[Right ventricular function: physiological and physiopathological features]. / Fonction ventriculaire droite: bases physiologiques et physiopathologiques.

Sinus and conus constitute the two cavities of the right ventricle. They are anatomically and functionally different. The sinus is a flow-generator and the conus a pressure-regulator. The coronary circulation of the right ventricle is provided by the right coronary artery and the left anterior descending artery. The right ventricle is perfused during systole and diastole. When oxygen demand increases, coronary arteries dilate and oxygen extraction rises. As for the left ventricle, right ventricular performance depends upon heart rate, rhythm, contractility and loading conditions. Ventricular interactions are very important for right ventricular function. Loading conditions and contractility of the left ventricle are of major significance for right ventricular performance. For the right ventricle, the end of the ejection is different from the end of the active contraction. The time between them allows to achieve ventricular emptying. This duration is linked to afterload. Presently, it is impossible to accurately and simply assess these conditions. Pressure and volume overloadings result in right ventricular failure. They are responsible for ventricular dilation and ischaemia with a decrease in cardiac output, generating a vicious circle. Treatment includes the removal of the cause, and the maintenance of systemic arterial pressure and biventricular contractility. It is difficult to assess the effects of intravenous vasodilators on right ventricular afterload.

Mycoplasma pneumoniae pneumonia following assisted ventilation.

BACKGROUND: Mycoplasma pneumoniae pneumonia is regarded as a community-acquired pneumonia, rarely requiring hospitalization, with sporadic cases or limited outbreaks occurring after close contacts with an infected patient. Few reports mention M pneumoniae pneumonia acquired during hospitalization. PATIENTS AND METHODS: M pneumoniae was diagnosed in patients who developed pneumonia following perioperative and postoperative assisted ventilation by the isolation of M pneumoniae from bronchial washing, the detection of M pneumoniae DNA from bronchial washing, and serologic testing for the presence of specific immunoglobulin M (IgM) antibodies. RESULTS: Four patients were diagnosed as having M pneumoniae pneumonia following mechanical ventilation over a 1 1/2-year period. They were men, older than 50 years, and were hospitalized for vascular surgery. They developed febrile hypoxemia and intersticial pneumonia. Isolation of M pneumoniae and detection of M pneumoniae DNA were positive in 1 case; specific IgM antibodies were present in 4 cases. CONCLUSIONS: These observations allow the description of a new clinical entity and highlight the role of M pneumoniae as an agent of nosocomial infections. This diagnosis should be considered in any patient with precocious post-assisted ventilation febrile hypoxemia and diffuse interstitial pneumonia, and empiric treatment protocols may include M pneumoniae in their spectrum.

[A cause of difficult weaning from artificial respiration: polyneuropathy of intensive care]. / Une cause de difficulté de sevrage de la ventilation artificielle: la polyneuropathie de réanimation.

Three cases of Critically Illness Polyneuropathy (CIP) are reported. The difficulty of weaning the patients from the ventilator, whereas sepsis and MOF had been successfully treated, was the main feature in the three cases. The diagnosis was established by eletromyogram, showing a primary axonal denervation of peripheral nerve fibres, which was confirmed by a pathological study in one patient.

[Diprivan: evaluation of the depth of anesthesia]. / Diprivan: évaluation de la profondeur de l'anesthésie.

In daily practice, assessing the exact depth of anaesthesia relies even today on clinical signs such as movements elicited by painful stimuli and/or changes in blood pressure and heart rate. Neurophysiological indicators, such as EEG and evoked potentials, are most probably techniques of the future. They are not yet in routine medical practice, because of the complexity of the information supplied, unresolved technical problems and the high cost of equipment. Nevertheless, these techniques are gradually entering the operating theatre and contribute to the monitoring of the anaesthetized patient. EEG, in particular, regardless of the method of analysis used, seems effective and reliable during the induction phase of anaesthesia, However, the most adequate method of monitoring the maintenance phase or detecting awareness during anaesthesia remains to be produced.

[Computer-assisted intravenous anesthesia: value, method and use]. / Anesthésie intraveineuse assistée par ordinateur: intérêt, méthode et application.

Total intravenous anaesthesia (TIVA) is becoming increasingly popular among anaesthetists. It has several advantages, namely each component of the anaesthetic protocol can be independently controlled, and the operating room remains unpolluted with nitrous oxide or volatile anaesthetic agents. TIVA aims to maintain a constant blood concentration of each anaesthetic agent. This means that infusion rates need to be repeatedly altered. A computer calculates theoretical blood concentrations of agent according to a pharmacokinetic model, and drives an infusion device. Only a few programmes have been developed by research teams. No commercial device is available as yet. However, there are several syringe pumps and volumetric pumps which are accurate enough for use in TIVA and which may be controlled by computer. Clinical studies have shown the benefits of TIVA: greater haemodynamic stability, decreased drug consumption, more rapid recovery, and a lesser need for postoperative ventilatory support. The most appropriate agents are propofol and etomidate as hypnotics, alfentanil and sufentanil for opioids, vecuronium and atracurium as muscle relaxants. Etomidate is not recommended for prolonged infusions, because of the risk of adrenocortical suppression. TIVA seems to be attractive for neurosurgery, thoracic surgery, day case surgery, endoscopic procedures, and anaesthesia in remote locations. Unfortunately, it is an expensive technique. Moreover, there is considerable interpatient variability of the drug concentration required for a same clinical effect. Two methods are proposed to decrease this variability: population pharmacokinetic models and Bayesian forecasting. Closed loop systems are still research tools. It is concluded that computer-driven anaesthesia is the equivalent to the vaporizer for volatile agents. However, further clinical studies are needed to determine whether the advantages of this technique outweigh its disadvantages.

Pharmacodynamic properties of propofol during recovery from anaesthesia.

Propofol was used to induce and maintain anaesthesia in 20 healthy adult ASA physical status 1 patients undergoing dental surgery. Recovery was studied using psychometric tests and clinical assessment while propofol blood levels were obtained at the same study times. Recovery was rapid and there were no significant differences 60 min after anaesthesia (t60) for the tracing test and 90 min for the choice reaction time. All patients were orientated in time at t30 and in space at t45; Stewart's score was maximal in all patients at t60; recovery of normal walking was slower, i.e. t120. Return to baseline for psychometric function was linked to a decrease in propofol blood level, for both the tracing test (P less than 10(-6)) and the choice reaction time (P less than 10(-3)). We conclude that propofol is a suitable anaesthetic agent for induction and maintenance of short duration dental anaesthesia.

Propofol as the main anaesthetic agent in dental surgery.

Propofol was used as the main anaesthetic agent for induction and maintenance of anaesthesia in 30 patients undergoing dental surgery requiring tracheal intubation. Anaesthesia was successfully induced and intubation performed in all patients, with a propofol induction dose of 3.5 mg/kg and without muscle relaxants or opioids. Intubating conditions were good for 77% of the patients. No haemodynamic changes occurred. Maintenance with propofol 9 mg/kg/h and 70% nitrous oxide provided suitable conditions for surgery. Awakening and recovery times were short and few side effects were recorded. However, post-operative dental pain was systematically recorded and was present in 60% of the patients.