SummaryThe assessment of the depth of anaesthesia in man has received much attention in recent years, following a number of reports of people being aware during surgery. A range of different measures have been suggested for determining the adequacy of anaesthesia in man, but such a critical assessment is rarely applied to laboratory animals. This article describes the methods used to assess anaesthetic depth in both man and animals, and compares the relative states of knowledge about anaesthetic depth in animals and man.

SummaryThe effects of induction of anaesthesia with halothane or isoflurane were studied in rabbits. The anaesthetic agents were delivered either via a face-mask, or the animals were placed in an anaesthetic induction chamber. All rabbits had periods of apnoea during induction, lasting 30-120 s, resulting in moderate hypercapnia and acidosis. Periods of apnoea were associated with a marked bradycardia. The combination of bradycardia and hypercapnia during induction may represent an increased risk of anaesthetic associated mortality. Animals in all groups tried to avoid inhaling anaesthetic vapour, and this behaviour, together with the occurrence of breathholding suggests that induction was aversive.

SummaryThe results of a preliminary evaluation of etorphine/methotrimeprazine ['Small Animal Immobilon') and midazolam in rats and mice are reported, and this regimen is compared to fentanyl/fluanisone/midazolam in mice. In rats, a surgical plane of anaesthesia with good muscle relaxation was produced, but blood gas analysis showed the presence of severe hypoxia, hypercapnia and acidosis. In mice etorphine/methotrimeprazine/midazolam and fentanyllfluanisone/midazolam produced adequate anaesthesia, but blood gas analysis showed severe respiratory depression with both regimens. Since etorphine/methotrimeprazine/midazolam produced severe respiratory depression in rats and mice it is suggested that this regimen is used with caution. Administration of supplemental oxygen would seem advisable when using either etorphine/methotrimeprazine/midazolam or fentanyl/fluanisone/midazolam in rats and mice.

SummaryA safe means of anaesthetizing common marmosets (Callithrix iacchus) 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.

SummaryThe use of etorphine (a potent p.-opioid),methotrimeprazine (a phenothiazine tranquillizer) and midazolam (a benzodiazepine) in laboratory rabbits is described. The central ear artery was cannulated under local anaesthesia using lignocaine/prilocaine cream, enabling cardiovascular monitoring in conscious animals. Anaesthesia was characterized by respiratory arrest, profound analgesia and a stable cardiovascular system (after commencing intermittent positive pressure ventilation). Reversal of anaesthesia with buprenorphine [a partial Jt agonist) did not reduce the degree of post-operative respiratory depression, but shortened the period of unconsciousness considerably. This anaesthetic regimen can only be recommended for rabbits that are free of respiratory disease and if facilities for IPPV are available. Keywords

In April 1941 the patient was seen in the neuromedicai service. The impression at this time was that there was a disturbance of function in the pons and the cerebellum. However, roentgenograms of the skull failed to show evidence of tumor. On May 12, 1941 the patient still had dizziness and headache, although of less severity.

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whole story revolves on the idea that vertical nystagmus observed spontaneously in a patient is thought to be due to an intracranial lesion and that one hardly ever thinks of such nystagmus as being due to a peripheral lesion. Dr. Spiegel brings out by experimental means that such nystagmus can be produced by labyrinthine changes. He tries to prove this by puncturing the round windows of a cat. Vertical nystagmus of a type which changes with the position of the cat's head then developed. If the utricle is impaired, the activity of the vertical canals is thereby increased. In other words, lesions in the two labyrinths under certain circumstances will produce vertical nystagmus.He also injects into the middle ears a solution of cocaine and on permitting it to act by diffusion he observes certain reactions take place (although more slowly than after puncturing) in which there is vertical nystagmus, and this time the nystagmus is downward instead of upward.Dr. Spiegel concludes from these experiments that a bilateral peripheral lesion can produce vertical nystagmus.It is not often that one sees vertical nystagmus due to peripheral lesions. Dr. MacKenzie reported a case in which a focal infection produced vertical nystagmus, which disappeared following extraction of a tooth.