Identification of subgroups with long length of stay in surgical intensive care units among patients undergoing surgical cardiac valve replacement based on preoperative, peroperative, and postoperative variables

Background

The identification of subgroups of patients with long length of stay in surgical intensive care units (SICUs) may avoid inadequate management, as well as an increase in morbidity and costs. Fast track flowcharts are available in the literature, but they do not refer to surgical cardiac valve replacement (SCVR).

Objectives

To identify first postoperative day (FPOD) markers for length of stay in the SICU using preoperative, perioperative, and FPOD variables.

Case series and methods

A classical cohort with data consecutively collected in a private SICU from June 2000 to February 2003 (group B, 121 patients), and in a public SICU from January 2001 to February 2003 (group A, 326 patients). All 46 variables were previously defined according to the major prognostic indices in the literature and were correlated with the length of stay in the SICU as follows: group A, <3 days; group B, 4–7 days; and group C, >7 days. A classification and regression tree (CART) (using the Gini index with a FACT stop rule of 0.10 and equal priori) was created and followed by pruning based on misclassification and crossvalidation.

Results

Based on the CART, 16 relevant variables were selected. The model had an accuracy of 69% for group A and 80% for groups B and C. Analyzing patients with length of stay in the SICU up to 7 days, the accuracy increased to 87%.

Conclusions

The CART may provide interesting solutions regarding patient allocation and also quality assessment. Variables (ranking): age (100), FPOD multiple organ dysfunction syndrome (MODS) score (55), FPOD blood drainage (95), patient's sex (44), Rio score (89), FPOD Sepsis-related Organ Failure Assessment score (43), FPOD creatinine (86), alveoloarterial O₂ tension gradient > 250 (42), left atrial length on ECHO (84), perioperative fluid balance (41), extracorporeal circulation duration (83), body mass index < 20 (39), perioperative arterial bicarbonate (81), reoperation (37), FPOD epinephrine > 0.1 or norepinephrine > 0.1 (68), and age 0–64, 65–74 (35).