Pg Blazer - Online Test Series 33 - Anaesthesia

Ketamine produces dissociative anesthesia, which is a type of anesthesia characterized by a state of dissociation or detachment from one's surroundings. It induces a trance-like state, providing pain relief, sedation, and amnesia. Ketamine works by blocking the N-methyl-D-aspartate (NMDA) receptors in the brain, which are involved in the transmission and perception of pain. This dissociative effect allows patients to be in a dream-like state while still being able to respond to stimuli, making it useful for certain medical procedures and surgeries. Propofol, Thiopentone, and Enflurane are not known for producing dissociative anesthesia.

Propofol is the anesthetic induction agent of choice for a 20-year old patient presenting with early pregnancy who is admitted for Medical Termination of Pregnancy (MTP) in a day care facility. Propofol is a short-acting intravenous anesthetic that provides rapid induction and recovery, making it suitable for day care procedures. It has a favorable safety profile for both the mother and the fetus, and it does not have teratogenic effects. Therefore, it is the preferred choice in this scenario.

Ketamine increases cerebral blood flow and intracranial pressure. Hence it is contraindicated in patients with increased intracranial pressure.

Xenon is very close to being an ideal anaesthetic agent with multiple advantages like:
Inert
Non toxic
Minimal cardiovascular effects
Low blood solubility
Fast induction and recovery
Non explosive
Does not cause malignant hyperthermia

Hypothermia is the correct answer because it is known to decrease EEG activities. When the body temperature drops below normal, the brain's electrical activity slows down, resulting in decreased EEG readings. This is often observed during surgical procedures where hypothermia is intentionally induced to reduce metabolic demand and protect the brain from potential damage. On the other hand, early hypoxia, ketamine, and N2O may have different effects on EEG activities, but they do not directly cause decreased EEG activities as hypothermia does.

Succinylcholine is the neuromuscular blocking agent with the shortest onset of action. It is a depolarizing muscle relaxant that acts by binding to the nicotinic acetylcholine receptors at the neuromuscular junction, causing sustained depolarization and preventing muscle contraction. Succinylcholine has a rapid onset of action, typically within 30 to 60 seconds, making it useful for rapid sequence intubation or emergency procedures. Its effects are short-lived, with a duration of action of about 5 to 10 minutes, due to rapid metabolism by plasma cholinesterase.

Halothane is the correct answer because it is a fluorinated anesthetic that is known to corrode metal in vaporizers and breathing systems. This corrosion can lead to malfunctioning of the equipment and potential harm to the patient. Sevoflurane, enflurane, and isoflurane are also fluorinated anesthetics, but they do not have the same corrosive effect on metal as halothane does.

Inadvertent intra arterial injection of thiopentone sodium produces pain, not intravenous injection. Propofol causes pain with intravenous injection.

Desflurane has the minimum blood gas solubility coefficient among the given inhalational agents. Blood gas solubility coefficient refers to the ability of an anesthetic agent to dissolve in blood. A lower blood gas solubility coefficient indicates that the agent is less soluble in blood, allowing for faster induction and recovery from anesthesia. Desflurane has a lower blood gas solubility coefficient compared to isoflurane and sevoflurane, making it a preferred choice for inhalational anesthesia. Nitrous oxide, although not mentioned in the question, has a very low blood gas solubility coefficient, even lower than desflurane, making it the least soluble among the options.

The superior oblique muscle is the last muscle to be rendered akinetic with a retrobulbar anesthetic block. This means that it is the last muscle to become paralyzed or immobilized when the block is administered.