Induction Flashcards
Local Anesthesia
A local anesthetic agent is used in order to prevent the sensation of pain
Will only prevent pain in a small area for a minor procedure to be done
What Makes a Good Local Anesthetic
Does not irritate the tissue
Does not cause permanent damage
Is not toxic to any tissue after it is absorbed into the blood
Has a predictable duration and action
Common Local Anesthetics
- Bupivacaine (Marcaine)
- Lidocaine (Xylocaine)
- A commonly used combination is (0.5%) Lidocaine with epinephrine (reduce bleeding)
How do Local Anestheic works
How these agents work is that they will block the transmission of nerve impulses by acting on the cell membrane
They will generate an action potential but then block any further action
Pain will not be felt during this duration of action
Where are local anesthetic commonly used
Commonly used in out-patient wards and clinics
Regional Anesthesia
Regional anesthesia numbs a larger (but still limited) part of the body compared to local anesthesia and does not make the person unconscious. Sometimes medicine is added to help the person relax or fall asleep
Can be a regional nerve block or a regional spinal block
What is an important advantage of regional anesthetsia
Can be very helpful in many surgical procedures, as the patient will remain awake and can maintain their own airway and ventilation
It is important to remember when using these that they require an anti-anxiety agent
Interscalene Block
Type of nerve block
Will numb the shoulder and parts of the upper arm
The injection may be done through ultrasound guidance
Intravenous Regional Block
A peripheral vein is cannulated so that an agent can be introduced
You want this area to have as little blood flow as possible which is why you want to use elevation, tourniquets, etc
Lidocaine or marcaine is then infused into the vein (area) until anesthesia is obtained.
After the procedure, blood is allowed into the area again, agent will be diluted and function will return.
Spinal Block-Definition
At the level of the cauda equina (L2 - S2), an agent (typically tetracaine) can be injected directly into the CSF (sub-arachnoid space) with relatively little risk.
Depending on the amount of agent infused, anesthesia can be obtained much further up the cord.
Spinal Block-Uses
This can be very useful for lower extremity or even abdominal organ surgery.
Procedures up to 3 hours are possible—the clinician could use lidocaine for shorter procedures.
Spinal Block-Common Side Effects
Hypotension.
Severe headache.
Auditory and / or visual disturbances.
PDPH —post ductal puncture headache
Spinal Block-Rare Side Effects
Cardiac arrest.
Focal neurological defects.
Hematomas
Epidural Block
Agents are not needed to be placed directly in the CSF for action to occur.
‘Epidural’ suggests the space next to the dura but outside the actual cord
If enough agent is placed next to the dura, some will diffuse across and give the same action.
Epidural Block Uses
Caesarian section
Lower abdominal surgery
Procedures involving the legs etc.
Epidural Block Side Effects
Hypotension (* Systemic toxicity)
Accidental total spinal anesthesia.
Systemic Toxicity
Systemic toxicity is the result of too much agent.
Systemic Toxicity Path
- Eupohoria
- Apprehension
- Restlessness
- Nausea
- Vomitting
- Tremors
- Convulsions
- Postictal (post convulsion) coma
- Respiratory arrest
- Circulatory collapse
General Anesthesia
General anesthesia affects the entire body and makes the person unconscious.
The unconscious person is completely unaware of what is going on and does not feel pain from the surgery or procedure.
General anesthesia medicines can be injected into a vein or inhaled.
Modern approaches to general anesthesia involve administration of a combination of medications, such as hypnotic drugs, neuromuscular blocking drugs, and analgesic drugs
If general anesthesia is chosen, the anesthesia provider must then determine a plan for airway management, induction of anesthesia, maintenance of anesthesia, and immediate postoperative care
The anesthesia provider must be prepared to convert to general anesthesia if it becomes apparent that appropriate analgesia and immobility cannot be achieved by other means
Induction Definition
Induction is the phase of anesthesia and will begin with the first application of an agent, which is often IV drugs
When Does Induction End
Induction ends when surgical anesthesia is obtained
The procedure will dictate what level of anesthesia is desired.
