Search PubMed⌕ Search

Biomedical subjects

P Biro

Publications and source records attributed to P Biro.

At least 37 records · Page 2Linked to original sources
PubMed1998

A formula to calculate oxygen uptake during low flow anesthesia based on FIO2 measurement.

Monitoring of oxygen uptake during general anesthesia would have several benefits, but unfortunately, this is usually not available in the clinical routine situation. The herein proposed formula to calculate oxygen uptake (.VO2) necessitates only the accurate measurement of FIO2 as well as fresh gas flow and composition. Additionally, this method is not affected by the presence of anesthetic gases. The calculation uses the difference in oxygen content between the delivered fresh gas and the resulting FIO2 in the anesthesia circle system. This gap originates from oxygen uptake (that is mainly caused by metabolic oxygen consumption) and is more pronounced if low fresh gas flows are administered. In order to obtain representative results, calculation of .VO2 should be performed only after achievement of respiratory steady state conditions. Due to its simplicity and wide availability, it has the potential to become a valuable extension in anesthesia monitoring during the performance of routine general anesthesia.

Adult↗
PubMed1998

The efficiency of CO2 elimination during high-frequency jet ventilation for laryngeal microsurgery.

UNLABELLED: For adequate and safe use of high-frequency jet ventilation (HFJV), reliable monitoring of the PCO2 status and course is necessary. Because of improved handling and performance, recently available transcutaneous PCO2 monitoring devices such as MicroGas 7650 (Kontron Instruments Medical Sensors, Basel, Switzerland) should enable more effective surveillance of CO2 elimination and, subsequently, better control of subglottic HFJV. Adult patients (n = 164) undergoing laryngeal microsurgery during total i.v. anesthesia were assessed. The resulting transcutaneous PCO2 values, as well as the necessary driving pressure settings, were analyzed to define the CO2 elimination capacity of each patient. Therefore, an individual CO2 elimination coefficient (ECCO2) was calculated. The frequency distribution of the obtained ECCO2 values showed a normal distribution with a median at 0.79 and a range between 0.30 and 2.17. A significant difference in the frequency of obstructive lung disease was found between two patient subpopulations separated by the 25th percentile at an ECCO2 value of 0.63. Other co-factors of CO2 elimination during HFJV were age, gender, and body weight, whereas height and ventilation duration were not involved. We conclude that the individual assessment of ECCO2 enables one to find adequate ventilator settings, resulting in lower airway pressure and less cooling and drying of the tracheobronchial mucosa. IMPLICATIONS: CO2 elimination during high-frequency jet ventilation can be assessed by calculating the CO2 elimination coefficient (ECCO2) of each patient from the required driving pressure and the resulting transcutaneous CO2 partial pressure. The frequency distribution of ECCO2 in a typical laryngological patient population was analyzed, and a value of 0.63 was found to be a characteristic limit between sufficient and difficult CO2 elimination. The individual assessment of ECCO2 enables one to find adequate ventilator settings, resulting in lower airway pressure and less cooling and drying of the tracheobronchial mucosa.

Adult↗
PubMed1997

[The effect of fresh-gas decoupling on respiratory volume. Draegar Sulla 808V anesthesia ventilator].

UNLABELLED: In order to perform accurate low-flow anaesthesia ventilation, it is desirable to avoid the influence of fresh gas flow (FGF) and inspiration duration (ID) on the resulting minute volume (MV). The Sulla 808V anaesthesia ventilator (Draeger, Luebeck, Germany) is originally not equipped with a fresh-gas decoupling (FGD) device. Therefore, changes of FGF and ID settings applied during controlled ventilation may lead to alterations of the resulting MV. Recently, a low-cost FGD device (Carbamed, Bern-Liebefeld, Switzerland) has been developed, which can be inserted into the circle system. We investigated the effect of this device on MV in the Sulla 808V anaesthesia apparatus. METHODS: The performance of a Sulla 808V anaesthesia ventilator was tested with and without a FGD device. During ventilation of a test lung, stepwise changes of tidal volume (400-1000 ml), FGF (0.5-10 l/min), and ID (0.25-0.5) settings were consecutively applied, and the resulting MV was recorded. Correlation and mean prediction error between ventilation parameter settings and MV were calculated. RESULTS: In the presence of a FGD device, the administered MV was not affected by the magnitude of FGF and ID. A mean prediction error (bias) of -3.6 l/min of the resulting MV was observed. Without FGD the bias was only-1.8 l/min, while FGF and ID revealed a pronounced influence on MV. These effects were statistically significant when using FGF exceeding 4 l/min. CONCLUSIONS: The tested FGD device can easily be integrated into the circle system of conventional anaesthesia machines such as the Draeger Sulla 808V, and is available at a reasonable cost. It allows constant ventilation parameters to be maintained that remain unaffected by wide FGF and ID variations. With this FGD the performance of the ventilator can be improved considerably, and low-flow anaesthesia can be used more extensively.

