Standard error can be calculated by the following formula:

Standard Error= (Standard Deviation)/ˆš(Sample Size)
= (12) / ˆš(64)
= 12 / 8
= 1.5

The external carotid artery has eight important branches:
Anterior surface:
1. Superior thyroid artery (first branch)
2. Lingual artery
3. Facial artery
Medial branch
4. Ascending pharyngeal artery
Posterior branches
5. Occipital artery
6. Posterior auricular artery
Terminal branches
7. Maxillary artery
8. Superficial temporal artery

The external carotid has eight branches, 3 from its anterior surface ; thyroid, lingual and facial. The pharyngeal artery is a medial branch. The posterior auricular and occipital are posterior branches.

When the association among any two classes of object is defined by the presence of a third entity it is termed as indirect association. For an instance, the age of the employee may affect the rate of pay, which would have implications on job satisfaction. So, in this example, an indirect relationship between age and job satisfaction exists due to a third party i.e. rate of pay.

Pipeline gases (in the UK this includes: Oxygen, Nitrous oxide, Medical air, and Entonox) are supplied at 4 bar (or 400 kPa), and compressed air is supplied at 7 bar for power tools.

Carbon dioxide and nitric oxide are usually only supplied in cylinders.

The femoral triangle is a wedge-shaped area found within the superomedial aspect of the anterior thigh. It is a passageway for structures to leave and enter the anterior thigh.

Superior: Inguinal ligament
Medial: Adductor longus
Lateral: Sartorius
Floor: Iliopsoas, adductor longus and pectineus

The contents include: (medial to lateral)
Femoral vein
Femoral artery-pulse palpated at the mid inguinal point
Femoral nerve
Deep and superficial inguinal lymph nodes
Lateral cutaneous nerve
Great saphenous vein
Femoral branch of the genitofemoral nerve.

Nitroglycerine is rapidly denitrated enzymatically in the smooth muscle cell to release the free radical nitric oxide (NO).
Released NO activated cytosolic guanylyl cyclase which increases cGMP (cyclin guanosine monophosphate) which causes dephosphorylation of myosin light chain kinase (MLCK) through a cGMP-dependent protein kinase.
Reduced availability of phosphorylated (active) MLCK interferes with activation of myosin and in turn, it fails to interact with actin to cause contraction. Consequently, relaxation occurs.

The larynx is an air passage, sphincter, and organ of phonation that extends from the tongue to the trachea. It lies in the anterior part of the neck at the vertebral levels C3 to C6.

Important anatomical landmarks:
C1-C2 – Atlas and axis, respectively

C3-C6 – Larynx

C5 – Thyroid cartilage

T5-T7 – Pulmonary hilum

T12-L1 – Duodenum.

The Poiseuille’s formula states that Q = ΔPÏ€r4/8Lη

where
ΔP = the pressure gradient along the vessel
Q = flow rate
r = radius of the vessel
η = coefficient of viscosity (haematocrit) of the blood
L = length of the blood vessel.

Resistance is pressure difference/flow (ΔP/Q) (analogous to Ohm’s law)

Rearranging Poiseuille’s equation ΔP/Q =8Lη/Ï€r4

Although the stiffness of the vessel wall affects blood flow, the thickness of the vessel wall does not.

There are two types of drug dose-response relationships, namely, the graded dose-response and the quantal dose-response relationships.

Drug response curves are plotted as percentage response again LOG drug concentration. This graph is sigmoid in shape.

Agonists are drugs with high affinity and high intrinsic activity. Meanwhile, the antagonist is a drug with high affinity but no intrinsic activity. Intrinsic activity determines the maximal response. The maximal response can be achieved even by activation of a small proportion of receptor sites.

Being the part of a meta analysis, forest plots are more valued as evidence then randomised control trials.

The notion that forest plots can only be used if the results are substantial is not true. They are good indicators of the significance of the data. If the diamond intersects the central line, the data is rendered significant. It also aggregates means and confidence intervals from studies conducted in the past which makes the study much more reliable as errors associated with individual studies tend to have less of an impact in this way.

The suggestion that forest plots are primarily used for qualitative data is factually incorrect. Forest plots require numerical values to function.

All in all, forest plots help us in determining whether or not there is a significant trend in that particular field of study.

