Bupivacaine is used to decrease sensation in a specific area. It is injected around a nerve that supplies the area, or into the spinal canal’s epidural space.

The maximum volume of 0.5% bupivacaine that should be administered to a 10kg child is 5 ml

The Weibull distribution are used to describe various types of observed failures of the components. it is used in reliability and survival analysis.

Regression Analysis is used to measure the relationship between among two or more variable. It determines the effect of independent variables on the dependent variables.

Student t-test is one of the most commonly used method to test the hypothesis. It determines the significant difference between the means of two different groups.

A time series is a collection of observations of well-defined data obtained at regular interval of time.

Kaplan-Meier estimator is used to estimate the survival function from lifetime data. It can be derived from maximum likelihood estimation of hazard function. It is most likely used to measure the fraction of patient’s life for a certain amount of time after treatment.

Approximately 70% of the heart’s ATP requirement is met by cardiac mitochondria through beta-oxidation of fatty acids at rest. The remaining 30% is supplied by glucose.

Amino acids and ketones, in the presence of ketoacidosis, may supply at most 10% of the ATP requirement. And, when in high levels, lactate may also contribute to the ATP requirement of the heart, particularly during moments of high muscular activity.

The correlation coefficient gives us the idea about relation between two parameters. i.e. to what extent change in parameter A could prompt a change in parameter B. The numerical value of correlation coefficient could not be greater than 1.

The costal elements of the seventh cervical vertebrae form projections known as cervical ribs, which are present in approximately 0.5% – 1 % individuals.

A cervical rib commonly comprises of a head, neck and tubercle. The body of the rib varies from person to person. It extends into the posterior triangle of the neck, where it is either free anteriorly, or attached to the first rib / sternum.

Patients with a cervical rib mostly are asymptomatic and it is usually diagnosed as an incidental finding on chest x-ray. However, in some cases, the subclavian artery and the lower trunk of the brachial plexus are compressed where they pass over the cervical rib. This leads to a condition known as ”neurovascular compression syndrome,” in which these neurovascular structures are compressed between the cervical rib and scalenus anterior.

The most common cause of neurogenic symptoms in approximately 80% of the patients with cervical rib is neck trauma.

In most cases, the tingling, numbness and impaired circulation to the upper limb appears only after puberty. This is because the neck elongates, and the shoulders droop slightly.

Sugammadex is a modified cyclodextrin that works as an aminosteroid neuromuscular blocking (nmb) reversal agent. By encapsulating each molecule in the plasma, it rapidly reverses rocuronium and, to a lesser extent, vecuronium-induced neuromuscular blockade. Consequently, a  concentration gradient favours the movement of these nmb agents away from the neuromuscular junction.  Pancuronium-induced neuromuscular blockade at low levels has also been reversed.

By inhibiting voltage-dependent calcium channels at the neuromuscular junction, antibiotics in the aminoglycoside group potentiate neuromuscular blocking agents. This can be reversed by giving calcium but not neostigmine or sugammadex.

Sugammadex will not reverse the effects of mivacurium, which belongs to the benzylisoquinolinium class of drugs.

A phase II or desensitisation block occurs when the motor end-plate becomes less sensitive to acetylcholine as a result of an overdose or repeated administration of suxamethonium. The use of neostigmine has been shown to be effective in reversing this weakness.

The epiploic foramen (foramen of Winslow or aditus to the lesser sac) is found behind the free right border of the lesser omentum. A short, 3 cm slit serves as the entrance to the lesser sac from the greater sac.

The epiploic foramen has the following boundaries:
Anteriorly: hepatoduodenal ligament, the bile duct (anteriorly on the right), the hepatic artery (anteriorly on the left), and the portal vein (posteriorly) together with nerves and lymphatics
Superiorly: the peritoneum of the posterior layer of the hepatoduodenal ligament runs over the caudate process of the liver
Posteriorly: inferior vena cava
Floor: upper border of the first part of the duodenum
The anterior and posterior walls of the foramen are normally
apposed, which partly explains why patients can develop large fluid
collections isolated to the greater or lesser sac

Rapid control of the hepatic artery and portal vein can be obtained by compression of the free edge of the lesser omentum (a ‘Pringle’ manoeuvre), which is a potentially useful technique in liver trauma and surgery.

The peritoneal cavity is made up of the omentum, the ligaments and the mesentery.

The section of the peritoneum responsible for tethering organs to the posterior abdominal wall is the mesentery.

These tethered organs are classified as intraperitoneal, and these include the stomach, spleen, liver, first and fourth parts of the duodenum, jejunum, ileum, transverse, and sigmoid colon.

Retroperitoneal organs are located posterior to the peritoneum and include: the rest of the duodenum, the ascending colon, the descending colon, the middle third of the rectum, and the remainder of the pancreas

The posterior inferior cerebellar artery is the largest branch arising from the distal portion of the vertebral artery which forms the basilar artery. It is one of the arteries responsible for providing blood supply to the brain’s cerebellum.

The labyrinthine artery (auditory artery) is a long and slender artery which arises from the basilar artery and runs alongside the facial and vestibulocochlear nerves into the internal auditory meatus.

