A magnetic resonance spectroscopic imaging study of adult nonhuman primates exposed to early-life stressors

BACKGROUND

Long-term behavioral, immunologic, and neurochemical alterations have been found in primates exposed to adverse early rearing.

METHODS

Bonnet macaque (Macaca radiata) mother-infant dyads were exposed to uncertain requirements for food procurement (variable foraging demand, VFD) for a few months. Ten years later, these offspring and age- and gender-matched control subjects were studied using proton magnetic resonance spectroscopic imaging (MRSI).

RESULTS

In anterior cingulate, VFD-reared subjects displayed significantly decreased N-acetylaspartate (NAA) resonance and significantly increased glutamate-glutamine-gamma-aminobutyric acid (Glx) resonance relative to the stable neurometabolite creatine (Cr). Across all subjects, NAA/Cr and Glx/Cr ratios in the anterior cingulate were negatively correlated (r = -.638, p =.014). In the medial temporal lobe, the ratio of choline-containing compounds to Cr was significantly increased in VFD subjects.

CONCLUSIONS

These findings indicate that adverse early rearing in primates has an enduring impact on adult MRSI measures considered reflective of neuronal integrity and metabolism, membrane structure and glial function, and cerebral glutamate content, and that these alterations occur in the same brain regions implicated in trauma-related psychiatric disorders.

Anaesthesia of the common marmoset (Callithrix jacchus) using continuous intravenous infusion of alphaxalone/alphadalone

A safe means of anaesthetizing common marmosets (Callithrix jacchus) for a study using magnetic resonance imaging (MRI) to investigate cerebral ischaemia was required. Continuous infusion of alphaxalone/alphadalone was used to anaesthetize 37 marmosets for non-recovery and recovery experiments. This was found to give safe, reliable anaesthesia when coupled with pulse oximetry and electrocardiographic (ECG) monitoring.

Effects of inhalation and intravenous anesthetic agents on pressor response to NG-nitro-L-arginine

The effects of anaesthetic agents on pressor effect of NG-nitro-L-arginine (L-NNA), a potent inhibitor of nitric oxide (NO) synthesis, were examined in rats. I.v. bolus of L-NNA (1-32 mg/kg) in conscious rats dose dependently increased mean arterial pressure (MAP) to a maximum value of 53 +/- 2 mmHg at 16 mg/kg with ED50 value of 4.7 +/- 0.9 mg/kg. The effects of a single i.v. bolus dose (32 mg/kg) of L-NNA were examined in conscious rats and rats anaesthetised with pentobarbital, chloralose, ketamine, althesin (mixture of alphaxalone and alphadolone), urethane, enflurane or halothane. In conscious rats, peak MAP (51 +/- 3 mmHg) was reached 10 min after i.v. injection and the effect lasted more than two hours. The magnitudes of peak MAP differed under the influence of anaesthetic agents with the following rank order: althesin greater than conscious = pentobarbital = chloralose = ketamine = urethane greater than enflurane much greater than halothane (in which there was negligible change in MAP). The onsets were delayed in rats anaesthetised with pentobarbital, althesin, chloralose and enflurane but not altered with ketamine and urethane compared to that in conscious rats. Therefore, L-NNA caused intense and prolonged pressor response in conscious rats and rats anaesthetised with the i.v. anaesthetic agents pentobarbital, chloralose, ketamine, althesin and urethane. MAP effect of L-NNA was markedly attenuated by the inhalation anaesthetics halothane and enflurane.

Continuous EEG and ICP monitoring as a guide to the administration of althesin sedation in severe head injury

The effects of 142 intravenous boluses of althesin (0.05 ml/kg) on cerebral perfusion pressure (CPP) were studied in twelve head injured comatose patients. The data were divided into those where the mean pre-bolus intracranial pressure (ICP) was above or below 20 mmHg and then subdivided into those where the minimum pre-bolus voltage of the cerebral function monitor (CFM) was above or below 5 microV (representing marked reduction in cortical electrical activity). The pre-bolus ICP influenced the extent of the fall in ICP and thus the direction of the resulting change in CPP. A mean reduction in CPP was observed in both groups in which ICP was below 20 mmHg irrespective of the CFM voltage. In the subgroups with high ICP, CPP increased when CFM was not depressed and fell when CFM was below 5 microV. The effects of individual boluses varied within and between the subgroups and, occasionally, severe and unpredictable hypotension occurred. If althesin administration had been restricted to the high CFM and high ICP group, 90% of the episodes of reduced CPP would have been avoided. In fact, when cortical electrical activity is already severely depressed, further administration of hypnotic anaesthetic agents produces only small reductions in ICP and usually a fall in CPP. These findings suggest that the minimum voltage of the CFM trace is a clinically useful guide to the administration of intravenous anaesthetic agents and offers a relevant prediction of their effects on CPP.

