Dose response curves are plotted as % response to drug against Logarithm of drug concentration. The graph is usually sigmoid shaped.

Any drug that has high affinity and high intrinsic activity is likely an agonist. A drug with high affinity but no intrinsic activity will act as an antagonist. Displacement of an agonist also depends on the relative concentrations of the two drugs at the receptor sites.

Maximal response may be achieved by activation of a small proportion of receptor sites.

The process used in the study is Delphi method. This method kicks off with an open ended questionnaire and uses its responses as a survey instrument for the next round in which each of the participants is asked to rate the items that the investigators have summarized on the basis of the data collected in the first round.

Any disagreement is further discussed in phases to come on the basis of information obtained from previous phases.

The temperature above which a gas cannot be liquefied no matter how much pressure is applied is its critical temperature. The critical temperature of nitrous oxide is 36.5°C

The minimum pressure that causes liquefaction is the critical pressure of that gas.

The Poynting effect refers to the phenomenon where mixing of liquid nitrous oxide at low pressure with oxygen at high pressure (in Entonox) leads to formation of gas of nitrous oxide.

There is no relevance of molecular weight to this question. it does not change with phase of a substance.

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.

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

So,

ARR= (24/120)-(60/240)

ARR= 0.2-0.25

ARR= 0.05 (Numerical Value)

ARR= 5%

99.7% of the values within 3 standard deviations of the mean.

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

1. Multiply the standard error by 3.

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

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

For a confidence interval of 68%, multiply the standard error with 1 and repeat the process. For a 95% confidence interval, Standard Error is multiplied by 1.96 to get the interval.

The inguinal canal is a passage in the lower anterior abdominal wall just above the inguinal ligament. It transmits the following structures:
1. genital branch of genitofemoral nerve
2. ilioinguinal nerve
3. spermatic cord (males only)
4. round ligament of the uterus (females only)

The ilioinguinal is a direct branch of the first lumbar nerve. The ilioinguinal nerve enters the inguinal canal via the abdominal musculature (and not through the deep (internal) inguinal ring) and exits through the superficial (or external) inguinal ring.

The openings for the other nerves in the answer options are:
Sciatic nerve – exits the pelvis via the greater sciatic foramen
Obturator nerve – descends into pelvis via the obturator foramen
Femoral nerve – descends from the abdomen through the pelvis behind the inguinal canal

The Iliohypogastric nerve also arises from the first lumbar root with the ilioinguinal nerve but pierces the transversus abdominis muscle posteriorly, just above the iliac crest, and continues anteriorly between the transversus abdominis and the internal abdominal oblique muscles.

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

Breathing 100% oxygen for three minutes will provide the best reservoir of oxygen during apnoea by oxygenating the functional residual capacity (FRC).

Sitting at 45 degrees might increase the FRC and improve oxygen reserve but not compared with 100% oxygenation.

The following table compares the oxygen reserves in the body following pre-oxygenation with room air and 100% oxygen:

Compartment Factors Room air (mL) 100% O2 (mL)
Lung FAO2, FRC 630 2850
Plasma PaO2, DF, PV 7 45
Red blood cells Hb, TGV, SaO2 788 805
Myoglobin – 200 200
Interstitial space – 25 160

FAO2 = alveolar fraction of oxygen.
FRC = Functional residual capacity.
PaO2 = partial pressure of oxygen dissolved in arterial blood
DF = dissolved form.
PV = plasma volume.
TG = total globular volume .
Hb = haemoglobin concentration.
SaO2 = arterial oxygen saturation

Stopping smoking one month prior to surgery will not be more effective than pre-oxygenation with 100% oxygen though it may reduce postoperative pulmonary complications. Note that both long term and short term abstinence reduces pulse rate and blood pressure thus reducing oxygen consumption and also reduce carboxyhaemoglobin levels.

Blood transfusion will not make a big difference in oxygen reserve, particularly if a blood transfusion is administered within 12-24-hours before surgery.

Heliox (79% helium and 21% oxygen) despite its lower viscosity is unlikely to be more effective than 100% oxygen .

After thyroid surgery, about 10-15% of patients experience a temporary subjective voice change of varying degrees. A frog in the throat or cracking of the voice, or a weak voice, are common descriptions. These modifications are only temporary, lasting a few days to a few weeks.

Swelling of the muscles in the area of the dissection, as well as inflammation and oedema of the larynx due to the dissection, or minor trauma from the tracheal tube, are all suspected causes.

On both sides of the thyroid gland, the superior laryngeal nerve (EBSLN) runs along the upper part. The muscles that fine-tune the vocal cords are innervated by these nerves. The quality of their voice is usually normal if they are injured, but making high-pitched sounds may be difficult. Injury to the EBSLN occurs in about 2% of the population.

Injuries to the recurrent laryngeal nerve (RLN) have been reported to occur in 1 percent to 14 percent of people. Except for the cricothyroid muscle, the RLN supplies all of the laryngeal intrinsic muscles.

This complication is usually unilateral and temporary, but it can also be bilateral and permanent, and it can be intentional or unintentional. The most common complication following thyroid surgery is a permanent lesion of damaged RLN, which manifests as an irreversible phonation dysfunction.

The crico-arytenoid joint dislocation is a relatively uncommon complication of tracheal intubation and blunt neck trauma. The probability is less than one in a thousand.

