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Biomedical subjects

H Deriaz

Publications and source records attributed to H Deriaz.

At least 19 recordsLinked to original sources
PubMed1992

[Effect of hygrophobic filter or heated humidifier on peroperative hypothermia].

A study was carried out to find out whether the use of a hygrophobic filter (Pall, Ultipor) or of a heated humidifier (Dräger, Aquapor) during surgery had any effect on a patient's intraoperative core temperature and thermal balance. Seventy-five ASA I or II patients scheduled for gynaecological surgery were randomly assigned to three groups: group A (n = 25), where no warming device was used; and two groups (n = 25 for each) where inhaled gases were humidified and heated with either a hygrophobic filter set up between the endotracheal tube and the Y-piece (group B) or a heated humidifier set to 100% saturation at a temperature of 41.5 degrees C (group C). The patients were all anaesthetised with the same technique (thiopentone 5 mg.kg-1, dextromoramide 0.03 mg.kg-1 and 0.1 mg.kg-1 of either pancuronium or vecuronium, followed by enflurane with nitrous oxide in oxygen); the perfused fluids were not heated. Room, tympanic, rectal, oesophageal and four skin (thorax, arm, leg, thigh) temperatures were measured with calibrated Exacon thermistances, on arrival in the operating theatre, during induction, every ten minutes for two hours, and then every twenty minutes for two hours more. Ramanathan's and Burton's formulae were used to calculate mean skin temperature and heat loss respectively. In the recovery room, patients were warmed up with an electric blanket. Shivering was ranked from "0" to "+ +". There were no differences between groups as far as age, drug doses, perfusion volumes and room temperature were concerned.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1992

[Monochromatic infrared halogenated gas analyzer and handling errors].

Monochromatic infrared gas spectrometers cannot identify volatile agents. Such an analyser (Capnomac, Datex) was tested while performing two errors: a) erroneous selection of the agent on the analyser, the vaporizer being filled with the correct agent; b) total or partial filling of the vaporizer (Vapor 19, Dräger) with an incorrect agent, the analyser being set for the agent the vaporizer was specified for. Three agents were studied, halothane (H), enflurane (E) and isoflurane (I). Each experiment was made in triplicate, the vaporizer being dried out between each. In case of erroneous selection on the analyser, differences between E and I were very small. When H was erroneously selected, the concentration displayed was six times higher, and when E or I was selected instead of H, the concentration displayed was six times lower than expected. In the 3.3-3.5 m band, H transmittance was six times higher than those of E and I. The agent selection control changes the gain so as to correct for the selected agent (gain for H: 12.0, E: 2.24, I: 1.89). In case of erroneous filling of the vaporizer, the concentration displayed was always different from that expected. When E or I was delivered with an H vaporizer, the analyser being set on H, the concentration displayed was 3 to 9 times higher than the concentration that had been set. On the other hand, when H was delivered with an E or I vaporizer, the analyser being set to E or I, the concentration displayed was 4 to 8 times lower.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1992

[Physical modeling of inhalation anesthesia].

A new physical model simulating the pharmacokinetics of volatile anaesthetics is presented. It consists in a ventilator connected to a water manometer. Gas is removed from the gaseous part of this manometer with a constant rate pump. This gas flow is directed thereafter into three capacitances with valves and pumps: one capacitance only contains air, representing the lungs, and the other two olive oil, representing the visceral and muscle compartments. Halothane, enflurane and isoflurane (1 vol%) were administered to this model with different values of cardiac output and alveolar ventilation. There was good concordance between the values of FA/FI that were measured in this model and those calculated by computer simulation. No correction factor was required. Such a physical model may therefore be used to test new techniques of administration of volatile agents.

Anesthesia, Inhalation↗
PubMed1992

[Effects of nifedipine premedication on peroperative hypothermia].