Some predisposing factors to hypersensitivity reactions following first exposure to Althesin

Three possible factors predisposing to Althesin hypersensitivity, namely total dose, method of administration, either by bolus dose or infusion, and pregnancy have been studied in patients receiving the drug for the first time. Of 137 patients given Althesin, four exhibited clinical signs of mild hypersensitivity, while C3 conversion alone, indicative of a subclinical reaction, was seen in a further six patients. No reactions were observed in two control groups in whom anaesthesia was induced with thiopentone. Neither the total dose nor method of administration appeared consistently to influence the incidence of reactions, but eight of the ten patients producing an altered response to Althesin were pregnant.

Use of a continuous infusion of althesin in neuroanaesthesia. Changes in cerebral blood flow, cerebral metabolism, the EEG and plasma alphaxalone concentration

Ten patients with small supratentorial tumours were studied during craniotomy. Cerebral blood flow (CBF) was measured in the contralateral hemisphere by a modification of the Kety and Schmidt technique using xenon-133 i.v. With an Althesin infusion rate of 0.2 ml kg-1 h-1, CBF was 24.4 +/- 5.4 ml min-1/100 g and CMRO2 1.87 +/- 0.44 ml min-1/100 g at PaCO2 4.1 +/- 0.7 kPa (mean +/- SD). During constant infusion rates of Althesin, steady values of CMRO2 were obtained, while an increase in infusion rate of 150% was associated with an increase in plasma alphaxalone concentration, a decrease in CMRO2 and a tendency of further EEG suppression. However, great inter- and intraindividual variations were present, and correlations between CMRO2, EEG activity and plasma alphaxalone concentration were weak.

[Anesthetic induction with Althesin or diazepam in patients undergoing an aortocoronary bypass]

The haemodynamic effects of induction of anaesthesia with diazepam (group D) and Althesin (group A) were studied in 25 coronary patients under betablockers with good myocardial function. Haemodynamic variables monitored were vascular pressures, cardiac output and systolic time intervals. The effects of both drugs were observed when used alone (time I) and in combination with fentanyl, pancuronium and nitrous oxide (time II). The results seemed to show that Althesin (12.51% fall in SI and 10.79% increase in PEP/LVET) depressed myocardial function more than diazepam (no significant difference), but the introduction of fentanyl, pancuronium and nitrous oxide removed the differences between the drugs as to their effect on myocardial performance. These drugs added a depressant effect to diazepam (13.83% fall in SI and 15.77% increase in PEP/LVET) without increasing Althesin's negative inotropic effect. However, in group A at time II, the pulmonary arterial pressure, the wedge pressure and the pulmonary vascular resistance were significantly reduced, while they remained stable in the diazepam group.

[Blood histamine level and anaphylactic reaction under alphadione]

Histamine release is generally thought to play a major role in anaesthetic-induced anaphylactoid reactions. In 12 patients who were developing such a reaction at the start of a slow rate intra-venous infusion of alphadione, serum histamine was measured using the enzyme-isotopic assay from a blood sample drawn within the first 5 minutes following the onset of clinical signs. Histaminemia above normal value was noted in 3 patients only without clear clinical correlation. These results would suggest that histamine release is unlikely to be principally involved in this kind of adverse reaction.

Age influences the minimum infusion rate (ED50) for continuous infusions of Althesin and methohexitone

The influence of age has been studied on equipotent rates of continuous infusions of two intravenous hypnotic agents. Two end points have been defined; ED50: the rate needed to suppress the initial response to the surgical incision in 50% of patients, and ED95: the corresponding rate in 95% of patients receiving continuous infusion anaesthesia to supplement 67% nitrous oxide in oxygen. All 210 patients included in the study were premedicated with morphine 0.15 mg kg-1. For patients aged 20-40 years (young group), the ED50 values for Althesin (as alphaxalone) and methohexitone were 14.6 micrograms kg-1 min-1 and 59.9 micrograms kg-1 min-1. The ED95 values were 21.0 micrograms kg-1 min-1 and 92.1 micrograms kg-1 min-1. For patients aged 55-80 years (old group), the ED50 values for Althesin and methohexitone were 11.0 micrograms kg-1 min-1 and 44.2 micrograms kg-1 m in-1, while the corresponding ED95 values were 16.4 micrograms kg-1 min-1 and 76.2 micrograms kg-1 min-1.

