Can ulnar artery velocity changes be used as a preoperative screening tool for radial artery grafting in coronary artery bypass?

Radial artery harvesting for coronary revascularization may result in digit ischemia if collateral circulation is inadequate. The purpose of this study was to compare changes in ulnar artery flow velocity during radial artery compression (RAC) with changes in first- and second-digit pressures during RAC, a previously validated predictor of digital ischemia. Photoplethysmography was used to measure first- and second-digit arterial pressures before and during RAC on 80 extremities. Color flow duplex imaging was used to measure distal ulnar artery peak systolic velocity before and during RAC. Seventy-eight of eighty extremities had a slight increase in ulnar artery velocity with RAC. There was no correlation between ulnar artery velocity changes and digit pressure changes. Measurement of ulnar artery velocity during RAC is not a useful predictor of digit pressure changes. Measurement of segmental upper extremity pressures with first- and second-digit pressure measurement during radial artery compression should remain the preferred preoperative screening tool for radial artery harvest prior to CABG.

Incidental discovery of an inferior vena cava aneurysm.

Inferior vena cava (IVC) aneurysms are extremely rare, with only 18 reported cases in the world literature. These aneurysms are categorized as acquired, congenital, or associated with arteriovenous fistulae. Thrombosis of an IVC aneurysm can lead to IVC syndrome characterized by massive lower extremity edema, pulmonary embolism, or even death. Therapeutic alternatives range from watchful waiting to operative resection. This report presents a case of an IVC aneurysm noted incidentally at the time of diagnostic computed tomography for the evaluation of blunt chest trauma following a motor vehicle collision. In addition, the classification, embryology, diagnosis, and management of this unusual clinical entity are reviewed.

Regulation of lysyl oxidase by interferon-gamma in rat aortic smooth muscle cells.

Lysyl oxidase is an essential catalyst for the cross-linking of extracellular collagen and elastin. Abnormalities in lysyl oxidase activity may contribute to the pathogenesis of arterial diseases characterized by abnormal matrix remodeling. This study tested the hypothesis that interferon (IFN)-gamma, a proinflammatory cytokine present in aortic aneurysm and arteriosclerotic plaque rupture, downregulates lysyl oxidase gene expression in rat aortic smooth muscle cells. Steady-state lysyl oxidase mRNA levels decreased in a concentration- and time-dependent manner to 30% of control levels after 24 hours of treatment with IFN-gamma. Cell layer lysyl oxidase activity decreased in parallel with the observed changes in steady-state mRNA. Nuclear runoff studies suggested that transcriptional regulation was responsible for at least 40% of the observed downregulation. mRNA decay studies suggested that IFN-gamma also decreased lysyl oxidase mRNA half-life from 9 to 6 hours. Downregulation of lysyl oxidase by IFN-gamma did not appear to require new protein synthesis. This study documents that IFN-gamma downregulates lysyl oxidase gene expression in rat aortic smooth muscle cells by transcriptional and posttranscriptional mechanisms. If similar regulation occurs in vivo, it is possible that IFN-gamma-mediated changes in lysyl oxidase may contribute to arterial diseases characterized by abnormal extracellular matrix.

Noninvasive evaluation of hand circulation before radial artery harvest for coronary artery bypass grafting.