The intraoperative time-course of core temperature in patients premedicated with nifedipine (n = 30) was compared to that of control patients (n = 30). Distal oesophageal temperature (TCORE) was recorded every five minutes during total hip replacement in 60 adults ranked ASA 1 to 2. Patients in the control group were only premedicated with 100 mg of oral hydroxyzine. The treatment group consisted of 30 patients taking nifedipine for blood pressure control or coronary insufficiency. They were given 10 mg sublingual nifedipine as well as the hydroxyzine premedication. Anaesthesia was induced with thiopentone, fentanyl and vecuronium, and maintained with nitrous oxide in oxygen and halothane in a semi-closed circuit. The slopes of the time-course for TCORE were established for each patient, using two linear regressions, between 0 and 0.5 h and from 1 to 2 h. The two groups did not differ in age, weight, ambient temperature, blood pressure, heart rate, and volume of unwarmed blood transfused. TCORE differed significantly from the 25th minute on until the end of the study period. Contrary to all expectation the TCORE at 2 h was higher in the nifedipine group (34.85 +/- 0.09 degrees C) than in the control group (34.01 +/- 0.14 degrees C, p < 0.001). TCORE decreased more rapidly in the control group during the first study interval (0 to 0.5 h), -1.50 +/- 0.60 degrees C.h-1 vs -2.34 +/- 1.02 degrees C.h-1 (p < 0.001). The second slopes did not differ particularly (-0.96 +/- 1.32 degrees C.h-1 vs -0.90 +/- 0.42 degrees C.h-1 respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

[Postoperative shivering: analysis of main associated factors].

This study was carried out in 75 female patients, ranked ASA 1 or 2, during recovery from balanced general anaesthesia. It aimed to find out the main determinants of postoperative shivering and its thermal effects. Skin and oesophageal temperature were recorded every ten minutes. Mean skin and body temperatures, and the intraoperative energy balance were calculated. There was no additional source of heating. Shivering was ranked from 0 to 2. Statistical analysis showed that the starting mean core and body temperatures were the only factors correlated with shivering and its intensity, whereas mean skin temperatures, age and opioid doses were not. Between 33.5 and 36.5 degrees C, there was a linear relationship between the oesophageal temperature at the end of anaesthesia and the incidence of shivering. A decrease of 1 degrees C in core temperature increased the probability of shivering by 33%. At 35.4 degrees C, 50% of patients shivered. There was a homogenous group of patients whose oesophageal temperature at the end of anaesthesia was between 35 and 36 degrees C. In this group, there was no significant difference between starting skin temperatures, whether the patient shivered or not. However, the core temperature of those within that group that did shiver returned to normal levels more quickly than in those that did not shiver. These data underlined the essential role played by core temperature at the end of anaesthesia in postoperative shivering and its intensity, as well as the heat producing value of shivering. It would therefore seem logical to prevent postoperative shivering by avoiding intraoperative hypothermia.

Adult↗
PubMed1989

[A mistake in the filling of a vaporizer detected by an infrared analyser of halogenated anesthetic agents].

An anaesthetic pitfall related to an incorrectly filled vaporizer, without harmful effects on the patient, is reported. A halothane specific vaporizer has been accidentally partially filled with enflurane. The incident was suspected when the Datex Normac infrared analyser, calibrated for halothane, displayed an inspired concentration of 0.83% v/v, whereas the Dräger Vapor 19 vaporizer dial was set to deliver 0.4% v/v with a fresh gas flow of 2.7 l.min-1 to a circle system. The analyser uses infrared gas spectrometry, in the 3.3 to 3.5 microns band which contains the absorption peaks of halothane, enflurane, isoflurane and methoxyflurane. The four agents have different transmittances, with halothane the greatest. The agent selection control changes the gain to correct for the selected agent. The measurements are only accurate when only one agent is present at a time. In the reported case, the displayed concentration was very high because the high gain of halothane (12.0) was applied to enflurane (enflurane gain: 2.24). An in vitro experiment measuring the values of different enflurane/halothane mixtures, carried out with the involved vaporizer, showed that it contained, at the time of the incident, a mixture of 20% enflurane and 80% halothane. It may therefore be possible to detect a vaporizer filling error when the values "measured" by the analyser are not in concordance with those set on the vaporizer. Filling an enflurane vaporizer with halothane is more dangerous, as it results in a high halothane output with a Normac "enflurane" inspired concentration remaining very low. The indexed pin safety system remains the best means of avoiding wrong vaporizer filling.