Anaesthesia for transcervical thymectomy in myasthenia gravis

A modified technique of total intravenous anaesthesia was used in the management of 22 patients with myasthenia gravis of varying severity undergoing therapeutic transcervical thymectomy. The relatively short-acting intravenous hypnotics, Althesin and etomidate were compared for induction of anaesthesia and for maintenance as a supplement to 50% nitrous oxide in oxygen. Moderately high doses (20 or 25 micrograms/kg) of the potent, synthetic opiate, fentanyl provided analgesia and a level of respiratory depression sufficient to facilitate control of respiration. The induction of anaesthesia was rapid and smooth, completed in under 5 minutes. Reflex response to surgical stimulation was suppressed for extremely variable periods. Complete recovery of consiousness, or adequate spontaneous respiration and of muscle tone was readily achieved, but was more rapid after Althesin (p less than 0.05). Postoperative problems were few. It is suggested that this technique of anaesthesia can provide optimum operating conditions with rapid, complete recovery and consequently low morbidity; the primary requirements of anaesthesia for therapeutic thymectomy.

Hypoxic ventilatory drive in the dog under Althesin anaesthesia

Althesin was administered i.v. to eight dogs, using two different rates of infusion (6.55 +/- 2.13 microliter kg-1 min and 12.80 +/- 2.00 microliter kg-1 min). Ventilation (TI, TE, RR, TI/Ttot, VT, VE, VT/TI) and arterial blood-gas tensions were measured in air and during a 10-min period of 100% oxygen breathing. For both rates of Althesin infusion the ventilatory response to oxygen was identical: there was significant depression of ventilation (decrease in VE and of the ventilatory drive, VT/TI) from the 1st min of inhalation lasting up to the 10th min. This decrease in ventilation was more marked and persistent than the decrease noticed in the unanaesthetized dog. We conclude that the hypoxic ventilatory drive persists in the dog under Althesin anaesthesia.

Dose-response relationships for infusions of Althesin or methohexitone

A technique is described for the determination of equipotent rates of infusion of intravenous hypnotic agents. Two end points have been defined; the rates needed to suppress the initial response to the surgical incision in 50% (ED50) and 95% (ED95) of patients receiving continuous infusion anaesthesia to supplement 67% nitrous oxide in oxygen. For patients aged 20-60 years, and premedicated with morphine 0.15 mg/kg intramuscularly, the ED50 values for Althesin (as alphaxalone) and methohexitone by infusion were 13.7 and 48.8 micrograms/kg/minute respectively. The ED95 values were 18.1 and 75.9 micrograms/kg/minute. For patients of a similar age premedicated with diazepam 10 mg orally, the ED50 values for Althesin and methohexitone were 18.5 and 66.0 micrograms/kg/minute respectively; while the ED95 values were 24.2 and 80.8 micrograms/kg/minute.

Does obesity affect recovery? A study using intravenous methohexitone and Althesin for short procedures

One hundred and twenty unpremedicated patients, scheduled for minor gynaecological procedures, were randomly allocated to receive Althesin or methohexitone to supplement N2O and O2 anaesthesia. Patients were assessed as thin, medium or fat according to the degree of obesity as measured by skinfold calipers. The range of mean times for the patients to open their eyes was 3.1-4.0 minutes, to be orientated was 4.4-6.7 minutes and to perform a manipulative test was 27.7-32.1 minutes. No statistically significant differences were seen in these indices of recovery whether they received Althesin or methohexitone or whether they were thin, medium or fat. A paper and pencil test was also performed. Induction doses of the intravenous agent were calculated on a body weight basis and increments given only in response to movement. The mean total dose of Althesin was decreased from 1.33 mg total steroid/kg for thin patients to 1.06 mg total steroid/kg for fat patients (p less than 0.01). The mean total dose of methohexitone was decreased from 3.4 mg/kg for thin patients to 2.9 mg/kg for fat patients which was not significant.

Baroreflex effects of althesin infusions to supplement nitrous oxide anaesthesia in man

The effects on baroreflex control of heart rate, of two infusion rates of Althesin (18 and 36 micrograms kg-1 min-1 as total steroid) to supplement 66% nitrous oxide in oxygen anaesthesia, have been studied in six younger (mean age 35.5 yr) and six older (mean age 61.0 yr) patients. Steady-state anaesthesia at both infusion rates was associated with diminished baroreflex sensitivity and resetting of the reflex to allow lower arterial pressures to be maintained without tachycardia.

