Anaesthesiology Intensive Therapy, 2009,XLI,1; 34-37

The Therapeutic Intervention Scoring System (TISS-28) for assessment of cardiac surgical postoperative intensive care

*Katarzyna Gój1, Piotr Knapik2, Ewa Kucewicz-Czech2, Dariusz Luboń1


1Department of Anaesthesiology and Intensive Nursing Care, Silesian Medical University in Katowice


2Deparment of Cardiac Anaesthesiology and Postoperative Intensive Therapy, Silesian Medical University in Katowice

  • Table 1. Types of cardiac procedures and their risk
  • Table 2. TISS-28 scores in the postoperative period
  • Fig. 1. TISS-28 scores after cardiac procedures according to various operative risks
  • Fig. 2. Costs of therapy in patients of various operative risks
  • Fig. 3. Correlation between TISS-28 scores and treatment costs

Background. The TISS-28 scoring system, commonly used in Poland in general intensive care, relies mostly on nursing activities in individual patient care. It is not known, however, whether this system can also be useful in specialised intensive care. The aim of this study was to assess the usefulness of the TISS-28 scoring system in cardiac surgical intensive care.

Methods. Clinical records of three hundred and fifty-nine consecutive patients, treated in a cardiac surgical intensive care unit, were retrospectively analyzed. The records were analyzed overall, and in subgroups according to various ranges of operative risk according to the EuroSCORE (a scoring system commonly used in the preoperative assessment of cardiac surgical patients). The TISS-28 scores for each individual day of treatment were calculated. Additionally, individual real costs of treatment were calculated for each patient.

Results. One hundred and four patients (28.9%) were preoperatively allocated to the EuroSCORE low-risk group, 158 (44.0%) to the medium-risk group, and 97 (27.1%) to the high-risk group. The overall mean TISS-28 score was high (39.2±7.6). Patients in the high-risk group had the highest TISS-28 scores. Overall costs of treatment, calculated for individual patients, were closely correlated to the TISS-28 scores (r=0, 76, p<0, 0001).

Conclusions. The TISS-28 scoring system may be useful in prediction of treatment costs and in planning of nursing staff allocation in a specialized cardiac surgical intensive care.

Intensive therapy units in Poland are financed by covering the costs of each person-day of treatment based on the therapeutic intervention scoring system (TISS), reflecting the extent of nursing workload. In its original version, TISS included 76 parameters; for practical reasons, it was limited to 28 items - TISS-28 [1]. The TISS-28 scores determine the extent of the National Health Fund contracts. Such an approach is validated, as it is known that TISS-28 scores correlate well with ITU costs [2].

The maximum TISS-28 score is 78. One TISS-28 point corresponds to about 10 min. of direct care during the 8-hour nursing shift, i.e. during such a shift, the nurse is capable of providing services equal to 40-50 points. According to the authors of TISS-28, scores should be calculated one time a nursing or medical shift [3].

The utility of TISS-28 was confirmed in multi-profile ITUs [4, 5, 6]. However, it is not known what its usefulness is under specialist intensive care conditions, in which the extent of nursing workload and treatment-related costs might be extremely varied and depend largely on the profile of a given ward.

The treatment of patients in cardiac postoperative care units (CPCUs) requires marked workload of the nursing staff and generates extremely high costs [7], which should be reflected in TISS-28 scores. However, the literature lacks information regarding this issue; thus, it is not known whether TISS-28, commonly considered useful in general profile units (i.e. multi-profile ITUs) could be equally useful to assess the costs of treatment in specialist intensive care units (such as CPCUs).

In general, the risk of cardiac surgery is assessed according to the European System for Cardiac Operative Risk Evaluation (EuroSCORE). The system was devised based on analysis of about 20 thousand consecutive patients undergoing cardiac surgery in 128 hospitals of 8 European countries and is the major system used in Europe [8]. There are no literature data regarding the relation between the cardiac operative risk and TISS-28 score of patients during postoperative therapy.

The aim of the study was to assess the utility of TISS-28 in the cardiac postoperative care unit setting; in particular, the following questions were addressed to:

How are the individual groups of patients assessed according to TISS-28 in the postoperative period?

Is there any relation between the EuroSCORE evaluation and TISS-28 scores in the postoperative period?