OBJECTIVE: Radial artery harvesting for coronary artery bypass may lead to digit ischemia if collateral hand circulation is inadequate. The modified Allen's test is the most common preoperative screening test used. Unfortunately, this test has high false-positive and false-negative rates. The purpose of this study was to compare the results of a modified Allen's test with digit pressure change during radial artery compression for assessing collateral circulation before radial artery harvest. METHODS: One hundred twenty-nine consecutive patients were studied before coronary artery bypass operations. A modified Allen's test was performed with Doppler ultrasound to assess blood flow in the superficial palmar arch before and during radial artery compression. A decreased audible Doppler signal after radial artery compression was considered a positive modified Allen's test. First and second digit pressures were measured before and during radial artery compression. A decrease in digit pressure of 40 mm Hg or more (digit DeltaP) with radial artery compression was considered positive. RESULTS: Seven of 14 dominant extremities (50%) and 8 of the 16 nondominant extremities (50%) with a positive modified Allen's test had a digit DeltaP of less than 40 mm Hg (false positive). Sixteen of 115 dominant extremities (14%) and 5 of 112 nondominant extremities (4%) with a negative Allen's test had a digit DeltaP of 40 mm Hg or more with radial artery compression (false negative). CONCLUSION: Use of the modified Allen's test for screening before radial artery harvest may unnecessarily exclude some patients from use of this conduit and may also place a number of patients at risk for digit ischemia from such harvest. Direct digit pressure measurement is a simple, objective method that may more precisely select patients for radial artery harvest. Additional studies are needed to define objective digital pressure criteria that will accurately predict patients at risk for hand ischemia after radial harvest.

Differential clinical workloads among faculty at a major academic health center.

OBJECTIVE: The authors analyzed patient care (1981-1995) and financial data (1991-1996) to determine if differential workloads existed at a major academic health center. SUMMARY BACKGROUND DATA: Academic health centers differ markedly from community-based medical centers, but they are required to compete with others who have a more circumscribed mission and a responsibility for providing less complex care. Changes in health care systems may lessen incentives to generate clinical revenue and may adversely affect educational and research programs. METHODS: Patient care data at the University of Michigan Health System were analyzed by discipline for level of activity from 1981 to 1995 and were compared to professional and institutional financial data from 1991 to 1995. RESULTS: Surgeons represented 11% of the total full-time physicians throughout the period of the study (94 of the 836 Medical Center physicians, 1995). They accounted for 33% of hospital admissions (11,616 of 35,101) and 16% of outpatient visits (92,364 of 568,738). Since 1981, surgeons experienced a 249% increase in total operative workload (6799-16,909 procedures), representing a 30% increase in operations/surgeon (138-180 operations). Surgical efforts in 1995 accounted for 29% of the total professional fee revenue and $240 million of the $512-million University of Michigan Hospital revenue. CONCLUSIONS: Surgeons had a greater collective and individual responsibility than did nonsurgeons for clinical activity and the financial viability of the academic health centers studied. Many proposals for financing health care delivery systems have the potential to exacerbate this differential. Restructuring of academic health centers must address this fact, lest their academic mission and scholarly activity be compromised.

Effect of independent changes in mixed-venous PCO2 or PO2 on cardiac output in anesthetized sheep.

To determine whether changes mixed-venous PCO2 or PO2 affect cardiac output independent of changes in arterial blood gases, we used extracorporeal gas exchange to increase mixed-venous PCO2 or decrease mixed-venous PO2 in adult sheep. Sheep were anesthetized, mechanically ventilated, and connected to a veno-venous extracorporeal circuit. The circuit included a gas exchanger which was used to increase mixed-venous PCO2 or decrease mixed-venous PO2; the native lungs were ventilated to maintain arterial PCO2 and PO2 at control levels. When mixed-venous PCO2 was increased by 32% above control levels for a period of 60 min, cardiac output increased significantly to 28% above control levels. Cervical vagotomy abolished this response. In contrast, decreasing mixed-venous PO2 by 29% did not increase cardiac output. These results demonstrate that increasing mixed-venous PCO2 can increase cardiac output independent of changes in arterial blood gases and that intact vagus nerves are necessary for this response to occur.

Bypass grafting for chronic mesenteric ischemia.

A critical analysis of the literature suggests that there is no clearly superior technique for mesenteric revascularization and that the choice of operation must be individualized. Bypass grafting using either an antegrade or retrograde technique with prosthetic or autogenous conduits should produce excellent long-term results for most patients with this complex surgical problem. In most situations multiple vessel revascularizations are preferred. Surgeons caring for such patients must have the ability to utilize all available techniques to ensure optimal outcomes.

Visceral artery aneurysms.

