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Biomedical subjects

R G Hahn

Publications and source records attributed to R G Hahn.

At least 73 records · Page 4Linked to original sources
PubMed1997

Dilutional hypocalcaemia from urological irrigating fluids.

A normal serum calcium concentration is essential for cardiovascular and muscular function. The hypocalcaemia-inducing potential of urological irrigating fluids was studied in 7 young men and in 10 prostatectomy patients. A total of 48 intravenous infusions of 1,000 ml of various irrigating fluids showed consistently that dilution of the serum calcium concentration occurs. The magnitude of the dilution was in between that recorded for albumin and for sodium. The free calcium concentration, however, correlated closely with the serum sodium level. These results suggest that dilutional hypocalcaemia can be expected to coexist with hyponatraemia in patients who develop the transurethral resection syndrome.

Adult↗
PubMed1997

Cardiac output and ethanol monitoring of fluid absorption.

The purpose of this experimental study was to find out whether central haemodynamic activity influences the precision of the ethanol method used to monitor fluid absorption during endoscopic surgery. Today, the nomograms used together with this monitoring method indicate that increasing breath ethanol values reflect progressively larger absorption volumes regardless of the haemodynamic situation. Cardiac output was measured by ultrasound-Doppler and compared with the concentrations and pharmacokinetics of ethanol in the breath during and after 13 intravenous (i.v.) infusions of 15 mL kg-1 of irrigating fluid containing 1% of ethanol in nine healthy male volunteers. The results show that the peak ethanol concentration increases with cardiac output. This can probably be explained by the shorter time needed for the blood to reach and to return from well perfused tissues, thereby prolonging the apparent rate of distribution to poorly perfused tissues. It is concluded that a hyperkinetic circulation causes the ethanol monitoring method to indicate larger absorption volumes.

Adult↗
PubMed1997

Glycine 1.0% versus glycine 1.5% as irrigating fluid during transurethral resection of the prostate.

OBJECTIVE: To evaluate the potential benefits of reducing the glycine concentration from 1.5% to 1.0% in the irrigating fluid used during transurethral resection of the prostate (TURP) when 1% ethanol is used as the tracer of absorption. PATIENTS AND METHODS: The effect of 1% ethanol on the tendency for blood to haemolyse was tested in vitro and the optical condition of the irrigating fluids were studied during 10 TURPs. The breath ethanol level was monitored during 423 operations where these fluids were used in a randomized double-blind study. The incidence of 13 symptoms was recorded in the 77 patients who absorbed irrigating fluid. RESULTS: Ethanol slightly lowered the tendency for blood to haemolyse. Reducing the glycine concentration did not alter the optical conditions during TURP. The incidence of symptoms increased significantly as more glycine solution was absorbed, arterial hypotension and nausea being the most usual. Bradycardia, prickling skin sensations and feelings of uneasiness were less common when 1.0% glycine was used, but the choice of irrigating fluid had no effect on the total incidence of symptoms. CONCLUSION: We found no clear advantage in lowering the glycine concentration of the irrigating fluid used during TURP.

Absorption↗
PubMed1997

Free and total prostate-specific antigen serum concentrations do not help to detect prostate cancer in patients with urinary outlet obstruction.

OBJECTIVES: To determine whether different molecular forms of prostate-specific antigen (PSA) obtained before transurethral resection of the prostate (TURP) indicate the presence of prostate cancer. PATIENTS AND METHODS: The free, total and free-to-total PSA levels were measured in 261 patients scheduled for TURP, 20 of whom had known prostate cancer. The tissue histology was compared with the PSA levels and the patients were followed for 5 years. RESULTS: Prostate cancer was detected in 23 of the patients (9%) who were thought to have benign disease. Normal ranges for the distribution of the PSA levels were established based on the patients with a benign histology, but these ranges did not detect most of the unknown cancers. The sensitivity of the total PSA test in detecting cancer was 38% and the specificity 90%. The discrimination was no better when considering the free fraction or the free-to-total PSA level. However, none of the 14 patients whose cancer was missed showed general progression of the disease during the 5-year follow-up and only one died from prostate cancer. In contrast, eight of the 20 patients with a known prostatic malignancy showed general progression, and six died from the disease. CONCLUSION: PSA testing of patients with outlet obstruction often failed to detect prostate cancer, but the prognosis was moderately good in those patients in whom it was missed.