Anesthesia, General↗
PubMed1989

Vascular occlusions for liver resections. Operative management and tolerance to hepatic ischemia: 142 cases.

The intra- and early postoperative courses of 142 consecutive patients who underwent liver resections using vascular occlusions to reduce bleeding were reviewed. In 127 patients, the remnant liver parenchyma was normal, and 15 patients had liver cirrhosis. Eighty-five patients underwent major liver resections: right, extended right, or left lobectomies. Portal triad clamping (PTC) was used alone in 107 cases. Complete hepatic vascular exclusion (HVE) combining PTC and occlusion of the inferior vena cava below and above the liver was used for 35 major liver resections. These 35 patients had large or posterior liver tumors, and HVE was used to reduce the risks of massive bleeding or air embolism caused by an accidental tear of the vena cava or a hepatic vein. Duration of normothermic liver ischemia was 32.3 +/- 1.2 minutes (mean +/- SEM) and ranged from 8 to 90 minutes. Amount of blood transfusion was 5.5 +/- 0.5 (mean +/- SEM) units of packed red blood cells. There were eight operative deaths (5.6%). Overall, postoperative complications occurred in 46 patients (32%). The patients who experienced complications after surgery had received more blood transfusion than those with an uneventful postoperative course (p less than 0.001). The length of postoperative hospital stay was also correlated with the amount of blood transfused during surgery (p less than 0.001). On the other hand, there was no correlation between the durations of liver ischemia of up to 90 minutes and the lengths of postoperative hospital stay. The longest periods of ischemia were not associated with increased rates of postoperative complications, liver failures, or deaths. There was no difference in mortality or morbidity after major liver resections performed with the use of HVE as compared with major liver resections carried out with PTC alone, although the lesions were larger in the former group. It is concluded that the main priority during liver resections is to reduce operative bleeding. Vascular occlusions aim at achieving this goal and can be extended safely for up to 60 minutes.

Aged↗
PubMed1987

Continuous i.v. infusion of labetalol for postoperative hypertension. Haemodynamic effects and plasma kinetics.

Labetalol is a combined alpha- and beta-adrenoreceptor blocking agent. A loading dose may be used to antagonize sympathetic overactivity rapidly after surgery and be followed by a continuous infusion to achieve a stable effect. The haemodynamic effects and pharmacokinetics of this method of labetalol administration were studied in six rewarmed, extubated and sedated patients 15 +/- 2 h after aortobifemoral bypass surgery. Patients were monitored with radial and thermistor-tipped pulmonary artery catheters. Labetalol 1.5 mg kg-1 was injected i.v. over 5 min and a maintenance infusion of 0.2 mg kg-1 h-1 was started 30 min later and continued for 5.5 h. Within 5 min of the loading dose, i.v. labetalol induced significant (P less than 0.05) decreases in mean arterial pressure (-32 +/- 11%), in heart rate (-20 +/- 11%) and in cardiac index (-26 +/- 15%) that lasted throughout the infusion. Changes in systemic vascular resistance were not uniform, but an increase was not observed in any patient. Mean stroke volume index and ventricular filling pressures were not significantly affected by labetalol administration. The mean measured steady state plasma concentration (Css) (264 +/- 46 ng ml-1) was higher than predicted (170 ng ml-1) because the clearance (13.1 +/- 2.4 ml kg-1 min-1) was lower than that used to calculate the infusion rate. We conclude that labetalol is an effective antihypertensive agent in the postoperative period. A Css can be achieved rapidly by such i.v. administration and this offers the advantage of inducing rapid and stable haemodynamic effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

[French survey on anesthesia systems and peroperative respiratory monitoring equipment].

A national inquiry has been carried out in France. It concerned the anaesthetic systems and respiratory monitoring equipment in use at the moment, as well as that wished for. The equipment in use was very stereotyped: an open system with a respirator, for the most volumetric, and with a safety O2/N2O mixer. Monitoring is carried out with the pressure gauges and the measure of expiratory volume; only two thirds of the equipment had an alarm. The O2 and CO2 analysers were little used. Expired CO2 monitoring was only carried out in teaching hospitals and in big centres. Apart from this, the equipment was independent of the hospital and the type of surgery carried out. As for anaesthetic systems, 53% of centres would like obtain open systems, 15% closed systems; 32% did not answer. This increase in number of closed systems is not significant. However, a very strong wish for respirators with flow rate control and safety O2/N2O mixers was observed, whilst the safety parameters of these mixers were open to discussion. Respiratory monitoring was not just confined to the mechanical aspects, as 65% of centres wished to monitor FIO2. The big centres and the teaching hospitals were interested by the expiratory CO2 monitoring. This inquiry showed the interest in respiratory safety in operating theatres. Further studies should confirm or not the increasing interest in closed systems.

