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Copyright of Canadian Journal of Anaesthesia / Journal Canadien d'Anesthésie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The coronavirus replicase-transcriptase complex is an assembly of viral and cellular proteins that mediate the synthesis of genome and subgenome-sized mRNAs in the virus-infected cell. Here, we report a genetic and functional analysis of 19 temperature-sensitive (ts) mutants of Murine hepatitis virus MHV-A59 that are unable to synthesize viral RNA when the infection is initiated and maintained at the non-permissive temperature. Both classical and biochemical complementation analysis leads us to predict that the majority of MHV-A59 ORF1a replicase gene products (non-structural proteins nsp1-nsp11) form a single complementation group (cistron1) while the replicase gene products encoded in ORF1b (non-structural proteins nsp12-nsp16) are able to function in trans and comprise at least three, and possibly five, further complementation groups (cistrons II-VI). Also, we have identified mutations in the non-structural proteins nsp 4, nsp5, nsp10, nsp12, nsp14, and nsp16 that are responsible for the ts phenotype of eight MHV-A59 mutants, which allows us to conclude that these proteins are essential for the assembly of a functional replicase-transcriptase complex. Finally, our analysis of viral RNA synthesis in ts mutant virus-infected cells allows us to discriminate three phenotypes with regard to the inability of specific mutants to synthesize viral RNA at the non-permissive temperature. Mutant LA ts6 appeared to be defective in continuing negative-strand synthesis, mutant Alb ts16 appeared to form negative strands but these were not utilized for positive-strand RNA synthesis, and mutant Alb ts22 was defective in the elongation of both positive- and negative-strand RNA. On the basis of these results, we propose a model that describes a pathway for viral RNA synthesis in MHV-A59-infected cells. Further biochemical analysis of these mutants should allow us to identify intermediates in this pathway and elucidate the precise function(s) of the viral replicase proteins involved.

Maternal cortical vein thrombosis is a potentially fatal complication of pregnancy and the puerperium. Patients may present with focal neurologic deficits, seizures, or symptoms indicating increased intracranial pressure. Associated conditions include maternal dehydration and preeclampsia or frank eclampsia. Parturients may require anesthesia for various types of delivery. Safe administration of appropriate anesthesia must take into account the possible presence of a coagulopathy or reduced intracranial compliance. Case presentations, a literature review, possible pathogenetic mechanisms, and specific anesthetic considerations are discussed to enable the obstetric anesthesiologist to develop a rational plan of management.

Several occurrences of pulmonary edema following relief of acute upper airway obstruction have been reported. The edema is associated with normal cardiac filling pressures and responds promptly to conservative therapy. Its origin may be attributed to the cardiopulmonary effects of the vigorous inspiratory effort that the spontaneously breathing patient generates to overcome respiratory obstruction (the Müller maneuver). A patient with postobstruction pulmonary edema complicated by hypovolemia and myocardial infarction is described. Prompt invasive hemodynamic monitoring in selected high-risk patients is suggested.

The case of a pregnant patient with diffuse scleroderma who died following Caesarean section under general anaesthesia is presented. The patient's postoperative course was complicated by pulmonary oedema and pulmonary hypertension, sepsis, thrombocytopenia and renal failure. Aspects of the disease which possess anaesthetic implications are reviewed.

Regional anaesthesia is a suitable technique for the management of the asthmatic parturient. We report the case of an asthmatic gravida in labour in whom prompt institution of bupivacaine-fentanyl epidural analgesia was associated with enhancement of the effectiveness of concurrent medical therapy for bronchospasm. Prior to the initiation of epidural blockade, inhaled atropine was employed in an effort to reduce parasympathetic tone in the bronchial smooth muscle. Sustained clinical improvement did not occur until after delivery of the fetus and placenta.