Understanding anesthesia
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UNDERSTANDING ANESTHESIA. Objectives. Identify the different types of anesthesia management Identify common anesthetic agents & their influence on patient subsystems Identify the stages of general anesthesia Discuss appropriate actions in the event of a malignant hyperthermia crisis .

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Understanding anesthesia



  • Identify the different types of anesthesia management

  • Identify common anesthetic agents & their influence on patient subsystems

  • Identify the stages of general anesthesia

  • Discuss appropriate actions in the event of a malignant hyperthermia crisis


  • The word is derived from the Greek words an, which means “without” and aithesia which means “feeling”

  • The use of medical anesthesia was first reported in 1846

  • The development of anesthesia has made today’s modern surgical techniques possible

Asa physical status classification
ASA Physical Status Classification

  • ASA 1 – normal, healthy patient

  • ASA 2 – patient with mild, well-controlled systemic disease

  • ASA 3 – patient with severe systemic disease that limits activity

  • ASA 4 –patient with severe, life-threatening disease

  • ASA 5 – moribund patient not expected to survive for 24 hours with or without surgery

An “E” is added to the classification

for emergent procedures

General anesthesia
General Anesthesia

  • Effects of general anesthesia:

    • Effects are produced by depression of the CNS & blocking pain stimuli at the level of the cerebral cortex

  • Hypnosis (sleep)

  • Analgesia

  • Amnesia

  • Muscle relaxation

General anesthesia1
General Anesthesia

  • Anesthesia is generally induced by a combination of drugs:

    • inhalation & intravenous anesthetics

    • intravenous narcotics & sedatives

    • muscle relaxants

Complications associated with general anesthesia
Complications Associated with General Anesthesia

  • Laryngospasm

  • Nausea & Vomiting

  • Damage to teeth during intubation

  • Corneal abrasions

  • Aspiration

  • Malignant hyperthermia

Regional anesthesia
Regional Anesthesia

  • Defined as “a reversible loss of sensation in a specific area of the body”

    • Spinal anesthesia

    • Epidural anesthesia

    • IV Regional Blocks

    • Peripheral Nerve Blocks

Spinal anesthesia
Spinal Anesthesia

  • A local anesthetic agent (lidocaine, tetracaine or bupivacaine) is injected into the subarachnoid space

    • Spinal anesthesia is also known as a subarachnoid block

  • Blocks sensory and motor nerves, producing loss of sensation and temporary paralysis

Possible complications of spinal anesthesia
Possible Complications of Spinal Anesthesia

  • Hypotension

  • Post-dural puncture headache (“Spinal headache”) caused by leakage of spinal fluid through the puncture hole in the dura-can be treated by blood patch

  • “High Spinal”- can cause temporary paralysis of respiratory muscles. Patient will need ventilator support until block wears off

Epidural anesthesia
Epidural Anesthesia

  • Local anesthetic agent is injected through an intervertebral space into the epidural space.

  • May be administered as a one-time dose, or as a continuous epidural, with a catheter inserted into the epidural space to administer anesthetic drug

Complications of epidural anesthesia
Complications of Epidural Anesthesia

  • Hypotension

  • Inadvertent dural puncture

  • Inadvertent injection of anesthetic into the subarachnoid space

Iv regional blocks
IV Regional Blocks

  • Also known as a Bier Block

  • Used on surgery of the upper extremities

  • Patient must have an IV inserted in the operative extremity

Iv regional block
IV Regional Block

  • After a pneumatic tourniquet is applied to extremity, Lidocaine is injected through the IV

  • Anesthesia lasts until the tourniquet is deflated at the end of the case

Iv regional blocks1
IV Regional Blocks

  • IMPORTANT- to prevent an overdose of lidocaine it is important not to deflate the tourniquet quickly at the end of the procedure

  • The anesthesia provider will deflate/inflate tourniquet several times before complete deflation of tourniquet cuff

Peripheral nerve blocks
Peripheral Nerve Blocks

  • Injection of local anesthetic around a peripheral nerve

  • Can be used for anesthesia during surgery or for post-op pain relief

  • Examples: ankle block for foot surgery, supraclavicular block for post-op pain control after shoulder surgery

Monitored anesthesia care mac
Monitored Anesthesia Care (MAC)

  • Generally used for short, minor procedures done under local anesthesia

  • Anesthesia provider monitors the patient and may provide supplemental IV sedation if indicated

Conscious sedation
Conscious Sedation

  • Used for short, minor procedures

  • Used in the OR and outlying areas

    • (ER, Endo., etc)

  • Patient is monitored by a nurse and receives sedation sufficient to cause a depressed level of consciousness, but not enough to interfere with patient’s ability to maintain their airway

Inhalation anesthetics
Inhalation Anesthetics

  • Nitrous Oxide- can cause expansion of other gases- use of N20 contraindicated in patients who have had medical gas instilled in their eye(s) during retinal detachment repair surgery

Inhalation anesthetics1
Inhalation Anesthetics

  • Cause cerebrovascular dilation and increased cerebral blood flow

  • Cause systemic vasodilation and decreased blood pressure

  • Post-op N&V

  • All inhalation anesthetics, except N20, can trigger malignant hyperthermia in susceptible patients

Intravenous induction maintenance agents
Intravenous Induction/Maintenance Agents

