Cost analysis of gentamicin-impregnated collagen sponges in preventing sternal wound infection post cardiac surgery.

OBJECTIVE: The use of antibiotic-impregnated sponges (Collatamp) during cardiac surgery is controversial. We analysed the cost-effectiveness of its selective use in patients at high-risk of sternal wound infection (SWI). METHOD: Postoperative costs were analysed in two groups of patients undergoing heart surgery between 2011 and 2013: those with SWI (group 1) and in high-risk patients without SWI (group 2). The potential cost of gentamicin-impregnated collagen sponges (GCS) use in high-risk patients was compared with our current practice. RESULTS: We identified 1,251 patients with at least one recognised risk factor for developing SWI in this period. Of these, 18 developed SWI (incidence 1.4%). The median postoperative cost per patient without SWI was £9,617. The additional cost per patient incurred by SWI was £4,860.75. The annual additional cost for treating patients with SWI was £43,749. With a 50% reduction in SWI, the annual additional cost of treating these patients would be reduced to £21,873. The cost of GCS is £80 per patient. Adding this to £21,873 gives a potential total cost of £71,913 in the treated high-risk cohort. CONCLUSION: In our practice the annual cost of treating SWI in high-risk patients without use of GCS is lower than the annual cost of using GCS in all high-risk patients (£43,749 versus £71,913) if it produces a 50% reduction in SWI. The reduction in the incidence of SWI poses no economic benefit when the cost of the product is factored in.

The sensitivity of the calculation of ΔV to vehicle and impact parameters.

ΔV is frequently used to describe collision severity, and is often used by accident investigators to estimate speeds of vehicles prior to a collision, and by researchers looking for correlations between severity and outcome. This study identifies how ΔV varies over a wide range of input uncertainties allowing the direct comparison of different methods of input data collection in terms of their effect on uncertainty in the calculation of ΔV. Software was developed to implement this sensitivity analysis and was validated against examples presented in the CRASH3 manual. The findings are therefore representative of, and relevant to, commercially available tools such as CRASH3 and AIDamage. It is possible to measure the vehicle and collision parameters with sufficient accuracy to determine ΔV to a level of precision that is useful to predict occupant fatality. In many cases, ΔV is largely insensitive to the input parameter and category values or values determined from photographs may be used. A vehicle specific value of the stiffness parameter B should be used. Direct measurement of crush measurements and vehicle mass (including the best estimates of fluid loss) should be used. Similarly the mass of occupants and cargo should be measured directly rather than estimated from 50th centile values. Calculation of ΔV is sensitive to PDOF which should be measured with a precision of better than ±6°.

Impact of cell salvage during cardiac surgery on the thrombelastomeric coagulation profile: a pilot study.

Intraoperative cell salvage of the cardiopulmonary bypass residual volume can dilute platelets and coagulation factors. This is a report of a randomised control trial of 20 patients undergoing coronary bypass surgery. Residual cardiopulmonary bypass volume was processed and transfused after surgery in the cell salvage group and the residual volume was transfused unprocessed in the control group. The coagulation profile was measured using the Rotem(®) thrombelastometry system. Mean (SD) maximum clot firmness after surgery was 52.8 (5.4) mm in the cell salvage group compared to 57.2 (5.0) mm in the control group (p=0.04). Clot formation time was prolonged after surgery by 39 (27) s in the cell saver group compared to 19 (17) s in the control group (p=0.045). Platelet count was reduced after surgery by 96 (32) x 10(9).L(-1) in the cell saver group and 70 (19) x 10(9).L(-1) in the control group (p=0.03). Blood volume in the chest drains 4 hours after surgery was similar in both groups. There was a strong association between clot formation time after surgery and blood loss (R = 0.68, p=0.001). The increase in blood loss was 4.1 ml for every one-second increase in clot formation time (95% CI 1.9 - 6.4, p=0.001). Cell salvage of the residual cardiopulmonary bypass volume reduced platelet numbers and prolonged clot formation time and maximum clot firmness was less in this group.

Low-impact scenarios may account for two-thirds of blunt traumatic aortic rupture.

