During pre-operative planning, efficient anesthetic regime was chosen on nature of surgery or diagnostic procedure as well as on patient's physiologic, pathologic & pharmacologic state

Status of organ systems are always taken into consideration (1) CVS (2) Respiratory (3) Liver & Kidney (4) Nervous (5) Other [pregnancy]

If a hypotensive episode develops during anesthesia, the reduced perfusion pressure may be followed by ischemic injury to tissues

Inhalation anesthetics such as halothane may sensitize the heart to catecholamines -> increase risk of arrhythmias

Anesthetic agents suppress CV function to varying degrees (Eg: propofol, iv agent caused markedly fall in BP)

Inhaled anesthetics depress the respiratory system & acts as bronchodilators while IV anesthetics & opioids may suppress respiration

This effect on respiratory function may affect the ability for adequate ventilation & oxygen supply during surgery & post-operatively

Patients with asthma & ventilation or perfusion abnormalities -> may complicate control of inhalation anesthetics

Release of fluoride, bromide & other metabolic products of halogenated hydrocarbons can affect these organs esp the metabolites that accumulate over repeated administration over short period of time

Both organs influence the long-term distribution & clearance & may also become the target organs for toxic effects, thus their status are important to be considered

Neurologic disorders (eg: epilepsy, myasthenia gravis, neuromuscular disease & compromised cerebral circulation) or patient history of malignant hyperthermia influences the selection of anesthetics

BZDs should not be used routinely during labor, because of resultant temporary hypotonia & altered thermoregulation in newborn

Special precaution for use in pregnant women: Anesthetics may affect organogenesis in fetus during early pregnancy; Transient use of nitrous oxide -> aplastic anemia in the unborn child; Oral clefts among child of women who received BZD during early pregnancy (2-fold increased risk of oral cleft)

Adults normally induced with IV anesthetic (eg: propofol produces unconsciousness within 30-40 seconds);;; children w/o IV access, inhalatio induction is used with non-pungent agents (eg: halothane or sevoflurane)

Additional inhalation and/or IV drugs of selected combination may be given to produce the desired depth of surgical anesthesia (Stage III)

Induction depends on how fast the effective concentrations of anesthetic drugs reach brain

Period of time from onset of administration to the development of surgical anesthesia

This often includes co-administration of IV skeletal muscle relaxant to facilitate intubation & muscle relaxation (eg: rocuronium, vecuronium or succinylcholine)

Patient's vital signs & response to various stimuli are monitored continuously throughout surgery by carefully balancing amount of drug inhaled and/or infused with the depth of anesthesia

During this period, anesthesia is commonly maintained by administration of volatile anesthetics - for good control over the depth of anesthesia

Opioids (eg: fentanyl) often used for pain relief along with inhalation agents, because the latter are not good analgesics

Propofol, Fospropofol, Barbiturates (thiopental, mathohexital), BZD (midzolam, diazepam, lorazepam), Opioids (fentanil, sufentanil, remifentanil), Etomidate, Ketamine, Dexmedetomidine

IV infusions of various drugs may also be incorporated during maintenance phase

Redistribution from site of action underlies recovery (rather than metabolism of the anesthetic)

Post-operatively, the anesthetic mixture is withdrawn & the patient is monitored for the return of consciousness

Recovery depends on how fast the anesthetic diffuses from the brain

Monitoring continues until normal physiologic function is achieved (eg: spontaneous respiration, acceptable BP & HR etc)

A period from discontinuation of administration of anesthesia until consciousness & protective physiologic reflexes are regained

If skeletal muscle relaxants have not been fully metabolized, reversal agents may be used

Patients are also observed for delayed reactions eg: respiratory depression from opioids administered for post-operative pain control

4 stages: Analgesia, Excitement, Surgical Anesthesia, Medullary paralysis

These stages were based on the observation of the inhaled anesthetics

4 sequential stages, based on increasing depth of CNS depression (GUEDEL'S SIGN)

Amnesia & reduced awareness of pain will occur as stage II is approached

Interference with sensory transmission in the spinothalamic tract lead to loss of pain sensation

To shorten or eliminate this stage, a rapid acting agent such as propofol is given iv before inhalation anesthesia is administered

Patient experience delirium & possibly combative behavior

Relaxation of skeletal muscle with eventual loss of spontaneous movement occur in this stage

Continuous careful monitoring is required to prevent undesired progression to stage IV

Gradual loss of muscle tone & reflexes as CNS is further depressed

If no measures taken to maintain circulation & respiration, -> DEATH

Esters linkage - procaine, chloroprocaine, tetracaine, cocaine

Amides linkage - lidocaine, bupivacaine, ropivacaine, mepivacaine, prilocaine

Blocks pain sensation to specific (localized) areas of the body without loss of consciousness