Attenuation of the pressor response to tracheal intubation by magnesium sulphate with and without alfentanil in hypertensive proteinuric patients undergoing caesarean section.

The pressor response to tracheal intubation is known to be exaggerated in patients with gestational proteinuric hypertension (GPH). We have studied the effect of pretreatment with magnesium sulphate 40 mg kg-1 or 30 mg kg-1 with alfentanil 7.5 micrograms kg-1 on this pressor response in 38 patients with moderate to severe GPH. The magnesium-alfentanil combination produced better control of arterial pressure and heart rate than magnesium alone, although both techniques provided good cardiovascular control. There was no significant difference in fetal outcome between groups. Both pretreatment methods produced satisfactory control of catecholamine release.

Attenuation of the pressor response to tracheal intubation in hypertensive proteinuric pregnant patients by lignocaine, alfentanil and magnesium sulphate.

The pressor response to intubation is known to be exaggerated in patients with gestational proteinuric hypertension (GPH). The effect of pretreatment with lignocaine 1.5 mg kg-1, magnesium sulphate 40 mg kg-1 or alfentanil 10 micrograms kg-1 on this pressor response was studied in 69 patients with moderate to severe GPH. Systolic arterial pressure exceeded baseline values for the first 5 min after tracheal intubation in the lignocaine group, with a peak increase of 31.6 (SEM 3.6) mm Hg at 2 min after intubation, but no mean increase in pressure occurred in the two other groups. Following intubation, six of 24 mothers in the alfentanil group, six of 21 in the lignocaine group and one of 24 in the magnesium group (P less than 0.05) exhibited a systolic arterial pressure (SAP) greater than 180 mm Hg sustained for 2 min or more. Alfentanil caused the least change in heart rate, but resulted in significant fetal depression.

Self-tuning, microprocessor-based closed-loop control of atracurium-induced neuromuscular blockade.

A self-tuning, closed-loop computerized system was used to maintain atracurium-induced neuromuscular blockade in patients undergoing routine lower abdominal gynaecological surgery. The controller is based on a unique algorithm which utilizes a bi-exponential model wherein two of the variables are estimated on-line. This enables the system to optimize the sizes of subsequent bolus doses according to patient sensitivity. In this study an initial bolus of 0.3 mg kg-1 was given in a trade-off aimed at achieving earlier intubating conditions rather than taking control of relaxation ab initio and obtaining the pre-programmed setpoint of 15% single twitch response (STR) without overshoot. This was successful in all of the 11 patients studied, the mean time from injecting the bolus to intubation being 2.47 (SD 0.95) min and the drug maintenance requirement being 0.34 (0.07) mg kg-1 h-1. This provided a mean value of 10.26% STR with minimal oscillation about the setpoint (average standard deviation = 4.31 (2.53)) for up to 147 min.

On-line control of atracurium induced muscle relaxation.

We described recently a microcomputer system capable of controlling muscle relaxation during surgical procedures; the system was tested and evaluated in 42 clinical trials involving the use of the muscle relaxant, d-tubocurarine. The advent of new non-depolarizing neuromuscular blocking drugs with significant clinical advantages makes it essential that any automatic control system for muscle relaxation can also be used with such drugs, and benefit from their improved properties. This paper describes a series of 22 clinical trials in which our controller was used successfully to control muscle relaxation using atracurium. We also investigated an alternative control strategy, taking advantage of the rapid elimination of atracurium from the body.