A paediatric 19G Tuohy catheter is available that is 5cm in length and has 0.5cm markings

18G Tuohy catheters are generally 9 to 10cm to hub

Distal end of catheter is angled (15 to 30 degrees) and closed to avoid puncturing the dura

Epidural mesh are usually 0.2 microns and are used to filter bacteria and viruses to ensure sterility of procedure

Transparent catheters are 90cm long with diameters depending on gauge size. It has 1cm graduations from 5 to 20cm to ensure they have been inserted amply and removed completely. Distal end is smooth which can be open or closed (with lateral openings).

The ideal gas equation makes the following assumptions:

The gas particles have a small volume in comparison to the volume occupied by the gas.
Between the gas particles, there are no forces of interaction.
Individual gas particle collisions, as well as gas particle collisions with container walls, are elastic, meaning momentum is conserved.
PV = nRT
Where:

P = pressure
V = volume
n = moles of gas
T = temperature
R = universal gas constant

Helium is a monoatomic gas with a small helium atom. The attractive forces between helium atoms are small because the helium atom is spherical and has no dipole moment. Because helium atoms are spherical, collisions between them approach the ideal state of elasticity.

Most real gases behave qualitatively like ideal gases at standard temperatures and pressures. When intermolecular forces and molecular size become important, the ideal gas model tends to fail at lower temperatures or higher pressures. It also fails to work with the majority of heavy gases.

Helium, argon, neon, and xenon are noble or inert gases that behave the most like an ideal gas. Xenon is a noble gas with a much larger atomic size than helium.

The neuroleptic malignant syndrome is a rare complication in response to neuroleptic or antipsychotic medication.

The main features are:
– Elevated creatinine kinase
– Hyperthermia and tachycardia
– Altered mental state
– Increased white cell count
– Insidious onset over 1-3 days
– Extrapyramidal dysfunction (muscle rigidity, tremor, dystonia)
– Autonomic dysfunction (Labile blood pressure, sweating, salivation, urinary incontinence)

Management is supportive ICU care, anticholinergic drugs, increasing dopaminergic activity with Amantadine, L-dopa, and dantrolene, and non- depolarising neuromuscular blockade drugs

Desflurane is a highly fluorinated methyl ethyl ether used for the maintenance of general anaesthesia. It has been identified as a weak triggering anaesthetic of malignant hyperthermia. That, in the absence of succinylcholine, may produce a delayed onset of symptoms.

The blood brain barrier (BBB) consists of the ultrafiltration barrier in the choroid plexus and the barrier around cerebral capillaries. The barrier is made by endothelial cells which line the interior of all blood vessels. In the capillaries that form the blood€“brain barrier, endothelial cells are wedged extremely close to each other, forming so-called tight junctions.

Outside of the BBB lies the hypothalamus, third and fourth ventricles and the chemoreceptor trigger zone (CTZ).

Water, oxygen and carbon dioxide cross the BBB freely but glucose is controlled. The ability of chemicals to cross the barrier is proportional to their lipid solubility, not their water solubility. It’s ability to cross is inversely proportional to their molecular size and charge.

In neonates, the BBB is less effective than in adults. This is why there is increased passage of opioids and bile salts (kernicterus) into the neonatal brain.

In meningitis, the effectiveness and permeability of the BBB is affected, and as a result, this effect helps the passage of antibiotics which would otherwise not normally be able to cross.

Patients who present for surgery may be on prescription medication or natural/herbal therapies. These have relevance for anaesthesia since they can cause drug interactions.

Ephedra (Ma Huang) is a drug derived from the plant Ephedra sinica that is used as a CNS stimulant, weight reduction aid, and asthma therapy. It is a combination of alkaloids that includes ephedrine which stimulates noradrenaline release from pre-synaptic neurones by acting directly on alpha and beta adrenoreceptors. The use of sympathomimetic drugs together can cause cardiovascular instability.

Ginkgo Biloba contains anti-oxidant characteristics and is used to treat Alzheimer’s disease, vascular dementia, and peripheral vascular disease. It lowers platelet adhesiveness and raises the risk of bleeding by decreasing platelet activating factor (PAF), especially in individuals who are also taking anticoagulants and antiplatelet drugs.

The extract from St. John’s Wort is utilised as an antidepressant because it is a cytochrome P450 isoenzyme inhibitor as well as a serotonin uptake inhibitor. When drugs like fentanyl or tramadol are used during an anaesthetic, there is a risk of serotonin syndrome developing.

