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Biomedical subjects

C Lennmarken

Publications and source records attributed to C Lennmarken.

At least 19 recordsLinked to original sources
PubMed1997

The effects of midazolam and flumazenil on psychomotor function.

STUDY OBJECTIVE: To determine the effects of midazolam and its antagonism with flumazenil on psychomotor function as assessed by the perceptive accuracy test (PAT) and choice reaction time (CRT). DESIGN: Double-blind, cross-over, randomized, placebo-controlled study. SETTING: Department of Anaesthesiology, University Hospital, Linköping, Sweden. SUBJECTS: 11 healthy volunteers (6 females, 5 males, mean age 32 years). INTERVENTIONS: Midazolam 0.1 mg/kg (Group MH), midazolam 0.035 mg/kg (Group ML), or placebo (Group PL) were injected intravenously (IV) in a cross-over design. Flumazenil 0.5 mg was injected after 60 minutes. Plasma concentrations of midazolam were measured at 3, 30, 60 and 75 minutes. MEASUREMENTS AND MAIN RESULTS: Baseline values were first obtained on psychomotor tests including the PAT and CRT. These tests were then repeated 30 and 60 minutes after the IV injection of midazolam or placebo, and repeated 15 and 30 minutes following the injection of flumazenil. A dose-dependent effect of midazolam was seen on the PAT and CRT. Flumazenil completely reversed the psychomotor effects of midazolam in Group ML at 60 minutes but not in Group MH, and this action was clearly detected by the PAT. Psychomotor tests had returned to baseline values when the plasma concentration of midazolam was below 33 ng/ml. A marked inter-individual variation was seen on the PAT, CRT, and in the correlation between the plasma concentration and the results on the PAT. CONCLUSIONS: There was a dose-dependent deterioration in psychomotor performance in subjects given midazolam. The PAT was sensitive in the detection of these residual effects, but a large inter-individual variation in the psychomotor effects of midazolam was evident that could be due to pharmacodynamic and pharmacokinetic variability between individuals. Flumazenil in a dose of 0.5 mg IV completely reversed the effects of low-dose, but not high-dose, midazolam.

Adjuvants, Anesthesia↗
PubMed1996

Anaesthesia for day-care arthroscopy. A comparison between desflurane and isoflurane.

A study was undertaken to compare desflurane- and isoflurane-based anaesthesia in patients undergoing day-care arthroscopic surgery. Anaesthesia was induced with propofol 2-3 mg.kg-1 and a laryngeal mask airway was inserted after loss of the eyelash reflex. Patients were then randomly divided into two groups to receive maintenance anaesthesia with either isoflurane or desflurane delivered in oxygen and nitrous oxide. Alfentanil was used as the analgesic during the operation. Early recovery was assessed by measurement of the times to eye opening, extubation and ability to give a date of birth. Psychomotor recovery was assessed by performance on the finger tapping and perceptive accuracy tests. Mood was evaluated using visual analogue mood scores and the mood adjective checklist. Discharge times were also measured. Early recovery was significantly quicker following desflurane anaesthesia but no differences between the groups were found in psychomotor tests. The mood adjective checklist showed that patients in the isoflurane group had a greater total mood score and were more calm than those in the desflurane group; this was particularly evident 2 h after anaesthesia. The discharge times were similar for the two groups. Desflurane is a satisfactory alternative to isoflurane for day care anaesthesia.

Adult↗
PubMed1995

Assessment of recovery following day-case arthroscopy. A comparison between propofol and isoflurane-based anaesthesia.

