Page 18 - ANZCP Gazette APRIL 2022

COMPARISON OF CEREBRAL EMBOLIC LOAD BETWEEN SINGLE AORTIC CROSS-CLAMP AND PARTIAL AORTIC SIDE-CLAMP TECHNIQUES DURING CORONARY ARTERY BYPASS GRAFTING
Sojin (Jenny) Jeng Auckland City Hospital, New Zealand
Winner of the Syd Yarrow – LivaNova – Award 2021
Abstract:
Cerebral emboli have been associated with post-operative cognitive decline and stroke following cardiac surgery requiring the use of cardiopulmonary bypass (CPB). We conducted a prospective, observational study comparing the cerebral embolic load between two clamp techniques (single aortic cross-clamp (SACC) application versus an additional partial aortic side-clamp (PASC) application) when performing the proximal anastomosis during coronary artery bypass grafting (CABG). This study was part of a larger investigation comparing cerebral arterial emboli exposure on cerebral autoregulation in open-chamber versus closed- chamber cardiac surgery at Auckland City Hospital. Twenty consented patients (n=14 PASC, n=6 SACC) who underwent CABG had emboli (with differentiation to gaseous and solid) monitoring using the Transcranial Doppler (in the left and right middle cerebral arteries) from the initiation of CPB to the termination of CPB. Patients with the use of an additional PASC clamp had a higher number of detected cerebral arterial emboli compared to the SACC use.
Introduction
Cardiac surgeons must choose between two contemporary surgical techniques of using a single aortic cross-clamp (SACC) or an additional partial aortic side-clamp (PASC), along with SACC when performing the proximal aortic anastomosis during CABG. The decision to use either clamp technique involves weighing out the advantages and disadvantages (involving bypass times and myocardial reperfusion times), personal preference and individual patient history.
It is well known that a higher incidence of cerebral emboli coincides with the application and removal of the aortic cross-clamp during CABG (1,2,3,4,5,6).
Cerebral injury is a frequent complication of cardiac surgery and has been associated with high mortality, morbidity, hospital costs and impaired quality of life.
There is a range of severity of injury, like encephalopathy, post-operative cognitive decline (POCD), stroke and subtle neurocognitive dysfunction following cardiac surgery requiring the use of cardiopulmonary bypass (7,8,9). Emboli in this context, may be of gaseous or solid material; and may lodge in the cerebral vasculature blocking blood flow with ischaemia distal to the blockage (10). It can be argued that gaseous emboli are of somewhat less detrimental when smaller in size, although close attention is required to prevent embolic exposure of any kind.
Cerebral emboli are ubiquitous in cardiac surgery and can be introduced from the heart lung machine (HLM) through
cardiotomy suckers, and perfusionist interventions (methods of circuit deairing, giving drugs) (11); or the surgical field (patient factors including intracardiac shunts, deairing techniques, surgical techniques) (12,13). Furthermore, surgical manipulation in cardiac surgery can generate more micro emboli, increasing the risk of cerebral injuries.
To date, there has been a focus on reducing the incidence of embolic load from the CPB circuit (14,15), however, strategies to reduce embolic load from the surgical field have received less attention (16). This study focused on two different surgical techniques relevant to management of emboli generation from the surgical field. Specifically, the difference in cerebral emboli generation between SACC and PASC techniques during CABG requiring CPB was investigated. To our knowledge, we are the first group to explore the difference in cerebral embolic count between the two clamp techniques, with an association to emboli differentiation (gaseous or solid).
Hypothesis
The use of the additional PASC will have a higher cerebral embolic load, when compared to the SACC technique.
Materials and Methods
This prospective observational study was part of a larger study investigating the effect of cerebral emboli exposure on cerebral autoregulation in open-chamber versus closed- chamber cardiac surgery requiring CPB at Auckland City Hospital. All results obtained for the purpose of this research were separately collected and analyzed for discussion. Hence, the result of this study follows written consent and ethics approval by the Southern Health and Disability Ethics Committee (16/STH/157/AM02) and Auckland District Health Board Research Committee (A+7371). Patients scheduled for surgery were enrolled as a sample of convenience based primarily on the availability of the primary author of the larger study to conduct monitoring in the allocated research time.
Out of the 40 patients that were criteria eligible and recruited from the main study (open and closed chamber), 20 patients (n=14 PASC, n=6 SACC) undergoing CABG surgery (closed chamber only) were studied to compare the embolic load (differentiated as gaseous or solid) between two surgical techniques (SACC and PASC). Of note, only male participants were investigated, which was of chance; therefore, our data can only apply to the male population. However, it seems unlikely that patterns of emboli exposure would be influenced by patient gender. Relevant characteristics of the patients are shown in Table 1.
15 APRIL 2022 | www.anzcp.org