Crystalloids recommended for fluid resuscitation include 0.9% N saline and Hartmann’s solution(a physiological solution). 0.9% N. saline is not a physiological solution for the following reasons:

Compared with the normal range of 98-102 mmol/L, its chloride concentration is high (154 mmol/L)
It lacks calcium, magnesium, glucose and potassium
It does not have bicarbonate or bicarbonate precursor buffer necessary to maintain plasma pH within normal limits

There is a difference in the activity (concentration) of strong ions at a physiological pH. This imbalance can explain abnormalities of acid base balance. A normal strong ion difference (SID) is in the order of 40.

SID = ([Na+] + [K+] + [Ca2+] + [Mg2+]) – ([Cl-] + [lactate] + [SO42-])

This imbalance is made up with the weaker anions to maintain electrical neutrality.
Administration of a large volume of 0.9% normal saline during resuscitation results in excessive chloride administration and this impairs renal bicarbonate reabsorption. The SID of 0.9% normal saline is 0 (Na+ = 154mmol/L and Cl- = 154mmol/L = 154 – 154 = 0). A large volume of NS will decrease the plasma SID causing an acidosis.

Other causes of a hyperchloremic acidosis are:

Diabetic ketoacidosis
Total Parenteral Nutrition
Overdose of ammonium chloride and hydrochloric acid
Gastrointestinal losses of bicarbonate like in diarrhoea and pancreatic fistula
Proximal renal tubular acidosis with failure of bicarbonate reabsorption

Ketamine is usually used as a racemic mixture, i.e. (R/S)-ketamine. For over 20 years, use of the more potent (S)-enantiomer by anaesthesiologists has become a preferred option due to the assumption of increased anaesthetic and analgesic properties, a more suitable control of anaesthesia, and of an improved recovery from anaesthesia.

The use of ketamine in anaesthesia and psychiatry may be accompanied by the manifestation of somatic and especially psychomimetic symptoms such as perceptual disturbances, experiences of dissociation, euphoria, and anxiety.

This sudden change in pulse rate is due to the oculocardiac reflex. It is a >20% reduction in pulse rate as a result of placing pressure directly on the eyeball. The reflex arc has an afferent and efferent arm:

The afferent (sensory) arm: The trigeminal nerve (CN V)

The efferent arm: The vagus nerve (CN X)

The most appropriate action is to ask the surgeon to stop retraction of the extraocular muscles, Assess for hypoxia, and give 100% oxygen if indicated.

Atropine of glycopyrrolate can be administered to counteract the reflex, and also prevent any further vagal reflexes.

Administration of fentanyl may increase patient’s risk of bradycardia and sinus arrest in this case.

Adrenaline is not indicated here as other treatment options will provide sufficient relief from arrhythmia.

The Delphi technique was developed in the 1950s and is a widely used and accepted method for achieving convergence of opinion concerning real-world knowledge solicited from experts within certain topic areas. Choosing the appropriate subjects is the most important step in the entire process because it directly relates to the quality of the results generated, despite this, there is no exact criterion currently listed in the literature concerning the selection of Delphi participants.

Therefore, due to the potential scarcity of qualified participants and the relatively small number of subjects used in a Delphi study, the ability to achieve and maintain an ideal response rate can either ensure or jeopardize the validity of a Delphi study.

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.

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.

Ligamentum venosum is an anterior relation of the liver: The ligamentum venosum, the fibrous remnant of the ductus venosus of the fetal circulation, lies posterior to the liver. It lies in the fossa for ductus venosus that separates the caudate lobe and the left lobe of the liver.

The portal triad contains three important tubes: 1. Proper hepatic artery 2. Hepatic portal vein 3. Bile ductules It also contains lymphatic vessels and a branch of the vagus nerve.

The bare area of the liver is a large triangular area that is devoid of any peritoneal covering. The bare area is attached directly to the diaphragm by loose connective tissue. This nonperitoneal area is created by a wide separation between the coronary ligaments.

The porta hepatis is a fissure in the inferior surface of the liver. All the neurovascular structures (except the hepatic veins) and hepatic ducts enter or leave the liver via the porta hepatis. It contains the sympathetic branch to the liver and gallbladder and the parasympathetic, hepatic branch of the vagus nerve. The caudate lobe (segment I) lies in the lesser sac on the inferior surface of the liver between the IVC on the right, the ligamentum venosum on the left, and the porta hepatis in front

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.

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.

