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  • Dr abdollahi

  • Anesthesiologists care for the surgical patient
    in the preoperative, intraoperative, and
    postoperative period . Important patient care
    decisions reflect the preoperative evaluation,
    creating the anesthesia plan, preparing the
    operating room, and managing the intraoperative

  • The anesthesiologist is ultimately responsible
  • (1) Determining the medical status of the
  • (2) Developing a plan of anesthesia care,
  • (3) Reviewing with the patient or a responsible
    adult the proposed care plan.
  • After review of the patient's medical history
    and laboratory and other test results from the
    patient's medical record, confirmation by a
    focused physical examination, and review of the
    patient's fasting status, the anesthesiologist
    chooses the anesthetic technique.

  • The anesthesiologist selects as the anesthetic
  • (1) General anesthetic
  • (2) Regional anesthetic
  • (3) Peripheral nerve block
  • (4) Monitored anesthetic care (MAC).
  • The choice of anesthetic technique (or
    combination of techniques) is determined by
    surgical and patient considerations frequently,
    more than one anesthetic technique is appropriate.

Considerations That Influence the Choice of
Anesthetic Technique
  • Intraoperative and postoperative monitoring
    considerations may influence the choice of
    anesthetic technique. For example, if rapid
  • neurologic evaluation is needed, a general
    anesthetic with
  • short-acting drugs or a regional anesthetic may
    be selected.

  • Conversely, if intraoperative transesophageal
    echocardiography is required, a general
    endotracheal anesthetic will probably be
    preferred. There are few circumstances in which a
    specific anesthetic technique has been
    demonstrated to be safer or more efficacious than
    another technique,but anesthesiologists may
    perform better with techniques with which they
    are more experienced.

  • Unpleasant side effects associated with
    anesthesia may influence the choice of anesthetic
    technique. Because the relative safety of
    different anesthetic techniques is often viewed
    as similar, patient satisfaction may become the
    principal determinant of the anesthetic technique

  • Assuming equivalent safety, both the
    anesthesiologist and patient are likely to place
    the greatest importance on avoidance of pain,
    followed by vomiting, nausea, and to a lesser
    extent, urinary retention, myalgia, and pruritus.
    For some patients, avoiding an awake technique is
    the predominant concern, perhaps because of
    anxiety. For these patients, even in the absence
    of pain, the sights, sounds, and smells of the
    operating or procedure room are an experience to
    be avoided.

  • An ideal anesthetic technique would incorporate
  • patient safety and satisfaction, provide
    excellent operating
  • conditions for the surgeon, allow rapid recovery,
  • avoid postoperative side effects. In addition, it
    would be
  • low in cost, allow early transfer or discharge
    from the
  • postanesthesia care unit , optimize postoperative
  • pain control , and permit optimal operating room
    efficiency, including turnover times.

Physical Status Classification of the American
Society of Anesthesiologists
General Anesthetic
  • General anesthesia may be initiated by the
  • of intravenous drugs or inhalation of a volatile
  • with or without nitrous oxide.

  • Induction of general anesthesia (loss of
    consciousness) in adult patients is most often
    accomplished by the intravenous administration of
    drugs (propofol, thiopental, or etomidate) that
    produce rapid onset of unconsciousness. After
    loss of consciousness, the anesthesiologist may
    place a laryngeal mask airway (LMA) and or
    administer a neuromuscular blocking drug
    intravenously to produce skeletal muscle
    relaxation for facilitation of direct

  • The intravenous injection of a drug to produce
    unconsciousness followed immediately by a
    neuromuscular blocking drug that produces a rapid
    onset of skeletal muscle paralysis
    (succinylcholine, rocuronium, mivacurium) is
    referred to as "rapid-sequence" induction of
    anesthesia. Frequently, the patient is breathing
    oxygen (3 to 5 Umin) via a facemask
    (preoxygenation) before rapid-sequence induction
    of anesthesia.

