Search PubMed⌕ Search

Biomedical subjects

C Lennmarken

Publications and source records attributed to C Lennmarken.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1992

Atracurium-induced neuromuscular block in the isolated arm.

A modification of the isolated arm technique was applied in 10 females under opioid-based i.v. anaesthesia for comparison of the offset of an atracurium-induced neuromuscular block in an isolated arm to an arm with maintained circulation. The neuromuscular blocking effect of a bolus dose of atracurium 0.5 mg.kg-1 was measured bilaterally using the integrated adductor pollicis EMG response (integrated T1 EMG response in % of baseline value and T4/T1 ratio) after bilateral ulnar nerve train-of-four (TOF) stimulation. At 10% T1 recovery, one arm was isolated from the general circulation for 20 min by means of a tourniquet cuff (isolated arm), while normal circulation was maintained in the other arm (control arm). In both arms, the TOF response, peripheral skin temperature, mixed peripheral venous pH and plasma concentrations of atracurium and laudanosine were then measured and compared. Core and peripheral skin temperatures in both arms remained stable and normal throughout the study, and mixed peripheral venous pH stayed within physiological limits in both arms in all subjects. In the isolated arm, recovery of the neuromuscular block was markedly delayed compared to the control arm, the integrated EMG T1 response and TOF ratio being significantly reduced in the isolated arm after 20 min of isolation. The decline in plasma concentration of atracurium was less in the isolated arm than in the control arm, whereas laudanosine levels increased in the isolated and decreased in the control arm. Normal peripheral circulation is of major importance for termination of an atracurium-induced neuromuscular block.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia Recovery Period↗
PubMed1992

Lipoprotein metabolism following gastroplasty in obese women.

In order to elucidate the long-term alterations in cholesterol transport and esterification as a part of the changes in the carbohydrate and lipoprotein metabolism subsequent to calorific restriction, 15 obese women were investigated before and after treatment with vertical banded gastroplasty. Insulin resistance and production, lipid levels in plasma, lipoproteins and the lecithin: cholesterol acyl transferase (LCAT) rate were assessed. There was a 60% decrease in mean calorific intake six months after surgery. A slight hyperglycaemia was almost normalized concomitant with a reduction of serum insulin and C-peptide after 1 year. The very low density lipoprotein (VLDL) level was unchanged. The high density lipoprotein (HDL) levels tended to rise after 1 year, when there was a significant increase of the HDL-2 subfraction. The lipid levels in the lipoprotein fractions showed a rise in mean HDL-2 cholesterol. Both the molar and fractional rates of LCAT were decreased. These results suggest that long-term calorific restriction reduces insulin resistance and production, and lowers VLDL levels and VLDL and cholesterol synthesis. However, the low density lipoprotein cholesterol levels are unchanged, probably because of a decrease in the previously elevated fractional cholesterol removal.

Adult↗
PubMed1991

Delayed recovery of muscle pH after short duration, high intensity exercise in malignant hyperthermia susceptible subjects.

Six subjects susceptible to malignant hyperthermia (MHS) and seven control subjects exercised for 4 min at 120% of their calculated maximal oxygen uptake on a bicycle ergometer. Mean (SEM) muscle pH, measured with a needle-tipped electrode in the vastus lateralis muscle, decreased from a resting value of 7.16 (0.04) to 6.78 (0.04) after exercise in the control group, and from 7.15 (0.05) to 6.56 (0.05) in the MHS group (P less than 0.01 compared with control group). A further decrease in muscle pH to 6.68 (0.06) by 5 min after exercise occurred in the control group, followed by incomplete recovery to 7.06 (0.04) 30 min after exercise. In the MHS group, however, muscle pH decreased to 6.45 (0.05) 5 min after exercise before recovering slowly to only 6.64 (0.07) after 30 min (P less than 0.01 compared with control group). There was no difference in muscle temperature, venous pH or venous lactate concentrations between the two groups. The results show that there is abnormal recovery of muscle pH after short-duration, high-intensity exercise in MHS subjects.

Adult↗
PubMed1991

Carboxyhaemoglobinaemia and pulse oximetry.

We compared measurements obtained with a pulse oximeter (SpO2) against values obtained from a CO-oximeter in a patient with carbon monoxide poisoning. SpO2 was equal to the sum of the oxyhaemoglobin (HbO) and carboxyhaemoglobin (HbCO) values over the range of HbCO from 30 to 1%. This confirms the experimental findings that pulse oximeters measure HbCO as HbO. The patient was treated with oxygen (FlO2 = 50%) and recovered without any sequelae. Under these circumstances, the half-life of HbCO was approximately 2 h.

Adult↗
PubMed1991

Computerized dynamic posturography: a new method for the evaluation of postural stability following anaesthesia.

Dynamic posturography, a new method to study postural stability in humans, was performed in 11 healthy volunteers before administration of midazolam 0.1 mg/kg body weight i.v., and repeated subsequently at 45, 105 and 165 min. Results indicate that balance was affected significantly (P less than 0.008) up to 45 min after i.v. midazolam and did not return to control values until 105 min. The quantified version of the Romberg test performed with the eyes open or closed using the Equitest did not appear to be sensitive in detecting residual effects of midazolam on balance. We conclude that healthy, young persons should not be considered to have regained postural stability for up to 105 min after sedation with midazolam. Dynamic posturography appears to be a useful test in the objective assessment of balance disturbances.

