It’s a minute volume divider – True
The Manley MP3 ventilator is classed as a minute volume divider. The entire fresh gas flow or minute volume is delivered to the patient, having been divided into readily set tidal volumes.

Can efficiently ventilate patients with poor pulmonary compliance – False
Ventilating patients with poor pulmonary compliance is not easily achieved, which makes it an unsuitable ventilator for a modern ICU.

Can generate tidal volume up to 1500ml – False
It can generate tidal volumes up to 1000 ml (not 1500 ml), and the inflation pressure can be adjusted by sliding a weight along a rail.

Functions like a Mapleson A system during spontaneous ventilation – False
The ventilator functions like a Mapleson D breathing system (not Mapleson A) during spontaneous ventilation.

Has three sets of bellows – False
The fresh gas flow drives the ventilator which allows rapid detection of gas supply failure. It has two sets of bellows (not three) and three unidirectional valves.

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

The taeniae coli are the three outer muscular bands of the cecum, ascending colon, transverse colon, and descending colon.

The taeniae coli converge at the base of the appendix in the cecum where they form a complete longitudinal layer. In the ascending and descending colon, the bands are located anteriorly, posteromedially, and posterolateral.

The membranous urethra is the shortest part of the urethra and the least dilatable part of it.

This is as a result of it being surrounded by the external urethral sphincter which is made up of striated muscle and controls voluntary urine flow from the bladder to the urethra.

Awareness during general anaesthesia is a frightening experience, which may result in serious emotional injury and post-traumatic stress disorder.

The incidence of awareness during general anaesthesia with current anaesthetic agents and techniques has been reported as 0.2-0.4% in nonobstetric and noncardiac surgery, as 0.4% during caesarean section, and as 1.5% in cardiac surgery.

The incidence during major trauma surgery is higher. Incidence of recall has been reported to be as high as 11-43% in major trauma cases.

The concentration of solute particles per litre (mosm/L) = the osmolarity of a solution. Changes in water content, ambient temperature, and pressure affects osmolarity. The osmolarity of any solution can be calculated by adding the concentration of key solutes in it.

Individual manufacturers of crystalloids and colloids may have different absolute values but they are similar to these.

0.45% N. Saline with 5% glucose:
Tonicity – hypertonic
Osmolarity – 405 mosm/L
Kilocalories (kCal) – 107

0.9% N. Saline:
Tonicity – isotonic
Osmolarity – 308 mosm/L
Kilocalories (kCal) – 0

5% Dextrose:
Tonicity – isotonic
Osmolarity – 253 mosm/L
Kilocalories (kCal) – 170

Gelofusine (154 mmol/L Na, 120 mmol/L Cl):
Tonicity – isotonic
Osmolarity – 274 mosm/L
Kilocalories (kCal) – 0

Hartmann’s solution:
Tonicity – isotonic
Osmolarity – 273 mosm/L
Kilocalories (kCal) – 9

Incidence tells us about the number of new cases that have been reported while prevalence gives us the idea of existing cases.

In this particular instance, the parameter of the study i.e. the total number of cases has not changed thus the prevalence of the disease remains same. Although, more cases have been reported in the second instance as a result of which incidence has increased.

The abdominal aorta begins at the level of the body of T12 near the midline, as a continuation of the thoracic aorta. It descends and bifurcates at the level of L4 into the common iliac arteries.

The branches of the abdominal aorta (with their vertebra level) are:
1. Inferior phrenic arteries: T12 (upper border)
2. Coeliac artery: T12
3. Superior mesenteric artery: L1
4. Middle suprarenal arteries: L1
5. Renal arteries: Between L1 and L2
6. Gonadal arteries: L2 (in males, it is the testicular artery, and in females, the ovarian artery)
7. Inferior mesenteric artery: L3
8. Median sacral artery: L4
9. Lumbar arteries: Between L1 and L4

The superior phrenic artery branches from the thoracic aorta.

Type I – immediate hypersensitivity reaction

Examples are: Atopy, urticaria, Anaphylaxis, Asthma( IgE mediated).

Type II – Antibody mediated cytotoxic reaction

Examples are: Autoimmune haemolytic anaemia, Thrombocytopenia( IgM or IgG mediated).

Type III – Immune complex mediated reaction

Examples are: Serum sickness,SLE – IgG., Farmers lungs, rheumatoid arthritis

Type IV – Delayed hypersensitivity reaction

Examples are: Contact dermatitis, drug allergies.

