Haemodynamic changes during radical nephrectomy with inferior vena cava thrombectomy: A pilot study

Department of Urology, University of Texas Health San Antonio, San Antonio, Texas, USA Department of Cardiothoracic Surgery, University of Texas Health San Antonio, San Antonio, Texas, USA Department of Surgical Disciplines, Baylor College of Medicine, Houston, Texas, USA Department of Anesthesiology and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA Department of Vascular Surgery, Vascular Health Partners Community Care Physicians, Latham, New York, USA Cardiothoracic and Transplant Anesthesiology, University of Texas Health San Antonio, San Antonio, Texas, USA

Renal cell carcinoma (RCC) is amongst the top 10 cancers in the United States, and approximately 10%-15% of these cancer cases are complicated by renal vein and inferior vena cava (IVC) thrombus. 1 An aggressive surgical approach, that is, radical nephrectomy (RN) with IVC thrombectomy, has been associated with a 5-year survival rate of 40%-68%. 2 The venous tumour extension can directly occlude the IVC (entirely or partially), generate venous stasis to create bland thrombus or invade the IVC wall. Over time, progressive occlusion of the IVC leads to reliance on collateral blood flood flow through the lumbar and azygos veins. Intraoperatively, to achieve full control of the IVC for tumour thrombectomy, the surgeon must ligate and control both collateral vessels and occluding tributaries of the IVC, including lumbar, renal, accessory hepatic, retro-hepatic and gonadal veins.
In some instances, cardiopulmonary bypass (CPB) or deep hypothermic circulatory arrest is required. 2 These cases are associated with significant hypotension from a combination of haemorrhage, venous occlusion and embolic events. While hypotension caused by haemorrhage and embolism may be easily detected by the surgical team or by intraoperative transesophageal echocardiography (TEE), the degree of hypotension associated with a decrease in preload due to sequential occlusion of the IVC and venous collaterals is not well characterized. The purpose of this study is to assess the haemodynamic changes that occur during operative steps of RN with IVC thrombectomy to aid the anesthesiologist in the management of expected intraoperative events.
We conducted a prospective observational pilot study of adult patients with RCC and tumour thrombus, who underwent RN with IVC thrombectomy, at a single academic tertiary care hospital in the United States. A sample size of 10 patients was selected a priori. The study was approved by the Institutional Review Board (reference number: HSC20190259E).
Comprehensive perioperative surgical care of these patients at our institution has been previously described. 3 All procedures were performed by a single urologist with the assistance of cardio-vascular surgeons, as indicated. The anaesthesia care included general endotracheal anaesthesia, arterial and central venous catheterization and noninvasive haemodynamic monitoring by an Edwards FloTrack ® system arterial pulse contour analysis monitor. Crystalloids, blood products and vasopressor drugs were administered at the discretion of the attending anesthesiologists and were not standardized. TEE was used in all cases to determine the degree of IVC thrombus extension, to guide application of IVC clamps and to monitor for embolic events.
Once TEE was placed, the cardiac anesthesiologist, urologist and vascular surgeon reviewed the extent of thrombus prior to making any incision. We also evaluated for IVC wall invasion, bland thrombus and distance of proximal limit of thrombus from hepatic veins. These small preoperative maneuvers and closed-loop communication assisted in determining potential problems during the surgery.
Patients' clinical, demographic and perioperative details were recorded. The Mayo clinic thrombus classification was used for describing the level of IVC thrombus. Intraoperative haemodynamic variables included mean arterial pressure (MAP) and stroke volume variation (SVV) measured from radial arterial lines, and cardiac index (CI) and systemic vascular resistance (SVR), as estimated from the FloTrak ® device. Each haemodynamic outcome variable was measured at 10 different pre-defined perioperative time points (Table 1). In patients who required intraoperative CPB, haemodynamic variables collected while on bypass were excluded.
The mean (AEstandard deviation) or median (interquartile range), according to the normality of distribution, was reported for continuous variables. Each haemodynamic outcome at various surgical step was compared to baseline values (defined as the time of IVC exposure) using Wilcoxon rank-sum tests. Analyses were conducted using Stata 13 and a p value of less than 0.05 was considered significant.
Ten patients undergoing open RN with IVC thrombectomy were included. Table 1: provides clinical, demographic and perioperative details along with variations in haemodynamic parameters. Cardiopulmonary bypass was utilized in two patients and those haemodynamic parameters while patients on bypass for these two patients were excluded. The individual haemodynamic parameters, blood loss, vasopressor used and volume of crystalloid and blood products used are shown in Table S1. However, this study has several limitations. It is a pilot observational study with limited sample size and without a comparator group.
Importantly, anaesthetic management was not protocolized. The haemodynamic outcome variables may have been subject to systematic or random measurement error. Moreover, this study never aimed to identify a strategic approach or recommend an intraoperative anaesthetic management plan in patients undergoing RN with IVC thrombectomy. Finally, the clinical significance of statistically care of future patients by helping anesthesiologists anticipate and treat changes in haemodynamics associated with planned surgical steps but may also improve multidisciplinary communication during surgery.