Transcript Principles of emergency anesthesia

PRINCIPLES OF EMERGENCY
ANESTHESIA
Dr Masood Entezari
INTRODUCTION
In elective surgery:
- madding correct diagnosis
- identifying and treating medical disorders
- occurring an appropriate period of starvation
 One or more of these conditions are often not met in
emergency work

Further problems :
- dehydration
- electrolyte abnormalities
- hemorrhage
- pain
 The components of general anesthesia are the same in
elective and emergency surgery

Components of general anesthesia
• preoperative
assessment
• Premedication
• Induction
• Maintenance
• Reversal
• Postoperative care
The key to success in emergency anesthesia is a
thorough preoperative assessment
 Particular attention must be given to:
- the search for medical problem
- the occurrence of hypovolemia
- an evaluation of the airway
 There are very few patients whose clinical state is so
life – threatening that they need immediate surgery
( true emergency)

CLASSIFICATION OF OPERATIONS
Emergency immediate operation within one hour of
surgical consultation and considered
life – saving , for example, ruptured aortic
aneurysm repair
Urgent
Operation as soon as possible after
resuscitation , usually within 24 hour of
surgical consultation , for example , intestinal
obstruction
Scheduled
Early operation between 1 and 3 weeks ,
which is not immediately life – saving , for
example, cancer surgery, cardiac surgery
Elective
Operation at the time to suit both the patient
and surgeon
The vast majority of patients benefit from :
- the correction of hypovolemia
- the correction of electrolyte abnormality
- stabilization of medical problem
- waiting for the stomach to empty
 When to operate is the most important decision that
has to be made in emergency work
 Emergency anesthesia ≈ general anesthesia
 But

Classification of anesthetic techniques
• general anesthesia
- intubation of unprotected airway
- spontaneous respiration or controlled ventilation
- use of muscle relaxants
• regional anesthesia
• combination of general and regional anesthesia
• sedation
- intravenous
- inhalational
• combination of sedation and regional anesthesia
Due to the increasing use of regional anesthesia ,
hypovolemia must be corrected pre- operatively
 The sedated patient can talk to the anesthetist at
all time
 If not ,then airway control may be lost with the
risk of aspiration of gastric contents

FULL STOMACH
Starvation for at least 4-6 hours in emergency
surgery
 All emergency patients should be treated as
having a full stomach and so at risk of vomiting ,
regurgitation and aspiration
 Occurring the vomiting at the induction and
emergence from anesthesia
 Entering gastric acid to the lungs and creating a
pneumonitis can be fetal

Silent regurgitation : passive regurgitation of
gastric content up to esophagus
 Regurgitation is particularly likely at induction
of anesthesia when several drugs used
 Regardless of the period of starvation ,in
emergency anesthesia there is always a risk of
aspiration

The trachea must be intubated as rapidly as
possible after induction
 Endoteracheal intubation is performed under
general anesthesia when there is no problem in
preoperative assessment of the airway


Some basic requirements for endoteracheal intubation:
- skilled assistance must be present
- the trolley must tip
- the suction apparatus must work correctly
and
be left on
- a rang of sizes of endoteracheal tubes must
be
available
- spare laryngoscopes must be available
- ancillary intubation aids, gum elastic bougie
and stillettes must be available
Management of endotracheal intubation when
risk of aspiration
•Empty stomach
- from above by nasogastric tube
- from below by drugs ,for example, metoclopramid
•Neutralise remaining stomach contents
- antacids
- use of H₂ blocking drugs to prevent
further
acid secretion
• Stop central nervous system induced vomiting
- avoid opiates
- use of phenothiasines
• Correct anesthetic technique
- rapid sequence induction
- preoxygenation , cricoid pressure , intubation
Neither physical nor pharmacological methods should
be relied on to empty the stomach completely
 In some specialties (obstetrics) an H₂ receptor blocking
drug and 30 ml sodium citrate used orally 15 minutes
before induction of anesthesia
 Opiates delay gastric emptying and increase the
likelihood of vomiting