Visceral artery aneurysms are an uncommon form of vascular disease that have a significant potential for rupture or erosion into an adjacent viscera, resulting in life-threatening hemorrhage. During the last decade, hepatic artery aneurysms have become the most commonly reported visceral artery aneurysm. This change likely reflects the increased use of percutaneous diagnostic and therapeutic biliary procedures, as well as increased use of diagnostic computed tomography after blunt abdominal trauma. A second significant development is the increased use of percutaneous catheter-based therapy in the management of visceral artery aneurysms. Nonetheless, a continued aggressive approach to the diagnosis and management of these unusual aneurysms remains warranted.

Transforming growth factor-beta 1 increases lysyl oxidase enzyme activity and mRNA in rat aortic smooth muscle cells.

PURPOSE: This investigation was designed to test the hypothesis that transforming growth factor-beta 1 (TGF-beta 1) regulates lysyl oxidase secretion from vascular smooth muscle cells. Lysyl oxidase is an enzyme that catalyzes an essential step in collagen and elastin cross-linking in the extracellular matrix, and TGF-beta 1 has been implicated in the pathogenesis of restenosis after vascular injury. The effect of TGF-beta 1 on lysyl oxidase in vascular smooth muscle cells has not been previously defined. METHODS: Rat aortic smooth muscle cells were grown in culture to confluence. Cells in passage 2 to 6 were incubated for 24 hours in media containing 0.1, 0.5, 1.0, or 10.0 ng/ml of TGF-beta 1. Lysyl oxidase activity in the media was quantitated with a tritium-release bioassay against an insoluble 3H-labeled aortic clastin substrate. Northern blot analyses were performed to determine steady-state levels of lysyl oxidase mRNA in the smooth muscle cells. RESULTS: Lysyl oxidase activity in the media increased 1.5-fold above control levels after exposure to 10 ng/ml of TGF-beta 1 (p < 0.01). This increase in lysyl oxidase activity was associated with a concentration-dependent increase in steady-state levels of lysyl oxidase mRNA, being 4.3- and 6.2-fold above control levels after exposure to 1 and 10 ng/ml TGF-beta 1, respectively (p < 0.01). The observed increase in steady-state lysyl oxidase mRNA after exposure to TGF-beta 1 was also time-dependent over the 24-hour experimental period. CONCLUSIONS: TGF-beta 1 appears to regulate lysyl oxidase in cultured rat aortic smooth muscle cells. Increases in lysyl oxidase activity may be one of the mechanisms by which TGF-beta 1 contributes to arterial restenosis after vascular injury.

A novel protamine variant reversal of heparin anticoagulation in human blood in vitro.

PURPOSE: Protamine reversal of heparin anticoagulation during cardiovascular surgery may cause severe hypotension and pulmonary hypertension. A novel protamine variant, [+18RGD], has been developed that effectively reverses heparin anticoagulation without toxicity in canine experiments. Heretofore, human studies have not been undertaken. This investigation hypothesized that [+18RGD] would effectively reverse heparin anticoagulation of human blood in vitro. METHODS: Fifty patients who underwent anticoagulation therapy during vascular surgery had blood sampled at baseline and 30 minutes after receiving heparin (150 IU/kg). Activated clotting times were used to define specific quantities of [+18RGD] or protamine necessary to completely reverse heparin anticoagulation in the blood sample of each patient. These defined amounts of [+18RGD] or protamine were then administered to the heparinized blood samples, and percent reversals of activated partial thromboplastin time, thrombin clotting time, and antifactor Xa/IIa levels were determined. In addition, platelet aggregation assays, as well as platelet and white blood cell counts were performed. RESULTS: [+18RGD] and protamine were equivalent in reversing heparin as assessed by thrombin clotting time, antifactor Xa, antifactor IIa levels, and white blood cell changes. [+18RGD], when compared with protamine, was superior in this regard, as assessed by activated partial thromboplastin time (94.5 +/- 1.0 vs 86.5 +/- 1.3% delta, respectively; p < 0.001) and platelet declines (-3.9 +/- 2.9 vs -12.8 +/- 3.4 per mm3, respectively; p = 0.048). Platelet aggregation was also decreased for [+18RGD] compared with protamine (23.6 +/- 1.5 vs 28.5 +/- 1.9%, respectively; p = 0.048). CONCLUSIONS: [+18RGD] was as effective as protamine for in vitro reversal of heparin anticoagulation by most coagulation assays, was statistically more effective at reversal than protamine by aPTT assay, and was associated with lesser platelet reductions than protamine. [+18RGD], if less toxic than protamine in human beings, would allow for effective clinical reversal of heparin anticoagulation.

