Joel Dunning

A validated rule for predicting patients who require prolonged ventilation post cardiac surgery

OBJECTIVE Prolonged ventilation post surgery causes logistic problems on cardiac surgical intensive care units (CSU). We thus sought to derive and validate a clinical decision rule to predict patients at high risk of prolonged ventilation, so that the timing of operations on high risk patients can be optimised in the context of the workload of the CSU. METHODS The North Staffordshire Royal Infirmary (NSRI) Open Heart Registry was analysed from April 1998 to May 2002. Prolonged ventilation was defined as that which was longer than 24 h. The Parsonnet score was assessed for its ability to predict these patients. Univariate analysis was first performed to identify predictive variables. Recursive partitioning and logistic regression was then performed to identify the optimal decision rule. This rule was then validated on the Blackpool Victoria Hospital (BVH) Open Heart Registry. RESULTS A total of 3,070 patients were analysed of whom 201 were ventilated for more than 24 h. A Parsonnet score of 10 predicted 49% of high risk patients but 618 low risk patients are misclassified. Our rule that uses Parsonnet score over 7, ejection fraction, operation status, PA pressure and age, to identify high risk patients identifies 50% of those needing prolonged ventilation and only incorrectly identifies 282 of the 2869 patients with normal ventilation times giving a specificity of over 90%. Validation in the BVH database demonstrated similar findings. CONCLUSION Our rule identifies 14% of all our patients as high risk and 50% of these required prolonged ventilation. Such a rule allows more efficient use of scarce CSU resources by appropriate surgical scheduling.

In patients post cardiac surgery do high doses of protamine cause increased bleeding

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether high doses of protamine causes increased bleeding in patients post cardiac surgery. Altogether 268 papers were found using the reported search, of which five presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. We conclude that high doses of protamine can cause increased bleeding and impaired platelet function but these effects have never been demonstrated below a ratio of 2.6:1 protamine to heparin.

Is the figure-of-eight superior to the simple wire technique for closure of the sternum?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed is whether the figure-of-eight technique is superior to the simple wire technique for closing of the sternum? Altogether 111 papers were found in Medline of which seven presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. We conclude that the figure-of-eight wire technique is not superior to the simple wire technique for closure of the sternum.

Does liberal use of bone wax increase the risk of mediastinitis

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether bone wax increases the risk of mediastinitis in patients undergoing cardiac surgery. Altogether 276 papers were found using the reported search, of which five presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. We conclude that animal studies indicate that there are strong reasons for concern over the liberal usage of bone wax.

Derivation and validation of a clinical scoring system to predict the need for an intra-aortic balloon pump in patients undergoing adult cardiac surgery.

The spectrum of patients receiving cardiac surgery are increasing in age and severity of illness. With the reduction of complications caused by the placement of an intra-aortic balloon pump (IABP) there is increasing interest in the placement of an IABP prophylactically. We sought to derive a scoring system to guide the placement of IABPs. A total of 3927 patients from the Blackpool Victoria Open Heart Registry were used to derive a range of clinical decision scores using a range of established and novel statistical techniques. This database included 127 patients who received an IABP. The derived scores and rules were then validated on the North Staffordshire Open Heart Registry, containing 3070 patients, and 161 patients who received an IABP. We derived and validated a clinical score that has a sensitivity of 50% and a specificity of 96.5% in the prediction of those patients requiring an IABP. This was robust in the validation dataset and outperformed the Parsonnet score in this context. Our validated clinical scoring system will be useful both to guide individual clinical decision making and to compare variation of IABP usage among institutions.

Low dose (renal dose) dopamine in the critically ill patient

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether low dose (renal dose) dopamine in the critically ill patient prevents acute renal failure. Altogether 141 papers were found using the reported search, of which three presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. We conclude that there is no evidence to support the use of low-dose dopamine to treat acute renal failure in critically ill patients.

Which patients would benefit from an intra-aortic balloon pump prior to cardiac surgery?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether there is a group of patients who would benefit from a prophylactic intra-aortic balloon pump prior to cardiac surgery. Altogether 110 papers were found using the reported search, of which seven presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. We conclude that there is evidence to support preoperative intra-aortic balloon pump insertion in patients with two of left ventricular ejection factor <30 or 40%, left main stem disease, unstable angina or redo-operation.

Does use of aprotinin in coronary artery bypass graft surgery affect graft patency

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether use of aprotinin in coronary artery bypass graft surgery adversely affects graft patency. Altogether 45 papers were identified using the below mentioned search, of which 10 presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. We conclude that aprotinin clearly reduces blood loss, requirement for blood transfusion, and the risk of reoperation for bleeding, but does increase the risk of saphenous vein graft occlusion.

What is the optimal dose of aspirin after discharge following coronary bypass surgery

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was, what is the optimal dose of aspirin post cardiac surgery that should be given to prevent graft occlusion and prolong survival. Altogether, 114 papers were found from Medline and 59 papers were found from the Cochrane Central Register of Controlled Trials using the reported search, of which seven presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. We conclude that best evidence suggests that 325 mg optimally improves vein graft survival and mortality, and does not cause an increase in complications compared to lower doses.

What is the optimal medical treatment for stable cardiac surgical patients who go into atrial fibrillation after their operation

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was which medical strategy is the optimal treatment for stable patients going into atrial fibrillation post cardiac surgery. Altogether 281 papers were found from medline and 83 from the Cochrane Central Register of Controlled Trials using the reported search, of which 12 presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. We conclude that there is very little evidence to support any one strategy over another.