[Ketamine for subarachnoid anesthesia during hypovolemia: preliminary study in pigs]

OBJECTIVES

To assess whether subarachnoid ketamine has fewer hemodynamic effects than lidocaine in normal and hypovolemic pigs and to determine whether or not the effects of ketamine are dose-dependent.

METHODS

Thirty pigs were randomly allocated to receive subarachnoid administration of lidocaine 2 mg x kg(-1), ketamine 1 mg x kg(-1) or ketamine 2 mg x kg(-1), in a situation of either normal or reduced blood volume. The pigs were assigned to six groups: group L2 (2% lidocaine 2 mg x kg(-1), normovolemia), group L2H (2% lidocaine 2 mg x kg(-1), hypovolemia), group K1 (ketamine 1 mg x kg(-1), normovolemia), group K1H (ketamine 1 mg x kg(-1), hypovolemia), group K2 (ketamine 2 mg.kg(-', normovolemia), and group K2H (ketamine 2 mg x kg(-1), hypovolemia). To induce hypovolemia 30% of the calculated blood volume was withdrawn from each pig. The subarachnoid space was catheterized, and invasive measurements of hemodynamic variables (derived from arterial, central venous and pulmonary artery catheter monitoring) were obtained. Variables were recorded at baseline and 5 and 15 min after drug injection in the normovolemic groups, and at baseline after inducing hypovolemia and 5 and 15 min after drug injection in the hypovolemic groups.

RESULTS

In the normovolemic pigs no significant differences were detected between groups. In hypovolemic pigs differences were observed in heart rate and arterial pressure between the ketamine 1 mg x kg(-1) and lidocaine 2 mg x kg(-1) groups (P < 0.05). The decreases in heart rate and arterial pressure were less marked in the ketamine group. Mixed venous oxygen saturation and cardiac index deteriorated to a lesser degree in both ketamine groups than in the lidocaine groups (P < 0.05).

CONCLUSIONS

Racemic ketamine administered by subarachnoid injection in hypovolemic pigs produces less deterioration in hemodynamic variables than does lidocaine. Hemodynamic changes caused by ketamine were not dose-dependent. These findings may be of interest, given the increased use of ketamine in neuroaxial anesthesia and analgesia and perhaps the possible use of neuroaxial ketamine in hypovolemic patients.

Effects of a midazolam-ketamine admixture in human volunteers

As the ideal sedative does not exist for all situations, we examined the effect of a midazolam-ketamine sedoanalgesic admixture in human volunteers. Ten ASA physical status I volunteers were administered loading doses of 0.07 mg/kg of midazolam followed by 0.7 mg/kg of ketamine. The same amount of midazolam and ketamine was then infused constantly over 1 hour via a 60 drops (gtts)/mL i.v. infusion set. Blood samples were analyzed for plasma catecholamine levels. Respiration rate and oxygen saturation did not alter significantly from baseline levels. Heart rate and systolic blood pressure remained stable with an increase of 15% in heart rate and 6% in systolic blood pressure only at 10 minutes following the bolus loading. Diastolic blood pressure did not alter significantly from baseline levels (P < .05). Plasma catecholamines levels remained stable except for an increase in epinephrine (38%) and norepinephrine (19%) 10 minutes following the bolus injections. Plasma dopamine levels remained unchanged. There were no cases of unpleasant dreaming, dysphoria, or emergence-type reactions. This combined nonnarcotic sedoanalgesic technique maintains spontaneous ventilation and stable cardiorespiratory parameters and may be considered as an alternative to traditional conscious sedation or general anesthesia.