Extracorporeal life support for neonatal respiratory failure. A 20-year experience.

OBJECTIVE: The authors reviewed their experience with extracorporeal life support (ECLS) in neonatal respiratory failure; they define changes in patient population, technique, and outcomes. SUMMARY BACKGROUND DATA: Extracorporeal life support has progressed from laboratory research to initial clinical trials in 1972. Following a decade of clinical research, ECLS is now standard treatment for neonatal respiratory failure refractory to conventional pulmonary support techniques. Our group has the longest and largest experience with this technique. METHODS: Between 1973 and 1993, 460 neonates with severe respiratory failure were treated using ECLS. The records of all patients were reviewed. RESULTS: Overall survival was 87%. Primary diagnoses were meconium aspiration syndrome (MAS; 169 cases [96% survival]), respiratory distress syndrome/hyaline membrane disease (91 cases [88% survival]), persistent pulmonary hypertension of the newborn (37 cases [92%]), pneumonia/sepsis (75 cases [84% survival]), congenital diaphragmatic hernia (CDH; 67 cases [67% survival]), and other diagnoses (21 cases [71% survival]). Common mechanical complications included clots in the circuit (136; 85% survival); air in the circuit (67; 82% survival); cannula problems (65; 83% survival) and oxygenator failure (34; 65% survival). Patient-related complications included intracranial infarct or bleed (54 cases; 61% survival), major bleeding (48 cases; 81% survival), seizures (88 cases; 76% survival), metabolic abnormalities (158 cases; 71% survival) and infection (21 cases; 48% survival). Since 1989, treatment groups have been expanded to include premature infants (13 cases; 62% survival), infants with grade I intracranial hemorrhage (28 cases; 54% survival) and "non-honeymoon" CDH patients (15 cases; 27% survival). Since 1990, single-catheter venovenous access has been used in 131 patients (97% survival) and currently is the preferred mode of access. Follow-up ranges from 1 to 19 years; 80% of patients are growing and developing normally. CONCLUSIONS: Extracorporeal life support has become standard treatment for severe neonatal respiratory failure in our center (460 cases; 87% survival), and worldwide (8913 cases; 81% survival). The availability of ECLS makes the evaluation of other innovative methods of treatment, such as late elective repair of diaphragmatic hernia and new pulmonary vasodilators, possible. The application of ECLS is now being extended to premature and low-birth weight infants as well as older children and adults.

Traumatic rupture of a cervical parathyroid adenoma.

BACKGROUND: Spontaneous rupture of a hyperplastic parathyroid gland or adenoma resulting in extracapsular hemorrhage is extremely rare. METHODS: We report a case of traumatic rupture of a cervical parathyroid gland adenoma. RESULTS: The patient had progressive stridor, neck swelling, and chest and back pain with evidence of ongoing blood loss resulting in airway compromise. Exploration of the neck and superior mediastinum revealed hypercellular parathyroid tissue consistent with adenoma or hyperplasia. CONCLUSIONS: Traumatic rupture of an enlarged parathyroid gland is a distinct and potentially lethal cause of unexplained cervical or mediastinal hemorrhage after blunt neck trauma. Failure to consider the diagnosis may result in delayed operative intervention with persistent hemorrhage resulting in airway compromise.

The management of acute respiratory failure.