BACKGROUND: Traditionally, blunt traumatic aortic rupture (BTAR) is thought to be a high-velocity injury. It was hypothesised that BTAR has a higher than suspected incidence in low-speed accidents, with unique kinematic and demographic risk factors. METHODS: Using the UK Cooperative Crash Injury Study (CCIS) framework, impact profiling was undertaken for accidents involving BTAR. Equivalence Test Speed (ETS) was the parameter used to compare crash severity within comparable impact configurations, as it is a surrogate marker reflecting the net impact forces acting on the vehicle. ETS=40 mph (the threshold used for safety testing within the EURONCAP scheme) was used to delineate low-impact blunt traumatic aortic rupture (LIBTAR) cases, which were subsequently analysed for aetiological risk factors. RESULTS: 119 fully analysed cases of aortic injury were identified from a total of 16,444 cases reported to the UK CCIS between 1998 and 2007. 79 cases (66.4%) qualified as LIBTAR. Risk factors for LIBTAR were age >60 (p<0.0001), lateral impact direction (OR 2.041, RR 1.99, p=0.003), and struck side seat position (OR 1.934, RR 1.885 p=0.101). Low-impact crash scenarios were found to represent more than 95% of UK road traffic accidents. CONCLUSION: Low-impact collisions account for two thirds of fatal aortic injuries. Age >60, lateral impacts and struck side seat position are predictive of LIBTAR. Low-impact cases were associated with minor (potentially subclinical) intimomedial injuries. Therefore, it is recommended that a higher index of suspicion of aortic injury is used in low-impact scenarios in the risk groups identified.

Preoperative intra aortic balloon pumps in patients undergoing coronary artery bypass grafting.

BACKGROUND: The intra aortic balloon pump (IABP) is a mechanical assist device which improves cardiac function. The device has a well-established place in algorithms for managing low cardiac output following cardiac surgery. There is increasing evidence that certain cardiac surgery patients benefit from a period of preoperative augmentation with the intra aortic balloon pump. OBJECTIVES: To determine the effect of the preoperative intra aortic balloon pump on mortality and morbidity in a number of different patients groups undergoing coronary artery bypass grafting. SEARCH STRATEGY: Searches were performed of the following databases: Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library (Issue 1 2005), MEDLINE (2000-2005) and EMBASE (1998-2005). No language restrictions were applied. SELECTION CRITERIA: Randomised or controlled trials of any size or length were included. DATA COLLECTION AND ANALYSIS: Papers were assessed for inclusion by two reviewers independently. Differences were settled by consensus with a third reviewer. Data were extracted and entered into RevMan 4.1, through which a meta-analysis of the data was performed. MAIN RESULTS: Five randomised controlled trials were identified from a total of 765 studies (4 on-pump and 1 off-pump). Data from a total of 193 patients were included in the meta-analysis; all on-pump. Generally, the patients were designated as "high risk" . 105 patients were treated preoperatively with IABP and 88 patients served as controls. There were three hospital deaths in the intervention arm and 18 in the non-intervention arm (odds ratio (OR) 0.16; 95% confidence intervals (CI): 0.06 to 0.4; P<0.0001). Low cardiac index (<2.0 L/min/m2) was noted in 21 out of 105 patients in the treatment arm and 59 patients out of 88 in the non-treatment arm (OR 0.14; 95% CI: 0.08 to 0.25; P<0.00001). A large proportion of the control group had an IABP inserted postoperatively for low cardiac index (52 out of 88). An off-pump versus on-pump analysis was not possible due to the limited number of off-pump studies. However a single well-conducted randomised controlled trial suggested favourable effect of the preoperative IABP in off-pump patients. AUTHORS' CONCLUSIONS: Available evidence suggests the preoperative intra aortic balloon pump may have a beneficial effect on mortality and morbidity in specific high risk patient groups undergoing coronary artery bypass grafting, however, the randomised evidence is from a number of small trials, with a high proportion of unstable patients, recruited at a single institution.

Rupture of the aorta following road traffic accidents in the United Kingdom 1992-1999. The results of the co-operative crash injury study.

