Balanced anesthesia

Analgesia - Analgesic adjunct for the maintenance of balanced general anesthesia in patients who are intubated and ventilated. 

For preoperative analgesia, as a supplement to balanced analgesia, to surgical and postsurgical anesthesia and for obstetrical analgesia during labor and delivery. 

Balanced Anesthesia with Inhalational Anesthetic Agents... 

Sufentanil is much more potent than fentanyl and is indicated specihcally for long neurosurgical procedures. In such patients, sufentanil maintains anesthesia over a long period when myocardial and cerebral oxygen balance are critical. 

An anxious 5-year-old child with chronic otitis media and a history of poorly controlled asthma presents for placement of ventilating ear tubes. General anesthesia is required for this short elective ambulatory surgery procedure. What preanesthetic medication should be administered Which of the three commonly used anesthetic techniques would you choose to use in this situation (1) inhalational anesthesia with sevoflurane for induction and maintenance in combination with nitrous oxide, (2) intravenous anesthesia with propofol for induction and maintenance of anesthesia in combination with remifentanil, or (3) balanced anesthesia using propofol for induction of anesthesia followed by a combination of sevoflurane and nitrous oxide for maintenance of anesthesia ... 

Midazolam Slow onset and recovery flumazenil reversal available Used in balanced anesthesia and conscious sedation provides cardiovascular stability and marked amnesia... 

Halothane, isoflurane, and enflurane have similar depressant effects on the EEG up to doses of 1-1.5 MAC. At higher doses, the cerebral irritant effects of enflurane may lead to development of a spike-and-wave pattern and mild generalized muscle twitching (ie, myoclonic activity). However, this seizure-like activity has not been found to have any adverse clinical consequences. Seizure-like EEG activity has also been described after sevoflurane, but not desflurane. Although nitrous oxide has a much lower anesthetic potency than the volatile agents, it does possess both analgesic and amnesic properties when used alone or in combination with other agents as part of a balanced anesthesia technique. 

Recovery is sufficiently rapid with most intravenous drugs to permit their use for short ambulatory (outpatient) surgical procedures. In the case of propofol, recovery times are similar to those seen with sevoflurane and desflurane. Although most intravenous anesthetics lack antinociceptive (analgesic) properties, their potency is adequate for short superficial surgical procedures when combined with nitrous oxide or local anesthetics, or both. Adjunctive use of potent opioids (eg, fentanyl, sufentanil or remifentanil see Chapter 31) contributes to improved cardiovascular stability, enhanced sedation, and perioperative analgesia. However, opioid compounds also enhance the ventilatory depressant effects of the intravenous agents and increase postoperative emesis. Benzodiazepines (eg, midazolam, diazepam) have a slower onset and slower recovery than the barbiturates or propofol and are rarely used for induction of anesthesia. However, preanesthetic administration of benzodiazepines (eg, midazolam) can be used to provide anxiolysis, sedation, and amnesia when used as part of an inhalational, intravenous, or balanced anesthetic technique. 

A randomized double-blind study including 40 patients undergoing elective hysterectomy under standardized balanced anesthesia were reported by Lehmann et al. in 1989. In a recovery room patients were allowed to self-administer fentanyl by means of the On-Demand Analgesia Computer. Demand dose was 34.5 pg, infusion rate 4 pg/h, lockout time 1 min, hourly max. dose = 250 pg. The patients were randomly and double-blindly assigned to have an additional infusion of either placebo... 

As a component of balanced anesthesia (intravenous administration) For control of ethanol or other sedative-hypnotic withdrawal states For muscle relaxation in specific neuromuscular disorders... 

Several drugs are used intravenously, alone or in combination with other drugs, to achieve an anesthetic state (as components of balanced anesthesia) or to sedate patients in intensive care units who must be mechanically ventilated. These drugs include the following (1) barbiturates (thiopental, methohexital) (2) benzodiazepines (midazolam, diazepam) (3) opioid analgesics (morphine, fentanyl, sufentanil, alfentanil, remifentanil) (4) propofol (5) ketamine and (6) miscellaneous drugs (droperidol, etomidate, dexmedetomidine). Figure 25-2 shows the structures of... 

Propofol (2,6-diisopropylphenol) is an extremely popular intravenous anesthetic. Its rate of onset of action is similar to that of the intravenous barbiturates recovery is more rapid and patients are able to ambulate sooner after propofol. Furthermore, patients subjectively "feel better" in the immediate postoperative period after propofol as compared with other intravenous anesthetics. Postoperative nausea and vomiting is less common because propofol has antiemetic actions. Propofol is used for both induction and maintenance of anesthesia however, cumulative effects can delay arousal following prolonged infusion. These favorable properties are responsible for the extensive use of propofol as a component of balanced anesthesia and for its great popularity as an anesthetic for use... 

A rough estimation whether anesthesia might relevantly misrepresent the situation of an awake animal should be performed comparing the bile excretion with the excretion via feces from the mass balance study (see example), the urine excretion or the radioactivity concentration in blood (so the bile fistula study should be extended to collect also body fluids such as terminal blood or the urine during the anesthesia). 

In man, potentiation and prolongation of the action of atracurium by halothane (62-64) have been reported, as has potentiation after 30 minutes of isoflurane anesthesia (65). Whether the dose of atracurium should be reduced from that used during balanced anesthesia by 20, 30, or 50% when patients are anesthetized with inhalational anesthetics can only be decided in the case of an individual patient if neuromuscular monitoring is available, since many other variables, such as the tissue concentrations of the volatile anesthetic and the response of the individual patient to the neuromuscular blocking drug, will influence the overall blocking effect. 

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