Adult↗
PubMed1997

Modelling the volume of expandable body fluid spaces during i.v. fluid therapy.

We have developed mathematical models to represent the changes in volume of fluid spaces associated with i.v. administration of a crystalloid solution. Input data for parameter estimations were dilution of blood, measured as reduction of blood haemoglobin concentration. The models were based on the assumption that the body strives to maintain volume homeostasis of fluid spaces and that the rate of restoration is a function of deviation from resting volume. Two models were derived; the first had a single fluid space into which fluid was administered and from which fluid left, the other model had a second fluid space communicating with the first. These models may be useful in the description and analysis of the effects of i.v. fluid therapy.

Adult↗
PubMed1997

Volume kinetics of Ringer's solution in female volunteers.

The kinetics of crystalloid solutions in humans have not been adequately described previously. Therefore, we measured blood haemoglobin concentration during and for 120 min after i.v. infusion of 25 ml kg-1 of Ringer's acetate solution over 15, 30, 45 and 80 min, and 12.5 ml kg-1 over 30 min in six adult female volunteers. The dilution-time profiles were analysed according to a new kinetic model adapted for fluid spaces. Volume expansion produced by Ringer's solution approached steady state in an exponentially decaying manner when plasma volume had increased by approximately 550 ml. The size of the fluid space expanded by Ringer's solution was only 4.8 litre (95% confidence interval 3.8-5.8 litre) except for the fastest infusion, where it averaged 9.0 litre. The rate of fluid elimination could be predicted as the product of plasma dilution and a constant averaging 95 (95% confidence interval 68-122) ml min-1.

Adult↗
PubMed1997

Plasma dilution and the rate of infusion of Ringer's solution.

Changes in the volume of the fluid space expanded by i.v. infusion of Ringer's acetate solution have been analysed recently using mathematical models. Data obtained by such analyses allow simulation of the dilution of the plasma volume during infusion of the solution at different rates. To obtain basic kinetic data for such simulations, the plasma dilution-time curves were measured during and after i.v. infusion of Ringer's solution 25 ml kg-1 over 30 min in 15 healthy male volunteers (mean age 31 yr) and over 30, 45 and 80 min in six females (mean age 32 yr). Based on these experiments, nomograms were constructed from which the rate of infusion of Ringer's solution and the infusion time required to obtain a defined plasma dilution in both males and females can be estimated together with the infusion rate needed to maintain the dilution at the level reached.

Adult↗
PubMed1997

Volume kinetics of Ringer solution, dextran 70, and hypertonic saline in male volunteers.

BACKGROUND: A knowledge of the distribution of different fluids given by intravenous infusion is basic to the understanding of the effects of fluid therapy. Therefore, a mathematical model was tested to analyze the volume kinetics of three types of fluids. METHODS: The authors infused 25 ml/kg of Ringer acetate solution, 5 ml/kg of 6% dextran 70 in 0.9% NaCl, and 3 ml/kg of 7.5% NaCl over 30 min in 8 male volunteers aged from 25 to 36 years (mean, 31 years) and measured the changes in total hemoglobin, serum albumin, and total blood water over time. The changes were expressed as fractioned dilution and then plotted against time. The curves were fitted to a one-volume and a two-volume model, which allowed an estimation of the size of the body fluid space expanded by the fluid (V) and the elimination rate constant (k(r) to be made. RESULTS: The changes in blood water concentration indicated a mean size of V of 5.9 1 (+/- 0.8, SEM) for Ringer's solution, 2.6 (+/- 0.3) 1 for dextran, and 1.2 (+/- 0.1) 1 for hypertonic saline. The corresponding values of k(r) were 94 (+/- 42), 12 (+/- 6), and 30 (+/- 4) ml/min, respectively. Blood hemoglobin indicated a degree of dilution similar to that indicated by blood water. Serum albumin indicated a more pronounced dilution, which resulted in a larger expandable volume and a greater mean square error for the curvefitting. The larger volume obtained for serum albumin can probably be explained by a loss of intravascular albumin into the tissues along with the infused fluid. CONCLUSIONS: The distribution of intravenous fluids can be analyzed by a kinetic model adapted for fluid spaces, but slightly different results are obtained, depending on the marker used to indicate dilution of the primary fluid space. Analysis and simulation of plasma volume expansion by this model is a tool that can help the anesthetist to better plan fluid therapy.