Type V – Autoimmune

Graves’
Myasthenia – IgM or IgG.

Creatinine clearance is a test used to approximate the glomerular filtration rate (GFR) as an assessment of kidney function.

Creatinine is formed during the breakdown of dietary sources of meat and skeletal muscle. It is secreted at a consistent concentration and pace into the body’s circulation, and is easily filtered across the glomerulus without being reabsorbed or metabolized by the kidney.

It is represented mathematically as:
Creatinine clearance (CL) = U x V/P
where,
U: Urinary creatinine concentration (mg/mL)
V: Volume of urine (mL/min)
P: Plasma creatinine concentration (mg/mL)

Therefore, in this case:
CL: 1.25 x 1 = 125mL/min
0.1

Barbiturates are derived from barbituric acid, which itself is nondepressant, but appropriate side-chain substitutions result in CNS depressant activity that varies in potency and duration with carbon chain length, branching, and saturation.

Oxybarbiturates retain an oxygen atom on number 2-carbon atom of the barbituric acid ring.

Thiobarbiturates replace this oxygen atom with a sulphur atom, which confers greater lipid solubility. Generally speaking, a substitution such as sulphuration that increases lipid solubility is associated with greater hypnotic potency and more rapid onset, but shorter duration of action.

Addition of a methyl group to the nitrogen atom of the barbituric acid ring, as with oxybarbiturate methohexital, also results in a compound with a short duration of action.

The ions found in higher concentrations intracellularly than outside the cells are:

ATP
AMP
Potassium
Phosphate, and
Magnesium Adenosine diphosphate (ADP)

Sodium is a primarily extracellular ion.

The vertebral (spinal) column is the skeletal central axis made up of approximately 33 bones called the vertebrae.

Cervical disc herniations occur when some or all of the nucleus pulposus extends through the annulus fibrosus. The most commonly affected discs are the C5-C6 and C6-C7 discs. Each vertebrae has a corresponding nerve root which arises at a level above it. This means that a hernation of the C5-C6 disc will cause a compression of the C6 nerve root.

The foramen transversarium is a part of the transverse process of each cervical vertebrae, however, the vertebral artery only runs through the C1-C6 foramen transversarium.

The costal facets are the point of joint formation between a rib and a vertebrae. As such, they are only present on the transverse processes of T1-T10.

The lumbar vertebrae do not form a joint with the ribs, nor do they possess a foramina in their transverse process.

Intervertebral discs are thickest in the cervical and lumbar regions of the spinal column. However, there are no discs between C1 and C2.

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.

Venous cutdown is a surgical procedure when venous access is difficult, and other procedures like the Seldinger technique, ultrasound-guided venous access, and intraosseous vascular access have failed.

The vein of choice for venous cutdown is the long/great saphenous vein. It is part of the superficial venous collecting system of the lower extremity. It is the preferred vein as the long saphenous vein has anatomic consistency and is superficially located at the ankle anterior to the medial malleolus. It is also the most commonly used conduit for cardiovascular bypass operations.

Origin- in the foot at the confluence of the dorsal vein of the first digit and the dorsal venous arch of the foot
Route- runs ANTERIOR to the medial malleolus and travels up in the medial leg and upper thigh.
Termination: in the femoral vein within the femoral triangle

Regarding the other options:
The short saphenous vein passes posterior to the lateral malleolus.
The dorsalis pedis vein accompanies the dorsalis pedis artery on the anterior foot.
The posterior tibial vein is part of the deep venous system accompanying the posterior tibial artery. There is no significant sural vein (there is a sural nerve), but the sural veins accompany the sural arteries and drain to the popliteal vein.

The arterial cannula inserted should have parallel walls in order to reduce the risk of interruption of blood flow to distal limbs.

It is essential that the monitor used to display the arterial pressure waves has a frequency capacity of 0.5-40Hz. This is because the pressure waves are a combination of different sine waves of varying frequencies and amplitudes.

The diameter of the catheter is directly proportional to the natural frequency which is the frequency at which the system responsible for monitoring the waves resonates and amplifies the signals. This should be at least ten fold in comparison to the fundamental frequency. The diameter of the catheter is also inversely proportional to the square root of the system compliance, the tubing length and the fluid density within the system.

