One hundred consecutive reports of reactions to intravenous anaesthetics Althesin, thiopentone and Epontol are reviewed and analysed. Ten reactions are attributed to causes other than the anaesthetic drug, and four are believed to have been caused by the muscle relaxant employed. The remaining 86 reactions were grouped according to their clinical presentation: histaminoid reactions ( 19), histaminoid with bronchospasm (33), bronchospasm (12), cardiovascular collapse (uu), delayed histaminoid reactions (6), and clonic contractions (5). None of the first four reaction types was associated with only one anaesthetic. A knowledge of the sales of Althesin has allowed the incidence of reactions to be estimated as between one in 11,000 and one in 19,000.

In this paper, we investigate the potential of a novel precoder for a massive multiple-input multiple-output (MIMO) system with multiple-antenna users under the influence of both Rayleigh and keyhole channel models. The proposed precoder is based on maximum-ratio processing and aims to enhance the channel hardening effect at the users. This is achieved through dividing each channel vector by its norm square. Closedform expressions for the achievable spectral efficiency of the conventional and proposed precoders are derived. If modeled with Rayleigh fading, due to the physical hardening property of this channel, a moderate gain in performance is produced by the proposed precoding method, where the highest spectral efficiency gain occurs for a small number of users and user antennas. Under Rayleigh fading, the results also demonstrate that similar performance is returned by increasing the users or user antennas. By comparison, the proposed precoder is shown to produce significant performance gains in the keyhole channels under the condition that the system is limited to singleantenna users. Corresponding to this, the results showcase how the performance of massive MIMO under keyhole channels is heavily dependent on increasing the number of served users over user antennas.

In this paper, we analyze and compare the performance of conventional maximum-ratio (MR) precoding to a proposed alternative scheme, when applied to a massive multiple-input multiple-output (MIMO) system with multiple-antenna users. In the proposed MR precoding scheme, each channel vector is divided by its norm square to increase the degree of hardening of the effective channel gains at the users. We derive closed-form expressions for the achievable spectral efficiency (SE) of both the conventional and proposed precoding schemes. These closed-form expressions are very simple and useful for further system design. For instance, for both precoding schemes, our results justify the motivation for additional user antennas since significant performance improvements are observed. The proposed scheme produces greater performance when compared to the conventional one across a range of system setups. More specifically, the proposed scheme is most effective in systems where the numbers of users and user antennas are kept small.

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