Is there any relation between TISS-28 scores and costs of treatment in CPCU?

Our additional objective was to assess the patient-nurse ratio during one CPCU shift. Such assessments were feasible assuming that one TISS-28 point corresponded to a definite number of direct nursing care minutes.

METHODS

The retrospective analysis involved medical records of consecutive patients hospitalized in the Intensive Postoperative Therapy Unit (IPTU) of the Silesian Centre for Heart Diseases in Zabrze in the period of three months.  

The total data were analysed according to the degree of EuroSCORE operative risk and type of cardiac surgeries performed (coronary, valvular, coronary and vascular, aortal aneurysms, heart transplants and others). In each patient, the preoperative EuroSCORE was determined and the cardiac operative risk was categorized as low (0-2 pts), medium (3-5 pts) and high (6 and more pts).

Based on the retrospective analysis of medical records of all patients, the TISS-28 score was defined on the individual days of IPTU therapy. The TISS-28 evaluation was carried out according to generally accepted rules by recording the highest intensity of therapeutic activities in the individual categories within 24 h. Each TISS-28 therapeutic intervention was included in the score if confirmed in the records or its use was explicitly arising from them.

Once the TISS-28 score on each day of hospitalization was analysed, the precise length of IPTU stay was recorded, which was relevant for further calculations as part-days generated respectively lower costs of treatment.

The further analysis was to determine precise costs of therapy. The data were based on the information from hospital databases, Hospital Medical Information System,  the accounting department of the Silesian Centre for Heart Diseases and the IPTU cash register. Accurate costs of the whole IPTU stay as well as the cost of each day of therapy were calculated. The total costs of IPTU stay of a given patient were also divided into the following components: costs of drugs, blood preparations, diagnostic procedures, storage (dressing materials, disposable equipment, sanitary agents) as well as personal and indirect costs (salaries, media, equipment depreciation).

Costs of drugs, blood preparations and diagnostic procedures were accurately recorded in units thanks to the IPTU cash register. The storage, personal and indirect costs were calculated for each patient. For this reason, total storage, personal and indirect costs, incurred during the three analysed months, were divided by the total number of IPTU stay hours of all patients. The resultant cost of one hour of IPTU stay per one patient was multiplied by the length of IPTU stay, thereby the averaged storage and indirect cost of IPTU stay for each patient was obtained. After adding the costs of drugs, blood preparations and diagnostic procedures, the total, individual costs of IPTU stay per each patient were calculated.

The values of numeric parameters were compared between the groups using ANOVA. The values of qualitative parameters were compared using the ?2 test with appropriate corrections, if needed. Correlations between values of numeric parameters were determined based on the value and statistical significance of the Spearman’s rank correlation coefficient. Statistical calculations were carried out using the Statistica Pl software. Statistical significance was set at p<0.05.

RESULTS

The medical records of 359 patients revealed that 104 (28.9%) were preoperatively characterized by low, 158 (44%) by medium and 97 (27.1%) by high operative risk according to EuroSCORE.

The low operative risk group included patients scheduled for coronary artery bypass grafting (95.2%) and a low percentage of patients qualified for valvular procedures (4.8%). The higher difficulty procedures (complex -  involving valve replacement or valve plastic surgery combined with coronary artery bypass grafting as well as aortal aneurysm procedures and heart transplants) were performed in patients with medium or high operative risk (Table 1).

The TISS-28 postoperative evaluation was on average 39.2±7.6 pts. The highest score was noted on day “0” (the surgery day). On day 1, the recorded score was markedly lower. On the successive days, a high proportion of patients were discharged from IPTU; those remaining in the unit were often the patients with complications, thus the mean TISS-28 score was higher (Table 2).

The high operative risk patients had significantly higher TISS-28 scores, both on the individual postoperative days and at all recorded measurements (Fig. 1). The mean total IPTU costs depended on the degree of operative risk and were found to reach the highest values in the high operative risk group (Fig.2).

Despite the differences in TISS-28 scores, operative risks of patients and surgical procedures performed, the total TISS-28 score correlated strictly with total costs of therapy (r=0.76, p<0.0001) (Fig. 3).

