Biomedical subjects

Randall B Griepp

Publications and source records attributed to Randall B Griepp.

25 records · Page 2Linked to original sources

PubMed2002

Effect of hypothermia on cerebral blood flow and metabolism in the pig.

BACKGROUND: The pig has become an increasingly popular model for the study of cerebral protection during cardiothoracic surgery in recent years, but little information is available concerning hypothermic porcine physiology. Because the efficacy of cerebral protection depends largely upon metabolic suppression, we studied cerebral oxygen metabolism at various temperatures using two different methods to assess cerebral blood flow (CBF). MATERIAL AND METHODS: Twelve pigs (7 to 13 kg) underwent cooling on cardiopulmonary bypass to 8 degrees C as recorded by an electrode placed deep in the parenchyma of the brain. CBF was measured in 6 animals using radioactive microspheres and in the other 6 using fluorescent microspheres. CBF, cerebral oxygen consumption, and cerebral vascular resistance were determined at 37 degrees C, 28 degrees C, 18 degrees C, and 8 degrees C. RESULTS: Both methods produced very similar data. CBF fell steadily with decrease in temperature to 18 degrees C but failed to drop further with more profound hypothermia. With both groups combined, mean cerebral oxygen metabolism was 2.63 mL/100 g per minute at 37 degrees C. Metabolic activity was 50% of base line values at 28 degrees C, 19% at 18 degrees C, and 11% at 8 degrees C. The Q10 value in the pig--the degree of metabolic suppression achieved by a 10 degrees C drop in temperature--is 2.46 (95% confidence interval 2.1 to 2.9); this value is consistent with similar studies in humans. CONCLUSIONS: The presence of significant residual metabolic activity at 18 degrees C suggests that this degree of hypothermia may provide incomplete cerebral protection during prolonged interruption of CBF. This study demonstrates that cooling to temperatures below 18 degrees C in the pig can achieve greater metabolic suppression although it may be associated with loss of cerebral autoregulation.

Animals↗

PubMed2002

Replacing the ascending aorta and aortic valve for acute prosthetic valve endocarditis: is using prosthetic material contraindicated?

BACKGROUND: The use of prosthetic material (rather than a homograft) for ascending aorta/aortic valve replacement (Bentall procedure) in cases of acute prosthetic valve endocarditis is controversial. We report favorable results using this technique almost exclusively (a homograft was used in only 3 patients with hematological problems) during a 12-year interval. METHODS: Twenty-eight patients (55 +/- 14 years; 22 male) underwent a Bentall procedure for acute prosthetic valve endocarditis between 1988 and 2000. Twenty-five patients had undergone previous aortic valve replacement (1 with concomitant mitral valve replacement, 4 with coronary artery bypass grafting), and 3 had had a previous Bentall operation. The median interval between initial surgery and reoperation was 13 months (range, 1 to 106). Sixty-eight percent of operations were urgent or emergencies. Ninety-three percent of patients had significant aortic regurgitation; complete annuloaortic dehiscence occurred in 71%, and in 57%, an abscess was found. Causative organisms were identified in 25 of 28 patients: Staphylococcus epidermidis (9), Staphylococcus aureus (7), Streptococcus viridans (6), Pseudomonas (2), and Legionella (1). RESULTS: Twenty-three patients had mechanical and 5 had biological valves implanted during the Bentall procedure. Hypothermic circulatory arrest was used in 64%. Hospital mortality was 11%: there was one intraoperative death, and two before discharge (one cardiac, one sepsis). Eighty-nine percent survived without stroke. During follow-up (median, 44.5 months; complete in 92%), 1 patient died of recurrent endocarditis at 4 months. CONCLUSIONS: These results indicate that prosthetic root replacement may be superior to use of a homograft for acute aortic prosthetic valve endocarditis, with only a 4% incidence of recurrent endocarditis and reoperation.

Adult↗

PubMed2002

Bioprosthetic valved conduit aortic root reconstruction: the Mount Sinai experience.