Vocal cord polyps affect 0.8 percent of people.

The cephalic vein is one of the primary superficial veins of the upper limb. It overlies most of the fascial planes as it is located in the superficial fascia along the anterolateral surface of the biceps.

It originates in the anatomical snuffbox from the radial side of the superficial venous network of the dorsum of the hand. It travels laterally up the arm to join the basilic vein via the median cubital vein at the elbow.

Near the shoulder, it passes between the deltoid and pectoralis major muscles. It pierces the coracoid membrane (continuation of the clavipectoral fascia) to terminate in the axillary vein’s first part.

The subclavian artery lies behind and partly above the subclavian vein. 3-4% of the time, it can be inadvertently cannulated during cannulation of the subclavian vein

Because of its anatomical position, putting pressure on the subclavian artery is impossible so arresting bleeding with pressure when it is punctured is not viable.

One of the consequences of subclavian vein cannulation (1%) is pleural puncture leading to a pneumothorax. This is because the apical pleura is inferior and caudal to the subclavian vein.

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.

The emulsification and absorption of fats requires Bile salts.

Absorption of fats is associated with the activation of lipases in the intestine.

Bile salts are involved in fat soluble vitamin absorption and are reabsorbed in the terminal ileum (B12 is NOT fat soluble).

Although Vitamin B12 is also absorbed in the terminal ileum, it is a water soluble vitamin (as are B1, nicotinic acid, folic acid and vitamin C) .

The gastric parietal cells secretes Intrinsic factor that is essential for the absorption of B12.

The hindgut is from the distal third of the transverse colon down to the upper one-third of the anal canal. The inferior mesenteric artery supplies the hindgut.

The inferior mesenteric artery arises from the aorta behind the inferior border of the third part of the duodenum 3€“4 cm above the aortic bifurcation, at the third lumbar vertebra level.

The important landmarks of vessels arising from the abdominal aorta at different levels of vertebrae are:

T12 – Coeliac trunk

L1 – Left renal artery

L2 – Testicular or ovarian arteries

L3 – Inferior mesenteric artery

L4 – Bifurcation of the abdominal aorta.

Randomisation allows for performance of experimental trials in a random order. Using this method gives us control over the confounding variables that are not supposed to be held constant.

For an instance, by employing randomisation we get to control biological differences among individual human beings during experimental trials.

ICP is significant because it influences cerebral perfusion pressure and cerebral blood flow. The normal ICP ranges from 5 to 13 mmHg.

The components within the skull include the brain (80%/1400 ml), blood (10%/150 ml), and cerebrospinal fluid (CSF) (10%/150 ml).

Because the skull is a rigid box, if one of the three components increases in volume, one or more of the remaining components must decrease in volume to compensate, or the ICP will rise (Monroe-Kellie hypothesis).

Primary brain injury occurs as a result of a head injury and is unavoidable unless precautions are taken to reduce the risk of head injury. A reduction in oxygen delivery due to hypoxemia (low arterial PaO2) or anaemia, a reduction in cerebral blood flow due to hypotension or reduced cardiac output, and factors that cause a raised ICP and reduced CPP are all causes of secondary brain injury. Secondary brain injury can be avoided with proper management.

The most important initial management task is to make certain that:

There is protection of the airway and the cervical spine
There is proper ventilation and oxygenation
Blood pressure and cerebral perfusion pressure are both adequate (CPP).

Following the implementation of these management principles, additional strategies to reduce ICP and preserve cerebral perfusion are required. The volume of one or more of the contents of the skull can be reduced using techniques that can be used to reduce ICP.

Reduce the volume of brain tissue
Blood volume should be reduced.
CSF volume should be reduced.

The following are some methods for reducing the volume of brain tissue:
Abscess removal or tumour resection
Steroids (especially dexamethasone) are used to treat oedema in the brain.
To reduce intracellular volume, use mannitol/furosemide or hypertonic saline.
To increase intracranial volume, a decompressive craniectomy is performed.

The following are some methods for reducing blood volume:

Haematomas must be evacuated.
Barbiturate coma reduces cerebral metabolic rate and oxygen consumption, lowering cerebral blood volume as a result.
Hypoxemia, hypercarbia, hyperthermia, vasodilator drugs, and hypotension should all be avoided in the arterial system.
PEEP/airway obstruction/CVP lines in neck: patient positioning with 30° head up, avoid neck compression with ties/excessive rotation, avoid PEEP/airway obstruction/CVP lines in neck

The following are some methods for reducing CSF volume:

To reduce CSF volume, an external ventricular drain or a ventriculoperitoneal shunt is inserted (although more a long term measure).

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.

The Delphi is a group facilitation technique that seeks to obtain consensus on the opinions of `experts’ through a series of structured questionnaires (commonly referred to as rounds). By using successive questionnaires, opinions are considered in a non-adversarial manner, with the current status of the groups’ collective opinion being repeatedly fed back. Studies employing the Delphi make use of individuals who have knowledge of the topic being investigated

The inflow of blood from the superior vena cava is directed towards the right atrioventricular orifice. It returns deoxygenated blood from all structures superior to the diaphragm, except the lungs and heart.

There are no valves in the superior vena cava which is why it is relatively easy to insert a CVP line from the internal jugular vein into the right atrium. The brachiocephalic vein is similar as it also has no valves.