The presence of an air bubble, a clot or an easily malleable diaphragm and tube can result in wave damping. Increased damping will cause a reduction in the systolic pressure, and an increase in diastolic pressure. The maximum damping value of an appropriate monitoring system would be 0.64.

A rigid, non-malleable diaphragm and tubing can cause a resonance within the system. This resonance will result in an increase in the systolic pressure and a reduction in the diastolic pressure

Cardiac conduction

Phase 0 – Rapid depolarization. Opening of fast sodium channels with large influx of sodium

Phase 1 – Rapid partial depolarization. Opening of potassium channels and efflux of potassium ions. Sodium channels close and influx of sodium ions stop

Phase 2 – Plateau phase with large influx of calcium ions. Offsets action of potassium channels. The absolute refractory period

Phase 3 – Repolarization due to potassium efflux after calcium channels close. Relative refractory period

Phase 4 – Repolarization continues as sodium/potassium pump restores the ionic gradient by pumping out 3 sodium ions in exchange for 2 potassium ions coming into the cell. Relative refractory period

Refractometers measure the degree to which the light changes direction, called the angle of refraction. A refractometer takes the refraction angles and correlates them to refractive index (nD) values that have been established. Using these values, you can determine the concentrations of solutions.

An echocardiogram provides real-time visualisation of cardiac structures. The ejection fraction (EF) is normally measured using this system.

The ejection fraction (EF) can be deduced mathematically if the patient’s end-diastolic volume (EDV), end-systolic volume (ESV) and stroke volume (SV) are known, as:

SV = EDV – ESV, and

EF = SV/EDV x 100

The normal range for EF is >55-70%.

For this patient,

SV= 40 – 30 = 10 mL, therefore

EF = 10/40 x 100 = 25%

Breathing system is an assembly of components which connects patient’s airway to anaesthesia machine through which controlled composition of gas mixture is dispensed. It delivers gas to the patient, removes expired gas and controls the temperature and humidity of the inspired mixture. It allows spontaneous, controlled, or assisted respiration. It may also provide ports for gas sampling, airway pressure, flow and volume monitoring.

Breathing systems have been classified by Conway and Mapleson.
Conway suggested a functional classification:
– Circuits requiring a CO2 absorber
– Circuits not requiring a CO2 absorber

William Mapleson designated varying arrangements of breathing system components (masks, breathing tubes, fresh gas flow inlets, adjustable pressure-limiting valves, and reservoir bags) as Mapleson A-E circuits.
Mapleson A: Arranged as FGF inlet, reservoir bag, APL valve, mask.
In this circuit, because the reservoir bag is between the FGF inlet valve and the APL valve, expired gas from the patient may re-enter the system and fill the reservoir bag during controlled ventilation. This is the most efficient system for spontaneous breathing as the FGF must only be equal to a patient’s minute ventilation to prevent rebreathing.

Mapleson B: Arranged as reservoir bag, FGF inlet, APL valve, mask.
In this circuit, the FGF inlet is closer to the APL valve, which helps prevent the rebreathing concern in the Mapleson A circuit as above during controlled ventilation.

Mapleson C: Arranged as reservoir bag, FGF inlet, APL valve, mask.
In this circuit, the arrangement is the same as the Mapleson B circuit. However, this circuit is shorter as it does not contain elongated corrugated tubing. This circuit also has the FGF inlet close to the APL valve to aid in preventing rebreathing.

Mapleson D: Arranged as reservoir bag, APL valve, FGF inlet, and mask.
In this circuit, the arrangement interchanges the FGF inlet and APL valve of the Mapleson A circuit. This system prevents rebreathing by directing FGF towards the APL valve rather than towards the patient during exhalation.

Mapleson E: Arranged as corrugated tubing, FGF inlet, and mask.
In this circuit, there is no reservoir bag and no APL valve. Given the inability to alter the pressure of the circuit, this is ideal for spontaneously ventilating neonates or paediatric patients where low-pressure ventilation is desired. The system prevents rebreathing, similar to the Mapleson D circuit.

Jackson Rees later modified the Mapleson E by adding an open ended bag, which has since become known as the Mapleson F.
Mapleson F: Arranged as APL valve directly connected to reservoir bag, corrugated tubing, FGF inlet, and mask.
The system prevents rebreathing similarly to Mapleson D by directing FGF towards the APL valve.

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.