Humans↗
PubMed1997

Comparison of topical anaesthesia methods for venous cannulation in adults.

A prospective, randomized clinical trial was performed in order to assess the efficacy and side-effects of commonly used topical anaesthesia methods in adults receiving peripheral venous cannulation. The study was double-blinded to the degree that the methodologies allowed. One hundred and fifty healthy adults undergoing elective surgery were allocated at random to five groups: EMLA cream, ethyl chloride spray, intracutaneous infiltration with 2% lidocaine, placebo cream and no treatment. Venipuncture was performed with a 18G cannula on the dorsal side of the hand. Puncture pain and pain caused by the topical treatment itself were measured using a visual analogue scale (VAS, range: 0-100 mm). Haemodynamic response, difficulties in performing the puncture and side-effects were recorded. All analgesic techniques were well tolerated. Haemodynamic response and degree of puncture difficulty showed no differences among the groups. Puncture pain (median mrnVAS) following infiltration (1.0) and EMLA (10.0) was significantly lower than no treatment (30.0) or placebo (30.0). The benefit of local infiltration was altered by injection pain (11.5). Spray did not significantly lower puncture pain (26.5) and, in addition, was associated with discomfort (10.5). In adults, EMLA cream significantly reduces puncture pain and represents an acceptable alternate method for topical anaesthesia in venous cannulation. Local lidocaine infiltration is impaired by applicational pain, whereas spraying the puncture site with ethyl chloride has no analgesic benefit.

Clinical Trial↗
PubMed1997

[The dose-dependent effects of oral premedication with midazolam].

OBJECTIVE: The aim of this study was to examine the psychological effects, well-being and side effects after various doses of oral midazolam medication. METHODS: After informed consent has been obtained and following the approval by the institutional ethical committee, 80 adult patients in the ASA physical status I and II were randomly assigned to one of five different premedication groups: 3.75, 7.5, 11.25, 15 mg midazolam, and placebo. The medication was given in a double-blind fashion 60 min before induction of general anaesthesia for various surgical procedures. At 3 definite stages (before premedication, 30 and 60 min after premedication), blood pressure, heart rate, transcutaneous oxygen saturation and respiratory rate were measured. Sedation and well-being were graded according to a 5-point scale, and the subjective anxiety level was assessed according a visual analogue scale (range 0-100 mm). Anterograde and retrograde amnesia were measured by recall of auditive and visual stimuli. Finally, patients were asked whether in case of future surgery they would prefer the same or a different medication. RESULTS: Demographic data were similar in all groups. There was no significant difference in respiratory rate, oxygen saturation, blood pressure or heart rate. Alertness declined only after 60 min in the groups treated with 7.5 mg and more midazolam. During the entire measurement period, anxiolysis was not different from placebo in any of the midazolam groups. In comparison to placebo, all midazolam groups showed a statistically significant and dose dependent anterograde amnesia for visual stimuli. Subjective well-being scores showed no differences between the groups. Only few side effects were seen following doses of 7.5 mg and higher, including ptosis, strabismus, diplopia, speech disorders, disorientation and vertigo. The majority of patients in all groups indicated a wish for the same medication in case of future anaesthesia for surgical interventions. CONCLUSIONS: Midazolam administered orally prior to surgical procedures showed marked interindividual variability. Sedation and amnesia were dose-dependent and were evaluated by the patients as acceptable. Anxiolysis was not significantly different from placebo. A dose of 7.5 mg midazolam showed the best relation between desirable and undesirable effects. Adequate attention given to the patient by the anaesthesiologist prior to surgery seems to be as important and beneficial as oral medication with midazolam.

