Biomedical subjects

S Jakobson

Publications and source records attributed to S Jakobson.

At least 19 recordsLinked to original sources

PubMed2001

Continuous positive pressure ventilation during epidural blockade--effects on cardiac output distribution.

BACKGROUND: It has been shown that when cardiac output (CO) decreases during continuous positive pressure ventilation (CPPV), its regional distribution adapts with a favouring of vital organs. Does epidural blockade modify this adaptation? METHODS: Regional blood flows were assessed by the microsphere technique (15 microm) in 17 anaesthetised pigs during spontaneous breathing and CPPV with 8 cm H2O end-expiratory pressure (CPPV8) before and after epidural blockade. The block was induced at either the Th6-7 (Thep) or the L6-S1 (Lep) level with 1 ml of lidocaine 40 mg x ml(-1). RESULTS: When Lep was combined with CPPV8, mean arterial pressure and CO decreased significantly, and they decreased even more when combined with Thep. In contrast, the relative perfusion of the central nervous system, heart and kidneys remained stable during the four conditions studied. The adrenal perfusion during CPPV8 was obviated by epidural blockade. The absolute and relative perfusion of the skeletal muscle decreased during epidural blockade. The administered doses of epidural lidocaine did not affect blood flow in the spinal cord. CONCLUSIONS: The locally mediated nutritive vasoregulation of vital organs outweighed the sympathetic blockade induced by epidural blockade. During Thep blockade the animals were less capable of responding to the haemodynamic changes induced by CPPV8, probably due to the blockade of the cardiac part of the sympathetic nervous system.

Adrenal Glands↗

PubMed1998

Tissue perfusion in relation to cardiac output during continuous positive-pressure ventilation and administration of propranolol or verapamil.

BACKGROUND: Our objective was to determine whether administration of propranolol or verapamil modifies the hemodynamic adaptation to continuous positive-pressure ventilation (CPPV), in particular the regional distribution of cardiac output (CO). METHODS: General hemodynamics and regional blood flows assessed by microsphere technique (15 microns) were recorded in 16 anesthetized pigs during spontaneous breathing (SB) and CPPV with 8 cm H2O end-expiratory pressure (CPPV8) before and after intravenous administration of propanolol (0.3 mg.kg-1 followed by 0.15 mg.kg-1.h-1, n = 8) or verapamil (0.1 mg.kg-1 followed by 0.3 mg.kg-1.h-1, n = 8). RESULTS: CPPV8 depressed CO by 25% without shifts in its relative distribution with the exception of a noteworthy increase in adrenal perfusion. Propranolol increased arterial blood pressure, and due to a fall in heart rate, CO dropped by 25%. The kidneys and, to a lesser extent, the splanchic region and central nervous system received increased fractions of the remaining CO at the expense of skeletal muscle flow. Similar patterns were seen during SB and CPPV8 such that the combination of propranolol and CPPV8 depressed CO by 50%. The circulatory effects of verapamil were less evident but myocardial perfusion tended to increase. CONCLUSIONS: The combination of propranolol or verapamil with CPPV does not result in any specific hemodynamic interaction in anesthetized pigs, except that the combined effect of propranolol and CPPV may severely reduce CO.

Adrenal Glands↗

PubMed1997

Maintained cardiac output during positive end-expiratory pressure ventilation in open-chest pigs.

BACKGROUND: Does ventilation with positive end-expiratory pressure (PEEP) act to reduce cardiac output (CO) not only by impeding venous return but also by inducing myocardial depression? The present study was aimed to demonstrate the possible existence of this latter mechanism. METHODS: Eight pigs of Swedish native breed weighing 20-25 kg and 10-12 weeks old were anaesthetized, tracheotomized and connected to a volume-controlled ventilator. To prevent intrathoracic pressure from interfering with venous return, the heart and juxtacardiac vessels were exposed to atmospheric pressure by opening and retracting the chest and pericardium. Heart rate (HR), CO, stroke volume (SV), mean arterial (MAP), mean right (MRAP) and left (MLAP) atrial pressures were recorded before and after retransfusion of 500 ml of autologous blood. This procedure was carried out twice in each animal-during ventilation with zero and with 15 cm H2O of PEEP. RESULTS: Comparison of the two ventilation modes before volume load revealed negligible differences in HR, CO, SV, MAP, MRAP and MLAP. Moreover, the changes evoked by volume load were practically identical. CONCLUSIONS: Addition of PEEP to regular positive pressure ventilation does not induce any haemodynamically detectable myocardial depression in the piglet.