What is the most popular IV induction agents used
Propofol (Diprivian)
How can the clinician decide if the cannula is in the wrong place
Thiopental given in a very small dose (2 mg)at this point can help the clinician decide if the cannula has gone interstitial or even possibly intra-arterial
What will happen to the patient during induction
The patient will probably undergo profound muscle weakness / relaxation during this phase.
Proper positioning of the patient to avoid injury is mandatory.
What is the most reliable sign of loss of consciousness
The most reliable sign of loss of consciousness is loss of eyelash reflex. (Blinking at the stroking of the eyelashes.)
What Do You Do after you confirm loss of consiousness
Anectine can be used now.
Hyper-oxygenation of the patient will allow sufficient time for intubation.
Tracheal intubation can now be preformed with little chance of laryngospasm.
Nitrous oxide and inhaled anesthetics can now be administered to maintain surgical anesthesia.
Semiconscious
An imprecise term for a state of drowsiness and inaction in which more than normal stimulation may be needed to evoke a response and the response will likely be delayed and incomplete.
Unconscious
An imprecise term for severely impaired awareness of self and surroundings. Synonyms include comatose and unresponsive.
Inhalation Induction
Induction via inhaled agent can be both rapid and pleasant for the patient.
Halothane in 0.5% increments (four to five breaths) via face mask until 3 to 4 % concentration is achieved will induce anesthesia.
Sevoflurane is also popular for inhalation induction because of its pleasant odor and low solubility. Enflurane is a potent resp depressant.
Rapid Sequence Induction
This technique is useful if there is worry that the patient may aspirate gastric contents.
Obesity, pregnancy, an acute abdominal catastrophe, hiatus hernia or Class ‘E’ surgeries are all situations where aspiration must be a concern.
The presence of an assistant is mandatory during rapid sequence induction.
RSI Procedure
- Check and Prepare Equitment
- Pre-oxygenate the patient with 100% O2via face mask for 3 to 5 minutes. (4 to 5 VCs minimum.)
- Position the patients’ head in the ‘sniffing’ (intubation) position
- Administer a carefully calculated dose of thiopental according to the pts size. 3 to 5 mg/Kg
- Immediately give the Anectine; (paralyzing dose 1 mg/Kg)
- Pre-curarization will reduce intra-gastric pressure and therefore reduce the chance of aspiration but it will also reduce the potency of Anectine and delay its action
- Reconfirm positioning of the head and intubate the trachea at the onset of paralysis
- Inflate the cuff of the ET Tube (and confirm position) beforereleasing pressure on the cricoid cartilage.
- Record the position of the ETT and secure it.
Maintenance
Maintenance refers to the phase that starts with the achieving of surgical anesthesia and ends with the beginning of emergence.
The surgical procedure should logically happen during this phase.
One or more agents (usually an inhaled anesthetic) are used to maintain unconsciousness and muscle relaxation (if desired).
Controlled Ventilation Should Be Used During Maintence When
- Profound muscle relaxation is required.
- Balanced anesthesia is being used;
- Nitrous oxide * Volatile agents.
- Narcotics * Muscle Relaxants.
- There is pre-existing cardio-pulmonary disease.
- Hyperventilation is desired.
Emergence Phase
Discontinuing all anesthetic agents and the patient begins to wake up
If no paralysis or muscle relaxants where used then extubation can be allowed even when the patient is still unconscious, as long as protective reflexes have returned but do not do this is they are semi-consious
When minute ventilation is adequate and airway guarding has returned he can be extubated.
Pt should be positioned laterally to prevent aspiration
If the patient was paralyzed or has a large amount of narcotics onboard then they must be reversed
DO NOTallow a a paralyzed patient to regain consciousness. He’ll be very unhappy with you.
