Avaliação da veia cava inferior na decisão de fluidoterapia em cuidados intensivos: implicações práticas / Inferior vena cava evaluation in fluid therapy decision making in intensive care: practical implications

RESUMO A ressuscitação hídrica do paciente em falência circulatória aguda tem como um de seus objetivos aumentar o volume sistólico e, consequentemente, o débito cardíaco, para melhor oxigenação dos tecidos. Contudo, isso não se verifica em cerca de metade dos pacientes, que são considerados não respondedores a fluidos. A avaliação da resposta a fluidos antes de sua administração pode selecionar os pacientes que devem ter benefício e evitar o risco de sobrecarga nos restantes. Os parâmetros dinâmicos de avaliação da resposta a fluidos têm se revelado promissores enquanto fatores preditores. Entre estes, a medição ecocardiográfica da variação respiratória do diâmetro da veia cava inferior é um método de fácil aplicação, que tem sido difundido na avaliação hemodinâmica em unidades de cuidados intensivos. No entanto, a aplicabilidade desta técnica tem muitas limitações, e os estudos, até à presente data, são heterogêneos e pouco consistentes em alguns grupos de pacientes. Realizamos uma revisão sobre a utilização da variação respiratória do diâmetro da veia cava inferior, medida por ecocardiografia transtorácica, na decisão de administrar fluidos ao paciente em falência circulatória aguda, em cuidados intensivos, incluindo potencialidades e limitações da técnica, de sua interpretação e a evidência existente.

ABSTRACT The fluid resuscitation of patients with acute circulatory failure aims to increase systolic volume and consequently improve cardiac output for better tissue oxygenation. However, this effect does not always occur because approximately half of patients do not respond to fluids. The evaluation of fluid responsiveness before their administration may help to identify patients who would benefit from fluid resuscitation and avoid the risk of fluid overload in the others. The dynamic parameters of fluid responsiveness evaluation are promising predictive factors. Of these, the echocardiographic measurement of the respiratory variation in the inferior vena cava diameter is easy to apply and has been used in the hemodynamic evaluation of intensive care unit patients. However, the applicability of this technique has many limitations, and the present studies are heterogeneous and inconsistent across specific groups of patients. We review the use of the inferior vena cava diameter respiratory variation, measured via transthoracic echocardiography, to decide whether to administer fluids to patients with acute circulatory failure in the intensive care unit. We explore the benefits and limitations of this technique, its current use, and the existing evidence.

Evaluation of volume responsiveness by pulse pressure variability and inferior vena cava dispensability index at different tidal volumes by mechanical ventilation

This study investigated the effects of tidal volume (TV) on the diagnostic value of pulse pressure variation (PPV) and the inferior vena cava dispensability index (IVC-DI) for volume responsiveness during mechanical ventilation. In patients undergoing elective surgery with mechanical ventilation, different TVs of 6, 9, and 12 mL/kg were given for two min. The left ventricular outflow tract velocity-time integral (VTI) was measured by transthoracic echocardiography. The IVC-DI was measured at sub-xyphoid transabdominal long axis. The PPV was measured via the radial artery and served as baseline. Index measurements were repeated after fluid challenge. VTI increased by more than 15% after fluid challenge, which was considered as volume responsive. Seventy-nine patients were enrolled, 38 of whom were considered positive volume responsive. Baseline data between the response group and the non-response group were similar. Receiver operating characteristic curve confirmed PPV accuracy in diagnosing an increase in volume responsiveness with increased TV. When TV was 12 mL/kg, the PPV area under the curve (AUC) was 0.93 and the threshold value was 15.5%. IVC-DI had the highest diagnostic accuracy at a TV of 9 mL/kg and an AUC of 0.79, with a threshold value of 15.3%. When TV increased to 12 mL/kg, the IVC-DI value decreased. When the TV was 9 and 12 mL/kg, PPV showed improved performance in diagnosing volume responsiveness than did IVC-DI. PPV diagnostic accuracy in mechanically ventilated patients was higher than IVC-DI. PPV accuracy in predicting volume responsiveness was increased by increasing TV.