Animals↗

PubMed1995

Plasma exchange in patients with acute renal failure in the course of multiorgan failure.

Multiorgan failure (MOF) due to intoxication, trauma or sepsis in the progressive late stages always include acute renal failure (ARF). The prognosis of these patients is poor despite adequate dialysis. This study included 27 consecutive patients (20 men and 7 women, age range 15-77 years) with a rapid progress of MOF including ARF, who were treated by plasma exchange as an attempt to reverse the progress of MOF. Twenty-three of the patients suffered from a septic shock. Oliguria or anuria was present in all, dialysis was performed in 16 of them, and mechanical respiratory aid in 17. Plasma exchange was performed 1-10 times and almost exclusively by centrifuge technique, using albumin and/or liquid stored plasma (in a few cases fresh frozen plasma) as colloidal replacement fluid. Twenty-two patients survived (81%) and 5 patients died. The reasons of death were cerebral haemorrhagia, brain abscess, myocardial sudden death, relapsing sepsis from multiple hepatic abscesses and a not drained psoas abscess. All survivors could leave hospital recovered from renal failure with few other sequelae. The plasma exchange technique is easy to perform despite low blood pressures by using a vein to vein access. Plasma exchange, therefore, may be tried to reverse late stages of multiorgan failure.

Acute Kidney Injury↗

PubMed1994

Echocardiographic analysis of cardiac function during high PEEP ventilation.

OBJECTIVE: Does positive end-expiratory pressure ventilation (PEEP) deteriorate cardiac contractility? DESIGN: By means of echocardiography nine piglets were studies during ventilation with 0, 15 and 25 cmH2O (PEEP). Recordings were made before and after 500 ml of 6% dextran 70. MEASUREMENT AND RESULTS: Right and left ventricular end-diastolic diameters were plotted against the stroke volume determined by the thermodilution technique. By combining observations made before and after volume expansion during the different ventilation modes, a ventricular function curve was obtained. The slopes of the curves were similar during all three ventilation modes, both on the left and on the right side. CONCLUSION: This study indicates undisturbed myocardial contractility during PEEP ventilation. We infer that the cardiac output deterioration in the intact animal is caused entirely by impairment of venous return.

Animals↗

PubMed1994

PEEP ventilation does not cause humorally mediated cardiac output depression in pigs.

OBJECTIVE: This study was designed to see if humorally mediated negative inotropism contributes to the cardiac output (CO) depression seen during positive end-expiratory pressure (PEEP) ventilation. DESIGN: 8 pairs of piglets were used and a combined blood circulation was established between the two animals in each pair. One animal was ventilated with a PEEP of 15 cmH20 (donor) and the other was ventilated without PEEP (recipient). MEASUREMENT AND RESULTS: CO and stroke volume deteriorated in the donors by 32% and 44%, respectively, while no change was seen in the recipients. CONCLUSION: As humorally mediated negative inotropism during PEEP ventilation has earlier been demonstrated in dogs, the results suggest that this mechanism might be species-dependent.

Analysis of Variance↗

PubMed1994

The effect of peep-ventilation on cardiac function in closed chest pigs.

OBJECTIVE: Does ventilation with positive end-expiratory pressure (PEEP) depress myocardial contractility? DESIGN: Ten piglets were anaesthetized and prepared for the measurement of cardiac output (SV) and right (MRAPtm) and left (MLAPtm) mean transmural atrial pressure, the latter serving as indices of preload. 500 ml of autologous blood was re-transfused during intermittent positive pressure ventilation without PEEP (IPPV) and continuous positive pressure ventilation with 15 cm H2O PEEP (CPPV). MEASUREMENTS AND RESULTS: Right and left ventricular function curves were drawn by plotting MRAPtm and MLAPtm respectively versus the corresponding strokevolumes before and after re-transfusion. Similar inclinations were obtained during IPPV and CPPV on either side of the heart. CONCLUSIONS: Although the ventricular function curves during IPPV and CPPV covered partially different preload levels, the results suggest that CPPV i.e. PEEP does not affect myocardial contractility.

