Asian Cardiovasc Thorac Ann 2005;13:325-329
© 2005 Asia Publishing EXchange Ltd
Intensive Care Unit Readmission after Elective Coronary Artery Bypass Grafting
Joseph Alex, MRCS,
Rajesh Shah, FRCS,
Steven C Griffin, FRCS,
Alexander RJ Cale, FRCS,
Michael E Cowen, FRCS,
Levent Guvendik, FETCS
Department of Cardiothoracic Surgery, Castle Hill Hospital, Hull, United Kingdom
For reprint information contact: Joseph Alex, MRCS Tel: 44 150 736 3541 Fax: 44 150 736 3541 Email: mrjosephalex{at}yahoo.co.uk, The Cottage, Main Road, Covenham St. Bartholomew, Louth LN11 0PF, United Kingdom.
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ABSTRACT
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Prospective data of 3,120 consecutive patients who had elective coronary artery bypass were analyzed to identify patient profile, cost, outcome and predictors of those readmitted to the intensive care unit. Group A (n = 3,002) had a single intensive care unit admission and group B (n = 118) were readmitted within 30 days after surgery. Parsonnet score, EuroSCORE, age, body mass index, chronic obstructive airway disease, peripheral vascular disease, renal dysfunction, unstable angina, congestive cardiac failure, and poor left ventricular function were higher in group B. Bypass and crossclamp times were longer, and the prevalence of inotropic and balloon pump support, arrhythmias, myocardial infarction, re-exploration, blood loss and transfusion, cerebrovascular accident, wound infection, sternal dehiscence, and multisystem failure were higher in group B. Despite a 4-fold increase in cost of care, the mortality rate (32.4%) of patients readmitted to intensive care was 23-times higher than routine patients (1.4%). Crossclamp time > 80 min, Parsonnet score > 10, EuroSCORE > 9, sternal dehiscence, ventricular arrhythmias, and renal failure predicted readmission.
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INTRODUCTION
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Not infrequently, owing to continuing organ dysfunction or new complications, there arises a need to readmit patients to the intensive care unit (ICU) following coronary artery bypass grafting. Despite the fact that readmitted patients have a much higher morbidity and mortality, to date, very few studies have identified the predictors or analyzed the patient profile, cost, and outcome.
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PATIENTS AND METHODS
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Prospectively entered data from the patient analysis and tracking system database of 3,120 consecutive first-time coronary artery bypass patients from 1999 to 2003 were analyzed. Emergencies were not included in the study. Subsequent to entry of the data, they were independently checked, compared to patient notes, and validated for completeness and accuracy. There were 3,002 patients (group A) who had a single routine ICU admission, and 118 (group B) who were readmitted to the ICU within 30 days of surgery, indicating a readmission rate of 3.8%.
The anesthesia, myocardial protection technique, and mode of cardiopulmonary bypass were essentially similar in both groups. Following cardiac surgery, all patients were transferred directly to the ICU and managed by the intensive care team comprising surgical and anesthetic intensivists and registered nurses trained in post-cardiac surgery ICU care. Patients in ICU received 1:1 nursing care with continuous monitoring of the electrocardiogram, blood pressure, central venous pressure, oxygen saturation (SaO2), temperature, hourly fluid balance, 1–2 hourly blood gases, 4 hourly neurologic and Glasgow coma scale assessment, and daily hematological and biochemical profile. The decision to transfer a patient from ICU to the high dependency unit (HDU) was based on these parameters: mean arterial pressure > 70 mm Hg without inotropic support, blood pH 7.3–7.45, arterial blood oxygen > 75 mm Hg on inspired oxygen < 35%, arterial blood CO2 < 40 mm Hg, SaO2 > 95%, Glasgow coma scale > 13. In the HDU with a 1:4 nurse:patient ratio, continuous monitoring of the electrocardiogram, central venous pressure, SaO2, hourly fluid balance, and 4-hourly blood pressure, pulse, and temperature measurement were undertaken. From the HDU, patients were transferred to the ward with a 1:6 or 1:8 nurse:patient ratio, continuous telemetry monitoring, 4-hourly pulse, blood pressure, temperature, and SaO2 measurement, and daily hematological and biochemical profile. All patients received twice-daily physiotherapy, with additional sessions when indicated. Ward rounds twice a day by the surgical team included clinical examination, analysis of laboratory investigations and appropriate changes in management. The criteria for readmission to the ICU included: respiratory failure due to any cause, needing ventilation; cardiac arrest or cardiovascular instability requiring inotropic support; recurrent ventricular arrhythmias; acute renal failure requiring hemofiltration or dialysis; severe sepsis requiring inotropic support; and re-exploration or other surgical procedures requiring general anesthesia.
The chi-squared test and Fisher’s test were used for categorical data, while the Student t test was used for numerical data. Statistical significance was set at p < 0.05. Univariate, followed by multivariate, logistic regression analysis was undertaken to identify predictors of readmission to the ICU. Further subgroup analyses of reasons for readmission, length of stay, and mortality were undertaken, based on left ventricular (LV) function. SPSS version 11.0 for Windows software (SPSS Inc., Chicago, IL, USA) was used for statistical analysis.
