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Biomedical subjects

O Stenqvist

Publications and source records attributed to O Stenqvist.

At least 55 records · Page 3Linked to original sources
PubMed1995

Conversion of inhaled nitric oxide to nitrate in man.

1. Nitric oxide (NO) is potentially useful as a selective vasodilator drug in infants and adults with pulmonary hypertension. In vitro and in vivo observations demonstrate that NO may be converted to nitrate in the blood, to be further excreted into the urine. The aim of the present study was to assess quantitatively the importance of this pathway for inhaled NO in human subjects. 2. Healthy subjects inhaled 15NO (25 p.p.m.) for 1 h. The plasma and urine levels of 15NO3- were followed for 2 and 48 h, respectively. 3. The measured retention of 15NO in the lungs was 224 +/- 13 mumol, corresponding to 90 +/- 2% of the inhaled amount. Plasma 15NO3- increased during the inhalation of 15NO, to about 15 mumol l-1, and fell when inhalation of 15NO was terminated. 4. Urinary excretion of 15NO3- during the first 24 h after inhalation was 154 +/- 12 mumol. During the following 24 h another 8 +/- 2 mumol of 15NO3- appeared in the urine. 5. We conclude that conversion of inhaled NO to nitrate is a major metabolic pathway in man, covering more than 70% of its inactivation. The metabolic fate of the remaining NO inhaled requires further study.

Administration, Inhalation↗
PubMed1994

Complement system activation during orthotopic liver transplantation in man. Indications of peroperative complement system activation in the gut.

Sixteen patients with acute and chronic liver disease undergoing OLT were studied regarding the role of the liver and the gut in complement activation. Also, the relation between complement activation and clinical manifestations during the liver transplantation reperfusion period was investigated. Blood samples for measurement of complement anaphylatoxin C3a (C3a), complement anaphylatoxin C5a (C5a), and terminal C5b-9 complement complex (TCC) were taken simultaneously from the central venous catheter and the radial arterial line before starting the operative procedure, 1 min before declamping, and 1-2 min, 5 min, 30 min and 6-12 hr after declamping. Simultaneous blood sampling from the radial arterial line, central venous catheter, portal vein, and hepatic vein was performed 1-2 min and 5 min after completed unclamping. Elevated plasma levels of C3a and TCC were found upon reperfusion, while C5a levels remained unchanged throughout the operation compared with the preoperative levels. The levels of C3a in the portal vein were higher compared with the levels in the simultaneously obtained samples from the radial artery. The results indicate complement cascade activation located to the gut during the reperfusion phase of OLT. Seventy-five percent of the patient studied suffered from the postreperfusion syndrome, indicated by profound hypotension upon reperfusion of the transplanted liver. There was a significant correlation between high concentration of C3a anaphylatoxin and development of profound hypotension.

Adult↗
PubMed1994

Effects of hyperventilation on the inspiratory to end-tidal oxygen difference.

We assessed the inspiratory to end-tidal oxygen difference (PIO2-PE'O2) during voluntary hyperventilation in 10 healthy male volunteers. The oxygen difference was measured with a fast-response paramagnetic differential oxygen sensor. As simultaneous changes in metabolism and cardiac output also influence (PIO2-PE'O2), oxygen uptake was measured with indirect calorimetry and non-invasive transthoracic electrical bioimpedance was used for measurement of cardiac output. After a rest period, subjects were instructed to double their minute ventilation volume (VE) and after 5 min triple their resting VE for another 5 min. (PIO2-PE'O2) decreased from a zero value of 6.4 kPa to 3.9 kPa at 5 min (P < 0.01) and 2.9 kPa at 10 min (P < 0.01). At 15 min (i.e. 5 min after the end of hyperventilation) there was an increase in (PIO2-PE'O2) to 8.3 kPa (P < 0.05). Regression analysis between (PIO2-PE'O2) (kPa) and VE (litre m-2 min-1) gave the formula: (PIO2-PE'O2) = 1/(0.059 + 0.034 VE), r = -0.92, n = 158. Oxygen uptake and cardiac output did not change significantly during hyperventilation, but decreased in the post-hyperventilation period. An oxygen difference of more than 8 kPa was associated with significant arterial desaturation.

