Defining a safe corridor for trans-iliac pin placement in cats.

OBJECTIVE: To identify whether a theoretical predictable safe corridor is available in cats for placement of trans-iliac pins without the use of fluoroscopy. METHODS: Twenty-one cats with straight orthogonal normal pelvic radiographs were included. Two start points were evaluated: a midpoint and a dorsal point. The midpoint was defined as midway between the dorsal lamina of the sacral vertebral canal and the cranial dorsal iliac spine. The dorsal start point was 2 mm ventral to the cranial dorsal iliac spine. The pin was assumed to be driven at 90 degrees to the lateral face of the ilium, and considered surgeon accuracy was ±4 degrees from the perpendicular. The angular range and the distance between the iliac wings from the ventrodorsal radiograph were used to calculate the possible cross-sectional area and pin exit location if driven from one iliac wing to the other. The corridor was then evaluated for repeatability in six randomly selected cats. RESULTS: Vertebral foramina penetration risk was identified in some cats when using a 1.6 and 2 mm-diameter pin using the mid-iliac wing start point. The dorsal start point decreased the available pin placement area but reduced the risk of entering the hazardous zone for all pin sizes up to 2 mm. CONCLUSION AND RELEVANCE: A theoretical defined safe corridor is available for trans-iliac pin placement in cats between 2.0 and 5.5 kg. A 1.2-mm pin is the safest if using the mid-iliac wing start point. A more dorsal start point can accommodate up to a 2.0-mm pin if correctly aligned to the sacrum.

Progression of lower-extremity arterial occlusive disease in type II diabetes mellitus.

The prevalence of lower-extremity arterial occlusive disease (LEAOD), the progression of LEAOD, and the incidence of new LEAOD were determined by noninvasive method in 410 volunteers between the ages of 50 and 70 yr; 252 individuals had type II (non-insulin-dependent) diabetes, 158 were control subjects. LEAOD was monitored with the ankle/arm systolic blood pressure index in combination with Doppler arterial velocity waveform analysis. LEAOD was much more prevalent in the type II patients (22%, 55 of 252) than in the control subjects (3%, 4 of 158) (P less than .00001). The prevalence of risk factors for LEAOD was much higher in the type II patients, including elevated triglyceride, depressed high-density lipoprotein (HDL) cholesterol, hypertension, smoking, and elevated systolic blood pressure. In type II diabetic patients the incidence of new LEAOD over a 2-yr period (14%, 28 of 197) was lower than the incidence of LEAOD progression (87%, 45 of 52). Type II patients with LEAOD also had a high incidence of mortality (22%, 12 of 55) compared with those without LEAOD (4%, 8 of 197) (P less than .0005). A risk score including smoking history, duration of diabetes, depressed HDL cholesterol, total cholesterol, elevated systolic blood pressure, and low obesity index is related to LEAOD. After accounting for the effect of all of the risk factors, we suggest that type II diabetes contributes additional risk for LEAOD.

Status of the valves in the superficial and deep venous system in chronic venous disease.

The relationship between the functional status of the venous valves in the superficial and deep veins and ulceration was evaluated in 42 patients. Twenty-five patients had ulcers, 12 of these patients had a history of previous deep venous thrombosis and 13 of these patients denied such an event. Seventeen patients had normal ankle skin, 10 of these patients had a documented history of deep vein thrombosis and seven of these patients had varicose veins only. An ultrasonic duplex scanner was used to document the presence of reflux in all segments of the superficial and deep system. In the entire group of 25 limbs with ulceration, valvular incompetence was noted in 22 limbs at levels involving segments that communicated with the ulcer-bearing area. Of the 17 limbs with normal ankle skin, in only two instances was a single segment of posterior tibial vein in midcalf found to be incompetent. For those patients with normal ankle skin and a history of varicose veins, the deep veins below the common femoral vein level were always competent.

The mechanism of venous valve closure. Its relationship to the velocity of reverse flow.

