Onset of local anaesthetic block

A lower tissue pH will increase the speed of onset of local anaesthetic block. TRUE/FALSE

An increase in progesterone, increases the sensitivity to local anaesthesia. TRUE/FALSE

A large nerve axon has a faster onset of action with the same dose of local anaesthetic, compared to a small nerve. TRUE/FALSE

Fick’s law of diffusion covers all of the factors that affect onset of a local anaesthetic block. TRUE/FALSE

Ropivicaine has intrinsic vasodilatory actions which may reduce its length of action. TRUE/FALSE


Duration of Non-depolarising Neuromuscular Blocking Agents

NDMRs with a long duration of action have a clearance rate that is limited by the glomerular filtration rate. TRUE/FALSE

Intravenous calcium can be used to hasten the recovery from neuromuscular blockade. TRUE/FALSE

Magnesium and Lithium have opposing effects on the duration of action of NDMRs. TRUE/FALSE

Hypothermia increases the duration of vecuronium induced neuromuscular blockade. TRUE/FALSE

A patient with a 40% burn 2 weeks prior, is likely to be resistant to the effects of NDMRs. TRUE/FALSE

Onset time for Non-Depolarising Neuromuscular Blockade

Increasing the dose of Atracurium from 0.6mg/kg to 1.0mg/kg, increases the speed of onset of intubating conditions. TRUE/FALSE

Sevoflurane will slow the onset of non-depolarising neuromuscular blocking drugs. TRUE/FALSE

The gender difference in sensitivity to NDMRs is insignificant. TRUE/FALSE

The onset of action of NDMRs in peripheral muscles (versus central) is slower primarily due to differences in blood supply. TRUE/FALSE

The most potent NDMR has the slowest onset whereas the least potent NDMR has the fastest. TRUE/FALSE

Ephedrine increases the cardiac output, which causes the NDMR to reach the effect site more quickly. TRUE/FALSE

The onset of NDMRs may be delayed in someone with poor nutritional status. TRUE/FALSE



2018.1 SAQ 8

Outline the pharmacology of intravenous metoprolol.

The use of beta-blockers peri-operatively has been topical for the last few years. There have been conflicting results with large studies, but the evidence has strongly suggested that stopping a patient on long term beta blocker therapy can cause harm.

We are often faced with patients who, for various surgical and hospital reasons, have missed their regular beta blocker dose. This question asks about the pharmacology of intravenous metoprolol, which is one of the more commonly used beta blockers in a theatre environment. We ask this question because we want you to consider why and when you would give this drug, and what the effects of giving this might be.


A. Metoprolol is a non-selective beta antagonist. TRUE/FALSE

Beta blockers can be categorised as non selective or cardio-selective. The cardio-selective are more potent at blocking beta-1 receptors than beta-2, and are therefore much less likely to trigger bronchospasm. This effect can be overcome with higher doses and even cardio-selective beta blockers can become non-selective at higher doses.

B. The metabolism of metoprolol is reliable and predictable. TRUE/FALSE

Metoprolol is a racemic mixture and exhibits stereo selective metabolism when administered orally. It is dependent on oxidation via CYP2D6. CYP2D6 is absent in approximately 8% of the caucasian population.

C. The intravenous dose of metoprolol is the same as the oral dose. TRUE/FALSE

The oral bioavailability of Metoprolol is 50%. This can go up to 70% if there are repeated doses. The biological half life has a large range but in normal metabolisers is 3-7 hours.

D. Metoprolol is not used in congestive heart failure or ischaemic heart disease, due to its effects on contractility. TRUE/FALSE

Metoprolol is used in coronary vascular disease. Why is this?

E. Metoprolol can be used in Raynaud’s due to the vasodilatory effects. TRUE/FALSE

The beta 2 receptors can be activated and cause bronchodilation. They can also cause vasodilation in the vessels in the gut, skeletal muscle and the kidneys.

Qu’ils mangent de la brioche

During a trip to this amazing palace early last year, I was taken on a tour that included the room where Marie Antoinette gave birth. As princesses of the royal blood were not able to take the throne, the birth was public to ensure no substitution of the neonate at birth. Marie-Antoinette was married for 8 years prior to the birth of her first child, and her sister-in-law had already produced two male heirs to the throne. The pressure was on.