Adult↗
PubMed1994

Nitrous oxide uptake during spontaneous and controlled ventilation.

The rate of uptake of nitrous oxide was studied in 40 orthopaedic patients anaesthetised with either enflurane or isoflurane in nitrous oxide and with either spontaneous or controlled ventilation. A variant of the Douglas bag method was used in combination with low fresh gas flows to a circle system. There were no significant differences in nitrous oxide uptake between the groups and the uptake rates followed 'the square root of time concept', with an overall best fit curve of 1080.t-0.505 ml.70 kg-1 x min-1. During spontaneous ventilation, the nitrous oxide uptake rate was similar or even higher than the corresponding rate during controlled ventilation, in spite of lower minute volumes.

Adult↗
PubMed1994

Predictable nitrous oxide uptake enables simple oxygen uptake monitoring during low flow anaesthesia.

The uptake rate of oxygen and nitrous oxide were studied during low flow anaesthesia with enflurane or isoflurane in nitrous oxide with either spontaneous or controlled ventilation. The excess gas flow and composition were analysed. The nitrous oxide uptake rate was in agreement with Severinghaus' formula VN20 1000.t-0.5. The composition of excess gas was predictable and the following formula for oxygen uptake could be derived: VO2 = VfgO2-0.45 (VfgN2(0)-(kg: 70.1000.t-0.5)) where oxygen uptake rate (VO2, ml.min-1) equals oxygen fresh gas flow (VfgO2) minus 0.45 times the difference between the fresh gas flow of nitrous oxide (VfgN2O), ml.min-1 and estimated uptake of nitrous oxide. The equation assumes constant inspired gas concentrations of 30% oxygen and 65-70% nitrous oxide. The oxygen uptake rates calculated from this formula were in good agreement with measured uptake rates. Thus, continuous monitoring of oxygen uptake rates is possible by using only reliable flowmeters and analysis of inspired oxygen concentration.

Adult↗
PubMed1993

Sampled gas need not be returned during low-flow anesthesia.

OBJECTIVE: The purpose of this investigation was to study the N2 flux between the patient and the breathing circuit, and the excess gas during N2O anesthesia with the low, fresh gas flow technique. METHODS: Forty patients were studied. After a 6-minute high, fresh gas flow denitrogenation period, the O2 fresh gas flow was set at about 4 ml/kg/min and the N2O fresh gas flow was set to maintain an inspired O2 fraction of 0.30. The excess gas flow and N2 excretion were measured by a variant of the Douglas bag method. RESULTS: The mean inspired N2 concentration reached a peak of 5.9% at 40 minutes. The estimated mean N2 excretion was 39 ml/min at 10 minutes, declining to 18 ml/min at 60 minutes. A calculation of N2 homeostasis during closed-circuit anesthesia based on the results of the patient study indicated that sampling for gas analysis actually reduces the gas costs if the sampled gas is scavenged instead of returned to the circle system, since intermittent flushing with high, fresh gas flow for denitrogenation is unnecessary in the former situation. CONCLUSIONS: Regardless of the fresh gas flow used, sampled gas need not be returned during N2O anesthesia.

Adult↗
PubMed1993

Nitrous oxide elimination and diffusion hypoxia during normo- and hypoventilation.

We studied the elimination rate of nitrous oxide in 36 patients undergoing orthopaedic surgery. They were allocated randomly to one of six groups which differed in time of nitrous oxide exposure and mode of ventilation. In order to simulate recovery conditions, nitrous oxide administration was discontinued after 30, 60 or 120 min of exposure. Either normoventilation or hypoventilation was used. The mean excretion rate was 1 litre min-1 at 1 min, declining to 100 ml min-1 at 30 min, with relatively small effects of different modes of ventilation and times of exposure. In spite of an FIO2 of 0.30, there were significant decreases in SpO2 during both normo- and hypoventilation. The smallest end-tidal oxygen concentrations were reached at 10-15 min in the groups with hypoventilation, after 1 or 2 h of nitrous oxide exposure.