Impact of body characteristics on ultrasound-measured inferior vena cava parameters in Chinese children

Ultrasound-measured inferior vena cava (IVC) and abdominal aorta (Ao)-associated parameters have been used to predict volume status for decades, yet research focusing on the impact of individual physical characteristics, including gender, height/weight, body surface area (BSA), and age, assessed simultaneously on those parameters in Chinese children is lacking. The aim of the present study was to explore the impact of individual characteristics on maximum IVC diameter (IVCmax), Ao, and IVCmax/Ao in healthy Chinese children. From September to December 2015, 200 healthy children from 1 to 13 years of age were enrolled. IVCmax and Ao diameters were measured by 2D ultrasound. We found that age (years), height (cm), weight (kg), waist circumference (cm), and BSA (m2) were positively correlated with IVCmax and Ao. Multivariate linear regression showed that age was the only independent variable for IVCmax (mm) in female children, height was the only independent variable for IVCmax in male children, and age was the only independent variable for Ao in both females and males. IVCmax/Ao was not significantly influenced by the subjects' characteristics. In conclusion, IVCmax and Ao were more susceptible to subjects' characteristics than IVCmax/Ao. IVCmax/Ao could be a reliable and practical parameter in Chinese children as it was independent of age, height, and weight.

Duplication of the inferior vena cava: case report and a literaturereview of anatomical variation

Anatomical variation in the inferior vena cava can result in misdiagnosis, making a better understanding of suchvariations crucial. Here we report the case of a 29 year-old male, victim of multiple trauma, who in the courseof treatment presented with a pulmonary thromboembolism confirmed by tomography. Given the gravityof the situation and the need for additional surgeries, a decision was made to implant an inferior vena cavafilter. During phlebography, prior to implantation of the filter, the duplication of the vena cava was detectedand classified as a complete duplication. A review of the literature revealed various anatomical descriptions ofduplicated inferior vena cava, the most common of which were incomplete cases showing greater variationin venous contion. All in vivo anatomical descriptions were done via phlebography, demonstrating the valueof this test for the diagnosis of anatomical variation in the abdominal veins. While duplication of the inferiorvena cava was not the cause of the venous thrombosis in our patient, a detailed phlebography test was neededto both identify the anatomical variation and facilitate the placement of the filter to prevent a new pulmonarythromboembolism.

Regional differences in veins wall viscosity, compliance. energetics and damping: analysis of the pressure-diameter relationship during cyclical overloads

Background: The characterization of the dynamic process of veins walls is essential to understand venous functioning under normal and pathological conditions. However, little work has been done on dynamic venous properties. Aim: To characterize vein compliance (C), viscosity (η), peak-strain (W St) and dissipated (W D) energy, damping (ξ), and their regional differences in order to evalúate their role in venous functioning during volume-pressure overloads. Methods: In a mock circulation, pressure (P) and diameter (D) of different veins (anterior cava, jugular and femoral; from 7 sheep), were registered during cyclical volume-pressure pulses. From the P-D relationship, C, W St and ξ (at low and high P-D leveis), η and W D were calculated. Resulls: For each vein there were P-dependent differences in biomechanical, energetics, and damping capability. There were regional-differences in C, η), W St and W D (p<0.05), but not in ξ. Conclusión: The regional-dependent differences in dynamics and energetics, and regional-similitude in damping could be important to ensure venous functioning during acute overloads. The lower C and higher W St and W D found in back-limb veins (femoral), commonly submitted to high volume-pressure loads (i.e. during walking), could be considered relevant to ensure adequate venous system functionality and venous wall protection simultaneously.