Continuous intravenous anaesthesia with Althesin for resection of tracheal stenosis

The anaesthetic management of patients undergoing tracheal resection for tracheal stenosis and the advantage of the maintenance of spontaneous respiration without intubation of the distal tracheal segment is discussed. The case reports of two such patients using a continuous intravenous infusion of Althesin with maintenance of spontaneous respiration are presented. The technique expedited the surgical reanastomosis due to lack of instrumentation in the surgical field. While some mild respiratory depression as evidenced by carbon dioxide retention did occur, the technique is worthy of consideration for the procedure.

Althesin in the management of head injuries: a preliminary report

The aggressive treatment of major craniocerebral trauma has received recent attention. Barbiturate administration has been beneficial in some cases of sustained, uncontrolled intracranial hypertension. One major disadvantage of pentobarbital narcosis is the long half-life of the drug (15 to 48 hours). We have used Althesin, an intravenous steroid anesthetic (alfaxalone and alfadolone acetate; Glaxo Laboratories Ltd., Greenford, Middlesex, England), in eight seriously head-injured patients. Althesin combines the theoretical advantages of pentobarbital in the management of head trauma with almost immediate reversibility (serum half-life, 1.6 minutes). Raised intracranial pressure and clinical outcome seem to be influenced favorably and the side effects are negligible when the drug is administered by continuous intravenous infusion over several days. Further study of this compound in the management of head trauma seems warranted.

[Respiratory effects of increasing doses of alfathesin in the dog]

In 10 dogs the authors studied the effect of increasing doses of alfathesin on ventilation (VE, frequency, VT, blood gases), on the ventilatory pattern (TI, TE, TI/Ttot), on the neurological initiation of ventilation (VT/TI, occlusion pressure at 0.5 seconds), and on the Hering-Beurer reflex (duration of apnoea after occlusion of the airway at the end of inspiration). The results were compared with normal values taken from the literature. The correlation between the dose of alfathesin and the measured or calculated parameters was examined. Ventilation was stimulated by low doses of alfathesin, a stimulation, characterized by tachypnoea without change in tidal volume. Deepening of anaesthesia was accompanied by progressively increasing depression of respiration (diminution of VE, of frequency, of VT/TI and increase of PaCO2 and of the duration of apnoea). The mechanisms of the initial stimulation of ventilation and of respiratory depression are discussed. The authors conclude that the action of alfathesin on the central nervous system is biphasic, with stimulation during light anaesthesia followed by depression with associated depression of ventilation, despite increasing hypoxia and hypercapnia.

Sex difference in response to alphaxalone anaesthesia may be oestrogen dependent

The steroid anaesthetic Althesin (Glaxo), which is a mixture of two C21 steroids, alphaxalone (3 alpha-hydroxy-5 alpha-pregnane-11, 20-dione--the active compound) and alphadolone acetate (21-acetoxy-3 alpha-hydroxy-5 alpha-pregnane-11, 20-dione), has been especially useful for the study of forebrain-autonomic and neuroendocrine functions. As determined by the loss of the righting reflex, Child et al. found no sex difference in the anaesthetic dose of Althesin administered intravenously (i.v.). However, in our neuroendocrine studies in which the anaesthetic was administered intraperitoneally (i.p.) and at dosage sufficient to produce surgical anaesthesia and analgesia, we observed a sex difference in the efficacy of Althesin. This may explain the difficulties that have been encountered in obtaining adequate anaesthesia (blockade of the somatomotor response to pain) with Althesin. Here we report, using cortical electroencephalography, that Althesin is a more potent anaesthetic than either sodium pentobarbitone or urethane, and that anaesthesia in the male rat requires about four times more Althesin (administered i.p.) than in the female. This sex difference is age dependent, can be abolished by administering oestrogen to the male, does not depend on sexual differentiation of the brain, and cannot be attributed to a sex difference in the metabolic clearance rate of alphaxolone. These results, taken together with those of Richards and Hesketh, suggest that the effect of alphaxalone may be mediated by interactions with synaptic membranes that are more specific than simply a generalized change in membrane structure, and that these interactions are affected by sex steroids.

