Alfentanil is less lipid-soluble than fentanyl and thus is less permeable to the membrane making it less potent.

Alfentanil is a phenylpiperidine opioid analgesic with rapid onset and shorter duration of action.

Alfentanil has less volume of distribution due to its high plasma protein binding (92%)

It can cause respiratory depression and can cause sedation

Perioperative and postoperative analgesia can both be provided by an inguinal hernia field block. The Iliohypogastric and ilioinguinal nerves, as well as the skin, superficial fascia, and deeper structures, must be blocked for maximum effectiveness. The local anaesthetic should ideally have a long duration of action, be highly concentrated, and have a volume of at least 30 mL.

Plain bupivacaine has a maximum safe dose of 2 mg/kg body weight.

Because the patient weighs 75 kg, 150 mg bupivacaine can be safely administered. Both 30 mL 0.5 percent bupivacaine (150 mg) and 60 mL 0.25 percent bupivacaine (150 mg) are acceptable doses, but 30 mL 0.5 percent bupivacaine represents the optimal volume and strength, potentially providing a denser and longer block.

The maximum safe dose of plain lidocaine has been estimated to be between 3.5 and 5 mg/kg. The patient weighs 75 kg and can receive a maximum of 375 mg using the higher dosage regimen:

There are 200 mg of lidocaine in 10 mL of 2% lidocaine (and therefore 11 mL contains 220 mg)
200 mg of lidocaine is contained in 20 mL of 1% lidocaine.

While alternatives are available, Although the doses of 11 mL lidocaine 2% and 20 mL lidocaine 1% are well within the dose limit, the volumes used are insufficient for effective field block for this surgery.

With 1 in 200,000 epinephrine, the maximum safe dose of lidocaine is 7 mg/kg. The patient can be given 525 mg in this case. Even with epinephrine, 60 mL of 1% lidocaine is 600 mg, which could be considered an overdose.

When a drug is given via intravenous infusion, the plasma concentration rises exponentially as a wash-in curve until it reaches steady-state concentration (the point at which the infusion rate is balanced by the elimination rate or clearance). To reach this steady state, the drug will take 4-5 half-lives.

Cpss (target plasma concentration at steady state) and clearance (CL) in ml/minute or litre/hour are the two factors that determine the infusion rate or dose (ID) in mg/hour of a drug.

ID = Cpss × CL

We know the infusion rate is 20 ml/hour in this case. The drug’s concentration is 5 mg/mL. The patient is receiving 100 mg of the drug per hour, with a 20 L/hour clearance rate.

ID = Cpss × 20

Therefore,

Cpss = 100 mg/20000 ml

Cpss = 0.005 mg/mL or 5 mcg/mL

Based on the presenting symptoms, this is the case of bacterial meningitis. The treatment of choice for bacterial meningitis is a cephalosporin. Cephalosporin acts by inhibiting bacterial cell wall synthesis.

Selegiline is a monoamine oxidase inhibitor. Inhibition of monoamine oxidase leads to increased levels of norepinephrine and serotonin in the central nervous system.

Pethidine, also known as meperidine, is a strong agonist at the mu and kappa receptors. It inhibits pain neurotransmission and blocks muscarinic-specific actions.

Administering opioid analgesic is relatively contraindicated to individuals taking monoamine oxidase inhibitors. This is because of the high incidence of serotonin syndrome, which is characterized by fever, agitation, tremor, clonus, hyperreflexia and diaphoresis. Onset of symptoms is within hours, and the treatment is mainly through sedation, paralysis, intubation and ventilation.

The clinical findings are more consistent with Serotonin syndrome rather than exacerbation of Parkinson’s. Parkinson’s Disease (PD) exacerbations are defined as patient-reported or caregiver-reported episodes of subacute worsening of PD motor function in 1 or more domains (bradykinesia, tremor, rigidity, or PD-related postural instability/gait disturbance) that caused a decline in functional status, developed over a period of < 2 months, did not fluctuate with medication timing, and are not caused by intentional adjustments of PD medications by the treating neurologist. Malignant hyperthermia usually occurs within minutes of administration of a volatile anaesthetic, such as halothane, or succinylcholine. There is massive release of calcium from the sarcoplasmic reticulum, leading to fever, acidosis, rhabdomyolysis, trismus, clonus, and hypertension. In sepsis, it more common for patients to present with hypotension rather than hypertension.

Ketamine is primarily used for the induction and maintenance of anaesthesia. It induces dissociative anaesthesia. But it is contraindicated in cardiovascular diseases such as unstable angina or poorly controlled hypertension.