Animals↗

PubMed1994

Participatory control in chronic hospital-based hemodialysis patients.

The purpose of this study was to determine chronic hospital-based hemodialysis patients' perceptions of control over selected aspects of hemodialysis care and to compare the patients' ratings with the global ratings of nurses caring for them. Two versions of a 14-item Hemodialysis Control Questionnaire (HCQ) were developed, one for patients (HCQ-P) and one for nurses (HCQ-N). Forty-seven patients and 32 nurses rated both perceived and desired control for each aspect of hemodialysis care on the HCQ. Reasons for their ratings were elicited and recorded. High test-retest reliability was established for both perceived and desired control on the HCQ-P and the desired control component of the HCQ-N. Patients rated their overall perceived and desired control as moderate, likewise the nurses' global score for desired control was rated as moderate. Item-by-item analysis revealed that nurses overestimated the patients' desired control over technical aspects of care but underestimated the patients' desire for more control over nontechnical aspects of care. The content analysis of the verbatim responses supported the quantitative findings.

Adult↗

PubMed1989

Is it really a placenta previa?

Transvaginal sonography was compared to the traditional transabdominal sonography for diagnosing placenta previa. There was no vaginal bleeding in the 55 women studied following vaginal examination. The exact location of the internal os was diagnosed in all women by the vaginal route, and only in 36 of the 55 by abdominal scanning. Transvaginal sonography correctly diagnosed 39 out of the delivered 45 women, whereas transabdominal sonography only did so in 20 of the 45 cases. These results suggest that transvaginal sonography for the diagnosis of placenta previa is safe and superior to transabdominal sonography.

False Positive Reactions↗

PubMed1989

True shunt in relation to venous admixture in an experimental porcine model of early ARDS.

Using the multiple inert gas elimination technique, ventilation/perfusion (V/Q) relationships were studied in an experimental porcine model of the early Adult Respiratory Distress Syndrome (ARDS) to establish the nature of the increased venous admixture. Six animals served as controls and revealed no major changes apart from a 10% decrease in cardiac output during the 4-h observation period. All control animals showed a shift to a higher mean V/Q of perfusion (Qmean) and a maintained log standard deviation (QSD) throughout the experiment. The distribution was unimodal and centered around a V/Q ratio of 1.0. The share of perfusion to V/Q ratio less than 0.005 (i.e. true shunt, Qs) remained unchanged at 6-7% of cardiac output. Nine animals, given a continuous infusion of E. coli endotoxin, showed a significant decrease of 53% in cardiac output (Qt) at 4 h. Mean pulmonary artery pressure (MPAP) showed a 2-phase reaction with a peak level at 0.5 h, and a second gradual increase from 2 h onwards. Venous admixture doubled at 0.5 h, after which it declined but remained elevated throughout the observation period. All endotoxin animals showed a shift in perfusion to a higher Qmean with a significantly wider QSD at 0.5, 2 and 4 h. The distribution was unimodal and centered around a V/Q ratio of 1.0. True shunt was unchanged at 6-7% of cardiac output throughout the study. The increase in venous admixture in this experimental ARDS model is consequently explained by the widening of the V/Q scatter and is due to a perfusion shift to lower ventilation/perfusion ratios rather than to an increase in true shunt.

Animals↗

PubMed1988

Vaginal ultrasound for diagnosis of placenta previa.

Transvaginal sonography was compared with transabdominal sonography in 35 women with suspected placenta previa. The transvaginal sonographic technique did not result in vaginal bleeding in any of the patients. The internal os and its relationship to the location of the placenta were visualized by transvaginal sonography in all patients, but only in 24 patients (69%) by transabdominal sonography. Transvaginal sonography ruled out placenta previa in 13 cases thought to be placenta previa by abdominal sonography. The transvaginal diagnosis in these 13 patients was confirmed at delivery. Thirty-four of the 35 women have been delivered. The diagnosis at delivery confirmed the transvaginal sonographic diagnosis in 29/34 cases and the transabdominal diagnosis in 16/34. Transvaginal sonography did not predict the delivery diagnosis in five patients who were erroneously believed to have placenta previa by both sonographic techniques.

