Mark R. Jackson

Limitations of the Parsonnet score for measuring risk stratified mortality in the north west of England. The North West Regional Cardiac Surgery Audit Steering Group.

OBJECTIVE To study the use of the Parsonnet score to predict mortality following adult cardiac surgery. DESIGN Prospective study. SETTING All centres performing adult cardiac surgery in the north west of England. SUBJECTS 8210 patients undergoing surgery between April 1997 and March 1999. MAIN OUTCOME MEASURES Risk factors and in-hospital mortality were recorded according to agreed definitions. Ten per cent of cases from each centre were selected at random for validation. A Parsonnet score was derived for each patient and its predictive ability was studied. RESULTS Data collection was complete. The operative mortality was 3.5% (95% confidence interval 3.1% to 3.9%), ranging from 2.7% to 3.8% across the centres. On validation, the incidence of discrepancies ranged from 0% to 13% for the different risk factors. The predictive ability of the Parsonnet score measured by area under the receiver operating characteristic curve was 0.74. The mean Parsonnet score for the region was 7.0, giving an observed to expected mortality ratio of 0.51 (range 0.4 to 0.64 across the centres). A new predictive model was derived from the data by multivariate analysis which includes nine objective risk factors, all with a significant association with mortality, which highlights some of the deficits of the Parsonnet score. CONCLUSIONS Risk stratified mortality data were collected on 100% of patients undergoing adult cardiac surgery in two years within a defined geographical region and were used to set an audit standard. Problems with the Parsonnet score of subjectivity, inclusion of many items not associated with mortality, and the overprediction of mortality have been highlighted.

Valvular heart operation is an independent risk factor for acute renal failure

BACKGROUND Acute renal failure (ARF) after cardiac operation with cardiopulmonary bypass is associated with a high mortality rate. The purpose of this study was to determine and quantify whether valvular heart operation is an independent risk factor for developing ARF. METHODS We retrospectively analyzed 5,132 consecutive patients who underwent cardiac operation involving cardiopulmonary bypass between April 1997 and March 2001. Patients with significant renal impairment (preoperative serum creatinine > 200 micromol/L) were excluded. A multivariable logistic regression model was constructed to identify independent risk factors for the postoperative development of ARF. RESULTS In 151 (2.9%) patients ARF developed before hospital discharge. The crude incidence of ARF for isolated coronary artery bypass grafting, isolated valve(s) operation, and valve(s) with coronary artery bypass grafting operation was 1.9%, 4.4%, and 7.5%, respectively (p < 0.001). The results of the logistic regression analysis found that valve operation with or without coronary artery bypass grafting was an independent risk factor for the development of postoperative ARF (odds ratio 2.68, 95% confidence interval 1.89 to 3.79; p < 0.001). Other independent predictors of ARF were increased preoperative serum creatinine levels, urgent or emergent operation, insulin-dependent diabetes, and increased cardiopulmonary bypass time. CONCLUSIONS Valve operation is an independent risk factor for postoperative ARF. This risk is further increased by prolonged cardiopulmonary bypass.

Gastrointestinal complications after aortic surgery

BACKGROUND AND PURPOSE A major gastrointestinal complication (GIC) after aortic surgery may be disastrous, but these complications have received scant attention. This study was performed to determine the risk factors, associated events, and outcomes for patients with GIC. METHODS We performed a secondary analysis of a prospective study that examined 120 consecutive patients who underwent transperitoneal aortic revascularization for aneurysmal or occlusive disease. RESULTS The following 29 GICs developed in 25 patients (21%) within 30 days of aortic surgery: paralytic ileus that required replacement of nasogastric tubes (n = 12), upper gastrointestinal bleeding (n = 5), Clostridium difficile enterocolitis (n = 5), acute cholecystitis (n = 2), mechanical obstruction (n = 2), ascites (n = 2), and colon ischemia (n = 1). Seven patients required operations for GICs after aortic revascularization. A comparison of patients with and without GICs showed no differences in the prevalence of risk factors, presence of mesenteric artery stenoses, coexisting medical illnesses, antecedent gastrointestinal history, operative indication, preoperative fluid administration, or duration of operation. However, patients with GICs had more intraoperative complications (P = .004), greater intraoperative blood loss (P = .02), and more fluids during the postoperative period (P = .008). The mean duration of mechanical ventilation was 71 +/- 23 hours for patients with GICs versus 7 +/- 2 hours for patients without GICs (P = .006). A higher prevalence of pulmonary (P = .004) and renal (P = .001) complications was seen in the patients with GICs. The mean stay in the intensive care unit was 16 +/- 2 days for patients with GICs as compared with 5 +/- 0.4 days for patients without GICs (P < .001). Four deaths occurred, all caused by multisystem organ failure: 3 patients had GICs, and 1 did not have a GIC (P = .007). CONCLUSIONS These results show that GICs are prevalent in transperitoneal aortic surgery and are associated with severe morbidity rates, increased hospital costs because of prolonged stay, and increased mortality rates. Some GICs appear to be associated with intraoperative events that lead to visceral hypoperfusion, and others can be attributed to mechanical causes. However, none of the variables examined in this study were predictive of GICs. In all, GICs should be considered serious adverse sequela after aortic revascularization. Because no risk factors for GICs have been identified, these complications currently cannot be prevented.