Fifty healthy patients, aged 15-45 years, undergoing day-case arthroscopy, participated in a study to assess aspects of recovery and mood. Psychomotor tests, including the p-deletion test and the Trieger dot test, were performed pre-operatively and mood was measured using the mood adjective checklist. Anaesthesia in all patients was induced with propofol and a laryngeal mask airway was inserted immediately. All patients received alfentanil as the intra-operative analgesic. The patients were randomly allocated to receive one of two different regimens for maintenance of anaesthesia: propofol group--maintenance with an infusion of propofol 10 mg.kg-1.h-1 for 15 min followed by 6 mg.kg-1.h-1 and nitrous oxide and oxygen (bolus doses of propofol were given if anaesthesia was deemed to be light); isoflurane group--maintenance with isoflurane (inspired concentration 0.5-2.0%) in nitrous oxide and oxygen. Postoperatively, psychomotor tests were repeated every 30 min and mood was measured after 2 h and 24 h. Psychomotor recovery was quicker in the isoflurane group than the propofol group and had returned to baseline values in the isoflurane group by 60 min. The time to discharge was similar in both groups as was the incidence of side effects. There was no difference in mood scores between the groups either at the time of discharge or at 24 h. We conclude that psychomotor recovery is somewhat quicker when isoflurane-based anaesthesia is used for day-case arthroscopy, but other factors, including time to awakening, mood and time to discharge are similar for both techniques.

Adolescent↗
PubMed1995

Pulse oximetry--clinical implications and recent technical developments.

The pulse oximeter has been shown to be a reliable monitor of arterial oxygen saturation and has therefore been recommended as mandatory monitoring for patients during anaesthesia and intensive care. In 1989 two review articles on pulse oximetry were published (1, 2) and two years ago Severinghaus and Kelleher summarized the literature between 1989 and October 1991 (3). Our aim is to focus the discussion on technical aspects and applications of pulse oximetry with special attention centered on recent developments. This review is consequently an update on pulse oximetry since the end of 1991, and the first on technically-based publications in the two last decades.

Animals↗
PubMed1994

Alfentanil or fentanyl during isoflurane-based anaesthesia for day-care knee arthroscopy?

Forty patients agreed to participate in a study to compare whether fentanyl or alfentanil used as analgesic is associated with quicker recovery following anaesthesia for outpatient arthroscopy procedure. Psychomotor tests including choice reaction time (CRT), perceptive accuracy test (PAT) and finger tapping test (FTT) were done prior to induction of anaesthesia with propofol (2-3 mg.kg-1). Patients were then divided into two groups: Group F (fentanyl) received 0.1 mg fentanyl prior to start of surgery and thereafter 0.05 mg every 30 min during the procedure. Group A (alfentanil) received 0.5 mg alfentanil prior to the onset of surgery and 0.25 mg every 15 min thereafter. Anaesthesia was then maintained using isoflurane (0.5-2%) in oxygen and air (FiO2 0.33) during spontaneous respiration with a face mask in a Bain's system. Psychomotor tests were repeated every 45 min postoperatively. Clinical recovery, visual analogue pain intensity score (VAS) and time to discharge home were also assessed by a nurse blind to the method used. Patients in Group A returned to baseline values on the FTT after 90 min while those in Group F did not return to baseline values until 135 min after the end of the operation. Clinical recovery and time to discharge home ("home ready") were also significantly longer in Group F. There was no difference in recovery as seen in the PAT and CRT between the groups. Also, there was no difference in the incidence of side effects and the pain intensity (VAS) scores were similar in the two groups at all time periods.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Out-patient surgery--a survey of anaesthesia care in a university hospital.

This study was done at the Linköping University Hospital, Sweden, to assess the quality of care given to patients undergoing outpatient anaesthesia. A questionnaire was given to all adult patients (> 15 years old) immediately on admission to the outpatients' surgical ward and the patients were asked to answer all the questions, if necessary with the help of an attending nurse. Another questionnaire was given to the patients in the post-operative ward immediately prior to their being discharged home. Analyses of results indicate that although most patients were satisfied with the care offered at the outpatient surgical unit, 50% requested, but were not given, anxiolytic premedication before the operation. A majority of these were women undergoing gynaecological operations. Twenty per cent of the patients complained of post-operative pain that was poorly managed. Drowsiness (12%), headache (10%), and sore throat (8%) were common complications following general anaesthesia. In contrast, patients who had regional or local anaesthesia had an extremely low incidence of complications. Almost one-third of the patients were discharged without a responsible person accompanying them home and 25% were alone at home during the first 24 hours. Of the patients who went home alone, most either walked, cycled or took the bus, but 4% actually drove home after the operation. In our opinion more stress should be laid on patient information before the operation and better methods to relieve preoperative anxiety should be used whenever indicated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Accuracy of pulse oximetry at various haematocrits and during haemolysis in an in vitro model.

