Biomedical subjects

J Santesson

Publications and source records attributed to J Santesson.

13 recordsLinked to original sources

PubMed1979

Studies on intrapulmonary gas distribution in the normal subject. Influence of anaesthesia and artificial ventilation.

Intrapulmonary gas distribution, assessed by a multiple breath, nitrogen washout technique and expressed by the Fowler index NWOD, was studied in subjects with healthy lungs during spontaneous breathing while awake, and during mechanical ventilation under halothane anaesthesia. The distribution index rose from a mean of 32% awake to 56% during anaesthesia. An attempt was also made to differentiate between the contribution of gravitational (airway closure) and non-gravitational (diffuse airway obstruction) inhomogeneity of ventilation. This was accomplished by measurement of the slope of the alveolar plateau during a sinle breath nitrogen washout. The slope was similar awake and anaesthetized, and it increased equally under both conditions, when preinspiratory lung volume was stepped up from RV to CC, CC being the lung volume at which airways begin to close during expiration. NWOD was significantly correlated to the degree of airway closure, expressed as FRC-CC, and, less so, to inspiratory resistance. It is suggested that a less efficient ventilation distribution in anaesthetized normal subjects, as measured by NWOD, is caused rather by airway closure (gravitational inhomogeneity) than by diffuse airway obstruction (non-gravitational inhomogeneity of ventilation).

Adult↗

PubMed1979

Renal function and fluoride formation and excretion during enflurane anaesthesia.

Central circulation, renal function, and fluoride formation and excretion were studied in nine patients during enflurane anaesthesia and surgery. Cardiac output and mean systemic arterial pressure remained unchanged compared with preoperative control values. During anaesthesia and surgery, urine flow rate, inulin clearance, PAH clearance and fractional sodium excretion were 60, 65, 55, and 45% of control values, respectively. Mean peak plasma level of fluoride was 20.0 microM. It was reached 4 hours after termination of anaesthesia. Fluoride clearance (CF) decreased from 23.9 ml . min-1 to 2.7 ml . min-1 during anaesthesia. Postoperative, CF increased to 41.6 and 76.0 ml . min-1, respectively, during two consecutive measurement periods. There was no correlation between plasma fluoride levels and depression of any renal function variable.

Adult↗

PubMed1979

Fluoride kinetics and renal function during enflurane anaesthesia.

Renal function, fluoride formation and excretion were studied during and after enflurane anaesthesia in seven patients. During anaesthesia, urine flow rate, inulin clearance, PAH clearance and fractional sodium excretion were 13, 78, 65 and 49% of control values, respectively. Renal function was promptly restored postoperatively. Enflurane was metabolized to inorganic fluoride with a mean maximal serum level of 17.4 +/- 3.3 microM. Fractional fluoride excretion decreased during anaesthesia to 35% of the control value. Postoperatively, there was a highly significant correlation between the increase in fractional fluoride excretion and the rise in urinary pH during two consecutive 3-hour periods. It is suggested that tubular reabsorption of fluoride is inversely related to tubular fluid pH and that fluoride is reabsorbed by non-ionic diffusion.

Adult↗

PubMed1979

Airway closure during anesthesia: a comparison between resident-gas and argon-bolus techniques.

Airway closure was measured in awake and then anesthetized supine healthy subjects with the argon-bolus and the resident-gas (nitrogen) techniques simultaneously. The preinspiratory lung volume for the closing volume maneuver was varied from residual volume to closing capacity (CC). Comparative measurements were also performed in the upright and supine positions in awake subjects. Closing volume (CV) was consistently larger with the bolus technique in supine subjects both when awake and when anesthetized (difference between methods 0.1--0.2 l, P less than 0.01), whereas no difference between the methods was noted in upright subjects. The lower "nitrogen CV" in supine subjects may be due to a shorter vertical lung height with a smaller range of nitrogen concentrations, resulting in a less abrupt onset of phase IV (taken to indicate CV). CV was not significantly affected by the preinspiratory lung volume with either technique, and CC was unchanged when anesthesia was instituted. Functional residual capacity (FRC) was reduced with anesthesia (mean reduction: 0.6 l, P less than 0.01) and FRC-CC became negative in all subjects with either technique. This implies intermittent or continuous airway closure during anesthesia and the possibility of increased venous admixture.

Adult↗

PubMed1978

The effect of surgical stress on haemodynamics during neurolept anaesthesia.

The influence of surgical stress on haemodynamics during neurolept anaesthesia (NLA) was studied in ten patients, while they were awake, under anaesthesia prior to surgery and peroperatively. Systemic arterial, pulmonary arterial, right atrial and pulmonary capillary wedge pressures, as well as cardiac ouput (Qt), arterial oxygen content and mixed venous oxygen content, were measured. Systemic and pulmonary vascular resistances, arterial-venous oxygen content difference (AVD), oxygen consumption (VO2) and cardiac index (CI) were calculated. On institution of anaesthesia, CI fell from 2.8 +/- 0.1 1/min-m2 to 2.5 +/- 0.2 1/min-m2 and systolic arterial pressure (SBP) fell from 13.4 +/- 0.5 kPa to 10.2 +/- 0.3 kPa. During surgery CI rose to 3.3 +/- 0.1 1/min-m2 and SBP rose to 15.7 +/- 0.6 kPa. Prior to anaesthesia, AVD was 40.2 +/- 0.2 ml/l. Under anaesthesia prior to surgery, AVD did not change, but VO2 declined from 207 +/- 13ml/min to 171 +/- 10 ml/min. During surgery, AVD fell to 30.5 +/- 0.3 ml/l, while VO2 remained unchanged. It is concluded that NLA has a direct metabolic depressant effect and, in association with surgery, is accompanied by hyperkinetic circulation.