  • Preoxygenation is intended to replace nitrogen
    (denitrogenation) in the patient's functional
    residual capacity (about 2500 mL of
  • 21 oxygen) with oxygen. This practice should
  • the margin of safety during periods of upper
    airway obstruction or apnea (drug induced during
    direct laryngoscopy for tracheal intubation) that
    may accompany induction of anesthesia.

  • In healthy awake patients, the increase in
    arterial hemoglobin oxygen saturation achieved
    with eight vital capacity breaths of 100 oxygen
    over a period of 60 seconds is similar to that
    achieved by breathing 100 oxygen for 3 minutes
    at normal tidal volumes. Four vital capacity
    breaths over a 30-second
  • period also increases arterial oxygenation, but
    the time
  • until hemoglobin desaturation is shorter than in
  • breathing oxygen for 3 minutes or taking eight
    deep breaths.

Rapid-Sequence Induction of Anesthesia
  • A typical rapid-sequence induction of anesthesia
  • preoxygenation followed by the administration of
    a nonparalyzing (defasciculating) dose of a
  • neuromuscular blocking drug (pancuronium, 1 to 2
    mg IV or its equivalent) and succinylcholine (1
    to 2 mg/kg IV).
  • Cricoid pressure may be applied by an assistant
    just before
  • the onset of drug-induced unconsciousness and
    loss of
  • protective upper airway reflexes.

  • Rocuronium, though not as rapid in onset as
    succinylcholine, is used as an alternative when a
    depolarizing muscle relaxant is contraindicated.
  • It is common practice to administer an opioid
    (fentanyl, 1 to 2 µg/kg IV or its equivalent) 1
    to 3 minutes before administration of the
    induction drug.

  • The opioid is intended to blunt the subsequent
    presser and heart rate responses to direct
    laryngoscopy and tracheal intubation and also to
    initiate preemptive analgesia. Remifentanil and
    alfentanil undergo more rapid blood-brain
    equilibration than fentanyl does and thus may be
    more reliable in blunting the sympathetic nervous
    system responses evoked
  • by direct laryngoscopy and tracheal intubation.

  • with the onset of unconsciousness, the patient's
    head is positioned to optimize patency of the
    upper airway, and positive-pressure inflation of
    the patient's lungs with oxygen is instituted.
    Direct laryngoscopy for tracheal intubation is
    initiated only after the onset of skeletal muscle
    paralysis (often verified by a peripheral nerve
    stimulator), which is typically 45 to 90 seconds
    after the administration of succinylcholine.

  • Facilitation of tracheal intubation by skeletal
    muscle paralysis with pancuronium, vecuronium,
    atracurium, cisatracurium, or mivacurium is
    possible if it is acceptable to wait 3 to 5
    minutes for their peak pharmacologic effect.

  • Monitoring of arterial hemoglobin oxygen
    saturation with a pulse oximeter provides early
    warning should arterial oxygen desaturation occur
    during the period of apnea required for tracheal
    intubation. It is mandatory that proper placement
    of the tube in the trachea be confirmed after
    direct laryngoscopy .

Evidence of a Patent Upper Airway after
Induction of Anesthesia
  • After tracheal intubation, it may be prudent to
    insert a gastric tube through the mouth to
    decompress the stomach and remove
  • any easily accessible fluid. This orogastric tube
    should be
  • removed at the conclusion of anesthesia. Then
  • suction is needed postoperatively, nornlally the
    tube should
  • be inserted through the nares rather than the

  • An alternative to rapid-sequence induction of
    anesthesia is the inhalation of sevoflurane (non
    pungent) with or without nitrous oxide.s Prior
    intravenous administration of a "sleep dose" of
    an induction drug may be used if an intravenous
    catheter is in place.

  • Desflurane produces a rapid onset of effect but
    is not selected for inhalation induction because
    of its airway irritant effects. Inhalation or
    "mask induction" of anesthesia is most often
    selected for pediatric patients when prior
    insertion of a venous catheter is not practical.