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RESULTS
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Readmitted patients in group B had a higher preoperative risk profile in terms of Parsonnet score, EuroSCORE, age, body mass index, chronic obstructive airway disease, peripheral vascular disease, renal dysfunction (serum urea > 30 mg·dL–1, serum creatinine > 1.6 mg·dL–1), recent unstable angina, recent congestive heart failure, and poor LV function (Table 1
). The sex ratio and the prevalence of smoking, diabetes, hypertension, cerebrovascular accident, and myocardial infarction, and the coronary disease severity were comparable. Bypass and crossclamp durations were higher in group B.
Details of postoperative inotropic and intra-aortic balloon pump support, arrhythmias, myocardial infarction, re-exploration, blood loss, blood transfusion, cerebrovascular accident, renal dysfunction, gastrointestinal complications, major wound infection, sternal dehiscence, and multisystem failure are shown in Table 2. The durations of ICU, HDU, and ward stay were significantly higher in group B. The early postoperative mortality was 32.4% in group B and 1.4% in group A. The daily cost of care per patient in the ICU, HDU, and the general ward was approximately: 1,200, 700, and 350 GBP, respectively. Based on the mean lengths of stay, the total cost per patient for ICU, HDU, and ward care was: 1,500, 1,050, and 1,785 GBP, respectively, in group A; and 9,000, 6,090, and 3,290 GBP in group B. The total cost of care per readmitted patient in group B was 18,380 GBP compared to 4,335 GBP in group A.
A subgroup analysis of patients readmitted to the ICU (Table 3) revealed that in patients with poor LV function, ventricular arrhythmia (43.8%) was the main reason for readmission, whereas respiratory failure (42.2%) was the main reason for readmission in patients with good LV function ( p = 0.01). Within the readmission group, there were no significant differences in the length of stay (27.6 ± 28.3 vs. 24.1 ± 23.2 days) or mortality (37.5% vs. 31.6%) between patients with poor LV function compared to those with good LV function.
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Table 3. Outcome in Patients with Good (n = 98) and Poor (n = 20) Left Ventricular (LV) Function Readmitted to the Intensive Care Unit
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Univariate predictors of readmission were: chronic obstructive airway disease, crossclamp time > 80 min, Parsonnet score > 10, EuroSCORE > 9, re-operation for bleeding, sternal dehiscence, ventricular arrhythmias, low cardiac output, gastrointestinal complications, postoperative cerebrovascular accident, and postoperative renal failure (serum urea > 30 mg·dL–1, serum creatinine > 1.6 mg·dL–1, urine output < 500 mL in 24 h, K+ > 6 mEq·L–1, pH < 7.25). However, on multivariate logistic regression analysis (Table 4) only crossclamp time > 80 min, Parsonnet score > 10, EuroSCORE > 9, sternal dehiscence, ventricular arrhythmias, and postoperative renal failure predicted readmission to the ICU.
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DISCUSSION
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The operating capacity of any cardiac unit is dependent on theater time and ICU bed availability. The immediate postoperative period of ventilation facilitates myocardial recovery by reducing the work of breathing, maintaining an optimum level of oxygenation and re-inflation of the lungs. Early extubation after 6–8 hours of ventilation improves diastolic compliance, overall cardiac function, and due to a better ability to cough, reduces the incidence of atelectasis and lobar collapse. Advances in technology, improvements in anesthetic methods, surgical technique, professional skills, and the application of evidence-based medicine have improved postoperative care to facilitate early extubation and discharge from the ICU. Despite the increase in demand for ICU beds, resources and staffing levels have remained limited in most cardiothoracic units in the UK. The need to maintain a high standard of care under these constraints has forced most units to adopt a policy of clinical-criteria based and protocol-driven decision making regarding extubation and transfer out of the ICU and HDU. Although this practice of basing decisions on patients achieving certain target figures works for the majority of cases, it does not give due importance to the patient’s risk-profile, the possibility of progressive organ dysfunction, or identified predictors of readmission.1–4 From our analysis, it is clear that patients who were readmitted to the ICU had a higher preoperative risk-profile and longer bypass and crossclamp times. The complication rates and postoperative morbidity were also significantly higher in this group. Our readmission rate of 3.8% was comparable to previous studies in which it ranged from 3.5–12%.4–11 Previously identified predictors of ICU readmission have included obesity, female sex, history of congestive heart failure, preoperative renal failure, poor LV function, high Parsonnet score, non-elective surgery, re-exploration, increased postoperative weight gain, longer initial intubation time, high inspired oxygen requirement, and high respiratory rate on discharge from the ICU.1–14 New predictors identified in our analysis were long crossclamp time, high EuroSCORE, sternal dehiscence, ventricular arrhythmias, and postoperative renal failure.