Administration, Oral↗
PubMed1996

[Prevention and treatment of postoperative nausea and vomiting with 5-HT3-receptor blockers].

Since there continues to be a high incidence of postoperative nausea and vomiting associated with many types of surgery, and the standard antiemetics often do not achieve satisfactory results, there have been attempts to use the 5-HT3 antagonists. This group of substances is relatively new, but has already been used successfully as an antiemetic during chemotherapy. To date, results are on hand for four different 5-HT3 receptor blockers: ondansetron, tropisetron, granisetron and dolasetron. Applied intravenously, all four have been effective both in prophylaxis and also as therapy for postoperative emesis. Except for ondansetron, there is so far no definitely clear knowledge about the lowest possible effective dosage. The entire group is well tolerated: only occasional and minor side effects have been reported. Even though not all the hopes originally set in the 5-HT3 group of antagonists have been fulfilled, progress has nevertheless been achieved. Especially noteworthy points are a positive cost-effectiveness relationship of these drugs and their appropriate use in case of the proper indications.

Antiemetics↗
PubMed1995

[Intravenous anesthesia with propofol versus thiopental-/enflurane anesthesia. A consumption and cost analysis].

It may be possible to reduce costs in anaesthesia when there is a choice of drugs and methods. Two of the most widespread techniques are inhalation anaesthesia with enflurane following induction with thiopentone, and intravenous anaesthesia (IVA) with propofol. The aims of our study were to compare the costs, effectiveness and side effects of the anaesthetics involved in these two techniques, and to measure significant clinical parameters. METHODS. After approval by the hospital ethics committee, 40 adult patients of ASA physical status 1 and 2 who had been scheduled for elective septorhinoplasty and had given informed consent were entered in our prospective, single-blind randomized study. In 20 patients anaesthesia was induced with thiopentone (4-5 mg/kg) and suxamethonium (1-1.5 mg/kg) and maintained with enflurane. The other 20 patients received an initial i.v. bolus of propofol (2-2.5 mg/kg) followed by a propofol infusion adjusted to their individual clinical needs. Ventilation was performed in both groups with 70% nitrous oxide in oxygen, using a nonrebreathing system. Muscle relaxation was maintained with atracurium. The amounts of anaesthetics, oxygen, nitrous oxide, and muscle relaxants used were measured and a record of the costs was kept. In addition, circulatory and respiratory parameters and quantitative and qualitative aspects of recovery from anaesthesia were recorded. RESULTS. The biometric and clinical data did not differ significantly between the two groups. For induction, 382 (+/- 55.9) mg thiopentone costing 1.24 Swiss francs (SFr), or 172 (+/- 25.1) mg propofol costing 11.87 (SFr) was used. For maintenance, 28.3 (+/- 6.4) ml enflurane costing 21.96 SFr/h, or 450.7 (+/- 247) mg propofol costing 29.75 SFr/h was required. The need for muscle relaxants, oxygen, and nitrous oxide was also not significantly different in the two groups. Additional expenses were due to relaxation antagonists (1.91 SFr per patient in both groups) and to the perfusion pump system (8.60 SFr per patient in the IVA group only). Circulatory and respiratory parameters remained normal in both groups. In the propofol group, the heart rate tended to increase more at the beginning of anaesthesia, whereas later on it showed a tendency to lower values than in the thiopentone/enflurane group. Patients receiving IVA generally had a shorter awakening period, a higher degree of wellbeing during recovery, and needed less systemic analgesics (P < 0.05). CONCLUSIONS. Costs of anaesthetic drugs in the IV group totalled 54.50 SFr during the first hour, i.e. 1.65 times the costs in the thiopentone/enflurane group for the same time. However, with continuing duration of anaesthesia this ratio declines to 1.43 in anaesthesia lasting 2 h. In addition, IVA patients had a noticeably faster and far more pleasant recovery. Minute ventilation, oxygen consumption, heart rate and CO2 production indicated a less pronounced stress response and sympathetic activity during and after propofol. Quicker recovery of cognitive and psychomotor abilities, less postoperative pain and less impairment of respiratory function after IVA may lead to an earlier release from the postoperative recovery unit. This might be a cost-reducing factor that should be taken into account when these two anaesthetic regimens are concerned.