Adult↗
PubMed1997

Central and regional hemodynamics during acute hypovolemia and volume substitution in volunteers.

OBJECTIVES: To study the central and regional hemodynamics and oxygen consumption during acute hypovolemia and volume replacement with crystalloid and colloid solutions. DESIGN: Prospective, randomized, laboratory investigation. SETTING: Clinical physiology department at a university hospital. SUBJECTS: Eighteen healthy male volunteers, between 21 and 35 yrs of age (mean 26). INTERVENTIONS: Catheters were inserted in the cubital vein, brachial artery, pulmonary artery, thoracic aorta, right hepatic vein, and left renal vein for measurements of systemic arterial and pulmonary arterial pressures, total and central blood volumes, extravascular lung water, and the splanchnic (liver) and renal blood flow rates. The exchange of respiratory gases was measured, using the Douglas bag technique. Measurements were made before and after a venesection of 900 mL and again after the subjects had been randomized and received volume replacement with either 900 mL of Ringer's acetate solution 900 mL of albumin 5%, or 900 plus 900 mL of Ringer's solution. MEASUREMENTS AND MAIN RESULTS: Withdrawal of 900 mL of blood decreased cardiac output and the splanchnic and renal blood flow rates by between -16% and -20%. The oxygen uptake decreased by 13% in the whole body, while it remained unchanged in the liver and kidney. The systemic and pulmonary vascular resistances increased, while the extravascular lung water decreased. Autotransfusion of fluid from tissue to blood was indicated by hemodilution, which was most apparent in subjects showing only a minor change in peripheral resistance. Cardiac output, blood volume, and systemic vascular resistance were significantly more increased by infusion of 900 mL of albumin 5% than by 900 mL of Ringer's solution. However, infusion of 1800 mL of Ringer's solution increased the extravascular lung water and the pulmonary arterial pressures to significantly above baseline, while no significant difference from baseline was found after 900 mL of Ringer's acetate solution. CONCLUSIONS: Withdrawal of 900 mL of blood induces similar reductions in cardiac output as in the splanchnic and renal blood flow rates. A fluid shift from the extravascular to the intravascular fluid compartment might restore up to 50% of the blood loss. Optimal volume substitution with Ringer's solution can be effectuated by infusing between 100% and 200% of the amount of blood lost.

Acute Disease↗
PubMed1997

Haemodynamics during inhalation of a 50% nitrous-oxide-in-oxygen mixture with and without hypovolaemia.

BACKGROUND: Inhalation of a gas mixture containing 50% nitrous oxide in oxygen (N2O/O2) is widely used for pain relief in emergency situations, which may also be associated with blood loss. The aim of this study was to evaluate the haemodynamic effects of this gas mixture in normo- and hypovolaemic subjects. METHODS: Six healthy males were studied during inhalation of N2O/O2 before and after withdrawal of 900 ml of blood. On each occasion, we measured systemic and pulmonary arterial pressures, cardiac output, blood gases, extravascular lung water, and the blood flow and oxygen consumption in the whole body, liver and kidneys. RESULTS: Inhalation of N2O/O2 reduced the stroke volume and increased peripheral resistance. Oxygen uptake decreased in the liver (-30%) and in the whole body (-23%). Blood withdrawal reduced the pulmonary arterial and central venous pressures (-30 to -50%) and further decreased stroke volume and the blood flows to the liver and the kidney (-15%). The extravascular lung water tended to increase both during inhalation of N2O/O2 and during hypovolaemia. CONCLUSION: N2O/O2 aggravated the hypokinetic circulation induced by hypovolaemia. However, the oxygen consumption decreased only during inhalation of N2O/O2. This opens up the possibility that the cardiodepression associated with N2O/O2 is caused by a change in metabolic demands.

