Anesthesia.pdf

AND RESUSCITATION

ANESTHESIA

Dr. H. Braden

Jameet Bawa, Julie Lajoie, and Maneesh Prabhakar, chapter editors

Geena Joseph, associate editor

THE ABC’s

AIRWAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

REGIONAL ANESTHESIA . . . . . . . . . . . . . . . . . . 19

Definition of Regional Anesthesia

Preparation of Regional Anesthesia

Nerve Fibres

Epidural and Spinal Anesthesia

IV Regional Anesthesia

Peripheral Nerve Blocks

Obstetrical Anesthesia

BREATHING (VENTILATION) . . . . . . . . . . . . . . 5

Manual Ventilation

Mechanical Ventilation

Supplemental Oxygen

LOCAL INFILTRATION, . . . . . . . . . . . . . . . . . . . . 22

HEMATOMA BLOCKS

CIRCULATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fluid Balance

IV Fluid Therapy

IV Fluid Solutions

Blood Products

Transfusion Reactions

Shock

LOCAL ANESTHETICS . . . . . . . . . . . . . . . . . . . . . 22

SPECIAL CONSIDERATIONS . . . . . . . . . . . . . . . 23

Atypical Plasma Cholinesterase

Endocrine Disorders

Malignant Hyperthermia (MH)

Myocardial Infarction (MI)

Respiratory Diseases

ANESTHESIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Preoperative Assessment

ASA Classification

Postoperative Management

Monitoring

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

GENERAL ANESTHETIC AGENTS . . . . . . . . . . . 14

Definition of General Anesthesia

IV Anesthetics (Excluding Opioids)

Narcotics/Opioids

Volatile Inhalational Agents

Muscle Relaxants + Reversing Drugs

MCCQE 2006 Review Notes

Anesthesia – A1

Tracheal Intubation

Extubation

THE ABC’S - AIRWAY

# = fracture

most acute airway problems in an unconscious patient can be managed using simple techniques such as:

• 100% O 2 with the patient in the lateral position (contraindicated in known suspected C-spine #)

• head tilt via extension at the atlanto-occipital joint (contraindicated in known/suspected C-spine #)

• jaw thrust via subluxation of temporomandibular joint (TMJ)

• suctioning (secretions, vomitus, foreign body)

• positioning to prevent aspiration

• inserting oro- or naso-pharyngeal airway

nasopharyngeal airway indicated when an oropharyngeal airway is technically difficult

(e.g. trismus, mouth trauma)

• large adult 8-9 mm, medium adult 7-8 mm, small adult 6-7 mm internal diameter

complications of nasopharyngeal airway include

• tube too long - enters the esophagus

• laryngospasm

• vomiting

• injury to nasal mucosa causing bleeding and aspiration of clots into the trachea

oropharyngeal airway holds tongue away from posterior wall of the pharynx

• large adult 100 mm, medium adult 90 mm, small adult 80 mm

• facilitates suctioning of pharynx

• prevents patient from biting and occluding endotracheal tube (ETT)

complications of oropharyngeal airway include

• tube too long - may press epiglottis vs. larynx and obstruct

• not inserted properly - can push tongue posteriorly

more advanced techniques include

• tracheal intubation (orally or nasally)

• cricothyroidotomy

• tracheostomy

TRACHEAL INTUBATION

definition: the insertion of a tube into the trachea either orally or nasally

Indications for Intubation - the 5 P's

P atency of airway required

• decreased level of consciousness (LOC)

• facial injuries

• epiglottitis

• laryngeal edema, e.g. burns, anaphylaxis

P rotect the lungs from aspiration

• absent protective reflexes, e.g. coma, cardiac arrest

P ositive pressure ventilation

• hypoventilation – many etiologies

• apnea, e.g. during general anesthesia

• during use of muscle relaxants

P ulmonary Toilet (suction of tracheobronchial tree)

• for patients unable to clear secretions

P harmacology also provides route of administration for some drugs

Equipment Required for Intubation

bag and mask apparatus (e.g. Laerdal/Ambu)

• to deliver O 2 and to manually ventilate if necessary

• mask sizes/shapes appropriate for patient facial type, age

pharyngeal airways (nasal and oral types available)

• to open airway before intubation

• oropharyngeal airway prevents patient biting on tube

laryngoscope

• used to visualize vocal cords

• MacIntosh = curved blade (best for adults)

• Magill/Miller = straight blade (best for children)

Trachelight - an option for difficult airways

Fiberoptic scope - for difficult, complicated intubations

Endotracheal tube (ETT): many different types for different indications

• inflatable cuff at tracheal end to provide seal which permits positive pressure ventilation and

prevents aspiration

• no cuff on pediatric ETT (physiological seal at level of cricoid cartilage)

• sizes marked according to internal diameter; proper size for adult ETT based on assessment of patient