BACKGROUND: Patients requiring aortic root reconstruction who are deemed unable to take anticoagulants offer unique challenges to the surgeon. For these patients, we have been manufacturing composite conduits intraoperatively using stented bioprostheses. METHODS: During the 10-year period from April 1992 until May 2002, 141 patients (105 male, 36 female) from 34 to 88 years of age underwent aortic root reconstruction with biological valved conduits. Diagnoses included dissection (n = 28, 9 acute type A), degenerative (64), atherosclerotic (32), anuloaortic ectasia (9), endocarditis (5), and other causes (3). Preoperative risk factors included hypertension (90), smoking (63), coronary artery disease (48), and diabetes (6). Valved conduits were mainly constructed from pericardial valves and impregnated Dacron grafts. Distal anastomosis was performed open in all cases except 6; the ascending aorta only was replaced in 63 patients, a hemiarch reconstruction was used in 71, and more extensive arch reconstruction in 7. Additional cardiac procedures were performed in 59 patients. RESULTS: Two deaths occurred in the operating room (biventricular failure). Late hospital mortality was 11 of 141 (7.8%) of which 6 (55%) were cardiac, 2 (18.2%) were infectious, 2 (18.2%) were of other complications and 1 (9.1%) was unknown. Three patients (2.1%) sustained permanent and 3 transient strokes. No structural deterioration of the valve and an approximately 86% freedom from thromboembolic events was observed during 5 years. CONCLUSIONS: For patients for whom anticoagulation is contraindicated or undesirable, reconstruction of the aortic root with a stented bioprosthetic valved conduit offers an acceptable alternative to mechanical prostheses.

Adult↗

PubMed2002

Aortic arch replacement using a trifurcated graft and selective cerebral antegrade perfusion.

BACKGROUND: Aortic arch aneurysm repair remains associated with considerable mortality and risk of cerebral complications. We present results of a technique utilizing a three-branched graft for arch replacement, deep hypothermic circulatory arrest (HCA), and selective antegrade cerebral perfusion (SCP). METHODS: Between March 2000 and November 2001, 22 patients (11 female) aged 40 to 77 years (mean 64 +/- 11.2) underwent arch replacement utilizing the trifurcated-graft technique. Serial anastomosis of the branched graft to individual cerebral vessels was carried out during HCA, followed by arch reconstruction during SCP through the graft. All 22 patients had surgery electively. Eight patients (36%) had undergone previous aortic surgery. In 19 patients, arch replacement was part of an elephant trunk procedure; 2 patients had Bentall operations and 1 had isolated arch replacement. Concomitant coronary artery bypass grafting was performed in 6 patients (27%). Mean HCA duration was 30 +/- 6 minutes at a mean temperature of 11.4 +/- 0.8 degrees C. Mean duration of SCP was 52 +/- 18 minutes. RESULTS: Adverse outcome--death before hospital discharge or permanent stroke or both--occurred in 2 patients (9%). Two patients experienced transient neurologic dysfunction (9%). Two patients (9%) developed renal failure requiring short-term hemodialysis and pulmonary complications occurred in 2 patients. CONCLUSIONS: Cerebral protection and prevention of atheroembolism remain challenges in aortic arch reconstruction. To reduce neurologic complications we developed an aortic arch reconstruction technique in which a trifurcated graft is anastomosed to the brachiocephalic vessels during HCA, reducing the risk of embolization while minimizing cerebral ischemia by permitting antegrade cerebral perfusion as arch repair is completed.

Adult↗

PubMed2002

Impact of high intracranial pressure on neurophysiological recovery and behavior in a chronic porcine model of hypothermic circulatory arrest.

OBJECTIVE: This review was undertaken to determine whether high intracranial pressure (ICP) during reperfusion after hypothermic circulatory arrest (HCA) correlates with evidence of suboptimal cerebral protection in a chronic porcine model. METHODS: In concurrent studies of cerebral protection, 48 control pigs (24-31 kg) underwent 90 min of HCA at 20 degrees C using a strictly standardized protocol. Hemodynamic measurements, ICP and neurophysiological data (EEG, SSEP) were assessed before HCA and until 3 h postoperatively. ICP was measured using a Codman microtip catheter inserted directly into brain parenchyma. Neurological/behavioral evaluation (9=full recovery) was carried out daily through postoperative day (POD) 3. RESULTS: There were no significant hemodynamic or metabolic differences between individual animals. ICP (mmHg) increased significantly for the first 3 h after HCA: from baseline levels of 6.2+/-2.1 to 10+/-2.6 at 1 h, 11+/-3.2 at 2 h and 10+/-3.6 mmHg at 3 h; P<0.001 for the trend. EEG recovery 3 h after HCA was observed in 13 animals (27%), and correlated with lower ICP during reperfusion (P<0.001): with each 1 mmHg increase in ICP at 3 h, the odds of early EEG recovery decreased by a factor of 0.72. Lower ICP during reperfusion was also significantly associated with higher behavioral scores on POD 1 and 2, P<0.001. CONCLUSIONS: A significant rise in ICP may help explain the prolonged obtundation and confusion often seen clinically after HCA. If these small but consistent increases in ICP contribute to rather than reflect ischemic neuronal damage, simple maneuvers to reduce ICP may improve cerebral recovery after HCA.