The effect off-pump coronary artery bypass surgery on in-hospital mortality and morbidity.

OBJECTIVE Off-pump coronary artery bypass (OPCAB) surgery is being increasingly reported to show better outcomes compared to conventional on bypass grafting. We examined the effect of OPCAB on in-hospital mortality and morbidity, while adjusting for patient and disease characteristics, in four institutions in the North West of England. METHODS Between April 1997 and March 2001, 10,941 consecutive patients underwent isolated coronary artery bypass surgery at these four institutions. Of these, 7.7% were performed off-pump. We used logistic regression to examine the effect of OPCAB on in-hospital mortality and morbidity after adjusting for potentially confounding variables. RESULTS The crude odds ratio (OR) for death (off-pump versus on-pump coronary bypass grafting) was 0.48 (95% confidence interval, CI 0.26-0.92; P=0.023). After adjustment for all major risk factors, the OR for death was 0.59 (95% CI 0.31-1.12; P=0.105). Off-pump patients had a substantially reduced risk of post-operative stroke (0.6 versus 2.3%, respectively; adjusted OR 0.26 (95% CI 0.09-0.70; P=0.008) and a significant reduction in post-operative hospital stay. Other morbidity outcomes were similar in both groups. CONCLUSIONS Off-pump coronary artery bypass incurs no increased risk of in-hospital mortality. In contrast, there is a significant reduction in morbidity in patients undergoing off-pump coronary bypass grafting when compared to that performed on cardiopulmonary bypass.

The progressive nature of peripheral arterial disease in young adults: A prospective analysis of white men referred to a vascular surgery service

OBJECTIVE The onset of symptomatic peripheral arterial disease at a young age (premature PAD) has been associated with rapid progression, bypass graft failure, and amputation. This study was performed to document the incidence of these complications and to determine the risk factors for poor outcome in patients with premature PAD. METHODS This study was designed as a prospective longitudinal analysis, with patients who were ambulatory or hospitalized at a single vascular referral institution. The subjects were 51 white men with onset of PAD symptoms before the age of 45 years (mean age of onset, 41 +/- 0.5 years) and represented consecutive patients who were seen at the vascular surgery service during a 4-year period. Thirty of the study subjects (58%) were recruited during the first 2 years. The main outcome measures were number and type of lower extremity revascularization procedures or amputations that were necessitated during the follow-up period. RESULTS During a mean follow-up period of 73 +/- 6 months, 15 patients (29%) had PAD that remained stable without interventions and 15 (29%) had PAD that remained stable for a mean of 76 +/- 13 months after a single intervention. Twenty-one patients (41%) required multiple operations or major amputations. In a comparison of the 30 PAD patients whose conditions were stable with or without a single intervention with the 21 PAD patients who required multiple interventions (REDO), there were no differences in smoking, hypertension, diabetes, or dyslipidemias. The REDO group had a younger mean age at the onset of symptoms (39 +/- 1 years vs 43 +/- 2 years; P <.001). At entry, the REDO patients had a higher prevalence of infrainguinal or multilevel disease (57% vs 20%; P =.03), a lower mean ankle brachial index (0. 44 +/- 0.04 vs 0.56 +/- 0.03; P =.02), and more frequent tissue loss (24% vs 0; P =.005). The REDO patients had a higher mean lipoprotein (a) level than did the patients with stable conditions (51 +/- 11 mg/dL vs 27 +/- 5 mg/dL; P =.03), but there were no significant differences in the mean plasma homocysteine levels (19 +/- 2 micromol/L vs 16 +/- 1 micromol/L) or in the proportion of patients with hypercoagulable states (33% vs 30%). The only predictive variables that were selected with stepwise logistic regression analysis were age at onset (P <.002; odds ratio, 1.4; 95% confidence interval, 1.11 to 1.81) and ankle brachial index of less than 0.5 (P <.008; odds ratio, 6.4; 95% confidence interval, 1.5 to 27.3). CONCLUSION Although 60% of the white men with premature PAD who were referred to a vascular surgery service had conditions that appeared to remain stable, these data show that approximately 40% of the patients will require multiple interventions because of disease progression or bypass graft failure. Clinical indicators, not serum markers, are predictors of poor outcome in patients with premature PAD. The results of this study suggest that patients with onset of PAD before the age of 43 years who have objective evidence of advanced disease are predisposed to multiple interventions.