• adult female: 7.0 to 8.0 mm

• adult male: 8.0 to 9.0 mm

• child (age in years/4) + 4 or size of child's little finger = approximate ETT size

• if nasotracheal intubation, ETT 1-2 mm smaller and 5-10 cm longer

• should always have ETT smaller than predicted size available in case estimate was inaccurate

malleable stylet should be available; it is inserted in ETT to change angle of tip of ETT, and to

facilitate the tip entering the larynx; removed after ETT passes through cords

lubricant and local anaesthetic are optional

Magill forceps used to manipulate ETT tip during nasotracheal intubation

suction, with pharyngeal rigid suction tip (Yankauer) and tracheal suction catheter

syringe to inflate cuff (10 ml)

A2 – Anesthesia

MCCQE 2006 Review Notes

THE ABC’s - AIRWAY . . . CONT.

stethoscope to verify placement of ETT

detector of expired CO 2 to verify placement

tape to secure ETT and close eyelids

remember “SOLES”

S uction

O xygen

L aryngoscope

ETT

S tylet, S yringe

Preparing for Intubation

failed attempts at intubation can make further attempts difficult due to tissue trauma

plan and prepare (anticipate problems!)

• assess for potential difficulties (see Preoperative Assessment section)

ensure equipment (as above) is available and working e.g. test ETT cuff, and means to deliver

positive pressure ventilation e.g. Ventilator, Laerdal bag, light on laryngoscope

preoxygenation of patient

may need to suction mouth and pharynx first

Proper Positioning for Intubation

FLEXION of lower C-spine and EXTENSION of upper C-spine at atlanto-occipital joint (“sniffing position”)

"sniffing position" provides a straight line of vision from the oral cavity to the glottis

(axes of mouth, pharynx and larynx are aligned)

above CONTRAINDICATED in known/suspected C-spine fracture

once prepared for intubation, the normal sequence of induction can vary

Rapid Sequence Induction

indicated in all situations predisposing the patient to regurgitation/aspiration

• acute abdomen

• bowel obstruction

• emergency operations, trauma

• hiatus hernia with reflux

• obesity

• pregnancy

• recent meal (< 6 hours)

• gastroesophageal reflux disease (GERD)

procedure as follows

• patient breathes 100% O 2 for 3-5 minutes prior to induction of anesthesia (e.g. thiopental)

perform "Sellick's manoeuvre (pressure on cricoid cartilage) to compress esophagus, thereby

preventing gastric reflux and aspiration

• induction agent is quickly followed by muscle relaxant

(e.g. succinylcholine), causing fasciculations then relaxation

• intubate at time determined by clinical judgement - may use end of fasciculations if no defasciculating

neuromuscular junction (NMJ) Blockers have been given

• must use cuffed ETT to prevent gastric content aspiration

• inflate cuff, verify correct placement of ETT, release of cricoid cartilage pressure

• manual ventilation is not performed until the ETT is in place and cuff up

(to prevent gastric distension)

Confirmation of Tracheal Placement of ETT

direct

• visualization of tube placement through cords

• CO 2 in exhaled gas as measured by capnograph

• visualization of ETT in trachea if bronchoscope used

indirect (no one indirect method is sufficient)

• auscultate axilla for equal breath sounds bilaterally (transmitted sounds may be

heard if lung fields are auscultated) and absence of breath sounds over epigastrium

• chest movement and no abdominal distension

• feel the normal compliance of lungs when bagging patient

• condensation of water vapor in tube during exhalation

• refilling of reservoir bag during exhalation

• AP CXR: ETT tip at midpoint of thoracic inlet and carina

esophageal intubation is suspected when

• capnograph shows end tidal CO 2 zero or near zero

• abnormal sounds during assisted ventilation

• impairment of chest excursion

• hypoxia/cyanosis

• presence of gastric contents in ETT

• distention of stomach/epigastrium with ventilation

MCCQE 2006 Review Notes

Anesthesia – A3

THE ABC’s - AIRWAY . . . CONT.

Complications during Laryngoscopy and Intubation

mechanical

• dental damage (i.e. chipped teeth)

• laceration (lips, gums, tongue, pharynx, esophagus)

• laryngeal trauma

• esophageal or endobronchial intubation

systemic

• activation of sympathetic nervous system (hypertension (HTN), tachycardia, dysrhythmias)

since tube touching the cords is stressful

• bronchospasm

Problems with ETT and Cuff

too long - endobronchial intubation

too short - accidental extubation

too large - trauma to surrounding tissues

too narrow - increased airway resistance

too soft - kinks

too hard - tissue damage

prolonged placement - vocal cord granulomas, tracheal stenosis

poor curvature - difficult to intubate

cuff insufficiently inflated - allows leaking and aspiration

cuff excessively inflated - pressure necrosis

Medical Conditions associated with Difficult Intubation

arthritis - decreased neck range of motion (ROM)

