Graham E. Venn

Alpha-stat acid-base regulation during cardiopulmonary bypass improves neuropsychologic outcome in patients undergoing coronary artery bypass grafting

Neuropsychologic impairment in patients undergoing cardiopulmonary bypass may be associated with cerebral blood flow changes arising from different management protocols for carbon dioxide tension during bypass. Seventy patients having coronary artery bypass grafting were randomized to either pH-stat or alpha-stat acid-base management during cardiopulmonary bypass with a membrane oxygenator. In each patient, cerebral blood flow (xenon 133 clearance), middle cerebral artery blood flow velocity (transcranial Doppler sonography), and cerebral oxygen metabolism (cerebral metabolic rate and cerebral extraction ratio) were measured during four phases of the operation: before bypass, during bypass (at hypothermia and at normothermia), and after bypass. A battery, of neuropsychologic tests were also conducted before and 6 weeks after the operation. During hypothermic (28 degrees C) bypass, cerebral blood flow was significantly (p < 0.001) greater in the pH-stat group (41 mlx100 gm(-1)xmin(-1); 95% confidence interval 39 to 43 mlx100 gm(-1)xmin(-1)) than in the alpha-stat group (24 mlx100 gm(-1)xmin(-1); confidence interval 22 to 26 mlx100 gm(-1)xmin(-1)) at constant pressure and How. Arterial carbon dioxide tensions were 41 mm Hg (40 to 41 mm Hg) and 26 mm Hg (25 to 27 mm Hg), respectively; pH was 7.36 (7.34 to 7.38) and 7.53 (7.51 to 7.55), respectively. Middle cerebral artery flow velocity was significantly (p < 0.05) reduced in the alpha-stat group to 87% (77% to 96%) of the prebypass value, whereas it was significantly (p < 0.05) increased (152%; 141% to 162%) in the pH-stat group. Cerebral extraction ratio for oxygen demonstrated relative cerebral hyperemia during hypothermic (28 degrees C) bypass in both the pH-stat and alpha-stat groups (0.12 [0.11 to 0.14] and 0.25 [0.22 to 0.28], respectively); however, hyperemia was significantly more pronounced in the pH-stat group, indicating greater disruption in cerebral autoregulation. Neuropsychologic impairment criteria of deterioration in results of three or more tests revealed that a significantly (Fishers exact test, p = 0.02) higher proportion of patients in the pH-stat group fared poorly than in the alpha-stat group at 6 weeks (17/35, 48.6% [32% to 65.1%], and 7/35, 20% [6.7% to 33.2.2%], respectively). In conclusion, patients receiving alpha-stat management had less disruption of cerebral autoregulation during cardiopulmonary bypass, accompanied by a reduced incidence of postoperative cerebral dysfunction.

Cardiopulmonary bypass: Perioperative cerebral blood flow and postoperative cognitive deficit

Increased cerebral blood flow occurring during cardiopulmonary bypass as a result of changes in arterial carbon dioxide tension during acid-base regulation is thought to increase postoperative cognitive dysfunction. We studied 70 patients undergoing coronary artery bypass procedures who were randomized to two different acid-base protocols: pH-stat or alpha-stat regulation. Cerebral blood flow, cerebral blood flow velocity, and cerebral oxygen metabolism were measured before bypass, during bypass (hypothermic [28 degrees C] and normothermic phases), and after bypass. Detailed cognitive tests were conducted before operation and 6 weeks after operation. During 28 degrees C bypass, cerebral blood flow was significantly (p < 0.05) higher in the pH-stat group than in the alpha-stat group (41 +/- 2 versus 24 +/- 2 mL.100 g-1.min-1), and cerebral blood flow velocity was significantly increased in the pH-stat group and significantly decreased in the alpha-stat group (152% +/- 10% versus 78% +/- 7%). Cerebral extraction ratio of oxygen demonstrated a relatively greater disruption of autoregulation in the pH-stat group than in the alpha-stat group with relative hyperemia of 0.12 +/- 0.02 versus 0.26 +/- 0.03, respectively, during 28 degrees C bypass. Using the criterion of deterioration in three or more neuropsychologic tests, a significantly higher proportion of patients in the pH-stat group fared less well than in the alpha-stat group (49% +/- 17% versus 20% +/- 13%). Patients in the alpha-stat group experienced less disruption of cerebral autoregulation during hypothermic cardiopulmonary bypass, and this was accompanied by a reduction in postoperative cognitive dysfunction.