Female↗

PubMed1987

Central haemodynamics and regional blood flows during thoracic epidural analgesia combined with positive pressure ventilation. An experimental study in the pig.

Cardiac output, central haemodynamics and regional blood flows were studied in pigs. The microsphere technique was used for blood flow determinations. Measurements were made during spontaneous breathing (SB) and during intermittent positive pressure ventilation with 0.8 kPa (8 cmH2O) positive end-expiratory pressure (8 PEEP) before and during thoracic epidural analgesia (TEA). TEA in the pig caused reduced cardiac output due to reduced heart rate with maintained stroke volume. During TEA there was also a reduction of mean arterial blood pressure which ran almost parallel to the decrease in cardiac output with maintained systemic vascular resistance during SB and at 8 PEEP. The distribution of cardiac output was basically the same during SB and at 8 PEEP as it was before TEA. However, myocardial blood flow and relative perfusion decreased during TEA, both during SB and at 8 PEEP. TEA also reduced spinal cord blood flow within the thoracic region during SB and at 8 PEEP.

Analgesia↗

PubMed1987

The effects of alpha adrenergic blockade on central haemodynamics and regional blood flows during positive pressure ventilation. An experimental study in the pig.

The effects of alpha receptor blockade on cardiac output distribution in pigs were studied. Recordings were made during spontaneous breathing (SB), during ventilator treatment with 8 Pa positive end-expiratory pressure (8 PEEP), after alpha blockade during SB (SB-alpha) and at 8 PEEP (8 PEEP-alpha). The microsphere method was used for blood flow determinations. The animals received either 5 ml.kg-1.h-1 (Group A) or 10 ml.kg-1.h-1 (Group B) of fluids. In Group A on SB-alpha, CO was maintained due to tachycardia but mean arterial pressure (MAP) decreased, renal blood flow and urine production decreased. At 8 PEEP-alpha, CO decreased despite increased heart rate (HR), MAP decreased alarmingly, renal blood flow decreased, urine production ceased and cerebral blood flow decreased, reflecting failing autoregulation. In Group B, CO increased during SB-alpha, SVR decreased, myocardial blood flow increased and organ blood flows were otherwise unchanged. At 8 PEEP-alpha, MAP, SVR, renal, pancreatic and splenic blood flows decreased in Group B. Gastric, intestinal and muscular blood flows were unchanged at 8 PEEP-alpha in Group B which is interpreted as an effect of the alpha blockade. In both groups peripheral arterio-venous shunting increased after alpha blockade.

Adrenergic alpha-Antagonists↗

PubMed1987

Functional effects of phosphoenolpyruvate and ATP on pig hearts in cardioplegia and during reperfusion. An in vivo study with cardiopulmonary bypass.

The effects of phosphoenolpyruvate (PEP) and ATP in cardioplegia and during early reperfusion were studied in pigs. Twenty pigs divided into three groups were placed on cardiopulmonary bypass and subjected to 2 h of hypothermic cardioplegic arrest. Group I (n = 7) served as a control. In group II (n = 7) PEP (14.4 mM) and ATP (0.067 mM) were added to the cardioplegic solution. Group III (n = 6) was given PEP (28.8 mM) and ATP (0.134 mM) with 500 ml of isotonic NaCl in the aortic root during early reperfusion. All animals in group III were weaned from bypass compared with 6 of 7 in group I and 5 of 7 in group II. Forty minutes after ischemia group III was assessed to be the only group with an unchanged aortic flow and stroke volume. The total peripheral resistance and arterial pressure were reduced in this group. The results demonstrate that PEP and ATP administered during reperfusion have a beneficial effect and that this may be exerted both on the myocardium and on the peripheral vessels.

Adenosine Triphosphate↗

PubMed1984

Assessment of lung water content by roentgen videodensitometry.

In 17 anesthetized and mechanically ventilated pigs, different degrees of lung injury were induced by iv infusion of oleic acid (mean dose 0.1 ml/kg). The change in radiologic density of the chest was measured by a videodensitometer before and 4 h after oleic acid infusion. The lungs were then removed for determination of the wet/dry weight ratio (WW/DW). The change in radiologic density was significantly correlated to WW/DW (r = .87) and to the changes in end-inspiratory pressure (r = .80), mean pulmonary arterial pressure (r = .77) and venous admixture (r = .79), but not to changes in the oncotic-hydrostatic pressure gradient of the lungs (r = .46). Roentgen videodensitometry appears to be a useful method for assessing changes in extravascular lung water content.