Adolescent↗
PubMed1993

Complement activation during liver transplantation.

Twelve patients with end-stage liver disease undergoing liver transplantation were studied regarding complement activation and formation of anaphylatoxins (C3a and C5a) and terminal C5b-9 complement complexes (TCC) after reperfusion of the grafted liver. Blood samples for complement variables (C1INH, C3, C4, C5, C3a, C5a, and TCC) were drawn preoperatively, before the anhepatic phase, 1 min before, and 2, 15, and 60 min after the start of reperfusion of the grafted liver. Activation of complement was observed during the operation. The C1INH, C3, C4, and C5 plasma concentrations decreased during the entire operation while the anaphylatoxin C3a and the terminal C5b-9 complement complex increased after the reperfusion of the grafted liver. Activation of complement with the formation of biologically active substances like anaphylatoxins and terminal C5b-9 complement complexes may be one explanation for circulatory complications often seen in patients undergoing orthotopic liver transplantation.

Adult↗
PubMed1993

Evaluation of a new system for ventilatory administration of nitric oxide.

A new system for delivery of nitric oxide (NO) to inspiratory gas consisting of two mass flow regulators and a soda-lime absorber for scavenging of nitrogen dioxide (NO2) is described. The system was evaluated using three different techniques for NO analysis (infrared, chemiluminescence and electro-chemical fuel cell technique). The electro-chemical fuel cell was less sensitive to humidity in the sample and is suitable for clinical routine use. The infrared analyser was very sensitive to humidity and the gas sample must be dried by silica gel, which absorbs NO2 and will cause falsely low NO2 values. NO2 was analysed with ultra-violet methodology. NO2 is highly toxic and the highest recommended occupational health and safety level for inhalation is 5 ppm. The highest values of NO2 in our system were detected before the absorber in the inspiratory limb of the breathing system, being 5 ppm at 100% oxygen and 100 ppm NO using "infant" respiratory settings (3 l/min in ventilation, frequency of 30/min). The corresponding value for "adult" respiratory settings (10 l/min in ventilation, frequency of 15/min) was 3.2 ppm. The absorber reduced these levels to well below 1 ppm. When clinically relevant levels of NO were used (20 ppm), no NO2 could be detected after the absorber, irrespective of oxygen concentration in the breathing gas. It was observed that gas cylinders with NO mixed in nitrogen may initially have a high NO2 concentration (around 12 ppm) and should be flushed thoroughly before use.

Evaluation Studies as Topic↗
PubMed1993

[Respiratory gas exchange. Anesthesia with enflurane or isoflurane in nitrous oxide during spontaneous and controlled ventilation].