Her first born was, indeed, a girl and Marie Antoinette fainted on delivery. Historians have not come to a conclusion as to why this “faint” occurred, but many reason have been postulated and many of which have links to the primary learning objectives. It was thought the pressure to produce a male heir was too much and she fainted on the delivery of a female. She may have also fainted due to the heat from such a crowd in the room. Two enormous tapestry sheets surrounded her bed and fell on her immediately after delivery, due to the crush of people wanting to see the gender of the baby. And as the baby was born in 1778, there was no pain relief for delivery.

Whatever the reason, the management of this loss of consciousness was to open some windows and provide venesection therapy. Correlation and causation have been confused in history and these treatments were deemed successful.

Marie Antoinette went on to have four children, however her first child was the only one to reach adulthood. She was Queen of France for 20 minutes after her father-in-law abdicated and her husband (and cousin) took twenty minutes to sign the same document.

SS_OB 1.4 Describe the utero-placental circulation and the principles of placental physiology as related to placental gas exchange and regulation of placental blood flow.

Uteroplacental blood flow at term is approximately 1125mL/min TRUE/FALSE

The utero-placental arteries have alpha-adrenergic receptors. TRUE/FALSE

The greatest driving force for diffusion of oxygen from maternal to foetal blood is the Bohr effect. TRUE/FALSE

The Haldane effect facilitates oxygen transfer from the mother to the foetus. TRUE/FALSE

The foetus has foetal haemoglobin which has a greater affinity for oxygen than adult haemoglobin. TRUE/FALSE

Aortocaval compression

SS_OB 1.5 Describe the mechanism and consequences of aorta-caval compression in pregnancy

In supine hypotensive syndrome, blood still returns to the right heart through the epidural, azygos and vertebral veins. TRUE/FALSE

Supine hypotension is compensated by an increase in peripheral sympathetic activity. TRUE/FALSE

The blood pressure measured in the arms, is a reliable predictor of uterine and placental blood flow, when the patient is supine. TRUE/FALSE

Aortocaval compression can reduce uterine perfusion due to reduced uterine venous pressure. TRUE/FALSE

General anaesthesia has no effect on supine hypotensive syndrome. TRUE/FALSE


Obs, Obs, Baby.

SS_OB 1.6 Describe the changes in the anatomy of the maternal airway and their impact on airway management during anaesthesia.

SS_OB 1.1 Describe the physiological changes and their implications for anaesthesia that occur during pregnancy, labour and delivery.

The increased risk of airway bleeding during manipulation is primarily due to platelet dysfunction in pregnancy. TRUE/FALSE

Lung compliance decreases in pregnancy. TRUE/FALSE

Closing capacity increases during pregnancy. TRUE/FALSE

Oxygen consumption is increased at term, regardless of whether the patient is in labour or not. TRUE/FALSE

Airway oedema can occur due to venous engorgement from labour. TRUE/FALSE

Neonatal circulation

SB_OB 1.3 Describe the transition from foetal to neonatal circulation and the establishment of ventilation.

At birth, the circulation changes from parallel to in series. TRUE/FALSE

Delivery of the neonate causes a reduction in flow through the IVC to the right atrium. TRUE/FALSE

The newborn’s ventricle is less compliant than an adult’s due to a lower proportion of non contractile proteins in the myocardial cells. TRUE/FALSE

Pulmonary vascular resistance falls at birth due to decreasing pH TRUE/FALSE

The neonatal circulation can revert back to the pattern of foetal circulation if there is pulmonary vasoconstriction. TRUE/FALSE

BT_PO 1.9 Hypoxia

Hypoxia is a strong driver to increase respiratory rate. TRUE/FALSE.

The aortic body peripheral chemoreceptors are the most important peripheral chemoreceptors in humans. TRUE/FALSE.

The central chemoreceptors respond directly to changes in the H+ concentration in the CSF. TRUE/FALSE.

Inflation of the lungs that is detected by pulmonary stretch receptors increases respiratory rate. TRUE/FALSE.

Rapid breathing in left heart failure is potentially due to stimulation of the junta-capillary receptors. TRUE/FALSE.