Kidney Function and Intrarenal Blood Flow Distribution After Bleeding and Infusions of Mannitol and Dextran

Es wurde die Wirkung blutungsbedingter Hypotension auf die intrarenale Durchblutungsverteilung, vermittels interner Bestimmung von markierten roten Zellen mit Betadetektor und der Nierenfunktion bezüglich Clearance und Konzentrationsfähig-keit, des Säure-Basen-Verhältnisses, der renalen Haemodynamik und Nierenfunktion während der Verabreichung von Mannitol und Dextran geprüft. Mäßige Entblutung von 20 ml/kg bewirkte nur leichte änderung der untersuchten Parameter; zusätzliche Blutung von 5-10 ml/kg, welche eine Anurie bewirkte, hatte eine vermehrte Resistance der Rindengefäße zur Folge, während diese im Zirkulationsgebiet des Markraumes im wesentlichen unverändert blieb. Dies spricht für eine verschiedene Wirkung auf die vasokonstriktorischen Mechanismen dieser beiden renalen Gefäßbette. Das Ausmaß des Schockes dokumentierte sich im Säure-Basen-Verhältnis, besonders im Base-Exzess. Mannitol-Verabreichung hatte auf die untersuchten Parameter fast keine Wirkung, ausgenommen ein Anstieg der Harnproduktion und ein Abfall der Harnosmolalität. Plasmaexpansion mit Dextran ließ aile Werte auf das Kontrollniveau zurückkeh-ren und das Säure-Basen-Verhältnis normalisierte sich, was für eine Wiederherstellung der Sauerstoffversorgung der Gewebe spricht.     

Trimming a Tether: A Simple Way to Prevent Complications Related to Tethered Ureteral Stents

Purpose

A method to prevent complications related to a tethered ureteral stent was assessed.

Materials and Methods

In 17 male patients tethers were trimmed just short of the meatus after insertion of a ureteral stent. At stent removal a rigid cystoscope was inserted into the anterior urethra, and the edge of the tether was grasped with foreign body forceps.

Results

Only 1 patient required removal of the tether due to severe urethral discomfort. Pain at cystoscopy for removal of the ureteral stent was minimal.

Conclusions

This method is useful for improving the quality of life during the catheterization period without decreasing effectiveness of a conventional ureteral stent with a tether.     

Human Hepatic Blood Flow and its Relation to Systemic Circulation during Intravenous Infusion of Lidocaine

Twelve healthy young volunteers were studied before and during intravenous administration of lidocaine at a dose rate of 2 or 4 mg/min. Five additional volunteers, who did not receive lidocaine solution but were given the same amount of physiological saline, were studied in the same manner. Heart rate, cardiac output, mean arterial blood pressure, mean right atrial blood pressure, estimated hepatic blood flow and plasma concentration of lidocaine were measured repeatedly. The results showed an increase in heart rate, cardiac output and mean arterial blood pressure, the latter two variables in relation to the plasma concentration of lidocaine. The estimated hepatic blood flow increased, partly as a result of the reduction of splanchnic vascular resistance and partly due to the stimulation of cardiac output. The decrease in splanchnic vascular resistance was proportional to the plasma concentration of lidocaine.     

An Interesting Case: Retrograde Blood Flow from a LIMA Sustaining Hemodialysis via an AVF

A case is described in which the inflow of a left radiocephalic arteriovenous fistula was being maintained by retrograde flow from a patent left internal mammary artery bypass graft, distal to a severe left subclavian artery stenosis. The clinical manifestations of this phenomenon were angina, lateral chest wall pain during dialysis, and distal hypoperfusion of the left hand. After stenting of the subclavian lesion, all symptoms resolved.     

Sources of Error in Noninvasive Pulmonary Blood Flow Measurements by Partial Rebreathing: A Computer Model Study

Background: Partial rebreathing is a noninvasive method for measuring pulmonary blood flow (PBF). This study examines the systematic errors produced by the partial rebreathing technique utilizing a comprehensive mathematical model of the cardiorespiratory system of a healthy, 70-kg adult male.