Subdiaphragmatic venous stasis and tissular hypoperfusion as sources of metabolic acidosis during passive portal-jugular and caval-jugular bypasses in dogs

Subdiafragmatic venous decompression during anhepatic stage of canine orthotopic liver transplantation attenuates portal and caval blood stasis and minimize hipoperfusion and metabolic acidosis observed with occlusion of portal and caval veins. During two hours, six dogs submitted to portal-jugular and caval-jugular passive shunts, with maintenance of arterial hepatic flow, were evaluated for pH, carbon dioxide tension (PCO2), base deficit (BD) and oxygen tension (PO2) in portal, caval and systemic arterial blood, as well as for increments of BD (DBD) in portal and caval blood. With a confidence level of 95 percent, the results showed that: 1. There were not changes of pH anDBD in portal and systemic arterial blood in the majority of studied times; 2. There was metabolic acidosis in caval blood; 3. The negative increments of BD (DBD) were higher in caval blood than in splancnic venous blood at T10, T30 and T105; and, 4. Deoxigenation of portal and caval blood were detected. Acid-base metabolism and oxigenation monitoring of subdiaphramatic venous blood can constitute an effective way to evaluate experimental passive portal-jugular and caval-jugular bypass in dogs.

Comportamento dos índices dopplerfluxométricos da veia cava inferior fetal em gestaçöes normais / The behaviour of inferior vena cava dopplervelocimetric indexes in normal pregnancy

Trata-se de um estudo transversal que avaliou 134 gestaçöes normais, entre 10 e 40 semanas, em relaçäo ao índice de pulsatilidade para veia (IPV) e ao índice de pico de velocidades para veias (IPVV), medidos na veia cava inferior fetal através da dopplerfluxometria pulsátil. Foi encontrada uma diferença estatisticamente significativa entre as medianas do IPV (p=0,0000) e entre as médias do IPVV (p=0,0000) nas várias faixas de idade gestacional. A análise de correlaçäo mostrou a existência de correlaçöes significativas negativas entre i IPV e a idade gestacional (r=0,74 com o IC 95 por cento -0,64 a -0,81)e entre o IPVV e a idade gestacional (r=-0,57 com o IC 95 por cento: -0,64 a -0,81) e entre i IPVV e a idade gestacional (r=-0,57 com o IC 95 por cento: -0,43 a -0,68). Concluímos que há uma queda dos índices venosos calculados (IPV e IPVV) da veia cava inferior fetal com o avanço da idade gestacional

Desvios porta-jugular e cava-jugular passivos em cães: investigação de pressões sangüíneas / Passive porto-jugular and cava-jugular shunts in dogs: investigation on blood pressures

Os principais objetivos dos desvios veno-venosos durante o transplante ortotópico de fígado são: atenuação da estase venosa subdiafragmática, manutenção do retorno satisfatório de sangue ao coração e perfusão tissular eficiente. Investigações sobre PP, PVCIIH, PVC, PAM e PPR, bem como DPP e DPVCIIH foram conduzidas em seis cães, sob anestesia geral, com fígados perfundidos pela Artéria Hepática, submetidos a desvios porta-jugular e cava-jugular passivos durante 2 horas. Estes desvios não foram capazes de evitar estagnação de sangue na VP e VCIIH, acarretando estase e menor retorno sangüíneo ao coração, sugeridos por aumentos significativos de PP e PVCIIH e quedas significantes nos níveis de PVC. Os valores de PAM não apresentaram diferenças significativas em relação ao tempo T0, na maior parte dos tempos avaliados, enquanto que os valores de PPR foram significativamente menores que os verificados no tempo T0, na maioria dos tempos estudados. Tais pressões mantiveram-se, respectivamente, acima de 100 e 50 mm de Hg, atribuindo-se tais resultados, em parte, à vasoconstricção arteriolar generalizada. Incrementos de pressão na VP (DPP) foram significativamente menos elevados que aqueles verificados na VCIIH (DPVCIIH), atribuindo-se tal diferença à complacência esplâncnica. Decréscimos ulteriores dos níveis de PP e PVCIIH sugerem queda do fluxo arterial para os territórios esplâncnico e sistêmico, decorrente de diminuição do retorno sangüíneo ao coração. Determinações de PP, PVCIIH, PVC, PAM e PPR podem constituir meio prático de avaliação hemodinâmica do desvio veno-venoso.