Venous valves will close when the reversal of the normal pressure gradient generates a sufficient reverse flow velocity. By testing 20 healthy subjects with ultrasonic duplex scanning and controlled limb compression. It was found that the velocity of reflux is related to the external compression pressure. Valve closure is an abrupt cessation of reverse flow. In this study, with subjects in a supine position, valve closure was achieved only after reverse velocities exceeded 30 cm/s. This velocity was not generated by manual compression of the limb. With a Valsalva maneuver, this velocity is achieved only in the common femoral vein in 90% of the tested individuals. The reflux velocities in response to a Valsalva maneuver are progressively lower in more distal veins--the profunda femoris, the superficial femoral vein, and the popliteal vein. With reverse velocities lower than 30 cm/s, the valves will not close and reflux can persist. Valsalva's maneuver only allows a diagnosis of valvular competence at the most proximal level in the venous tree.

The use of natural-abundance high-resolution carbon-13 NMR in the study of mucus glycoproteins.

Natural-abundance 13C NMR was used to study samples of native mucus from dog trachea and purified mucus glycoprotein from hog stomach. Despite the large molecular weight of the molecules (several million) and visco-elastic nature of the gel, spectra were produced which could be resolved into individual sharp resonances which gave significant structural detail. These results indicate the potential use of this powerful technique in the study of mucus glycoprotein structure in the undegraded molecule.

Visualization of calf veins by color flow imaging.

Both indirect and direct noninvasive tests have been shown to be useful for the detection of deep venous thrombi involving the proximal veins (popliteal to inferior vena cava). However, thrombi that are confined to the calf veins will not affect venous outflow and cannot be detected by the plethysmographic methods. B-mode imaging, while excellent for the major deep veins, is also limited in the calf region because the veins are small, and imaging resolution is not always adequate to permit visualization of these smaller veins. With the availability of duplex scanning with "slow flow" color capability, these veins lend themselves to study. In 30 normal subjects, we were able to visualize all paired veins from the level of the ankle to the popliteal fossa. The clinical implications of this approach are discussed.

Review of the use of throat packs in nasal surgery.

BACKGROUND: Throat packs are employed in nasal surgery to prevent contamination of the upper aerodigestive tract. Their use is thought to reduce the risk of aspiration and post-operative nausea and vomiting. However, use of throat packs may also be accompanied by increased throat pain. In order to inform our clinical practice, the evidence base for throat pack insertion was reviewed. METHOD: A search was made of the Pubmed database from the 1950s to March 2008. Four randomised, controlled, clinical trials were reviewed. RESULTS: All the trials had significant methodological weakness. In all but one, no power calculations were done. There were inconsistencies in the measurement of pain and heterogeneity of rhinological procedures. The one adequately powered trial could not demonstrate a difference in post-operative nausea and vomiting with the use of throat packs (beta error = 20 per cent). CONCLUSION: Further, adequately powered trials are required involving patients undergoing rhinological procedures with a higher risk of blood contamination (e.g. functional endoscopic sinus surgery), in order to provide definitive evidence on the morbidity of throat packs in rhinological procedures.

Identification of mycobactins by nuclear-magnetic-resonance spectroscopy.

Details are given of the n.m.r. spectra of mycobactins F, H, M, N, P, S and T, and resonances are ascribed to all the protons in these molecules. A simplified system is described for identifying known mycobactins by the n.m.r. spectrum alone. This method will not distinguish mycobactins S and T, whose nuclei differ only in the configuration at an asymmetric centre.

Low extracellular Ca2+ and enzyme release in the perfused rabbit heart.

Previous studies have shown that the well-oxygenated perfused rabbit heart releases creatine kinase when treated with the calcium antagonist drug verapamil (VER) in a dose-related manner. It is possible that this effect is related to Ca2+ ion deprivation of the sarcolemma. This possibility was explored by perfusing hearts with low Ca2+ (0.5, 0.23, 0.15, and 0 mM) versus a control group (1.27 mM Ca2+) for 60 min. Low Ca2+ perfusion was associated with reduction in the heart rate--left ventricular systolic pressure product and O2 consumption, tendency for the coronary sinus flow to increase, electromechanical dissociation, prolongation of atrioventricular conduction and QT interval, and decrease in myocardial glycogen. Lower total adenosine nucleotides were found only in the 0 mM Ca2+ group. As the Ca2+ concentration was reduced, the hearts lost increasing amounts of creatine kinase, aspartate aminotransferase, and lactate dehydrogenase. These results confirm the importance of Ca2+ ions in contractile and electrical cardiac functions and show that decreased availability of this cation leads to increasing enzyme leakage resembling that seen in VER-treated hearts.