Adolescent↗
PubMed1995

Anesthetic management of a patient with obstructive sleep apnea syndrome and difficult airway access.

Patients with the obstructive sleep apnea syndrome (OSAS) are predisposed to respiratory complications under the influence of sedative and anesthetic drugs because of these drugs' alternation of respiratory control with a tendency for upper airway collapse. Additional difficulties for airway management during anesthesia may arise if fixed anatomic obstacles block the upper airway. We present a case of a patient with OSAS scheduled for general anesthesia for nasal polypectomy and correction of a deviated septum. Preoperative evaluation revealed several factors known to be associated with difficult intubation and ventilation: nasal obstruction, maxillofacial malformation (micrognathia), reduced temporomandibular joint mobility, and obesity. An individualized strategy of airway management based on published standards was developed and successfully applied. It involved fiberoptic guided intubation through a laryngeal mask airway. This case illustrates the management of patients with OSAS and additional conditions that reduce upper airway patency.

Adult↗
PubMed1994

[Ondansetron as prophylaxis for postoperative nausea and vomiting. A prospective randomized double-blind comparative study with droperidol].

Ondansetron, a selective 5-HT3 receptor antagonist, has recently been shown, in a dose of 8 mg, to be superior to 1.25 mg droperidol in preventing postoperative vomiting. There are indications that a dose of 4 mg of ondansetron may be just as effective in reducing postoperative nausea and vomiting as a dose of 8 mg. The aim of this study was to evaluate the efficacy and the adverse effects of 4 mg ondansetron in the prevention of postoperative nausea and vomiting compared to droperidol in patients undergoing surgery with inhalation anaesthesia supplemented with alfentanil. METHODS. Following institutional approval, 40 ASA physical status I and II women scheduled for minor gynaecological surgery gave informed consent to participate in this randomized, double-blind comparative study. Five minutes before induction of general anaesthesia, 20 patients received a single intravenous (i.v.) dose of 4 mg of ondansetron and the remaining 20 received 1.25 mg droperidol i.v. Anaesthesia was induced with 2.1-4 mg/kg of thiopental and 0.1 mg of alfentanil i.v. and maintained with 65% nitrous oxide and 1.5%-3% enflurane in oxygen. On pain stimuli another 0.2-0.4 mg of alfentanil was given. Total effective antiemetic response was defined as the absence of nausea and vomiting for 24 h postoperatively. The incidence of nausea, vomiting and the number of patients showing total antiemetic response as well as the incidence of adverse effects were compared with the chi 2 test and P < 0.05 was considered significant. RESULTS. Patients were similar with respect to age, height, body weight and total anaesthetic agents received. Duration of anaesthesia and the time until awakening was not significantly different among groups. Postoperatively 7 out of 20 patients given 4 mg of ondansetron and 3 out of 20 patients with droperidol vomited (n.s.). The incidence of nausea was 11 out of 20 in the ondansetron group, and 4 out of 20 in the droperidol group (P < 0.05). Sixteen patients in the droperidol group and 8 patients in the ondansetron group showed a total effective antiemetic response (P < 0.05). Postoperative sedation and well-being scores did not differ significantly among groups. CONCLUSION. Our results show that for the prevention of postoperative nausea and vomiting 4 mg of Ondansetron was inferior to 1.25 mg of droperidol. The drugs were given intravenously prior to general anaesthesia for minor gynaecological surgery with nitrous oxide and enflurane in oxygen supplemented with small boluses of alfentanil.

Adult↗
PubMed1993

[Anesthetic gas consumption and costs in a closed system with the PhysioFlex anesthesia equipment].

