Should nitrous oxide be discontinued before desflurane after anaesthesia with desflurane/N2O?

Background : The appearance of hypoxaemia immediately after anaesthesia with nitrous oxide may be partially explained by diffusion hypoxia. This study was undertaken to evaluate circulatory and respiratory variables during emergence after desflurane/nitrous oxide anaesthesia, and whether there are any differences depending on which gas is discontinued first. Methods : 20 patients were studied after gynaecological laparoscopic surgery. The depth of anaesthesia was reduced 10 min prior to the emergence by stopping the administration of one of the two inhalational agents. Desflurane was discontinued first in Group 1, nitrous oxide in Group 2. Ventilation was controlled with E'C0₂ maintained at 5% until the administration of the second anaesthetic gas was discontinued. Thereafter, the patients breathed spontaneously. Results : The PaC0₂ at which the respiratory drive reappeared after controlled normoventilation was similar in both groups, 6.1–6.5 kPa, and extubation was performed after 10–11 min. At extubarion, the end–tidal C0₂ and total MAC were similar in the groups, about 6.2 vol% and 0.16, respectively. Mean arterial blood pressure was significantly higher in Group 1. The cardiac output increased in both groups from about 6 1/min at the conclusion of anaesthesia to 9.0 and 7.6 1/min at 15 min in the recovery period. End–tidal O₂ decreased and CO₂ increased in both groups during the first 10 min in the recovery period. pH was reduced at 15 and 30 min in both groups. Conclusion : Irrespective of which agent was discontinued first, there was an increase in cardiac output, decrease in oxygenation and a modest acidosis in the first 30–min recovery period. The only significant difference between the groups was in mean arterial blood pressure in the early emergence phase with a greater MAP when N₂O had been used until the conclusion of anaesthesia.     

Evaluation of an Educational Programme for Telephone Advisers in Primary Health Care

Marklund B, Silfverhielm B and Bengtsson C. Evaluation of aneducational programme for telephone advisers in primary healthcare. Family Practice 1989; 6: 263–267. Telephone advisers, usually registered nurses, have a very importantrole in the Swedish primary health care service. In order toimprove this service, a special educational programme has beenworked out for registered nurses working at a Swedish healthcentre. The purpose of this paper is to evaluate this educationalprogramme at one of the health centres. The quality of the telephoneadvice was evaluated by a blind observer. After the educationalprogramme the quality of advice was improved. Among the participatingnurses, the confidence and the satisfaction with the work increasedafter the educational programme.     

Effects of hyperventilation on the inspiratory to end-tidal oxygen difference

We assessed the inspiratory to end-tidal oxygen difference during voluntary hyperventilation in 10 healthy male volunteers.The oxygen difference was measured with a fast-response paramagneticdifferential oxygen sensor. As simultaneous changes in metabolismand cardiac output also influence oxygen uptake was measuredwith indirect calorimetry and noninvasive transthoracic electricalbioimpedance was used for measurement of cardiac output. Aftera rest period, subjects were instructed to double their minuteventilation volume (VE) and after 5 min triple their restingVE for another 5 min. decreased from a zero value of 6.4 kPato 3.9 kPa at 5min (P < 0.01) and 2.9kPa at 10min (P <0.01). At 15min (i.e. 5min after the end of hyperventilation)there was an increase in to 8.3 kPa (P < 0.05). Regressionanalysis between (kPa) and VE (litre m^–2 min^–1)gave the formula: , r = –0.92, n = 158. Oxygen uptakeand cardiac output did not change significantly during hyperventilation,but decreased in the post-hyperventilation period. An oxygendifference of more than 8 kPa was associated with significantarterial desaturation.     

The fitness of human translocation carriers

A simple method to estimate the mean fitness of human translocation carriers is described. The method is based on information about the inheritance pattern of the translocations. This kind of data can be obtained from the surveys of the chromosome constitutions of new-born babies. The following fitness estimates are obtained: D/D translocation carriers, 0-94; D/G translocation carriers, 0-83; and reciprocal translocation carriers, 0-67. The estimates are rather uncertain due to the scarcity of information, but they are consistent with the expected results. More accurate estimates will be obtained in the future when more data on translocation carriers are available and the cytological classification of the different translocations becomes more exact.     