Animals↗

PubMedDate not supplied

Aortic arch and descending thoracic aortic aneurysms: experience with stent grafting for second-stage "elephant trunk" repair.

Reconstruction of aortic arch and descending thoracic aortic aneurysms (TAAs) is technically challenging and associated with significant morbidity and mortality. We report our experience with extensive TAAs using a two-stage "elephant trunk" repair, with the second stage completed using an endovascular stent graft (ESG). Over 6 years, 111 patients underwent ESG treatment of TAAs at Mount Sinai Medical Center. Twelve of these patients were referred for ESG placement for the second stage of elephant trunk reconstruction because comorbidities placed them at high risk of open surgical repair. Our database was analyzed for technical and clinical success and perioperative complications. The mean follow-up was 11.8 months (range 1-64 months). Twelve patients (five women and seven men) with a mean age of 69 +/- 10 years underwent repair of their distal aortic arch and descending TAAs. These aneurysms included nine atherosclerotic aneurysms, one pseudoaneurysm, and two penetrating atherosclerotic ulcers. Three patients were symptomatic. Stent graft repair was technically successful in 91.7% or 11 of 12 patients. Excessive aortic arch tortuosity resulted in failure to deploy a stent graft in one patient. An antegrade approach through the open elephant trunk was used in two patients with severe iliac occlusive disease. Endoleaks (type 2) were identified in two patients with no aneurysm expansion; however, a 14 mm expansion over 1 year occurred in a patient with no identifiable endoleak. One early mortality occurred in a patient with a ruptured 6 cm infrarenal AAA after successful exclusion of the 8 cm TAA. Second-stage elephant trunk reconstruction of an extensive TAA using an ESG is effective in the short term. Its long-term durability remains to be determined.

Aneurysm, False↗

PubMedDate not supplied

Importance of extrasegmental vessels for spinal cord blood supply in a chronic porcine model.

UNLABELLED: IObjective: Our purpose was to investigate the interaction of the important components of spinal cord blood supply in the pig model to enable its use for future studies of spinal cord protection. METHODS: 25 juvenile pigs (20-22 Kg) underwent serial intercostal (IC) or lumbar artery (LA) ligation until disappearance of motor evoked potentials (MEPs). Pigs underwent sequential craniocaudal (IC/LA ligation alone (n=5); following clamping of both subclavian arteries (n=4)m, or clamping of the median sacral artery (MSA, n=4); preceded by clamping of the subclavian arteries (n=4), or of the MSA (n=4). RESULTS were verified by Tarlov's scores and perioperative angiography. RESULTS: All animals with MEP loss suffered postoperative paraplegia. Groups were equivalent with regard to stable arterial pressures throughout the experiment, temperature and other physiological parameters. Mean number of clamped IC/LA before MEP loss for cranio-caudal clamping direction was 12.8 +/-0.8 for segmental arteries isolated, 9 +/-0.8 if both subclavian arteries were ligated previously and only 4.3 +/- 0.5 IC if the median sacral artery was clamped before. Mean number of clamped LA for caudo-cranial clamping direction was 5.8 +/-0.9 for segmental lumbar arteries, 5.5 +/-0.6 LA if both subclavian arteries were ligated previously and 3.5 +/-0.6 if the median sacral artery was clamped before. CONCLUSION: This study confirms the importance of lumbar and MSA arteries to cord viability. It documents the interaction of the subclavian and MSA (roughly equivalent to the hypogastric arteries in humans) with segmental vessels in providing spinal cord blood supply. It also provides the physiologic basis for use of the pig model for studies of spinal cord protection in aortic surgery.

Animals↗