[Injection anesthesia administered in the mid-anesthesia period after ether induction in laboratory rats]

Our experience with anaesthetic combination of butyrophenone derivative droperidol (D, 0.8 mg/kg b.w.) + alpha-2-agonist xylazine (X, 5 mg/kg b.w.) + ketamine (X, 35 mg/kg b.w.), in 28 rats (12 female, 8 + 8 male) is described. Anaesthesia protocol started with ether inhalation (5 ml/l air) in a glass bell. When the effect of anaesthesia was evident, droperidol and xylazine with ketamine were administered in an intramuscular injection. At the same time as anaesthetics, atropine (0.05 mg/kg b.w.) was injected subcutaneously. Average time of induction of ether anaesthesia was 45 +/- 30 s. and duration of the surgical stage was 64 +/- 16 s. Average time of recurrence of the position reflex was 120 min. D + X + K anaesthetic combination is safe, cost effective, and it induces good analgesia and myorelaxation. Anaesthetic effect is possible to prolong with half dose of ketamine with half dose of droperidol or xylazine in 30 to 40 min. interval and the next prolongation is possible in 20 min. interval. The presented combination of anaesthetic was used for the soft tissue surgery (laparotomy, thoracotomy, and cannulation of large vessels--a. carotis, v. jugularis), both in experiments and clinical praxis.

Effects of ketamine on electroencephalographic and autonomic arousal and segmental reflex responses in the cat

OBJECTIVE

To provide evidence concerning doses of ketamine that affect electroencephalographic (EEG) and autonomic signs of arousal during nociceptive stimulation.

STUDY DESIGN

Prospective psychophysical test in people. Single injection or progressively increasing infusions of ketamine in cats. ANIMALS AND PEOPLE: Seven people (20-60 years old) and three cats (3-5 kg) for EEG recording and six cats for EMG recordings.

METHODS

In order to define innocuous and nociceptive stimulus intensities which could be applied to cats to evaluate arousal, psychophysical evaluations of sensations elicited by compression of the skin overlying phalangeal bones of the hand were obtained from human subjects. Then, following administration of ketamine, recordings of EEG frequency and of autonomic responses (heart rate, respiratory rate and arterial blood pressure) were obtained before and during stimulation of the tails of cats at pressures identified by human observers as either innocuous or nociceptive. Observations of withdrawal reflexes of the hindlimbs following interdigital skin stimulation were interposed between recording periods. In separate sessions, stretch reflex activity was assessed during awake and anesthetic conditions by recording electromyographic activity from soleus muscles and resistive force to dorsiflexion of the tibiotarsal joint.

RESULTS

There were no changes in either total EEG (0.5-30.0 Hz), low-frequency (0.6-7.5 Hz) or high-frequency (7.5-30.0 Hz) power produced by nociceptive stimulation for a period of 18-24 minutes following an intramuscular bolus dose of ketamine (33.0 mg kg-1), although withdrawal reflexes were present. Thereafter, nociceptive stimulation produced EEG arousal responses in the low-frequency and total power range and increased systolic blood pressure and respiration rate. In tests after intravenous infusion of ketamine (10.0-22.2 mg kg-1 hour-1), total and low-frequency EEG power and autonomic responses to nociceptive stimulation were eliminated. Organized motor responses were never elicited during IV infusion, but withdrawal reflexes were observed at each dosage. Also, stretch reflexes were shown by quantitative analysis to be retained at all doses of ketamine infusion.

CONCLUSIONS AND CLINICAL RELEVANCE

These results show that testing of withdrawal reflexes does not reveal the adequacy of ketamine anesthesia. Segmental stretch and withdrawal reflexes are preserved and can be investigated during infusion of ketamine at doses that eliminate arousal from brief periods of nociceptive stimulation.

Intraoperative Intravenous Ketamine in Combination with Epidural Analgesia: Postoperative Analgesia After Renal Surgery

We designed this double-blinded, randomized, controlled study to evaluate the effect of small-dose ketamine IV in combination with epidural morphine and bupivacaine on postoperative pain after renal surgery. An epidural catheter was inserted, and the administration of morphine and bupivacaine was started before surgery. Forty patients were assigned to one of two groups (ketamine or control). The ketamine group was administered a ketamine bolus and infusion during surgery. The median visual analog pain scale (VAS) scores at rest were significantly lower in the ketamine group during the first 6 h (P < 0.01). VAS pain scores on coughing were also significantly lower in the ketamine group (P < 0.01). Cumulative postoperative total analgesic consumption was less in the ketamine group on Days 1 and 2 (P < 0.001). The first analgesic demand time was shorter in the control group (9.2 +/- 11.5 min) than in the ketamine group (22.3 +/- 17.1 min) (P < 0.0001). The incidence of nausea and pruritus was more frequent in the control group (P < 0.05). In conclusion, postoperative analgesia was more effective when spinal cord and brain sensitization were blocked by a combination of epidural morphine/bupivacaine and IV ketamine.