The posterior cerebellar artery is one of two cerebral arteries supplying the occipital lobe with oxygenated blood. It is usually bigger than the superior cerebellar artery. It is separated from the vessel near its origin by the oculomotor nerve.

Marsh (adult) model, when used with children caused over-estimation of plasma concentration. To address this issue Kataria et al developed a three-compartmental model for propofol in children. The pharmacokinetic models used by Target controlled infusion (TCI) systems are used to calculate the relative sizes of the central (vascular), vessel-rich peripheral, and vessel-poor peripheral compartments. The relative volumes of these compartments are different in young children when compared to adults.

Kataria, therefore, is the correct option as described above.

The Maitre model is a three-compartmental model for alfentanil TCI.

The Marsh model describes a propofol TCI model for adults

The Minto model applies to TCI remifentanil.

The Schnider model is also an adult model for propofol that incorporates age and lean body mass as covariates.

CBF is defined as the blood volume that flows per unit mass per unit time in brain tissue and is typically expressed in units of ml blood/100 g tissue/minute. The normal average CBF in adults human is about 50 ml/100 g/min, with lower values in the white matter (,20 ml/100 g/min) and greater values in the gray matter (,80 ml/100 g/min).

Low CBF levels between 30-40 ml/100 g/min may begin to show poor prognostic EEG. EEG findings consistently associated with a poor outcome are isoelectric EEG, low voltage EEG, and burst suppression (specifically burst suppression with identical bursts), as well as the absence of EEG reactivity.

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

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

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

The neuromuscular blocking agent is likely to be filtered and not reabsorbed by the renal tubules due to an exclusion process.

Neuromuscular blocking agents that contain one or more quaternary nitrogen atoms are polar and ionised. As a result, the molecules have low lipid solubility, low membrane diffusion capacity, and low distribution volume.

It’s unlikely that a compound with three quaternary nitrogen atoms is an ester. Its high polarity would prevent molecules from moving quickly into tissues.

When drugs have a low hepatic extraction ratio (0.3), the venous and arterial drug concentrations are nearly identical. The liver is not the primary site of drug metabolism.

Therefore:

Changes in liver blood flow have no effect on clearance.
Protein binding, intrinsic metabolism, and excretion are all very sensitive to changes in clearance.
When taken orally, there is no first-pass metabolism.

There is no reason for the lungs to eliminate any neuromuscular blocking agent.

Spirometry measures the total volume of air that can be forced out in one maximum breath, that is the total lung capacity (TLC), to maximal expiration, that is the residual volume (RV).

It is conducted using a spirometer which is capable of measuring lung volumes using techniques of dilution.

During spirometry, the following measurements can be determined:
Forced vital capacity (FVC)/vital capacity (VC): The maximum volume of air exhaled in one single forced breathe.
Forced expiratory volume in one second (FEV1)
FEV1/FVC ratio
Peak expiratory flow (PEF): the maximum amount of air flow exhaled in one blow.
Forced expiratory flow (mid expiratory flow): the flow at 25%, 50% and 75% of FVC
Inspiratory vital capacity (IVC): The maximum volume of air inhaled after a full total expiration.

Anatomical dead space is measured using a single breath nitrogen washout called the Fowler’s method.

Residual volume and total lung capacity are both measured using the body plethysmograph or helium dilution

The functional residual capacity is usually measured using a nitrogen washout or the helium dilution technique.

Penicillinase is a narrow spectrum ?-lactamase that opens the ?-lactam ring and inactivates Penicillin G and some closely related congeners. The majority of Staphylococci and some strains of gonococci, B. subtilis, E. coli, and a few other bacteria produce penicillinase.

N. meningitidis is sensitive to penicillin and less than 20% resistance is found in pseudomonas.

Pituitary macroadenoma is a benign tumour with growth larger than 10mm (those under 10mm are called microadenoma)

Compression of optic chiasm by pituitary adenoma is responsible for causing visual field defects like bitemporal hemianopia, optic neuropathy.

The autonomic nervous system is divided into the sympathetic and parasympathetic nervous system. They are anatomically and physiologically different.

The sympathetic nervous system arises from the thoracolumbar outflow (T1-L5 ) at the lateral horns of grey matter of the spinal cord. Their preganglionic neurones are usually short myelinated and synapse in ganglia lateral to the vertebral column and have acetyl choline (Ach) as the neurotransmitter. Their postganglionic neurones are longer and unmyelinated and synapse with effector organ where the neurotransmitter is either adrenaline or noradrenaline.

The outflow of the parasympathetic nervous system is craniosacral. The cranial part originates from the midbrain and medulla (cranial nerves III, VII, IX and X) and the sacral outflow is from S2, S3 and S4. Their preganglionic neurones are usually long myelinated and synapse in ganglia close to the target organ and has Ach as its neurotransmitter. The unmyelinated postganglionic neurones is shorter and they synapse with effector organ. The neurotransmitter here is also Ach.

Both sympathetic and parasympathetic preganglionic neurons are cholinergic. Only the postganglionic parasympathetic neurons are cholinergic.