Anesthesia, Closed-Circuit↗
PubMed1985

[Determination of the dose-response curve for atracurium dibesylate in the anesthetized adult].

The mechanical response of the adductor pollicis to a 0.15 Hz stimulation of the ulnar nerve was studied in 35 unpremedicated adult patients (mean age 38 yr) under general anaesthesia using thiopentone, fentanyl and a N2O/O2 mixture under mechanical ventilation. PaCO2, pH, K, Ca, Mg plasma levels and temperature were in the normal range. Each patient received a single bolus of atracurium dibesylate: 0.10 mg . kg-1 (n = 11), 0.15 mg . kg-1 (n = 10), 0.20 mg . kg-1 (n = 11) or 0.30 mg . kg-1 (n = 4). The dose-response curve was constructed using the log-probit method for 0.10, 0.15, 0.20 mg . kg-1 doses, giving neuromuscular blocks greater than 0% and less than 0.20 mg . kg-1. The 0.20 mg . kg-1 dose had an onset time of 6.1 +/- 0.6 min, duration 0-90% of 34.3 +/- 3.2 min and a recovery index 25-75% of 10.9 +/- 1.0 min. The 0.3 mg . kg-1 dose resulted in onset time of 4.7 +/- 1.3 min, duration of 39.9 +/- 3.7 min and a recovery index of 10.7 +/- 1.8 min. Thus atracurium dibesylate seemed to be an agent of intermediate potency. Onset time was approximately the same as that for other non-depolarizing neuromuscular blocking drugs, but duration of action and recovery index were quite shorter, except for vecuronium bromide.

Adult↗
PubMed1985

[Modeling and BASIC program for the kinetics of inhalation anesthetic agents].

The pharmacokinetics of inhaled anaesthetics has been well described by Eger's model using a monoalveolar lung with continuous alveolar ventilation and four extrapulmonary compartments defined by their blood supply and anaesthetic solubility. The model is presented with its equations. A Basic microcomputer programme is proposed for this model: expected concentrations of anaesthetic in various conditions of administration, ventilation or cardiac output are shown, such as the uptake and distribution of nitrous oxide during anaesthesia. Different inhaled anaesthetics were compared for induction and recovery times in standardized conditions of administration.

Anesthesia, Inhalation↗
PubMed1985

Factors influencing pulmonary volumes and CO2 elimination during high-frequency jet ventilation.

An external spirometric method using a differential linear transformer was used to measure tidal volume (VT) and to determine factors influencing CO2 elimination and HFJV-induced "PEEP effect" in 15 critically ill patients under HFJV. VT increased with increasing driving pressure (DP) and decreasing frequency (f) and was influenced little by changes in I/E ratio. CO2 elimination, as reflected by the measurement of PaCO2, was mainly influenced by the absolute level of VT rather than by the product VT X frequency (PaCO2 = 5715/VT, r = 0.75, P less than 0.05). The primary phenomenon explaining HFJV-induced "PEEP effect" was intrapulmonary gas trapping due to incomplete exhalation of the first VT administered: the spontaneous relaxation times of these first VT were longer than expiratory time allotted to the ventilatory settings. HFJV-induced "PEEP effect" increased with I/E ratio, DP, and f and was markedly influenced by the mechanical properties of the total respiratory system. At given ventilatory settings, HFJV-induced "PEEP effect" was greater in patients with a normal or elevated time constant of the total respiratory system (tau RS) than in patients with a low tau RS. These results suggest that HFJV should not be used in patients with chronic obstructive pulmonary disease and asthma, and should be preferentially administered to patients having stiff lungs or decreased chest wall compliance.

Adult↗