  • Sevoflurane may also be useful when difficult
    airway management is anticipated because of the
    absence of salivation and preservation of
    spontaneous breathing. The traditional
  • "awake look" in a patient with a suspected
    difficult airway,
  • which included titration of intravenous drugs
    until the patient tolerated direct laryngoscopy,
    has been modified to include spontaneous
    ventilation of high concentrations of sevoflurane
    until laryngoscopic evaluation is possible.

Characteristics of Inhalation Induction
with Sevoflurane
  • Loss of consciousness typically occurs within
    about 1 minute
  • when breathing 8 sevoflurane. LMA placement can
    usually be achieved within 2 minutes after
    administering 7 sevoflurane by facemask. The
    addition of nitrous oxide to the inspired gas
    mixture does not add significantly to the
    induction sequence. Prior administration of
    benzodiazepines may facilitate inhalation
    induction, whereas opioids may complicate this
    technique by increasing the likelihood of apnea.

  • A technique for induction of anesthesia with
    sevoflurane includes priming the circuit
    (emptying the reservoir bag and opening the
    adjustable pressure-limiting "pop-off" valve),
    dialing the vaporizer setting to 8 while using a
    fresh gas flow of 8 l/min, and maintaining this
    flow for 60 seconds before applying the facemask
    to the patient.
  • At this point a single breath from end-expiratory
    volume to maximum inspiration followed by deep
    breathing typically produces loss of
    consciousness in 1 minute.

  • After inhalation induction of anesthesia, a
    depolarizing or nondepolarizing neuromuscular
    blocking drug is administered intravenously to
    provide the skeletal muscle relaxation needed to
    facilitate direct laryngoscopy for tracheal
    intubation. If the anesthesiologist decides to
    not place a tube in the trachea, anesthesia is
    maintained by inhalation through a face mask or

  • The objectives during maintenance of general
    anesthesia are amnesia, analgesia, skeletal
    muscle relaxation, and control of the sympathetic
    nervous system responses evoked by noxious
    stimulation. These objectives are achieved most
    often by the use of a combination of drugs that
    may include inhaled or injected drugs (or both),
    with or without neuromuscular blocking drugs.
    Each drug selected should be administered on the
    basis of a specific goal that is relevant to that
    drug's known pharmacologic effects at therapeutic

  • For example, it is not logical to administer high
    concentrations of volatile anesthetics to produce
    skeletal muscle relaxation when neuromuscular
    blocking drugs are specific for achieving this
  • Likewise, it is not acceptable to obscure
    skeletal muscle
  • movement by administering excessive amounts of
    neuromuscular blocking drugs because of
    insufficient doses of
  • anesthetics.

  • Indeed, a volatile drug is seldom administered as
    the sole anesthetic but is more often
    administered in combination with nitrous oxide.
    Substitution of nitrous oxide for a portion of
    the dose of the volatile anesthetic allows a
    decrease in the delivered concentration of the
    volatile drug, resulting in less cardiac
    depression despite the same total dose of
    anesthetic drugs.

  • Volatile anesthetics may provide inadequate
    analgesic effects, may be associated with
    postoperative hepatic dysfunction, and introduce
    the possibility of carbon monoxide production
    should they be exposed to desiccated carbon
    dioxide absorbents that
  • contain strong bases.

  • In certain instances it is acceptable to
    administer neuromuscular blocking drugs to ensure
    lack of patient movement and permit a decrease in
    the delivered concentration of volatile
    anesthetics. This use of neuromuscular blocking
    drugs, however, must not be interpreted as an
    endorsement for the administration of an
    inadequate dose of anesthetic that is obscured by
    skeletal muscle paralysis.
  • In this regard, intraoperative awareness is a
    recognized risk of minimal concentrations of
    anesthetic drugs ("light anesthesia"), especially
    when patient movements are obscured by
    drug-induced skeletal muscle paralysis.