OBJECTIVE: The true incidence and survivability of blunt traumatic aortic rupture following road traffic accidents in the UK is unclear. The objective of this study was to determine the extent of blunt traumatic aortic rupture in the UK after road traffic accidents and the conditions under which it occurs. METHODS: Data for the study was obtained from the Co-operative Crash Injury Study database. Road traffic accidents that happened between 1992 and 1999 and included in the Co-operative Crash Injury Study database were retrospectively investigated. RESULTS: A total of 8285 vehicles carrying 14,435 occupants were involved in 7067 accidents. There were 132 cases of blunt traumatic aortic rupture, of which the scene survival was 9% and the overall mortality was 98%. Twenty-one percent of all fatalities had blunt traumatic aortic rupture (130/613). Twenty-nine percent were due to frontal impacts and 44% were due to side impacts. Twelve percent of the blunt traumatic aortic rupture cases in frontal vehicle impacts were wearing seat belts and had airbag protection and 19% had no restraint mechanism. The Equivalent Test Speed of the accident vehicles, (where equivalent test speed provides an estimate of the vehicle impact severity and not an estimate of the vehicle speed at the time of the accident), ranged from 30 to 110 km/h in frontal impacts and from 15 to 82 km/h in side impacts. CONCLUSION: Blunt traumatic aortic rupture carries a high mortality and occurred in 21% of car occupant deaths in this sample of road traffic accidents. Impact scenarios varied but were most common from the side. The use of an airbag or seat belt does not eliminate risk. The injury can occur at low severity impacts particularly in side impact.

Minimal access mitral valve replacement.

Minimally invasive mitral valve surgery has recently been advocated as an alternative to the conventional median sternotomy approach. It has several documented advantages and requires a close relationship betweeen the surgeons, anaesthetist and perfusionist for a successful outcome. This article demonstrates our surgical technique for replacement of the mitral valve. The various aspects of the specialised equipment used are also described.

The mechanism of injury in blunt traumatic rupture of the aorta.

Rupture of the aorta accounts for a significant proportion of fatalities following blunt trauma. A great deal of consensus exists describing the circumstances under which acute traumatic aortic dissection occurs as well as its investigation and management. However, there remains some controversy surrounding the pathogenic aetiology underlying this injury. Univariate and multivariate models of blunt traumatic aortic rupture (BTAR) are discussed. To account for the consistency in the nature of BTAR, despite a range of trauma scenarios, the concepts of dynamic multivariate models and a final common pathway are introduced. Clinical management is described elsewhere. Greater understanding of the mechanism of BTAR could lead to a range of safety systems aimed at a reduction in its incidence and severity.

Bilateral absence of the superior vena cava.

Congenital anomalies of the superior vena cava are rare and often coexist with other cardiac abnormalities. In this report, we present a case of absent bilateral superior vena cava with no associated cardiac anomaly. Blood from the arms, head, and upper torso returned to the right atrium through the azygos vein and the inferior vena cava, mimicking chronic superior vena cava obstruction.

Pulmonary embolism and impending paradoxical embolism: a role for transesophageal echocardiography?

Thrombolysis is advocated as the treatment of choice for hemodynamically important pulmonary embolism. This paper reports the case of a patient with subacute massive pulmonary embolism in which thrombolysis was not considered appropriate because transesophageal echocardiography demonstrated a patent foramen ovale and impending paradoxical embolism.

An experimental study of intra aortic balloon pumping within the intact human aorta.

OBJECTIVE: Intra-aortic balloon pumping is a therapeutic technique which carries a significant morbidity related to the interaction between the balloon catheter and the aorta. The aim of this study was to visualise directly the dynamic action of the balloon catheter within the cadaveric human aorta in an artificial circulation. METHODS: An artificial circulation was constructed using of PVC tubing, a filter and a roller pump. A series of five intact cadaveric human aortas were then individually studied by placing each in series within the circuit. A balloon catheter was advanced via the left common iliac artery into the descending aorta under direct angioscopic vision. Balloon pumping was then commenced. The circuit was perfused with normal saline at a flow rate of 3 l/min. Pump actions of 1:1 and 1:2 were simulated. Each aorta at the end of the experiment was subjected to histological examination. RESULTS: The balloon only appeared to make direct contact with the wall of the aorta during deflation when it was swept to one side by the circulating fluid. During maximal inflation the only points of contact were the tip of the catheter and the entry site. Side branches of the aorta were not occluded by the balloon. There was considerable atheromatous debris visualised within the lumen of the aorta. Atheromatous plaques were seen to fissure and disrupt by a pressure wave action and not by direct contact with the balloon. CONCLUSION: The balloon catheter moves relative to the wall of the aorta during inflation and deflation. Contact between the balloon and the aorta only occurs during deflation. Side branches of the aorta are not occluded by the catheter. Plaque disruption and embolus formation appear to result from pressure wave action rather than direct contact with the balloon. This may have implications for future balloon design. Further investigation of this poorly understood interaction between the balloon and the aortic wall is required.

