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Biomedical subjects

U Sjöstrand

Publications and source records attributed to U Sjöstrand.

At least 19 recordsLinked to original sources
PubMed2001

Optimal positive end-expiratory pressure (PEEP) settings in differential lung ventilation during simultaneous unilateral pneumothorax and laparoscopy: an experimental study in pigs.

BACKGROUND: A combined thoraco-laparoscopic technique for esophageal resection is technically possible, but it requires special attention to ventilation. The positive insufflation pressure normally used in laparoscopy will, when communication between thorax and abdomen is established, create a pneumothorax. METHODS: We performed an experimental study of differential lung ventilation with different levels of positive end-expiratory pressure (PEEP) settings during thoraco-laparoscopy in anesthetized pigs. RESULTS: Positive pressure insufflation of carbon dioxide (CO2) resulted in elevated pulmonary capillary wedge pressure, hypercarbia, and respiratory acidosis. Hypoxemia, however, developed only at lower settings of PEEP. Heart rate, mean arterial pressure, and cardiac output remained relatively stable. CONCLUSION: Pneumopleuroperitoneum under positive CO2 insufflation pressure had adverse effects on blood gases. Hypercarbia, respiratory acidosis, and hypoxemia were early manifestations that occurred even in the presence of hemodynamic stability. The application of PEEP equal to or above CO2 insufflation pressure improved blood gases; in particular, the hypoxia could be avoided. No beneficial effects of differential lung ventilation were documented.

Animals↗
PubMed2001

Effects of sustained pressure application on compliance and blood gases in healthy porcine lungs.

BACKGROUND: Short periods of sustained increase in airway pressures (Press(up)) are believed to re-open lung areas that collapsed upon induction of anaesthesia. Recruitment of alveolar surface is usually assessed in terms of changes in the pressure-volume (PV) curve. The purpose of this study was to analyse PV-curves before and after a Press(up) and to ascertain whether such changes are compatible with the concept of recruitment of lung volume. METHODS: During ketamine anaesthesia, 12 healthy piglets were subjected to a Press(up) with end-expiratory pressure (PEEP) of 12 cmH2O and end-inspiratory pressure of 40 cmH2O. Before and after Press(up), PV-curves were obtained from a slow insufflation of 630 ml at zero PEEP (ZEEP). RESULTS: Compliance was non-linear both before and after Press(up) increasing up to 300 ml and sharply decreasing thereafter. After Press(up), the entire compliance curve was shifted to a higher absolute level. Up to 100 ml and a pressure level corresponding to the lower inflection point on the PV-curve (LIP), compliance was higher before Press(up). No effects on blood gases could be observed. CONCLUSION: If the similar shape of the compliance curve corresponds to a similar chain of re-opening and overdistension events, this would imply that all volume gained by Press(up) is lost within 10 min, without explaining the higher absolute compliance following Press(up). We speculate that a) re-opening of rapidly collapsing small airways determines the initial compliance increase; b) the lower compliance after Press(up) until LIP indicates reduced intratidal re-opening of lung regions; and c) changes in bronchomotor tone induced by Press(up) raise the absolute compliance, with a similar scenario of alveolar and small airway recruitment now taking place but at different degrees of airway stiffness.

Airway Resistance↗
PubMed2000

[Ventilation in ARDS: respirator, prone position, NO or artificial lung].

This review discusses the treatment of impaired gas exchange in acute respiratory distress syndrome (ARDS) using conventional ventilation, the open lung approach, prone position, nitric oxide (NO) inhalation and extracorporeal membrane oxygenation (ECMO). It is concluded that ventilation with high inspiratory pressures or volumes should be avoided, and that the open lung approach should be used as the first step. If this does not lead to satisfactory results, prone positioning is recommended, and if life-threatening hypoxemia persists, ECMO could be considered. NO inhalation is not recommended.

Adult↗
PubMed2000

Impact of different inspiratory flow patterns on arterial C02-tension.

Ventilation with decelerating inspiratory flow is known to reduce the dead space fraction and to decrease PaCO2. Constant inspiratory flow with an end-inspiratory pause (EIP) is also known to increase the removal of CO2. The aim of the study was to elucidate the effect of the pause/no-flow period while both the pattern and rate of inspiratory flow was unchanged, and when the lung was ventilated with sufficient PEEP to prevent end-expiratory collapse. Surfactant depleted piglets were assigned to decelerating or constant inspiratory flow with 24 breaths per minute (bpm) or 12 bpm, or to constant flow, without and with an end-inspiratory pause of 25%. By adding an EIP the total time without active inspiratory flow of the respiratory cycle was kept unchanged. Gas exchange, airway pressures, functional residual capacity (using sulfurhexafluoride) and haemodynamics (thermo-dye indicator dilution technique) were measured. Irrespective of ventilatory frequency, PaCO2 was lower and serial dead space reduced with decelerating flow, compared with constant inspiratory flow. With an end-inspiratory pause added to constant inspiratory flow, serial dead space was reduced but did not decrease PaCO2. The results of this study corroborate the assumption that total time without active inspiratory flow is important for arterial CO2-tension.