  • Propofol (Diprivan)- pain/burning on injection, can cause bizarre dreams

  • Pentothal (Sodium Thiopental)- can cause laryngospasm

General anesthesia2
General Anesthesia

  • During induction the room should be as quiet as possible

  • The circulator should be available to assist anesthesia provider during induction & emergence

  • Never move/reposition an intubated patient without coordinating the move with anesthesia first

General anesthesia3
General Anesthesia

  • Laryngospasm may happen in a patient having a procedure with general anesthesia

  • When laryngospasm occurs, it is usually during intubation or emergency

  • Assist anesthesia provider as needed- call for anesthesia back-up if necessary

Difficult airway cart
Difficult Airway Cart

  • Anesthesia maintains a “Difficult Airway Cart” containing equipment & supplies for difficult intubations

  • This cart is stored in one of the anesthesia supply rooms

  • Page anesthesia tech if the cart is needed for your room

Cricoid pressure or sellick maneuver
Cricoid Pressure or Sellick Maneuver

  • Used for patients at risk for aspiration during induction, due to a full stomach or other factors such as a history of reflux

  • Pressure on the cricoid cartilage compresses the esophagus against the cervical vertebrae and prevents reflux

Sellick maneuver
Sellick Maneuver

  • Cricoid pressure is maintained, as directed by anesthesia provider, until the ETT cuff is inflated:

Regional anesthesia1
Regional Anesthesia

  • Circulator may need to assist anesthesia provider with positioning for spinal or epidural anesthesia

  • Patient usually is positioned laterally for placement of regional anesthesia, but may be positioned sitting upright

The awake patient
The Awake Patient

  • Patients undergoing surgery with regional or local anesthesia, even if sedated, may be aware of conversation and activity in room

  • Post sign on door to OR, “Patient is Awake” so that staff entering room will be aware that patient is conscious

When patient is awake
When Patient is Awake

  • Limit any discussion of patient’s medical condition and prognosis

  • Avoid discussion of other patients & limit unnecessary conversation-- a sedated patient can easily misinterpret conversation they overhear

Anesthesia monitoring devices
Anesthesia Monitoring Devices:

  • Electrocardiograph (EKG or ECG)

  • Pulse oximeter

  • Blood pressure monitor

  • Temperature probe

  • Esophageal or precordial stethoscope

  • End-tidalCO2Monitor

Malignant hyperthermia
Malignant Hyperthermia

  • A rare, life-threatening complication of anesthesia

  • Triggered in susceptible patients by certain inhalation anesthetics (halothane, enflurane, isoflurane, sevoflurane, desflurane) and by the muscle relaxant succinycholine

Understanding anesthesia

  • Susceptibility to MH is inherited (autosomal dominant- 50% of children of parents with MH will inherit the gene)

  • MH can be diagnosed by muscle biopsy-this biopsy is indicated for people who have a family history of MH

Understanding anesthesia

  • The mortality rate from MH has been reduced from 80% to around 10% due to improvements in early recognition and treatment

Signs of mh
Signs of MH

  • Rapid rise in body temperature (temperature may exceed 110°F)-may be a late sign

  • Muscle rigidity

  • Hypercarbia (elevated CO2)

  • Acidosis

Treatment of mh
Treatment of MH

  • Call for help!

  • Immediate discontinuation of all inhalation anesthetics

  • Hyperventilate with 100% oxygen

  • End surgery if possible

  • Monitor core temperature

  • Give only “safe” anesthetics: IV narcotics, propofol (Diprivan), nitrous oxide

Treatment of mh1
Treatment of MH

  • Give Dantrolene until signs of MH are controlled

  • If patient is hyperthermic (core temp > 39° C or 102.2 ° F), immediately start aggressively cooling the patient: pack patient in ice, infuse chilled IV fluids, irrigate NG tube & foley catheter with ice water

Mh post acute phase
MH Post Acute Phase

  • Observe patient in ICU for at least 24 hours

  • Continue Dantrolene for at least 24 hours

Dantrolene sodium dantrium
Dantrolene Sodium (Dantrium)

  • Skeletal muscle relaxant

  • Dantrolene is stored in the OR in the Malignant Hyperthermia Box

    be sure that you know where this box is located!

Dantrolene reconstitution
Dantrolene Reconstitution

  • Use only preservative-free sterile water

  • Add 60cc sterile water to each 20mg vial of dantrolene-shake vial until solution is clear. Dantrolene is very difficult to mix up

  • Initial dosage 2.5 mg/kg IV push - administer drug until symptoms of MH subside or until maximum dosage of 10mg/kg is reached

    • (in some cases more than 10mg/kg is needed to reverse MH)

For more information
For More Information…

  • The Malignant Hyperthermia Association of the United States (MHAUS) has a 24-hr hotline to assist medical professionals in dealing with a malignant hyperthermia crisis:




  • For non-urgent needs, information about MH can be obtained through the MHAUS organization’s web site:



  • Gutierrez, K. (1999) Pharmacotherapeutics: Clinical Decision Making in Nursing

  • Malignant Hyperthermia Association of the United States (2005). Emergency therapy for malignant hyperthermia.

    Web site: http://www.mhaus.org/

    (MHAUS hotline: 1-800-MH-HYPER)

  • Rothrock, J. (2002) Alexander’s Care of the Patient in Surgery