Propofol, discovered in 1977, is an intravenous anaesthetic agent widely used in the operating theatres of all hospitals. It is a short-acting agent (from a few minutes up to one hour) which also has amnestic properties. It induces hypnosis reliably and quickly and has additive or synergistic effects with many other agents used in anaesthesia (barbiturates, benzodiazepines, opioids and ketamine). Propofol is associated with a smooth and rapid recovery, which distinguishes it from most traditional anaesthetics. Like other intravenous agents, propofol is both a cardiovascular and a respiratory depressant. However, the risk of these effects can be reduced by means of appropriate adjustments to the dosage or patient management. In addition, it induces a moderate relaxation of the vocal cords, facilitating intubation.

Propofol is a drug which is widely used in total intravenous anaesthesia (TIVA) by means of pharmacokinetic models of target-controlled infusion (TCI). This can be done using smart infusion pumps such as arcomed’s Chroma pumps.

It is also used in sedation procedures and in the ICU, especially in patients undergoing mechanical ventilation.

The Cortínez-Sepúlveda Model for Propofol

This pharmacokinetic model for the intravenous infusion of propofol in TCI mode has been developed by Drs. Luis I. Cortínez and Pablo O. Sepúlveda. Dr. Cortínez is a surgeon and specialist in anaesthesiology, an associate professor at the Pontificia Universidad Católica de Chile and a member of TIVA América, while Dr. Sepúlveda is an anaesthesiologist, ex-chairman and founding member of TIVA América and one of the world’s leading authorities on intravenous anaesthesia. Both have published numerous research papers in this field.

The Cortínez-Sepúlveda model arises from the need to develop a specific model for obese patients, since the traditional models (Schnider, Minto, Marsh, etc.) used in total intravenous anaesthesia (TIVA) present significant shortcomings in this respect, due to the particular characteristics of this type of patient. These models tend to present significant divergences between the predicted and observed drug concentrations, meaning anaesthetists have to use complex calculations or adjustment equations. Even so, patients with obesity (very high BMI or high body weight) present alterations in the pharmacokinetics of many compounds, and propofol is no exception.

In light of this situation, Drs. Cortínez and Sepúlveda decided to develop a new pharmacokinetic model for propofol which would simplify the work of the anaesthetist in patients with a high BMI and body weight of up to 250 kg, which presents its own challenges when it comes to performing surgery.

The basic parameters of this model are simple: k41 = 0.21 (corresponding to Ke0) and vc = 4.48* v2. Both of these are pharmacokinetic factors which determine the time and concentration of the drug in the tissues of the patient in way which is much more suited to the reality observed than other models already mentioned.

The Cortínez-Sepúlveda model for propofol is exclusively incorporated into Arcomed’s Chroma pumps as one of the models selectable by the anaesthetist in procedures using the TIVA-TCI mode. You just need to enter the physical parameters of the patient and the pump carries out all the dosage calculations necessary to maintain an appropriate drug concentration throughout the surgical procedure.

Here at Arcomed we collaborate closely and regularly with the most esteemed medical professionals in order to offer our clients the latest advances in infusion technology. The Cortínez-Sepúlveda model is a good example of this collaboration.