The importance of analyzing the ICU readmission rate and predictors for readmission lies in the fact that despite the higher intensity and cost of care, the outcome in these patients in terms of morbidity and mortality is significantly worse than for "routine" patients. Apart from the operation itself, ICU stay accounts for the highest proportion of the cost of care following any major surgery.4–16 The duration of ICU stay was 6 times longer, HDU stay was 5.5 times longer, ward stay was 2 times longer, and the mortality rate was 23 times higher in patients readmitted to the ICU. The mean cost of care was 4 times higher in this group. Irrespective of the actual reason for readmission, the main issue necessitating readmission to ICU is progressive or new organ dysfunction. Prospective analyses have shown significant reductions in ICU readmission after the opening of high-dependency units.17–19 Although a longer ICU stay for the sole purpose of closely monitoring these high-risk patients is neither feasible nor economically viable, applying a risk stratification score based on the predictors noted in our study and in previous studies (Table 4
and 5) to identify high-risk patients who would benefit from a longer duration of close monitoring in the HDU could be a cost-effective pre-emptive strategy to reduce the ICU readmission rate, morbidity, mortality, and the overall cost of treatment.
Presented at Chest 2004: 70th Annual Meeting of the American College of Chest Physicians. October 23–28, 2004, Seattle, Washington, USA.
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REFERENCES
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- Sirio CA, Martich GD. Who goes to the ICU postoperatively? Chest 1999;115(5 Suppl):125S–9S.[Abstract/Free Full Text]
- Loubani M, Mediratta N, Hickey MS, Galinanes M. Early discharge following coronary bypass surgery: is it safe? Eur J Cardiothorac Surg 2000;18:22–6.[Abstract/Free Full Text]
- Legare JF, Hirsch GM, Buth KJ, MacDougall C, Sullivan JA. Preoperative prediction of prolonged mechanical ventilation following coronary artery bypass grafting. Eur J Cardiothoracic Surg 2001;20:930–6.[Abstract/Free Full Text]
- Higgins TL, Estafanous FG, Loop FD, Beck GJ, Lee JC, Starr NJ, et al. ICU admission score for predicting morbidity and mortality risk after coronary artery bypass grafting. Ann Thorac Surg 1997;64:1050–8.[Abstract/Free Full Text]
- Chung DA, Sharples LD, Nashef SA. A case-control analysis of readmissions to the cardiac surgical intensive care unit. Eur J Cardiothorac Surg 2002;22:282–6.[Abstract/Free Full Text]
- Kogan A, Cohen J, Raanani E, Sahar G, Orlov B, Singer P, et al. Readmission to the intensive care unit after "fast-track" cardiac surgery: risk factors and outcomes. Ann Thorac Surg 2003;76:503–7.[Abstract/Free Full Text]
- Bardell T, Legare JF, Buth KJ, Hirsch GM, Ali IS. ICU readmission after cardiac surgery. Eur J Cardiothorac Surg 2003;23:354–9.[Abstract/Free Full Text]
- Rosenberg AL, Hofer TP, Hayward RA, Strachan C, Watts CM. Who bounces back? Physiologic and other predictors of intensive care unit readmission. Crit Care Med 2001;29:511–8.[Medline]
- Chen LM, Martin CM, Keenan SP, Sibbald WJ. Patients readmitted to the intensive care unit during the same hospitalization: clinical features and outcomes. Crit Care Med 1998;26:1834–41.[Medline]
- Cohn WE, Sellke FW, Sirois C, Lisbon A, Johnson RG. Surgical ICU recidivism after cardiac operations. Chest 1999;116:688–92.[Abstract/Free Full Text]
- Cooper GS, Sirio CA, Rotondi AJ, Shepardson LB, Rosenthal GE. Are readmissions to intensive care unit a useful measure of hospital performance? Med Care 1999;37:399–408.[Medline]
- Durbin CG Jr, Kopel RF. A case-control study of patients readmitted to the intensive care unit. Crit Care Med 1993;21:1547–53.[Medline]
- Rosenberg AL, Watts C. Patients readmitted to ICUs: a systematic review of risk factors and outcomes. Chest 2000;118:492–502.[Abstract/Free Full Text]
- Metnitz PG, Fieux F, Jordan B, Lang T, Moreno R, Le Gall JR. Critically ill patients readmitted to intensive care units lessons to learn? Intensive Care Med 2003;29:241–8.[Medline]
- Noseworthy TW, Jacobs P. Economic and ethical consideration in the intensive care unit. Healthc Manage Forum 1990;3:3–18.
- Holmes L, Loughead K, Treasure T, Gallivan S. Which patients will not benefit from further intensive care after cardiac surgery? Lancet 1994;344:1200–2.[Medline]
- Fox AJ, Owen-Smith O, Spiers P. The immediate impact of opening an adult high dependency unit on intensive care unit occupancy. Anaesthesia 1999;54:280–3.[Medline]
- Thompson H, Spiers P. Occupancy of a teaching hospital adult intensive care unit by high dependency patients. Anaesthesia 1998;53:589–92.[Medline]
- Leeson-Payne CG, Aitkenhead AR. A prospective study to assess the demand for a high dependency unit. Anaesthesia 1995;50:383–7.[Medline]
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ABSTRACT
INTRODUCTION