Adult↗

PubMed1978

Renal function during neurolept anaesthesia.

Renal function and central haemodynamics were studied in eight patients, without known histories of renal or cardiovascular disease, during and immediately after upper abdominal surgery under neurolept anaesthesia. Inulin and PAH clearance, fractional sodium and fractional osmolar excretion decreased, while fractional free water reabsorption increased under anaesthesia. Cardiac output, mean systemic arterial pressure and systemic vascular resistance remained virtually unchanged both per- and postoperatively. Renal haemodynamics were promptly restored postoperatively, while fractional sodium and fractional osmolal excretion were unaltered and antidiuresis increased. It is concluded that neurolept anaesthesia, as far as renal function is concerned, is well suited for the anaesthetic management of the poor-risk patient.

Abdomen↗

PubMed1978

Effects of enflurane on haemodynamics and oxygen uptake with special reference to the influence of surgical stress.

The influence on central haemodynamics of enflurane, in uniform anaesthetic concentration (1.5 MAC), was studied in 10 normocapnic patients undergoing upper abdominal surgery. The patients were studied awake, during anaesthesia prior to surgery, and during surgery. On institution of anaesthesia, cardiac output (QT) fell from 5.05 +/- 0.51 to 4.12 +/- 0.15 1/min and systemic vascular resistance (SVR) decreased from 2.36 +/- 0.22 to 1.93 +/- 0.18 kPa min. 1(-3). The arteriovenous oxygen content difference (AVD) did not change. On commencement of surgery, AVD diminished from 38.5 +/- 2.6 to 30.8 +/- 1.9 ml/min and QT rose to 5.82 +/- 0.46 1/min, while SVR remained unchanged. It is concluded that the fall in QT seen during enflurane anaesthesia is caused by a diminished tissue oxygen demand. It is also suggested that enflurane acts as an alpha-blocking agent.

Abdomen↗

PubMed1978

Influence of lung volume history on closing volume measurement during anaesthesia.

Airway closure measurements were made with the bolus technique on eight healthy subjects, who were in a supine position prior to and during anaesthesia. Measurements were made on an expiration following vital capacity (VC) and 30% VC. Closing volume (CV) was calculated prior to anaesthesia, and closing capacity (CC)--functional residual capacity (FRC) was estimated during anaesthesia. When measured from VC, CV was 703 +/- 20 ml (s.e. mean) and from 30% VC it was 440 +/- 51 ml (s.e. mean) (P less than 0.005) prior to anaesthesia. When measured from VC, CC--FRC was 370 +/- 34 ml (s.e. mean), and from 30% VC it was 343 +/- 37 (s.e. mean) (P greater than 0.05) during anaesthesia. It is concluded that volume history has little effect on CC measurement during anaesthesia and artificial ventilation, but a major influence on CC measurement in the conscious patient. Hence, it is suggested that CC, within the tidal range, is increased during anaesthesia.

Aged↗

PubMed1978

Pulmonary function in extreme obesity. Influence of weight loss following intestinal shunt operation.

Airway closure (CV), functional residual capacity (FRC) and the distribution of inspired gas (nitrogen washout delay percentage, NWOD %) and arterial oxygen tension (PaO2) was measured by standard electrodes in eight extremely obese patients before and after weight loss (mean weights 142 and 94 kg, respectively) following intestinal shunt operation. Prior to weight loss, airway closure occurred within a tidal breath in six out of eight patients. This was associated with a low FRC, and NWOD % was higher than in the non-obese. PaO2 was lower than normal. CV was unchanged after weight loss, but due to an increase in FRC, airway closure did not occur within a tidal volume and NWOD % was normal. PaO2 was also normal. It is concluded that weight reduction in extremely obese patients improves arterial oxygenation because of an increase in FRC, whereby CV no longer occurs within a tidal volume. Intrapulmonary gas mixing becomes more even.

Adult↗

PubMed1977

Studies on intra-pulmonary gas distribution in the extremely obese. Influence of anaesthesia and artificial ventilation with and without positive end-expiratory pressure.

