basic practice of anesthesiology final

8/13/2019 Basic Practice of Anesthesiology Final

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Basic Practice ofAnesthesiology

Hany El-Zahaby, MD


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Preoperative Evaluation1. History

-Currentproblem

-Other known problems

-Medical history (allergies, drug intolerance, presenttherapy, tobaccoand alcoholintake)

-Previous anesthetics, surgeries, deliveries

-Family history

-Review of organ systems

-Last oral intake


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Preoperative Evaluation

2. Physical Examination

-Vital signs

-Airway (Thyromental distance, Malampatisign)

-Heart

-Lungs

-Extremities

-Neurological examination


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3. Routine Laboratory evaluation (healthy

asymptomatic)

Hematocrite: All menstruating women, age >60 y,

anticipated significant blood loss

S. glucose, creatinine: age >60 y

ECG: age >40 y

Chest radiograph: age >60 y

Pregnancy test: fertile women


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merican Society of nesthesiologyRisk Classification

DescriptionASA Class

Normal, healthy (0.06-0.08%)1

Mild systemic disease (0.27-0.4%)2

Severe systemic D, not incapacitating (1.8-4.3%)3

Severe systemic D that is a constant threat to life

(7.8-23%)

4

Moribund, not expected to live 24h (9.4-51%)5

Care for organ donation6


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The Anesthetic Plan Premedication

Type of anesthesia

General (airway, induction, maintenance, relaxant)

Regional (technique, agents) Intraoperative management

Monitoring, positioning, fluids, MABL, specialtechniques

Postoperative management

Pain control, ICU (ventilation, monitoring)


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Informed consent

Gives the patient explanation of the options for

anesthesia and its realistic risks (general, regional,

local, topical, intravenous sedation)

Regardless of the technique chosen, consent must

always be taken for GA if other techniques prove

inadequate e.g. LA


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The Anesthetist-Patient relationship

Is The Patient Scared?

Surgery (cancer, physical disfigurement, pain, death)

Anesthesia (loss of control, not waking up, waking up

during surgery, nausea, confusion, paralysis,

headache)


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1-Unhurried, organized interview

2-Calm reassurance and expression of interest in the

patients well being

3-Informing about:

NPO (no solids after m.n., clear fluids up to 2-3 h

unless GER)

Time of surgery

Premedication and other daily medications

Tasks to occur on the day of surgery

Postoperative recovery or ICU


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Premedication

Benzodiazepines:

Diazepam (5-10 mg PO 1-2 hours before surgery),

never IM (pain, unpredictable)

Lorazepam (1-2 mg PO), intense prolonged amnesia

and sedation

Midazolam (1-3 mg IV or IM) at the receiving area, 0.5

mg/kg PO for pediatrics


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Premedication

Narcotics: painful fractures, planned extensive awake

invasive monitoring devices

Morphine 5-10 mg IM 60-90 min before surgery

Anticholinergics (rare): Not Routine

Glycopyrrolate 0.2-0.4 mg IV to reduce oral

secretions (fibreoptic intubation)


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Premedication

Prophylaxis for pulmonary aspiration:

Pregnant, hiatal hernia, GER, difficult airway, ileus,obesity, CNS depression

H2blockers (ranitidine, 150-300 mg PO beforebedtime and early morning)

Nonparticulate antacids (sodium citrate 30-60 ml)

Metoclopramide (10 mg IV 1h before surgery to

enhance gastric emptying)


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Premedication

Goals: Reduce anxiety, pain during vascular

cannulation and regional blocks, facilitate smooth

induction

Reduce the dose or withhold in elderly, debilitated,upper airway obstruction or trauma, central sleep

apnea, neurologically obtunded, severe pulmonary

or obstructive valvular disease


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Monitoring

Standard monitoring for GA:

ECG, non-invasive BP, respiratory rate, oxygen

saturation, end-tidal carbon dioxide, inspired oxygen

concentration

Standard monitoring for regional anesthesia:

ECG, non-invasive BP, respiratory rate, oxygen

saturation


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IV access

IV access: (14-16 G if rapid fluid or blood transfusion or

continuous drug infusions, better under local

anesthetic infiltration)


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Components of GA

Loss of consciousness

Loss of reflexes (Movement to pain)

