General anaesthesia

General anaesthesia Presented byDr Ravneet kour

ReferencesGuidelines for the Use of Sedation and General Anesthesia by Dentists. ADA. 2012:1-14

C. Langton Hewer the stages and signs of general anaesthesia. Br Med J. 1937;2(3996):274-276

Lola Adewale. Anaesthesia for paediatric dentistry. Cont Edu Anaesth Crit Care Pain.2012;12(6):288-94

Guideline on Use of Anesthesia Personnel in the Administration of Office-based Deep Sedation/General Anesthesia to the Pediatric Dental Patient. AAPD. 2015;37(6):228-31

Naveen Malhotra. General Anaesthesia for Dentistry. Indian J Anaesth 2008;52:Suppl (5):725-737

Difference b/w GA, LA and Conscious sedation.General AnesthesiaLocal AnesthesiaConscious SedationA drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation. The ability to independently maintain ventilatory function is often impaired. Patients often require assistance in maintaining a patent airway.The elimination of sensation, especially pain, in one part of the body by the topical application or regional injection of a drug.A minimally depressed level of consciousness that retains the patients ability to independently and continuously maintain an airway and respond appropriately to physical stimulation or verbal command and that is produced by a pharmacological or non-pharmacological method or a combination thereof.

American Society of Anesthesiologists (ASA) Patient Physical Status ClassificationASA I A normal healthy patient.ASA II A patient with mild systemic disease.ASA III A patient with severe systemic disease.ASA IV A patient with severe systemic disease that is a constant threat to life.ASA V A moribund patient who is not expected to survive without the operation.ASA VI A declared brain-dead patient whose organs are being removed for donor purposes.E Emergency operation of any variety (used to modify one of the above classifications, i.e., ASA III-E).

-Indian J Anaesth 2011;55:111-5

Routes of Administration

Oral A technique of administration in which the drug is administered through mouth.

, popular drug used at the present time is sodium pentothal

a.

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Stages of general anesthesia

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Guedel observations

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Gillespie 1943

Patient remains conscious and capable of responding to commands.Patient is relaxed and cooperative, with decreased awareness of surroundings.Respiration is normal.Eye movement are normal, with voluntary movement possible.protective reflexes are intact.Amnesia may or may not be present. Patient may exhibit diminished sense of time.Patient able to maintain patent airway.Stage I ends and stage II starts when patient is unable to respond appropriately to command or the protective reflexes are diminished.There are no objective sign that reliably indicates this transition from stage I to stage II.An oft-used sign of this transition is eyelid reflex.Gentle stroking of the eyelashes provokes lid closure in conscious patient. Lack of this stimulus denote entry of patient in stage II of anaesthesia.

Stage II: Delirium (ultralight general anesthesia)Degree of CNS depression is greater than stage I, consciousness is lost.Stage II begins with the loss of consciousness & progresses until entry into the stage of surgical anaesthesia.Respirations are irregular early in stage II but becomes more regular as stage II deepens.Eyeballs oscillate involuntarily, a movement termed lateral nystagmus.Pupils react to light normally.Skeletal muscle tonus is increased, with muscular rigidity present in some patients early in stage II The laryngeal and pharyngeal reflexes are still active early in stage II but become progressively more obtunded as stage II progresses.Physical restrains are usually require.Amnesia present in this stage.When stage III is the goal, it is the practice to induce anaesthesia rapidly so as to pass through stage II as quickly as possible , thereby minimizing overreaction to stimulation

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Stages of General Anesthesia

Advantages of general anesthesiaPatients cooperation in not absolutely essential for the success of GA.Patient is unconscious.Patient does not respond to pain.Amnesia is present.GA may be the only technique that will prove successful for certain patients.Rapid onset of action.Titration is possible.

Disadvantages of general anesthesiaThe patient is unconscious.Protective reflexes are depressed.Vital sign are depressed.Advanced training is required.An anaesthesia team is required.Special equipment is required wherever general anaesthesia.A recovery area must be available for the patient.Intaoperative complications are more likely to occur during general anaesthesia than during conscious sedation.

9. Postanesthetic complications are more common following general anaesthesia than after conscious sedation

10. The patient receiving general anaesthesia must receive nothing by mouth for 6 hours before the procedure.

11. Patients receiving general anaesthesia must be evaluated more extensively preoperatively than patients receiving conscious sedation.

Contraindications for general anesthesiaLack of adequate training by the doctor.Lack of adequate trained personnel.Lack of adequate equipment.Lack of adequate facilities.ASA IV and certain ASA III medically compromised patients.

Indications for general anesthesiaExtreme anxiety and fear.Adults or children who have mental or physical disabilities, senile patients, or disoriented patients.Age-infants and children.Short, traumatic procedures.Prolonged traumatic procedures.

PremedicationDrugDosageRoute of administrationFeaturesOpioidsMorphine 10mgPethidine 50-100mgIMReduces anxiety, produce pre & postoperative analgesia, reduce the dose of anesthetic required,.Disadvantage: depressed respiration, fall in BP, lack of amnesia, delayed gastric emptying.

Sedative anxietyDiazepam 5-10mgLorazepam 2mgOralIMProduce tranquility and smooth induction.Disadvantage: loss of recall of postoperative events, accentuation of postoperative vomiting.Anti-cholinergicsAtropine 0.6mgIMTo reduce salivary & bronchial secretions.Disadvantages: dryness of mouth in pre & postoperative period may be distressing disadvantage.

