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Anaesthesia MCQs
#3
Explanations:

Q1.  Answer - B
The difference between adult and children airway for the anesthesia point of view.

The epiglottis in infants is large stiff and omega shaped compared to short broad and flat epiglottis of adults (fig. 1). Epiglottis sits at 45 degree angles to anterior pharyngeal wall (adults 20 degree), as a result of which epiglottis should be picked up with the blade for better visualization of glottis. Larynx lies in a more cephalic position C3 – C4 at birth, C4 – C5 at 2 years of age, C5 – C6 by adulthood . A cephalic and superior position on larynx in infants creates more acute angulation between glottis and base of tongue hence posterior displacement is often necessary to improve the view. Larynx is funnel shaped (cylindrical in adults) till 6–8 years of age because cricoids cartilage (glottis in adults) is the narrowest part of airway. The vocal cords are bow shaped making an angle with anterior commissure, where as the plane of vocal cords is perpendicular to long axis of trachea and vocal cords are linear in adults. This
angulation of vocal cords increase the chance of endotracheal tube (ETT) abutting the anterior commissure during blind intubation.


2. Answer 

Head trauma patients usually require ventilator support due to respiratory failure secondary to impaired consciousness, decreased respiratory drive, chest injury, or ARDS. In case of isolated brain injury a degree of vulnerability is present in the lung tissue secondary to the pro-inflammatory state. This is aggravated by the use of high tidal volumes.


The main goal of ventilation in head injury patients has been to keep a low PaCO2 so as to prevent an increase in intracranial pressure (ICP) secondary to cerebral vasodilation. However, this can lead to reduced cerebral blood flow which can lead to cerebral ischemia. Guidelines stated by Brain Trauma Foundation (BTF) suggest that:

  1. Prophylactic hyperventilation to a PaCO2£ 25 mmHg (in the absence of intracranial hypertension) is not recommended (level II evidence).
  2. Hyperventilation is only recommended as a temporizing measure for the reduction of elevated ICP (level III evidence).
  3. Hyperventilation should be avoided during the first 24 h after injury when cerebral blood flow is often critically reduced.
  4. If hyperventilation is used, cerebral oxygen delivery should be monitored by jugular oxygen saturation (SjO2) or brain oxygen tension (PbrO2).
The role of PEEP 

Brain-injured patients are at high risk for associated pulmonary pathology, as part of the initial injury (pulmonary contusion, haemopneumothorax) or as sequelae of the brain injury (secondary pulmonary complications). Maintenance of adequate brain tissue oxygenation is paramount for a favourable outcome. PEEP improves oxygenation by recruitment of atelectatic alveolar units, improving FRC and preventing atelectrauma. However, it may have detrimental neurologic effects in certain clinical circumstances


3. Answer: 
Methadone, a long-acting synthetic opioid that prevents or reverses withdrawal symptoms and blocks the euphoric effects of other opiates, is the most widely used therapy for opioid dependence. Methadone induces prolongation of the rate-corrected QT interval (QTc) through blockade of the rapidly activating delayed rectifier potassium current (IKr) through the cardiac human ether-a-go-go-related gene (hERG) channel. Both the degree of QTc prolongation associated with methadone and the efficacy of methadone in opioid dependence increase with higher doses of methadone, resulting in a safety–efficacy paradox
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Messages In This Thread
Anaesthesia MCQs - by acrosspg - 01-02-2017, 11:54 PM
RE: Anaesthesia MCQs - by acrosspg - 01-02-2017, 11:56 PM
RE: Anaesthesia MCQs - by acrosspg - 02-02-2017, 12:20 AM

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