Analgesia

Amnesia

Relaxation


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Induction of Anesthesia

The environment in OR should be warm with minimal

noise and all attention focused on the patient

Supine position with extremities in neutral position and

head on firm pillow raised to sniff position


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Induction of Anesthesia

Techniques:

1- IVinduction preceded by oxygen via face mask untilloss of consciousness using thiopentone or propofol

2- Inhalationalanesthetics either by low concentrationwith incremental increase every 3-4 breaths or by asingle vital capacity breath technique usingsevoflurane or halothane


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Intravenous Induction

PropofolThiopentone

2-2.5mg/kg3-5mg/kg

IVI 6-10 mg/kg/h---

Painful injection---

Rapid induction, rapid clear-

headed recovery

Slower onset, slower recovery

Hypotension +++Hypotension ++

Depress respirationDepress respiration

Less N,VContraindicated in porphyria


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Airway Management

Face-mask with:

Oro-pharyngeal airway

Naso-pharyngeal airway

LMA

ETT with a muscle relaxant (depolarizing as succinyl

choline or non-depolarizing as tracrium, cistracrium,

rocuronium)


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Muscle Relaxants

Depolarizing MR (succinylcholine) mimics the action

of acetylcholine i.e. causes depolarization of the

motor end plate and muscle membrane but for

longer time than Ach. Used for rapid-sequenceinduction in patients with full stomach

Non-depolarizing MR produce reversible competition

with Ach at the motor end plate that produce

relaxation for longer duration


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Succinylcholine

Dose:1mg/kg produce relaxation in 1 min

Side effects:

Muscle pains, ganglionic stimulation, increase S. K+

level by 0.5-1 mEq/L, increase intraoccular pressure,increased intragastric pressure, increase intracranialpressure, prolonged block due to decrease orinhibition or atypical plasma cholinesterase,malignant hyperthermia


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Non-Depolarizing MR

Atracurium: 0.5 mg/kg, Hofmann elimination

Cisatracurium (Nimbex): 0.15 mg/kg, Hofmann

elemination, less histamine release

Vecuronium: 0.1 mg/kg, hepatic metabolism

Rocuronium (Esmeron): 0.5 mg/kg, hepatic metabolism

(short duration)


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TOF


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Twitch Height After Succinyl Choline


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Twitch Height After Non-Depolarizing


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Clinical Assessment of the Blockade

Clinical correlateEvoked response

Good intubating condition95% -- single twitch

Surgical relaxation withoutinhalation anesth.

TOF response =1

Surgical relaxation with

inhalation anesth.

TOF response =3

Possible extubationTOF ratio > 0.75

Normal VCTOF ratio = 1


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Laryngoscopy and Intubation

Profound sympathetic responses (hypertension,

tachycardia) can be attenuated by hypnotics,

inhalation anesthetics, opioids, lidocaine, or beta

blockers


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ETT Size

Premature: 2.5-3

Full term: 3

6 M -1 y:3.5

2 Y: 4.5

Over 2y: 4+(age/4)4 +(6/4) 5.5

Length (at mouth cm): 10+(age/4)10 +(6/4)

11.5cm


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Positioning

Movement of supine anesthetized patient into another

position may cause hypotension due to lack of intact

compensatory hemodynamic reflexes. Patients

head and limbs should be protected and padded.Hyperextension or over-rotation of the neck and

limbs must be avoided.


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Maintenance

Depth of anesthesia (surgical anesthesia)

+Muscle relaxation

Signs of inadequate depth of anesthesia:

Somatic responses (movement, coughing, changes of

respiratory pattern)

Autonomic responses (tachycardia, hypertension,

mydriasis, sweating, tearing)


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Stages of General Anesthesia

From induction to loss of

consciousness, pain perception is

maintained

Stage I

Amnesia

Exaggerated responses to noxious

stimulus, dilated pupils, divergentgaze, irregular breathing

Stage II

Delirium

Central gaze, constricted pupils,

regular respiration, no somatic or

autonomic responses

Stage III

Surgical anesthesia

Depressed respiration, dilated

fixed pupils, marked hypotension

Stage IV

Overdosage


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Maintenance

If spontaneous breathing is needed, minimal opioids

with nitrous oxide and inhalation anesthetic

If muscle relaxation is needed, nitrous oxide-opioid-

relaxant with minimal inhalation anesthetic andcontrolled ventilation (Balanced anesthesia)

TIVA: Continuous infusion of propofol-opioid +

muscle relaxant (nothing through inhalation)


