Induction anesthesia

Halothane (Fluothane) is a volatile liquid given by inhalation for induction and maintenance of anesthesia Induction and recovery from anesthesia are rapid, and the depth of anesthesia can be rapidly altered. Halothane does not irritate the respiratory tract, and an increase in tracheobronchial secretions usually does not occur. Halothane produces moderate muscle relaxation, but skeletal muscle relaxants may be used in certain types of surgeries. This anesthetic may be given with a mixture of nitrous oxide and oxygen. 

IV Relief of severe pain pain of Ml used preoperatively to sedate the patient and allay apprehension, facilitate anesthesia induction, and reduce anesthetic dosage control postoperative pain relieve anxiety and reduce left ventricular work by reducing preload pressure treatment of dyspnea associated with acute left ventricular failure and pulmonary edema produce anesthesia for open-heart surgery. 

Various barbiturates such as the short acting agent pentobarbital and the ultra-short acting agents thiopental and methohexital are used for anesthesia induction. They produce loss of consciousness without analgesia and with little effects on the cardiovascular system. Unconsciousness is combined with respiratory depression as the barbiturates produce non-selective CNS depression. 

Anesthesia induction with propofol causes a significant reduction in blood pressure that is proportional to the severity of cardiovascular disease or the volume status of the patient, or both. However, even in healthy patients a significant reduction in systolic and mean arterial blood pressure occurs. The reduction in pressure appears to be associated with vasodilation and myocardial depression. Although propofol decreases systemic vascular resistance, reflex tachycardia is not observed. This is in contrast to the actions of thiopental. The heart rate stabilization produced by propofol relative to other agents is likely the result of either resetting or inhibiting the baroreflex, thus reducing the tachy-cardic response to hypotension. 

Although the use of ketamine for anesthesia induction when seizure duration is insufficient has also been recommended, recent studies did not find this agent to be helpful (100, 101, 102 and 103). Disadvantages of ketamine include the following ... 

Kulka, P.J., Bremer, F., and Schuttler, J. (1993) [Anesthesia induction using etomidate in a lipid emulsion] (Germany)Anaesthesist, 42 205-209. 

Johnson et al. (1998) compared isoflurane with sevoflurane for anesthesia induction and recovery in adult dogs. 

Johnson RA, StrilerE, Sawyer DC, BrunsonDB (1998)Compar-ison of isoflurane with sevoflurane for anesthesia induction and recovery in adult dogs. Am J Vet Res 59 487—481 Kanaya N, Kawana S, Tsuchida H et al. (1998) Comparative myocardial depression of sevoflurane, isofluorane, and halothane in cultured neonatal rat ventricular myocytes. Anesth Analg 67 1041-1047... 

Safety and efficacy for reversal of benzodiazepine overdose, general anesthesia induction or resuscitation of a ne A/born have not been established, but anecdotal data suggest similar safety and efficacy as for conscious sedation... 

Simultaneous scalp and depth electrode recordings were performed on five patients with complex partial epilepsy who underwent alfentanil anesthesia induction before depth electrode removal (7). Five equal bolus doses of alfentanil 100 gg were given to each patient at 60-second intervals (total dose 500 gg). Epileptiform activity was increased in three of the five, but without clinical evidence of seizure activity. 

In contrast to isoflurane and desflurane, sevoflurane tends not to increase the heart rate, and is usually well tolerated for induction of anesthesia in young children. However, profound bradycardia was reported in four unpremedicated children aged 6 months to 2 years during anesthesia induction with sevoflurane 8% and nitrous oxide 66% (7). The episodes were not associated with loss of airway or ventilation. In three of the children there was spontaneous recovery of heart rate when the sevoflurane concentration was reduced the other child received atropine because of evidence of significantly reduced cardiac output. In a previous study of sevoflurane induction of anesthesia in children with atropine premedication there was also a low incidence of this complication (8), which is probably due to excessive sevoflurane concentrations. 

Thiopentai Anesthesia induction (indiyidualized) Flepatic 100% 100% 100% Group toxicity No data No data No data... 

One dosing cohort received 75 U kg rhAT, and the other cohort received a normal sahne placebo (both as single bolus intravenous injection). Heparin resistance was defined as failure to achieve an ACT of >480 seconds after receiving a total dose of 400 U kg heparin intravenously after anesthesia induction and surgical incision, but just prior to CPB. The proportion of rhAT patients who required administration... 

Another nonbarbiturate anesthetic is the imidazole carboxylate etomidate. Even though it produces no analgesia, it is used with fentanyl (see later) to produce very rapid anesthesia induction. The drug s appeal is its minimal effect on respiration and the cardiovascular system. Unlike many of the volatile compounds, it produces no annoying histamine release. It does cause intermittent muscle twitching. 

The production and maintenance of the anesthetic state is believed by most to be dependent on the concentration, or partial pressure, of the anesthetic agent in yet unknown areas of the brain. Obviously, the concentration of the anesthetic agent in the gas mixture administered, as well as the rate and depth of respiration of the patient, will influence the rate of anesthesia induction. The rate at which delivery of anesthetic agents to these sites occurs is dependent on their physicochemical properties, particularly their solubility in lipid and blood. 

Midazolam. Give 0.05 mg/kg (up to 0.35 mg/kg for anesthesia induction) IV over 20-30 seconds (usual adult doses vary 1 mg to maximum of 5 mg given in increments of 2.5 mg every 2 minutes lower dose in geriatric patients with maximum at 3.5 mg) or 0.07-0.1 mg/kg IM. Repeat after 10-20 minutes if needed. Continuous infusions have also been used to maintain effect with initial rates of 0.02-0.1 mg/kg/h (usual adult dose 1-7 mg/h children 1-2 mcg/kg/min) and then titrated to effect. Caution There have been several reports of respiratory arrest and hypotension after rapid intravenous injection, especially when midazolam is given in combination with opioids. Prolonged continuous infusion may lead to persistent sedation after the dmg is discontinued because midazolam accumulates in tissues. 

Egan TD, Brock-Utne JG. As3rstole after anesthesia induction with a fentanyl, propofol, and... 

Part 2 Prior to anesthesia induction, the patient is identified again by name and birth date, which are compared with ID bracelet and records. The scheduled surgical procedure is confirmed by the patient, and the surgical site marking by the OR staff. A brief review of patient s written informed consent, allergies, fasting interval, airway anatomy, ordered antibiotic prophylaxis, availability of blood products and readiness of anesthesia equipment is completed. Specifically in these patients, preoperative information is verified on correct medication intake, on fluid restriction orders, the interval since last hemodialysis and residual urinary output. 

Gooding, J. M. and Corssen, G. (1976) Etomidate an ultrashort actiiig nonbarbiturate agent for anesthesia induction. Anesth. Analg. Curr. Res., 55, 286. 

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