• The only reliable way
to prevent
regurgitation
using the correct anesthetic technique
(rapid sequence induction)
Rapid
sequence
induction
Preoxygenation
Cricoid
pressure
Intubation
PREOXYGENATION
Breathing 100% oxygen for at least 3 minutes before
induction
 In breathing oxygen only, the lungs denitrogenate rapidly
and after 3 minutes contains only oxygen and carbon
dioxide
 There is a greater reservoir of oxygen in the lunges to
utilize before hypoxia occurs

CRICOID PRESSURE
Identifying the cricoid cartilage on the patient
before induction of anesthesia
 Warning the patient that they might feel
pressure on the neck as they go to sleep
 Pressing down on the cartilage continuously until
telling the anesthetist to the assistant for
stopping

Object: compressing the esophagus between
the cricoid cartilage and vertebral column
 Pressure is usually undertaken by firm but gentle
pressure on the cartilage by the thumb and forefinger
of the assistant
 The cricoid is easily identifiable , forms a complete
tracheal ring , and the trachea is not distorted when it
is compressed
 Giving a neuromuscular blocking drug to facilitate
intubation

INTUBATION
The neuromuscular drug must act rapidly and have a
short duration of action
 The lungs are not ventilated during a rapid sequence
induction ; this will prevent accidental inflation of the
stomach , which will further predispose the patient to
regurgitation and vomiting
 An agent with a short duration of action is valuable
because in cases of failed intubation spontaneous
respiration will return promptly


Suxamethonium has many side effects but remain the
best drug available
Major side effects of suxamethonum
• Muscle aches
• Bradycardia
• Raised intracranial pressure
• Raised intraocular pressure
• Raised intragastric pressure
• Allergic reactions
• Hyperkalemia in burns , paraplegia, some myopathies
• Prolonged action in pseudo cholinesterase deficiency
• Malignant hyperthermia
Releasing the cricoid pressure only when :
- the trachea is intonated
- the cuff inflated
- the correct position of the tube is
confirmed
 The anesthetic is maintained with :
- a volatile agent
- nitrous oxide
- oxygen
- competitive relaxant
- suitable analgesia

The reversal of the relaxant at the end of the procedure is
undertaken with the anticolinesteras (neostigmine)
 Atropine or glycopyrrolat is given concomitantly to stop
bradycardia occurring from the neostigmine
 Major disadvantage of potential hemodynamic instability
of rapid sequence induction: hypertension and tachycardia
following laryngoscopy and intubation
 This is more severe in urgent surgery than elective surgery
because of using opiates at intubation of anesthesia

OTHER
INDICATIONS FOR RAPID
SEQUENCE INDUCTION
Every anesthetic ,not just emergency work , should be
considered from the point of view of unexpected
vomiting or regurgitation
 Some cases are at high risk and rapid sequence
intubation should be considered carefully as an option
in this group

High risk factors for regurgitation
• Oesophageal disease
- pouch
- stricture
• Gastro-oesophageal sphincter abnormalities
- hiatus hernia
- obesity
- drugs
• Gastric emptying delay
- trauma
- pyloric stenosis
- gastric malignancy
- opiates
- patient predisposition , anxiety
- pregnancy
- recent food intake
• Abnormal bowel peristalsis
- peritonitis
- ileus – metabolic or drugs
- bowel obstruction
PULMONARY ASPIRATION
Pulmonary aspiration may be obvious
 Silent pulmonary aspiration is presenting as a
postoperating pulmonary complication
 Treatment :
» suction of airway
» oxygenation of the patient(priority)
» broncoscopy (may be required)

Signs of pulmonary aspiration
• None
• Oxygen destruction
• Coughing
• Tachypnea
• Unexplained tachycardia
• Wheeze
• Hypotension
• Pneomonitis
• Postoperative pulmonary disease
If the patient is not paralyzed , surgery permitting, he
or she should be allowed to wake up
 If paralyzed , intubation and ventilation must occur
and oxygenation maintained
 Bronchospasm may be treated with aminophylline
 Further treatment may include antibiotics , other
bronchodilators and steroids
 Aggressive early management is required

CONCLUSION
Anesthesia for emergency surgery needs careful
preoperative assessment and adequate resuscitation
must be undertaken before surgery