Acute Phase Reactants in the Initial Phase of Giant Cell Arteritis

ABSTRACT The erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), fibrinogen and haptoglobin were followed weekly during the initial phase of corticosteroid treatment in 18 patients with 19 episodes of giant cell arteritis (GCA). Fibrinogen and CRP decreased most rapidly, with normal values in 67% of the patients after two weeks of treatment. After two weeks 56% of the patients had normal ESR values and 76% after five weeks. Haptoglobin normalised most slowly, no patient having a normal value after one week, 29% after two weeks and 75% after six weeks. For routine clinical use, we found the ESR alone sufficient for monitoring the initial steroid treatment.     

Anti-TNF Treatment of Baboons with Sepsis Reduces TNF-α, IL-6 and IL-8, but not the Degree of Complement Activation

The activation of complement and the release of TNF-α, IL-6 and IL-8 are important pathogenic factors behind organ dysfunction in sepsis. The aim of this study was to determine whether infusion of anti-TNF antibodies alters complement activation and plasma concentrations of pro-inflammatory cytokines at high doses of Escherichia coli . Six baboons received intravenously 2 × 10⁹ live E. coli bacteria per kg body weight (group 1), in addition five received pretreatment with 1 mg per kg body weight anti-TNF antibodies (group 2), and seven received 5 × 10⁸ live E. coli bacteria per kg body weight (group 3). Two hours after the start of infusion of the bacteria, plasma concentrations of C3 activation products, C5a and the terminal SC5b-9 complement complex were increased in groups 1 and 2 ( P  < 0.05), but there was no significant difference between the groups. At 2 h the levels of TNF-α, IL-6 and IL-8 were lower in group 2 compared with group 1 ( P  < 0.05). In group 2 compared with group 1 the TNF-α concentrations were, however, higher at 4, 8 and 24 h. The explanation for this phenomenon is probably that TNF-α binds to the anti-TNF antibody complex and is released slowly after it has been bound. The study showed that infusion of anti-TNF antibodies reduced the concentrations of TNF-α, IL-6 and IL-8, without any detectable influence on complement activation.     

COMPARISON OF PORTABLE EMERGENCY VENTILATORS USING A LUNG MODEL

A lung model was used to test the performance of five emergencyventilators (MEDUMA T Elektronik, MEDUMAT Variabel, OSIRIS,OXYLOG and rescuPAC 2DM). The model comprised two glass jarsfilled with water to suitable compliances and connecting tubes.A resistance (obstruction) was added to one of the ‘bronchial’tubes in order to simulate a patient with obstructive lung disease.Preset minute volume was compared with measured minute volumeand the gas distribution produced by the different ventilators.Acceptable performance was found with the MEDUMAT Elektronik,MEDUMAT Variabel, OSIRIS and OXYLOG ventilators. (Br. J. Anaesth.1993; 70: 372–377)     

NITROUS OXIDE ELIMINATION AND DIFFUSION HYPOXIA DURING NORMO- AND HYPOVENTILATION

We studied the elimination rate of nitrous oxide in 36 patientsundergoing orthopaedic surgery. They were allocated randomlyto one of six groups which differed in time of nitrous oxideexposure and mode of ventilation. In order to simulate recoveryconditions, nitrous oxide administration was discontinued after30, 60 or 120 min of exposure. Either normoventilation or hypoventilationwas used. The mean excretion rate was 1 litre min^–1 at1 min, declining to 100 ml min^–1 at 30 min, with relativelysmall effects of different modes of ventilation and times ofexposure. In spite of an Fl_O2 of 0.30, there were significantdecreases in Sp_O2 during both normo- and hypoventilation. Thesmallest end-tidal oxygen concentrations were reached at 10–15min in the groups with hypoventilation, after 1 or 2 h of nitrousoxide exposure.