Use of Bony Landmarks during Adrenal Venous Sampling to Guide Catheterization of the Left Adrenal Vein

Purpose The aim of this study was to examine the utility of fluoroscopic bony landmarks in predicting the location of the left adrenal vein during adrenal vein sampling (AVS). Methods Eighty-six AVS procedures were performed in 81 patients between August 2013 and March 2020. A selectivity index was calculated for each case by dividing the measured left adrenal vein cortisol level by the peripheral vein cortisol level. Successful “target” left adrenal vein catheterization was confirmed in cases with a selectivity index of three or greater. Intraprocedural AVS fluoroscopic images were selected that demonstrated catheter position in the left adrenal vein. Lateral distance from the catheter tip in the left adrenal vein to the lateral margin of the left pedicle at the associated vertebral body level was measured. Results Mean patient age was 56.4 years (range: 19–80 years) and 48 (59.3%) patients were male. Target sampling in the left adrenal vein was confirmed in 82 (95.3%) cases. In 78 (95.1%) targeted cases, the catheter terminated less than 25 mm from the left lateral pedicle at a mean distance of 11.2 mm. The catheter was most frequently placed at the T12 and L1 vertebral body levels. Four (4.7%) cases demonstrated nontarget catheter positioning, two (50.0%) of these cases were within 25 mm. Conclusion The position of the left adrenal vein is generally located in a predictable position relative to bony landmarks. By utilizing these landmarks, positioning of the sampling catheter during AVS can be more reliable with the potential to avoid repeat procedures and delays in patient care.

Chronic catheterization of external iliac vessels in growing cattle

Bovine preparations that allow for in vivo measurement of metabolic fluxes across the hindlimb often suffer from limited durability, usually because of failure of the venous catheter. A catheterization procedure that virtually eliminates this occurrence is presented. A silicone rubber catheter is implanted permanently in the femoral vein. It accommodates the repeated insertion and removal at each sampling session of a temporary sampling catheter. A simple and reliable method ensures the positioning of this catheter in the external iliac vein of a conscious, normally standing animal. The application of this approach allowed the study of hindlimb metabolism of cattle for up to 4 mo without a single planned sampling session postponed or missed. This preparation is particularly well suited for studies that require repeated measurements of hindlimb metabolism on the same animals over a period of many months.

A new method of sampling blood for measurement of plasma adenosine

The half-life of adenosine in human blood is 1-2 s at 37 degrees C. To measure plasma adenosine concentration accurately, it is necessary to inhibit adenosine metabolism during transit of blood through the sampling catheter. We have tested a double-lumen catheter and a solution of compounds that inhibit adenosine metabolism (stop solution) for this purpose. Stop solution and radiolabeled adenosine were delivered via an inner lumen, mixed with blood at the catheter tip, and withdrawn to a collection syringe in an outer lumen. Extracellular recovery of label was 89 +/- 5% and proportional to the quantity of label added to blood. In contrast, when blood and radiolabel were mixed with stop solution in the collecting syringe only after passage through the catheter, recovery of radiolabel was 7 +/- 3%. The importance of inhibiting pathways of adenosine formation and degradation or uptake during transit of blood through the catheter was demonstrated. The results suggest that a double-lumen catheter and stop solution are both necessary and suitable for collection of human blood to determine the concentration of plasma adenosine.

Measurement system for respiratory water vapor and temperature dynamics

An instrumentation system has been developed to simultaneously measure water vapor and temperature at the same point within respiratory airways during breathing. A mass spectrometer was used to analyze gas continuously sampled through a modified inlet catheter. At the tip of the catheter, gas temperature is sensed by a microbead thermistor. Adequate water vapor dynamics is achieved by a two-step procedure. First, the tip of the sampling catheter is constricted to reduce the catheter's internal pressure and thereby prevent condensation and evaporation. Second, the water vapor signal from the mass spectrometer is compensated electronically to improve its transient response. As part of the evaluation of the system, water vapor and gas temperature were measured in the oropharynx of human subjects.

Nasal CPAP and Work of Breathing Study Questioned

The paper by Goldman et al (Pediatrics 64:160, 1979) comparing the mechanics of breathing in neonates treated with nasal vs mask continuous positive airway pressure (CPAP) recommends that, since nasal CPAP appeared to increase the work of breathing, "other methods be considered for the delivery of CDP (continuous distending pressure)." As a strong proponent of nasal CPAP, I would like to express several concerns with the study and its interpretation. First, according to the authors' drawing, the nasal device used for the study had been modified with a PE 20 sampling catheter inserted through one of the prongs.

Letters to the Editor

We appreciate Dr Kattwinkel's concerns and we would like to clarify several of his comments: 1. Comparison of work of breathing—Dr Kattwinkel correctly points out that, by adding the PE 20 sampling catheter, we have increased the resistance of the nasal prongs over their resistance when used clinically. In fact, the catheter does increase the measured resistance of the nasal prongs by about 36%. We must concur that work of breathing measured with the nasal prongs would have been less if the sampling catheter was not present.

Glucose Oxidase Method for Continuous Automated Blood Glucose Determination

A glucose oxidase-peroxidase method for continuous automated monitoring of blood glucose has been developed. The response is linear over the range 0-800 mg/100 ml. Sensitivity can be maintained for 24 hr or longer and can be restored by rinsing the analytic system with sulfuric acid to permit studies of longer than 48 hr in duration. A precision of ± 1% can be maintained between rinses for samples containing 100-600 mg of glucose per 100 ml. This method is satisfactorily specific for glucose: The response with other sugars is less than 1% of the response obtained with the same concentration of glucose. Ascorbic acid causes no significant inhibition of the response to glucose. The inhibition by uric acid has been reduced fifty-fold compared to that in other methods. Transit through the sampling catheter and analytic system requires 15 min. Timed from the first detectable response to a change in concentration, 25% of total response is achieved in 30 sec and 90% in 80 sec. Fifty percent of an oscillation with a half-period of 45 sec can be detected; no oscillations this short were observed in records of human blood glucose. Applicability and feasibility of this method have been demonstrated in over 2000 hr of repeated blood glucose recordings in 12 diabetic and 6 normal subjects.