IMPLICATIONS

Renal nociception conducted multisegmentally by both the spinal nerves (T10 to L1) and the vagus nerve cannot be blocked by epidural analgesia alone. We demonstrated that IV ketamine had an improved analgesic or opioid-sparing effect when it was combined with epidural bupivacaine and morphine after renal surgery.

ANESTHETIC INDUCTION OF CAPTIVE TIGERS (PANTHERA TIGRIS) USING A MEDETOMIDINE–KETAMINE COMBINATION

Six adult female tigers (Panthera tigris) were anesthetized repeatedly for elective medical procedures using 3 mg medetomidine and 200 mg ketamine i.m. Inductions were rapid and smooth, although supplemental ketamine was needed for safe transport after induction in 6 of 17 procedures. Reversal of the medetomidine-induced sedation with 15 mg atipamezole i.m. 59-232 min after induction resulted in smooth, rapid recoveries.

The effects of small-dose ketamine on morphine consumption in surgical intensive care unit patients after major abdominal surgery

In a randomized, double-blinded study, we evaluated the analgesic effect of ketamine in the management of pain in a surgical intensive care unit after major abdominal surgery. Patients received morphine patient-controlled analgesia with either placebo (Group M) or ketamine (Group K). Morphine was administered with initial loading doses of 2 mg until the visual analog scale (VAS) score was <30 and thereafter with bolus doses of 1 mg and a lockout time of 7 min. Ketamine was administered with an initial bolus of 0.5 mg/kg followed by a perfusion of 2 micro g x kg(-1) x min(-1) during the first 24 h and 1 micro g x kg(-1) x min(-1) during the following 24 h. The 4-h cumulative morphine doses were measured over 48 h. The VAS scores at rest and at mobilization were measured every 4 h during 48 h. A total of 101 patients were enrolled, and 93 were analyzed (41 in Group K and 52 in Group M). VAS scores at rest and at mobilization were similar. The cumulative consumption of morphine was significantly smaller in Group K (P < 0.05). We concluded that small doses of ketamine were a valuable adjunct to opioids in surgical intensive care unit patients after major abdominal surgery.

Effect of alkalinization on the local analgesic efficacy of ketamine in the abaxial sesamoid nerve block in horses

The objective of this study was to determine the effects of the alkalinization on the local analgesic efficacy of 1% ketamine in the abaxial sesamoid nerve block in horses. Thirty-six mature healthy horses were randomly assigned to four groups for the following treatments; an abaxial sesamoid block with 5 mL of saline solution (control saline); an abaxial sesamoid block with 5 mL of a solution containing 1% ketamine (KETs 1%); an abaxial sesamoid block with 5 mL of a solution containing saline solution and 0.5 mEq of sodium bicarbonate (control bicarbonate); and an abaxial sesamoid block with 5 mL of a solution containing 1% ketamine and 0.5 mEq of sodium bicarbonate (KETb 1%). All blocks were performed in one randomly selected front leg. To determine analgesia, hoof withdrawal from thermal stimulus from radiant heat lamp was assessed. Before each block, the hoof withdrawal reflex latency (HWRL) (time between lamp illumination and withdrawal of the hoof) was determined; after the block, local analgesic effects were determined using the heat lamp at 2 and 5 min after the injection and then every 5 min for 1 h. In KETs 1% group, there were significant increases in HWRL between basal values and values from 2 to 10 min after an abaxial sesamoid block. In KETb 1% group, significant increases in HWRL was collected between the basal value and values from 2 to 25 min following an abaxial sesamoid block. In KETs 1% group, of the nine horses, four had an abaxial sesamoid block that was unsuccessful. However, in KETb 1% group, only one of the nine horses had an abaxial sesamoid nerve block that was unsuccessful. The alkalinization of a 1% ketamine solution produced a more consistent and persistent local analgesia in horses when compared with 1% ketamine solution alone.