Intrapulmonary gas distribution was studied in 10 extremely obese patients: (1) during spontaneous breathing awake; (2) during anaesthesia with controlled ventilation and zero end-expiratory pressure (ZEEP), and (3) as under (2) but with a positive end-expiratory pressure of approximately 15 cmH2O (PEEP). Gas distribution was assessed quantitatively by means of a multiple-breath nitrogen wash-out technique and subsequent fractional analysis, which permitted the calculation of nitrogen wash-out delay (NWOD). Gas distribution was also analyzed by means of a single-breath nitrogen wash-out in order to determine the slope of the "alveolar plateau." Gas distribution was within normal limits during spontaneous breathing, judged from multiple-breath as well as single-breath wash-out. With anaesthesia and ZEEP, NWOD was higher, indicating less efficient gas mixing, and the slope of the "alveolar plateau" was twice as steep as during spontaneous breathing. With PEEP, distribution of inspired gas improved (lowered NWOD and flatter slope). Theoretical considerations and clinical experiments led to the conclusion that uneven distribution in the anaesthetized obese is caused both by regional differences in the pulmonary time constants (as in obstructive lung disease) and by airway closure.

Adult↗

PubMed1976

Breathing mechanics, dead space and gas exchange in the extremely obese, breathing spontaneously and during anaesthesia with intermittent positive pressure ventilation.

Breathing mechanics and gas exchange were studied in 10 extremely obese subjects (average weight 138 kg) prior to and during anaesthesia with mechanical ventilation. Breathing mechanics were analysed from measurements of transpulmonary pressure (during anaesthesia, trans-chest wall pressure as well) inspiratory gas flow and tidal volume. Gas exchange was studied by analysing inspired and from the Bohr equation, and the division into anatomical and alveolar dead space was arrived at by capnography. The patients were anaesthetised with neuroltpt agents and ventilated with an air-oxygen mixture. Lung compliance during spontaneous breathing was below normal and decreased further during artificial ventilation. Chest wall compliance measured during anaesthesia was within normal limits. Lung resistance was above normal during spontaneous breathing and increased further during mechanical ventilation. Total dead space was normal during spontaneous breathing and increased moderately during artificial ventilation, the increment coming mainly from alveolar dead space. A moderate hypoxaemia was recorded during spontaneous breathing, and the alveolar-arterial oxygen tension difference was slightly elevated. During anaesthesia this difference was markedly greater. It is concluded that the most probable reason for the relative hypoxaemia is right-to-left shunting.

Adult↗

PubMed1976

Airway closure and distribution of inspired gas in the extremely obese, breathing spontaneously and during anaesthesia with intermittent positive pressure ventilation.

Airway closure (closing capacity, CC), FRC, total efficiency of ventilation (lung clearance index, LCI) and distribution of inspired gas (nitrogen washout declay percentage, NWOD) were determined by nitrogen washout techniques and arterial PO2and PCO2 measured by standard electrodes in 10 extremely obese subjects, prior to an during anaesthesia and artifical ventilation. CC was normal, but because of small FRC, airway closure occurred within a tidal breath in 9 out of 10 subjects during spontaneous breathing, when awake. PO2 was reduced, the hypoxaemia correlating to the magnitude of airway closure. LCI was normal, but NWOD was borderline. During anaesthesia, CC was unaltered by FRC was further reduced, so that in nine subjects sirway closure occurred above FRC and tidal volume together. A marked increase in relative hypoxaemia was recorded. LCI and NWOD rose, indicating less efficient and less even ventilation. It is concluded that airway closure reasonably explains the marked hypoxaemia in obese subjects during anaesthesia, and that it may also be the reason for the uneven distribution of inspired gas.

Adult↗

PubMed1976

Oxygen transport and venous admixture in the extremely obese. Influence of anaesthesia and artificial ventilation with and without positive end-expiratory pressure.

Eight extremely obese patients (mean weight 136 kg) were studied when awake and breathing air, and during anaesthesia with controlled ventilation (oxygen fraction in inspirate (FIO2): 0.5). During anaesthesia, the atients were first studied with zero end-expiratory pressure (ZEEP) ventilation. Then two different positive end-expiratory pressures (PEEP) were applied, 10 cmH2O and 15 cmH2O, in order to study the effect of an increase in functional residual capacity (FRC). Arterial oxygenation and oxygen availability, as well as cardiac output (QT) and venous admixture (QS/QT) were studied. With the institution of anaesthesia and ZEEP, the alveolar arterial oxygen tension difference (P(A-a)O2) rose from 3.5 +/- 1.1 to 28.4 +/- 2.6 kPa, and the oxygen availability fell from 1346 +/- 222 to 1039 +/- 239 ml/min, due to the additive effect of an increase in QS/QT from 10 +/- 4 to 21 +/- 5% and a fall in QT, from 7.7 +/- 1.2 to 5.5 +/- 1.1 1/min. With increasing levels of PEEP, despite a fall in P(A-a)O2, there was a reduction in oxygen availability. This was due to simultaneous reduction in QS/QT and QT. At a PEEP of 15cmH2O, the P(A-a)O2 was 21.2 +/- 7.1 kPa, oxygen availability 862 +/- 170 ml/min, QS/QT 13 +/- 4 and QT 4.4 +/- 0.6 1. It is concluded that PEEP ventilation significantly reduces QS/QT in extremely obese patients during anaesthesia and should be used in these patients if there is arterial hypoxemia despite a high FIO2.

Adult↗