Chapter 4.

Anesthesia

ANALGESIA AND SEDATION

LOCAL ANESTHESIA

Mechanism of Action

Chemistry

Toxicity and Allergy

REGIONAL ANESTHESIA IN HEAD AND NECK SURGERY

Patient Preparation

Regional Block of Scalp

Regional Block of Forehead

Infraorbital and Alveolar Nerve Blocks

Lower Incisor and Mental Nerve Blocks

Mandibular Nerve Blocks

Regional Block of Maxilla

Regional Block of Nose

Regional Block of External Ear

GENERAL ANESTHESIA

PEDIATRIC ANESTHESIA

KETAMINE

ANALGESIA & SEDATION

Current and appropriate trend in anesthesia practice

① minimize preoperative sedation : especially in very young and elderly

② relieve anxiety, analgesia, amnesia, sense of well-being while avoiding detrimental side effects

□ premedication 시 보통 사용하는 agent - sedative & tranquilizer

① flurazepam(Dalmane) : 15-30 mg p/o

② triazolam(Halcion) : 0.25-0.5 mg

# Dosage of Commonly used preoperative medications (table 4-1)

- 보통 narcotics와 sedative/tranquilizer를 병합하여 사용

1. Narcotics : morphine & meperidine

- analgesia와 함께 mild degree of sedation

- venous dilator & myocardial depressor

- bradycardia - associate to morphine --> atropine IV (0.01mg/kg)

- respiratory depression ( dose dependent )

- bronchoconstriction을 유발가능

<-- bronchus의 평활근을 직접 자극, 또는 histamine유리에 의한 간접 효과

- pontine & medullary respiratory center억제로 respiratory rate가 먼저 감소 depth는 나중에 감소

--> antagonist : naloxone (Narcan)  0.05 ~ 0.1 mg IV

- cardiac and respiratory effect of narcotics : age dependent

2. Sedatives :

① benzodiazepine compound : diazepam, lorazepam, midazolam

- C-V & respiratory side effect가 적다

- elderly patient에서는 hepatic dysfunction 초래가능

- antegrade fashion으로 amnesia가능

- IV시 mild respiratory depression가능 : tidal volume 감소, rate 증가

② butyrophenon : droperidol

- antiemetic effect, dysphoria 유발 가능

- alpha-adrenergic and dopinergic receptor blocker --> BP 감소

--> Parkinson's disease와 같이 extrapyramidal symptoms있을 시 조심

- mental detachment, apathy 유발

- action mechanism : multifactorial

--> dopamine, noradrenalin, serotonin, □-aminobutyric acid pathway를 차단

- catecholamine release에 의한 cardiac arrhythmias를 부분적으로 차단

- hepatic, renal, respiratory system에 대한 효과 없음

③ barbiturates : secobarbital, pentobarbital

- local anesthesia 시 사용되는 용량에서는 analgesic effect가 없으며, peripheral pain에 대하여 증가된 감수성을 보인다.

- cardiovascular effect : dose dependent

<-- venous dilatation에 의한 myocardial depression 초래

- medulla의 respiratory center를 억제 repiratory depression초래

--> TV감소가 main, respiratory rate usually is not affected until late

- hepatic metabolism

- antegrade amnesia

- acute intermittent porphyria 환자에서는 금기

LOCAL ANESTHESIA

1. Action mechanism

① sodium에대한 permeability를 변화 : excitation시 sodium influx를 막아 nerve transmission을 block

② surface charge theory : axonal membrane으로부터 Ca++을 제거

- Ca++-protein complex가 nerve impulse transmission에 중요

2. Chemistry : weak organic base

- 수용성을 증가시키기 위해 salt로 만듬(보통 hydrochloride salt)

- mild basic body pH에서 free base로 전환하여 more active form이 됨

--> acidic environment에서는 효과 감소 : infected or inflammed tissue

3. Toxicity & Allergy (table 4-2) : 대부분이 toxic reaction이며, true allergic reation은 드물다.

① Ester type - procaine, tetracaine

- CNS stimulation --> restlessness, agitation, excitement --> seizure

② Amide type - lidocain, mepivacain, bupivacain

- cortical depression --> drowsiness, lethargy, sleep

- very high dose --> medullary stimulation(PR↑, BP↑, RR↑)