  • Opioids that generally do not depress the
    cardiovascular system are combined most often
    with nitrous oxide . In patients with normal left
    ventricular function, however, the lack of
    opioid-induced cardiovascular depression and the
    absence of attenuation of sympathetic nervous
    system reflexes may be manifested as systemic
    hypertension. when this occurs, the addition of
    low concentrations of a volatile anesthetic to
  • delivered gases is often effective in returning
    the increased
  • systemic blood pressure to an acceptable level.

  • Neuromuscular blocking drugs are often necessary,
    even in the absence of the need for skeletal
    muscle relaxation, because adequate doses of
    opioids administered in the presence of nitrous
    oxide are unlikely to prevent patient movement in
    response to painful stimulation. Another
    disadvantage of injected drugs versus inhaled
    anesthetics is an inability to accurately titrate
    and maintain a therapeutic concentration of the
    injected drug. This disadvantage can be offset to
    some extent by continuous intravenous infusion of
    the injected anesthetic at a rate previously
    determined in other patients to be associated
    with therapeutic concentrations in blood.

  • Brain function monitoring (bispectral index,
    entropy, auditory evoked potentials) may be
    helpful in titrating the dose of inhaled or
    injected anesthetic drugs to produce the desired
    degree of central nervous system depression .

Regional Anesthetic
  • A neuraxial regional anesthetic (spinal,
    epidural, caudal) is selected when maintenance of
    consciousness during surgery is desirable. Spinal
    anesthesia and epidural anesthesia each have
    advantages and disadvantages that may make one or
    the other technique better suited to a specific
    patient or surgical procedure.

  • Spinal anesthesia
  • (I) takes less time to perform,
  • (2) produces a more rapid onset of
    better-quality sensory and motor anesthesia,
  • (3) is associated with less pain during surgery.

  • The principal advantages of epidural anesthesia
  • (I) a lower risk for post-dural puncture
  • (2) less systemic hypotension if epinephrine is
    not added to the local anesthetic solution,
  • (3) the ability to prolong or extend the
    anesthesia through an indwelling epidural
  • (4) the option of using the epidural catheter to
    provide postoperative analgesia.
  • Skeletal muscle relaxation and contraction of the
    gastrointestinal tract are also produced by a
    regional anesthetic.

  • Patients may have preconceived and erroneous
    conceptions about regional anesthesia that will
    require the anesthesiologist to reassure them
    regarding the safety of this technique. The only
    absolute contraindication to spinal or epidural
    anesthesia is patient refusal. Certain
    preexisting conditions increase the relative risk
    of these techniques, and the anesthesiologist
    must balance the perceived benefits of this
    technique before proceeding.

Conditions That May Increase the Risk Associated
with Spinal or Epidural Anesthesia
  • Disadvantages of this anesthetic technique
    include the occasional failure to produce sensory
    levels of anesthesia that are adequate for the
    surgical stimulus and the decrease in systemic
    blood pressure that may accompany the peripheral
    sympathetic nervous system blockade produced by
    the regional anesthetic, particularly in the
    presence of hypovolemia.

  • A regional anesthetic technique is most often
    selected for surgery that involves the lower part
    of the abdomen or the lower extremities in which
    the level of sensory anesthesia required is
    associated with minimal sympathetic nervous
    system blockade. This should not,
  • however, imply that a general anesthetic is an
  • technique for similar types of surgery.

Bier block
  • For procedures lasting between 20 and 90 minutes,
    intravenous regional anesthesia (IVRA, or Bier
    block) may be used. IVRA provides reliable
    anesthesia for both the upper and lower
    extremities, although the latter may be more
    problematic because of the size of the lower
    extremities in adults. After the application of a
    tourniquet and exsanguination of the extremity,
    lidocaine (0.5) is commonly administered into a
    catheter previously placed in the involved

  • Double tourniquets (distal cuff inflated over the
    area where local anesthetic has infiltrated with
    time) help ameliorate tourniquet pain.
    Intravenous analgesics such as ketorolac may be
    useful for treatment of patient discomfort during
    IVRA. IVRA is more cost- effective than general
    anesthesia or brachial plexus block
  • for outpatient hand surgery.