Adult↗
PubMed1991

Twitch tension and train-of-four ratio during prolonged neuromuscular monitoring at different peripheral temperatures.

In eight healthy patients, the influence of the train-of-four (TOF) response of prolonged neuromuscular monitoring and of different peripheral temperatures was studied during normal core temperature. Anaesthesia was induced and maintained with midazolam-fentanyl and a 70/30% mixture of nitrous oxide and oxygen. The mechanical TOF response of the adductor pollicis muscle (twitch tension and TOF ratio), was recorded simultaneously in both hands using supramaximal TOF stimulation of the ulnar nerve at the wrist. One arm was kept normothermic. The other arm was cooled using cold infusions and cold packings. Skin, muscle and core temperatures were continuously measured. In the normothermic arm (skin temperature greater than 32.0 degrees C), the twitch tension and TOF ratio were unchanged following 130-230 min of continuous nerve stimulation. In the hypothermic arm the twitch tension and TOF ratio showed only minor variations above a skin temperature of 32.0 degrees C (corresponding to a mean muscle temperature of 34.5 +/- 0.3 degrees C). Below a skin temperature of 32.0 degrees C a progressive decrease in TOF response was recorded. A linear relationship was found between skin temperature and TOF response as well as between muscle temperature and TOF response. At a skin temperature of 27.0 degrees C (corresponding to a mean muscle temperature of 30.8 +/- 0.4 degrees C), an approximate 20% reduction in twitch tension and a 10% decrease in TOF ratio were recorded with a considerable interindividual variation. We conclude that prolonged TOF nerve stimulation does not change the mechanical twitch response in patients with a normal central and peripheral temperature. A peripheral skin temperature below 32.0 degrees C with sustained and normal body temperature is, however, associated with changes in both twitch tension and TOF ratio that may be a source of error when evaluating neuromuscular function.

Aged↗
PubMed1991

The effect of peripheral hypothermia on a vecuronium-induced neuromuscular block.

Seven healthy patients were investigated during midazolam-fentanyl nitrous oxide-oxygen anaesthesia. The mechanical twitch response of the adductor pollicis muscle was recorded simultaneously during bilateral supramaximal train-of-four (TOF) stimulation of the ulnar nerves at the wrist. Intense neuromuscular block was evaluated using the post-tetanic count (PTC) method. Core temperature and the peripheral skin temperature of one arm were kept normal and stable. Following cooling of the other arm to a peripheral hand skin temperature of 27 degrees C, vecuronium was administered in a bolus dose of 0.05 mg.kg-1 followed by maintenance doses of 0.02 mg.kg-1. In the hypothermic and the normothermic arm the onset time following the bolus dose was 180 +/- 40 (mean +/- s.d.) seconds and 140 +/- 30 s, respectively, the duration of action was 26.4 +/- 4.5 and 16.5 +/- 4.0 min and the recovery time was 265 +/- 90 and 130 +/- 60 s (P less than 0.01). The time course of action following maintenance doses showed a similar marked difference between the hypothermic and the normothermic arm. In the normothermic arm a close correlation was found between the number of post-tetanic twitches and the time to first response to TOF stimulation. In contrast, in the hypothermic arm the number of post-tetanic twitches showed great variation with a poor correlation to the duration of intense neuromuscular block. It is concluded that the time course of action of a vecuronium-induced neuromuscular block is markedly prolonged during peripheral hypothermia and intense neuromuscular block cannot reliably be assessed using the PTC method at low peripheral temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1991

Basic studies of pulse oximetry in a rabbit model.

We have developed an animal model for the evaluation of pulse oximetry during severe hypoxaemia. Twelve rabbits were anaesthetized and mechanically ventilated via a tracheostomy tube. Increasing fractions of nitrogen were added to the gas mixture they inhaled to obtain severe hypoxaemia (saturation range 26%-100%). On 412 occasions, simultaneous pulse oximeter (SpO2) and invasive haemoximeter (SaO2) measurements were compared. The regression analysis of the data gave the equation: y = 0.7 x + 26.7, r = 0.90. In the SaO2 range less than or equal to 85%, the bias (mean value of SaO2-SpO2) was higher when compared with SaO2 greater than 85%. In an in vitro study the light absorption characteristics of rabbit haemoglobin (Hb) were compared to human Hb. The millimolar extinction coefficients of both reduced and oxygenated Hb from rabbits were found to be similar to human Hb. We consider the animal model (rabbit) suitable for studies of pulse oximetry during physiological and pathophysiological conditions.

Animals↗
PubMed1991

Termination of paroxysmal supraventricular tachycardia with a nasogastric tube--a case report.

The case is described of a 29-year-old man with a history of recurrent attacks of paroxysmal supraventricular tachycardia. The patient presented to the emergency ward with complaints of palpitations which had not been relieved by vagal stimulation maneuvers and propranolol. When intravenous metoprolol failed to convert the rhythm, a nasogastric tube was passed which immediately converted the tachycardia to normal sinus rhythm. The literature is reviewed and problems and complications of various techniques are discussed.

Adult↗