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Biomedical subjects

R J Baird

Publications and source records attributed to R J Baird.

At least 37 records · Page 2Linked to original sources
PubMed1983

A comparison of volume loading and atrial pacing following aortocoronary bypass.

Although cold potassium cardioplegia provides adequate myocardial protection, transient hemodynamic and metabolic instability occasionally occurs after uncomplicated coronary bypass surgery. Two methods to increase cardiac output were compared 2 to 6 hours postoperatively in 24 patients recovering from elective coronary bypass operation. Volume loading increased cardiac index (CI) from 2.1 +/- 0.5 to 2.7 +/- 0.6 L/min/m2 by increasing left atrial pressure (LAP) from 8.6 +/- 3.6 to 13.0 +/- 4.1 mm Hg. Atrial pacing at a rate of 112 +/- 8 beats per minute increased CI from 2.4 +/- 0.5 to 2.7 +/- 0.8 L/min/m2 without a change in LAP. Ejection fraction by nuclear angiography did not change, but the calculated left ventricular end-diastolic volume index (stroke index/ejection fraction) increased with volume loading and decreased with atrial pacing--a decrease in diastolic compliance. Myocardial oxygen extraction did not change, but myocardial lactate extraction increased with volume loading and decreased with atrial pacing. Coronary sinus blood flow was measured in 5 patients and increased with both methods studied. Volume loading demonstrated that myocardial performance was normal and myocardial metabolism increased commensurate with the increase in work. Atrial pacing increased CI but resulted in anaerobic metabolism and a decrease in diastolic compliance. Volume loading rather than atrial pacing will improve CI without producing ischemia in the early postoperative period.

Adult↗
PubMed1983

Improved myocardial protection during a prolonged cross-clamp period.

Severe coronary stenoses limit delivery of cardioplegic solution to ischemic regions in patients undergoing bypass operations. A prospective randomized trial was undertaken to determine whether the construction of proximal as well as distal anastomoses during a prolonged cross-clamp period would provide more uniform cardiac cooling and better myocardial protection. Ninety-one consecutive patients undergoing elective coronary bypass operations were randomized into two groups. The long cross-clamp technique was used in 46 patients (Group 1), and a proximal anastomosis was constructed after each distal anastomosis. The short cross-clamp technique was employed in 45 patients (Group 2), and distal anastomoses were constructed during aortic occlusion. Cardiopulmonary bypass time was identical, but the cross-clamp period was longer in Group 1 (59 +/- 15 minutes versus 46 +/- 17 minutes in Group 2; p less than 0.001). The mean temperature in the most ischemic region was colder with the long cross-clamp technique (12.5 +/- 3.1 degrees C in Group 1 versus 14.8 +/- 3.2 degrees C in Group 2; p less than 0.01). The total amount of the myocardial isoenzyme of serum creatine kinase released was greater in Group 2 than in Group 1 (332 +/- 34 IU/L per hour in Group 1 versus 469 +/- 45 IU/L per hour in Group 2). Thirty-six patients had coronary sinus catheters inserted (18 patients in each group). Myocardial lactate extraction returned to normal sooner in the patients who had a long cross-clamp period; time to a normal lactate extraction was 0.8 +/- 0.8 hours in Group 1 versus 2.2 +/- 2.1 hours in Group 2 (p less than 0.001). Volume loading and atrial pacing 2 to 4 hours postoperatively produced a similar hemodynamic response in the two groups, but myocardial lactate extraction increased in Group 1 and decreased in Group 2 (p less than 0.05). The construction of proximal as well as distal anastomoses during a prolonged cross-clamp period produced more uniform cooling and improved myocardial protection.

Constriction↗
PubMed1983

Optimal postoperative volume loading.