The inferior mesenteric artery supplies blood to the hindgut, which includes the sigmoid colon.

Note that during high anterior resection of distal sigmoid colon tumours, the inferior mesenteric artery is ligated, interrupting blood supply.

The branches of the internal iliac artery, particularly the middle rectal branch, are essential in retaining vascularity of the rectal stump.

The Drager Oxylog® 1000 is a pneumatically powered, time-dependent, volume-titrated emergency ventilator with a pressure limit. It is compatible with CD cylinder oxygen. The CD cylinder is a strong and lightweight cylinder usually composed of aluminium or Kevlar. The internal cylinder volume is 2 litres, and the pressure of a full cylinder is 230 bar. The volume of the full cylinder is determined by applying Boyle’s law: P1 × V1 = P2 × V2

Where:
P1= pressure of a full cylinder (230 bar)
V1= volume of oxygen at that pressure (2 litres)
P2= final pressure (1 bar), and
V2= volume of oxygen in the full cylinder.

Substituting values into the equation:

230 × 2 = 1 x V2
V2 = 460 litres. The flow of fresh gas is 4 litres/minute + 1 litre/minute required by the control, making a total of 5 litres/minute. The amount of time it takes for the cylinder to empty would be the total volume of oxygen in the full cylinder divided by the amount of oxygen expelled per minute: 460/5 = 92, meaning it would take 92 minutes for the cylinder to empty.

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

When there is capillary leakage as seen in dependent oedema or ascites, oncotic pressure becomes a problem.

The intracellular sodium concentration is very sensitive to the extracellular sodium concentrations. When there is an imbalance, osmosis occurs resulting in shifts in water between the two compartments.

The microvascular endothelium relies upon osmosis and other processes as it is not freely permeable to water.

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).

Epoprostenol has a half-life of only 42 seconds and has rapid offset. It is used for the treatment of pulmonary hypertension.

Aspirin inhibits the COX enzyme irreversibly. It inhibits thromboxane synthesis but does not inhibit the enzyme thromboxane synthetase.

Ticlopidine, clopidogrel and prasugrel act as irreversible antagonists of P2 Y12 receptor of Adenosine Diphosphate (ADP). These drugs interfere with the activation of platelets by ADP and fibrinogen. Both aspirin and clopidogrel act irreversibly so they are not correct.

Paclitaxel is a long-acting antiproliferative agent used for the prevention of restenosis (recurrent narrowing) of coronary and peripheral stents and is not the correct answer.

Tirofiban has the next shortest duration of action after epoprostenol. If epoprostenol is not given in the question, it would be the best answer.

Dopamine (DA) is a dopaminergic (D1 and D2) as well as adrenergic ? and ?1 (but not ?2 )agonist.

The D1 receptors in renal and mesenteric blood vessels are the most sensitive: i.v. infusion of a low dose of DA dilates these vessels (by raising intracellular cyclic adenosine monophosphate).

Moderately high doses produce a positive inotropic (direct ?1 and D1 action + that due to NA release), but the little chronotropic effect on the heart.

Vasoconstriction (?1 action) occurs only when large doses are infused.

At doses normally employed, it raises cardiac output and systolic BP with little effect on diastolic BP. It has practically no effect on nonvascular ? and ? receptors; does not penetrate the blood-brain barrier – no Central nervous system effects.

Dopamine is less arrhythmogenic than adrenaline

Regarding dopamine part of the dose is converted to Noradrenaline in sympathetic nerve terminals.

The superior laryngeal nerve gives off two branches: the sensory branch which is the internal laryngeal nerve, and the motor branch which is the external laryngeal nerve.

The recurrent laryngeal nerve (RLN) rises from the vagus nerve which supplies the intrinsic muscles of the larynx, except the cricothyroid muscles.

The internal jugular vein is found on both sides of the neck and collects blood from the brain, superficial regions of the face, and neck. It drains into the right atrium.

It is a continuation of the sigmoid sinus and begins in the posterior cranial fossa and exits the skull via the jugular foramen.
It runs within the carotid sheath as it descends in the neck and is accompanied by the vagus nerve posteriorly and the common carotid anteromedially.

The hypoglossal nerve emerges from the hypoglossal canal medial to the internal carotid artery and the internal jugular vein and ninth, tenth, and eleventh cranial nerves.

The internal jugular vein crosses anterior to the thoracic duct on the left side.