Experience with Vacuum‐Assisted Closure of Sternal Wound Infections Following Cardiac Surgery and Evaluation of Chronic Complications Associated with its Use

Abstract  Objectives: We report our experience in use of Vacuum‐assisted closure therapy (VAC) in the treatment of poststernotomy wound infection with emphasis on recurrent wound‐related problems after use of VAC and their treatment. Methods: Between July 2000 and June 2003, 2706 patients underwent various cardiac procedures via median sternotomy. Forty‐nine patients with postoperative sternal wound infection (1.9%) were managed with VAC. Wounds were classified as either superficial sternal wound infection (28 patients) or deep sternal wound infection (21 patients). In the superficial sternal wound infection group, 23 patients had VAC as definitive treatment (GroupA), while five patients (Group B) had VAC followed by surgical closure. Similarly, in the deep sternal wound infection group, 12 patients had VAC as definitive treatment (Group C), while nine patients had VAC followed by surgical closure (Group D). Patients were discharged after satisfactory wound closure. Upon discharge patients were followed up at interval of three to six months. Recurrent sternal problems when identified were investigated and additional surgical procedures were carried out when necessary. Results: There were nine deaths, all due to unrelated causes except in one patient who died of right ventricular rupture (Group C). Nine patients in Group A had recurrent wound problems of which six had VAC system for > 21 days. Three patients underwent extensive debridement due to sternal osteomyelitis. All eight patients in Group B presented with chronic wound‐related problems and underwent multiple debridements. Four patients had laparoscopic omental flaps. In contrast 14 patients (Group B and D) who were treated with shorter duration of VAC followed by either a flap or direct surgical closure, did not present with recurrent problems. Conclusion: VAC therapy is a safe and reliable option in the treatment of sternal wound infection. However, prolonged use of VAC system as a replacement for surgical closure of sternal wound appears to be associated with recurrent problems of the sternal wound. Strategy of use of VAC for a short duration followed by early surgical closure appears favorable.

Hyperperfusion and cerebral dysfunction. Effect of differing acid-base management during cardiopulmonary bypass.

Alterations in cerebral blood flow (CBF) occurring during cardiopulmonary bypass (CPB), which are thought to be responsible for increased morbidity, are probably related to changes in arterial carbon dioxide during acid-base management. In this study, 70 patients undergoing elective coronary artery bypass surgery (CABS) were randomised to one of two differing, but widely practised, cardiopulmonary bypass acid-base protocols; pH-stat and alpha-stat. Cerebral blood flow was measured during surgery using the xenon-133 isotope clearance technique. Cerebral oxygen metabolism was measured as the cerebral metabolic rate for oxygen (CMRO2) and matching of the cerebral blood flow to oxygen demand as the cerebral extraction ratio for oxygen (CERO2). Detailed neuropsychological tests were conducted in all patients before surgery and repeated at 6 weeks after surgery for assessment of changes in cognitive function. During hypothermic (28 degrees C) CPB, CBF was significantly greater (P < 0.001) in the pH-stat group (41 ml/100 g per min; 95% confidence intervals (CI), 39-43) than in the alpha-stat group (24 ml/100 g per min; 95% CI, 22-26). The cerebral extraction ratio for oxygen indicated a degree of mismatch of cerebral perfusion and demand during CPB in both pH-stat and alpha-stat groups (0.12; 95% CI, 0.11-0.14 and 0.25; 95% CI, 0.22-0.28, respectively). This mismatch was far more pronounced in the pH-stat group than in the alpha-stat group, indicating greater disruption in cerebral autoregulation in the former group.(ABSTRACT TRUNCATED AT 250 WORDS)

Bovine pericardial versus porcine stented replacement aortic valves: Early results of a randomized comparison of the Perimount and the Mosaic valves

OBJECTIVE A stented bovine pericardial valve might be less obstructive than a stented porcine valve. This study compared early hemodynamic function in a prospective series of 99 patients randomized to receive either a Mosaic or Perimount replacement aortic valve. METHODS Echocardiography was performed early after surgery and at 1 year after surgery. Patients also filled in psychologic questionnaires and underwent a 6-minute walk. RESULTS The groups were matched demographically. The Perimount valve was significantly less obstructive in terms of mean pressure difference (11 +/- 5 vs 17 +/- 7 mm Hg; P < .0001), with a trend in favor of a larger effective orifice area (1.47 +/- 0.45 vs 1.28 +/- 0.46 cm(2); P = .05) postoperatively. There were no differences in left ventricular mass regression, aortic regurgitation, 6-minute walk, psychologic questionnaires, or mortality and clinical events. CONCLUSION The stented bovine pericardial valve was less obstructive than the stented porcine valve. Both valves were associated with similar and significant improvements in quality of life, exercise ability, and regression of left ventricular mass.