The estimation of oxygen consumption and carbon dioxide elimination is essential for predicting the metabolic activity and needs of any patient having anaesthesia. During anaesthesia oxygen consumption can be measured and compared to a predicted value. However, oxygen uptake is affected by anaesthetic agents, which complicates the interpretation of measured oxygen uptake rate. The purpose of this study was to investigate whether there are any differences in respiratory gas exchange during anaesthesia with enflurane and isoflurane and also to assess the effects of spontaneous versus controlled ventilation. METHODS. Forty orthopedic patients were randomized to enflurane or isoflurane anaesthesia in nitrous oxide with either spontaneous or controlled ventilation. A fresh low-gas-flow technique was used. Inspiratory oxygen and end-tidal carbon dioxide concentrations and expiratory minute ventilation were measured in a circle absorber system between the y-piece and the endotracheal tube with a sampling analyser. Between the mixing box and the absorption canister, carbon dioxide concentration was continuously measured. The carbon dioxide elimination was calculated from mixed expired concentration and expiratory minute ventilation. Excess gas was collected every 10 min in a non-permeable mylar plastic bag connected to the excess valve. The excess gas flow was calculated and the oxygen uptake rate was assumed to be the difference between the oxygen fresh gas flow and the oxygen excess gas flow. RESULTS. The grand mean oxygen uptake rate was 2.5 ml.kg-1 x min-1 or 100 ml.min-1 x m-2. There were no statistically significant differences in oxygen uptake between enflurane and isoflurane anaesthesia or between spontaneous and controlled ventilation. The mean oxygen uptake rate at 10 min was between 2.0 and 2.2 ml.kg-1 x min-1 in all groups. At 30 min the mean oxygen uptake rates were 2.6 to 2.8 ml.kg-1 x min-1. Carbon dioxide elimination was closely associated with expired minute ventilation, with a carbon dioxide excretion of about 30 ml per litre gas exhaled, irrespective of ventilatory mode employed.

Adult↗
PubMed1992

Isolated hyperthermic liver perfusion with cytostatic-containing perfusate activates the complement cascade.

Eight patients with advanced liver malignancy undergoing isolated hyperthermic liver perfusion with melphalan and cisplatin were studied with regard to complement activation and formation of anaphylatoxins (C3a and C5a) and terminal C5b-9 complement complexes (TCCs). Blood samples for complement variables (C1-INH, C3, C4, C5, C3a, C5a and TCCs) were taken before surgery, 1 min before the start of perfusion, 1, 2 and 3 h after the start of perfusion, and 24 h after operation. Samples were drawn from the perfusate 1 h after the start of perfusion. Activation of complement was observed during perfusion. Raised plasma concentrations of C3a and TCCs were recorded and high levels of C3a and TCCs were found in the perfusate. In vitro tests indicated that melphalan and cisplatin may activate complement. This activation occurred at 37 and 42 degrees C but was more pronounced at 42 degrees C.

Adult↗
PubMed1992

Inspiratory to end-tidal oxygen difference during nitrous oxide anaesthesia.

In order to evaluate the value of the inspiratory to end-tidal oxygen concentration difference (Io2-E'o2) as a monitor during general anaesthesia, we studied 40 orthopaedic patients allocated randomly to four groups: anaesthesia with enflurane or isoflurane in nitrous oxide with either spontaneous or controlled ventilation. (Io2-E'o2) followed an asymptotically increasing curve because of decreasing uptake of nitrous oxide. At 1 h, (Io2-E'o2) approached the end-tidal carbon dioxide concentration (E'o2). During spontaneous ventilation, (Io2-E'o2) correlated best with E'co2. During controlled ventilation, there was a negative correlation between (Io2-E'o2) and nitrous oxide uptake rate. Changes in oxygen uptake rate were reflected in (Io2-E'o2), provided that the total ventilation volume was constant and the nitrous oxide uptake rate approached steady state conditions.

Adult↗
PubMed1992

Aspects on diagnosis and treatment of the foregut carcinoid syndrome.

Eight patients with the foregut carcinoid syndrome (two gastric and six bronchial primary tumors) are reported. The patients presented with complex clinical symptoms including ectopic production of adrenocorticotrophic hormone and growth hormone-releasing factors. The most alarming symptoms were facial flush and edema, accompanied by severe bronchoconstriction, which easily was misinterpreted as asthmatic attacks. Conventional bronchodilatory drugs may be potentially dangerous in these patients, in whom combined blockade of histamine receptors and treatment with cortisone and octreotide are recommended. Owing to the patients' age and general condition individualized long-term therapy was instituted. Surgical therapy under optimal protection by drugs can be of substantial value also in patients with advanced disease. One patient with life-threatening hormonal symptoms underwent hyperthermic perfusion of the liver with cytotoxic drugs, resulting in good palliation.

Aged↗