Vascular remodelling in intramyocardial resistance vessels in hypertensive human cardiac transplant recipients.

OBJECTIVE: Cardiac transplant recipients often develop hypertension as a side effect of immunosuppressive treatment. The aim of this study was to use the serial endomyocardial biopsies taken to monitor rejection to study the early and sequential arterial changes in human myocardial resistance arteries as hypertension develops. METHODS: At least 14 biopsies were studied from each of 23 patients, divided into a normotensive group (12 patients with a diastolic pressure never greater than 90 mm Hg) and a hypertensive group (11 patients with more than 10% of diastolic pressure measurements above 100 mm Hg). Morphometric analysis of between 30 and 50 arteries and arterioles in two widely separated histological levels from each biopsy was undertaken using an Optomax image analyser. RESULTS: There was a correlation between blood pressure, particularly diastolic pressure, and rate of medial thickening of intramyocardial coronary resistance arteries and arterioles (P = 0.0025). There was also a correlation between serum cyclosporin A concentrations and mean artery wall thickness (P = 0.003). CONCLUSIONS: Hypertension and cyclosporin A treatment are associated with significant wall thickening of intramyocardial resistance vessels in cardiac allograft recipients. These changes may be functionally and clinically important.

Infective endocarditis of the tricuspid valve in an orthotopic heart transplant recipient.

A 43-year-old orthotopic heart transplant recipient had coagulase-negative staphylococcus endocarditis 26 weeks after the operation. A diagnosis of endocarditis was confirmed and followed up by serial transoesophageal echocardiography. Treatment with intravenous gentamycin and vancomycin cured her endocarditis, and a 2.5 cm vegetation regressed significantly. She has been well since and, at 14 months after transplantation, was back to her normal activities. Although repeated blood culture yielded only intermittent light growths of coagulase-negative staphylococci, there were several positive samples. In a setting of infective features, light growths of coagulase-negative staphylococcus should be taken seriously if repeatedly positive in heart transplant recipients or other immunocompromised patients. Transesophageal echocardiography offers significant advantages over the transthoracic modality in suspected endocarditis.

Ventilatory and gas exchange abnormalities on exercise in chronic heart failure.

The mechanism of breathlessness on exertion in patients with chronic heart failure are still not fully understood. We therefore investigated the effects of ventilatory and gas exchange abnormalities on exercise capacity in chronic heart failure. Exercise testing was performed in 30 patients with exertional breathlessness due to chronic heart failure and in 30 controls, using continuous transcutaneous blood gas monitoring. Maximal symptom-limited oxygen consumption as (V'O2) as a percentage predicted was reduced in patients (45 +/- 10%; mean +/- SD) compared to controls (87 +/- 7). The ventilatory response (minute ventilation/carbon dioxide production (V'E/V'CO2)) was significantly increased in patients compared to controls (39.9 +/- 7.7 and 25.9 +/- 3.6, respectively). The dead space to tidal volume ratio (VD/VT) was raised in patients compared to controls at rest (0.45 +/- 0.04 vs 0.35 +/- 0.02, respectively) and this persisted on exertion (0.40 +/- 0.05 in patients and 0.20 +/- 0.05 in controls). At maximal symptom-limited exercise, V'E/V'CO2 was inversely related to the % predicted V'O2 in patients, but not in controls (r = -0.62 and r = -0.24, respectively). In patients, V'E/V'CO2 was significantly correlated with VD/VT at maximum exercise (r = 0.82). Patients with chronic heart failure have a significant degree of "wasted ventilation" on exertion, which is associated with increased ventilatory response. The increased ventilatory response on exertion appears to contribute to exercise limitation in these patients.