Methods: The model simulates tidal breathing through a branched respiratory tree and incorporates the effects on carbon dioxide dynamics of lung tissue mass, vascular transport delays, multiple body compartments, and realistic blood-gas dissociation curves. Four studies were performed: (1) errors produced under standard conditions, (2) effects of recirculation, (3) effects of alveolar-proximal airway partial pressure of carbon dioxide (Pco2) differences, and (4) effects of rebreathing time.

Results: Systematic errors are less than 10% when the simulated PBF is between 3 and 6 l/min. At 2 l/min, PBF is overestimated by approximately 35%. At 14 l/min, PBF is underestimated by approximately 40%. At PBF of greater than 6 l/min, recirculation causes approximately 60% of the systematic error, alveolar-proximal airway differences cause approximately 20%, and alveolar-arterial differences cause approximately 20%. The standard rebreathing time of 50 s is shown to be excessive for PBF of greater than 6 l/min. At PBF of less than 3 l/min, errors are caused by inadequate rebreathing time and alveolar-arterial gradients.     

Editorial Commentary: Blood Flow Restriction Therapy Prior to Anterior Cruciate Ligament Reconstruction: Small Effects Require Accurate Measurements

A recent research study showed that blood flow restriction (BFR) therapy was safe and well tolerated but failed to demonstrate efficacy as a modality that provides greater gains in quadriceps strength when added to a standard home program in patients awaiting anterior cruciate ligament (ACL) reconstruction. Despite employing a validated method of measurement, the results were highly variable, indicating the need for measurements with sufficient accuracy to detect the small, but potentially meaningful, gains in quadriceps strength that’s been attributed to BFR. The results inform future investigations of BFR prior to ACL surgery by demonstrating the need for accurate methods of measurements when the anticipated effects are small.     

Retrograde Blood Flow in the Brachial and Axillary Arteries during Routine Radial Arterial Catheter Flushing

Background: Flushing of radial arterial catheters may be associated with retrograde embolization of air or thrombus into the cerebral circulation. For embolization into the central circulation to occur, sufficient pressure must be generated during the flushing process to reverse antegrade blood flow in the arterial blood vessels of the upper extremity. This ultrasound study was designed to examine whether routine radial catheter flushing practices produce retrograde blood flow patterns in the brachial and proximal axillary arteries.

Methods: Duplex ultrasound examinations of the brachial and axillary arteries were conducted in 100 surgical patients to quantify direction and velocity of blood flow during catheter flushing. After obtaining Doppler spectral images of brachial and axillary arterial flow patterns, manual flushing was performed by injecting 10 ml flush solution using a syringe at a rate reflecting standard clinical practices. The flow-regulating device on the pressurized (300 mmHg) arterial flushing-sampling system was then opened for 10 s to deliver a rapid bolus of fluid (flush valve opening).

Results: The rate of manual flush solution injection through the radial arterial catheter was related to the probability of retrograde flow in the axillary artery (P < 0.001). Reversed arterial flow was noted in the majority of subjects (33 of 51) at a manual flush rate of less than 9 s and in no subjects (0 of 48) at a rate 9 s or greater. Retrograde flow was observed less frequently during flush valve opening (2 of 99 patients; P < 0.001 vs. manual flushing).     

Human Hepatic Blood Flow and its Relation to Systemic Circulation during Intravenous Infusion of Bupivacaine or Etidocaine

Fifteen healthy young volunteers were studied before and during an intravenous infusion of a local anaesthetic agent. Seven received bupivacaine and eight etidocaine in a dose rate of 2 mg/min over a period of 150 min. Variables of the central systemic circulation and also the hepatic blood flow were measured repeatedly. The circulatory alterations during administration of the two drug s were compared. Comparisons with previous results concerning lidocaine and a placebo were also made. It was found that bupivacaine increased the heart rate, mean arterial blood pressure and cardiac output significantly more than did etidocaine in an equal plasma concentration. Lidocaine was intermediate between bupivacaine and etidocaine. In contrast, these three drugs had the same decreasing effect upon the splanchnic vascular resistance, which caused an almost identical increase in the estimated hepatic blood flow. The calculated vascular resistance in the systemic circulation, excluding the splanchnic, was unchanged during the infusion of etidocaine, while it decreased during the infusion of bupivacaine. Most of this discrepancy was due to the different plasma concentrations of the drugs.