Animals↗
PubMed1988

Hemodynamic effects of colloid concentration in experimental hemorrhage: a comparison of Ringer's acetate, 3% dextran-60, and 6% dextran-70.

Hemodynamic effects of iso-oncotic 3% dextran-60, 6% dextran-70, and Ringer's acetate were compared in 28 male pigs (25 to 30 kg) subjected to experimental trauma and hemorrhage. The animals were kept anesthetized with 75% N2O/25% O2, 0.8% halothane. Hemodynamic and respiratory conditions were allowed to stabilize for one hour preoperatively (baseline data). After surgical trauma (arthroplasty), three 0.5 L of arterial blood samples were withdrawn and replaced with autologous red cells mixed with one liter of 3% dextran-60 in one group 1 (n = 9), one liter of 6% dextran-70 in group 2 (n = 10), and 3 L of Ringer's acetate in group 3 (n = 9). Pulmonary capillary wedge pressure (WP) was kept at baseline level for a further 10 h with infusion of the respective fluid; for this purpose, groups 1 through 3 needed additional infusions of 0.8 +/- 0.3, 0.5 +/- 0.4, and 5.3 +/- 3 (SD) L, respectively. Group 1 showed the highest jejunal capillary blood flow at 10 h and the lowest intragroup variations in hemodynamic and respiratory data. Group 2 had the highest pulmonary arterial pressures and group 3 had the lowest colloid oncotic and arterial BP and left ventricular volume indices. In group 3, the Hct and serum albumin indicated insufficient plasma volume replacement. This group had a significantly larger (p less than .05) amount of tissue water in skin, skeletal muscle, and jejunum than the other groups; no significant difference in lung or heart muscle water was found between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Influence of naloxone infusion on analgesia and respiratory depression following epidural morphine.

The influence of two different concentrations of iv naloxone infusion on the analgesia and adverse effects of epidural morphine were compared in a double-blind, placebo-controlled study. Forty-five patients undergoing gallbladder surgery were provided postoperative analgesia by 4 mg epidural morphine; they then received an iv infusion over a 12-h period consisting of either 5 micrograms X kg-1 X h-1 naloxone, 10 micrograms X kg-1 X h-1 naloxone, or saline. Pain relief was assessed by hourly visual analog scoring (VAS) and by direct questioning of the patient. Requirement of additional analgesia was noted. Respiratory frequency was monitored every 15 min and arterial blood gases were analyzed every 2 h for 24 h. Peak expiratory flow (PEF) was recorded 6 and 24 h postoperatively. Steady-state kinetics of naloxone were determined by a modified radioimmunoassay (RIA) method. All patients had good to excellent postoperative pain relief. Naloxone, 5 micrograms X kg-1 X h-1, did not appear to have any effect on epidural morphine analgesia. However, naloxone infusion at the rate of 10 micrograms X kg-1 X h-1 reduced the duration of analgesia by about 25%, and more frequent injections of epidural morphine were required to give effective analgesia. Complete reversal of analgesia was not seen in any patient. A dose-related stimulatory effect on respiratory frequency was noted in the groups receiving naloxone. PaCO2 values also were better in these groups as compared to values in the placebo group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Three per cent dextran-60 as a plasma substitute in blood component therapy. I. An alternative in surgical blood loss replacement.

Microaggregate-poor erythrocyte concentrate with 3% dextran-60 as a plasma substitute was compared with microaggregate-poor whole blood for replacement of intra-operative and immediately postoperative blood loss. Sixty patients undergoing total hip arthroplasty randomly received either of these two forms of therapy. In accordance with the clinical routine of our orthopedic department, an infusion of 500 ml of 6% dextran-70 (Macrodex) was given as thrombo-prophylaxis in both groups. Use of 3% dextran-60 as a plasma substitute in blood component therapy for surgical hemorrhage of up to 50% of the calculated blood volume caused no increase in bleeding tendency or frequency of postoperative hematoma compared with whole blood replacement. Plasma protein levels were low immediately postoperatively in patients given the dextran, but from the 4th postoperative day onward there was no difference between the groups. Applied in clinical practice, this would be efficient in saving plasma for other urgent purposes.

Aged↗
PubMed1985

Three per cent dextran-60 as a plasma substitute in blood component therapy. II. Comparative studies on pre- and postoperative blood volume.

