Biomedical subjects
Publications and source records attributed to S Henneberg.
A study with 133 adults, who had been breast-fed or bottle-fed after birth, shows that neonatal experience with vanilla influences preferences for other foods in later life.
The need for continuous, noninvasive, and reliable respiratory rate monitoring during recovery from general anesthesia has long been recognized. Alternative principles can be grouped into those detecting the respiratory effort, and those detecting the actual result, i.e. the respiratory gas flow. The second category is of greatest interest for patient monitoring. In this paper, we report the development and initial clinical experience with a new acoustic air-flow sensor. By differential, multipoint detection of the air-flow in the mouth and nose region, the sensor can easily discriminate against different kinds of interference, including motion artefacts. The sensor is nonexpensive, rugged, simple to apply and inherently safe. An instrument with continuous display of respiratory rate, and an audiovisual apnea alarm has been designed and built. The complete system has been tested on patients during recovery after general anesthesia. In 16 patients, the respiratory rate displayed by the instrument has been correlated against that visually observed. A good correlation was obtained. Minor discrepancies can be explained from the fact that visual observation corresponds to the respiratory effort, whereas the sensor detects the actual air flow. In 12 patients, 24 hour simultaneous recordings were made of respiratory rate with the new sensor, with simultaneous recording of the oxygen saturation and the heart rate with a pulse oximeter. It was found that the new sensor reliably recorded respiratory depression and apnea. Such events may in some patients be as frequent as one incident per hour. One case of 'Ondine's curse' provided clear evidence that pulse oximetry has a low sensitivity to respiratory disorders.
A system for patient monitoring during magnetic resonance imaging (MRI) is described. The system is based on remote auscultation of heart sounds and respiratory sounds using specially developed pickup heads that are positioned on the precordium or at the nostrils and connected to microphones via polymer tubing. The microphones operate in a differential mode outside the strong magnetic field to reduce various sources of interference from the MRI equipment. After amplification, the signal is transmitted as infrared light to a small, battery-operated receiver and a headphone set. Thus, the patient can be simultaneously auscultated both inside and outside the shielded MRI room by infrared transmission through a metal mesh window. Bench tests of the system show that common mode acoustic noise is suppressed by approximately 30 dB in the frequency region of interest (100-1,000 Hz), and that polymer tubing having a diameter of approximately 2 mm can be used for efficient sound transmission. Recordings in situ show satisfactory detection of both heart sounds and respiratory sounds, although the signal is somewhat masked by noise during imaging. A clinical test incorporating 17 sedated or anesthetized patients was also performed. In all but four cases, the quality of the breath and heart sounds was regarded as acceptable or better.
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We have measured plasma concentrations of local anaesthetics, and the substance fraction of methaemoglobin (MetHb), in infants less than 3 months of age, after application of a lignocaine-prilocaine cream (EMLA). A total of EMLA 2 g was applied over four different skin areas, totalling 16 cm2, for 4 h before anaesthesia for a minor surgical procedure. Sampling was carried out before and 4, 8 and 12 h after application. Maximum MetHb values (median = 2.24%) were obtained usually at 8 h and were significantly (P less than 0.001) higher than before application (median 1.32%). The plasma concentrations of local anaesthetics were low (maximum values: prilocaine 78 ng ml-1, lignocaine 412 ng ml-1). The activity of erythrocyte MetHb reductase (cytochrome b5 reductase) was analysed. Data from a previously studied group of infants aged 3-12 months were included also. Enzyme activity did not reach adult levels until after the age of 3 months. It showed a good inverse correlation with the maximum MetHb values after application of EMLA. Although the MetHb concentrations in the infants younger than 3 months were small, the enzyme capacity may be overloaded when EMLA is administered at the same time as other MetHb-inducing agents. It is concluded that the use of EMLA should be restricted in this age group.
The aim of the study was to evaluate the effect of a lidocaine-prilocaine cream (EMLA cream, Astra) in relieving pain during arterial cannulation. The study had a random, double-blind, placebo-controlled design and included altogether 90 patients. All the patients were premedicated with an opioid before cannulation. An EMLA application time of 60 minutes was used in 60 patients (30 EMLA/30 placebo) and there was no difference in the pain reaction measured on a visual analogue scale (VAS) or on an observer's verbal scale. The study was extended with a further 30 patients (15 EMLA/15 placebo) with an application time exceeding 90 minutes. Between these groups pain experience measured by VAS did not show any significant difference although the mean value was lower in the EMLA group. Observer ratings showed a significant (p less than 0.01) difference in distribution towards lower ratings in the EMLA group. In conclusion EMLA was found to have a weak, but measurable effect when the application time exceeded 90 minutes but not after 60 minutes.