Adult↗
PubMed1997

Estimation of fluid absorption by using the area under the curve for ethanol in expired air.

The use of irrigating fluid containing a small amount of ethanol allows fluid absorption to be monitored by means of expired-breath tests during transurethral resection of the prostate (TURP). There is, however, no consensus concerning how the breath ethanol data should be converted into the volume of irrigant absorbed. The present study examines the use of the product of concentration and time (area under the curve) to predict how much fluid is absorbed. Intermittent infusions of ethanol in 5 volunteers showed that the relationship between area under the curve and ethanol load was best described by a polynomial expression. This was also applicable to the uptake of small volumes of irrigating fluid during 16 TURPs. When patients with large-sized absorption (> 1,000 ml) were also considered, however, the precision was better when the absorbed volume was predicted by a multiple linear regression formula where the ethanol level in the exhaled breath at the end of any 10-min period during TURP and the time during which ethanol had been detected served as independent factors.

Absorption↗
PubMed1997

Blood haemoglobin and the long-term incidence of acute myocardial infarction after transurethral resection of the prostate.

OBJECTIVES: To study risk factors for acute myocardial infarction (AMI) in men suffering from benign prostatic hypertrophy. METHODS: We followed 811 patients who underwent transurethral resection of the prostate (TURP) between 1983 and 1992 until the end of 1993 with regard to the incidence of AMI. The association between AMI and various potential risk factors was evaluated by epidemiological methods. RESULTS: Fifty-two patients developed a first-time AMI after TURP. A pre-operative blood haemoglobin concentration in the range of 100-129 g/l (normal range 130-165 g/l) was associated with an increased long-term relative risk of a first-time AMI, which was estimated to be 2.0 (95% confidence interval = 1.0-4.1). This estimate became slightly stronger when we also included the 76 patients with a first AMI before surgery, 10 of whom developed a re-infarction after TURP. Furthermore, it was largely unchanged on adjusting for impaired health status and age > or = 75 years (patient factors) and for fluid absorption > or = 500 ml and a blood loss > or = 275 ml (operative factors), which had been reported to increase the long-term risk of AMI in a previous study. CONCLUSION: A moderately reduced blood haemoglobin level before TURP is associated with a doubled risk of developing AMI in later life.

Aged↗
PubMed1997

Survival after high-dose intraperitoneal infusion of glycine solution in the mouse.

We used an animal model to study whether glycine prompts death after absorption of irrigating fluid by the extravascular route. Mice were divided into groups of 10 and given an intraperitoneal infusion of 200, 225, 250, 275 or 300 ml/kg of glycine 1.1%, 1.5% or 2.2%. With all infused volumes, the chance of survival was better after infusion of glycine 1.1% and glycine 1.5% than after glycine 2.2%. The overall death rates were 10%, 16% and 46%, respectively. Logistic regression analysis showed that the outcome was significantly and independently affected by both the glycine concentration and the infused volume. We conclude that the glycine concentration of an irrigating fluid deposited in the peritoneal cavity is important to the chance of survival. The poorest chance is obtained with glycine 2.2%.

Animals↗
PubMed1997

Trapping of electrolytes during fluid absorption in transurethral resection of the prostate.

Absorption of irrigating fluid into the blood during transurethral resection of the prostate is associated with diffusion of sodium ions from the interstitial fluid space into the plasma. Some of this sodium is "trapped" and removed from the body in connection with bleeding and excretion of urine. The magnitude of this sodium loss was calculated over 10-min periods throughout 20 operations during which absorption of glycine solution occurred. The amount of trapped sodium increased with the amount of blood lost, a 1000-ml bleed correlating with a loss of 10 mmol of sodium. Two thirds was trapped with the plasma loss and one-third with the osmotic diuresis. This mechanism contributes to the absolute loss of sodium from the body. The total sodium loss, however, accounts for one third of the maximum hyponatraemia and is still dominated by the plasma-derived sodium excreted during the glycine-induced osmotic diuresis.

Absorption↗