Absorptiometry, Photon↗

PubMed1982

Effects of positive end-expiratory pressure on cardiac output distribution in the pig.

Cardiac output (CO) and the blood flow to the heart, cerebellum, kidney, pancreas, spleen and skeletal muscle were studied in 20 pigs during spontaneous breathing (SB) and intermittent positive pressure ventilation (IPPV) with a positive end-expiratory pressure (PEEP) of 0, 8, 16 or 24 cmH2O. Microspheres (15 micrometers) labelled with either 85-sr or 141-Ce were used. Injection of microspheres labelled with one of the isotopes was given during SB (all pigs) and with the other isotope during IPPV with PEEP of 0, 8, 16 or 24 cmH2O (five pigs at each level). CO decreased by 11% during IPPV with PEEP of 0 and 31%, 53% and 66% during PEEP of 8, 16 or 24 cmH2O, respectively. Mean arterial blood pressure was fairly well maintained in all groups except the group with PEEP of 24 cmH2O. The perfusion of the six organs deteriorated, but when taken as fractions of CO measured at the same time, the blood flow to the heart, cerebellum and kidney increased with increasing airway pressure, while that to the pancreas, spleen and skeletal muscle decreased. The vascular resistance of the three former organs did not change, while in the latter it increased markedly. It is concluded that when CO decreases as a result of positive pressure ventilation, a redistribution takes place, mainly due to vascular constriction in skeletal muscle, which acts to preserve the blood flow to vital organs.

Animals↗

PubMed1981

Influence of plasma oncotic pressure on lung water accumulation and gas exchange after experimental lung injury in the pig.

In 18 anaesthetized and artificially ventilated pigs, oleic acid was infused intravenously in order to induce a lung injury characterized by increased lung water content, decreased compliance and a ventilation/perfusion disturbance. After a stabilizing period, half of the animals (group P) underwent repeated plasmapheresis, which halved their plasma oncotic pressure (POP). The rest of the animals were bled and re-transfused with the shed blood, thus serving as a control group. In both groups, care was taken to keep the mean left atrial pressure as constant as possible. During plasmapheresis and "shamapheresis", there was no significant increase in venous admixture (F102 0.21 and 0.6) in either of the groups. At the end of the study, end-inspiratory pressure, dead space/tidal volume ratio and wet/dry lung weight ratio (WW/DW) were significantly higher in group P. Venous admixture and WW/DW correlated significantly with pulmonary arterial pressure and calculated pulmonary capillary pressure, but not with POP or POP minus pulmonary arterial occlusion pressure. It is concluded that reduction of plasma oncotic pressure may increase the lung water content in previously injured lungs, but this extra water accumulation does not necessarily impair oxygenation in the lungs.

Acid-Base Equilibrium↗

PubMed1981

The effect of positive end-expiratory pressure on central haemodynamics in the pig.

The effect on central haemodynamics of a stepwise increase in airways pressure from spontaneous breathing (SB) to intermittent positive pressure ventilation with a positive end-expiratory pressure (PEEP) of 0, 8, 16 and 24 cmH2O was studied in eight pigs under ketamine anaesthesia. Compared with SB, cardiac output (CO) was reduced by 12, 36, 50 and 64% at the respective ventilator settings. The transmural pressures of the right and left atrium, measured as the difference between atrial and pleural pressure, both decreased with increments in airway pressure. At a PEEP level of 24, there was a threefold increase in pulmonary vascular resistance. This increase was secondary to the decrease in CO and no signs of CO deterioration due to the increased right ventricular afterload were found. When 250 ml of dextran 70 was administered at a PEEP level of 24 and the airway pressure was then released stepwise, the left ventricular function curve improved, disclosing a relative myocardial failure at the highest PEEP levels. It is concluded that the principal causative mechanisms in CO reduction due to increased intrathoracic pressure is a decrease in preload to the right ventricle. At high PEEP levels there are also signs of myocardial depression.

Airway Resistance↗