The present investigation was undertaken in order to determine the release of 3-methylhistidine (3MH) from the splanchnic region and from the leg, and the contributions these make to the increase in urinary 3MH excretion in infection. Thirteen febrile patients with infection were investigated. After an overnight fast, hepatic vein, femoral vein, and radial artery catheterizations were performed. Splanchnic and leg blood flows were determined by dye dilution technique. Plasma 3MH was analyzed by a modified HPLC method. The release of 3MH from the leg was 0.064 +/- 0.007 mumol/min (+/- SE) and from the splanchnic region 0.012 +/- 0.013 mumol/min. These releases of 3MH constitute 27% +/- 2% and 8% +/- 6% of the individual urinary excretions, respectively. With increasing degree of catabolism, measured as individual 3MH increase above baseline excretion or as the 3MH to creatinine ratio (3MH:Cr), the relative contribution to urinary excretion from the leg was increased (individual increase, P = 0.08; 3MH:Cr, P less than 0.01). Since this contribution was not decreased in the more catabolic patients, as would have been expected if the increase in urinary 3MH originated elsewhere, it is concluded that skeletal muscle is the source, and these results thus validate the use of urinary 3MH excretion as a marker of myofibrillar protein catabolism in infected patients.
When 3-methylhistidine (3MH) excretion is used as an indicator of myofibrillar protein catabolism, there are restricting factors, such as meat intake, incorrect 24-h urine collections, and a large interindividual variation in basal excretion. 1-Methylhistidine (1MH) was previously suggested as an indicator of meat intake. We studied the basal urinary excretion of 1MH and whether this was influenced by infection and we compared the use of 3MH vs the 3MH:creatinine ratio (3MH:Cr) in detecting changes during infection. The basal excretion of 1MH was 84.9 mumol/24 h and its creatinine molar ratio (1MH:Cr) was 7.4 x 10(-3) with no change during infection. Because 1MH:Cr was significantly increased in 4 of 14 patients, their 3MH values were considered influenced by meat intake and thus discarded. Among the remaining 10 patients, 9 showed a significant individual increase in 3MH:Cr during infection compared with only 4 in 3MH. This was due to a higher precision in 3MH:Cr despite the concomitant significant increase in urinary creatinine excretion.
Because of large stores of CO2 in different body tissues, metabolic change cannot be detected by measuring gas exchange until the CO2 stores have adapted to the new situation. Similarly, changes in the CO2 stores not due to metabolic alterations, may lead to error in gas exchange measurements. We studied CO2 production (VCO2) and oxygen consumption (VO2) in mechanically ventilated ICU patients, where CO2 stores were altered by: a) changing minute ventilation by 15%, b) reducing body temperature, and c) changing the level of sedation. Expired gases went through a mixing chamber and were analyzed continuously by a mass spectrometer. Signals from this instrument, together with gas-volume signals from the ventilator, were fed to a computer for calculation of VO2 and VCO2. Twenty to 120 min were required to reach a stable level, depending on the patient's size and circulatory response. Similar results were obtained by computer simulation using a five-compartment model of CO2 stores. These experiments indicate that measuring VO2 (for calculation of metabolic respiratory quotient [RQ]) in ventilated patients should occur after the patients maintain a 60-min period of stable body temperature and awareness. Ventilatory variables should not be changed substantially during the 90-min period before gas sampling. Cardiac output and muscle blood flow should not have changed 2 to 3 h before measuring RQ. If muscle blood flow is low, the stable periods for body temperature and ventilatory variables should be increased.
The aim of the study was to measure the plasma levels of lidocaine and prilocaine after dermal application of EMLA in infants and to evaluate whether this procedure increases the levels of methaemoglobin (Met-Hb). Two groups of infants, 3-6 (n = 12) and 6-12 months (n = 10) of age, were studied. In total, 2 ml of EMLA was applied to 4 x 4 cm of skin surface for 4 h and blood samples for detection of Met-Hb and plasma levels of local anaesthetics were taken at 0, 2, 4 and 8 h after the application. After removal of the cream the infants were operated mainly for minor procedures under general anaesthesia. The plasma concentrations of lidocaine and prilocaine were in all cases below toxic levels and there were only minor increases in Met-Hb in a few infants. In conclusion, EMLA can be used safely in infants above 3 months of age provided that the recommendations with regard to dose, application area and time are followed. The use of EMLA in smaller infants and in children taking other Met-Hb-inducing drugs needs further evaluation.
CO2 kinetics during CPR was investigated in 15 anesthetized piglets. BP, blood gases, and acid-base balance were monitored through catheters in the carotid artery and a central vein, as well as in cerebrospinal fluid. Cardiac arrest was induced by a transthoracic direct current shock. CPR was begun immediately by artificial ventilation and simultaneous external chest compressions. Epinephrine was administered after 8 min of CPR. One group (n = 5) of animals received no buffer treatment while another (n = 5) received an infusion of 75 mmol sodium bicarbonate and a third group (n = 5) received an equivalent amount of tris-buffer mixture. The results of these experiments, as well as previously described circulatory variables during CPR, were analyzed using a computer model describing the CO2 kinetics of the pig. Our main finding was that PaCO2 was positively correlated to cardiac output during CPR; improved cardiac output during CPR resulted in more efficient tissue CO2 elimination and was associated with increased survival rates. PaCO2 was also somewhat reduced by efficient alveolar hyperventilation. The arterial PCO2 and pH did not reflect the acid-base balance in peripheral tissues. During CPR, bicarbonate and tris-buffer mixture both quickly passed through the blood-brain barrier. When buffer treatment is indicated during CPR, a buffer which does not increase tissue PCO2 may be the drug of choice.