NeurolepticsChlorpromazine 25mgHaloperidol 2-4mg IM Allay anxiety, & antiemetic action.H2 blockersRanitidine 150 mg Oral used for long procedures, cesarean section, obese patients at increased risk of gastric regurgitation.AntiemeticsMetoclopramide 10-20mg IM effective in reducing postoperative vomiting.Disadvantages: motor restlessness.

Monitoring equipments during general anesthesia Pulse oximeterSphygmomanometer TemperaturePrecordial stethoscope for monitoring of heart sound.Pretracheal stethoscope for monitoring of respiration.

Drugs used for anesthesiaInhalation Intavenous Gas: nitrous oxideInducing agents: Thiopentone sodium, methohexitone sodium, propofol, etomidateVolatile liquids: ether, halothane, isoflurane, desflurane, sevoflurineSlower acting drugs: diazepam, lorazepam, midazolam Dissociative anaesthesia: ketamineOpioid analgesia: fentanyl

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INHALATION ANESTHESIA

Sevoflurane Sevoflurane supplementation of 66% nitrous oxide in oxygen is used.

Sevoflurane may either be introduced in 2% increments every 2 to 3 breaths to a maximum of 8%, with maintenance of anaesthesia at or around 4%, or it may be introduced at the maximum concentration of 8%, with maintenance at 4%.

Sevoflurane became available and in comparison to halothane as it is associated with less myocardial depression and fewer and less significant respiratory problems when used for inhalational induction.

Diethyl etherProduces Good anelgesia & marked muscle relaxation. Highly soluble in blood .Recovery is slow. Postanesthic nausea, vomiting.Ether is not used in developing countries because of its unpleasent and inflammable properties.

Nitrous oxide Colourless, odourless, heavier than air, non-inflammable gas.Onset of action is quick & smooth. A mixture of 70% N2O+ 25-30% O2 + 0.2-2 % another potent anesthetic is employed for most surgical procedures. In this way concentration of other anesthetics can be reduced to 1/3 for the same level of anesthetic.

INTRAVENOUS ANESTHESIA

Methohexitone sodiumUltra short acting barbiturate with rapid onset.IV dose of 0.75 to 1 mg/kg produces sleep like state without spontaneous movements within 1min, patient wake up in 10min.

Diazepam/lorazepam DOSAGE: Oral 0.2 to 0.5 mg/kg to a maximum single dose of 10 mgIV0.25 mg/kgSUPPLIED: Tablets-2, 5, and 10 mgSuspension5 mg/ml

Midazolam DOSAGE: Oral0.25 to 1.0 mg/kg to a maximum single dose of 20 mgIM0.1 to 0.15 mg/kg to a maximum dose of10 mgIVslow IV titration; see manufacturer's recommended dosage guidelinesSUPPLIED: Syrup2 mg/mlInjectable1 mg/ml and 5 mg/ml vials

Fenatanyl Oset is 30 sec IV & 5-10min IMPeak effect is 10min IV & 30-45 min IM.Duration of action: 30-60 minDOSAGE: 0.002 to 0.004 mg/kg SUPPLIED: 0.05 mg/ml in 2- and 5-ml ampules.

Ketamine Induces so called dissociative anaesthesia Dose 3mg/kg IV or 5mg/kg IMRecovery starts within 10-15min, but patient remain amnesic for 1-2 hours.

Propofol Fast acting.Also called as milk of amnesia.Veerkamp et al.(1997) published an account of an exploratory study where children, mainly with nursing bottle caries, had teeth removed using propofol administered by an anesthetist.Recently involved agent in death of MICHEAL JACKSON due to overdosing.IV 2.5-3.5mg/kg Oral dose is 50mg/kg with range of 40-60mg/kgDuration of action is 2-5hours.

Reversal agentsSpecific reversal agents exists for benzodiazepines and opioids.

Flumazenil- 0.01 mg over 15sec, may be repeated at 1 min as needed.

Naloxone- 0.4mg initially followed by 0.1mg-0.2mg every 2-3min for children under 20 kg and dose for children over 20 kg is 2mg.

Preoperative instructions

Postoperative instructions

Discharge criteria 1. Cardiovascular function is satisfactory and stable.2. Airway patency is uncompromised and satisfactory.3. Patient is easily arousable and protective reflexes are intact.4. State of hydration is adequate.5. Patient can talk, if applicable.6. Patient can sit unaided, i f applicable.7. Patient can ambulate, i f applicable, with minimal assistance.8. If the child is very young or disabled, incapable of the usually expected responses, the presedation level o f responsiveness or the level as close as possible f or that child has been achieved.9. Responsible individual is available.

Criteria for giving GAPatient in operatory with preoperative instructions followed.Check for the vital signs and evaluate the status of health of the patientPremedicationInduction of general anaesthesiaIntraoperative monitoringReversal of anaesthesia in indoor unitPost operative instructionsFollow up

SummaryGA is a technique that require significantly greater training on the part of doctor and staff in order to be safe.The indication for GA in dentistry have diminished over the years as techniques of conscious sedation have evolved.The selection of most appropriate type of general anaesthesia for use in given patient must be made after a thorough evaluation of patients physical condition, planned dental treatment & preparedness of the facility.