Not All Piggybacks Are Equal: A Retrospective Cohort Analysis of Variation in Anhepatic Transcaval Pressure Gradient and Acute Kidney Injury During Liver Transplant

Abstract

Objectives: Complete inferior vena cava clamping in caval replacement during liver transplant is associated with substantial physiological derangement and postoperative morbidity. Partial clamping in the piggyback technique may be relatively protective, but evidence is lacking. Having observed substantial variation in transhepatic inferior vena cava pressure gradient with piggyback, we hypothesized that the causative mechanism is the extent of caval clamping rather than the surgical approach. Materials and Methods: We used internal jugular and femoral catheters to estimate suprahepatic and infrahepatic inferior vena cava pressures during clamping. Pressure gradients were calculated, and distributions were compared by surgical technique. We estimated adjusted odds ratios for pressure gradient on acute kidney injury at 72 hours. Results: In 115 case records, we observed substantial variation in maximum pressure gradient; median values were 18.0 mm Hg (interquartile range, 8.0-25.0 mm Hg) with the piggyback technique and 24.0 mm Hg (interquartile range, 19.5-27.0 mm Hg) with caval replacement. Incidence of acute kidney injury was 25% (29 patients). Pressure gradient was linearly associated with probability of acute kidney injury (odds ratio, 1.06; 95% CI, 1.01-1.13). Conclusions: We report 2 novel findings. (1) Anhepatic inferior vena cava pressure gradient varied substantially in individuals undergoing piggyback, and (2) gradient was positively associated with early acute kidney injury. We hypothesize that this (unmeasured) variation explains the conflicting findings of previous studies that compared surgical techniques. Also, we propose that caval pressure gradient could be routinely assessed to optimize real-time piggyback clamp position during liver transplant surgery.

Which cava anastomotic techniques are optimal regarding immediate and short‐term outcomes after liver transplantation: A systematic review of the literature and expert panel recommendations

“…Oliver et al. measured the anhepatic inferior vena cava pressure gradient and found that it varied substantially, with pressure gradient being linearly associated with early acute kidney injury (AKI) 61 . This suggests that renal venous congestion is an etiological factor to post operative AKI.…”

Prospective Cohort Study Assessing the Use of Peripheral Saphenous Venous Pressure Monitoring as a Marker of the Transcaval Venous Pressure Gradient in Liver Transplant Surgery

“…This should result in the repositioning of the clamp, where it is surgically possible to do so, with potential hemodynamic benefits that are likely to impact on renal outcomes. 1 There are some specific patient groups where maintenance of unobstructed venous return throughout the transplant is of critical importance. Patients with significant diastolic dysfunction (frequently seen in cirrhotic cardiomyopathy) or obstructive pathologies, like hypertrophic obstructive cardiomyopathy or inducible systolic anterior motion of the mitral valve, are very sensitive to alterations in preload.…”

“…2,3 This information permits adjustment of the side-biting vascular clamp to decompress the IVC if a piggyback technique has been employed, helps guide fluid management, and also identifies flow obstruction at the IVC anastomoses, which may cause graft dysfunction. We have recently shown that the TCPG during the anhepatic phase of transplant is independently associated with risk of postoperative acute kidney injury, 1 highlighting the clinical importance of this measurement and the value of IVC decompression. However, calculating the TCPG necessitates the insertion of a femoral central line for the purpose of IVC pressure assessment.…”

“…During liver transplant, the inferior vena cava (IVC) is either fully cross-clamped or partially clamped, in the piggyback technique, to allow excision of the native liver and graft implantation. The placement of this clamp leads to an interruption to IVC blood flow, the extent of which depends on surgical technique and clamp positioning, 1 and consequently an increase in IVC pressure. This venous pooling diminishes cardiac output, necessitating increased vasopressor support to maintain perfusion pressure and end-organ oxygen delivery.…”