Peripheral Nerve Block
  • A peripheral nerve block is most appropriate as a
  • of anesthesia for superficial operations on the
    extremities . Advantages of peripheral nerve
    blocks include maintenance of consciousness and
    the continued presence of protective upper airway
  • The isolated anesthetic effect produced by a
  • nerve block is particularly attractive in
    patients with
  • chronic pulmonary disease, severe cardiac
  • or inadequate renal function.

  • For example, insertion of a vascular shunt in the
    upper extremity for hemodialysis in a patient who
    may have associated pulmonary and cardiac disease
    is often accomplished with anesthesia provided by
    a peripheral nerve block of the brachial plexus.
    Likewise, avoidance of the need for neuromuscular
    blocking drugs in this type of patient
    circumvents the possible prolonged effect
    produced by these drugs in the absence of renal

  • A disadvantage of peripheral nerve block as an
  • technique is the unpredictable attainment of
    adequate sensory and motor anesthesia for
    performance of the surgery. The success rate of a
    peripheral nerve block is often related to the
    frequency with which the anesthesiologist uses
    this anesthetic technique.
  • Patients must be cooperative for a peripheral
    nerve block to be effective. For example, acutely
    intoxicated and agitated patients are not ideal
    candidates for a peripheral nerve block

Monitored Anesthesia Care
  • MAC is defined by the ASA as a procedure in which
    an anesthesiologist is requested or required to
    provide anesthetic services the anesthesiologist
    is responsible for preoperative evaluation, care
    during the procedure, and management after the
    procedure. This responsibility includes
  • (1) diagnosis and treatment of clinical problems
    during the procedure
  • (2) support of vital functions
  • (3) administration of sedatives, analgesics,
    hypnotics, anesthetic
  • drugs, or other medications as necessary for
    patient safety
  • (4) psychological support and physical comfort
  • (5) provision of other services as needed to
    complete the
  • procedure safely.

  • The care of a patient undergoing MAC is held to
    the same standard as any other anesthetic
    technique, given that the level of sedation may
    progress rapidly, go beyond consciousness, and
    lead to an "unplanned general anesthetic
    (specifically defined by the ASA as any instance
    in which the patient loses consciousness as
    defined by the ability to respond
    purposefully).when this occurs, extra care may be
    needed in monitoring to prevent airway mishaps
    such as upper airway obstruction and arterial
    hypoxemia, as reflected by the pulse oximeter

  • while caring for a patient under MAC, it is
    important to consider the total dose of local
    anesthetic administered by the surgeon and the
    risk for local anesthetic toxicity, with an eye
    to potentially toxic doses . In addition to
    monitoring the patient, the anesthesiologist
    makes the decision to administer supplemental
    oxygen (may not be necessary if pulse oximeter
    readings are
  • acceptable while breathing room air), typically
    by nasal cannula. In addition to oxygen, the
    anesthesiologist may administer drugs
    intravenously to provide anxiolysis (midazolam),
    sedation (propofol), and analgesia (remifentanil,
    ketorolac, ketamine).

  • MAC may facilitate avoidance of side effects
    (sympatholysis, respiratory depression, delayed
    emergence) and can be particularly cost-effective
    in comparison to general or regional anesthetics
    in the ambulatory care setting.

  • Preparation for anesthesia after the preoperative
  • has been administered and the patient is
    transported to the operating room is similar
    regardless of the anesthetic
  • technique that has been selected . On arrival in
    the operating room, the patient is identified and
    the planned surgery reconfirmed.

