Dynamic variation of the axillary veins due to intrathoracic pressure changes: A prospective sonographic study.

INTRODUCTION: The ultrasound-guided axillary vein is becoming a compulsory alternative vessel for central venous catheterization and the anatomical position offers several potential advantages over blind, subclavian vein techniques. OBJECTIVE: To determine the degree of dynamic variation of the axillary vein size measured by ultrasound prior to the induction of general anesthesia and after starting controlled mechanical ventilation. DESIGN: Prospective, observational study. METHODS: One hundred ten patients undergoing elective surgery were enrolled and classified according to sex, age, and body mass index. Two-dimensional cross-sectional vein diameter, area, and mean flow velocity were performed using ultrasound on both the left and right axillary veins of each subject before and after induction of anesthesia. RESULTS: There was statistically significant evidence showing that the axillary vein area increases when patients are mechanically ventilated. When considering venous flow velocity as a primary outcome, velocity decreased after patients moved from spontaneous to mechanical ventilation (coefficient = -0.267), but this relationship failed to achieve statistical significance (t = -1.355, p = 0.179). CONCLUSIONS: Anatomical variations in depth and diameter as well as the collapsibility due to intrathoracic pressures changes represent common challenges that face clinicians during central venous catheterization of the axillary vein. A noteworthy increase in vessel size as patients transition from spontaneous to mechanical ventilation may theoretically improve first-pass cannulation success with practitioners skilled in both ultrasound and procedure. As a result, placing a centrally inserted central catheter after the induction of anesthesia may be beneficial.

Variabilidade na determinação do ponto externo de referência para a medida de pressão venosa central em crianças / Variability in the establishment of an external reference point for central venous pressure measurement in children

OBJETIVO: Verificar variabilidade na determinação da linha axilar média como ponto externo de referência (PER), por diferentes profissionais de saú de, para a aferição de pressão venosa central em crianças. MÉTODOS: Estudo descritivo e de correlação realizado em uma unidade de cuidados intensivos pediátricos de um hospital universitário. Durante a determinação da linha axilar média como PER para a aferição da pressão venosa central, cinco avaliações realizadas no mesmo paciente por profissionais de saúde e uma realizada por um avaliador treinado foram comparadas. O resultado foi um total de 120 indicações de 44 profissionais de saúde, 17 (38,6 por cento) auxiliares e técnicos de enfermagem, 16 (36,3 por cento) enfermeiros e 11 (25,1 por cento) médicos, além de 24 identificações realizadas por avaliador treinado. Os dados foram analisados utilizando os testes do qui-quadrado, ANOVA, Kruskall-Wallis e teste t, fixando o nível de significância em 5 por cento. RESULTADOS: Houve diferença significante entre as identificações realizadas pelos profissionais de saúde e pelo avaliador (p < 0,001). Comparando a variabilidade das medidas realizadas pelos profissionais, 56 (46,7 por cento) foram menores do que a identificação do avaliador (variação de -0,5 até -9), 44 (36,7 por cento) foram maiores (variação de 0,5 até 4) e 20 (16,7 por cento) foram coincidentes (variação nula). Não se identificou influência da categoria profissional sobre a concordância entre os PER indicados (p = 0,899), tampouco na variabilidade observada (p = 0,778). Observou-se, contudo, que profissionais com maior tempo de experiência em unidades de cuidados intensivos demonstraram uma tendência a maior variabilidade com as medidas dos avaliadores. CONCLUSÃO: Verificou-se variabilidade nas indicações da linha axilar média como PER entre os profissionais e o avaliador treinado. A variabilidade não foi influenciada pela categoria profissional e quanto maior o tempo de experiência do profissional, maior...

OBJECTIVE: To investigate the variability in the establishment of the midaxillary line as external reference point (ERP), by different healthcare workers, for the measurement of central venous pressure in children. METHODS: Descriptive and correlational study carried out in a pediatric intensive care unit of a teaching hospital. During the establishment of the midaxillary line as ERP for central venous pressure measurement, five assessments of the same patient made by healthcare workers and one assessment made by a trained evaluator were compared. A total of 120 assessments were made by 44 healthcare workers, 17 (38.6 percent) by nursing assistants and nursing technicians, 16 (36.3 percent) by nurses and 11 (25.1 percent) by physicians, in addition to 24 assessments made by the trained evaluator. The data were analyzed using the chi-square test, ANOVA, Kruskal-Wallis test and t test. Significance level was set at 5 percent. RESULTS: There was statistically significant difference between the assessments made by healthcare workers and by the evaluator (p < 0.001). The comparison of the variability in the measurements made by healthcare workers revealed that 56 (46.7 percent) measurements were lower than those obtained by the evaluator (range from -0.5 to -9), 44 (36.7 percent) were higher (range from 0.5 to 4) and 20 (16.7 percent) were concordant (zero variability). Professional category did not influence the concordance between the ERPs (p = 0.899), or the variability observed (p = 0.778). However, the measurements made by professionals with greater experience in intensive care tended to differ more sharply from those made by the evaluators. CONCLUSION: The indications of the midaxillary line as ERP presented variations when measured by the healthcare team and by the trained evaluator. Variability was not influenced by professional category, and the more experienced the healthcare worker, the greater the probability for underestimation of the ERP...