In situations in which it may be impossible and/or unethical to evaluate pulse oximetry in humans, an in vitro model with circulating blood may be a necessity. The main objective was to develop such an in vitro model and, in this model, validate the pulse oximetry technique at various haematocrit levels. The pulsating character of arterial blood flow in a tubing system was simulated by using a specially constructed pressure-regulated roller pump. The tubing system was designed to minimise damage to red blood cells. The pulse oximeter readings (SpO2) were compared with oxygen saturation analyses by a haemoximeter (SaO2). The pulse oximetry readings were recorded at various haematocrit levels and during haemolysis in the SaO2 range 60-100 per cent. At a haematocrit level of 41-44 per cent, there was no correlation between SaO2 and SpO2 readings. After diluting the blood with normal saline to a haematocrit of 10-11 per cent, a good correlation between SaO2 and SpO2 was found. Following haemolysis, the agreement between SaO2 and SpO2 was further improved. Using the developed in vitro model, the results indicate that the accuracy of a pulse oximeter may be dependent on the haematocrit level.

Hematocrit↗
PubMed1993

Experimental evaluation of two new sensors for respiratory rate monitoring.

Visual observation was chosen as the reference method for measuring the respiratory rate in ten healthy volunteers. The new fibre-optic and acoustic sensors were simultaneously compared with capnography and transthoracic impedance plethysmography during normoventilation in the respiratory rate range of 6-24 breaths per minute and at a fixed respiratory rate of 13 breaths per minute. In addition a simulation of central apnoea was performed. All the measurements were recorded on an analogue tape recorder and a strip-chart recorder and analysed off line. The analyses of the recordings were performed by a person who was unable to see the monitoring systems. There was no discrepancy in the results of these methods. Each of the methods responded rapidly to an apnoeic event. The new fibre-optic and acoustic sensors correlate well with more traditional methods such as capnography and transthoracic impedance plethysmography for respiratory rate monitoring.

Acoustics↗
PubMed1993

Peroperative nitrous oxide does not influence recovery after laparoscopic cholecystectomy.

We have evaluated the effects of nitrous oxide on recovery following laparoscopic cholecystectomy in a prospective, randomised, double-blind study with 42 otherwise healthy patients. All patients received meperidine 1 mg/kg and atropine 6 micrograms/kg im for premedication, and anaesthesia was induced with fentanyl 2 micrograms/kg and thiopental 4-6 mg/kg. Succinylcholine was used for the intubation and muscle relaxation was achieved using vecuronium. Isoflurane with 70% nitrous oxide in oxygen and fentanyl was used for maintenance of anaesthesia in group I (n = 19), and isoflurane in air/oxygen and fentanyl in group II (n = 23). The postoperative ward staff and the surgeon evaluating the postoperative recovery were blinded to the anaesthetic technique. No differences were found in duration of operation and anaesthesia, need for postoperative analgesia or postoperative nausea treated medically. Recovery, judged by the Steward Coma Score, comprehension and collaboration, degree of sedation and orientation in time and space, was similar in the two groups. Postoperative hospital stay was 1 (1-4) day in the nitrous oxide group (median (10-90th percentiles) versus 2 (1-4) days in the air group. The time until patients were recovered, as judged by return to work and normal daily activities, was the same in the two groups: 8 (4-11) days in the nitrous oxide group and 8 (4-11) days in the air group. We conclude that nitrous oxide has no influence on recovery after laparoscopic cholecystectomy.

Adult↗
PubMed1993

Halothane-diethyl ether azeotrope anesthesia under primitive conditions: guidelines for neuromuscular blockade with vecuronium.