A rare case of aortocoronary dissection following percutaneous transluminal coronary angioplasty: successful treatment using off-pump coronary artery bypass grafting

Retrograde dissection of the aorta is a rare but potentially life threatening complication of percutaneous coronary intervention. We describe a case of retrograde aortic dissection, which occurred during attempted percutaneous transluminal coroanary angioplasty (PTCA) of chronically occluded left anterior descending artery (LAD). Emergency coronary artery bypass grafting (CABG) was performed to revascularise LAD distal to the site of entry tear with pedicled left internal mammary artery (LIMA). This was achieved off-pump. Ascending aorta was not replaced as the dissection was localised.

Effect of differing acid-base regulation on cerebral blood flow autoregulation during cardiopulmonary bypass.

Cerebral dysfunction following cardiopulmonary bypass may be aggravated by altered autoregulation of cerebral blood flow. We have used trans-cranial Doppler to measure middle cerebral artery blood flow velocity during cardiopulmonary bypass managed by either pH-stat or alpha-stat acid-base protocols. Fourteen patients were studied, 7 in each group. During bypass at 28 degrees C, patients underwent incremental alterations in mean arterial pressure from 20-90 mmHg, maintaining systemic perfusion flow at 1.75 L/min per m2. The cerebral extraction ratio of oxygen was measured to indicate matching of cerebral blood flow to demand. The pH-stat group showed a pressure passive cerebral circulation with significant (r = 0.999, P less than 0.05) increase in blood flow velocity with increasing arterial pressure. This also occurred in alpha-stat group during the pressure range of 20-50 mmHg (r = 0.951, P less than 0.05). During the pressure range of 50-90 mmHg in alpha-stat group the change in flow velocity (0.16 cm/sec per mmHg) was significantly (P less than 0.05) less than that in pH-stat group (0.58 cm/second per mmHg). The cerebral extraction ratio of oxygen was less depressed in the alpha-stat group than in the pH-stat group, indicating more appropriate matching of cerebral blood flow and tissue demand. These results suggest that, during alpha-stat managed cardiopulmonary bypass, cerebral blood flow velocity is less subject to wide pressure alteration than pH-stat.

NICE v world on endocarditis prophylaxis

Articles defending the National Institute for Health and Clinical Excellence’s (NICE) advocacy of no antibiotic prophylaxis tend to suggest that the contrary position is universal antibiotic prophylaxis.1 But the essential difference between American, European, and Australian guidelines and those from NICE is in advising antibiotics for high risk cardiac patients (those with …

Mitral valve replacement following a failed MitraClip procedure

While mitral valve surgery remains the gold standard for mitral regurgitation (MR), recent innovative and less invasive procedures like percutaneous MitraClip insertion make treatment options open to patients with end-stage dilated cardiomyopathy and poor left ventricular function, since such a cohort of patients invariably represents a high surgical risk. Enthusiasts of this procedure advocate the use of MitraClip as a primary procedure for patients with Type 1 MR and end-stage cardiomyopathy. Valve repair could be reserved for those patients with ongoing regurgitation following MitraClip insertion. We describe a patient treated by MitraClip insertion in whom the unsuccessful mid-term result necessitated surgery. In this patient, damage to the mitral valve from the MitraClip insertion produced a central leaflet perforation, which precluded repair, and thereby, the patient received a mechanical valve replacement. The enthusiasm for a less invasive initial approach in such patients must be balanced against the risk of failure of the primary procedure so that the patient is not denied the prospect of repair in the first instance.

Percutaneous closure of an iatrogenic puncture of the aortic arch.

AbstractWe report on the management of a rare complication of a vascular sheath being placed inadvertently in the aorta rather than in the venous system following thrombolytic therapy administration in a patient presenting with an acute myocardial infarction and complete heart block.