Twenty patients were studied over the first 4 post-operative days following abdominal aortic surgery. Ten patients had 93% of their non-protein energy as glucose and insulin was given to keep blood glucose below 10 mmol/l. The other 10 patients had 80% of non-protein energy as fat (Intralipid). Amino acids corresponding to 12 g of nitrogen were given in both groups. Gas exchange, nitrogen balance, phosphate balance, vanillylmandelic acid (VMA) excretion, 1- and 3-methylhistidine in urine, acute phase proteins, immunoglobulins and albumin were followed. Substrate utilisation was calculated from indirect calorimetry data and nitrogen excretion. Metabolism in the early post-operative phase was found to adapt to the nutrition regimen given even though the composition was extreme either in fat or carbohydrate content. The glucose-insulin regimen had a better nitrogen sparing effect and based on the difference in 3-methylhistidine excretion it is suggested that mainly protein muscle benefitted from this. Regardless of the TPN-regimen given, those patients whose RQ deviated the most from the average in their group had the highest nitrogen excretion. The two groups showed no differences in plasma proteins and catecholamine excretion.
In order to study how muscle glycogen is influenced by different nutritional regimens in the early post-operative period we took muscle biopsies from 20 patients preoperatively and on the fourth post-operative day after abdominal aortic surgery. Ten patients received 93% of non-protein energy as glucose, 7% as fat (Intralipid) and insulin was given to keep the blood glucose below 10 mmol/l. The remaining patients had 80% of non-protein energy as fat (Intralipid). Amino acids constituting 12 g of nitrogen daily were given to both groups. Daily measurements of gas exchange (oxygen uptake, CO2-production) were performed and from these data glucose balance was calculated as the difference between glucose intake and glucose expenditure. Muscle biopsies were analysed for glycogen, adenosine triphosphate, glucose-6-phosphate, lactate and citrate. We found that it was possible to maintain muscle glycogen stores at pre-operative levels with a glucose-insulin regimen. With the fat regimen there was a 31% decrease in muscle glycogen and two patients had a negative glucose balance despite the fact that 150 g of glucose were given. Average glucose balance throughout the study correlated positively with glucose intake. A significant correlation between glucose on the third day and change in muscle glycogen content was found. Muscle content of adenosine triphosphate, glucose-6-phosphate, lactate and citrate were similar in both groups.
Moderate per- and postoperative hypothermia initiates an increased metabolism in the postoperative period. The subsequent demands on oxygen transport may be critical in poor risk patients. Nineteen healthy young women with moderate hypothermia after abdominal surgery were studied for 2 h postoperatively with or without external heating from a heating ceiling. Central and peripheral temperatures, oxygen consumption, plasma catecholamines and shivering were measured. A method for continuous measurement of oxygen consumption and carbon dioxide production during spontaneous breathing is described. The results suggest that postoperative external heating decreases oxygen consumption, shivering and plasma catecholamine levels. At the same time, the comfort of the patient is increased considerably.
Heat loss during anaesthesia and surgery is a common problem. In patients with restricted cardio-pulmonary reserves this may endanger the postoperative outcome. In order to compare thermal balance we studied 25 men undergoing transurethral resection of the prostate (TURP), using either general anaesthesia (G.A.) or epidural analgesia (E.A.). Oxygen uptake, catecholamines, peripheral and central temperatures were followed in the per- and postoperative period. Heat production and total body heat were calculated from oxygen uptake and temperature measurements, respectively. Transurethral resection of the prostate resulted in a peroperative heat loss which was not influenced by the anaesthetic technique used and averaged 370 kJ during the first hour of surgery. G.A. reduced heat production while this was uninfluenced by E.A. After termination of general anaesthesia, oxygen uptake and plasma catecholamines increased, while no such changes could be detected using epidural analgesia. The ability to increase mean body temperature by increasing heat production was negatively correlated to age.
During whole body radiation therapy of children, treatment may be done in places not equipped with acceptable scavenging systems for anesthetic gases and where clinical observation of the patient may be impossible. In order to solve this problem, the authors have used a total intravenous (IV) anesthetic technique using midazolam, pancuronium, and fentanyl. With midazolam as the only hypnotic agent, the problem with scavenging is solved, and a computer simulation of the plasma concentration of midazolam is presented. A modified stethoscope for monitoring during radiation also has been developed. This anesthetic technique and the stethoscope have been used in seven children. The total IV anesthesia proved to be a useful method for children during whole body radiation. The modified stethoscope functioned very well and was a useful complement to the monitoring equipment.