The dose-response relationship for vecuronium during anesthesia with the azeotropic mixture of halothane and diethyl ether (HE) (66 ml of halothane mixed with 34 ml of ether in the same bottle)/oxygen was compared with halothane/nitrous oxide/oxygen anesthesia. The HE is not explosive and has preserved many of the advantageous properties of diethyl ether, making it an attractive anesthetic drug under difficult circumstances such as war or civil disaster. If muscular relaxation is needed in military anesthesia, it is essential to use a short- to medium-acting compound that can be stored without refrigeration. Vecuronium bromide fulfills these criteria. The study was conducted on 20 young (mean 24 years, range 18-31), ASA I patients. Using adductor pollicis mechanomyography and a cumulative dose technique, individual dose-response curves for vecuronium were constructed. Care was taken to keep peripheral and core temperatures normal and the times of exposure to inhalational gases equal. The results were analyzed by the log-probit method. During HE anesthesia, ED50 for vecuronium was 22 +/- 2 micrograms kg-1 (mean +/- SE) and ED90 was 49 +/- 8 micrograms kg-1. During halothane/nitrous oxide anesthesia, ED50 for vecuronium was 18 +/- 2 micrograms kg-1 (mean +/- SE) and ED90 was 39 +/- 7 micrograms kg-1. The dose-response relationships for vecuronium were similar during HE anesthesia and halothane/nitrous oxide anesthesia.

Adolescent↗
PubMed1992

Psychomotor recovery following propofol or isoflurane anaesthesia for day-care surgery.

A newly developed test for the assessment of psychomotor recovery--the perceptive accuracy test (PAT)--is described. Seventy-four subjects who performed the test though that it was easy to perform and some were motivated to try it on a number of occasions. Eight persons performed the test on different days and at different periods of time; the results were consistent and reproducible. Eight more persons were then asked to do the test 4 times at 15-min intervals; no 'learning' was seen with this test. A randomized, prospective study was then performed in two groups of 15 patients, undergoing arthroscopic procedures of the knee. Anaesthesia was induced with propofol and maintained with an infusion of propofol 12 mg/kg/h for the first 15 min, followed by 8 mg/kg/h subsequently in the propofol group. In the isoflurane group, anaesthesia was also induced with propofol, but isoflurane (0.5-2%) was used to maintain anaesthesia. Alfentanil was the analgesic used in both groups of patients. Results were compared with a third group of unanaesthetised controls, who were asked to perform psychomotor tests including choice reaction time and PAT at 30-min intervals for 2.5 h. There was a significant difference (P less than 0.01) in psychomotor recovery on the PAT-200 between the propofol group and control groups, but not in the isoflurane and control groups at 30 min. Both groups had returned to baseline values at 60 min in the PAT-60 and PAT-200. The choice reaction time showed no significant difference in either group 30 min after the anaesthetic.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The influence of changes in blood flow on the accuracy of pulse oximetry in humans.

Oxygen saturation (SpO2) was measured with a pulse oximeter in ten healthy, young men breathing air. A pulse oximeter probe was attached to the second toe and a laser Doppler probe to the first toe of the same foot for measurement of changes in peripheral blood flow. The pulse oximeter and laser Doppler readings were simultaneously compared when the foot was positioned 40 cm (position 1) above heart level, elevated 10 cm (position 2) above heart level and horizontally at heart level (position 3). Using this experimental human model, we achieved various blood flows. The AC and DC optical signals used for determination of oxygen saturation were recorded from the pulse oximeter and analysed. There was a significant increase (P less than 0.05) between position 1 and 3 in blood flow as measured by the laser Doppler flow meter. The corresponding pulse oximeter readings of haemoglobin saturation also increased significantly (P less than 0.05) comparing these two leg positions. Analysing the AC- and DC optical signals, the AC value of infrared light increased considerably, while the AC value of the red light decreased slightly. The DC values of red and infrared light did not change significantly. In summary, when blood flow was decreased, the ratio of red to infrared transmitted light was changed, resulting in a low SpO2 reading.