Hemostatic efficacy of fibrin sealant (human) on expanded poly-tetrafluoroethylene carotid patch angioplasty: a randomized clinical trial.

PURPOSE The efficacy of solvent-detergent-treated fibrin sealant (human [FSH]) for controlling anastomotic bleeding from expanded polytetrafluoroethylene (ePTFE) patch angioplasty during carotid endarterectomy was evaluated, and FSH was compared with thrombin-soaked gelatin sponge (Gelfoam; TSG). METHODS The study was of a randomized, open-label, single-site, single-treatment, parallel design that took place in a referral center with hospitalized patients. Forty-seven adult patients (33 men, 14 women) underwent elective carotid endarterectomy. Patients were randomized to receive either FSH (N = 24) or TSG (N = 23). FSH was obtained as an investigational new drug. FSH was applied as a liquid by means of a dual-syringe technique. Heparin anticoagulation, patch thickness, and suture type were standardized. Two different needle sizes were used (CV-6, PT-13: N = 21 [FSH: N = 10, TSG: N = 11]; CV-6, PT-9: N = 26 [FSH: N = 14, TSG: N = 13]). The FSH or TSG was applied to the ePTFE patch, and then blood flow was restored through the carotid artery. Degree of anticoagulation was assessed by anti-factor Xa activity. The time from restoration of carotid blood flow until achieving hemostasis was recorded. The blood loss from patch suture hole bleeding was measured. Completion intraoperative duplex ultrasound scanning was performed in all cases. Heparin was reversed with protamine sulfate. The primary end point was successful hemostasis within 15 minutes of restoration of carotid blood flow. The secondary end points were the amount of blood loss caused by suture line bleeding and the time to achieve hemostasis. RESULTS There was no difference in the number of patients with complete hemostasis at 15 minutes (TSG, 13 of 23; FSH, 12 of 24; P =.77). The measured blood loss was 99.0 +/- 119.9 (SD) mL for TSG, and 105.0 +/- 107.9 mL for FSH (P =.86). The time to hemostasis was the same for both groups (TSG, 16.5 +/- 16.5 minutes; FSH, 16.6 +/- 14.2 minutes; P =.97). Within both treatment groups, the use of larger needles (PT-13) was associated with greater blood loss (FSH, 169.7 +/- 124.2 mL; TSG, 172.7 +/- 151.5 mL) than was the use of smaller needles (PT-9; FSH, 58.8 +/- 66.3 mL; TSG, 34.1 +/- 25.6 mL; P =.036, P =.001, respectively). There were no postoperative strokes or bleeding complications in either group. No abnormalities were shown in either group by means of completion carotid duplex ultrasound scanning. CONCLUSION FSH was equivalent, but not superior to, TSG in achieving hemostasis during carotid endarterectomy performed with ePTFE patch angioplasty. Adhesion properties of FSH to ePTFE are possibly different than those to native tissue and warrant additional investigation.

Fibrin sealant in preclinical and clinical studies.

Fibrin sealant, now commercially available in the United States, is a virally inactivated preparation of highly purified human fibrinogen and human thrombin that includes aprotinin to reduce fibrinolysis. Although the product is relatively expensive, cost can be justified when the sealant is used to produce localized hemostasis in surgery in which bleeding cannot be controlled by sutures. Fibrin sealant can also be justified as an alternative to factor concentrates in patients with coagulopathies who have a localized site of bleeding. Newer formulations of fibrinogen and thrombin in a freeze-dried form applied as a bandage may be useful in immediate, on-site treatment of trauma victims in either a civilian or military setting.

