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Biomedical subjects

O Stenqvist

Publications and source records attributed to O Stenqvist.

At least 73 records · Page 4Linked to original sources
PubMed1991

Metabolic gas exchange during aortocoronary bypass surgery using a double pump system and mechanical ventilation. A comparison between indirect calorimetry and invasive blood gas measurements using Fick's principle.

Oxygen uptake and carbon dioxide excretion during aorto-coronary bypass surgery were studied in seven patients by indirect calorimetry and compared to blood-gas based measurements. Medium-high dose fentanyl, droperidol and midazolam were used for maintaining anaesthesia. During the period of extracorporeal circulation no external oxygenator was used. Circulation was maintained by two pumps by-passing the left and right heart respectively and the patient's lungs were ventilated with O2/N2 using a Servo 900C ventilator. For indirect calorimetric measurements gas concentrations were analysed by Beckman instruments and gas volumes were measured by the Servo 900C ventilator. Oxygen uptake and carbon dioxide excretion decreased by 31% and 39%, respectively. For invasive measurements during extracorporeal circulation, arterial and venous blood gases and pump flow were used. Using pump flow instead of cardiac output when calculating oxygen uptake circumvented errors in thermodilution measurements. There was a good correlation (r = 0.88) between the invasive and the indirect calorimetric measurements. Further, there was a good correlation between naso-pharyngeal temperature and indirect calorimetric measurements of oxygen uptake (r = 0.87).

Blood Gas Analysis↗
PubMed1991

Management of disseminated midgut carcinoid tumours.

Forty-one patients with disseminated midgut carcinoid tumours were treated over a 6-year period according to a strict programme including primary surgical treatment. In 10 patients, a total remission of the disease was obtained. Patients with bilobar hepatic disease had ischaemic treatment of their liver metastases by hepatic arterial embolisation after primary surgical and medical treatment (low dose octreotide). Thus, by combining surgical, radiological and medical treatment modalities, we wanted to offer these patients optimal palliation. This treatment programme resulted in good symptomatic relief in all patients accompanied by a marked reduction in 5-hydroxyindoleacetic acid (5-HIAA) levels. At recurrence of symptoms in combination with rising 5-HIAA levels, embolisation was repeated. Ten of the treated patients have deceased during the observation period, but only 5 from their carcinoid disease.

Adult↗
PubMed1990

Validation of a system for measurement of metabolic gas exchange during anaesthesia with controlled ventilation in an oxygen consuming lung model.

An oxygen consuming lung model was used for evaluation and validation of a technique for metabolic gas exchange measurements during controlled ventilation. The technique comprised a Servo 900 C ventilator (Siemens) and separate oxygen and carbon dioxide analysers (Beckman). Measurements of oxygen consumption and carbon dioxide production were made either by measuring inspired and expired ventilation and gas fractions in these volumes or by measuring gas fractions and calculating expired ventilation from inspired by transformation (Haldane). Irrespective of the FIO2, measured values correlated well with lung model settings: measured values were within +/- 2% of simulated. When Haldane transformation was used with an FIO2 of 0.5 there was a significant underestimation of oxygen consumption. Carbon dioxide production values correlated well irrespective of the FIO2 used or method of measurement of ventilation volume. Metabolic gas exchange measurements by measuring both inspired and expired ventilation volumes may be used when inert gases are not in equilibrium, for example during nitrous oxide anaesthesia.

Anesthesia↗
PubMed1990

Metabolic gas exchange during nitrous oxide anaesthesia with controlled ventilation.

A system for metabolic gas exchange has been used during nitrous oxide-opioid anaesthesia incorporating a Servo Ventilator 900 C and external analysers for oxygen and carbon dioxide. Oxygen consumption and carbon dioxide excretion were calculated as differences in content between inspired and expired minute ventilation. Nitrous oxide uptake was calculated similarly, assuming it was the only other gas present in addition to oxygen and carbon dioxide. The mean value for oxygen consumption was 3.25 ml kg-1 min-1, declining by 8% during the 2 h of anaesthesia. The formula for the best fit curve of nitrous oxide uptake was 18.3 . t-0.48 ml kg-1 min-1 when FIN2O was 0.7. To simplify measurement procedures and avoid measurements of expiratory volume, we also calculated metabolic gas exchange when expiratory minute ventilation was expressed as a function of inspiratory minute volume and nitrous oxide uptake. The latter value was obtained from the overall best fit curve for nitrous oxide uptake.

Adult↗
PubMed1990

Complement activation and reinfusion of wound drainage blood.