The Mapleson A (Magill) and coaxial version of the Mapleson A system (Lack circuit) are more efficient for spontaneous breathing than any of the other Mapleson circuits. The fresh gas flow (FGF) required to prevent rebreathing is slightly greater than the alveolar minute ventilation (4-5 litres/minute). This is delivered to the patient through the outer coaxial tube and exhaust gases are moved to the scavenging system through the inner tube. In the Lack circuit, the expiratory valve is located close to the common gas outlet away from the patient end. This is the main advantage of the Lack circuit over the Mapleson A circuit.

The Mapleson E circuit is a modification of the Ayres T piece and the FGF required to prevent rebreathing is 1.5-2 times the patient’s minute volume.

The Bain circuit is the coaxial version of the Mapleson D circuit.

The FGF for spontaneous respiration to avoid rebreathing is 160-200 ml/kg/minute.

The FGF for controlled ventilation to avoid rebreathing is 70-100 ml/kg/min.

Cardiac output = stroke volume x heart rate

Left ventricular ejection fraction = (stroke volume / end diastolic LV volume ) x 100%

Stroke volume = end diastolic LV volume – end systolic LV volume

Pulse pressure = Systolic Pressure – Diastolic Pressure

Systemic vascular resistance = mean arterial pressure / cardiac output
Factors that increase pulse pressure include:
-a less compliant aorta (this tends to occur with advancing age)
-increased stroke volume

The right coronary artery supplies the right ventricle, the right atrium, the sinoatrial (SA) node and the atrioventricular (AV) node.

The circumflex artery originates from the left coronary artery and is supplied by it.

Number needed to harm are a measure of the impact of a treatment or intervention that is often used to communicate results to patients, clinicians, the public and policymakers. It states how many patients need to be treated for one additional patient to experience an adverse outcome (e.g. a death). It is calculated as the inverse of the absolute risk reduction. It can equally well be applied to harmful outcomes as well as beneficial ones, where it becomes numbers needed to treat (NNT) instead.

In this way, they are both calculated the same but NNT usually refers to a therapeutic treatment whereas NNH refers to a risk-factor for disease.

The sacral hiatus is shaped by incomplete midline fusion of the posterior elements of the distal portion of S4 and S5. This inverted U shaped space is covered by the posterior aspect of the sacrococcygeal membrane and is an important landmark in caudal anaesthetic block. Distal most portion of the dural sac and the sacral hiatus usually terminate between levels S1 and S3. The dural sac ends at the level of S2 in adults and S3 in children.

An equilateral triangle is formed between the apex of the sacral hiatus and the posterior superior iliac spines. This triangle is used to determine the location of the sacral hiatus during caudal anaesthetic block.

The ileocolic artery is the terminal branch of the superior mesenteric artery. It supplies:
1. terminal ileum
2. proximal right colon
3. cecum
4. appendix (via its branch of the appendicular artery)

As veins accompany arteries in the mesentery and are lined by lymphatics, high ligation is the norm in cancer resections—the ileocolic artery branches off the SMA near the duodenum.

Mesenteric ischemia is ischemia of the blood vessels of the intestines. It can be life-threatening, especially if the small intestine is involved.

The inferior mesenteric artery originates 3-4 cm above the bifurcation of the abdominal aorta.
The left colic artery branches off the inferior mesenteric artery to supply the following:
– distal 1/3 of the transverse colon
– descending colon

At approximately the left colic flexure (splenic flexure), a transition occurs in the blood supply of the GI tract. The SMA supplies the proximal part to the flexure, and the IMA supplies the part distal to the flexure. This is why the left colic flexure is a watershed area and is prone to ischemia exacerbated by atherosclerotic changes or hypotension. The dominant arterial supply of the splenic flexure is usually from the left colic artery, but it may also get collaterals from the left branch of the middle colic artery.

The AMA and PMA do not exist.
The splenic artery directly supplies the spleen and has branches that supply the stomach and the pancreas.
The proximal two-thirds of the transverse colon is supplied by the middle colic artery, a branch of the SMA.

When a person forcefully expires against a closed glottis, changes occur in intrathoracic pressure that dramatically affect venous return, cardiac output, arterial pressure, and heart rate. This forced expiratory effort is called a Valsalva maneuver.

Initially during a Valsalva, intrathoracic (intrapleural) pressure becomes very positive due to compression of the thoracic organs by the contracting rib cage. This increased external pressure on the heart and thoracic blood vessels compresses the vessels and cardiac chambers by decreasing the transmural pressure across their walls. Venous compression, and the accompanying large increase in right atrial pressure, impedes venous return into the thorax. This reduced venous return, and along with compression of the cardiac chambers, reduces cardiac filling and preload despite a large increase in intrachamber pressures. Reduced filling and preload leads to a fall in cardiac output by the Frank-Starling mechanism. At the same time, compression of the thoracic aorta transiently increases aortic pressure (phase I); however, aortic pressure begins to fall (phase II) after a few seconds because cardiac output falls. Changes in heart rate are reciprocal to the changes in aortic pressure due to the operation of the baroreceptor reflex. During phase I, heart rate decreases because aortic pressure is elevated; during phase II, heart rate increases as the aortic pressure falls.

