Advances in monitoring in intensive care: continuous mixed venous oxygen saturation and right ventricular ejection fraction.

Direct cardiorespiratory measurements and the use of optimum values to guide therapy have been associated with improved survival in a number of conditions causing critical illness. Increasingly sophisticated monitoring that provides more accurate and reproducible assessment of the cardiorespiratory system at the bedside is pivotal to this better outcome. The inclusion of fibreoptic filaments and fast response thermistors in pulmonary artery catheters makes possible the continuous monitoring of mixed venous oxygen saturation and the measurement of right ventricular ejection fraction. Although the place of measurement and manipulation of these variables in critically ill patients has yet to be fully defined, clinical studies are promising. We discuss some practical aspects of the use of these measurements and some potential clinical applications. Additionally, some of the studies in which the use of these measurements is increasing our knowledge of the pathophysiology of critical illness and contributing to improved management of critically ill patients, are highlighted.

Drug-induced hyperthermia.

Drugs with antidopaminergic properties and those capable of stimulating serotonin release can be responsible for hyperthermia syndromes such as neuroleptic malignant syndrome and serotonin syndrome. Dopamine and serotonin are important neurotransmitters in temperature regulation and it is likely that these reactions result from drug-induced changes in neurotransmitter levels. We describe three cases of drug-induced hyperthermia, discuss their aetiology and management, with both general measures and therapies designed to redress neurotransmitter imbalance.

Moral principles in withdrawing basic life support from patients in the persistent vegetative state.

Patients in a state of persistent vegetation or 'cognitive death' are an emotional drain on their family, and a financial drain on a society with limited resources. In this article, society's responsibility towards these patients and the moral and ethical issues involved in the withdrawal of fluid and nutrition are discussed.

Moral principles in withdrawing advanced life support.

Decisions regarding withdrawal of life support are more frequently required as our technological capabilities increase. Doctors have to recognize that in certain cases maximal use of these capabilities may be incompatible with the patient's best interests. An ethical framework may help guide doctors through these dilemmas.

Blood pressure measurement during transport. A comparison of direct and oscillotonometric readings in critically ill patients.

This study assessed the accuracy of oscillotonometric blood pressure measurement in critically ill patients during transfer. Direct intra-arterial pressure measurements were taken in 44 transported patients as a 'gold standard' and compared with readings from four portable automatic oscillotonometers--the Dinamap 8100, Lifestat 100, Propaq 102 and Takeda UA711. All under-read systolic pressure (by 13%, 21%, 19% and 13% respectively) and over-read diastolic pressure (by 15%, 5%, 27% and 15% respectively) in comparison to direct pressure measurement. The limits of agreement for 95% of comparisons were broad. The systematic difference between direct and oscillotonometric measurements and the variability between and within patients show that direct oscillotonometric measurements are not interchangeable in these patients. Portable automatic oscillotonometers should not be substituted for direct monitoring in such circumstances.

Development of a probe for the in vivo measurement of airway humidity during anaesthesia.

Airway drying can arise during long-term respiration of anaesthetic dry gases and this may have implications for the function of the airway wall. Monitoring airway humidity can identify drying trends, although previous attempts have been limited for technical reasons. The design and development of a probe to measure mid-tracheal air humidity is described. The device comprises a commercially available capacitive humidity sensor and a thermocouple. The assembled probe is catheter-like with a diameter of 9.5 mm and a length of 312 mm. Water vapour transfer response times of 1.4s (absorption) and 3.6s (desorption) were evaluated for the probe. A preliminary trial to record airway humidity in ambient air and involving six patients was performed during anaesthesia.

How to perform tracheal intubation.

Tracheal intubation is a skill that should be considered supplementary to other aspects of airway management which are of vital importance in resuscitation. Doctors involved in resuscitation should develop and retain such skills, and be aware of potential dangers.

A comparison of measurements of blood pressure, heart-rate and oxygenation during inter-hospital transport of the critically ill.

Critically ill patients transferred between hospitals are often inadequately monitored in transit, with outcome adversely affected. In 22 such patients, we compared direct and palpated measurements of systolic pressure, oscilloscopic and aneroid manometric measurements of mean pressure, ECG and palpated measurements of heart-rate and clinical and oximetric assessments of oxygenation. On average palpated readings of systolic pressure under-read direct readings by 29% and palpated readings of heart-rate under-read ECG readings by 2%. The mean difference between oscilloscopic and manometric readings of mean pressure was zero. Oxygen saturation readings did not reach a level which allowed valid comparison. If direct measurement of heart-rate and blood pressure by battery-powered monitors is not feasible, palpation of heart-rate and manometric measurement of mean arterial pressure are acceptable alternatives during secondary transport of the critically ill.

Paracetamol absorption from Paramax, Panadol and Solpadeine.

Plasma paracetamol concentrations were measured after oral administration of three pharmaceutical preparations to four healthy volunteers. The formulations were Paramax (paracetamol with metoclopramide), Solpadeine (paracetamol with codeine and caffeine) and Panadol (paracetamol alone). After Solpadeine, concentrations at 15 min were significantly higher than after Panadol. Absorption of paracetamol from Paramax tablets did not differ significantly from Solpadeine or Panadol.