Intravenous infusions are required to maintain ventricular preload after uneventful coronary bypass operation. During the early postoperative period, when myocardial metabolic recovery is incomplete, volume loading is intended to stabilize ventricular function and metabolism and to prevent progressive ischemic injury. This study attempts to define the optimal preload for both metabolism and performance. Thirty-seven patients recovering from elective coronary bypass operations and cold potassium cardioplegia underwent volume loading with whole plasma. The initial response (VLA) from a low left atrial pressure (LAP = 7.3 +/- 3.3 mm Hg) was compared with the subsequent response (VLB) from a higher filling pressure (LAP = 10.9 +/- 2.7 mm Hg). Both VLA and VLB produced a similar increase in cardiac index, stroke work index, and end-diastolic volume index (EDVI), and a decrease in ejection fraction (measured by nuclear angiography). Myocardial lactate extraction increased with VLA, but myocardial lactate production resulted with VLB. A careful analysis of these volume loading studies suggested that myocardial performance and compliance were not altered in the early postoperative period. The decrease in ejection fraction with volume loading may have resulted from a combination of increased wall tension and decreased inotropic stimulation. After uneventful coronary bypass surgery, an LAP between 5 and 12 mm Hg corresponded to an EDVI between 30 and 80 ml/m2 and produced adequate cardiac index, stroke work index, and lactate extraction. A lower or higher preload did not improve function and resulted in abnormal metabolism.

Coronary Artery Bypass↗
PubMed1983

Effects of postoperative hypertension and its treatment.

Hypertension following aorta-coronary bypass operations can contribute to myocardial ischemia. Nitroprusside therapy will reduce afterload, preload, and coronary perfusion pressure. Since both hypertension and its treatment can result in ischemic injury, nitroprusside must be carefully titrated to optimize cardiac function and metabolism. Thirty-one patients undergoing elective coronary bypass grafting were studied during a hypertensive episode (mean arterial pressure [MAP] = 119 +/- 18 mm Hg) and during nitroprusside therapy at an MAP of 97 +/- 11 mm Hg and at an MAP of 80 +/- 11 mm Hg (normotension). Nitroprusside also produced a significant (p less than 0.05) decrease in left atrial pressure (LAP), left ventricular end-diastolic volume index (EDVI) (stroke index divided by ejection fraction by nuclear angiography), stroke index, and stroke work index (SWI). Cardiac lactate extraction (LEx) and the ratio LEx/SWI increased (p less than 0.05) with the initial nitroprusside therapy, but lactate production resulted when the MAP was lowered to 80 mm Hg. Volume loading studies were performed during hypertension in four patients and during nitroprusside therapy in 15 patients. Neither performance nor compliance was significantly altered at an MAP of 97 mm Hg, but compliance decreased at normotension. Both hypertension and its treatment can result in inadequate myocardial metabolism. Nitroprusside should be titrated to maintain MAP between 90 and 100 mm Hg.

Adult↗
PubMed1983

Comparison of alternative cardioplegic techniques.

Cold potassium cardioplegia provides adequate protection for coronary bypass operations, but severe coronary stenoses limit cardioplegic delivery to ischemic regions. The traditional technique delivers cardioplegic solution into the aortic root during the performance of distal anastomoses. The proposed alternative technique constructs proximal as well as distal anastomoses during a prolonged cross-clamp period, but permits more uniform cooling. The two techniques were compared in a prospective concurrent trial of 45 patients undergoing elective coronary bypass grafting. The traditional technique was employed in 26 patients (Group A) and the alternative technique in 19 patients (Group B). In both groups, 700 to 1,000 ml of a crystalloid cardioplegic solution was infused into the aortic root after application of the aortic cross-clamp. In Group A (traditional technique), 500 ml was infused into the aortic root after each distal anastomosis. In Group B (alternative technique), cardioplegic solution was administered through the vein graft after each distal anastomosis, and a proximal anastomosis was constructed after distal anastomoses to the most ischemic regions to permit continued cardioplegic delivery to these regions. The cross-clamp period was shorter in Group A than in Group B (44 +/- 15 versus 60 +/- 18 minutes, p less than 0.01), but the mean temperature in the most ischemic region was warmer (Group A, 19 degrees +/- 3 degrees C; Group B, 15 degrees +/- 3 degrees C, p less than 0.05). The postoperative CK-MB was higher in Group A (Group A, 47 +/- 36; Group B, 21 +/- 9 IU/L, p less than 0.01). Cardiac lactate production persisted longer in Group A (Group A, 4 +/- 1; Group B, 1 +/- 1 hours postoperatively, p less than 0.05). Volume loading 4 hours postoperatively produced a similar increase in left atrial pressure and cardiac index in both groups. In response to volume loading, Group A patients produced lactate, but Group B patients extracted lactate (change in cardiac lactate extraction: Group A, -1.7 +/- 2.3; Group B, +2.5 +/- 5.1 mg/dl, p less than 0.05). The construction of proximal as well as distal anastomoses during a prolonged cross-clamp period permits more uniform cooling and immediate reperfusion. This alternative technique resulted in less injury (CK-MB release) and more rapid recovery of myocardial metabolism.