(e.g. rheumatoid arthritis (RA) - risk of atlantoaxial subluxation)

obesity - increased risk of upper airway obstruction

pregnancy - increased risk of bleeding due to edematous airway, increased risk of aspiration

due to decreased gastroesophageal sphincter tone

tumours - may obstruct airway or cause extrinsic compression or tracheal deviation

infections (oral)

trauma - increased risk of cervical spine injuries, basilar skull and facial bone fractures,

and intracranial injuries

burns

Down’s Syndrome (DS) - may have atlantoaxial instability and macroglossia

Scleroderma - thickened, tight skin around mouth

Acromegaly - overgrowth and enlargement of the tongue, epiglottis, and vocal cords

Dwarfism - associated with atlantoaxial instability

congenital anomalies

EXTUBATION

performed by trained, experienced personnel because reintubation may be required at any point

laryngospasm more likely in semiconscious patient, therefore must ensure LOC is adequate

general guidelines

• check that neuromuscular function and hemodynamic status is normal

• check that patient is breathing spontaneously with adequate rate and tidal volume

• allow patient to breathe 100% O 2 for 3-5 minutes

• suction secretions from pharynx

• deflate cuff, remove ETT on inspiration (vocal cords abducted)

• ensure patient breathing adequately after extubation

• ensure face mask for O 2 delivery available

• proper positioning of patient during transfer to recovery room, e.g. sniffing position, sidelying

Complications Discovered at Extubation

early

• aspiration

• laryngospasm

• transient vocal cord incompetence

• edema (glottic, subglottic)

• pharyngitis, tracheitis

• damaged neuromuscular pathway (central and peripheral nervous system

and respiratory muscular function), therefore no spontaneous ventilation occurs post extubation

A4 – Anesthesia

MCCQE 2006 Review Notes

late

THE ABC’s - BREATHING (VENTILATION)

MANUAL VENTILATION

can be done in remote areas, simple, inexpensive and can save lives

positive pressure supplied via self-inflating bag (e.g. Laerdal/Ambu+/O 2 )

can ventilate via ETT or facemask - cricoid pressure reduces gastric inflation and the

possibility of regurgitation and aspiration if using facemask

drawbacks include inability to deliver precise tidal volume, the need for trained personnel to “bag”

the patient, operator fatigue, prevents operator from doing other procedures

MECHANICAL VENTILATION

indications for mechanical (controlled) ventilation include

• apnea

• hypoventilation (many causes)

• required hyperventilation (to lower intracranial pressure (ICP))

• intra-operative position limiting respiratory excursion, (e.g. prone, Trendelenburg)

• use of muscle relaxants

• to deliver positive end expiratory pressure (PEEP)

ventilator parameters include (specific to patient/procedure)

• tidal volume (average 10 mL/kg)

• frequency (average 10/minute)

• PEEP

• FIO 2 (fraction of inspired oxygen)

types of mechanical ventilators

1. pressure-cycled ventilators

• delivers inspired gas to the lungs until a preset pressure level is reached

• tidal volume varies depending on the compliance of the lungs and chest wall

2. volume-cycled ventilators

• delivers a preset tidal volume to the patient regardless of pressure required

complications of mechanical ventilation

• decreased CO 2 due to hyperventilation

• disconnection from ventilator or failure of ventilator may result in severe hypoxia and hypercarbia

• decreased blood pressure (BP) due to reduced venous return from increased intrathoracic pressure

• severe alkalemia can develop if chronic hypercarbia is corrected too rapidly

• water retention may occur as antidiuretic hormone (ADH) secretion may be

elevated in patients on ventilators

• pneumonia/bronchitis - nosocomial

• pneumothorax

• gastrointestinal (GI) bleeds due to stress ulcers

• difficulty weaning

SUPPLEMENTAL OXYGEN

Low Flow Systems

acceptable if tidal volume 300-700 mL, RR < 25, steady ventilation pattern

nasal canula - low flow system, inspired O 2 depends on flow rate and tidal volume.

Larger tidal volume, increased RR = lower FIO 2

• for every increase from 1 L/min O 2 , inspired O 2 concentration increases about 4%

• e.g. with normal tidal volume, at 1-6 L/min FIO 2 = 24-44%

facial mask - low flow system, well tolerated, will have some rebreathing at normal tidal volumes.

Minimize by increasing flow rate. Inspired O 2 is diluted by room air

• provides O 2 concentrations of 40-60%

facial mask with oxygen reservoir

• provides O 2 concentrations of > 60%

• 6 L/min = 60%, each increase of 1L/min O 2 increases the inspired conncentration by 10%

High Flow Systems

Venturi mask - high flow system, with mixed O 2 concentrations

• provides many O 2 concentrations, e.g. 24%, 28%, 35%, and 40%

• advantages include a consistent and predictable FIO 2 and the ability to control the humidity of the gas

MCCQE 2006 Review Notes

Anesthesia – A5

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: