RxPG AIIMS May 2003 BOOK Preview
Date: Sunday, July 06 @ 02:25:49 IST
Topic: AIIMS


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Preview the first 12 questions of RxPG May AIIMS Book exclusively here. Like everytime, this AIIMS paper is also released in book format by RxPG within 20 days of the exam. This is our fourth consecutive AIIMS exam in book format.

1. In a 2 months old infant undergoing surgery for biliary atresia, you would avoid one of the following anaesthetic:
A. Thiopentone
B. Halothane
C. Propofol
D. Sevoflurane


Answer: B (Halothane)

Ref: KDT-351,352,349, HPIM 15th edn, page 1740

Quality: Spotter Status: Repeat

Discussion
Halothane has hepatotoxic potential which is increased in presence of decrease blood flow to liver and preoperative liver disease.

Explanation
A. Thiopentone: IV inducing agent,ultra short acting, 2.5% solution used leads to CNS depression lasting more than 12 hours. It is used for short operation that are not painful.
B. Halothane: Inhalational anesthetic,contraindicated in the presence of jaundice. It is a potent GA, poor analgesic or muscle relaxant. It leads to direct myocardial depression and respiratory depression. It causes severe hepatic necrosis (idiosyncratic). It is preferred in asthma as it is a bronchodilator.
C. Propofol: Action is for 15 minutes only,used in day-case surgery,dose dependent respiratory depression occurs.
D. Sevoflurane: Good for pediatric patients,pleasant even through face mask,recovery is smooth. It should not be used in closed circuit with sodalime as it is then degraded.



2. A patient was administered epidural anaesthesia with 15 ml of 1.5% lignocaine with adrenaline for hernia surgery. He developed hypotension and respiratory depression within 3 minutes after administration of block. The most common cause would be:
A. Allergy to drug administered
B. Systemic toxicity to drug administered
C. Patient got vasovagal shock
D. Drug has entered the subarachnoid space

Answer: D (Drug has entered the subarachnoid space)

Ref: KDT 4th ed, page 165,164

Quality: Reader Status: New

Explanation
Drug has entered the subarachnoid space  normally 3 ml or less is used for spinal subarachnoid block, so this high volume (e.g.-15 ml) lead to total spinal causing profound hypotension (total sympathetic block) and respiratory muscle paralysis
• Drug allergy is associated with other symptoms and signs, e.g. rashes, tachycardia, and patient may be tachyphoic.
• In an adult patient upto 500 mg of lignocaine can be given with adrenaline and here it is 225 mg only without adrenaline upto 200 mg.
• It is very uncommon to have respiratory depression with vasovagal attack.




3. The pin index code of nitrous oxide is:
A. 2,5 B. 1,5
C. 3,5 D. 2,6

Answer: C (3,5)

Ref: Sarp

Expalanation
Pin index for N2O is 3,5. Pin index is a safety mechanism it prevents attachment of the incorrect gas cylinder valve bodies to a hanger yoke on an anesthetic machine.

Other pin index are as follows:
Oxygen=2,5
CO2 (7.5% concentration) = 1,6

Tips

Pin index of N2O - 3,5
A—Air 1,5
O—Oxygen 2,5
N—Nitrogen 3,5



4. The following combination of agents are the most preferred for short day care surgeries:
A. Propofol, fentanyl, isoflurane
B. Thiopentone sodium, morphine, halothane
C. Ketamine, pethidine, halothane
D. Propofol, morphine, halothane

Answer: A (Day case surgery is used for operations less than 30 minutes and which are likely to be associated with mild post operative pain and for children too)

Discussion
In a day care surgeries patients are sent back to home on the same day of surgery. So the drug’s having shorter duration of action, minimal residual effect and having least potential for vomiting, are preferred.

• Propofel  Advantages
- Clear headed recovery
- Antiemetic property
-  post op nausea and vomiting
• Fentanyl  Shorter duration of action
• Isoflurane  Almost fully excreted uncharged through lungs  no accumulation

Thiopentine, morphine and halothane   post operative nausea and vomiting-morphine  prolonged action Ketamine  Post operative delirium.