--> 호흡장애로 사망

③ allergy : extremely rare

ⓐ ester group에만 있음

ⓑ result from hapten formation --> true anaphylactic reaction

□ lidocaine의 toxic symptom : at first - cricumoral pallor

REGIONAL ANESTHESIA IN HEAD & NECK

Patient Preparation

□ Epinephrine addition(vasoconstrictor)

① prolongs the duration of action

② delay systemic uptake

③ total dosage 의 증가

④ bleeding 감소

Regional Block of Scalp

1. Scalp regional block : trigeminal nerve(V), cervical nerve(fig 4-1,2)

2. Forehead regional block

3. Infraorbital and alveolar nerve block (fig 4-5, 4-6, 4-7)

4. Lower incisor & mental n. block (fig 4-8)

5. Mandibular n. blocks (fig 4-10,11)

6. Regional block of maxilla (fig 4-12,13,14,15)

7. Regional block of nose(fig 4-16, 4-17, 4-18)

8. Regional block of external ear(fig 4-20, 4-21, 4-22)

GENERAL ANESTHESIA

□ General anesthesia의 장점

① precise control of physiologic response

② increased control of pain & comfort

□ NPO time

① 2 ~ 6개월	4 시간

② 6개월 ~ 2세	6 시간

③ 2세 이후	8 시간

□ infant의 경우 24시간의 fluid restriction --> 10%의 body fluid loss

PEDIATRIC ANESTHESIA

□ Preoperative psychologic response

① 6개월 이전 : no psychologic problem

② 6개월 ~ 6세 ; emotional stress from parental separation & fear of pain or frightening experience

③ 6세 ~ 12세 : 수술자체에 대한 두려움

④ teenagers : tend to minimize the fear of pain or surgery, 마취에 대하여 두려움을 보임

□ Maintenance of appropriate fluid and electrolyte metabolism

□ pediatric patient의 fluid requirement(table 4-5)

□ fluid requirement = maintenance fluids + replacement of losses

1. Fluid requirements : based on caloric expenditure per body weight

--> 1ml of fluid is required per calorie

□ calory 소모량

① 10kg 이하	100 cal/kg

② 11 ~ 20kg	1000cal + 50 cal/kg

③ 20kg 이상	1500cal + 10 ~ 20 cal/kg

2. Electrolyte metabolism

- 5% dextrose with 0.2% NaCl이 적당

구성 : 3 mEq sodium, 2 mEq Chloride / 100ml

3. Blood loss

① rapid loss : repalced with blood

② slow loss : replaced with starch, Plasmanate, lactated Ringer's solution

- with careful monitoric Hct & hemodynamic parameters

□ Hct 30 이상으로 유지

□ large blood loss시 clotting paramenter의 monitoring이 필요

□ peroperative assurance of adequate fluid

<-- blood pressure, pulse, urinary output

□ epinephrine : 비교적 안전하게 사용가능

① arrhythmogenic potential : halothane과 함께 사용할 때 더 커짐

② safe margin : 10 mg/Kg

KETAMINE

1, Dissociative anesthesia : functional dissociation between the thalamoneocortical and limbic system

--> unconsciousness with analgesia, amnesia, mild sedation(clinical)

2. Rapid onset(20 ~ 60 seconds), short duration ( 2mg/kg --> 10 ~ 15분 )

3. 장점

① protective airway reflex 유지

② cardiovascular stimulation : BP, heart rate, CO 증가

<-- secondary to CNS sympathetic stimulation

--> halothane(central sympathetic blocker)으로 block 가능

③ antiarrhythmic effect

4. 단점

① adverse psychic emergence (emergnece reaction)

--> hallucination, delirium and other psychic reaction 유발가능

□ diazepam(Valium)의 사용으로 감소시킬 수 있다.

② tarchycardia시 사용하면 tachyarrhythmia 유발 가능

③ peripheral arterial baroreceptor desensitization

<-- feedback impulse를 억제 --> increase pulse & BP