Influence of low extracellular Ca2+ ions on the cardiac function changes induced by verapamil in the perfused rabbit heart.

We tested the hypothesis that the myocardial effects of verapamil (VER) could be enhanced by decreasing the extracellular Ca2+ concentration ([Ca2+]o) in the isolated rabbit heart at 37 degrees C. After perfusion with standard Krebs - bicarbonate solution containing 1.27 mM Ca2+, for a 30-min period of stabilization and 15 min of control, groups of hearts were perfused for an additional 60 min with solutions containing one of the following: 1.27 mM Ca2+ (control group), 0.23 mM Ca2+ (low [Ca2+]o group), 1.27 mM Ca2+ plus 10(-7) M VER (VER group), or 0.23 mM Ca2+ plus 10(-7) M VER (combination, CBN group). These concentrations of [Ca2+]o and VER produce submaximal responses in our preparation. We found that the heart rate - LV pressure product (RPP) in the CBN group fell rapidly to 0 in the first 2-3 min of perfusion, this response being significantly lower than in the other two groups for the first 15 min. Electromechanical dissociation (EMD) appeared in one of six hearts at 60 min and in four of six hearts at 30 min in the low [Ca2+]o and VER groups, respectively, whereas it occurred in the CBN group in all hearts at 3 min. Depolarization rate (DR) fell by 10% in the low [Ca2+]o and VER groups versus a reduction of 45% in the CBN group (P less than 0.05) during the last 45 min of perfusion. The PR interval increased by 300% in the CBN group, a much greater and significant change (P less than 0.05) than in the hearts exposed to VER or low [Ca2+]o.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous infusion of the conjunctival sac with chloramphenicol in preoperative cataract patients.

(1) Administration of a drug solution to the conjunctival sac by means of continuous infusion through a fine-bore silicone elastomer tube has been shown to be a simple and practical method in hospital inpatients. The use of a body-borne clockwork-driven syringe ram allows the patient to be ambulant. (2) The use of continuous infusion reduces the nursing supervision required compared with repeated administration of drops. (3) Further work will be needed to established the optimum concentration of chloramphenicol needed to equal that achieved by repeated instillations. (4) The flow rate of the infusion producing no overflow, particularly in elderly patients, is likely to be less than 0-01 ml/min.

Duplex ultrasound assessment of venous diameters, peak velocities, and flow patterns.

Duplex ultrasound was used to study the diameters, flow patterns, and peak blood flow velocities of the common femoral vein (CFV) in 12 normal subjects (mean age 35 years). Each subject was supine and non-weight-bearing on a tilt table and rotated in 10-degree increments from -10 degrees (head down) to +30 degrees (head up). Cross-sectional B-mode image was used to monitor continuously CFV diameter for 5 minutes in each position. Doppler flow patterns were recorded in longitudinal axis; heart rate and respiratory movements were also noted. CFV flow was affected by respiratory and cardiac events. At -10 degrees flow was primarily related to cardiac events, with flow increasing during diastole. At +30 degrees flow varied minimally with the cardiac cycle and was primarily respiration dependent, stopping at peak inspiration. Proceeding from -10 to +30 degrees the mean maximal CFV diameter corrected for body surface area increased 92% (0.47 +/- 0.11 cm/m2 to 0.90 +/- 0.16 cm/m2, p less than 0.001), whereas peak flow velocity decreased from 41 +/- 10 cm/sec to 13 +/- 5 cm/sec, p less than 0.001. There was a linear, inverse relationship between mean peak velocity and mean corrected diameter, r = -0.99. The study confirms the multiple influences on venous flow patterns and establishes a quantitative relationship between venous diameters and flow velocities.

Quantitative segmental evaluation of venous valvular reflux with duplex ultrasound scanning.