Adult↗
PubMed1992

The accuracy of pulse oximetry at two haematocrit levels.

The object of this study was to investigate the influence of haematocrit on the accuracy of pulse oximetry. Seven Swedish land race rabbits were studied. The oxygen saturation of haemoglobin was decreased step-wise using increasing fractions of nitrogen to the inspiratory gas. One pulse oximeter probe was attached on the front leg and another probe directly over the common carotid artery. The pulse oximeter readings (SpO2) were compared with simultaneous oxygen saturation analysis (SaO2) by a haemoximeter. The pulse oximeter measurements were performed at the haematocrit levels of approximately 40% and 11%, respectively. We found a good correlation between SpO2 and SaO2 in a wide range of the oxygen saturation, i.e. SaO2 26-100%. After haemodilution the correlation was improved in the range 86-100%, but not in the range 26-85%. No correlation between SpO2 and SaO2 was found when the sensor was attached directly over the artery during normal haematocrit levels. After haemodilution a better correlation was however obtained. These results indicate that the accuracy of pulse oximetry is dependent on the haematocrit level.

Animals↗
PubMed1992

Thiopentone or propofol for induction of isoflurane-based anaesthesia for ambulatory surgery?

This study compares psychomotor recovery following induction of anaesthesia with either thiopentone or propofol in 30 healthy, unpremedicated patients undergoing outpatient arthroscopic procedures of the knee. A battery of tests including simple reaction time (SRT), choice reaction time (CRT), perceptive accuracy test (PAT) and digit symbol substitution test (DSST) were done before anaesthesia. The patients were randomly divided into two groups: Group 1 was induced with thiopentone 5-6 mg/kg while Group 2 was induced with propofol 2-3 mg/kg. Anaesthesia was then maintained with isoflurane (0.5-2%) in oxygen and air, and supplements of alfentanil were given for analgesia during spontaneous respiration with a face mask. Psychomotor recovery assessed every 30 min postoperatively for 120 min showed that patients in Group 1 had not returned to baseline values until 120 min after the operation on the PAT, while those in Group 2 had returned to baseline values at 60 min. No patient had any significant side effects. The SRT, CRT and DSST proved to be relatively insensitive in the detection of residual effects of anaesthesia and had a significant learning effect. This study suggests that induction of anaesthesia with propofol followed by maintenance with isoflurane in oxygen and air during spontaneous ventilation is associated with rapid psychomotor recovery and is a suitable method for ambulatory surgery. The PAT is sensitive and not associated with some of the problems found with other commonly used tests.

Adult↗
PubMed1992

Attenuated ventilatory response to hypoxaemia at vecuronium-induced partial neuromuscular block.

The effect of a partial neuromuscular block on the ventilatory response to hypercarbia and to hypoxaemia was studied in 11 non-anaesthetized male subjects. Respiratory frequency, tidal volume, minute volume, respiratory timing and drive were measured during air breathing and during stimulation by hypercarbia and hypoxaemia. The ventilatory response was defined as the ratio between, respectively, tidal volume and minute volume during ventilation stimulated by hypercarbia and hypoxaemia compared to measurements during air breathing. The ventilatory measurements were repeated on three separate occasions: before neuromuscular block was established, during an infusion of vecuronium aiming at a mechanical adductor pollicis train-of-four (TOF) ratio of 0.70, and after the infusion had been stopped and the neuromuscular block had spontaneously recovered to a TOF ratio of > 0.90. Resting ventilation during air breathing remained with minor variations throughout the experiment. The ventilatory response to hypercarbia was not affected at a TOF ratio of 0.70 as compared to measurements before vecuronium and at a TOF ratio of > 0.90. In contrast, the ventilatory response to hypoxaemia was markedly reduced at a TOF ratio of 0.70. We conclude that a mechanical TOF ratio of 0.70 following vecuronium may be associated with an inadequate ventilatory response to hypoxaemia.

Adult↗