Comparison of ketamine versus combination of ketamine and medetomidine in injectable anesthetic protocols: chemical immobilization in macaques and tissue reaction in rats

This study compared balanced anesthesia between ketamine alone and ketamine with medetomidine and assessed the repeated intramuscular use of ketamine and its potential for tissue damage. The combination of ketamine and medetomidine was tested in newly arrived macaques undergoing a period of quarantine in an animal facility. Results indicated that the medetomidine and ketamine combination induced a deeper, more level plane of anesthesia of longer duration than did ketamine alone. Furthermore, use of the medetomidine-reversing agent, atipamezole, permitted more rapid recovery. In addition, a preliminary study in adult rats was undertaken to assess tissue damage induced by intramuscular injection of ketamine versus the combination of ketamine and medetomidine. Histological evaluation of tissue inflammation and muscle necrosis in rats indicated that the lower dose of ketamine afforded by combination with medetomidine caused markedly less damage to muscle tissue at injection sites.

Effect of ovariohysterectomy on canine postsurgical leukocyte function

The effect of surgery on phagocytic activity of blood leukocytes and mitogen-induced blastogenesis of lymphocytes was studied in fourteen dogs. Simple ovariohysterectomy with anaesthesia induced by ketamine and xylazine or by ketamine, xylazine and halothane caused a short nonsignificant depression of phagocytic activity that persisted for four hours after surgery. Ingestion capacity of leukocytes decreased significantly immediately after surgery. Mitogen-induced blastogenesis of lymphocytes was depressed significantly in the first 48 hours and despite partial recovery this parameter did not reach the value of the control groups until the end of observation (7 days). A more conspicuous decrease of blastogenic response of blood lymphocytes to mitogens was found after the use of ketamine and xylazine in a dose maintaining anaesthesia. Anaesthesia with ketamine and xylazine in the lower dose and maintained with halothane resulted in a later improvement of the blastogenic response of lymphocytes.

Sedation with midazolam and ketamine for invasive procedures in children with malignancies and hematological disorders: a prospective study with reference to the sympathomimetic properties of ketamine

Different pharmacological agents have been used for sedation in children undergoing invasive procedures. The authors prospectively evaluated the efficacy, the occurrence of adverse side effects, and cardiovascular parameters in midazolam and ketamine sedation for invasive procedures in children with malignancies and hematological disorders. A total of 183 invasive procedures were performed on 63 children (mean age 9.2 +/- 5.2 years). Intravenous sedation consisted of 0.1 mg midazolam/kg and 1.0 mg ketamine/kg. Incremental dosages of ketamine (0.33 mg/kg) were given if necessary to maintain deep sedation. Systolic and diastolic blood pressure, heart rate, and oxygen saturation were recorded. All 183 invasive procedures were successfully completed with satisfactory sedation levels in 170 procedures (92.9%; 95% CI:88.2-96.2%). In 33 procedures (18%; 95% CI: 12.8-24.4%) sedation was associated with side effects, the most common being oxygen desaturation. One patient experienced a transient episode of laryngospasm. There was a significant increase in both systolic and diastolic blood pressure and heart rate after ketamine medication (p <.01). Procedure and recovery time were correlated to ketamine dosage (p <.01). The combination of midazolam and ketamine is efficacious in achieving deep sedation for painful invasive procedures. Considering the possibility of potentially serious respiratory complications it should be performed only by physicians who are trained in advanced airway management and life support. As opposed to many other sedative drugs with cardio-depressant properties, ketamine causes a rise in both systolic and diastolic blood pressure, and heart rate.

