UNDERSTANDING ANESTHESIA

Objectives 1.Identify the different types of anesthesia management 2.Identify common anesthetic agents & their influence on patient subsystems 3.Identify the stages of general anesthesia 4.Discuss appropriate actions in the event of a malignant hyperthermia crisis

Anesthesia 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 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 Effects of general anesthesia: Effects are produced by depression of the CNS & blocking pain stimuli at the level of the cerebral cortex Effects are produced by depression of the CNS & blocking pain stimuli at the level of the cerebral cortex 1.Hypnosis (sleep) 2.Analgesia 3.Amnesia 4.Muscle relaxation

General Anesthesia Anesthesia is generally induced by a combination of drugs: inhalation & intravenous anesthetics inhalation & intravenous anesthetics intravenous narcotics & sedatives intravenous narcotics & sedatives muscle relaxants muscle relaxants

Complications Associated with General Anesthesia Laryngospasm Nausea & Vomiting Damage to teeth during intubation Corneal abrasions Aspiration Malignant hyperthermia

Regional Anesthesia Defined as “a reversible loss of sensation in a specific area of the body” Spinal anesthesia Spinal anesthesia Epidural anesthesia Epidural anesthesia IV Regional Blocks IV Regional Blocks Peripheral Nerve Blocks Peripheral Nerve Blocks

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 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 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 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 Hypotension Inadvertent dural puncture Inadvertent injection of anesthetic into the subarachnoid space

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 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 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 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) 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 Used for short, minor procedures Used in the OR and outlying areas (ER, Endo., etc) (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 Nitrous Oxide- can cause expansion of other gases- use of N 2 0 contraindicated in patients who have had medical gas instilled in their eye(s) during retinal detachment repair surgery

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 N 2 0, can trigger malignant hyperthermia in susceptible patients

Intravenous Induction/Maintenance Agents Propofol (Diprivan)- pain/burning on injection, can cause bizarre dreams Pentothal (Sodium Thiopental)- can cause laryngospasm

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

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 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 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: Electrocardiograph (EKG or ECG) Pulse oximeter Blood pressure monitor Temperature probe Esophageal or precordial stethoscope End-tidal CO 2 Monitor

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

MH 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

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

Signs of MH Rapid rise in body temperature (temperature may exceed 110°F)-may be a late sign Muscle rigidity Hypercarbia (elevated CO 2 ) Acidosis

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 MH Give Dantrolene until signs of MH are controlled If patient is hyperthermic (core temp > 39° C or ° 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 Observe patient in ICU for at least 24 hours Continue Dantrolene for at least 24 hours

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

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: MH-HYPER MH-HYPER( )

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

References Gutierrez, K. (1999) Pharmacotherapeutics: Clinical Decision Making in Nursing Malignant Hyperthermia Association of the United States (2005). Emergency therapy for malignant hyperthermia. Web site: (MHAUS hotline: MH-HYPER) (MHAUS hotline: MH-HYPER) Rothrock, J. (2002) Alexander’s Care of the Patient in Surgery