PRINCIPLES OF EMERGENCY ANESTHESIADr 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
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
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
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
using the correct anesthetic technique (rapid sequence induction)
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
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
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)
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