Intra-ocular pressure changes during induction of anaesthesia and tracheal intubation. A comparison of thiopentone and propofol followed by vecuronium.

Intra-ocular pressure was measured during induction of anaesthesia with propofol (n = 40) or thiopentone (n = 40) followed by vecuronium to facilitate tracheal intubation which was carried out 3 minutes after the administration of relaxant. The average induction doses were 2.15 and 4.83 mg/kg for propofol and thiopentone, respectively. Half the patients in each group received a supplementary dose of the same induction agent (propofol 1.0 mg/kg or thiopentone 2.0 mg/kg) (corrected) prior to intubation. Both propofol and thiopentone produced a significant reduction in intra-ocular pressure which decreased further after administration of vecuronium as well as the second smaller dose of the induction agents. Intra-ocular pressure prior to intubation was lower in the two propofol groups in comparison to the corresponding thiopentone groups. Intubation was associated with an increase in intra-ocular pressure but it still remained significantly below the baseline values except in the group given one dose of thiopentone. Supplementary doses of induction agents before intubation attenuated the increase in intra-ocular pressure. Propofol was significantly more effective in this respect and this group showed the lowest intra-ocular pressure throughout the study period. However, administration of propofol resulted in a 30% incidence of pain on injection and a decrease in systolic arterial pressure of more than 30% in about half the patients.