The midgut gives rise to the appendix.
At week 6, the caecal diverticulum appears and is the precursor for the cecum and vermiform appendix. The cecum and appendix undergo rotation and descend into the right lower abdomen. The appendix can take up various positions:
1. Retrocecal appendix: behind the cecum
2. Retrocolic appendix: behind the ascending colon
3. Pelvic appendix: appendix descends into the pelvis

The appendix grows in length so that at birth, it is long and worm-shaped, or vermiform. After birth, the caecal wall grows unequally, and the appendix comes to lie on its medial side.

The midgut develops into the distal duodenum, jejunum, ileum, cecum, appendix, ascending colon, and proximal 2/3 of the transverse colon.

Rifampicin is a potent inducer of liver cytochrome enzymes. Other enzyme inducers are:
Carbamazepine
Sodium valproate
Phenytoin
Phenobarbitone

Randomisation can be used to provide control over the confounding variables during the design stage of a study however during analytical stage a technique called stratification is used for controlling confounding variables. Since the question asks for the information that is factually incorrect.

Entonox is a gas that consists of 50% oxygen and 50% Nitrous oxide. Nitrous oxide is sometimes used for anaesthetics but in this combination, it works as a short-acting painkiller.

Under normal working conditions, it exists only in gaseous form in a cylinder. The gauge pressure of a full Entonox cylinder is 137 bar.

Entonox cylinders should be stored horizontally at a temperature above 100 C

Pseudocritical temperature and pseudocritical pressure can be defined as the molal average critical temperature and pressure of mixture components. In other words, the pseudo-critical temperature is the temperature at which the two gases separate. The pseudo-critical temperature of Entonox is approximately -5.50 C

Low molecular weight heparin (LMWH) creates a complex by binding to antithrombin. This complex binds with and inactivates factor Xa.

There is less risk of bleeding with LMWH because it binds less to platelets, endothelium and von Willebrand factor.

LMW binds Xa more readily. The shorter chains are less likely to bind both antithrombin and thrombin.

There is need for monitoring in renal impairment because LMHW is excreted in the urine (and partly by hepatic metabolism)

LMWH have been shown to be as efficacious as unfractionated heparin. It is also safer and have improved inpatient stay and reduced hospital cost.

There is minimum mixing of blood passing through the vessels.

The cerebral hemispheres are supplied by arteries that make up the Circle of Willis. The Circle of Willis is formed by the anastomosis of the two internal carotid arteries and two vertebral arteries. It lies in the subarachnoid space within the basal cisterns that surround the optic chiasma and infundibulum.

Each half of the circle is formed by:
1. Anterior communicating artery
2. Anterior cerebral artery
3. Internal carotid artery
4. Posterior communicating artery
5. Posterior cerebral arteries and the termination of the basilar artery

The circle and its branches supply; the corpus striatum, internal capsule, diencephalon, and midbrain

After the carotid body, the thyroid gland is the second most richly vascular organ in the body.

The global blood flow to the thyroid gland can be measured using:
1. Colour ultrasound sonography
2. Quantitative perfusion maps using MRI of the thyroid gland using an arterial spin labelling (ASL) method.

This table shows the blood flow to various organs of the body at rest:
Organ Blood Flow(ml/minute/100g)
Hepatoportal 58
Kidney 420
Brain 54
Skin 13
Skeletal muscle 2.7
Heart 87
Carotid body 2000
Thyroid gland 560

Total body water (TBW) is about 50% to 70% in adults depending on how much fat is present. ECF is relatively contracted in an obese person.

The simple rule is 60-40-20. (60% of weight = total body water, 40% of body weight is ICF and 20% is ECF)

For this woman, the total body water is 36 litres (0.6 × 60). ECF is 12 litres (1/3 of TBW) and 24 litres (2/3 of TBW) is intracellular fluid .

Sodium concentration is approximately 135-145 mmol/L in the ECF.