Comparison of the cerebral function monitor and plasma concentrations of thiopentone and alphaxalone during total i.v. anaesthesia with repeated bolus doses of thiopentone and althesin

Repeated bolus doses of thiopentone or Althesin were administered to 10 patients every 240 s while cerebral electrical activity was recorded with the Cerebral Function Monitor (CFM). Peripheral venous blood samples were collected at 60 and 225 s after each bolus dose for the measurement of plasma concentrations of the drugs. Significant correlations in the range r = 0.56-0.96 (P = 0.02-0.00001) between plasma thiopentone or alphaxalone concentrations and the upper and lower edges of the CFM trace were found. For the patients with relatively poor correlations, better correlations were obtained when 60- and 225-s sample were analysed separately.

A clinical neuropsychological study of the postoperative course after three types of anaesthesia

In a double-blind study, 57 patients were anaesthetized with either Althesin, thiopentone, or fentanyl combined with diazepam for cystoscopies. One and a half and four hours after the administration of anaesthesia, the patients were investigated with an objective neuropsychological method, continuous Reaction Time, and with a subjective rating scale. Beecher's Mood Scale. One week later the patients answered a questionnaire about side-effects experienced during the days following anaesthesia. At the 1 1/2 h investigation, the patients were cerebrally affected, both subjectively and objectively. The CNS-dysfunction was different for the three anaesthetics. After administration of thiopentone, the patients experienced the highest degree of subjective effects but had the smallest reaction time prolongation. Fentanyl-diazepam gave the least subjective effects, but the highest degree of cerebral affection in the reaction time measurements. The effects of Althesin were intermediate. Four hours after anaesthesia, the reaction time prolongations had disappeared, except for Althesin, and only patients who had thiopentone registered subjective effects. The number of side-effects was greatest and most prolonged following thiopentone. About 25% of the patients reported that side-effects had persisted more than 1 day after anaesthesia.

Althesin infusions for maintenance of anaesthesia

The intravenous anaesthetic Althesin may be administered by continuous intravenous infusion for maintenance of general anaesthesia, sedation in patients in intensive care units or during investigational procedures. Published reports of experience with this technique are reviewed, with particular attention to the rates of administration employed and the influence of other anaesthetics and analgesic agents used concurrently.

Continuous intravenous infusion of disoprofol (ICI 35868, Diprivan). Comparison with Althesin to cover surgery under local analgesia

Disoprofol has been used to induce and, by continuous infusion, to maintain a light level of general anaesthesia in 100 patients undergoing surgery with the aid of a regional block. Its effects have been compared with 100 patients anaesthetised in a similar manner with Althesin. Disoprofol proved to be a very satisfactory agent for use by this method and apart from an appreciable incidence of pain on injection the number of complications was small and comparable to those found with Althesin, which caused more involuntary movements. Recovery was particularly rapid and clear-headed following disoprofol, and occurred highly significantly more quickly than after Althesin. Disoprofol, however, will not be marketed in the present formulation which has Cremophor EL as the solubilising agent.

[The use of althesin in endoscopy]

Althesin was used on account of its pharmacokinetic and pharmacodynamic properties and its high therapeutic index in a search for a narcotic drug displaying minimal interference with metabolic and functional parameters in the aged. Continuous perfusion of the anaesthetic proved an extremely flexible method bearing in mind the varying length of the operations concerned. Stress is laid on the need for clinical control, especially at the moment of induction to ensure that timely action can be taken in the event of complications.

A study of the amygdaloid defence reaction showing the value of Althesin anaesthesia in studies of the functions of the fore-brain in cats

1. In cats under Althesin (alphaxalone-alphadalone) anaesthesia, sites in the amygdala and brain-stem defence areas have been electrically stimulated by means of monopolar, semi-microelectrodes. 2. Such stimulation evoked a consistent pattern of visceral changes characteristic of the alerting stage of the defence reaction as it has been described by previous workers. This "visceral alerting reaction" included increases in arterial blood pressure, heart-rate and cardiac output with vasoconstriction in kidney, intestines and skin but vasodilatation in the hind limbs. 3. These results differ strikingly from those reported previously n that, under conventional anaesthetics, such as chloralose or barbiturate, the full visceral alerting reaction cannot be evoked by amygdala stimulation, or any other manoeuvre which involves transmission through the brain stem defence areas. 4. The area of the amygdala from which such responses can be elicited under althesin closely resembles that which has been reported to evoke defence reactions in conscious animals. 5. It is concluded that Althesin, used in the manner described, does not distort synaptic transmission in the forebrain in the way that conventional anaesthetics do. It is suggested that this steroid anaesthetic may be invaluable in any studies of fore-brain physiology in the cat.