The root of a pepper is used to make kava (Piper methysticum). It is a weak GABAA agonist which has the potential to augment the effects of propofol and benzodiazepines, which are volatile anaesthetics.

Garlic is made from the allium sativum plant and is used to treat hypertension and hyperlipidaemia. It includes cysteine, which inhibits platelet aggregation irreversibly, amplifying the effects of aspirin and NSAIDs.

Echinacea is a common herbal medicine that stimulates the immune system by modulating cytokine signalling. In individuals who require organ transplantation, it should be avoided.

The umbilical vein closes once the umbilical cord is clamped following birth. This causes a rise in systemic vascular resistance, closing the ductus venosus.

Upon birth, the pulmonary vascular resistance is decreased as the lungs are aerated.

At birth, there is a rise in oxygen tension which causes the corresponding constriction of the ductus arteriosus. This prevents a left to right shunt as it stops aortic blood and blood from the pulmonary artery from mixing. The ventricles do no have an opening connecting them.

The foramen ovale closes soon after birth. It is the septum opening between the left and right atrium.

An adult’s cardiac output is expected to be 5 L/min.

Bilirubin is formed by metabolizing heme, mostly from haemoglobin in red blood cells.

Bilirubin is conjugated to glucuronic acid in the hepatocytes by the glucuronyl transferase enzyme in order to enable it to become soluble and allow for its secretion across the canalicular membrane and into bile.

The conjugation process is increased by rifampicin and decreased by valproate.

Gilbert’s syndrome is caused by a decrease in glucuronyl transferase in the hepatic system, decreasing the transport of bilirubin into the hepatocyte, causing unconjugated bilirubinaemia.

Crigler-Najjer syndrome is caused by mutations in the genes responsible for hepatic glucuronyl transferase, decreasing the activity of the enzyme, meaning bilirubin cannot be conjugated, causing unconjugated bilirubinaemia.

Dubin-Johnson syndrome does not cause an impairment in the conjugation of bilirubin, but it blocks the transport of bilirubin out of the hepatocyte resulting in conjugated bilirubinaemia.

The patient is likely suffering from biliary colic since her pain is intermittent and comes and goes in waves. Biliary colic pain gets worse after eating, especially fatty food as bile helps digest fats. Gallstones are the most common cause of biliary colic and are usually located in the cystic duct or common bile duct. But since this patient has no signs of jaundice or steatorrhea, the duct most likely blocked is the cystic duct.

The cystic duct drains the gallbladder and combines with the common hepatic duct to form the common bile duct. The common bile duct then merges with the pancreatic duct and opens into the second part of the duodenum (major duodenal papilla).

The duodenojejunal flexure is attached to the diaphragm by the ligament of Treitz and is not associated with any common pathology.
The fourth part of the duodenum passes very close to the abdominal aorta and can be compressed by an abdominal aortic aneurysm.
The third part of the duodenum can be affected by superior mesenteric artery syndrome, where the duodenum is compressed between the SMA and the aorta, often in cases of reduced body fat.
The first part of the duodenum is the most common location for peptic ulcers affecting this organ.

PaCO2 is one of the most important factors that regulate cerebral vascular tone. CO2 induces cerebral vasodilatation and as a result, it increases CBF. Between 20 mmHg (2.7 kPa) and 80 mmHg (10.7 kPa), there is a linear increase of PaCO2.

Sometimes, there are areas where auto regulation has failed locally but not globally. Similarly, local vs. systemic acidosis will have similar effects. When the PaO2 falls below 50 mmHg (6.5 kPa), the CBF progressively increases.

An increase in the cerebral metabolic rate for oxygen (CMRO2) and therefore CBF can be caused by hyperthermia.
A late feature of cerebral injury is hyperthermia secondary to hypothalamic injury. Therefore this is not the most likely cause of an increased CBF in this scenario.

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.

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 mechanism of action of macrolides is inhibition of bacterial protein synthesis by preventing peptidyltransferase from adding to the growing peptide which is attached to tRNA to the next amino acid.

Phase 2 trials involve patients that are suffering from the disease under study and are associated with determining the efficiency and the optimum dosage of the drug.