The ECF is made up of both intravascular and extravascular fluid and plasma proteins is found in both.

Elimination of phenytoin from the body follows first-order kinetics. This means that the rate of elimination is proportional to plasma concentration.

The rate of elimination can be described by the equation:

C = C0·e-kt

Where:

C = drug concentration
C0 = drug concentration at time zero (extrapolated)
k = Rate constant
t = Time

Enzyme systems become saturated when phenytoin concentrations exceed the normal range and elimination of the drug becomes zero-order. At this point, the drug is metabolised at a fixed rate and metabolism is independent of plasma concentration.

Aspirin and ethyl alcohol are other drugs that behave this way.

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

The inguinal triangle of Hesselbach’s is an important clinical landmark on the posterior wall of the inguinal canal. It has the following relations:
Inferiorly – medial third of the inguinal ligament
Medially – lower lateral border of the rectus abdominis
Laterally – inferior epigastric vessels

Direct inguinal hernia is when the bowel bulges directly through the abdominal wall. These hernias usually protrude through Hesselbach’s triangle

The anterior cerebral artery supplies the midline portion of the frontal lobe and the superior medial parietal lobe of the brain. It also supplies the front four-fifths of the corpus callosum and provides blood to deep structures such as the anterior limb of the internal capsule, part of the caudate nucleus, and the anterior part of the globus pallidus.

The cerebral hemispheres are supplied by arteries that make up the Circle of Willis. The Circle of Willis is formed by the anastomosis of the two internal carotid arteries and two vertebral arteries.

Clinically, the internal carotid arteries and their branches are often referred to as the anterior circulation of the brain. The anterior cerebral arteries are connected by the anterior communicating artery. Near their termination, the internal carotid arteries are joined to the posterior cerebral arteries by the posterior communicating arteries, completing the cerebral arterial circle around the interpeduncular fossa, the deep depression on the inferior surface of the midbrain between the cerebral peduncles.

The middle cerebral artery supplies part of the frontal, temporal and parietal lobes.

The posterior cerebral artery supplies the occipital lobe.

The international system of units, or system international d’unites (SI) is a collection of measurements derived from expanding the metric system.

There are seven base units, which are:

Metre (m): a unit of length
Second (s): a unit of time
Kilogram (kg): a unit of mass
Ampere (A): a unit of electrical current
Kelvin (K): a unit of thermodynamic temperature
Candela (cd): a unit of luminous intensity
Mole (mol): a unit of substance.

Mivacurium is metabolised primarily by plasma cholinesterase at an In vitro rate of about 70% that of succinylcholine. Mivacurium is contraindicated in patients with genetic and acquired plasma cholinesterase deficiencies.

The clearance of atracurium is by Hoffman degradation and ester hydrolysis in the plasma and is independent of both hepatic and renal function.

Rocuronium is eliminated primarily by the liver after metabolises to a less active metabolite, 17-desacetyl-rocuronium. Its duration of action is not affected much by renal impairment.

Vecuronium undergoes hepatic metabolism into 3-desacetyl-vecuronium which has 50-80% the activity of the parent drug. It undergoes biliary (40%) and renal excretion (30%). The aminoglycoside antibiotics possess additional neuromuscular blocking activity. The potency of gentamicin > streptomycin > amikacin. Calcium can be used to reverse the muscle weakness produced by gentamicin but not neostigmine. When vecuronium and gentamycin are given together the effect on neuromuscular blockade is synergistic.

Significant residual neuromuscular block 2 hours after the administration of these drugs is unlikely In this scenario.

Any recovery from neuromuscular blockade with suxamethonium in a patient with deficiency of plasma cholinesterase demonstrate four twitches on a train of four count.

Selection bias is when randomisation is not achieved and is often a result of in efficient recruiting method.

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

Measurement bias can be characterized by gathering of information in a manner that is distorted.