Aged↗
PubMed1983

Survival following complete detachment of an end-to-end aortic anastomosis.

A 78-year-old man had complete dehiscence of the suture line of the aorta to a prosthesis, 8 years after standard repair of an abdominal aortic aneurysm. For 6 months, until the aortic was reconstructed, the patient had no hemorrhage or limb ischemia because a conduit was maintained by the original aneurysm wall which had been wrapped around the prosthesis. The authors believe this is the first report of survival following such dehiscence. They advocate the use of non-absorbable sutures when anastomosing the graft to the aorta and repair rather than resection of abdominal aortic aneurysms.

Aged↗
PubMed1982

Transluminal dilation. An alternative?

In a prospective study, 384 peripheral arterial transluminal dilations were evaluated, using clinical and vascular laboratory criteria, and analyzed by the life-table method. The overall cumulative success rate was 58.9 +/- 3.3% (mean +/- SEM) after two years but was higher if the iliac segment was dilated, only one site was dilated, the clinical indication was claudication, the distal vessels were normal, the ankle-brachial BP ratio was more than 0.35, or if the patient was younger than 55 years. The complication rate was 3.9%. If the dilation failed, the symptoms were worse in 8% and the ankle-brachial BP ratio fell in 23%. After successful dilation in patients with normal distal vessels, residual claudication persisted in 34%, and the ankle-brachial BP ratio remained abnormal in 40%. Although the overall success rate of transluminal dilation was lower than for a comparable surgical procedure, dilation does have a role in the management of localized peripheral vascular disease.

Actuarial Analysis↗
PubMed1982

Pericardial graft for intraoperative balloon pump insertion.

A technique that permits rapid insertion of an intraaortic balloon pump to support patients who cannot be successfully weaned from cardiopulmonary bypass is described. A pericardial patch is obtained while the sternum is still open, and is sutured to a common femoral arteriotomy. A 6-0 Prolene mattress stitch is inserted at the heel and continued along the sides. The ends are tied at the toe, and the same suture is used to construct a tube of pericardium over the balloon catheter. A single heavy silk suture is placed around the pericardial graft to prevent bleeding. The technique helps prevent thrombus and avoids infectious complications. It reduces the incidence of vascular complications and makes use of the Fogarty catheter after balloon removal unnecessary. We have used the method in 9 patients since November, 1979, without problems.

Assisted Circulation↗
PubMed1982

Cardioplegia for severe coronary artery disease: an improved technique using direct coronary artery infusion.

Conventional techniques of cardioplegic solution administration result in regional disparities in the level of myocardial protection in patients with severe coronary artery disease. This report describes a simple adjunct to conventional transaortic administration of cardioplegic solution, in which additional solution is introduced directly through the coronary arteriotomy used for the vein graft anastomosis. The supplemental infusate is delivered through s small-caliber flexible catheter. This technique permits effective perfusion of the coronary vascular bed distal to severely stenotic and occlusive lesions. Using an experimental model of physiologically significant coronary arterial stenosis, we compared the effectiveness of this technique with that of conventional techniques of cardioplegia.

Animals↗
PubMed1981

The hemodynamic and metabolic response to pacing after aortocoronary bypass.

Long-term follow-up of aortocoronary bypass has shown good preservation of ventricular function. However, myocardial reserve in the immediate postoperative period may not be optimal. Nineteen patients who underwent elective aortocoronary bypass protected with cold potassium cardioplegia were studied in the early postoperative period at rest and during the stress of atrial and ventricular pacing. Performance was assessed by hemodynamic, metabolic and nuclear angiographic measurements. In the first 2--6 hours after aortic cross clamping, myocardial performance was preserved at rest and there was no evidence of ischemic metabolism. Atrial pacing at a rate of 119 beats/min caused a significant increase in cardiac index (p less than 0.01) without deterioration in hemodynamics, ejection fraction or metabolic status. At the same rate, ventricular pacing did not change the cardiac index and there was a decrease in hemodynamic function. Ejection fraction decreased from 56% to 44% (p less than 0.05) without a change in end-diastolic volume. Lactate, pyruvate and beta hydroxybutyrate extractions were changed to net production. Ventricular performance was preserved at rest immediately after aortocoronary bypass done with multidose cold potassium cardioplegia, with adequate reserve to meet the stress of atrial but not ventricular pacing. We conclude that the therapeutic implications of the type of pacing selected in the immediate postoperative period may be important.