Ketamine-induced changes in rat behaviour: A possible animal model of schizophrenia

It was investigated whether subchronic application of 30 mg/kg ketamine (Ket) induces reliable changes in behaviour and parameters of dopaminergic, glutamatergic, and serotonergic neurotransmissions, which might be the basis of an animal model in schizophrenia research. To test this, rats were injected with 30 mg/kg ip Ket daily for five consecutive days. In response to the first Ket injection, there was a decrease in activity time representing an acute Ket effect. Following the fifth injection, there were no differences between Ket- and saline (sal)-injected control rats in activity time, which might be a tolerance reaction. The following experiments were performed 2 or 4 weeks after Ket treatment. There were no effects on anxiety in either vehicle or Ket-treated rats using either low or high illumination levels in the elevated plus-maze. In the social interaction test, both groups of rats spent comparable times in social contact. The percentage of nonaggressive behaviour was decreased in Ket-treated rats. Two weeks after completion of the treatment, there was no effect on prepulse inhibition (PPI). Four weeks after the final Ket injection, latent inhibition (LI) was disrupted. There was no difference in the animals' activity in reaction to apomorphine (Apo) administration. Ket-treated rats injected with 0.1 mg/kg MK-801 showed an enhancement in locomotor activity. Ket treatment leads to an increase in D2 receptor binding in the hippocampus and a decrease in glutamate receptor binding in the frontal cortex. The authors did not find any changes in D1 receptor binding. The density of dopamine transporters was increased in the striatum. The density of 5-HT transporters was increased in the striatum, the hippocampus, and the frontal cortex. The results suggest that subchronic treatment with subanaesthetic doses of Ket induce schizophrenia-related alterations, which might be a useful animal model in the study of this disease.

Effects of ketamine and propofol on the ratio of interleukin-6 to interleukin-10 during endotoxemia in rats

Our previous study reported that the change in the ratio of interleukin (IL)-6 to IL-10 influences the severity of sepsis in patients with systemic inflammatory response syndrome. We evaluated the change in the ratio of IL-6 to IL-10 after administration of ketamine or propofol in endotoxin-exposed rats in order to evaluate the relationship of pro-inflammatory and anti-inflammatory cytokines following ketamine or propofol administration during endotoxemia. We randomly assigned 40 rats to one of four equal groups: endotoxin alone, receiving Escherichia coli endotoxin (15 mg/kg, i.v.); saline control; ketamine (10 mg x kg(-1) x h(-1), i.v.) before and during exposure to endotoxin; and propofol (10 mg x kg(-1) x h(-1), i.v.) before and during exposure to endotoxin. We measured the plasma concentrations of tumor necrosis factor (TNF)-alpha, IL-6, and IL-10 and calculated the ratio of IL-6 to IL-10 in each group. The current study showed that ketamine and propofol administration attenuated the increase in TNF-alpha, IL-6, and IL-10, and ketamine attenuated the increase in the ratio of IL-6 to IL-10, but propofol increased this ratio in rats receiving a single intravenous bolus of endotoxin. While the mechanisms responsible for the inhibitory effects require further investigation, our results suggest that proper use of ketamine as an anesthetic agent may offer certain advantages in the management of patients with endotoxemia.

Racemic ketamine does not abolish cerebrovascular autoregulation in the pig

BACKGROUND

Little is known about the influence of racemic ketamine on autoregulation of cerebral blood flow (CBF), and available reports regarding its influence on cerebral hemodynamics are contradictory. This study was designed to evaluate cerebrovascular responses to changes in the mean arterial pressure (MAP) during ketamine anesthesia.

METHODS

In eight normoventilated pigs anesthesia was induced with propofol and maintained by i.v. infusion of ketamine (15.0 mg kg(-1) x h(-1)) during measurements. The intra-arterial xenon clearance technique was used to calculate CBF. Balloon-tipped catheters were introduced in the inferior caval vein and mid-aorta, and increases or decreases by up to 40% in mean arterial pressure (MAP) in random order were achieved by titrated inflation of these balloon catheters. Cerebral blood flow was determined at each MAP level. Regression coefficients of linear pressure-flow curves were calculated in all animals.

RESULTS

From the mean baseline level (101 mmHg) MAP was reduced by 20% and 40%, and increased by 26% and 43%. The maximal mean increase and decrease in MAP induced a 12% increase and a 15% decrease, respectively, of CBF from the mean baseline level (52.6 ml.100 g(-1) x min1). The 95% confidence interval (-0.02; 0.38) of the mean regression coefficient of individual pressure-flow curves does not include the regression coefficient (0.64) of a linear correlation between MAP and CBF including origo (correlation coefficient 0.99), which indicates complete lack of cerebrovascular autoregulation.