When the participants of a research study are recruited from the hospitals rather than the general population, its called Berkson Bias.

Confounding bias is the major player here because in this case the effects of smoking can be masked behind and can be read as outcomes of lower socio economic status. This extraneous factor (Smoking), distorts the founding.

Pupil size is reduced by the pupillary light reflex and during accommodation for near vision. In the pupillary light reflex, light that strikes the retina is processed by retinal circuits that excite W-type retinal ganglion cells. These cells respond to diffuse illumination. The axons of some of the W-type cells project through the optic nerve and tract to the pretectal area, where they synapse in the olivary pretectal nucleus. This nucleus contains neurons that also respond to diffuse illumination. Activity of neurons of the olivary pretectal nucleus causes pupillary constriction by means of bilateral connections with parasympathetic preganglionic neurons in the Edinger-Westphal nuclei. The reflex results in contraction of the pupillary sphincter muscles in both eyes, even when light is shone into only one eye.

Also known as the “product limit estimate’’, the Kaplan-Meier survival plot is used to estimate the true survival function from the collected data.

Using this plot, probabilities of occurrence of an event at a certain point in time can be computed. The successive probabilities are multiplied by any earlier computed probabilities to get the final estimate. For a given population, the survival probability at any particular time on the plot = (number of subjects living at the start – number of subjects who died)/number of subjects living at the start.

The description of a scatter plot is a graphical representation using Cartesian coordinates to display values for more than two variables for data set. It is used for to assess the relationship between 2 different variables.

The patient in the case has a fluid volume requirement of 30 mL/kg/day. His basic electrolyte requirement per day is:

Sodium at 2 mmol/kg/day x 110 = 220 mmol/day
Potassium at 1 mmol/kg/day x 110 = 110 mmol/day

His energy requirement per day is:

35 kcal/kg/day x 110 kg = 3850 kcal/day

One gram of glucose in fluid can provide approximately 4 kilocalories.

The following are the electrolyte components of the different intravenous fluids:

Fluid Na (mmol/L) K (mmol/L)
0.9% Normal saline (NSS) 154 0
0.45% NSS + 5% dextrose 77 0
0.18% NSS + 4% dextrose 30 0
Hartmann’s 131 5
5% dextrose 0 0

1000 mL of 5% dextrose has 50 g of glucose

Option B is inadequate for his sodium and caloric requirements (30 mmol of Na+ and 560 kcal). It is adequate for his K+ requirement (120 mmol of K+).

Option C is in excess of his Na+ requirement (462 mmol of Na+). Moreover, it does not provide any K+ replacement.

Option D is inadequate for his caloric requirement (600 kcal) and K+ requirement (60 mmol of K+). Moreover it does not provide any Na+ replacement.

Option E is in excess of his Na+ requirement (393 mmol of Na+), and is inadequate for his potassium requirement (15 mmol of K+)

Option A has adequate amounts for his Na+ (231 mmol of Na+) and K+ (120 mmol of K+) requirements. It is inadequate for his caloric requirement (600 kcal).

Arterial pressure waveforms is an invasive form of monitoring cardiac parameters. It provides a lot of information on the performance of the heart from different sections, including:

Cardiac measurements:

Heart rate
Systolic pressure
Diastolic pressure
Mean arterial pressure
Pulse pressure
Change in pulse amplitude corresponding to respiratory changes
Slope of anacrotic limb associated with aortic stenosis

From the shape of the arterial waveform displayed:

Slope of anacrotic limb represents aortic valve and LVOT flow
Indications of aortic stenosis (AS): Slurred wave, collapsing wave
Rapid systolic decline in LVOTO
Bisferiens wave in HOCM
Low dicrotic notch in states with poor peripheral resistance
Position and quality of dicrotic notch as a reflection of the damping coefficient

For this question, the upstroke slope of the pressure wave is indicative of myocardial contractility and is mathematically represented as:

dP/dt, which represents a change of pressure with regards to time.

