Bypass Shunt Research Articles

Cerebral protection during carotid endarterectomy.

Carotid endarterectomy was performed on 73 occasions using the following regimen during the operative period: (1) general anesthesia with normothermia, (2) maintaining a normal or slightly elevated arterial oxygen tension (Pa o 2 , (3) maintaining a normal or low arterial carbon dioxide tension (P co 2 ), (4) maintaining systemic arterial pressure (SAP) at normal or slightly elevated levels, (5) employing a bypass shunt in all cases, and (6) utilizing transient systemic anticoagulation with heparin. The rationale for this regimen is explained in terms of current concepts of cerebral blood flow and metabolism. No new neurological deficit has appeared after operation using these techniques.

Evidence for the Lack of By-Pass Shunting in Teleost Gills

Retention of 15 μ diameter tracer-labelled microspheres in the gills was studied in some Alaskan teleosts. Neither adrenaline nor acetylcholine significantly affected the percentage retention, as predicted by earlier reports on by-pass shunts affected by these drugs. Rentention of 50 μ microspheres was nearly complete, even under conditions reported to favor shunting. Histological examination of microsphere-treated gills revealed no accumulation in the reported shunt pathways under any conditions. If the shunts do exist, their significance would seem to be slight.

Carotid artery aneurysm associated with nonbacterial suppurative arteritis.

We report a case of true aneurysm of the left common carotid artery in a 34-year-old woman. It was successfully treated with excision and autogenous saphenous graft replacement using hyperoxygenation and internal shunt. Alternate methods of restoration of continuity that were considered are depicted, eg, creation of a permanent shunt between both external carotid arteries, and venous bypass shunt between the proximal carotid and the external carotid arteries. The interesting feature in this case was that microscopic examination of the removed specimen showed suppurative inflammation of the aneurysm. There was no history of systemic or local infection and no organisms could be detected.

Essential Steps in Hepatic Resection

Review of a system of hepatic resection that allows safe, controlled dissection with the maximum opportunities for freedom from uncontrolled bleeding. The complicated steps of utilizing bypass shunts and cold perfusion followed by vascular occlusion are not considered necessary for the majority of resections.

Relation between EEG, regional cerebral blood flow and internal carotid artery pressure during carotid endarterectomy

The EEG was recorded in 52 patients with cerebrovascular disorders selected for reconstructive surgery due to stenosis of the carotid arteries. Changes in cortical activity during 2 min test occlusion of the carotid arteries were related to regional cerebral blood flow and internal carotid artery pressure. The test occlusion induced flattening or slowing of the EEG or both in 14 patients. Flattening occurred when the cerebral blood flow fell to 11–19 ml/100 g/min and when the pressure in the internal carotid artery above the stenosis fell to 15–46 mm Hg. Slowing of the EEG was seen when the regional cerebral blood flow fell to 16–22 ml/100 g/min and the internal carotid artery pressure to 29–50 mm Hg. Measurement of the pressure in the stump of the internal carotid artery is an easy method and is a reliable measure of collateral circulation. It serves as a useful guide to whether or not a temporary by-pass shunt is needed to avoid cerebral ischaemia. Manual frequency analysis of the EEG failed to demonstrate any inter- or intra-individual relation between cerebral blood flow and the mean frequency, probably because of focal cerebral anoxia induced either by the stroke or by the test occlusion.

Reconstruction of the innominate artery by means of a temporary heparin-coated shunt bypass

Reconstruction of the innominate artery by means of a temporary heparin-coated shunt bypass

The use of electroencephalographic monitoring during carotid endarterectomy, as an indicator for the application of a temporary by-pass.

A continuous eeg monitor was used as a means of indicating the adequacy of cerebral blood flow during a trial clamp-off period in patients undergoing carotid thromboendarterectomy. If the eeg indicated a decrease in cerebral function, in spite of the employment of general anaesthesia, moderate hypothermia, induced hypertension and induced hypercarbia, then a temporary by-pass shunt was employed. The management of a typical case is described.

Resection of aneurysms of the descending thoracic aorta using a GBH-coated shunt bypass

Resection of aneurysms of the descending thoracic aorta using a GBH-coated shunt bypass

Continuous Flow-Measurement During Reconstruction of the Carotid Artery

An extravascular bypass shunt with a built-in probe for flow measurement, which permits a continuous measurement, was tested on 11 patients. In most of these cases an adequate flow could be matintained. These patients are included in a material comprising 68 patients. Very careful studies of the haemodynamic have been made in 48 cases with an electro-magnetic flow-measurer and with pressure-measurements. The result of these measurements is under discussion.