Tricyclic antidepressants (TCA) are primarily used as antidepressants which is important for the management of depression. These are second-line drugs next to SSRI. They work by competitively preventing re-uptake of amines (noradrenaline and serotonin) from the synaptic cleft so increasing their concentration. But TCA overdoses are toxic and have cardiovascular effects, central effects, and anticholinergics effects. Cardiovascular effects like prolonged QT and widened QRS at lower doses progressing to ventricular arrhythmias and refractory hypotension at higher doses can be life-threatening. When used in the perioperative period, it can lead to increased sensitivity to circulating catecholamines therefore care is needed perioperatively.

The leading cause of perioperative anaphylaxis in the UK currently are antibiotics. They account for 46% of cases with identified causative agents. Co-amoxiclav and teicoplanin between them account for 89% of antibiotic-induced perioperative anaphylaxis

Neuromuscular blocking agents (NMBAs) are the second leading cause and account for 33% of case.

Chlorhexidine (0.78/100,000 administrations)
Co-amoxiclav (8.7/100,000 administrations)Suxamethonium (11.1/100,000 administrations)
Patent blue dye (14.6/100,000 administrations)
Teicoplanin (16.4/100,000 administrations)

Anaphylaxis to chlorhexidine periop poses a significant risk in the healthcare setting because of its widespread use with some being fatal.

Resistance pulmonary arteries constrict in response to alveolar and airway hypoxia, diverting blood to better-oxygenated alveoli.

In atelectasis, pneumonia, asthma, and adult respiratory distress syndrome, hypoxic pulmonary vasoconstriction optimises O2 uptake. Hypoxic pulmonary vasoconstriction helps maintain systemic oxygenation during single-lung anaesthesia.

A redox-based O2 sensor within pulmonary artery smooth muscle cells is involved in hypoxic pulmonary vasoconstriction. The production of reactive oxygen species by smooth muscle cells in the pulmonary artery varies in proportion to PaO2. Hypoxic removal of these redox second messengers inhibits voltage-gated potassium channels, depolarizing smooth muscle cells in the pulmonary artery.

L-type calcium channels are activated by depolarization, which raises cytosolic calcium and causes hypoxic pulmonary vasoconstriction. Some anaesthetics suppress this response, increasing the risk of further deterioration in ventilation perfusion mismatch.

Agents that inhibit HPV are ether, halothane, and desflurane (>1.6 MAC).
Agents with no effect on HPV include thiopentone, fentanyl, desflurane (1MAC), isoflurane (<1.5MAC), sevoflurane(1MAC), and propofol.

To begin, one must determine the child’s approximate weight. There are a variety of formulas to choose from. It is acceptable to use the advanced paediatric life support formula:

(Age + 4) 2 = Weight

A 5-year-old child will weigh around 18 kilogrammes.

10 mcg/kg (0.1 ml/kg of 1 in 10 000 adrenaline) = 180 mcg is the appropriate dose of intravenous or intraosseous adrenaline.

The correct energy level to deliver is 4 J/kg, which equals 72 joules.

The pad size that is appropriate for this patient is 8-12 cm. For an infant, a 4.5 cm pad is appropriate.

To allow adequate separation in infants and small children, the pads should be placed anteriorly and posteriorly on the chest.

When using a bag and mask to ventilate, take two breaths for every 15 chest compressions. If chest compressions are being applied intubated and without interruption, a ventilation rate of 10-20 breaths per minute should be given.

Chest compressions should be done at a rate of 100-120 per minute, the same as an adult.

Dopamine (DA) is a dopaminergic (D1 and D2) as well as adrenergic ? and?1 (but not ?2 ) agonist.

The D1 receptors in renal and mesenteric blood vessels are the most sensitive: i.v. infusion of a low dose of DA dilates these vessels (by raising intracellular cAMP). This increases g.f.r. In addition, DA exerts a natriuretic effect by D1 receptors on proximal tubular cells.

Moderately high doses produce a positive inotropic (direct?1 and D1 action + that due to NA release), but the little chronotropic effect on the heart.

Vasoconstriction (?1 action) occurs only when large doses are infused.

At doses normally employed, it raises cardiac output and systolic BP with little effect on diastolic BP. It has practically no effect on nonvascular ? and ? receptors; does not penetrate the blood-brain barrier—no CNS effects.

Dopamine is used in patients with cardiogenic or septic shock and severe CHF wherein it increases BP and urine outflow.

It is administered by i.v. infusion (0.2–1 mg/min) which is regulated by monitoring BP and rate of urine formation