General Anesthesia

• Course: MEDI045

General Anesthesia

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.

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

In modern anesthetic practice this involves the triad of: unconsciousness, analgesia, muscle relaxation.

Content:

• Assessment
• Planning I: Monitors
• Planning II: Drugs
• Planning III: Fluids
• Planning IV: Airway
  
  Management
• Induction
• Maintenance
• Emergence
• Postoperative
  
  Objectives of anesthesia
• Unconsciousness
• Amnesia
• Analgesia
• Oxygenation
• Ventilation
• Homeostasis
• Airway Management
• Reflex Management
• Muscle Relaxation
• Monitoring
• Role Of Anesthetists
• Preoperative evaluation and patient preparation
• Intraoperative management
  
         - General anesthesia
  
                 Inhalation anesthesia
  
                 Total IV anesthesia
  
         - Regional anesthesia & pain management
  
                 Spinal, epidural & caudal blocks
  
                 Peripheral never blocks
  
                 Pain management (acute and chronic pain)
• Postanesthesia care (PACU management)
• Anesthesia complication & management
• Case study
  
   
  
  Preoperative anesthetic evaluation
  
  Risks of Anesthesia
• Physical status classification
• 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
  
  Premed  
  
                                   Intraoperative             Postoperative
  
                                    management                management
  
  General                    Monitoring                Pain control
  
                                                                      PONV
  
    Airway management       Positioning                  Complications
  
    Induction                          Fluid management        postop ventilation
  
    Maintenance               Special techniques        Hemodynanic monit
  
     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
• General Anesthesia

1. Monitor
2. Preoxygenation
3. Induction ( including RSI & cricoid pressure)
4. Muscle relaxants
5. Mask ventilation
6. Intubation & ETT position comfirmation
7. Maintenance
8. Emergence

 

   Airway exam

Mallampati classification

 

Class I:

uvula, faucial pillars, soft palate visible

Class II:

faucial pillars, soft pillars visible

Class III:

soft and hard palate visible

Class IV:

hard palate visible

 

• Induction agents
• Opioids – fentanyl
• Propofol, Thiopental and Etomidate
  
   
  
  Muscle relaxants:
• Depolarizing
• < >IV induction
• Inhalation induction
  
   
  
  General Anesthesia
• Reversible loss of consciousness
• Analgesia
• Amnesia
• Some degree of muscle relaxation
  
   
  
  Intraoperative management
• Maintenance
  
          Inhalation agents: N2O, Sevo, Deso, Iso
  
          Total IV agents: Propofol
  
          Opioids: Fentanyl, Morphine
  
          Muscle relaxants
  
          Balance anesthesia
  
   
• Monitoring
• Position – supine, lateral, prone, sitting, Litho
• Fluid management
  
        - Crystalloid vs colloid
  
        - NPO fluid replacement: 1st 10kg weight-
  
           4ml/kg/hr, 2nd 10kg weight-2ml/kg/hr and
  
           1ml/kg/hr thereafter
  
        - Intraoperative fluid replacement: minor
  
           procedures 1-3ml/kg/hr, major procedures 4-
  
          6ml/kg/hr, major abdominal procedures 7-10/kg/ml
  
   
  
  
  
  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 Anesthesia
  
  Complication and Management
• Neurological complication
  
           - Slow wake-up
  
           - Stroke
• Malignant hyperthermia
• 
  
  Case Report
  
  
  
  Arterial oxygen desaturation following PCNL
  
  The Patient
• Patient : 73 y/o Female
  
                     BW 68 kg, BH 145 cm (BMI 32)
• Chief complaint :
  
   Right flank pain (stabbing, frequent attacks)
  
   General malaise and fatigue
• Past history : Hypertension under regular control
  
                          Senile dementia (mild)
  
                                 
• Preoperative diagnosis : Right renal stone (3.2 cm)
• Operation planned : Right PCNL (percutaneous nephrolithotomy)
  
  Preanesthesia Assessment                  
• EKG : Normal sinus rhythm
• CXR : Borderline cardiomegaly & tortuous aorta
• Lab data : Hb 10.5 / Hct 33.2
  
                      BUN 24 / Creatinine 1.1
  
                      GOT 14
  
                        PT, aPTT WNL
  
  Anesthetic Technique
• General anesthesia with endotracheal intubation
• Standard monitoring apparatus for ETGA
• Induction : Fentanyl ug/kg
  
                        propofol  2mg/kg
  
                        Succinylcholine 80 mg
  
                        Atracurium 25 mg
• Endotracheal tube (ID 7.0-mm) @ 19cm
•  
  

  Intra-operative Events

  
  
  Maintenance: Isoflurane 2~3% in O2 0.5 L/min

• Position: prone
• Blood loss : 300 mL → PRBC 2U
  
   
  
  Intra-operative Events
• Stable hemodynamics
• Abnormal findings 30 minutes after surgery started
  
  Increased airway pressure 35~40 mmHg
  
  SpO2 dropped to 90~95%
• Bilateral breathing sounds were still audible then
• Management : Solu-cortef 100 mg IV stat
  
                            Aminophylline 250 mg IV drip
  
                            Bricanyl 5 mg inhalation
  
  ABG
  
  PH 7.2
  
  PaO2 90.5
  
  PaCO2 66.8
  
  HCO3 26
  
   
  
  Postoperative
• The patient’s condition was kept up until the end of surgery
• SpO2 90~92% after the patient was placed in the supine position
  
     again with diminished breathing sound over right lower lung
• The patient was transferred to SICU for further care (*)
• Chest X-ray was followed in SICU
  
   
  
  Postoperative Course
• Pigtail drainage in SICU
• Pleural effusion : bloody
  
                RBC numerous
  
                WBC 7800 (Seg 94%)
  
                Gram stain (-)
• Impression : Right hydrothorax and hemothorax
• Extubation and transfer to ordinary ward
• Pigtail removed