The coeliac axis refers to one of the splanchnic arteries located within the abdomen.

It arises from the aorta almost horizontally at the level of the T12 vertebrae

Bulky, greasy stools are associated with improper digestion that can be expected if the pancreas loses its exocrine function. This is common in long-term chronic pancreatitis but since this is the patient’s first presentation with such symptoms, this complication is unlikely.

Peripheral neuropathy is a common complication of chronic diabetes but has been reported with cases of chronic pancreatitis too.

Abdominal distention with shifting dullness is a classic symptom of underlying ascites. Ascites is a complication of many diseases but it is not common with the acute first-time presentation of pancreatitis.

Option E: This points towards abdominal obstruction but in the absence of the more common symptoms, nausea and bilious vomiting, this is unlikely.

Option A: Grey Turner’s sign is the pooling of blood in the retroperitoneal space between the last rib and the top of the hip. The pancreas is a retroperitoneal organ and inflammation of the pancreas can cause retroperitoneal haemorrhage. The sign takes 24-48 hours to develop and can predict a severe attack of acute pancreatitis. The patient has presented with acute pancreatitis due to his history of high alcohol intake, and acute on chronic is unlikely as this is his first presentation. He also has low blood pressure and an increased heart rate, which suggest blood loss with acute pancreatitis.

Since an arterial pressure transducer, and every other measuring apparatus, is prone to errors due to offset and gradient drifts, regular calibration is required to maintain accuracy of the instrument. The two-point calibration pressure values of 0 mmHg and 200 mmHg are within the physiologic range and can best compensate for the gradient drift.

Carbon dioxide (CO2), is a carbonic gas made up of two dissimilar atoms, namely one carbon atom and two oxygen atoms. Capnography is a technique used to measure carbon dioxide during a respiratory cycle, and it consists in calculating the concentration of the partial pressure of CO2, through the absorption of the infrared light, namely that CO2 absorbs infrared radiation at a wavelength of 4.28 µm.

End-tidal CO2 (ETCO2), referring to the level of the carbon dioxide released at the end of an exhaled breath, is required to be continuously monitored, especially in ventilated patients, as it is a sensitive and a non invasive technique that provides immediate information about ventilation, circulation, and metabolism functions. ETCO2 is normally lower than the arterial partial pressure and varies between 0.6 and 0.7 kPa.

There are two methods used to measure carbon dioxide. The sidestream capnometer method samples gases at a set flow rate (150-200 mL/min) from a sampling area through small diameter tubing, and the mainstream analyser method that uses a direct measurement of the patient exhaled CO2 by a relatively large and heavy sensors. Sidestram method allows the analysis of multiple gases and anaesthetic vapours comparing to the mainstream method that does not allow the measurement of other gases.

The measurements of GFR are done using renally inert indicators like inulin, where passive rate of filtration at the glomerulus = rate of excretion. Normal value is about 180 litres per day.

GFR is altered by renal blood flow but blood flow does not need to be measured.

The reabsorption of Na leads to a low excretion rate and low urine concentration and therefore its use as an indicator would lead to an erroneously LOW GFR.

If there is tubular secretion of any solute, the clearance value will be higher than that of inulin. This will be either due to tubular reabsorption or the solute not being freely filtered at the glomerulus.

pH is the negative log to the base 10 of hydrogen ion concentration:

So, what power produces the answer?

pH = – log10 [H+]

Making [H+] the subject:

[H+] = 10-pH

Substituting, [H+] = 10-7

One nanomole = 1 x 10-9 or 0.000000001

10-7 = 1x 0.0000001 or 10 x 0.00000001 or 100 x 0.000000001

100 nanomole

Tests are used to confirm the presence of a particular disease. However the results can be misleading at times since most of the tests have some limitations associated with them.
Sensitivity is the correct term that refers to the probability of a positive test. The others are explained below:

False Positive rates refer to the proportion of the patients who don’t have the condition being detected as positive.