Explanation
A. Propofol: IV inducing agent, short acting ,onset is 15-45 seconds and lasts only 15 minutes.supplemented by FENTANYL it is used for total iv anesthesia. It has got minimal residual impairment and least post operative nausea and vomiting.
Fentanyl: Short acting potent analgesic related to prthidine.used for neurilept analgesia with droperidol that is the patient remains cooperative [no unconciousness]
Isoflurane: Rapid induction and recovery,post operative nausea and vomiting is minimaldoes not lead to seizures and so is preferred for neurosurgery.
B. Tiopentone: IV inducing agent, ultra short acting, 2.5% solution used.leads to cns depression lasting more than 12 hours.,used for short operation that are not painful.
Morphine: Dangerous in patient with respiratory insufficiency.side effects are-sedation,mental clouding,and lethargy,vision blurring and respiratory depression
Halothane: Inhalational anesthetic,contraindicated in the presence of jaundice, potent GA ,poor analgesic or muscle relaxant.it leads to direct myocardial depression and respiratory depression also occurs.it causes severe hepatic necrosis[idiosyncratic].it is preffered in asthama as it is a bronchodilator.malignant hyperthermia seen sometimes,also psychomotor perfromance and mental ability decreased for hours after regaining conciousness.
C. Ketamine: Causes dissociative anesthesia,no respiratory depression,sympathetic stimulation leads to increased blood pressure,heart rate and cardiac output.But in 50% emergence delirium occurs in addirtion to hallucinations and involuntary movements.it is used in burn wound dressing
Pethidine: A opiod analgesic,side effects are like morphine,used in biliary colic and in labour.



5. Regarding neonatal circumcision, which one of the following is true:
A. It should be done without anaesthesia as it is
hazardous to give anaesthesia
B. It should be done without anaesthesia as neonate
do not perceive pain as adult
C. It should be done under local anaesthesia only
D. General anaesthesia should be given to neonate for
circumcision as they also feel pain as adult

Answer: D (General anaesthesia should be given to neonate for circumcision as they also feel pain as adult)

Quality: Spotter Status: New

Explanation
Neonates also have developed sensory system.

Comments
I think we should not waste time, discussing other options.



6. In a young patient who had extensive soft tissue and muscle injury, which of these muscle relaxants used for endotracheal intubation might lead to cardiac arrest:
A. Atracurium
B. Suxamethonium
C. Vecuronium
D. Pancuronium

Answer: B. Scoline [suxamethonium] causes an acute rise in serum potassium due to potassium eflux from cells. Cardiac arrythmia and even arrest occur in patients with burns, soft tissue injury, tetanus, myopathy, motor neuron disease etc

Ref: KDT 4th edn, page 152, Lee 12th edn, page 47

Quality: Reader Status: New

Discussion
• Extensive crush injury may lead to hyperkalemia and myoglobinuria. Suxamethonium (succinylcholine) is a depolarizing muscle blocker which also leads to hyperkalemia. So very high concentration of potassium might lead to cardiac arrest.
• Succinylcholine is contraindicated. 24 hrs to 2 years following major burns, since, it can produce profound hyperkalemia and cardiac arrest.

Explanation
A. Atacurium: 4 times less potent than pancuronium and shorter acting too,can be used in liver and kidney disease also as it is eliminated by hoffman degradation. Hemodynamically it is neutral.
C. Vecuronium: Shorter action than pancuronium, CVS stabilization better than pacuronium due to lack of histamine release action and absent ganglionic action.
D. Pancuronium: Good CVS stability nad long acting agent.



7. During laryngoscopy and endotracheal intubation which of the manoeuver is not performed:
A. Flexion of the neck
B. Extension of head at the atlanto-occipital joint
C. The laryngoscope is lifted upwards levering over the
upper incisors
D. In a straight blade laryngoscope, the epiglottis is lifted
by the tip

Answer: C (The laryngoscope is lifted upwards levering over the upper incisors)

Ref: PALS, 99th edn, page 4.16

Quality: Thinker Status: New

Discussion
• Laryngoscope blade is lifted diagradly forward.
• Levering it over the upper incisor well traumatize upper incisor
• Flexion of the neck and extention of head at the atlantooccipital joint—aligns the oral, pharyngeal and laryngeal axes so that the patway from the lips to the glottis is nearly in a straight line.
• When the epiglotisis large and overhanging (e.g. infants), straight blade (Miller blade) is used to lift the epiglottis.





8. The ideal muscle relaxant used for a neonate undergoing porto-enterostomy for biliary atresia is:
A. Atracurium
B. Vecuronium
C. Pancuronium
D. Rocuronium

Answer: A (Atracurium)

Ref: KDT 4th edn, page 154

Quality: Spotter Status: Often repeated topic

Discussion
Atracurium: 4 times less potent than pancuronium and shorter acting too,can be used in liver and kidney disease also as it is eliminated spontaneously in plasma by non enzymatic degradation [by hoffman degradation]. Hemo-dy-namically it is neutral.so liver plays no role in it metabolism.