Eighteen patients undergoing total hip replacement (n = 13) or knee arthroplasty (n = 5) due to osteoarthritis or osteoarthrosis were prospectively studied in an investigation of complement activation and anaphylatoxin release in association with reinfusion of aspirated wound blood. Twelve of the patients needed blood transfusions and received an average of 390 +/- 75 ml (+/- SD) of autologous blood within 45 min. Plasma complement components, anaphylatoxins, and inhibitors were studied 1 min before and 15 min after the start of and 15 min after the completion of autologous transfusion. Samples also were taken from the collected blood, before and after passing it through a microporous filter. Blood gases and systemic complement samples were drawn simultaneously. There were no significant changes in systemic complement variables before, during, or after transfusion of autologous blood. However, in the aspirated blood, increased concentration of anaphylatoxins (C3a and C5a) and terminal complement complexes (TCC) were present (P less than 0.001). There were no differences observed between samples drawn before and after filtration of the blood. The concentration of C5 was less in the collected blood than in the systemic blood (P less than 0.05). No changes in blood gases were observed. This study demonstrated that postoperatively salvaged whole blood underwent anaphylatoxin formation and complement activation. However, after reinfusion of this blood, neither systemic complement activation nor clinical complications were observed.

Adult↗
PubMed1989

The circle system as a humidifier.

In a laboratory model, humidity output was investigated in relation to the design of a circle absorber system. A 70-kg subject was simulated with fresh gas flows of 0.5, 2 or 5 litre min-1. Different circle systems, absorption canisters and tubings were studied. It was found that both the type of circle system (according to Eger's classification) and the size of the absorption canister, influenced the humidity of inspired gases. Coaxial tubing only moderately increased the humidity. If a fresh gas flow of 0.5 liter min-1 was used, optimum moisture contents were attained, irrespective of the circle system tested. Low fresh gas flows, a small canister and an Eger A type circle system, were factors which increased humidification.

Absorption↗
PubMed1989

Low-flow anaesthesia does not increase the risk of microbial contamination through the circle absorber system.

In the circle absorber system, a decrease in fresh gas flow means a higher degree of rebreathing, and, consequently, a higher temperature and humidity within the system. With our present hygienic routines, the circle system tubings are changed and decontaminated once daily. Thus, the same circle system is used for several patients each day. In order to evaluate whether the risk of bacterial contamination increased with the introduction of low-flow anaesthesia, 122 patients anaesthetized with either a low-flow technique (less than 1.5 l fresh gas flow/min) or with medium fresh gas flows (3-6 l/min) were studied. Bacterial samples were taken preoperatively from the oropharynx and postoperatively from five locations in the circle system. The patients were studied postoperatively for signs of respiratory tract infection. There were few positive bacteria cultures from the tubings in the circle system, regardless of fresh gas flow. No pathogens were found in the inspiratory tubings and no cases of postoperative respiratory tract infection could be related to bacterial spread from the anaesthesia machine. There were no indications that the present hygienic management was insufficient for the medium- or the low-flow circle system techniques.

Adolescent↗
PubMed1989

Whole body gas exchange: amino acid and lactate clearance as indicators of initial and early allograft viability in liver transplantation.

A method for the rapid assessment of liver allograft circulation and function after liver transplantation is described. In 12 patients undergoing liver transplantation continuous recording of whole body energy production was made on the basis of gas exchange measurements during the surgical procedure. Oxygen consumption decreased rapidly by 25% when the blood supply to the native liver was interrupted. After the anhepatic period, there was a sharp increase of oxygen consumption with successful reperfusion of the allograft. Carbon dioxide production fell by 14% and returned to preanhepatic values after successful declamping. In two cases with suboptimal reperfusion the return of gas exchange values was slow and incomplete. Results from the studies of whole body energy production were compared with biochemical measurements. No significant accumulation of amino acids occurred during the anhepatic period, but in the two patients with incomplete revascularization, clearance of amino acids, after the anhepatic phase, was impaired and plasma amino acids accumulated. The same pattern was found for plasma lactate levels. By the techniques described in this article, rapid and reliable assessment of initial and early graft function in hepatic transplantation is possible. This is of great value for the intraoperative and early postoperative assessment and planning of surgical and anesthesiologic strategies.

Adolescent↗
PubMed1989

Humidity of the Bain and circle systems reassessed.