CONCLUSIONS

We conclude that autoregulation of CBF is not abolished during continuous ketamine infusion in normoventilated pigs and that previous divergent conclusions are unlikely to be associated with severe impairment of cerebrovascular autoregulation.

Experience with ketamine and sodium pentobarbital as anesthetics in a rat model of cardiac arrest and resuscitation

We review 7 years experience with the chest compression model of cardiac arrest and resuscitation, comparing two different anesthetics. Ketamine stimulates cardiac function and only mildly depresses respiration; of the two it provides easier resuscitation. However, ketamine severely depresses brain protein synthesis; in studies using this measure ketamine is unsuitable and another agent must be used. Sodium pentobarbital mildly depresses brain protein synthesis, but depresses both cardiac and respiratory function, making resuscitation more difficult. Use of alternate chest/abdominal pumping (Babbs resuscitation technique), with judicious use of intra-cardiac epinephrine (adrenaline), made resuscitation reliable under sodium pentobarbital as well.

Medetomidine-ketamine anaesthesia induction followed by medetomidine-propofol in ponies: infusion rates and cardiopulmonary side effects

REASONS FOR PERFORMING STUDY

To search for long-term total i.v. anaesthesia techniques as a potential alternative to inhalation anaesthesia.

OBJECTIVES

To determine cardiopulmonary effects and anaesthesia quality of medetomidine-ketamine anaesthesia induction followed by 4 h of medetomidine-propofol anaesthesia in 6 ponies.

METHODS

Sedation consisted of 7 microg/kg bwt medetomidine i.v. followed after 10 min by 2 mg/kg bwt i.v. ketamine. Anaesthesia was maintained for 4 h with 3.5 microg/kg bwt/h medetomidine and propofol at minimum infusion dose rates determined by application of supramaximal electrical pain stimuli. Ventilation was spontaneous (F(I)O2 > 0.9). Cardiopulmonary measurements were always taken before electrical stimulation, 15 mins after anaesthesia induction and at 25 min intervals.

RESULTS

Anaesthesia induction was excellent and movements after pain stimuli were subsequently gentle. Mean propofol infusion rates were 0.89-0.1 mg/kg bwt/min. No changes in cardiopulmonary variables occured over time. Range of mean values recorded was: respiratory rate 13.0-15.8 breaths/min; PaO2 29.1-37.9 kPa; PaCO2 6.2-6.9 kPa; heart rate 31.2-40.8 beats/min; mean arterial pressure 90.0-120.8 mmHg; cardiac index 44.1-59.8 ml/kg bwt/min; mean pulmonary arterial pressure 11.8-16.4 mmHg. Recovery to standing was an average of 31.1 mins and ponies stood within one or 2 attempts.

CONCLUSIONS

In this paper, ketamine anaesthesia induction avoided the problems encountered previously with propofol. Cardiovascular function was remarkably stable. Hypoxaemia did not occur but, despite F(I)O2 of > 0.9, minimal PaO2 in one pony after 4 h anaesthesia was 8.5 kPa.

POTENTIAL RELEVANCE

The described regime might offer a good, practicable alternative to inhalation anaesthesia and has potential for reducing the fatality rate in horses.

Effects of different subanaesthetic doses of (S)-ketamine on psychopathology and binocular depth inversion in man

The role of the N-methyl-D-aspartate (NMDA) neurotransmitter system in relation to psychoses is not completely understood, but represent a challenge in neurobiological research. The psychotic states induced by NMDA antagonists such as phencyclidine and ketamine have been described as being most similar to schizophrenia and the NMDA system has been implicated in the pathogenesis of schizophrenia. Binocular depth inversion, an illusion of visual perception, has been shown to be impaired in psychotic and psychotomimetic states in healthy and schizophrenic subjects. In this study, pictures of natural and artificial objects were presented stereoscopically to 12 healthy male volunteers and depth perception assessed using an operationalized method. The effects of the psychotomimetic S-enantiomer of the anaesthetic ketamine in two different subanaesthetic doses were compared with those of a placebo. In spite of dose dependence and grave subjective and significant objective psychopathology, no significant impairment of binocular depth perception was found with (S)-ketamine. Implications related to memory function, perceptogenesis and 'bottom-up' processing in ketamine model psychosis and schizophrenia are discussed.