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Inhalation Anesthetics

Blood-gas partition coefficient is inversely related to

the rate of induction

MAC: minimal alveolar concentration that prevent

movement in response to a skin incision in 50% ofpatients


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Inhalation Anesthetics

MACBlood/gas PC

1040.47Nitrous oxide

0.742.3Halothane

1.151.4Isoflurane

2.050.69Sevoflurane

6.00.42Desflurane


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Ventilation

Spontaneous/assisted:

All inhalation anesthetics depress respiration and

moderately increase PaCO2

Can be affected by positioning, peritonealinsufflation, open chest, surgical packing and opioids


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Ventilation

Controlled Ventilation:

Initial setting with TV=10-15 ml/kg, RR=10-12/min,notice the PIP, If>30, decrease TV and increase RR

A sudden drop in PIP circuit leakA sudden increase in PIP kink, endo-bronchialintubation, peritoneal insufflation


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IV Fluids

Maintenance: first 10kg 4ml/kg/h

Second 10 kg 2ml/kg/h

After 20 kg 1 ml/kg/h

Third-space loss: Tissue edema and evaporation,

varies from 5-10 ml/kg/h

Blood loss: Replaced in 1:3 with isotonic crystalloid,

or 1:1 with blood


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IV Fluids (60 kg fit adult fasting for 6h)

1st h 2nd h 3rd h

Fasting 300 150 150

Maintenance

(100ml/h)

100 100 100

3rd space 5x60=300 5x60=300 5x60=300

Blood loss -- -- --

Total 700 550 550


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Estimated Allowable Blood Loss

70 kg, Hct 35

EABL =EBV X (Hctstart

-Hctallowable

)Hctstart

EABL = 4900 X (3527)= 980ml

35


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Estimating Volume of Blood to be

Transfused

70 kg, with present Hct of 23

Volume=EBV X (Hctdesired- Hctpresent)

Hct transfused blood

Volume=4900 X (30-23) =490ml

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Emergence from GA

Goals: awake, responsive with full muscle strength

so he can maintain patent airway, cannot aspirate

and can be assessed neurologically

Technique: withdraw anesthetics near the end ofsurgery, reverse muscle relaxation with neostigmine

(0.03-0.06 mg/kg) and atropine (0.2-0.4 mg/kg)


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Emergence from GA

Environment: Warm and calm

Positioning: Supine, tonsillectomy if full stomach

Mask ventilation: 100% oxygen, avoid stimulation ofthe airway during stage II


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Emergence from GA

Extubation:

1-Awake (desirable) with fully recovered protective

reflexes, follow simple verbal commands, breathe

spontaneously with good oxygenation and ventilation(lidocaine 1mg/kg IV)

2- Deep extubation (during stage III) reduce risk of

laryngospasm and bronchospasm (in asthmatic)

avoid coughing ( eye surgery, hernia repair)


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Emergence from GA

Agitation: due to hypoxia, hypercarbia, airway

obstruction, full bladder, pain or sevoflurane and

desflurane anesthesia. Treated by treating the

cause, fentanyl 25g IV or morphine 2mg IVincrements

Delayed awakening: Continue ventilatory support

and airway protection and reverse the etiology


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Transport

Stable patient can be transferred without oxygen or

monitor to PACU

Unstable patient should be transferred with oxygen,

monitors, tools for re-intubation to PACU or ICU Anesthetist should give concise but thorough

summary to PACU or ICU staff


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Acute postoperative pain management

Optimal pain control is an integral component of

accelerated recovery

Although opioids are the most effective, acute

postoperative pain management is now based onmultimodal analgesiaand opioid sparing


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Psychological Preparation

Assessing Pain (0-10 Verbal Analogue Scale is now

the fifth vital sign to be recorded in the record)

Preemptive Analgesia (peripheral injury centralsensitization increase pain sensitivity


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Treatment Options:

1- NSADs:

Oral alonemild to moderate pain, begin preop.,

gastric irritation, coagulopathy, mask fever

Oral wi th op ioidsreduce opioid intake

Parentralkeorolac 30 mg then 15-30 mg/6h,

expensive, can replace opioids

Paracetamol (Perfalgan), 1 gm/6h


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2-Opioids:

PO (chronic pain)

IM ( morphine 0.1mg/kg, pethidine 1mg/kg) painful,

unreliable

IV-bolus (morphine 2mg every 5 min, max 10-15mg)

