All about general anesthesia

By Dr. Aparna Jayara Pg 1st year GMC haldwani

Definition

• General anesthesia is described as a reversible state of unconsciousness with inability to respond to a standardized surgical stimulus.

• In modern anesthetic practice it involves a triad of unconsciousness analgesia and muscle relaxation .

Brief history

General anesthetics have been performed since 1846 when Morton demonstrated the first anesthetic (using ether) in Boston, USA. Local anesthetics arrived later, the first being scientifically described in1884.

Difference b/w GA, LA and Conscious sedation.

General Anesthesia Local Anesthesia Conscious Sedation

A 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 patient’s 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.

General Anesthesia

• Assessment (i.e. PAC)

• Planning I: Monitors

• Planning II: Drugs• Planning III: Fluids• Planning IV: Airway

Management

• Induction• Maintenance• Emergence• Postoperative

Pre anesthetic check up• History of presenting illness• Past history ( medical history/ surgical history/

blood transfusion history) , h/of any mode of anesthesia in past

• Drug history• Personal history• Complete General physical examination (airway

assesment and exanmination of spine)• Systemic examination (CNS,CVS,RESPI.)

PAC (cont..)

• Investigations • CBC• RBS• Coagulation profile• LFT• KFT• Viral markers• Other investigations if needed ( thyroid profile, lipid

profile)

Airway assesment

• Mallampati score• Assesment of atlanto occipital extension• Upper lip bite test• Interincisor gap• Thyromental distance • Hyomental distance• Sternomental distance• Mandibular protrusion test

Mallampati Score

• Class I (easy)—visualization of the soft palate, fauces, uvula, and both anterior and posterior pillars

Class II—visualization of the soft palate, fauces, and uvula

Class III—visualization of the soft palate and the base of the uvula

Class IV (difficult)—the soft palate is not visible at all

Sensitivity: 44% - 81%Specificity: 60% - 80%

Difficult intubation

• More than 3 attempts• Longer than 10 minutes• Failure of optimal best attempt

Physical status classification (ASA)• Class I: A normal healthy patients• Class II: A patient with mild systemic disease (no functional limitation)• Class III: A patient with severe systemic disease (some• functional limitation)• Class IV: A patient with severe systemic disease that is a constant threat to life (functionality incapacitated)• Class V: A moribund patient who is not expected to survive without the operation• Class VI: A brain-dead patient whose organs are being removed for donor purposes• Class E: Emergent procedure

Anesthetic plan

Premedication Intraoperative Postoperative management managementGeneral Monitoring Pain control PONV Airway management Positioning Complications Induction Fluid management postop ventilation Maintenance Special techniques Hemodynanic monitorin Muscle relaxation

NPO status

• NPO, Nil Per Os, means nothing by mouth• Solid food: 8 hrs before induction• Liquid: 4 hrs before induction• Clear water: 2 hrs before induction• Pediatrics: stop breast milk feeding 4 hrs before induction

• ANTI-PSILOGOGUS• ANTI-EMETIC• ANTI-HISTAMINIC• ANTA-ACID• ANALGESIC• AMNESIA• ADDITIVE

PRE MEDICATION

• INDUCTION

• MUCSLE RELAXATION

• INTUBATION

• VENTILATION

• REVERSAL

STEPS OF ANESTHESIA

Induction

Let the pt go off to sleepPreoxygenation

8L~10L/min

IV or Inhalational

induction

Airway management

Induction techniques

• Intravenous: the most common method ( with thiopentone, propofol, ketamine etc.)

• Inhalation: for special pt (as pt with difficult airway, pediatric pt)

• Intramuscular :rarely used, only used in uncooperative pts and young children

Induction agents

• Opioids – fentanyl• Propofol, Thiopental and Etomidate• Muscle relaxants: Depolarizing Nondepolarizing

Maintenance

Increasing depth of anesthesia

stageⅠ

Amnesia

Loss of

consciousness

Stage ⅡDelirium

Injurious responses

to noxious stimuli

Stage Ⅲ

Surgical anesthesia

Painful stimulation does

not elicit somatic reflexes

or deleterious autonomic

responses

Stage Ⅳ

Overdosage

Circulatory

failure

Maintenance Anethesia

• Volatile anesthestic ( halothane, sevoflurane,isoflurane)

• Nitrous oxide-opioid relaxant technique

• IV anesthesia

• Combinations

• Maintain homeotasisVital signsAcid-base balanceTemperatureCoagulationVolume status

Maintain Ventilation

1. Spontaneous or assisted ventilation

2. Controlled ventilation Tidal volume: 10-12ml/kg Respiratory rate: 8-10 breaths/min

Maintain Intravascular Volume

1. fluidsCrystalloid sollutions:Colloid sollutions:

2. Blood & blood products

• PULSE• BP• SPO2• ETCO2• TEMPERATURE• GLUCOSE• ECG

MONITORING

Emergence

• Turn off the agent (inhalation or IV agents)• Reverse the muscle relaxants• Return to spontaneous ventilation with

adequate ventilation and oxygenation • Suction upper airway• Wait for pts to wake up and follow command• Hemodynamically stable

Postoperative management

• Post-anesthesia care unit (PACU) - Oxygen supplement - Pain control - Nausea and vomiting - Hypertension and hypotension

- Agitation • Surgical intensive care unit (SICU) - Mechanical ventilation - Hemodynamic monitoring

General Anesthesia Complications and Management

• Respiratory complication - Aspiration – airway obstruction and pneumonia - Bronchospasm - Atelectasis - Hypoventilation• Cardiovascular complication - Hypertension and hypotension - Arrhythmia - Myocardial ischemia and infarction - Cardiac arrest

General AnesthesiaComplication and Management

• Neurological complication - Slow wake-up - Stroke

• Malignant hyperthermia

Goals to be met before discharge from recovery:

awake Responsive Full muscle strength Adequate pain control WAIT TILL PATIENT CAN BREATH ON ROOM

AIR MINIMUM FOR 5 MINCONSCIOUSRESPONDINGREGULAR RESPIRATIONRRGULAR HRNORMAL BP

Advantages of general anesthesia1. Patients cooperation in not absolutely

essential for the success of GA.2. Patient is unconscious.3. Patient does not respond to pain.4. Amnesia is present.5. GA may be the only technique that will prove

successful for certain patients.6. Rapid onset of action.7. Titration is possible.

Disadvantages of general anesthesia1. The patient is unconscious.2. Protective reflexes are depressed.3. Vital sign are depressed.4. Advanced training is required.5. An ‘‘anaesthesia team’’ is required.6. Special equipment is required wherever general

anaesthesia.7. A recovery area must be available for the patient.8. 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 anesthesia1. Lack of adequate training by the doctor.2. Lack of adequate trained personnel.3. Lack of adequate equipment.4. Lack of adequate facilities.5. ASA IV and certain ASA III medically

compromised patients.

Indications for general anesthesia1. Extreme anxiety and fear.2. Adults or children who have mental or

physical disabilities, senile patients, or disoriented patients.

3. Age-infants and children.4. Short, traumatic procedures.5. Prolonged traumatic procedures.

Thank you