Advantages and guidelines for using isoflurane.

Isoflurane offers many advantages over other inhalational anesthetics. Its faster induction and recovery, relative sparing effect on cardiovascular function and cerebral blood flow autoregulation, and negligible metabolism make this drug particularly useful in the anesthetic management of the debilitated, aged, or unusual veterinary patient.     

Advantages and guidelines for using halothane.

Halothane is a frequently used agent. Its cost is inexpensive. Halothane is a safe and effective anesthetic agent if used properly. Proper usage includes adjusting the concentration administered to produce adequate anesthesia for the procedure without excess depression of cardiac, respiratory, and neurologic function. Proper monitoring of the patient indicates the adjustments needed in concentration or needed medications or procedures to increase safe usage. Potent tranquilizers, sedatives, and analgesics used as preanesthetics during halothane anesthesia or the early postanesthetic period may produce profound changes in anesthetic concentrations required or physiologic responses to the combined medications.     

Advantages and guidelines for using methoxyflurane.

Methoxyflurane anesthesia is particularly useful for orthopedic surgery (muscle relaxation, analgesia, and slow recovery), ophthalmic surgery (central eye position), and small laboratory animals (high therapeutic index and slow induction).     

Advantages and guidelines for using nitrous oxide.

Nitrous oxide is useful as an adjunct to methoxyflurane anesthesia and prolonged halothane anesthesia. Nitrous oxide is also useful in the debilitated patient in which the potent volatile anesthetics induce excessive cardiovascular depression. Finally nitrous oxide is useful for smoothing an inadequate anesthetic plane induced by the potent volatile anesthetics.     

Advantages and guidelines for using opioid agonist-antagonist analgesics.

The opioid agonist-antagonists are not controlled substances requiring strict record keeping and security because of their low abuse potential. They are effective analgesics in their own right and can be used to antagonize opioid agonist-induced depression while retaining a degree of analgesia. Respiratory depression is less than that induced by opioid agonists, but degree of analgesia is somewhat limited also owing to the ceiling effect.     

Advantages of and guidelines for using neuromuscular blocking agents.

Neuromuscular blocking agents, although not commonly used in veterinary practice, should be considered when muscle relaxation is needed to facilitate surgical exposure and minimize tissue trauma. These drugs should be administered only once respiration has been controlled and anesthetic agents have been administered to induce unconsciousness and analgesia. Following administration of neuromuscular blocking drugs, neuromuscular and cardiovascular function must be monitored.     

Advantages and guidelines for using ketamine for induction of anesthesia.

Ketamine in combination with a sedative or tranquilizer is a relatively safe and effective drug for intravenous induction of anesthesia in dogs and cats. If properly dosed, the combination can be used to induce anesthesia with minimal adverse cardiovascular effects, and it is a reasonable method for induction of anesthesia in patients with cardiac disease. If dosage is kept low, the rate of recovery is acceptable, and some of the drugs commonly used in the regimen with ketamine are reversible with appropriate antagonists.     

Advantages and guidelines for using opioid agonists for induction of anesthesia.

Opioids have a central role in the anesthetic management of small animals, as premedicants, as part of a balanced anesthetic technique, or for the provision of postoperative analgesia. These drugs are safe to use, provide excellent analgesia, and are easily reversible. They cause minimal cardiovascular depression and induce no deleterious renal or hepatic changes. These agents, combined with a sedative, generally provide an ideal anesthetic state.     

Advantages and guidelines for using ultrashort barbiturates for induction of anesthesia.

Despite the introduction of a number of new injectable agents, ultrashort barbiturates continue to be popular. Some of the reasons include rapid, smooth onset of action; predictable hypnotic effects; relatively rapid, smooth recovery; and inexpensiveness. Ultrashort barbiturates also possess some pharmacodynamic properties that make them ideal agents for use in patients with certain diseases or undergoing certain procedures. These include patients with raised intracranial pressure, patients with a history of seizures, patients with corneal lacerations or glaucoma, patients for examination of vocal cord and arytenoid cartilage function, patients with hyperthyroidism, and patients thought to be susceptible to malignant hyperthermia.     

Caudal epidural analgesia in cattle using xylazine.

Each of 25 mature Holstein cows were given a single 5 mL epidural injection of one of four different concentrations of xylazine or saline. The onset, magnitude and duration of caudal epidural analgesia was quantitated with the use of a low voltage DC current applied to the perineal area. The dose that produced the longest duration of analgesia and produced the least ataxia or sedation was approximately 0.05 mg/kg (25 mg in 5 mL diluent). The analgesia produced by this xylazine dose was compared to a standard dose of epidural lidocaine (100 mg/5 mL) by the same method. To investigate the role of systemic absorption in the production of epidural analgesia, the previously utilized epidural xylazine dosage was given intramuscularly to four adult cows. Analgesia was quantitated as before and the results compared with epidural xylazine. Epidural xylazine produced a significantly greater duration of analgesia, as measured by this model, than did epidural lidocaine. Xylazine, given epidurally, produced greater perineal analgesia than did xylazine given intramuscularly.     

Advantages and guidelines for mask induction.

Inhalational agents with low blood/gas solubilities (halothane, isoflurane, and nitrous oxide) are preferred for mask induction. A gradual step up in the vaporizer concentration is the recommended induction method because it is generally smoother and safer than the crash induction technique.     

Advantages and guidelines for using alpha-2 agonists as anesthetic adjuvants.

Xylazine and medetomidine produce reliable sedation, muscle relaxation, and analgesia in dogs and cats. In addition, alpha-2 agonists have proved very effective as sedative-analgesic adjuncts when coadministered with benzodiazepine or opioid agonists. Alpha-2 agonists should not be classified as monoanesthetics. They are excellent anesthetic adjuncts when combined with dissociatives and opioids. Because of the acute alterations in cardiopulmonary function commonly induced by alpha-2 agonists, it is suggested that their use be restricted to the young healthy patient undergoing routine surgical or diagnostic procedure. The development of more specific and selective alpha-2 agonists will continue to enhance the safety and reliability of this novel class of compounds. The unique spectrum of anesthetic properties induced by alpha-2 agonists has assured them of an increasingly prominent role in the development of new and sophisticated ways of achieving anesthesia.     

Comparison of epidural and systemic tramadol for analgesia following ovariohysterectomy

The objective of the study was to compare epidural and systemic tramadol for postoperative analgesia in bitches undergoing ovariohysterectomy. Twenty animals, randomly divided into two groups, received either epidural (EPI) or intramuscular (IM) tramadol (2 mg/kg) 30 min before anesthetic induction. Analgesia, sedation, cardiorespiratory parameters, end-tidal isoflurane, blood catecholamines and cortisol, and arterial blood gases were measured at different time points up to 24 hr after agent administration. There were no differences between the two groups regarding cardiorespiratory parameters, end-tidal isoflurane, and pain scores. Two dogs in the IM and one in the EPI group required supplemental analgesia. Cortisol was increased (P<0.05) at 120 min (3.59 μg/dL and 3.27μg/dL in the IM and EPI groups, respectively) and 240 min (2.45 μg/dL and 2.54μg/dL in the IM and EPI groups, respectively) compared to baseline. Norepinephrine was also increased (P<0.05) at 120 min in both groups compared to baseline values. Epinephrine values were higher (P<0.05) in the IM group compared with the EPI group at 50 min, 120 min, and 1,440 min after tramadol administration. Epidural tramadol is a safe analgesic, but does not appear to have improved analgesic effects compared with IM administration.