Axillary and tympanic membrane temperature measurements are unreliable early after cardiopulmonary bypass.

BACKGROUND AND OBJECTIVE: Inaccurate measurements of body temperature following cardiopulmonary bypass may be associated with serious complications. The purpose of this study was to determine whether axillary and tympanic temperature measurements correlate with the urinary bladder temperature in the early postcardiac surgery period. METHODS: Forty-nine adult patients who underwent cardiac surgery under cardiopulmonary bypass at our institution were prospectively studied. Urinary bladder, right axillary, right tympanic and left tympanic temperature measurements were simultaneously recorded at 0, 6, 12 and 18 h following cardiopulmonary bypass. Patients had one to four sets of recordings and a total of 629 temperature measurements were recorded. The mean difference (bias) between the bladder and each of the other methods and limits of agreement were calculated using Bland and Altman method. RESULTS: The mean core body temperature recorded from the bladder on admission to the intensive care unit was 36.4 degrees C. After 6, 12 and 18 h the mean core body temperature was 37.4 degrees C (range: 35.2-39.0), 37.5 degrees C and 37.45 degrees C, respectively. The mean differences (bias) between the bladder temperature and the other three methods were: left tympanic, 0.65 degrees C (95% CI: -0.24 to 1.58); right tympanic, 0.57 degrees C (95% CI: -0.48 to 1.63) and right axillary, 0.55 degrees C (95% CI: -0.27 to 1.36). CONCLUSIONS: The axilla and tympanic membrane are unreliable sites for core body temperature measurement early after cardiopulmonary bypass in adult patients and clinical decisions should be based on more reliable methods.

Improvement in the visualization of superficial arm veins being evaluated for access and bypass.

OBJECTIVES: Duplex ultrasound mapping of arm veins is being performed with increasing frequency. Unlike ultrasound testing in other areas, this has never been subjected to a gold standard invasive test to determine accuracy. Duplex mapping appears to have a good predictive value whenever large veins are demonstrated preoperatively, but its ability to accurately measure minimum-sized veins is unproven. In this study, we compared diameter measurements obtained under six different conditions and used the maximum diameter as the comparison gold standard. METHODS: A 12-MHz linear probe was used to measure the cephalic and basilic vein cross-sectional diameters at the wrist level in 24 normal volunteers under the following conditions: (1) resting supine with a room temperature of 23 degrees to 24 degrees C, (2) supine with a tourniquet inflated to 65 mm Hg, (3) sitting with the arm dangling, (4) sitting with a tourniquet, (5) sitting after a 2-minute immersion in warm water (44 degrees C), and (6) same with tourniquet. Half the subjects underwent the protocol in a different order. RESULTS: Vein diameters were significantly larger after submersion in warm water compared with supine (P < .05, pair-wise multiple comparison procedure, Student-Newman-Keuls method). Assuming the sitting position (from supine) resulted in a decreased arm vein diameter 58% of the time. In 25% of the normal subjects, the cephalic vein size was <2 mm, which increased to >2 mm after warming. All subjects had either a cephalic or a basilic vein at the wrist that was >3.1 mm after warming. CONCLUSION: Use of warm water immersion before vein diameter measurement in a sitting position, without a tourniquet, will result in significantly larger diameter findings in normal arm veins. These diameters are likely to more closely resemble the venous diameter after distension with arterial pressure. Further studies are needed to see if warming in patients could result in increased utilization of autogenous arm vein for dialysis access and bypass.

[The efficacy of local T-pa infusion in the treatment of axillary vein thrombosis]. / Aksiller ven trombozunda lokal t-PA infüzyon tedavisinin etkinligi.

BACKGROUND: We evaluated the results of local tissue plasminogen activator (t-PA) infusion in the treatment of axillary vein thrombosis. METHODS: Fourteen male patients (mean age 23+/-2 years) who presented with pain and swelling in the arm were diagnosed as having axillary vein thrombosis. Besides physical examination, diagnoses were made with the use of venous Doppler ultrasound, duplex scanning or venography. Complaints were localized in the right upper arm in 10 patients, and in the left upper arm in four patients. Time to presentation from the onset of complaints ranged 1-3 days, 3-7 days, 7-10 days, and 10-14 days in six, three, two, and three patients, respectively. Infusion of t-PA (0.25 mg/kg) was performed for one hour via a venous catheter inserted to the distal part of the brachial vein. Venous patency was evaluated using Doppler ultrasound and venography. RESULTS: Axillary vein was shown to be patent by venous Doppler ultrasound in eleven patients within a mean of 4.2 hours. Three patients who exhibited no improvement received another t-PA (0.05 mg/kg/h) infusion six hours after the initial treatment. Venous Doppler ultrasound showed almost complete patency of the lumen after six, seven, and 11 hours of the subsequent infusion, respectively. Following therapy, all the patients were administered prophylactic anti-aggregating treatment. On control examinations after three months, venous Doppler ultrasound and venography showed that the lumens were almost completely patent in 12 patients and two patients, respectively. No recurrences were detected. CONCLUSION: Fibrinolytic agents yield high efficacy in the treatment of axillary vein thrombosis.