IVI ( morphine 10- 20 g/kg/h)

Monito r the resp iratory rate


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3- PCA:

Provide analgesic doses immediately based on patient

needs using microcomputer-controlled infusion

pumps which avoids extreme swings in plasmalevels. Special order sheet is needed with detailed

pump setting (demand dose, start dose, delay time,

basal rate) and monitoring (pain level, sedation level,

verbal response)


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4- Epidural Analgesia

Abdominal , vascular & L.L. surgery

Contraindications: patient refusal, coagulopathy,

LMWH, bacteremia, local infection

0.1% Bupivacaine + 1-2 g/ml Fentanyl 5-10 ml/h

Bupivacaine if hypotension or motor block

Fentanyl if pruritis

Complications: Inadequate analgesia, PDPH, epidural

hematoma or abcess


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5- Neuraxial Morphine(preservative-free)

Epidural: 1-4 mg

Intrathecal: 0.1-0.4 mg (Respiratory depression)

6- Intraoperative Neural Blockade(esp. children)


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Local Anesthetics

Ester/Amide

AmineAromatic Ring


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Local Anesthetics

Esters:procaine, chloroprocaine, tetracaine

(metabolised by plasma esterase, allergen)

Amides:lidocaine, bupivacaine, ropivacaine (liver

metabolism)


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Local Anesthetics

Potencylipophilicity

Durationprotein binding

OnsetpKa (pH at which 50% are uncharged ions

diffuse to nerve membrane)


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Local Anesthetics

Sequence of block:

Sympathetic pain & temp. proprioception touch& pressure motor

Additives:Epinephrine 1:200,000prolong duration,systemic toxicity, intensity of block, surgicalbleeding

Sodium bicarbonate: 1 meq:10ml lidocaine,0.1meq:10 ml bupivacaine (avoid ppt)fasten onset


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LA: Systemic Toxicity

CNSLight-headedness, tinnitus, metallic taste, visual

disturbance, cicumoral numbness, muscle twitching,

seizures, loss of consciousness

Treatment: stop injection, oxygen, midazolam 1-2 mg,thiopentone 50-200 mg

CVScontract., conduct., VD collapse (esp.

Bupivacaine)

Treatment: oxygen, volume, vasopressors ACLS


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Local Anesthetics: Spinal Anesthesia

Spinal Needle: 25G pencil point with 19G introducer

Position: Sitting or lateral

Level: L3-4, L4-5

Approach: Midline or paramedian

Drugs: Bupivacaine (Heavy) 0.5% 2-3 mls


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Local Anesthetics: Spinal Anesthesia

Complications:

Hypotension0.5-1L of LR beforethe block, ephedrine

5-10 mg boluses

Bloody tapif does not clear rapidly, withdraw &reinsert

Nausea & vomiting treat hypotension

Apnea (total spinal) support ventilation

PDPH: bed rest, IV fluids, analgesics, caffeine 30mg,

epidural blood patch


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Local Anesthetics: Epidural Anesthesia

Epidural Needle: 17G Tuohyneedle

Position: Sitting or lateral

Level: L3-4, L4-5

Approach: Midline or paramedian

Drugs: Bupivacaine 0.125- 0.25% 15-20 ml

Techniques: Loss of resistance

Hanging drop methodTest dose: 3 ml lidocaine 1% with epinephrine

1:200,000


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Drugs: 1.5 ml/segment

Decrease dose 50% in old age

Decrease dose 30% in pregnancy

Epinephrine increase duration

Opioids (fentanyl 50-100 ) improve the quality

Sodium bicarbonate speeds the onset


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Complications:

Dural puncture 1% Convert to spinal

Reinsert one space above

Inability to thread the epidural catheter (too lateral,

partial bevel insertion)

Insertion into a vein (withdraw)

Catheter break off (inform patient & leave it)


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Local Anesthetics: Combined Spinal-Epidural

Anesthesia

Combine advantages and avoid disadvantages of both

techniques

Rapid onset, solid sacral block, less volume

Longer time, more control on level


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Local Anesthetics: Caudal Epidural

Through the sacrococcygeal membrane

Can reach high level in children: 1 ml/kg Bupivacaine

0.2-0.25% with 1;200,000 Epinephrine reach T6-8

level


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THANK YOU

basic practice of anesthesiology final

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