates for the newer test look more promising.

The metabolism of drugs in the liver occurs in 3 phases

Phase I: This involves functionalization reactions, which are of 3 types, namely hydrolysis, oxidation and reduction reactions catalysed by the cytochrome P450 (CYP) enzymes.

Phase II: This involves conjugation or acetylation reactions. The goal is to create water soluble metabolites that can be excreted from the body.

The liver is the second largest organ. It’s smallest functional unit is the acinus which is divided into 3 zones:

Zone I (periportal): This zone receives the largest amount of oxygen supply as it is the closest to the blood vessels. It is the site of plasma protein synthesis.

Zone II (mediolobular): This is located between the portal triad and central vein.

Zone III (centrilobular): This is closest to the central vein and receives the least amount of oxygen supply.

Kupffer cells are specialized macrophages found in the periportal zone of the liver, and function to remove foreign particles and breakdown red blood cells via phagocytosis.

Ito cells are fat-storing liver cells found in the space of Disse. Their function is to take-uo, store and secrete retinoids, as well as manufacture and release proteins that make up the extracellular matrix.

The basilar artery is a large vessel that is formed by the union of the vertebral arteries at the junction of the medulla and pons. It lies in the pontine cistern and follows a shallow groove on the ventral pontine surface, extending to the upper border of the pons.

The basilar artery then bifurcates into the two posterior cerebral arteries that form part of the Circle of Willis.

Thiopental is a new British Approved Name for thiopentone and is thio-barbiturate.
Methohexitone is an oxy- barbiturate. Both thiopental and methohexitone are intravenous induction agents.

Ketamine cannot cause loss of consciousness in less than 30 seconds. At least 30 seconds is needed to cause loss of consciousness following intravenous administration.

Etomidate is an imidazole but it is not used in the Intensive Care unit for sedation because it has an antidepressant effect on the steroid axis.

The oxygen consumption rate (VO2) at rest is 3.5 ml/kg/minute (one metabolic equivalent or 1 MET).
3.86 ml/kg/minute thyrotoxicosis

Young children consume a lot of oxygen: around 7 ml/kg/min when they are born. The metabolic cost of breathing is higher in children than in adults, and it can account for up to 15% of total oxygen consumption. Similarly, an infant’s metabolic rate is nearly twice that of an adult, resulting in a larger alveolar minute volume and a lower FRC.

At term, oxygen consumption at rest can increase by as much as 40% (5 ml/kg/minute) and can rise to 60% during labour.

When compared to normal basal metabolism, sepsis syndrome increases VO2 and resting metabolic rate by 30% (4.55 ml/kg/minute). In septicaemic shock, VO2 decreases.

Dobutamine hydrochloride was infused into 12 healthy male volunteers at a rate of 2 micrograms per minute per kilogramme, gradually increasing to 4 and 6 micrograms per minute per kilogramme. Dobutamine was infused for 20 minutes for each dose. VO2 increased by 10% to 15%. (3.85-4.0 ml/kg/min).

As there is no brachiocephalic artery on the left side, the artery is entered by the catheter on the right side.

The brachiocephalic artery branches into the common carotid and the right subclavian artery, so the catheter is most likely to enter the right subclavian artery, or also possibly the right carotid.

During analytical stage a technique called stratification is used for controlling confounding variables. This technique involves sorting out the data into discernible groups.

The shaft of the humerus has two prominent features:
1. Deltoid tuberosity – attachment for the deltoid muscle
2. Radial or spiral groove – The radial nerve and profunda brachii artery lie in the groove

Mid-shaft fractures of the humerus usually occur after a direct blow to the upper arm, which can occur after a fall or RTAs. The most important clinical significance of a mid-shaft humeral fracture is an injury to the radial nerve. The radial nerve originates from the brachial plexus and has roots of C5-T1. It crosses the spiral groove on the posterior side of the shaft of the humerus.
On examination, the patient may have a wrist drop, loss or weakness of finger extension, and decreased or absent sensation to the posterior forearm, digits 1 to 3, and the radial half of the fourth digit.

The following parts of the humerus are in direct contact with the indicated
nerves:
Surgical neck: axillary nerve.
Radial groove: radial nerve.
Distal end of humerus: median nerve.
Medial epicondyle: ulnar nerve.

The following are the colour codes for medical gas cylinders:

Oxygen cylinder has a dark body with white shoulders.

Nitrous oxide is French blue. Air encompasses a grey body with dark and white quarters on the shoulders.

Entonox contains a French blue body with white and blue quarters on the shoulders.

Carbon dioxide barrels are grey in colour.

For the local anaesthetic base to be stable in solution, it is formulated as a hydrochloride salt. As such, the molecules exist in a quaternary, water-soluble state at the time of injection. However, this form will not penetrate the neuron. The time for onset of local anaesthesia is therefore predicated on the proportion of molecules that convert to the tertiary, lipid-soluble structure when exposed to physiologic pH (7.4).

The ionization constant (pKa) for the anaesthetic predicts the proportion of molecules that exists in each of these states. By definition, the pKa of a molecule represents the pH at which 50% of the molecules exist in the lipid-soluble tertiary form and 50% in the quaternary, water-soluble form. The pKa of all local anaesthetics is >7.4 (physiologic pH), and therefore a greater proportion the molecules exists in the quaternary, water-soluble form when injected into tissue having normal pH of 7.4.

Furthermore, the acidic environment associated with inflamed tissues favours the quaternary, water-soluble configuration even further. Presumably, this accounts for difficulty when attempting to anesthetize inflamed or infected tissues; fewer molecules exist as tertiary lipid-soluble forms that can penetrate nerves.