Introduction

In war, anesthetic technique must take into account field conditions. In military anesthesia, medical gas (volatile anesthetics, nitrous oxide) can be difficult to obtain, and their choice is limited. The availability of anesthesia ventilators and vaporizers is uncertain. Conditions in a field hospital can be extreme in terms of temperature and space.

Two kinds of patients must be cared for. Major trauma patients are outnumbered by patients with superficial trauma, fractures, fatalities, peripheral gunshots, and limb injuries.1 In such cases, anesthesia must provide rapid recovery and efficient postoperative analgesia for early evacuation.

Total intravenous anesthesia (TIVA) answers the constraints of precarious material situations and has been used successfully in war conditions.2 TIVA with two short-lasting agents such as propofol and alfentanil presents further advantages: rapid awakening, efficacy for both ambulatory surgery3 and major procedures,4,5 induction and maintenance with the same agents, and reliability with a simple ventilatory device without nitrous oxides During the Persian Gulf War, four cases of battlefield casualties anesthetized with propofol and alfentanil mixed together in a single syringe were reported.7 Even though the mixture of anesthetic agents was abandoned years ago in Western countries, this technique might be useful under field conditions. The present study tried to improve this technique by using a simplified infusion scheme.

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The aim of the study was to compare in patients without multiple injuries the safety and efficacy of a TIVA technique using a simplified infusion scheme for propofol and alfentanil mixed together, both for induction and maintenance, with an inhalational anesthetic technique.

Methods

Study Design

After ethics committee approval and written informed consent, 32 American Society of Anesthesiologists physical status I patients free of medical illness and taking no medications, aged 17 to 48 years, and undergoing elective arthroscopic knee surgery (cruciate ligaments) with use of a tourniquet were included in the study. Patients were randomly allocated to one of two groups (TNA or inhalational technique).

In the TIVA group, a mixture of 2,500 tg of alfentanil (5 ml) and 450 mg of propofol (45 ml of 1% solution) was used. The concentration of each agent in the 50-ml syringe was 50 (mu)g ml^sup -1^ alfentanil and 9 mg ml^sup -1^ propofol.

Anesthetic Technique

Preinduction Period

All patients were premedicated orally with alprazolam (0.5 mg) and hydroxyzine (100 mg) 1 to 2 hours before surgery. An intravenous cannula (18 gauge) on the forearm was used for infusion of lactated Ringer's solution (5 ml kg^sup 1^ - h^sup -1^). Before induction, 3 minutes of ventilation with 100% oxygen via a face mask was achieved. Routine monitoring included electrocardiography, noninvasive blood pressure measurement, pulse oximetry, and capnography. Neuromuscular block was monitored by accelerometry (train-of four ratio, TOF Guard, Organon-Tecknica, Turnhout, The Netherlands).

Induction Period

In the TNA group, the mixture was infused by a Graseby 3400 pump (Graseby, Watford, Herts, United Kingdom) permitting infusion at a maximum rate of 1,200 ml h^sup -1^. The induction volume of the mixture was one-third the body weight in kilograms administered over 30 to 45 seconds (i.e., 3 mg kg^sup -1^ propofol and 16.6 (mu)g kg^sup -1^ alfentanil). After mask ventilation, at the second minute a dose of 0.5 mg kg^sup -1^ atracurium was injected, and maintenance infusion was started (Table I). Tracheal intubation was performed when adequate neuromuscular block had been achieved, about 5 minutes after the beginning of induction.