Which of the following is a pleasant anaesthetic agent preferred for inhalation mask anaesthesia in children?
Ans. A. Sevolfurane. (Ref. Lee's Synopsis of Anaesthesia 13th/pg. 136)Sevoflurane, with low blood gas solubility allows rapid induction and early emergence.Due to its pleasant odor, it is nonirritant to the airway which makes it an attractive alternative for inhalational induction in children.An area where sevoflurane might be expected to find increasing use is that of laryngeal mask airway (LMA) insertion which is becoming more frequent in paediatric ambulatory surgery as this avoids some of the hazards of endotracheal intubation.Inhalational Anaesthetics# HALOTHANE# ISOFLURANE# NITROUS OXIDE# SEVOFLURANESEVOFLURANE# used widely for induction in children as is not irritant to the airway and has good cardiovascular stability# apnea can occur with prolonged use of high concentrations; use for a brief time only# emergence times are usually short following sevoflurane anaesthesia (unless administration is prolonged); ensure adequate analgesia is given to cover the early recovery period# agitation during recovery appears to be common in children# there is a theoretical risk of nephrotoxicity due to Compound A which is formed by the breakdown of sevoflurane by carbon dioxide absorbents; reduce sevoflurane degradation by avoiding prolonged use in low-flow systems (<2 L/ minute).# Induction: Up to 8% inspired concentration in oxygen with or without nitrous oxide produces surgical anaesthesia in <2 minutes.# Maintenance: 0.5-3% inspired concentration in oxygen with or without nitrous oxide; use concentrations in lower end of range when using nitrous oxide.HALOTHANE# Mode of action- Halothane is a volatile liquid anaesthetic. It's advantages are that it is potent, induction is smooth, pleasant to inhale, the vapor is not irritant to the skin and mucous membranes and does not produce necrosis when split on tissues. It suppresses salivary, mucous, bronchial, and gastric secretions and dilates the bronchioles.- IndicationsInduction but more often for the maintenance of general anaesthesia.- Specific considerationsHalothane reduces muscle tone in pregnant uterus and generally its use is not recommended in obstetrics because of the increased risk of postpartum hemorrhage.- Halothane should not be used for patients with cardiac arrhythmias.- Halothane was considered to be unsafe in patients with acute porphyria.# Adverse Effects- Cardiovascular: Halothane has a depressant action on the cardiovascular systemand reduces blood pressure; signs of overdosage are bradycardia and profound hypotension. It is also a respiratory depressant and can cause cardiac arrhythmias; there have been instances of cardiac arrest. The sensitivity of the heart to sympathomimetic amines is increased.- Hepatic: dysfunction, hepatitis, and necrosis have been reported following the use of halothane, more frequent following repeated use. Serious hepatotoxicity has limited its use in recent years.- Other: malignant hyperpyrexia, involuntary muscle movements, hiccup, coughing, bronchospasm, laryngospasm and respiratory depression.# Drug interactions1. Adrenaline: the concurrent use of adrenaline with halothane may lead to seious side effects since fatalities have been reported in some patients associated with ventricular fibrillation.2. Calcium-Channel Blockers: verapamil has been reported to cause cardiac arrest when given with halothane.3. Morphine, chlorpromazine: both drugs increase the depressant effects of halothane.4. Suxamethonium: reports of potentiation of suxamethonium-induced muscle damage by prior anaesthetic induction using halothane have been observed.# Sodium Bicarbonate: sodium bicarbonate, given to induce metabolic alkalosis, decreased total peripheral resistance during halothane anaesthsia and might lead to severe hypotension.# Dosage- Anaesthesia may be induced with 2 to 4% v/v of halothane in oxygen or mixtures of nitrous oxide and oxygen; It takes up to about 5 minutes to attain surgical anaesthesia and halothane produces little or no excitement in the induction period. For induction in children a concentration of 1.5 to 2% v/v has been used.. The more usual practice is to induce anaesthesia with an intravenous agent. Anaesthesia is maintained with concentrations of 0.5 to 2% v/v depending on the flow rate used; the lower concentration is usually suitable for the elderly.ISOFLURANE# Mode of actionThought to enhance inhibitory ion channel activity and inhibit excitatory activity in the brain to induce hypnosis and amnesia, and in the spinal cord to cause immobility in response to painful stimuli.# IndicationsInduction and maintenance of general anaesthesia.# ContraindicationsSpecific considerationsPregnancy: Limited data; ADEC category B3. Reduce maintenance dose in obstetric anaesthesia.Breastfeeding: No data.# Adverse effectsCommon: On induction, coughing, breath-holding, laryngospasm.# DosageInduction: 1.5-3% inspired concentration in oxygen and nitrous oxide produces surgical anaesthesia within 10 minutes; alternatively, start at an inspired concentration of 0.5% and increase gradually to the required level.# Maintenance: 0.5-2.5% inspired concentration in oxygen and nitrous oxide; 1.5-3.5% inspired concentration when used with oxygen alone.NITROUS OXIDEIntroduction:# in anaesthesia, it is mainly used as an adjunct to other inhalational anaesthetics, allowing them to be used at lower concentrations# it is a weak anaesthetic but has strong analgesic properties; used in subanaesthetic concentrations in obstetrics, emergency care and procedures not requiring loss of consciousness; premixed nitrous oxide 50% and oxygen 50% alone is suitable for self-administration# prolonged inhalation can inactivate vitamin B12 and interfere with DNA synthesis causing haematological and neuro- logical adverse effects; avoid exposures of >6 hours# whether or not chronic low level occupational exposure is harmful to staff remains unresolved; control nitrous oxide pollution using a scavenging system and effective ventilation# protect cylinders containing 50% nitrous oxide and 50% oxygen from the cold; if cooled to temperatures < -7degC, liquid nitrous oxide separates and may require remixing before use# Mode of actionNitrous oxide is an anesthetic administred by inhalation. It is a weak anaesthetic with minimum alveolar concentration value of 110%. It has strong analgesic properties, but produces little muscle relaxation.# IndicationsNitrous oxide is used as an adjuvant to other anaesthetics and permits them to be used at a significantly reduced dosage. It is given with oxygen for anaesthesia especially in obstetrics. Recovery is usually rapid from nitrous oxide anaesthesia.# Specific considerationsAir-containing cavities (e.g. middle ear occlusion, abdominal distension, pneumothorax, air embolus), or during or after pneumoencephalography or vitreoretinal surgery involving gases such as sulphur hexafluoride: risk of increased pressure and/or volume within such cavities.Vitamin B12 deficiency: increased risk of neurological dysfunction, including subacute combined degeneration of the spinal cord with prolonged exposure.Pregnancy: Safe to use; ADEC category A.# Adverse effectsThe main complications are those due to varying degrees of hypoxia..Rare: With prolonged (eg >24 hours) or repeated use: megaloblastic anaemia, leucopenia, agranulocytosis, neuropathy, myeloneuropathy.DosageInduction: 70% with 30% oxygen, (in combination with other anaesthetic agent).Maintenance: 30-70% with oxygen, (in combination with other anaesthetic agent).Analgesia: 25-50% with oxygen.
Sevolfurane
Desflurane
isoflurane
Enflurane
General Anesthesia