The tibial nerve lies on top of the vessels contained within the inferior aspect of the popliteal fossa.

In the superior aspect of the fossa, the tibial nerve runs lateral to the vessels, before then travelling superficial to the vessels, and then finally changing course to lie medial to the vessels.

The popliteal artery is the most deep structure present in the popliteal fossa

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 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.

As there is no brachiocephalic artery on the left side, the artery is entered by the catheter on the right side.

The brachiocephalic artery branches into the common carotid and the right subclavian artery, so the catheter is most likely to enter the right subclavian artery, or also possibly the right carotid.

Atypical antipsychotic drugs include risperidone and quetiapine. They not only inhibit dopamine receptors in the limbic system, but also histamine (H1) and alpha2 adrenoreceptors. When combined with general and/or central neuraxial block, this might result in severe hypotension.

Donepezil (Aricept) is an acetylcholinesterase (AChE) inhibitor that increases the neurotransmitter acetylcholine in the cerebral cortex and hippocampus in a reversible, non-competitive manner. It is used to reduce the advancement of Alzheimer’s disease symptoms (AD). Rivastigmine and galantamine are two more drugs that work in the same way.

Ginkgo Biloba contains anti-oxidant characteristics and is used to treat early-stage Alzheimer’s disease, vascular dementia, and peripheral vascular disease. It lowers platelet adhesiveness and decreases platelet activating factor (PAF) increasing the risk f bleeding, especially in individuals who are also taking anticoagulants and antiplatelet medication.

Memantine is an antagonist of the NMDA receptor. Synaptic plasticity, which is thought to be a critical component of learning and memory, can be inhibited at high doses. The use of ketamine is a relative contraindication since antagonism of this receptor can cause a dissociative state.

The ECG changes seen in hypomagnesaemia include:

Prolonged PR interval
Prolonged QT interval
Flattening of T waves
ST segment depression
Prominent U waves

These changes are almost the same as those of hypokalaemia.

There is an increased risk of digoxin toxicity and a risk of atrial and ventricular ectopic and ventricular arrhythmias.

There is impaired synthesis and release of parathyroid hormone (PTH) in chronic hypomagnesaemia leading to impaired target organ response to PTH. This produces secondary hypocalcaemia.

The use of potassium ‘wasting’ diuretics (e.g. loop diuretics like furosemide) may lead to Hypomagnesaemia.

A tall T wave is seen in hypermagnesemia.

The renal effects of atrial natriuretic peptide (ANP) secretion are as follows:

Increased glomerular filtration rate by dilating the afferent glomerular arteriole. Moreover, it constricts the efferent glomerular arteriole, and relaxes the mesangial cells.
Reduces sodium reabsorption in the collecting ducts and distal convoluted tubule.
The renin-angiotensin system (RAS) is inhibited.
Blood flow in the vasa recta is increased.

Because plasma osmolality is unlikely to change, hypothalamic osmoreceptors are unaffected.

The plasma protein has a molecular weight of 66 kDa, is not normally filtered into the proximal convoluted tubule, and has no osmotic diuretic effect.

The following are some basic assumptions:

Extracellular fluid (ECF) makes up one-third of total body water (TBW), while intracellular fluid makes up the other two-thirds (ICF)
One-quarter plasma and three-quarters interstitial fluid make up ECF (ISF)
The volume receptors in the atria have a 7-10% blood volume change threshold.
The osmoreceptors are sensitive to changes in osmolality of 1-2 percent.
The normal plasma osmolality before the transfusion is 287-290 mOsm/kg.
The plasma protein solution is a colloid that is only delivered to the intravascular compartment. The tonicity remains unchanged.
The blood volume increases by 20%, from 5,000 mls to 6,000 mls. This is higher than the volume receptor threshold of 7 to 10%.

In patients with an intact hypothalamic-pituitary axis, serial TSH measurements are used to determine the adequacy of treatment with thyroid hormones . changes in TSH levels becoming apparent after approximately eight weeks of therapy with thyroid hormone replacement. Change in T3/T4 levels are seen before changes in TSH .

In patients taking thyroid replacement therapy, the most frequent reason for persistent elevation of serum TSH is poor compliance. Patients who do not regularly take their L-thyroxine try and catch up just before a visit to a clinician for blood test.

Tissue-level unresponsiveness to thyroid hormone is caused by mutation in the gene controlling a receptor for T3 and is rare.

Reduced responsiveness of target tissues to thyroid hormone aka resistance to thyroid hormones (rTH) occurs when there is a mutation in the thyroid hormone receptor ? gene. It is a rare autosomal dominant inherited syndrome of reduced end-organ responsiveness to thyroid hormone and has two types:

Generalised resistance (GrTH)
Pituitary resistance (PrTH)

Patients with rTH have normal or slightly elevated serum thyroid stimulating hormone (TSH) level, elevated serum free thyroxine (FT4) and free triiodothyronine (FT3) concentrations.

Drugs that increase metabolism of thyroxine include:

Warfarin
Rifampin
Phenytoin
Phenobarbital
St John’s Wort
Carbamazepine

These drugs lower circulating thyroid hormones and would be associated with a raised TSH but low T3/T4.

The Glasgow Coma Scale (GCS) has been used in outcome models as a measure of physiological derangement and as a tool for assessing head trauma.

Eye opening (E):

4 Spontaneously
3 Responds to voice
2 Responds to painful stimulus
1 No response.

Best verbal response (V):

5 Orientated, converses normally
4 Confused, disoriented conversation, but able to answer basic questions
3 Inappropriate responses, words discernible
2 Incomprehensible speech
1 Makes no sounds.

Best motor response (M):

6 Obeys commands for movement
5 Purposeful movement to painful stimulus
4 Withdraws from pain
3 Abnormal (spastic) flexor response to painful stimuli, decorticate posture
2 Extensor response to painful stimuli, decerebrate posture
1 No response.

In this case, GCS = 2+3+5 = 10.

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.