M. E. Gaunt

A comparison of quality control methods applied to carotid endarterectomy

OBJECTIVESnTo compare the ability of continuous wave Doppler (CWD), B-mode ultrasound (BMU), angioscopy and transcranial Doppler (TCD) to detect technical error during carotid endarterectomy (CEA).nnnDESIGNnA prospective, comparative study in 100 consecutive patients.nnnSETTINGnLeicester Royal Infirmary, Leicester, U.K.nnnMATERIALSnIntraoperative TCD monitoring was performed using a SciMed PcDop 842 2 MHz TCD. An Olympus 2.8mm flexible angioscope was used to inspect the arterial lumen prior to restoration of bloodflow. After restoration of flow 10Mhz BMU images and 8Mhz CWD velocity spectra of carotid artery blood flow were obtained.nnnCHIEF OUTCOME MEASURESnThe detection of intimal flaps, thrombus, stenoses or other errors of surgical technique likely to result in perioperative morbidity.nnnMAIN RESULTSnCWD and BMU images were technically inadequate in 9% and 24% of cases respectively and neither technique altered clinical management. Angioscopy demonstrated significant technical errors in 12 cases (four intimal flaps, thrombus in eight). TCD detected shunt malfunction in 13% of patients, emboli during dissection in 23% and early postoperative carotid artery thrombosis in three patients.nnnCONCLUSIONSnA combination of TCD monitoring and completion angioscopy provided the maximum yield in terms of diagnosing technical error and establishing the cause of perioperative morbidity.

Unstable carotid plaques: Preoperative identification and association with intraoperative embolisation detected by transcranial doppler

OBJECTIVESnTo investigate whether unstable carotid plaque characteristics, as determined by preoperative colour Duplex ultrasonography (CDU) and postoperative histological examination, were associated with particulate embolisation, detected by transcranial Doppler (TCD), during the initial dissection of the carotid bifurcation during carotid endarterectomy(CEA).nnnDESIGNnA prospective, consecutive study was undertaken of 50 patients undergoing carotid endarterectomy(CEA).nnnSETTINGnLeicester Royal Infirmary, Leicester, U.K.nnnMATERIALSnCarotid plaques were assessed preoperatively using CDU. Intraoperative TCD monitoring of the ipsilateral middle cerebral artery was performed using a Scimed 2MHz TCD. Carotid plaques removed at operation were processed histologically and multiple sections assessed microscopically.nnnCHIEF OUTCOME MEASURESnPlaque composition was classified ultrasonically and histologically according to the Gray-Weale classification and plaque surface characteristics were graded according to a five point classification. TCD detected emboli were identified and counted during the initial dissection of the artery.nnnMAIN RESULTSnParticulate embolisation occurred in nine patients. Histologically, embolisation was associated with ulcerated plaque in three cases and ulcerated plaque with associated thrombus in six cases (p = 0.0005). However, the ability of CDU to positively predict embolisation based on the correct identification of an unstable plaque surface was only 25%.nnnCONCLUSIONSnEmbolisation during dissection is strongly associated with ulcerated plaque with associated thrombus. CDU is unable to reliably identify these characteristics preoperatively. Intraoperative TCD monitoring can detect potentially harmful embolisation during this stage enabling surgical technique to be modified appropriately.

Preventing strokes associated with carotid endarterectomy: Detection of embolisation by transcranial doppler monitoring

Intraoperative embolisation has been estimated as the cause of perioperative stroke in up to 80% of carotid endarterectomies (CEA), while reduced cerebral blood flow is responsible for less than 20%. 1 Monitoring or quality control methods which are unable to detect embolisation are unlikely to reduce perioperative mortality and morbidity associated with CEA. Because the majority of monitoring methods are used primarily to detect haemodynamic abnormalities, this may be one reason Why no study has convincingly established the clinical advantage for perioperative monitoring and why a significant number of surgeons performing CEA do not employ this strategy. 2 For any monitoring method to have an impact on perioperative morbidity/ mortality it must detect the majority of abnormalities while there is still time to correct the defect and prevent permanent damage. There is accumulating, evidence that transcranial Doppler (TCD) monitoring can not only detect embolisation, but also that it can identify clinically significant patterns of embolisation early enough to permit therapeutic intervention to prevent stroke. 3 Even surgeons with low perioperative stroke rates have a du ty to ensure that small numbers of preventable strokes are eliminated. The evidence emerging from studies of the perioperative use of TCD may be making the argument that there is no clinical advantage in monitoring more difficult to sustain. The introduction of transcranial Doppler (TCD) monitoring of the middle cerebra ! artery (MCA) during CEA enabled emboli to be detected directly for the first time, whilst simultaneously providing haemodynamic data on the adequacy of cerebral blood supply. 4 Emboli

The Effect of Perioperative Embolisation on Visual Function in Patients Undergoing Carotid Endarterectomy

OBJECTIVESnTo investigate the effect of carotid artery embolisation detected by transcranial Doppler (TCD) monitoring during carotid endarterectomy (CEA) on visual function.nnnDESIGNnA prospective study. Visual function was assessed by an independent ophthalmalogist.nnnMATERIALSnOne hundred consecutive patients undergoing carotid endarterectomy.nnnMETHODSnAll patients underwent pre- and postoperative retinal fundoscopy and automated visual field analysis. Intraoperative emboli were detected by continuous TCD monitoring of the middle cerebral artery.nnnRESULTSnPreoperatively, six patients had fundoscopic evidence of silent retinal embolisation, five patients had visible emboli associated with amaurosis fugax. Visual field analysis found no significant difference between ipsi- and contralateral eye scores. Only patients with occlusions of major retinal vessels had clinically reduced visual function. Intraoperatively TCD identified embolisation in 83/91 of monitored operations. Postoperatively, ipsilateral visual field scores deteriorated while contralateral eye scores remained unchanged, however only one new retinal embolus was detected. The incidence of TCD detected embolisation was not associated with a corresponding deterioration in postoperative visual function.nnnCONCLUSIONSn(1) A group of patients can be identified who experience silent retinal embolisation prior to CEA. (2) Clinically significant retinal embolisation resulting from CEA is uncommon. (3) CEA is associated with a deterioration in the visual field scores for the ipsilateral eye compared with the contralateral eye but the mechanism for this small but significant deterioration remains unclear.