Explanation
The metabolism of atracurium is mainly by Hoffman degradation which is non-enzymatic, pH and temperature dependent.
The metabolism of vecuronium, pancuronium and rocuronium are dependent on liver and in biliary atresia liver functions are deranged.




9. In the immediate postoperative period the common cause of respiratory insufficiency could be because of the following, except:
A. Residual effect of muscle relaxant
B. Overdose of narcotic analgesic
C. Mild hypovolemia
D. Myocardial infarction

Answer: C (Mild hypovolemia)

Ref: CMDT 2003, page 306, 307

Quality: Spotter Status: New

Discussion
Volume overload rather than hypovolumia will lead to acute respiratory failure in adult.
Myocardial infarction leads to pulmonary edema and choice A and B lead to respiratory depression.

Comments
• Residual effect of muscle relaxant may lead to recurarisation and respiratory muscle paralysis
• Overdose of narcotic analgesic can lead to direct respiratory depression
• Narcotic can also known to cause delayed respiratory depression in post operative period
• Extensive myocardial infarction may lead to respiratory insufficiency by decreasing the blood supply to respiratory centre.





10. Following spinal subarachnoid block patient a develops hypotension. This can be managed by the following means, except:
A. Lowering the head end
B. Administeration of 1000 ml of Ringers’ lactate before
the block
C. Vasopressur drug like methoxamine
D. Use of ionotrope like dopamine

Answer: A (Lowering the head end)

Ref: Lee, 12th edn, page 681

Quality: Spotter Status: High yield topic

Explanation
• Spinal subarachnoid block is usually given by hyperbaric rupivacaine or hyperbaric lignoaine/density more than that of CSF). Hypotension during spinal anaesthesia is because of sympathetic blockade. If we make the patient head down, the drug will ascent towars cephalic direction and hence the level of sympathetic block which will further increase the hypotention.
• Ringer lactate infusion will compensate for relative hypovolemic caused by sympathetic block.
• Vasopressor and ponotrophic durgs will increase BP by vasoconstriction and tachycardia.




11. The narrowest part of larynx in infants is at the cricoid level. In administering anesthesia this may lead to all except:
A. Choosing a smaller size endotracheal tube
B. Trauma to the subglottic region
C. Postoperative stridor
D. Laryngeal oedema

Answer: A (Choosing a smaller size endotracheal tube)

Ref: Lee 12th edn, page 249, 512

Quality: Thinker Status: New

Discussion
• Endotracheal tubes that pass through the glottis may still implinge upon the cricoid cartilage, causing postoperative edema, stridor, croup and airway obstruction
To pervent these complications, smaller size tube is selected.







12. All of the following factors decrease the Minimum Alveolar Concentration (MAC) of an inhalational anaesthetic agent except:
A. Hypothermia
B. Hyponatremia
C. Hypocalcemia
D. Anemia

Answer: C (Hypocalcemia)

Quality: Spotter Status: Repeat

MAC
• MAC is the minimal alveolar concentration of an anesthetic (in volume %) at which 50% of the patient will not respond to painful stimuli (eg, surgery-skin incision).
• MAC is used to compare inhalation anesthetic potency. (Similar to mg/kg for those of injectable anesthetics).
• Clinically, achieving a surgical plane of anesthesia usually requires 1.2 to 1.5 times MAC to ensure 99.9% of the patient that will not respond to the surgical stimulation.
• The lower the MAC value, the more potent the anesthetic agent.

Factors Affecting MAC
• Although all inhalant anesthetics are maintained with 1.2 to 1.5 times MAC for general anesthesia, factors that affect MAC have to be considered during the maintenance of general anesthesia.
• Factors that decrease MAC:
• Hypotension
• Anemia ( PCV < 13%).
• Hypothermia
• Metabolic acidosis
• Extreme hypoxia (PaO2 < 38 mmHg)
• Age: old animal require less anesthetic
• Premedication (opioids, sedatives, tranquilizers)
• Local anesthetics
• Pregnancy
• Hypothyroidism
• Concurrent use of nitrous oxide
• Factors increasing MAC
• Increasing body temperature - increases cerebral
metabolic rate of brain
• Hyperthyroidism
• Hypernatrimia
• Factors NOT affecting MAC
• Type of stimulation
• Duration of anesthesia
• Sex
• PaCO2 between range of 14-95 mmHg
• Metabolic alkalosis
• PaO2 between range of 38-500 mmHg
• Hypertension
• Potassium - no effect



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