Anesthesia study notes

• This is a collection of study notes on Anesthesia.

Anaesthesia Revision - 1

• During pre-anesthesia check-up, ensure to ask about the patient's past medical and personal history.

• Treatment plan for co-morbid conditions prior to surgery:

  • For hypertension, continue antihypertensives until the surgery day, except ACE inhibitors and ARBs, which can cause severe hypotension. ACE inhibitors and ARBs can be continued for minor surgeries with minimal blood loss
  • For diabetes mellitus, discontinue OHA and insulin, SGLT-2 inhibitors 24 hours prior. Start short acting insulin intra-op.
  • For Epilepsy, continue antiepileptics until the surgery day. Baseline liver function tests should be performed.
  • For thyroid disorders, continue medications until the day of surgery. Correct hypothyroidism and hyperthyroidism.
  • For psychiatric problems, continue antipsychotics, apart from MAO inhibitors, which should be stopped 3 weeks before.

• Treatment plan for medications prior to surgery

  • For oral contraceptives, consider the risk of DVT. Can continue if low risk, but stop if high risk.
  • If the LFTs are abnormal, delay the surgery for 1-2 weeks in patients taking Herbal medicine.
  • Continue anti-tubercular therapy, but check LFT. Sildenafil should be stopped 24-48 hours before.

• Treatment plan for medications requiring special modifications prior to surgery

  • Diuretics should be stopped - exceptions and thiazides
  • Anticoagulants must be discontinued
    • Aspirin, Clopidogrel, Warfarin
    • Bridging with LMWH is necessary, follow necessary requirements for surgery

Personal, family and allergy

• Tobacco chewing causes chances of difficult intubation due to restricted mouth opening.
• For Malignant hyperthermia, know the etiology, risk factors and pathophysiology
• In a patient with allergy, there is a presentation of sudden tachycardia and bronchoconstriction.
• For a patient presenting with this, they should be placed on 100% O2, and treated with Adrenaline and Hydrocortisone.

Airway Examination

• Finger breadth technique to assess mouth opening.
• Use the OBESE mnemonic while determining predictors for difficult intubation
• Mallampati scoring to determine visualization

ASA Grading

• ASA grading determines pre-operative investigation
• They are graded based on functional capacity

Anaesthesia Revision - 2

• Bispectral Index of 40-60 is the recommended range for general anesthesia

CVS monitoring

• ECG detects arrhythmias using Lead II
• Non-Invasive measurements of the CVS involved methods like sphygmomanometer
• Invasive measurements are used during major surgeries

Central Venous Catheter

• Pulmonary artery catheter provides details of the functioning for the left heart
• Long term IV cannulation for TPN, inotropes and cardiac medications
• Measures functioning of right heart

Risks of the Central Venous Catheter

• Pulmonary capillary rupture
• Arrhythmias

RS monitoring

• Pulse oximeter measures oxygenation
• Capnography monitors exhaled CO2

Capnography

• Mainstream and sidestream are two methods
• Pulse Oximetry emits red and infrared lights
• Has limitations
• Can experience waveform abnormalities

Waveform abnormalities

• Bronchospasm increases upstroke of Phase III
• Hypoventilation is commonly seen in opium poisoning
• Malignant hyperthermia has a step ladder pattern

Temperature Monitoring

• Used to detect Hypothermia or Hyperthermia
• Done using the tympanic membrane or pulmonary artery

Neuromuscular monitoring:

• Aids in checking the adequate muscle relaxation post surgery
• TOF Ratio of > 0.9, indicates recovery from muscle relaxant

Anesthesia Revision - 3

General anesthesia

• Uses drugs in Intravenous and Intranasal routes
• muscle relaxants
• analgesics

Intravenous Induction Agents

• Generally Depressants
• Affects GABA receptors
• Leads to chloride conductance

Barbiturates

• Has antiepileptic actions
• except methohexital

Thiopentone Sodium

• Yellow powder that smells of Garlic
• Effected in 15 sec
• Termination of action via redistribution
• Brain = Fat
• use
  • Neurosurgeries
  • Truth serum
• Causes severe complication

methohexital

• has proconvulsant disadvantages
• used in electroconvulsive therapy

General

• Characteristics include
• maintain depth of anesthesia.
• Induce sleep (Paediatric).
• Depressants.
• Enter & exit the circulation via lungs.

Anaesthesia Revision - 4

• Aids in intubation/Surgical relaxation

Depolarizing Muscle Relaxants (DMR)

• Non competitive blockade
• metabolised by pseudocholinesterase
• Bradyarrhythmia
• cause muscle fasciculations

Reasons for prolonged duration of action:

• ↓Concentration of PCE
• ↓PCE enzyme activity
• Phase II block

Non Depolarizing muscle Relaxants (NDMR)

• Are available in two types
• Steroidal compounds.
• Benzylisoquinolone compounds. Neostigmine
• Administered on spontaneous breathing
• side effects cause Bradycardia

Anaesthesia Revision 5

• Suugamadex
• cyclodextrin molecule used to reverse vecuronium/Rocuronium
• Contraceptive Failure
• signs of adequate reversal can be determined
• Able to hold tongue depressor between incisors

Paediatric

Considerations in Anaesthetic factors

• Propfol
• Sevoflurane

Complication

• Drowsiness/Vomiting
• Caused by haemorrhage

Caudal Anaesthesia

• No risk of chord injury
• Is for patients for patients only
• Can cause infection

The End