Superficial venous anastomosis in the human upper extremity--a post-mortem study.

The frequent use of veins in surgery, especially in the replacement of clogged arteries in the lower extremities, persuaded the authors to conduct research concerning the morphology of superficial veins in the human upper extremity. In a post-mortem study a group of 40 male subjects of 22-92 years of age was examined. The preparation of the region of the elbow fossa was performed in order to establish the architecture of superficial veins in the extremity. Many detailed anthropometrical measurements were also carried out, enabling a typological evaluation to be made of the deceased under study. Two characteristic pictures of venous anastomosis were tested, one with symmetrical tributaries to the vena basilica et cephalica and the second characterised by a rich set of tributaries to the vena basilica. The characteristics, calibre and structure of both these suggest a fruitful application of them in vessel surgery. The vena cephalica in particular, taken with efficient valves, may successfully play the role of vessel implant.

Improved patency of prosthetic arteriovenous grafts with an acute anastomotic angle and flow diffuser.

OBJECTIVE: Conventional end-to-side anastomosis to establish venous outflow for prosthetic arteriovenous grafts often requires operative patch angioplasty within 1 year because of venous stenosis. Rather than conventional venous anastomosis, a modified end-to-side anastomosis at a 15-degree angle with a flow diffuser was constructed. Such diffusers allow decreased flow velocity and increased pressure, inhibiting boundary layer separation. METHODS: Ten brachial artery to axillary vein 6 mm straight se-polytetrafluoroethylene prosthetic arteriovenous grafts were created with this technique. Patients included 6 men and 4 women (mean age, 66.4 years; range, 54-80 years), all with renal failure and a history of diabetes. The degree of stenosis at the venous anastomosis was determined with duplex scanning at intervals of 6 months. Analysis of survival and cumulative primary patency estimates were determined with the Kaplan-Meier method. RESULTS: Primary cumulative patency estimate of 100% for the modified group at 18 and 24 months was significantly greater than that for age-matched historic control fistulas with the conventional end-to-side anastomosis (n = 20): 18 months, 32%; 24 months, 32% (P <.05). Although venous stenosis could not be quantitated for thrombosed conventional fistulas, modified anastomoses had minimal stenosis at 24 months: mean area reduction, 30% (range, 20%-45%). CONCLUSION: Incorporation of a flow diffuser and a 15-degree anastomotic angle significantly increases patency of prosthetic brachial artery to axillary vein grafts.

Importance of Doppler analysis of transmitted atrial waveforms prior to placement of central venous access catheters.

PURPOSE: To assess the sensitivity of Doppler flow analysis of the axillary and internal jugular veins to screen for clinically occult thoracic central veno-occlusive disease and predict successful placement of central access catheters. MATERIALS AND METHODS: Sixty-seven patients underwent both duplex sonographic evaluation of the axillary and internal jugular veins and contrast venography prior to placement of a central venous catheter. Duplex evaluation included visual evidence of veno-occlusive disease as well as the presence or absence of normal transmitted polyphasic atrial waves and respiratory variation of flow. Diagnostically adequate venograms were available for comparison with the duplex sonograms in 168 access routes (access site plus downstream conduit veins). The contrast venograms and sonograms were compared by using retrospective blinded interpretation. Outcome of attempted catheter placement was tabulated. RESULTS: Directed sonographic imaging of the axillary and internal jugular vein allowed detection of access route veno-occlusive disease with a sensitivity of only 33.3%. Alternatively, when Doppler flow analysis found atrial waveforms that were not polyphasic, central conduit occlusive disease was detected with a sensitivity of 79.6%. Monophasic atrial waveforms were associated with a 25% failure rate of catheterization due to central vein occlusive disease, whereas polyphasic atrial waveforms were correlated with a 100% success rate for catheter placement. CONCLUSION: In asymptomatic patients, sonographic imaging alone misses most instances of central veno-occlusive disease. However, Doppler flow analysis of transmitted atrial waveforms substantially improved the sensitivity. A normal polyphasic atrial waveform virtually excludes the possibility of a more central venous occlusion or stenosis greater than 80% and ensures an adequate route for central venous catheterization.