A marked decrease in both personal and environmental pollution with anaesthetic gases as well as in costs is possible with anaesthesia machines which can be run with a low fresh gas flow (FGF) [9]. Low-flow anaesthesia can be performed with appropriately equipped circle systems, although strongly reduced FGF minimises the control of depth of anaesthesia and gas concentrations. Microprocessor-controlled feedback systems allow the utilisation of closed-circuit systems throughout the whole duration of anaesthesia, maintaining full anaesthetic control [3,5]. The aim of this investigation was to determine the costs resulting from gas consumption and clinical suitability of the recently marketed PhysioFlex anaesthesia machine. METHODS. We used a PhysioFlex (Physio, Hoofdorpp, Netherlands) in a series of 15 routine otorhinolaryngological interventions. After induction with thiopentone and suxamethonium, general anaesthesia was maintained with nitrous oxide in 30% oxygen and isoflurane and supplemented with fentanyl and atracurium. The expenditure of anaesthetic gases was recorded during a total of 61 h and 27 min and differentiated into its components. Anaesthetic gas uptake and costs were compared with different breathing systems (low-flow anaesthesia, semiclosed system and non-rebreathing system) under similar clinical conditions. RESULTS. The average minute volume was 6.84 (+/- 1.17) l and the expiratory isoflurane concentration was 0.91% (+/- 0.14%) (Table 1). These settings resulted in an oxygen expenditure of 27.9 (+/- 8.46) l/h with total costs of SFr. 0.04, nitrous oxide 11.9 (+/- 5.4) l/h and 0.27, isoflurane 3.9 ml/h and SFr. 5.42. In contrast, other breathing systems in analogous settings resulted in greater costs by a factor of 0.77 for low-flow anaesthesia (FGF 1 l/min), 2.47 for a semiclosed system (FGF 3 l/min) and 5.63 for a valve-controlled non-rebreathing system (FGF 6.84 l/min) (Table 2). DISCUSSION. The emission of anaesthetic gases can be lowered by measures that avoid unintended gas fallout, the application of filters, scavenging systems and efficient air circulation in operation and recovery rooms [8]. Above all, the use of the lowest possible FGF is advantageous for the patient insofar as better conditioned breathing gases are available, and economic and environmental effects are more significant (Table 3). With the method of quantitative anaesthesia as performed by the PhysioFlex, it is now possible to reduce gas expenditure according to the requirements of the patient as well as maintaining full control of anaesthesia depth. Simultaneously, multiple secured feedback control systems guarantee adequate monitoring and storage of respiratory and metabolic parameters. The duration of nitrous oxide wash-out can be a problem, in particular, when a changeover to O2/air is required.

Anesthesia, Closed-Circuit↗
PubMed1993

[A modified Macintosh blade for difficult intubation. The mirror blade].

Difficult intubations can occur in cases of anatomical or physiological abnormalities of the face and neck. They are frequently predictable when specific signs are evident preoperatively. There are still occasional unexpected difficulties during conventional laryngoscopy when common blades like the Macintosh and Foregger types are used. During the past 5 decades several authors have proposed many types of laryngoscopes and blades differing in length and shape, as well as various accessories such as guide-wires, prisms, and mirrors. METHOD. We modified a size 3 Macintosh blade by adding a mirror placed tangential to the external curve near the apex. This configuration allows both conventional direct visualisation of the vocal cords and non-direct viewing through the mirror. Insertion of the tube is facilitated using a specially shaped guide-wire. RESULTS. This equipment was used for orotracheal intubation in 20 patients with different degrees of direct laryngeal visibility prior to otolaryngologic endoscopy and surgery under general anaesthesia. Both methods of larynx visualisation were performed and compared. In 1 patient the mirror was not useful because it became fogged. In all the others we could avoid this problem by warming the blade in water. Only in 1 other case was the conventional view better and intubation seemed to be easier than when the mirror was used. In 15 patients the vocal cords were visualised better with the mirror, and intubation was performed by means of the guide-wire with the non-direct technique. In 2 of these cases difficult direct laryngoscopy of grades 3 and 4 according to the Cormack and Lehane classification was found. Four patients were difficult to intubate and neither type of laryngoscopy was ideal. It is notable that a satisfactory view was achieved in the mirror with much less effort. In particular, there was no need to introduce the blade as deeply or raise its apex as much as is usually done. CONCLUSION. The mirror-blade is a suitable device for management of unexpected difficult intubations. Because of its dual availability, it offers both direct and non-direct visualisation of the larynx. Handling of this mirror-blade can be practised extensively, which allows integration of this equipment in the "failed intubation drill". This should be an integral part of the teaching and training of anaesthesia personnel.

Adult↗