The significance of intrathecal catheter location in rats

Although chronic intrathecal catheterization is a widely used method in rats, few calibration experiments have been performed. In this study, we investigated the correlation between the side position of the catheter tip and the side differences observed in the motor and sensory disturbances after intrathecal administration of lidocaine to a large number of rats. The existence of a sensory block was determined by the paw withdrawal test. The motor impairment was assessed by observing the complete clubbing of the hindpaw and measuring the hindpaw grip strength. After experimental use, we established the position of the catheter tip. The catheter tips were variously located in all directions of the transverse plane in the rat spinal subarachnoid space. Lidocaine administration (100 or 500 microg/5 microL; n = 264 and 112, respectively) led to dose-dependent motor and sensory disturbances. The effect of 100 microg of lidocaine exhibited side differences; i.e., the extents of both motor (r = 0.77) and sensory (r = 0.60 and r = 0.67 for the right and the left side, respectively) disturbances correlated significantly with the location of the catheter tip. Our data have shown that detection of the paralytic and/or antinociceptive effect of small-dose lidocaine before planned experiments is a simple and reliable method for prediction of the location of the catheter tip. We suggest that the position of the catheter might cause side differences in the drug effect, especially if small doses of drugs are administered and their effects are investigated on both sides.

Ventilatory response during dissociative sedation in children-a pilot study

OBJECTIVES

It is unclear whether ketamine induces subclinical respiratory depression when administered in dissociative doses intravenously (IV). The authors report a pilot study of capnography in emergency department (ED) pediatric patients receiving ketamine alone for procedural sedation, and describe serial measures of ventilatory response [end-tidal carbon dioxide (EtCO(2)), respiratory rate, pulse oximetry].

METHODS

The authors performed continuous capnography on a convenience sample of 20 ED pediatric patients who received ketamine 1.5 mg/kg IV for procedural sedation.

RESULTS

Continuous EtCO(2) and pulse oximetry remained essentially unchanged following ketamine injection, and no EtCO(2) levels > 47 mm Hg were noted at any point throughout sedation.

CONCLUSIONS

No hypoventilation was observed in 20 ED pediatric patients receiving ketamine 1.5 mg/kg administered IV over 1 minute. The authors found no evidence of respiratory depressant properties for this dissociative agent.

Postoperative pain relief after hepatic resection in cirrhotic patients: the efficacy of a single small dose of ketamine plus morphine epidurally

In cirrhotic patients undergoing hepatic surgery, postoperative analgesia remains a challenge. In this study, we evaluated the efficacy of a single dose of morphine combined with small-dose ketamine given epidurally for postoperative pain relief. One-hundred-four classification "Child A" cirrhotic patients were randomly assigned to two groups: 1) (MKG, n = 54): epidural morphine (3.5-5 mg) plus ketamine (20/30 mg); and 2) epidural morphine (3.5/5 mg) (MG, n = 50). The level of analgesia, side effects, psychomimetic and neurological disorders, additional analgesic needs, and overall quality of the analgesia were recorded. The mean duration of analgesia was longer in the MKG group (27.2 +/- 8 h versus 16.4 +/- 10 h; P < 0.05). In the MKG group, the visual analog scale (VAS) score began to be significantly lower from 14 h at rest and 12 h on coughing until the end of the study. The need for additional analgesia was also smaller in the MKG group (P < 0.05): at 24 h, only 10% of patients in the MKG group needed complementary analgesia, whereas in the MG group it was 100% (P = 0.003). Side effects were similar in both groups. Psychomimetic side effects and neurological disorders were not detected. These results suggest that postoperative analgesia provided by a single dose of epidural morphine with small-dose ketamine is effective in cirrhotic Child's A patients having major upper abdominal surgery.