Does the choice of risk adjustment model influence the outcome of surgeon specific mortality analysis: a retrospective analysis of 14,637 patients under 31 surgeons

Objectives: To compare implications of using the logistic EuroSCORE and a locally derived model when analysing individual surgeon mortality outcomes. Design: Retrospective analysis of prospectively collected data. Setting: All NHS hospitals undertaking adult cardiac surgery in northwest England. Patients: 14 637 consecutive patients, April 2002 to March 2005. Main outcome measures: We have compared the predictive ability of the logistic EuroSCORE (uncalibrated), the logistic EuroSCORE calibrated for contemporary performance and a locally derived logistic regression model. We have used each to create risk-adjusted individual surgeon mortality funnel plots to demonstrate high mortality outcomes. Results: There were 458 (3.1%) deaths. The expected mortality and receiver operating characteristic (ROC) curve values were: uncalibrated EuroSCORE −5.8% and 0.80, calibrated EuroSCORE −3.1% and 0.80, locally derived model −3.1% and 0.82. The uncalibrated EuroSCORE plot showed one surgeon to have mortality above the northwest average, and no surgeon above the 95% control limit (CL). The calibrated EuroSCORE plot and the local model showed little change in surgeon ranking, but significant differences in identifying high mortality outcomes. Two of three surgeons above the 95% CL using the calibrated EuroSCORE revert to acceptable outcomes when the local model is applied but the finding is critically dependent on the calibration coefficient. Conclusions: The uncalibrated EuroSCORE significantly overpredicted mortality and is not recommended. Instead, the EuroSCORE should be calibrated for contemporary performance. The differences demonstrated in defining high mortality outcomes when using a model built for purpose suggests that the choice of risk model is important when analysing surgeon mortality outcomes.

Gastroesophageal Reflux and Tracheobronchial Contamination After Cardiac Surgery: Should a Nasogastric Tube Be Routine?

Nasogastric (NG) tubes are routinely used in patients undergoing cardiac surgery.This randomized study was designed to assess gastroesophageal reflux (GER) without a NG tube (control) compared with a NG tube managed either by gravity drainage (gravity) or continuous low-grade suction (suction). Antimony pH probes were placed in the lower esophagus and trachea after induction of anesthesia in 51 patients, and pH was recorded every 5 s until the time of tracheal extubation. GER was defined as reversible decrease in esophageal pH to less than 4.0. No significant difference was found between groups in age, weight, gender, duration of postoperative ventilation, morphine use, or antiemetic use. All indicators of GER were seen more frequently in the gravity group compared with the two other groups (P < 0.001). One episode of sudden decrease in tracheal pH was observed in a patient in the gravity group, indicating tracheal aspiration, which was associated with delayed extubation and postoperative pneumonia. The absence of a NG tube is not associated with reflux, probably since the gastroesophageal sphincter remains competent. NG tubes are not routinely necessary for cardiac surgery in patients without risk factors for GER, and increase reflux risk if managed without low-grade suction. (Anesth Analg 1996;83:228-32)

Should we rely on nasopharyngeal temperature during cardiopulmonary bypass

A potential morbidity of incomplete re-warming following hypothermic cardiopulmonary bypass (CPB) is cardiac arrest. In contrast, attempts to fully re-warm the patient can lead to cerebral hyperthermia. Similarly, rigid adherence to 37.0°C during normothermic CPB may also cause cerebral overheating. The literature demonstrates scant information concerning the actual temperatures measured, the sites of temperature measurement and the detailed thermal strategies employed during CPB. A prospective, randomized, controlled study was undertaken to investigate the ability to manage perfusion temperature control in a group of hypothermic patients (28°C) and a group of normothermic patients (37°C). Eighty patients presenting for first-time, elective coronary artery bypass graft surgery (CABG) were randomly allocated to the hypothermic and normothermic groups. All surgery was performed by one surgeon and the anaesthesia managed by one anaesthetist. Temperature measurements were made at the nasopharyngeal (NP) site, as well as in the arterial line of the CPB circuit. The hypothermic group had the arterial blood temperature lowered to 25.0°C to maintain the NP temperature at 28.0-28.5°C. During re-warming, the arterial blood was raised to 38.0°C. Meanwhile, in the normothermic group, the arterial blood temperature was raised to a maximum of 37.0°C to maintain NP temperature at 36.5-37.0°C. Despite strict guidelines, some patients transgressed the temperature control limits. Two patients in the hypothermic group failed to reach an NP temperature of 28.5°C. Twenty-six patients were managed entirely within the control limits. During re-warming in both groups, control of both arterial and NP temperature was well managed with only 25% patients breaching the respective upper control limits. During the re-warming phases of CPB, we were unable to make any correlation between NP temperature and arterial blood temperature, using body weight or body mass index as predictors. Based on the results obtained, we recommend that strict criteria should be implemented for the management of temperature during CPB, in conjunction with more emphasis being placed on monitoring arterial blood temperature as a marker of potential cerebral hyperthermia. We should, therefore, not rely on NP temperature measurement alone during CPB.