Microaggregate-poor erythrocyte concentrate with 3% dextran-60 as a plasma substitute was compared with microaggregate-poor whole blood for replacement of intra-operative blood loss. Their blood volume-conserving effects were studied by sequential blood volume determination with radioactive technetium (99mTc) in 19 patients undergoing total hip arthroplasty. Pre-operatively there was no difference in blood volume between the groups. Immediately after surgery and on the 2nd postoperative day there was no difference in total blood volume. Blood component therapy with 3% dextran as a plasma substitute is an efficient principle for intra-operative blood loss replacement at hip operations.

Aged↗
PubMed1984

Comparison of intramuscular and epidural morphine for postoperative analgesia in the grossly obese: influence on postoperative ambulation and pulmonary function.

In a randomized double-blind study of thirty grossly obese patients undergoing gastroplasty for weight reduction, the effects of intramuscular and epidural morphine were compared as regards analgesia, ambulation, gastrointestinal motility, early and late pulmonary function, duration of hospitalization, and occurrence of deep vein thrombosis in the postoperative period. The patients were operated on under thoracic epidural block combined with light endotracheal anesthesia. A six-grade scale was devised to quantify postoperative mobilization. A radioactive isotope method using 99mTc -plasmin was employed to detect postoperative deep vein thrombosis. For 14 hr after the first analgesic injection, respiratory frequency was noted every 15 min and arterial blood gases were measured hourly. Peak expiratory flow was recorded daily until the patient was discharged from hospital. Spirometry was performed the day before and the day after surgery. Plasma concentrations of morphine were measured after both intramuscular and epidural administration. Both intramuscular and epidural morphine gave effective analgesia, but the average dose of intramuscular morphine was up to seven times greater than that required by the epidural route. A larger number of patients receiving epidural morphine postoperatively were able to sit, stand, or walk unassisted within 6, 12, and 24 hr, respectively. Being alert and more mobile as a result of superior postoperative analgesia from epidural morphine, patients in this group benefited more from vigorous physiotherapy routine, which resulted in fewer pulmonary complications. Furthermore, earlier postoperative recovery of peak expiratory flow and bowel function presumably contributed to a significantly shorter hospitalization in patients receiving epidural morphine. There was no evidence of prolonged respiratory depression in this high-risk category of patients. The 99mTc -plasmin tests revealed no significant difference between the two groups.

Adult↗
PubMed1983

Effects of hypo-, normo-, and hypercarbia in dogs with acute cardiac tamponade.

The hemodynamic effects of changes in PaCO2 during intermittent positive pressure ventilation (IPPV) were studied in nine dogs with acute cardiac tamponade. During steady state light thiopental anesthesia, measurements were performed during hypocarbia (24.0 +/- 2.6), normocarbia (40.4 +/- 2.4), and hypercarbia (56.8 +/- 3.1 mm Hg; mean +/- SD). The study was carried out at a standardized level of cardiac tamponade that gave a 60% reduction in cardiac output (CO) at normocarbia. Changes in airway pressure were avoided by adding CO2 to the inspiratory gas to obtain the desired PaCO2. Hypercarbia increased pericardial pressure 2-4 mm Hg and significantly decreased CO. During hypocarbia CO increased as pericardial pressure decreased 3-6 mm Hg. These findings are the reverse of changes seen when tamponade is not present. The changes in pericardial pressure most likely influence myocardial tone and cardiac volume and, thus, CO. The results suggest that patients with cardiac tamponade requiring general anesthesia should not breathe spontaneously if there is any danger of respiratory depression and hypercarbia.

Acute Disease↗
PubMed1981

Postoperative pain relief by epidural morphine.

Postoperative pain relief was studied in 280 patients undergoing various kinds of surgery, e.g., thoracic, upper and lower abdominal, perineal, obstetric, and orthopedic. Morphine, 2 or 4 mg, was given after surgery through an indwelling epidural catheter. Excellent analgesia was noted in 87% of patients; only 3.5% of patients were dissatisfied. A single injection gave complete pain relief for the entire postoperative period in 30% of cases; in the remaining patients the mean duration of analgesia was 10.7 hours (SD +/- 4.3). Plasma morphine concentrations recorded after 2-mg doses suggest a regional spinal action as the basis for the long duration of analgesia, although the initial effect after 4-mg doses might well include systemic responses due to rapid vascular uptake of morphine from the epidural space. Peak expiratory flow (PEF) measurements and arterial blood gas analyses showed no significant early postoperative respiratory depression. Absence of sedation, orthostatic hypotension, respiratory depression, and motor paralysis facilitated early ambulation with less risk for postoperative respiratory complications. It is concluded that 2-mg doses of epidural morphine give good analgesia of long duration despite low plasma levels. After upper abdominal and thoracic surgery higher doses (4 mg) may be necessary in healthy patients. Elderly and frail patients appear to be sensitive to epidural morphine and doses in excess of 2 mg should be avoided regardless of the type of surgery. With this dose schedule we have not encountered delayed respiratory depression.

Adolescent↗