Preintubation Values Research Articles

Time-frequency spectral analysis of heart rate variability during induction of general anaesthesia

We have examined the spectral components of heart rate variability (HRV) during induction of anaesthesia with thiopentone, tracheal intubation and subsequent inhalation of isoflurane-nitrous oxide. Commonly used spectral analysis methods such as fast Fourier transformation or autoregressive modelling require stationary data and are not suitable for the rapidly changing HRV data in this period. An advanced spectral analysis method, time-frequency analysis, which can treat non-stationary data, was used in this study. Multiple spectra were generated to demonstrate the time-related spectral components of HRV. Mid-frequency power (MF, 0.08-0.15 Hz), high-frequency power (HF, 0.15-0.5 Hz) and MF/HF ratio at baseline, after induction (before intubation), immediately after intubation and during maintenance periods were calculated and compared. MF and HF powers decreased after induction and were reduced further in the maintenance period but MF/HF ratio remained unchanged after induction. Immediately after intubation MF and HF powers did not differ significantly from the immediate pre-intubation values, but MF/HF ratio did.

Intra‐ocular pressure changes in patients with glaucoma

We performed a randomised prospective study in 20 patients with glaucoma to examine the effects of tracheal intubation and laryngeal mask insertion on intra-ocular pressure, mean arterial blood pressure and heart rate. After induction of anaesthesia with propofol, intra-ocular pressure decreased significantly below baseline values in both the laryngeal mask and tracheal tube groups. After insertion of the laryngeal mask, intra-ocular pressure remained significantly below baseline values in all patients. In contrast, tracheal intubation was associated with a significant increase in intra-ocular pressure to above baseline values in three out of eight patients. Insertion of the laryngeal mask had minimal effects on mean arterial blood pressure and heart rate, whereas tracheal intubation significantly increased both factors relative to pre-intubation values.

EARLY TRACKEAL INTUBATION WITH THIOPENTONE TN ELECTIVE SURGERY

We have studied tracheal intubating conditions within 30 s of administration of thiopentone in 24 patients and compared this with our usual method of tracheal intubation, which involves 3 min of manual ventilation in 29 patients. All patients received papaveretum 10 mg 3 min before induction and alcuronium at induction of anaesthesia. Satisfactory intubating conditions were observed in 83% of patients in both groups. There were no difficult or failed intubations and no patient had laryngospasm. The duration of laryngoscopy in the control group was 14.1 (SD 8.6) s (range 7-50 s), compared with 12.4 (3.1) s (range 6-20 s), in the early intubation group (ns). In the control group there was a significant decrease in systolic pressure before tracheal intubation and a significant increase in heart rate after intubation, compared with baseline values. The average systolic pressure in the early intubation group increased only minimally: from a pre-intubation value of 143.3 (21.2) mm Hg to 145.5 (25.1) mm Hg after intubation. Our results demonstrate that early tracheal intubation under thiopentone supplemented with an opioid and a non-depolarizing neuromuscular block is feasible, associated with minimal changes in arterial pressure and not accompanied by an increased incidence of side effects.

EFFECTS OF NEBULIZED LIGNOCAINE ON THE INTRAOCULAR PRESSURE RESPONSES TO TRACHEAL INTUBATION

We have examined the effect of preoperative administration of nebulized lignocaine or saline on the intraocular pressure (IOP) response to tracheal intubation in 20 adults. In the saline group, tracheal intubation was associated with a significant increase in IOP above control and preintubation values (P less than 0.01); in the lignocaine group there was no change in IOP following intubation. After intubation, IOP was significantly less in the lignocaine group than in the saline group (P less than 0.05).

Continuous Monitoring of Left Ventricular Performance with the Computerized Nuclear Probe During Laryngoscopy and Intubation Before Coronary Artery Bypass Surgery

GILES, R. W.; BERGER, H. J.; BARASH, P. G.; TARABADKAR, S.; MARX, P. G.; HAMMOND, G. L.; GEHA, A. S.; LAKS, H.; ZARET, B. L. Author Information

Continuous monitoring of left ventricular performance with the computerized nuclear probe during laryngoscopy and intubation before coronary artery bypass surgery

Left ventricular performance was monitored serially in 25 patients during laryngoscopy and intubation in the anesthetic induction period before elective coronary artery bypass surgery using the labeled equilibrium blood pool and the computerized nuclear probe. Left ventricular ejection fraction was obtained preoperatively, after induction of anesthesia but before endotracheal intubation, immediately after intubation, and at 1 minute intervals thereafter for 10 minutes. In all patients, there was an immediate decrease (mean 16%) in left ventricular ejection fraction accompanying the reflex hypertension and tachycardia occurring during laryngoscopy and endotracheal intubation; it was significantly depressed for 3 minutes with the concomitant hemodynamic changes. Seven patients did not demonstrate a recovery of left ventricular ejection fraction to the preintubation value. In 10 healthy noncardiac patients undergoing orthopedic surgery, after an identical anesthetic induction sequence and intubation, there was a similar decrease in ejection fraction, but of shorter duration. In these patients the recovery of left ventricular performance preceded the recovery of blood pressure and heart rate. This study demonstrates that profound decreases in left ventricular performance accompany the reflex hypertension and tachycardia occurring during endotracheal intubation and that there is persisting depression of left ventricular function in some patients with coronary artery disease. These findings indicate the potential utility of the computerized nuclear probe for monitoring ventricular performance during this critical period.