The mortality rate of severe respiratory failure in most centers remains 60% to 90% with conventional pulmonary support techniques. Recent advances in the physiologic management of patients with acute respiratory failure include optimizing systemic oxygen delivery as reflected by continuous mixed-venous saturation monitoring, avoidance of the damaging effects of high inflation pressures and volumes during mechanical ventilation, and the increasing application of extracorporeal life support techniques for refractory respiratory failure. The future promises the routine clinical application of novel support techniques including implantable intracorporeal gas exchange devices and perfluorocarbon liquid ventilation.

Primary unifocalization for the absence of intrapericardial pulmonary arteries in the neonate.

The management of the neonate with absence of intrapericardial pulmonary arteries in association with complex intracardiac anomalies presents a challenging surgical problem. The more traditional approach of palliation with unilateral or bilateral systemic-pulmonary artery shunts may result in peripheral pulmonary artery stenoses and uneven distribution of pulmonary blood flow. In addition, this approach may lead to complicated reconstructive procedures necessitating reconstruction of the branch pulmonary artery with prosthetic material, which restricts pulmonary artery growth and often complicates reoperation. To avoid these potential limitations, we have performed primary unifocalization for absence of intrapericardial pulmonary arteries in eight consecutive neonates (median age 9 days) between May 1990 and December 1991. Absence of intrapericardial pulmonary arteries occurred in association with tetralogy of Fallot (n = 4), truncus arteriosus (n = 2), and transposition of the great arteries with pulmonary atresia (n = 2). Four patients had unilateral absence of the right (n = 1) or left (n = 3) intrapericardial pulmonary artery. In the remaining four patients, there was complete absence of both intrapericardial pulmonary arteries. Wide mobilization and excision of all ductal tissue before anastomosis was performed from a midline approach in seven patients. In one patient, a preliminary right thoracotomy was required. Primary unifocalization was performed simultaneously with complete repair in five patients. In the remaining three patients, unifocalization was part of a staged repair and included insertion of a systemic-pulmonary artery shunt to the reconstructed central pulmonary artery confluence. No operative or late cardiac deaths occurred, although one death occurred during subsequent repair of a tracheoesophageal fistula. Three patients underwent reoperation, and only one patient required revision of an anastomotic pulmonary artery stenosis. All survivors were growing normally at 2 to 22 months after operation (mean follow-up 10 months). Our experience suggests that primary reconstruction for the absence of intrapericardial pulmonary arteries can be successfully accomplished in the neonate. This approach provides uniform bilateral pulmonary blood flow, avoids prosthetic material in the branch pulmonary arteries, and may eliminate, or at least simplify, future reconstructive procedures.

Local production of interleukin-8 is associated with nosocomial pneumonia.

One hundred five (70%) of 151 patients hospitalized in the intensive care unit and undergoing mechanical ventilation had bronchial secretions that tested positive for interleukin-8 within 36 hours of admission. Arterial blood, mixed venous blood, and urine collected simultaneously all tested negative, except for 11 patients admitted with intra-abdominal septic foci. The presence of interleukin-8 in the pulmonary air space early in the course of hospitalization was significantly associated with patients with multiple injuries, the need for greater ventilatory support, the occurrence of pulmonary dysfunction, and a 66% incidence of nosocomial bacterial pneumonia. We conclude that the early local production of interleukin-8 in the lungs is an early marker of pulmonary injury and may be involved in the pathogenesis of nosocomial bacterial pneumonia.

Prolonged extracorporeal circulation without heparin. Evaluation of the Medtronic Minimax oxygenator.

Bleeding remains the most common complication of prolonged extracorporeal life support (ECLS). This study evaluated the Medtronic Minimax (Annaheim, CA) microporous oxygenator with the Carmeda Bio Active (heparin bonded) Surface (Stockholm, Sweden) for use in prolonged neonatal ECLS. Eight adult sheep were maintained on venovenous extracorporeal circulation (ECC) for a period of 4 days without systemic heparin. After 4 days of venovenous ECC without anticoagulation, there was no evidence of significant bleeding, circuit thrombosis, or systemic embolism. Gas exchange, hydrodynamic performance, coagulation, and biocompatibility studies suggest that the Minimax is safe and reliable for short-term or long-term ECLS in neonates.