Atrial Function↗
PubMed1981

Ascending aorta to bifemoral artery bypass.

In certain patients the standard bypass procedure for aortoiliac occlusion is unsuitable. Included in this group are those who are obese, who have horseshoe kidneys, abnormal renal arteries, large incisional hernias, thoracoabdominal coarctation, failed previous aortoiliac repair or who have undergone multiple laparotomies. Since 1975 the authors have operated on 16 such patients to construct a bypass graft from the ascending aorta to the femoral arteries without entering the abdominal cavity. The new ventral aorta follows the natural anastomotic axis of the mammary and epigastric arteries, behind the rectus muscle and in front of the posterior rectus sheath. The operation is simple and effective and is especially applicable to the patient with obstruction of both the coronary and aortoiliac arteries.

Adult↗
PubMed1981

Comparison of conduits for leg revascularization.

The saphenous vein (SV) remains the conduit of choice for lower limb revascularization. When SV is unavailable, or unsuitable, two alternative conduits have been employed: gluteraldehydestablized human umbilical vein (HUV) and polytetrafluoroethylene (PTFE). In this study of the 218 patients who underwent lower limb revascularization, 3-year patency of 85 SV graft was 75% compared to 34% for the 66 HUV grafts and 33% for the 67 PFTE grafts. Three factors were found to independently influence patency: the indication for surgery, the site of the distal anastomosis, and the angiographic runoff. The SV group had significantly better patency than either HUV or PFTE in each of these subgroups. No consistent difference between HUV and PTFE was found. A risk score was obtained by assigning a value of 1 to 3 for each of the factors influencing patency--indication: 1 = claudication, 2 = rest pain, 3 = ischemic lesions; site: 1 = above knee (AK), 2 = below knee (BK), 3 = tibial; runoff 1 = good (two or three vessels), 2 = fair (one vessel), 3 = poor (no vessel). Patients with the lowest risk scores (3 to 4) had the best 3-year patency: SV, 78%; HUV, 44%; and PTFE, 48%. Patients with the highest risk scores (7 to 9) had the worst 3-year patency: SV, 68%; HUV, 32%; and PTFE, 28%. SVs had better patency under high- and low-risk conditions and remain the conduit of choice for lower limb revascularization. Both HUV and PTFE have equivalent and acceptable patency when SV is unavailable or unstable.

Blood Vessel Prosthesis↗
PubMed1980

Surgical treatment of annuloaortic ectasia.

Twenty-two patients with annuloaortic ectasia (an aneurysm of the ascending aorta and aortic valve incompetence) due to cystic medionecrosis underwent surgical repair between 1967 and 1979. Twelve patients had Marfan's syndrome and 4 had a forme fruste. The use of a valved conduit and improved techniques of myocardial protection have reduced the perioperative risks and may improve the survival of these patients. Between July 1, 1967 and June 30, 1978, 12 patients had supracoronary repair of the aneurysm and replacement of the aortic valve (group 1); the mortality was 17% (2 of 12). Between July 1, 1978 and Aug. 31, 1979, 10 patients underwent insertion of a valved conduit with implantation of the coronary arteries (modified Bentall procedure, group 2); the operative mortality was 10%. In five group 1 patients (42%) and two group 2 patients (20%) technical problems resulted in bleeding in the early postoperative period. Evidence of a recurrent aneurysm in the diseased segment of the proximal aorta developed in 2 of the 10 group 1 survivors, at 2 and 4 years after operation, respectively. Use of the modified Bentall procedure and cold potassium cardioplegia reduced operative complications from 58% (7 of 12 in group 1) to 20% (2 of 10 in group 2). Because of the low risk of the current procedure and the high risk associated with its natural history, operative intervention should be considered for asymptomatic patients with annuloaortic ectasia.

Adolescent↗