EComment. Superior caval clamping without a cavoatrial shunt during bidirectional Glenn operation

Abstract

We read with interest the paper by Mostafa et al. [1], in which they presented the results of two groups of single ventricle patients, who underwent bidirectional cavopulmonary anastomosis with and without a veno-atrial shunt. The authors indicate a mean venous pressure of 37.07 ± 7.12 mmHg in the non-shunted group for a mean clamp time of 9.85 ± 3.52 min. The mean intensive care unit stay was 2.57 ± 75 days in the non-shunted patients. The authors performed bidirectional Glenn operation in a cohort of patients aging between 8-108 months [1]. The superior vena cava carries at least half of the blood volume in the early periods of life [2,3]. With growth, the inferior vena cava dominates [3] and proportions become 1/3-4 in adulthood [2,3]. Thus, although superior vena cava clamping may be uneventful in later childhood or adulthood, clamping of the superior caval vein in the early periods of life may not be easily haemodynamically tolerated. The manoeuvre may lead to cardiac failure and an increased amount and number of inotropic agents may be required [2]. Moreover, although authors state the manoeuvre had not led to serious neurologic sequelae during clamping of the superior vena cava, intracerebral pressure increases and cerebral arterial flow diminishes for sure. The literature includes animal experiments of superior vena cava clamping in monkeys [4] and dogs [5]. Research indicates that temporary occlusion of the superior vena cava is safe, despite decreased cerebral blood flow during clamp application [4,5]. First of all, it seems that these experiments were performed on adult animals in both studies [4,5]. Moreover, Masuda et al. indicated histopathological changes in the basal ganglia, hippocampus and even bleeding at the frontal lobe in their experiments on monkeys [4]. Urayama et al. [5] experienced attenuated amplitudes of somatosensory evoked potentials and prolonged latency [5]. We never hesitate to perform cardiopulmonary bypass during bidirectional Glenn procedure at our institution. When an off-pump operation is planned, an external cavo-atrial shunt is created. Despite the shunt, at least 5 mcg/kg/min of dopamine facilitates the surgery. A cavo-atrial shunt with or without minimal dose of inotropic support during reconstruction of the bidirectional Glenn provides a non-adventurous procedure and is a safe technique to decompress the cerebral pressure, to minimize decrease in cerebral arterial blood flow and hence to prevent postoperative neurological events. The cannula inserted into the superior vena cava does not pose major trauma to the superior vena cava and usually does not cause venous distortion or even in case of doubt, the vein can be easily reconstructed. Conflict of interest: none declared.