Key Point: While finding out confidence intervals, standard errors are used. Standard error and Standard deviation are two distinct entities and should not be confused.

For 99.7% confidence interval, you can find the range as follows:

Multiply the standard error by 3.

Subtract the answer from mean value to get the lower limit.

Add the answer obtained in step 1 from the mean value to get the upper limit.

The range turns out to be 1-13 mmol/L.

For a confidence interval of 68%, multiply the standard error with 1 and repeat the process. The range found for this interval is 3-11 mmol/L.

For a 95% confidence interval. Standard Error is multiplied by 1.96 which gives us the limit ranging from 3.08 to 10.92 mmol/L which could be approximated to 3-11 mmol/L.

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.

The portal vein arises from the splenic and mesenteric veins, and is the biggest vessel in the portal venous system, accounting for about 75% of the hepatic blood flow.

It is responsible for draining blood from parts of the gastrointestinal system, the spleen, the pancreas and the gallbladder into the liver.

The formula for calculating air: oxygen entrainment ratio is given as :
100% − FiO2 = air/oxygen entrainment ratio
Since FiO2 − 21% and the entrainment ratio is already known. Substituting the values in the equation: x = FiO2.

100 − x = 9
x − 21
100 − x = 9(x − 21)
100 − x = 9x − 189
10x = 289
x = 289/10
x = 28.9%

Bucks fascia refers to the layer of loose connective tissue, nerves and blood vessels that encapsulates the penile erectile bodies, the corpa cavernosa and the anterior part of the urethra, including the entirety of the spongiose part of the urethra.

It runs with the external spermatic fascia and the penile suspensory ligament.

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

Oxygen delivery depends on 2 variables.
1) Content of oxygen in blood
2) Cardiac output

Oxygen content (arterial) = (Hb (g/dL) x 1.39 x SaO2 (%) ) + (0.023 x PaO2 (kPa))

Oxygen content (mixed venous) = (Hb (g/dL) x 1.39 x mixed venous saturation) + (0.023 x mixed venous partial pressure of oxygen in kPA)

Huffner’s constant = 1.39 = 1g of Hb binds to 1.39 ml of O2

Oxygen delivery DO2 (ml/min) = 10 x Cardiac output (L/min) x Oxygen content
Normally 1000ml/min

Oxygen consumption VO2 (ml/min) = 10 x Cardiac output (L/min) x Difference in arterial and mixed venous oxygen content
Normally 250 ml/min

Oxygen extraction ratio (OER) = VO2/DO2
Normally approximately 25%

Flowmeters measure the rate at which a specific gas, that the flowmeter has been calibrated for, passes through. This calibration is done at room temperature and standard atmospheric pressure with an accuracy of +/- 2%.

Reading the flowmeter is done from the top of a bobbin (the midpoint of a ball). Oxygen is the last gas to be added downstream to the mixture delivered to the back bar as a safety feature. This prevents delivery of a hypoxic mixture.

Inaccurate flow measurements occur when the bobbin sticks to the inside wall of the flowmeter. Stannic oxide has been used as a successful antistatic substance thus, reducing the aforementioned risk.

Carbon dioxide being easily delivered is found on some older machines, but those attached flowmeters are limited by a maximum flow of 500 ml /min. Thus avoiding the delivery of a hypercarbic mixture.

The sternocleidomastoid muscle divides the neck into anterior and posterior triangles on both sides of the neck.

The posterior triangle has the following boundaries:
anteriorly – sternocleidomastoid muscle
posteriorly – trapezius
roof – investing layer of deep cervical fascia
floor – prevertebral fascia overlying splenius capitis, levator scapulae, and the scalene muscles

The contents of the posterior triangle are:
1. fat
2. lymph nodes (level V)
3. accessory nerve
4. cutaneous branches of the cervical plexus – greater auricular nerve, transverse cervical nerve, lesser occipital nerve, supraclavicular nerve (A major branch of this plexus is the phrenic nerve, which arises from the anterior divisions of spinal nerves C3-C5)
5. inferior belly of omohyoid
6. branches of the thyrocervical trunk (transverse cervical and suprascapular arteries)
7. third part of the subclavian artery
8. external jugular vein

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 minimal alveolar concentration (MAC) is the concentration of an inhalation anaesthetic agent in the lung alveoli required to stop a response to the surgical stimulus in 50% of the patient.

Following factors don’t affect the MAC of the inhaled anaesthetic agents:

Gender, acidosis, alkalosis, hypothyroidism, hyperthyroidism, body weight, serum potassium level, and the duration of the anaesthesia.

MAC increase in children, elevated temperature, high metabolic rate, sympathetic increase and chronic alcoholism.

MAC decrease in low temperature, low oxygen level, old age, hypotension (<40 mmHg), depressant drugs e.g. opioids and low level of catecholamines; alpha methyl dopa. Carbon dioxide O2 at the pressure > 120mmHg is being used in anesthetic-Hinkman as an additive effect to decrease MAC, however, increase concentration of CO2 activates the sympathetic system resulting the MAC increases.