Reversing Paralysis
To reverse paralysis you can use neostigmine, edrophonium (Tensilon)
To Reverse Narcotics
To reverse narcotic use Narcan
Emergence Complications
Diffusion Hypoxia; If nitrous oxide was used during the procedure and suddenly discontinued, large amounts of it will diffuse back out of all areas of compartment 3 into the alveoli.
This can dilute the oxygen in the alveoli if inspired oxygen concentration were only 21%.
Use 100% oxygen during emergence to ensure something more than 21% at all times.
Neuroleptic Anesthesia
Innovar; a combination of droperidol (Inapsine ®) (tranquilizer) and Fentanyl (powerful opioid) can produce a dopy, who cares, what-ever attitude in subjects.
There is some amnesia and high analgesia along with a calm lack of movement in subjects.
Nitrous Oxide could be used as an adjunct.
Seldom used.
Dissociative Anesthesia Definition
Ketamine produces a situation where the patient appears to be awake but will have no recollection of events after emergence from the drug.
Dissociative Anesthesia is Composed Of
Catalepsy.
Sedation.
Amnesia.
Analgesia
Low Flow Anesthesia
- Extremely low flows can be used to maintain anesthesia in a controlled situation.
- Oxygen flows of 500mL/min and N2O flows of 700 mL/min are enough to adequately;
- Carry the inhaled agent (eg. Sevoflurane).
- Supply oxygen for metabolism.
- Provide enough flow so that CO2 being scrubbed will be replaced.
- Economy, less pollution, quick titration to effect, little chance of negative side effects and safety can be the result.
What are the most important factors to consider when choosing which anesthetic technique to use
Type of surgical procedure
Coexisting disease
Patient preference
Continuum of Depth of Sedation
Mild Sedation
Anxiolysis
Response (Stimulation Type): Normal (verbal stimuli)
Ability to Maintain Airway: Not Affected
Cardiovascular Funtion: Not Affected
Continuum of Depth of Sedation
Moderate Sedation
Consious Sedation
Response (Stimulation Type): Purposeful (verbal or tactile stimuli)
Ability to Maintain Airway: Airway maintained without intervention, ventilation adequate
Cardiovascular Funtion: Usually maintained
Continuum of Depth of Sedation
General Anesthesia
Response (Stimulation Type): None
Ability to Maintain Airway: Airway intervention often required;ventilation frequently inadequate
Cardiovascular Funtion: May be impaired
Continuum of Depth of Sedation
Deep Sedation
Response (Stimulation Type): Purposeful (repeated or painful stimulus)
Ability to Maintain Airway: Airway maintained without intervention, ventilation may be inadequate
Cardiovascular Funtion: Usually maintained
neuraxial Anesthesia
spinal, epidural, caudal
Clinical Settings Where Regional Anesthesia May Not Be Appropriate
- Preference and experience of patient, anesthesia provider, and surgeon
- The need for an immediate post-operative neurological examination in he anatomic area impacted by the regional anesthetic
- Coagulopathy
- Pre-existing neurological diseases
- Ex. Multiple sclerosis, Neurofibromatosis
- Infected or abnormal skin at the planned cutaneous puncture site
Specific Consideration for Neuraxial Anesthesia
Hypovolemia increase the risk for hypotension
Coagulopathy, including anticoagulants and antiplatlets medication therapy, which will increase risk of epidural hematoma
Increase ICP which may result in cerebral herniation with intentional or inadvertent dural puncture
Clinical Settings Appropriate for General Anesthesia
- A requirement for systemic neuromuscular blockade
- A requirement for establishment of a secure airway
- Due to surgical procedure that may compromise native airway integrity, oxygenation, or ventilation
- Due to the level of consciousness required to provide immobility, analgesia, or anxiolysis
- Patient or procedural characteristics that are not appropriate for monitored anesthesia care
- Uncooperative patient or patient refusal
- Surgical pain not emendable to local or tropical anesthesia
- Patent or procedural characteristic that are not suitable for regional anesthetic
- Preference of patient, anesthesia provider, and/or surgeon
Denitrogenation
Pre oxygenation is also known as denitrogenation is the deliberate replacement of nitrogen in the patient functional residual capacity (FRC) with oxygen
Preoxygenation is done by
8 VC of 100% oxygen over 60 seconds OR
Vt breathing of 100% oxygen for 3 min
Both of the above will replace ~80% of FRC with oxygen
Purpose of Pre-Oxygenation
The purpose of preoxygenation is to provide a margin of safety during periods of apnea or upper airway obstruction that can result from general anesthesia
It can also delay or eliminate the onset of hypoxemia during the time between intravenous induction and beginning of controlled ventilation
What Are Some Reasons an Inhaled Induction May be Used over IV Induction
An inhaled induction is often for pediatric patients or patient who are thought to have a difficult airway as spontaneous respirations will be preserved with an inhaled induction
However, inhaled anesthetics ablate protective airway reflexes and pharyngeal muscular tone, so this method will not be suitable for all patients in whom difficulties with airway management are anticipated.