False Negative rates refer to the proportion of the patients who have the condition being detected as negative (like the 20% of the patients that went undetected by the Ca-125 test).

Specificity describes the ability of a test to detect and pick up people without the disease. Absolute risk ratio compares the rate of two separate outcomes.

The commonest and most likely cause of a gradual rise in end-tidal CO2 (EtCO2) occurring during anaesthesia in a spontaneously breathing patient is hypoventilation. This occurs from the respiratory depressant effects of the opioid and sevoflurane.

Malignant hyperthermia should be sought if the EtCO2 shows further progressive rise.

Causes of rebreathing and a rise in the baseline of the capnograph can be caused by exhausted soda lime and inadequate fresh gas flow into the Bain circuit.

A sudden rise in EtCO2 can be caused deflation of the tourniquet.

The most common cause of hypoparathyroidism is injury or removing the parathyroid glands. They can be injured accidentally during surgery to remove the thyroid as they are located posterior to the thyroid gland.

A result of both low parathyroid hormone and low calcium is likely to mean that the parathyroid glands are not responding to hypocalcaemia. The hypocalcaemia can cause confusion, and the stay in the hospital is likely to refer to her surgery.

While a parathyroid adenoma is fairly common and can cause hypoparathyroidism, it much more likely causes hyperparathyroidism.

Chronic kidney disease is likely to cause hypocalcaemia, which would increase parathyroid hormone production in an attempt to increase calcium levels, causing hyperparathyroidism. Vitamin D is activated by the kidneys and then binds to calcium to be absorbed in the terminal ileum so that a deficiency would cause hyperparathyroidism.

Staphylococcus aureus infection is the most likely cause.

Surgical site infections (SSI) occur when there is a breach in tissue surfaces and allow normal commensals and other pathogens to initiate infection. They are a major cause of morbidity and mortality.

SSI comprise up to 20% of healthcare associated infections and approximately 5% of patients undergoing surgery will develop an SSI as a result.
The organisms are usually derived from the patient’s own body.

Measures that may increase the risk of SSI include:
-Shaving the wound using a single use electrical razor with a disposable head
-Using a non iodine impregnated surgical drape if one is needed
-Tissue hypoxia
-Delayed prophylactic antibiotics administration in tourniquet surgery, patients with a prosthesis or valve, in clean-contaminated surgery of in contaminated surgery.

Measures that may decrease the risk of SSI include:
1. Intraoperatively
– Prepare the skin with alcoholic chlorhexidine (Lowest incidence of SSI)
-Cover surgical site with dressing

In contrast to previous individual RCT’s, a recent meta analysis has confirmed that administration of supplementary oxygen does not reduce the risk of wound infection and wound edge protectors do not appear to confer benefit.

2. Post operatively
Tissue viability advice for management of surgical wounds healing by secondary intention

Use of diathermy for skin incisions
In the NICE guidelines the use of diathermy for skin incisions is not advocated. Several randomised controlled trials have been undertaken and demonstrated no increase in risk of SSI when diathermy is used.

Prostacyclin is a strong vasodilator. It is administered as an intravenous infusion for critical ischemia. Commercially, it is available as sodium epoprodtenol.

Atrial Natriuretic peptide (ANP) hormone secreted from the atria, kidney, and neural tissues. It primarily acts on renal vessel to maintain normal blood pressure and reduce plasma volume by: increasing the renal excretion of salt and water, glomerular filtration rate, vasodilation, and by increasing the vascular permeability. It also inhibits the release of renin and aldosterone.

Indoramin is an alpha-adrenoceptor blocking agent. which act selectively on post-synaptic-alpha adrenoreceptor, leading to decease in peripheral resistance.

Angiotensin II is a vasoconstrictor, causing high sodium retention. It also increases the secretion of antidiuretic hormone (ADH) and aldosterone level.