The duration of deep venous valvular reflux was studied in 192 venous segments of the legs of 32 patients in good health. Three methods were used to elicit reflux in the supine and upright positions--Valsalva's maneuver, proximal limb compression, and release of distal limb compression. Standardized compressions were achieved with pneumatic cuffs. When this approach was used to study valve function, the time to complete closure of the valve and cessation of retrograde flow was found to be shorter than that for conventional methods of closure. The distal cuff deflation method is the only one that permits a quantitative and reproducible method to measure duration of venous reflux at all levels of the lower limb. Normal values obtained with this test are presented for the common femoral, deep femoral, and superficial femoral veins and for the popliteal and posterior tibial veins midway between knee and ankle level and the posterior tibial vein at the ankle. In the popliteal vein, median duration of reflux is 0.19 second; 95% of the values in the popliteal vein are less than 0.66 second. In distal areas, duration of reflux is short and uniform. The advantage of the cuff deflation test over the Valsalva method is that the cuff method is not hindered by the presence of ileofemoral valves. A better understanding of the relative importance of deep valve dysfunction at different levels and the expected benefit of valve repair may be obtained with this test.

Primary biliary cirrhosis, dark adaptometry, electro-oculography, and vitamin A state.

Twenty five patients with primary biliary cirrhosis were studied for vitamin A state. In nine patients found to have low circulating vitamin A concentrations no abnormality was found on electro-oculography or in dark adaptation. A positive correlation was found between retinol binding protein and vitamin A values (r = +0.88; p less than 0.001) and between serum albumin and vitamin A values (r = +0.75; p less than 0.001). A weaker and negative correlation was found between serum bilirubin (r = -0.47; p less than 0.05) and vitamin A values. Patients with primary biliary cirrhosis should not receive regular parenteral or even oral vitamin A supplementation unless dark adaptometry or electrooculography yields an abnormal result.

Functional status of the deep venous system after an episode of deep venous thrombosis.

An episode of deep venous thrombosis is often followed by the opening of collaterals, fibrinolysis, recanalization and valvular dysfunction. The effect of these processes on the peak flow velocity in the superficial femoral and popliteal veins after simulated contraction of the calf muscles was tested in a group of normal subjects and three groups of patients who had deep venous thrombosis. There were 12 patients followed less than two years with no skin changes. The second group consisted of 12 patients followed for 8-15 years without ulceration. The third group of 12 patients had active or healed ulcers. The peak flow velocity in the superficial femoral and popliteal veins was assessed by rapidly inflating cuffs about the calf and ankle to 100 mmHg. The velocities generated by cuff compression were lower in patients than in normal subjects. This was particularly true in the superficial femoral vein. This change in velocity may be secondary to incomplete recanalization with resulting stenosis or valvular incompetence in the calf.

Distribution of lipids from the yolk to the tissues during development of the water python (Liasis fuscus).

Energy metabolism during embryonic development of snakes differs in several respects from the patterns displayed by other reptiles. There are, however, no previous reports describing the main energy source for development, the yolk lipids, in snake eggs. There is also no information on the distribution of yolk fatty acids to the tissues during snake development. In eggs of the water python ( Liasis fuscus), we report that triacylglycerol, phospholipid, cholesteryl ester and free cholesterol, respectively, form 70.3%, 14.1%, 5.7% and 2.1% of the total lipid. The main polyunsaturate of the yolk lipid classes is 18:2n-6. The yolk phospholipid contains 20:4n-6 and 22:6n-3 at 13.0% and 3.6% (w/w), respectively. Approximately 10% and 30% of the initial egg lipids are respectively recovered in the residual yolk and the fat body of the hatchling. A major function of yolk lipid is, therefore, to provision the neonate with large energy reserves. The proportion of 22:6n-3 in brain phospholipid of the hatchling is 11.1% (w/w): this represents only 0.24% of the amount of 22:6n-3 originally present in the egg. This also contrasts with values for free-living avian species where the proportion of DHA in neonatal brain phospholipid is 16-19%. In the liver of the newly hatched python, triacylglycerol, phospholipid and cholesteryl ester, respectively, form 68.2%, 7.7% and 14.3% of total lipid. This contrasts with embryos of birds where cholesteryl ester forms up to 80% of total liver lipid and suggests that the mechanism of lipid transfer in the water python embryo differs in some respects from the avian situation.