Arterial lesions associated with medial disorganization and fibrosis in endomyocardial biopsies from human cardiac allografts.

We describe distinctive arterial lesions in endomyocardial biopsies from patients with human cardiac allografts. The lesions affected principally the media of small arteries and consisted of misorientation of smooth muscle cells and fibrosis. This remodelling was most prevalent in the subadventitial zone, but sometimes extended to involve the full thickness of the media. In the most extreme cases medial smooth muscle cells ran parallel to the long axis of the vessel and were segregated into small bundles and single cells separated by collagen which merged with the adventitial fibrosis. The intima was always normal. Abnormal arteries were present in 16% of 603 consecutive biopsies from 44 patients, and 39% of lesions occurred in 16% of patients. No lesions were found in endomyocardial biopsies from 25 non-transplanted patients, nor in mucosal biopsies from both transplanted and non-transplanted patients, confirming that the appearances were not due to biopsy artefact. There was early arterial remodelling in biopsies within two weeks of transplantation and none of the stages resembled vascular rejection. Fifty per cent of biopsies from some patients contained arterial lesions, suggesting that in susceptible patients they are common.

A double-blind placebo-controlled trial of low-dose ganciclovir to prevent cytomegalovirus disease after heart transplantation.

BACKGROUND: The aim of this double-blind, placebo-controlled study was to determine whether a prolonged course of low-dose ganciclovir prevented the development of clinical cytomegalovirus disease after heart transplantation. METHODS: Fifty-six consecutive patients were stratified into two groups: cytomegalovirus-positive recipients (n = 40) and cytomegalovirus-negative recipients of organs from cytomegalovirus-positive donors (n = 16). All patients received equine antithymocyte globulin induction for 7 days and maintenance doses of cyclosporine, azathioprine, and prednisolone. Ganciclovir (5 mg/kg intravenously) or matching placebo was given with the premedication, three times weekly for the first 6 weeks after transplantation and for another 2 weeks for each treated rejection episode between 6 and 12 weeks. RESULTS: Ganciclovir prophylaxis reduced the actuarial incidence of cytomegalovirus disease from 71% to 11% in cytomegalovirus-mismatched patients (p < 0.01). Ganciclovir prophylaxis did not reduce the incidence of cytomegalovirus disease in cytomegalovirus-positive recipients (25% in both placebo and ganciclovir groups) but did delay its onset and reduce its morbidity. There were no adverse reactions during ganciclovir administration. Gastritis was the most common clinical manifestation of cytomegalovirus disease. Pneumonitis and myocarditis were seen only in placebo-treated cytomegalovirus-mismatched patients. All patients with clinical cytomegalovirus disease responded to ganciclovir, 10 mg/kg/day for 2 weeks. CONCLUSIONS: Prolonged low-dose ganciclovir prophylaxis after heart transplantation reduces the incidence of cytomegalovirus disease in cytomegalovirus-mismatched patients and reduces the morbidity of cytomegalovirus disease in cytomegalovirus-positive recipients.

Heart transplantation: initial results in Scotland.

Between 1st Jan 1992 and 1st Sept 1993 164 patients were referred as candidates for heart transplantation in Scotland. 79 were accepted for transplantation and 39 of these received orthotopic heart transplants. 30 day mortality was zero. Mean time on intensive care post operatively was 46.35 hrs and mean time to hospital discharge was 17.03 days. Cumulative actuarial survival (survival at 18 months post operatively) was 87%. There were three deaths, two from infection at six and 19 weeks and one from neoplasia at 37 weeks. Mean time to rejection was 38.54 days. Linear rejection rates at 0-3, 3-6, 6-9, 9-12, 12-15 and 15-18 months were 1.86, 0.94, 0.6, 0.04, 0 and 0 events per 100 pt-days respectively. Linear infection rates at 0-3, 3-6, 6-9, 9-12, 12-15 and 15-18 months were 1.81, 0.17, 0.1, 0, 0.05 and 0.18 events per 100 pt-days respectively. The heart transplant programme in Scotland has been successful in terms of operative mortality and short to medium term survival.