Auditory steady-state response, upper facial EMG, EEG and heart rate as predictors of movement during isoflurane-nitrous oxide anaesthesia

We have studied the relationship between patient movement andchanges in the auditory steady-state evoked potential, upperfacial muscle electromyogram (FEMG), electroencephalographic-zerocrossing frequency (EEG–ZCF) and heart rate during emergencefrom anaesthesia. Twelve healthy patients underwent surgeryduring stable isoflurane-nitrous oxide-oxygen anaesthesia withoutneuromuscular block. After skin closure, anaesthesia was discontinuedabruptly while mechanical ventilation was continued until thepatient moved. The magnitude of change in each physiologicalsignal was evaluated in decibels (dB). Both the auditory steadystate evoked potential and FEMG showed significant increasesin amplitude during the last 5-min period before movement (6.1and 10.7 dB, respectively). EEG-ZCF increased rapidly afteranaesthesia was discontinued (2.5 dB) but there was no furtherincrease in activity before movement. Heart rate did not changebefore movement. The use of the decibel transformation offersa promising method of displaying and interpreting changes inphysiological variables during anaesthesia.     

Stimulation of Thrombocytopoiesis in Irradiated Mice

Platelet depletion in mice, by injection of heterologous anti-platelet serum(APS), resulted in apparent stimulation of megakaryocytopoiesis as evidencedby a subsequent over-compensation of the level of circulating platelets. Injection of APS immediately before or after exposure to sublethal radiation or aday after exposure appeared to modify the response to radiation. Radiation-induced thrombocytopenia was neither as severe nor as prolonged in animalsso treated as in irradiated controls. More chronic thrombocytopenia at thetime of irradiation, however, appeared to increase the radiosensitivity of themegakaryocytic system.

Submitted on June 18, 1969 Accepted on January 13, 1970     

Megakaryocytopoiesis in the Rat

Labeling of rat megakaryocytes was observed after a single intravenousinjection of tritiated thymidine, and the following conclusions were made.

1. Morphologic appearance of megakaryocytes corresponded to their stageof maturation.

2. Only the youngest recognizable megakaryocytes (stage I) appeared tohave a DNA synthetic period.

3. Megakaryocytes did not undergo permanent cellular division.

4. There was probably some degree of ineffective megakaryocytopoiesis.

5. The average total maturation time of rat megakaryocytes was estimatedto be 43-75 hours wih 8-14 hours in stage I, 11-19 hours in stage II, and24-42 hours in stage III.

6. There was continuous influx into the megakaryocyte compartment froma precursor compartment. The immediate precursor cell was morphologicallyunrecognizable, but it appeared to have a generation time of 16 hours, aDNA synthesis period of 10 hours and a post-synthetic maturation timeof 2 hours.

7. Reutilization of tritium probably accounted for maintenance of a highdegree of labeling of megakaryocytes for a period of 1.5-4 days.

Submitted on August 7, 1964 Accepted on November 22, 1964     

Valproic acid-induced hyperammonemia in mentally retarded adults

All individuals receiving valproic acid therapy in an institution for the mentally retarded were evaluated for hyperammonemia. Of these 19 adults, 6 had persistent and 5 others had intermittent hyperammonemia. The hyperammonemic patients were asymptomatic, except that 2 had occasional lethargy. Hyperammonemia was detected more often in younger adults and in those treated with multiple anticonvulsants, especially phenytoin. Valproate-induced hyperammonemia is probably the result of depletion of mitochondrial acetyl CoA and decreased production of N-acetylglutamate, the obligatory activator of the first enzyme of the urea cycle, carbamyl phosphate synthetase I. Anticonvulsant-mediated microsomal enzyme induction may also contribute.