Chemical restraint of peccaries with tiletamine/zolazepam and xylazine or tiletamine/zolazepam and butorphanol

OBJECTIVE

To evaluate the use of a combination of tiletamine/zolazepam and xylazine (TZX) in collared and white-lipped peccaries and to compare its efficacy as an anesthetic technique with that of tiletamine/zolazepam and butorphanol (TZB).

STUDY DESIGN

Prospective experimental trial.

ANIMALS

Seven white-lipped peccaries (Tayassu pecari) (four females and three males) and four collared peccaries (Tayasu tajacu) (two males and two females).

METHODS

Animal immobilization was attempted with TZX and TZB (IM) on two different occasions. Heart and respiratory rates (HR, RR), rectal temperature (RT), sedation, muscle relaxation, posture, auditory response and analgesia were evaluated every 15 minutes during immobilization. Induction, anesthesia, standing and walking time were determined after drug administration.

RESULTS

Doses for white-lipped peccaries were 1.23 +/- 0.26 mg kg(-1) (mean +/- SD) of TZ and 1.23 +/- 0.26 mg kg(-1) of X, and 1.46 +/- 0.09 mg kg(-1) of TZ and 0.14 +/- 0.008 mg kg(-1) of B; doses for collared peccaries were 1.51 +/- 0.29 mg kg(-1) of TZ and 1.51 +/- 0.29 mg kg(-1) of X and 1.68 +/- 0.02 mg kg(-1) of TZ and 0.17 +/- 0.002 mg kg(-1) of B. In white-lipped peccaries, both drug combinations provided a smooth induction and good immobilization for more than an hour. Anesthesia and standing times were significantly longer in animals given TZB, whereas walking time was significantly longer in animals given TZX. A significant decrease in HR was observed with both treatments. Respiratory rate decreased significantly with TZX, but the rate remained higher than with TZB. Induction and recovery quality in white-lipped peccaries was better with TZB than with TZX. Neither protocol provided adequate immobilization in collared peccaries.

CONCLUSION AND CLINICAL RELEVANCE

At the doses described, TZB is effective in providing a long period of immobilization, whereas TZX is adequate for short to medium immobilization in white-lipped peccaries. Neither drug combination was effective in collared peccaries at the doses given.

Analgesic and systemic effects of ketamine, xylazine, and lidocaine after subarachnoid administration in goats

OBJECTIVE

To determine the effects of ketamine hydrochloride, xylazine hydrochloride, and lidocaine hydrochloride after subarachnoid administration in goats.

ANIMALS

6 healthy goats.

PROCEDURE

In each goat, ketamine (3 mg/kg), xylazine (0.1 mg/kg), lidocaine (2.5 mg/kg), and saline (0.9% NaCI) solution were injected into the subarachnoid space between the last lumbar vertebra and first sacral vertebra (time 0). Analgesic, ataxic, sedative, cardiovascular, and respiratory effects and rectal temperature were evaluated before (baseline) and 2, 5, 10, 15, and 30 minutes after administration and at 30-minute intervals thereafter as needed.

RESULTS

Administration of anesthetics induced varying degrees of analgesia. Onset of the analgesic effect was more delayed for xylazine (mean +/- SD, 9.5 +/- 2.6 minutes) than for ketamine (6.7 +/- 2.6 minutes) or lidocaine (3.5 +/- 1.2 minutes). Duration of analgesia induced by xylazine (88.3 +/- 15 minutes) was twice as long as the duration of analgesia induced by ketamine (48.8 +/- 13.5 minutes) but similar to that induced by lidocaine (66.5 +/- 31 minutes). Xylazine induced bradycardia, whereas ketamine caused a nonsignificant increase in heart rate. Xylazine induced a reduction in arterial pressure, whereas ketamine or lidocaine did not affect arterial pressure.

CONCLUSIONS AND CLINICAL RELEVANCE

Subarachnoid administration of xylazine in goats resulted in longer duration of analgesia of the tail, perineum, hind limbs, flanks, and caudodorsal rib areas than administration of ketamine or lidocaine. However, xylazine caused bradycardia and respiratory depression. Additional studies are needed to determine whether the analgesia would be sufficient to allow clinicians to perform surgical procedures.