Phase 0 trials assist the scientists in studying the behaviour of drugs in humans by micro dosing patients. They are used to speed up the developmental process. They have no measurable therapeutic effect and efficiency.

Phase 1 is associated with assessing whether a drug is safe to use or not. The process is extensive and can take up to several months. It also involves healthy participants (less than 100) that are paid to take part in the study. The side effects upon increasing dosage are also addressed by the study. The effects the drug has on humans including how its absorbed, metabolized and excreted are studied. Approximately 70% of the drugs pass this phase.

Cephalosporin belongs to a family of beta-lactam antibiotics. All β-lactam antibiotics interfere with the synthesis of the bacterial cell walls. The β-lactam antibiotics inhibit the transpeptidases so that cross-linking (which maintains the close-knit structure of the cell wall) does not take place i.e. they inhibit bacterial cell wall formation.

The following are the colour codes for medical gas cylinder in the UK:

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 first rib is an atypical rib. It is short, wide, and flattened and lies in an oblique plane.

It has a small scalene tubercle on its medial border which marks the point of attachment of scalenus anterior. The lower surface lies on the pleura and is smooth.

The tubercle on the upper surface separates an anterior groove for the subclavian vein and a posterior groove for the subclavian artery and lower trunk of the brachial plexus.

Scalenus medius is attached to a roughened area posterior to the groove for the subclavian artery.

The upper surface gives attachment anteriorly to the subclavius muscle and costoclavicular ligament.

Hiatus is an opening in the diaphragm. A hiatal hernia is a protrusion of the upper part of the stomach through an opening in the diaphragm, the oesophageal hiatus, into the thorax. The oesophageal hiatus occurs at the level of T10 in the right crus of the diaphragm.

Other important openings in the diaphragm:
T8: vena cava, terminal branches of the right phrenic nerve
T10: oesophagus, vagal trunks, left anterior phrenic vessels, oesophageal branches of the left gastric vessels
T12: descending aorta, thoracic duct, azygous and hemi-azygous vein

An opening in the diaphragm is called a hiatus. The oesophageal hiatus is at vertebral level T10. A hiatus hernia is where the stomach bulges through the oesophageal hiatus hence the name – hiatus hernia.

Serum specific IgE assays against allergen sources/molecules are the most commonly used in vitro diagnostic approach. The measurement of specific IgE recognizing allergenic epitopes can be achieved both through the usage of single reagents (singleplex) or with a pre-defined panel of a number of molecules to be tested simultaneously (multiplex).

Several clinical entities have been described and those occurring immediately after drug exposure are immunoglobulin E (IgE)-mediated and explored by skin testing and by the in vitro measurement of serum-specific IgE. The sensitivity of these tests is not 100% and even for patients with a clear positive history, a drug provocation test may be required in order to confirm the diagnosis. The advantages of the in vitro determination of specific IgE antibodies when compared with in vivo testing are that the former poses no direct risk to the patient and does not require personnel with expertise. Even though in vitro tests are recommended in immediate hypersensitivity reactions, their exact place in the diagnostic procedure is not clear and certain authors do not use this method in daily practice. In one study, in terms of sensitivity, 11 of 26 patients (42%) with negative skin tests and a positive drug provocation challenge (or repeated clinical history) had specific IgE to benzylpenicilloyl or amoxicilloyl (4). The specificity of the test was 95€“100%. Therefore, IgE measurements can avoid a potentially harmful drug provocation test.

An elevated serum tryptase does not differentiate between type 1 and type 2 hypersensitivity reaction. It indicates mast cell degranulation.

RAST is a useful aid to improve the overall diagnosis of drug allergies by using radioactive detection. This, however, is now rarely used.

Quantification of basophil activation by CD63 expression can be done by flow cytometry, which forms the basis of experimental drug-induced basophil stimulation tests.

The most important determinant of preoxygenation adequacy is expired fraction of oxygen. Denitrogenating of the functional residual capacity is the purpose of preoxygenation. This is dependent on three vital factors: (1) respiratory rate; (2) inspired volume, and; (3) inspired oxygen concentration (FiO2).

Arterial oxygen saturation does not efficiently determine adequacy of preoxygenation because of its inability to measure tissue reserves. Arterial partial pressure of oxygen is also unsuitable for determining preoxygenation adequacy. Moreover, the absence of central cyanosis is a very crude sign of low tissue oxygenation.