Routine Preparation before Induction
of Anesthesia Independent of the Anesthetic
Technique Selecte
  • Anesthesia machine
  • Attach an anesthetic breathing system with a
    properly sized facemask
  • Occlude the patient end of the anesthetic
    breathing system and fill with oxygen from the
    anesthesia machine ("flush valve") (applying
    manual pressure to the distended reservoir bag
    checks for leaks in the anesthetic breathing
    system and confirms the ability to provide
    positive-pressure ventilation of the patient's
    lungs with oxygen)
  • Check the anesthetic breathing system valves
  • Calibrate the oxygen analyzer with air and oxygen
    and set alarm limits
  • Check the carbon dioxide absorbent for color
  • Check the liquid level of vaporizers
  • Confirm proper function of the mechanical

  • Confirm the availability and function of wall
  • Check the final position of all flowmeter,
    vaporizer, and monitor (visual and audible alarm)
  • Monitors
  • Blood pressure
  • Pulse oximetry
  • Electrocardiography
  • Capnography

  • Drugs
  • Local anesthetic (lidocaine)
  • Induction drug (propofol, thiopental, etomidate)
  • Opioid (fentanyl, sufentanil, alfentanil,
  • Benzodiazepine (midazolam, diazepam)
  • Anticholinergic (atropine, glycopyrrolate)
  • Sympathomimetic (ephedrine, phenylephrine)
  • Succinylcholine
  • Nondepolarizing neuromuscular blocking drug
    (mivacurium, rocuronium, atracurium, vecuronium,
    cisatracurium, pancuronium)
  • Anticholinesterase (neostigmine, edrophonium)

  • Opioid antagonist
  • Benzodiazepine antagonist
  • Catecholamine to treat an allergic reaction
  • Equipment
  • Intravenous solution and connecting tubing
  • Catheter for vascular cannulation
  • Suction catheter
  • Oral and/or nasal airway
  • Laryngeal mask airway
  • Tracheal tube
  • Nasogastric tube
  • Temperature probe

  • The patient's medical record, including the
    nurse's notes, is consulted by the
    anesthesiologist to learn of any unexpected
    changes in the patient's medical condition, vital
    signs, or body temperature and to determine that
    the preoperative medication
  • and, if indicated, prophylactic antibiotics have
  • administered. Likewise, any laboratory data that
    have become available since the
    anesthesiologist's previous visit should be

  • Initial preparation for anesthesia, regardless of
    the technique of anesthesia selected, usually
    begins with insertion of a catheter in a
    peripheral vein and application of a blood
    pressure cuff. This initial preparation may be
    accomplished in a holding area or in the
    operating room. The use of separate rooms
    (induction rooms) distinct from the operating
    room for induction of anesthesia is not
    recommended by some because of the questionable
    safety of routinely moving anesthetized patients
  • with the necessary attached equipment from one
    area to
  • another.

  • An exception to this recommendation may be the
    performance of peripheral nerve blocks or
    institution of epidural anesthesia in a holding
    area so that the block is in place when the
    operating room becomes available.
  • Likewise, an epidural catheter for postoperative
    pain management may be placed in the holding area
    before transport of the patient to the operating
    room and induction of general anesthesia.

  • Monitors such as the pulse oximeter,
    electrocardiogram, and peripheral nerve
    stimulator are also applied while the patient is
    still awake.
  • Immediately before induction of anesthesia,
    baseline vital
  • signs (systemic blood pressure, heart rate,
    cardiac rhythm, arterial hemoglobin oxygen
    saturation, breathing rate)
  • and the corresponding time are recorded.

  • The desire for cost containment often leads to
    recommendations that low-cost drugs (antiemetics,
  • induction drugs, volatile anesthetics,
    neuromuscular blocking drugs) be used in
    preference to newer, but more expensive drugs
    with desirable pharmacologic profiles. The
    ultimate goal must be to obtain the best results
    (low toxicity, rapid awakening, absence of nausea
    and vomiting) at the most practical cost. A
    useful method to decrease the cost of volatile
    anesthetics is the use of low fresh gas flow (2
    L/min) during maintenance of anesthesia.