When the person starts to breathe normally again, the intrathoracic pressure declines to normal levels, the aortic pressure briefly decreases as the external compression on the aorta is removed, and heart rate briefly increases reflexively (phase III). This is followed by an increase in aortic pressure (and reflex decrease in heart rate) as the cardiac output suddenly increases in response to a rapid increase in cardiac filling (phase IV). Aortic pressure also rises above normal because of a baroreceptor, sympathetic-mediated increase in systemic vascular resistance that occurred during the Valsava.

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.

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.

Opioid receptors are a large family of seven transmembrane domain receptors. They are of four types:

1) Delta opioid receptor

2) Mu opioid receptor

3) Kappa opioid receptor

4) Orphan receptor-like 1

They contain about 372-400 amino acids and thus their molecular weight is different.

Opioid receptor activation reduces the intracellular cAMP formation and opens K+ channels (mainly through µ and δ receptors) or suppresses voltage-gated N-type Ca2+ channels (mainly κ receptor). These actions result in neuronal hyperpolarization and reduced availability of intracellular Ca2+ which results in decreased neurotransmitter release by cerebral, spinal, and myenteric neurons (e.g. glutamate from primary nociceptive afferents).

However, other mechanisms and second messengers may also be involved, particularly in the long-term

This patient has been shifted to a sulfonylurea drug whose most common side effect is hypoglycaemia. Similar symptoms can arise in a patient on insulin too. The signs and symptoms are consistent with a hypoglycaemic attack and include tachycardia, altered consciousness, and behaviour. This needs to be treated as an emergency with rapid correction of the blood glucose level using glucose or IV 20% dextrose.

In a hypoglycaemic attack, the body undergoes stress and releases hormones to increase blood glucose levels. These include:
Glucagon
Cortisol
Adrenaline

Adrenaline or epinephrine is the hormone responsible for this patient’s condition and is primarily produced in the medulla of the adrenal gland. It functions primarily to raise cardiac output and raise blood glucose levels in the blood.

Alpha-cells of the islets of Langerhans produce the hormone glucagon, which has opposing effects to insulin.

Follicular cells of the thyroid gland produce and secrete thyroid hormones. Thyroid hormones can cause similar symptoms, but it is unlikely with the patient’s medical history.

Post-ganglionic neurons of the sympathetic nervous system use norepinephrine as a neurotransmitter. Adrenaline can be made in these cells, but it is not their primary production site.

Zona fasciculata of the adrenal cortex is the main site for the production of cortisol.

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 Beers criteria, a US set of criteria for good prescribing in the older patient, preclude the use of metoclopramide in Parkinson’s disease. The Adverse Reactions Register of the UK Committee on Safety of Medicines (CSM) for the years 1967 to 1982 contained 479 reports of extrapyramidal reactions in which metoclopramide was the suspected drug; 455 were for dystonic-dyskinetic reactions, 20 for parkinsonism and four for tardive dyskinesia. Effects can occur within days of initiation of treatment and may take months to wear off.

Other antiemetics are available, such as cyclizine (Valoid), domperidone and ondansetron, which would be more appropriate to use in those with Parkinson’s disease.

Cyclizine is a piperazine derivative with histamine H1 receptor antagonist and anticholinergic activity. It is used for the treatment of nausea, vomiting, (particularly opioid-induced vomiting), vertigo, motion sickness, and labyrinthine disorders.

Prochlorperazine is an antipsychotic known to cause tardive dyskinesia, tremor and parkinsonian symptoms and is therefore likely to exacerbate Parkinson’s disease. Prochlorperazine is not favoured for older patients because of the increased risk of stroke and transient ischaemic attack (TIA).

Droperidol and phenothiazine are also potent antagonists on D2 receptors and must also be avoided.

Propranolol is a nonselective beta-blocker with a half-life of 3 to 6 hours.

Since it is lipid-soluble it crosses the blood-brain barrier and causes Central Nervous System side effects like sedation, nightmares, and depression.

They are contraindicated in asthma, Congestive heart failure, and diabetes.

It has a large volume of distribution with no intrinsic sympathomimetic action.

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.

The usual method of calculating the dose of a drug to be given to patients of normal weight is to use total body weight (TBW). This is because the lean body weight (LBW) and ideal body weight (IBW) dosing scalars are similar in these patients.