What is the most common inhaled induction agent
Sevoflurane is the most commonly used anesthetic for inhaled induction of anesthesia because of its low pungency, high potency (permitting delivery of high-inspired oxygen concentration), and rapidity of onset.
Priming
In order to speed up onset priming may be used
This approach to inhaled induction of anesthesia can produce loss of consciousness within 1 minute.
How is Priming Done
Priming involves filling the breathing circuit with 8% sevoflurance through emptying the reservoir bag and opening the adjustable pressure limiting valve, and using a high fresh gas flow (e.g., 8 L/min) for 1 minute before applying the face mask to the patient
Anectine
Succinylcholine Chloride
Skeletal muscle relaxant for intravenous (IV) administration indicated as an adjunct to general anesthesia, to facilitate tracheal intubation, and to provide skeletal muscle relaxation during surgery or mechanical ventilation.
Goal of RSI
minimize the time between onset of unconsciousness and tracheal intubation and reduce the risk of regurgitation by applying cricoid pressure
Airway Management Techniques
Airway management techniques (e.g., direct laryngoscopy, supraglottic airway placement) are implemented after the intravenous or inhaled induction of anesthesia
However, if the anesthesia provider anticipates difficulty with ventilation via a mask or tracheal intubation then tracheal intubation should be initiated prior to induction of anesthesia (i.e., awake intubation)
Nitric Oxide with General Anesthesia
Nitrous Oxide can provide hypnosis and anaglesia, but can not be used as the sole drug for general anesthesia as it lacks the potency of volatile inhaled anesthetics
The minimum alveolar concentration required to prevent movement to surgical stimulation is greater than the concentration that can be delivered at atmospheric pressure, so it cannot be used alone to provide reliable hypnosis
Substitution of nitrous oxide for a portion of the inhaled anesthetic dose can reduce the cardiovascular effects observed with potent inhaled anesthetics while maintaining the same anesthetic depth.
Nitrous oxide also provides analgesia and is rapidly titratable because of its low blood-gas partition coefficient.
Post Operatively What Can Inhaled Anesthetic Increase the Risk Of
Inhaled anesthetics increase the risk for postoperative nausea and vomiting
Patients undergoing outpatient surgery require special attention to the prevention of postoperative and post-discharge nausea and vomiting
This may involve selection of a less emetogenic anesthetic maintenance drug (e.g., propofol) as well as administration of multiple antiemetic drugs
Propofol For Maintenance of Anesthesia
Propofol can reduce incidence of posoperative nausea and vomitting as well as have more favorable emgerence (decreased coughing and laryngospasm)
How Can the Depth of Hypnosis Be Measured
However, depth of hypnosis cannot be reliably measured in the absence of EEG or auditory evoked potential monitoring.
What is the most common use of drugs for maintanance of anesthetsia
Potent inhaled anesthetics represent the mainstay of drugs used to maintain anesthesia in most clinical situations
They are easily titratable, reduce the autonomic response to noxious stimulation, and at clinically relevant doses can often provide sufficient muscle relaxation to facilitate surgical exposure