DISCUSSION

Intensive therapy and critical care require highly qualified medical staff and advanced management methods. Those forms of therapy generate the highest costs in the process of stationary treatment exceeding the costs of therapy in other hospital wards, which is associated with more severe conditions of patients, mostly life-threatening and requiring intensive diagnostic and therapeutic procedures, increased pharmacotherapy, continuous nursing care and specialist monitoring devices [9].  

The multi-profile intensive therapy units must be run only by specialists in anaesthesiology and intensive therapy. However, the number of intensive therapy units in Poland is too low to provide care for all patients requiring it. Some of them, although fulfilling the criteria of ITU admission, are treated in wards of various profiles - surgical, medical, neurological, cardiac, etc, by other specialists.
There is much controversy about the literature terms “general or specialist intensive therapy” [10, 11]. In our country, these terms function separately – we have “intensive therapy” and “intensive care” – the latter administered in various ways in the units under a variety of names – postoperative, high dependency or critical care units.

The authors of TISS-28 recommend calculating TISS-28 scores during one 8-hour nursing shift [3], whereas strict surveillance shifts last 12 h and nursing activities are equal to TISS-28 66.7 pts, on average. Considering that in patients after cardiac surgery the TISS-28 score is 39.2±7.6 pts, it may be assumed that the patient-nurse ratio ought to be about 1.7:1. To provide the minimum reserve, the ratio value should be reduced to 1.5:1

Thus, the recommended number of nurses in IPTU depends on the number of patients, e.g. during the 12-h shift, 4 patients should be managed by 3 nurses, 6 by 4 and 9 by 6 nurses. These calculations, however, are only estimates.  

CONCLUSIONS

1. In patients after cardiac surgery, the TISS-28 score is high and depends on the preoperative risk according to EuroSCORE and types of procedures.

2. TISS-28 may be useful to prognosticate the costs of therapy and number of nurses required under specialist postoperative care conditions in cardiac surgery.

3. In cardiac postoperative intensive therapy units, at least two nurses should be available for each three patients.

..............................................................................................................................................................

REFERENCES

1.Keene AR, Cullen DJ: Therapeutic Intervention Scoring System: update 1983. Crit Care Med 1983; 11: 1-3.

2.Dickie H, Vedio A, Dundas R, Treacher DF, Leach RM: Relationship between TISS and ICU cost. Intensive Care Med 1998; 24: 1009-1017.

3.Miranda DR, de Rijk A, Schaufeli W: Simplified Therapeutic Intervention Scoring System: the TISS-28 items – results from astudy. Crit Care Med 1996; 24: 64-73.

4.Graf J, Graf C, Koch KC, Hanrath P, Janssens U: Cost analysis and outcome prediction with the Therapeutic Intervention Scoring System (TISS and TISS-28). Med Klin 2003; 98: 123-132.

5.Kaufmann I, Briegel J: Therapeutic Intervention Scoring System (TISS) – afor calculating costs in the intensive care unit (ICU) and intermediate care unit (IMCU). Critical Care 2000; 4 (Suppl. 1): 243.

6.Parviainen I, Herranen A, Holm A, Uusaro A, Ruokonen E: Results and costs of intensive care in auniversity hospital from 1996-2000. Acta Anaesthesiol Scand 2004; 48: 55-60.

7.Azoulay A, Pilote L, Filion KB, Eisenberg MJ: Costs of treatment of acute myocardial infarction in Canadian and US hospitals. Cardiovasc Rev Rep 2003; 24: 555-560.

8.Nashef SA, Roques F, Michel P, Gauducheau E, Lemeshow S, Salamon R: European system for cardiac operative risk evaluation (EuroSCORE). Eur J Cardiothorac Surg 1999; 16: 9-13.

9.Brilli RJ, Spevetz A, M, Branson RD: Leczenie na oddziale intensywnej terapii: okreslenie zadan klinicznych inajlepszego modelu praktyki. Med Inten Rat 2006; 2: 117-132.

10.Intensive Care National Audit & Reserch Centre: General critical information. http://www.icnarc.org/patients/general. http://www.answers.com/topic/intensive-care-medicine

..............................................................................................................................................................

Address:

*Katarzyna Gój
Zakład Anestezjologii i Intensywnej Opieki Pielęgniarskiej
ul. Ziołowa 45/47, 40-635 Katowice
e-mail: kgoj@poczta.fm

Received: 05.08.2008.
Accepted: 09.10.2009.