Because the LBW and fat mass do not increase in proportion in patients with morbid obesity, this is not the case. Drugs that are lipid soluble, such as propofol or thiopentone, can cause a relative overdose. Lean body mass is a better scalar in these situations.

Suxamethonium has a small volume of distribution, so the dose is best calculated using the TBW to ensure optimal and deep intubating conditions. The higher dose was justified because these patients’ plasma cholinesterase activity was elevated.

Other scalars include:

The dose of highly lipid soluble drugs like benzodiazepines, thiopentone, and propofol can be calculated using lean body weight (LBW). The formula LBW = IBW + 20% can be used on occasion.

Fentanyl, rocuronium, atracurium, vecuronium, morphine, paracetamol, bupivacaine, and lidocaine are all administered with LBW.

Formulas can be used to calculate the ideal body weight (IBW). There are a number of drawbacks, including the fact that patients of the same height receive the same dose, and the formulae do not account for changes in body composition associated with obesity. Because IBW is typically lower than LBW, administering a drug based on IBW may result in underdosing. The body mass index (BMI) isn’t used to calculate drug dosage directly.

A passive leg raise can lead to transient increases in blood pressure and stroke volume as it increased the amount of venous return to the heart. Venous return increases in this situation as it transfers a larger volume of blood from the lower limbs to the right heart. It therefore mimics a fluid challenge. However its effects are short lasting and often lead to minimal increases in blood pressure. It therefore should not be used to treat shock in isolation. The passive leg raise is useful in determining the likelihood that a patient with shock will respond to fluid resuscitation.

Stroke volume (via a cardiac monitor) and/or pulse pressure (via an arterial line) should be measured to assess the effects of a passive leg raise. An increase in stroke volume by 9% or in pulse pressure by 10% are considered indicative of fluid responsiveness.

Blood that enters the ventricles during diastole causes stretching of sarcomeres within cardiac muscle. The extent to which they stretch is proportional to the strength of ventricular muscle contraction. Therefore, the venous return (amount of blood returned to the heart) is proportional to stroke volume. The end diastolic volume is determined by venous return and is also proportional to stroke volume.

Cardiac muscle contraction strength is dependent on the action of adrenaline and noradrenaline, but these hormones contribute to cardiac contractility, not to stroke volume.

68% of the population will be found in one standard deviation (SD) above plus one SD below the mean. Two SDs above plus two SDs below the mean will include 95% of the population.

The median can be greater or less than the mean as it is simply the mid point of the data after the data is arranged. Half the data are above and half below the median .

The mode is a true score, unlike the mean or the median. It is the most common score or the score obtained from the largest number of subjects in any given data.

Monosynaptic reflexes is a type of reflex arc providing direct communication between motor and sensory innervation in a muscle. It occurs very quickly as it arises and ends in the same muscle. Examples include: biceps reflex, brachioradialis reflex, extensor digitorum reflex, triceps reflex, Achilles reflex and patellar reflex.

Polysynaptic reflexes facilitates contraction and inhibition in muscle by providing communication between multiple muscles.

Selegiline is a monoamine oxidase inhibitor. Inhibition of monoamine oxidase leads to increased levels of norepinephrine and serotonin in the central nervous system.

Pethidine, also known as meperidine, is a strong agonist at the mu and kappa receptors. It inhibits pain neurotransmission and blocks muscarinic-specific actions.

Administering opioid analgesic is relatively contraindicated to individuals taking monoamine oxidase inhibitors. This is because of the high incidence of serotonin syndrome, which is characterized by fever, agitation, tremor, clonus, hyperreflexia and diaphoresis. Onset of symptoms is within hours, and the treatment is mainly through sedation, paralysis, intubation and ventilation.

The clinical findings are more consistent with Serotonin syndrome rather than exacerbation of Parkinson’s. Parkinson’s Disease (PD) exacerbations are defined as patient-reported or caregiver-reported episodes of subacute worsening of PD motor function in 1 or more domains (bradykinesia, tremor, rigidity, or PD-related postural instability/gait disturbance) that caused a decline in functional status, developed over a period of < 2 months, did not fluctuate with medication timing, and are not caused by intentional adjustments of PD medications by the treating neurologist. Malignant hyperthermia usually occurs within minutes of administration of a volatile anaesthetic, such as halothane, or succinylcholine. There is massive release of calcium from the sarcoplasmic reticulum, leading to fever, acidosis, rhabdomyolysis, trismus, clonus, and hypertension. In sepsis, it more common for patients to present with hypotension rather than hypertension.