An analysis of the logistics of supplying and processing sterilized items in hospitals

Abstract

This paper presents an analysis of the logistics of supplying and processing sterile medical/surgical supplies and materials for hospitals. The analysis slightly modifies classical inventory theory to take into consideration the special needs and requirements of hospitals, particularly the need to allow for the possibility of being ‘cut off from supplies’ and to take into consideration the effects of single-use vs multiple-use items [1,2,4,6]. The analysis breaks out total sterile stock requirements into two components—processing stock and replacement stock. The processing stock component is the multiple-use and single-use, non-prepackaged kern stock required to ‘support’ the processing cycle. For the case of continuous processing, continuous constant demand, the processing component is equal to the product of the daily demand times the processing cycle in days. For the case of discrete, evenly spaced demand, it is described by a range of values, the lower limit of which is a linear function of demand and processing time and the upper limit of which is a disjointed linear function of demand and processing time. The replacement stock component is the stock that is required to replace items thȧt wear out or are lost, damaged, pilfered, and the like. The replacement stock component is broken out into two components: a working stock—the stock required to replace items that wear out, etc., during the normal time between arrival of supplies; and a safety stock—the stock required for replacements during the time when a hospital could be cut off from supplies. The analysis shows that, for fixed replenishment intervals, the replacement stock component is equal to the daily demand multiplied by the sum of the replenishment and cut-off periods, and the product is divided by the number of times the item in question can be used. At economical order quantities, the working stock component is proportional to the square root of the annual demand times the cost to order items divided by the number of uses possible for the item in question times the annual cost to inventory items. An example demonstrates the combined effects of processing and replacement stock on total sterile stock requirements for a hospital. The example shows that single-use, non-prepackaged items require the greatest level of supply, single-use prepackaged items the next level of supply, multiple-use slowly processed items an intermediate level of supply, and multiple-use quickly processed items the lowest level of supply.