The humidity outputs of the Bain circuit, a traditional non-coaxial Mapleson D system, and a circle system with and without a soda lime absorber were evaluated in a laboratory model simulating a 70-kg subject. The breathing systems were tested with tidal volumes of 0.35 and 0.70 L and frequencies of 10-20 breaths/min to maintain an end-expiratory CO2 of 4.5%. There were small differences in inspiratory gas humidity between the Bain and the non-coaxial Mapleson D system. With a fresh gas flow of 5 L/min in the Bain circuit, the humidity was 9.8-16.5 mg H2O/L depending on tidal volume and respiratory frequency. The humidity output of the circle absorber system with fresh gas flows of 0.5 or 2 L/min was 21.6-25.2 mg H2O/L at 60 min. Therefore, this study does not support previous studies, which propose that the Bain circuit has superior humidifying properties compared with those of the circle absorber system.

Anesthesiology↗
PubMed1988

Comparison of costs of different anaesthetic techniques.

The costs of anaesthetic drugs, intravenous agents as well as gases, were studied for different anaesthetic techniques in a medium-sized operative procedure, cholecystectomy. Three anaesthetic breathing systems were used: a non-rebreathing system, a circle absorber system with medium fresh gas flows of 3-6 l/min, and a low-flow circle system. Anaesthesia without volatile inhalation agents used with a low-flow technique was the least expensive, and anaesthesia with isoflurane in a non-rebreathing system was the most expensive. The costs of anaesthesia without volatile inhalation agents in a non-rebreathing system, enflurane anaesthesia in a circle system with medium fresh gas flows, and isoflurane anaesthesia with low-flow technique were similar.

Aged↗
PubMed1988

Gaseous homeostasis during low-flow anaesthesia.

The object of this clinical study was to investigate the circle system gas homeostasis during low-flow anaesthesia using a technique designed to keep a constant inspired oxygen fraction of 0.30. Denitrogenation was adequately accomplished with mask preoxygenation, 10 l/min, for 1 min and an initial fresh gas flow of 5 l/min for 6 min after intubation. There was no need to wash out accumulated nitrogen at intervals, since the already low nitrogen concentration in the system tended to decrease after 1 h. The fresh gas flow of nitrous oxide to oxygen ratio and the inspiratory to end-expiratory oxygen concentration difference both reflected the uptake of nitrous oxide. The calculated rates of uptake of nitrous oxide, a subject of controversy, were in accordance with those found by Severinghaus and Barton & Nunn.

Adult↗
PubMed1988

SMS 201-995 and provocation tests in preparation of patients with carcinoids for surgery or hepatic arterial embolization.

Patients with midgut carcinoids undergoing surgical resection or ischemic treatment of hepatic metastases by embolization are at risk for development of carcinoid crises due to release of hormonally active tumor products. Eight such patients were treated on nine separate occasions with increasing subcutaneous doses of a synthetic somatostatin analogue (SMS 201-995) 4 days prior to surgery or hepatic arterial embolization. The patients were tested by pentagastrin provocation and simultaneous measurement of serotonin (5-HT) levels in peripheral blood before and after prophylactic treatment, to evaluate the efficacy of SMS 201-995. The provoked release of 5-HT was markedly diminished, and the basal levels of 5-HT were markedly reduced in patients with high initial levels. During surgery or embolization both SMS 201-995, as well as ketanserin, a 5-HT2 receptor blocker, were given. With this combined treatment all patients were hemodynamically stable during surgery or embolization. During embolization the arterial levels of 5-HT increased only moderately, while urinary excretion of 5-hydroxyindoleacetic acid remained unchanged despite a proven adequate embolization. Two patients were operated on without previous treatment with SMS 201-995; both developed severe crises at induction of anesthesia, but IV SMS 201-995 rapidly reversed the bronchoconstriction and facial flush and gradually restored arterial blood pressure, even though cardiac output remained depressed for a prolonged period. The crisis reaction correlated well with high circulating levels of 5-HT, but after treatment with SMS 201-995 these levels were still high.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Preservation of humidity and heat of respiratory gases during anaesthesia--a laboratory investigation.

Humidification and heating of anaesthetic gases are desirable to prevent respiratory tract damage and a fall in body temperature during operative procedures. Numerous studies on the humidity and temperature of inspiratory gases in different breathing systems for anaesthesia have been carried out, but comparisons are difficult since different methods have been used. In this laboratory set-up we studied a non-rebreathing system with and without humidifiers and a circle absorber system with low (0.5 l/min) or medium (5 l/min) fresh gas flows regarding their ability to heat and humidify anaesthetic gases. The humidity of inspired gases was acceptable in the non-rebreathing system using either a Bennett Cascade humidifier or disposable humidifiers and in the circle absorber system using a fresh gas flow of 5 l/min or less. The temperature of the inspired gases was highest with the Bennett Cascade humidifier, followed by the low-flow circle system. The circle absorber system used with low fresh gas flow gave higher inspiratory gas temperature and humidity than the non-rebreathing system with a good disposable humidifier.

Anesthesia, Inhalation↗