Anaesthetic considerations for carotid thrombo-endarterectomy.

Patients presenting for carotid thrombo-endarterectomy have precarious brain perfusion. The anaesthetic approach must not be detrimental to adequate cerebral blood flow. Systemic arterial blood pressure must be maintained. Agents or techniques are avoided which may increase cerebrovascular resistance by affecting blood viscosity, cerebrospinal fluid pressure, cerebrovascular diameter, or body temperature changes. In the preoperative period, a light premedication is advocated to promote early awakening and to maintain a stable respiratory and cardiovascular status. Induction is smooth, with no straining or coughing. An armoured oro-endotracheal tube is used to ensure a patent airway at all times. Maintenance anaesthesia is nitrous oxide, oxygen, and halothane. Thus, cautery may be used. Cerebral vasodilatation tends to occur with halothane. The respiratory tract is not irritated. Early awakening is possible. Gallamine is used to ensure a light plane of anaesthesia and to offset the bradycardia possibly produced by halothane. Also, the carotid sinus reflex, which may be stimulated during surgery, is blocked with gallamine. Use of a muscle relaxant prevents abdominal muscle contractions, which inevitably occur during spontaneous respiration and which may increase central venous pressure and, consequently, cerebral venous pressure. Gallamine facilitates the use of controlled ventilation. By monitoring systemic arterial and internal jugular venous Po2, Pco2, pH, bicarbonate and base excess (Astrup), precise regulation of tidal volume, minute volume (Wright respirometer) and Pco2 at 40-45 mm. Hg is achieved. Moderate hypercarbia tends to increase cerebral blood flow and hyp erventilation; cerebral vasoconstriction and cerebral hypoxia are avoided. A polyethylene surgical shunt bypass is used during the thrombo-endarterectomy. Additional special monitors used are the electrocardiogram, electroencephalogram, central venous pressure, and oesophageal temperature. Low molecular-weight dextran is advocated to decrease viscosity and thus increase cerebral blood flow. Results of carotid thrombo-endarterectomy in the past five years in 60 patients undergoing 78 procedures showed 47, or 78 per cent, with clinical improvement. There were three deaths, giving a mortality rate of 5 per cent. One death was due to a myocardial infarct one month postoperatively. Another patient died from rethrombosis of the internal carotid artery in the early postoperative period. The third death resulted from intracranial rethrombosis with infarction, superimposed on a setting of severe generalized cerebral atherosclerosis.

BYPASS SHUNT--A USEFUL ADJUNCT TO THE TWIN-COIL ARTIFICIAL KIDNEY.

THE artificial kidney developed by Kolff and Watschinger,1 consisting of a disposable, sterile twin-coil dialyzer unit and cellophane circuit tubing, has proved efficient and relatively safe. Hemodialysis by this means, however, is not entirely free of problems. On occasion, incidents requiring attention to the patient or the equipment may necessitate interruption of dialysis. Such delays can often be avoided or minimized by the use of a bypass shunt between the arterial-inflow and venous-outflow lines of the artificial kidney (Fig. 1). By means of the shunt the extracorporeal circulation can be continued, bypassing the patient, or the patient's circulation can be . . .

THE USE OF A BYPASS SHUNT LINE WITH A disc oxygenator

THE USE OF A BYPASS SHUNT LINE WITH A disc oxygenator

A sutureless by-pass shunt in vascular surgery

A sutureless by-pass shunt in vascular surgery

Resection of Aneurysm of Thoracoabdominal Aorta

The major technical problem in the excisional therapy of aneurysms involving the thoracoabdominal aorta is ischemia of vital organs during the construction of new anastomoses to any combination of the celiac, superior mesenteric, and renal arteries. While the duration of complete occlusion of these vessels compatible with healthy survival is not known definitely in man, it is reasonable to assume that the shorter the periods of visceral anoxia the better for the patient. In some instances it has been possible to obtain a relatively brief period of occlusion of the visceral arteries, i. e., 37 minutes, by tangential excision of the aneurysm and reconstruction of the aorta by lateral sutures, as reported by Bahnson. 1 DeBakey and co-workers were the first successfully to apply the principle of a temporary by-pass shunt during resection of the aneurysm and replacement by a homograft. 2 This operation was performed on three patients, two