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INTRAOCULAR PRESSURE CHANGES DURING RAPID SEQUENCE INDUCTION OF ANAESTHESIA: COMPARISON OF PROPOFOL AND THIOPENTONE IN COMBINATION WITH VECURONIUM
Br. J. Anaesth. (1988), 60, 379-383
INTRAOCULAR PRESSURE CHANGES DURING RAPID SEQUENCE INDUCTION OF ANAESTHESIA: COMPARISON OF PROPOFOL AND THIOPENTONE IN COMBINATION WITH VECURONIUM R. K. MIRAKHUR, W. F. I. SHEPHERD AND P. ELLIOTT
PATIENTS AND METHODS
SUMMARY Intraocular pressure (IOP) was measured during rapid sequence induction of anaesthesia using thiopentone or propofol as the induction agent and vecuronium for neuromuscular blockade. Vecuronium was administered in a dose of 0.15 mg kg~1 approximately 35 s before the induction agent. IOP was measured with a handheld app/anation tonometer before anaesthesia, following administration of the induction agent immediately after trachea/ intubation and cuff inflation and 1, 2 and 3 min later. IOP in the propofol group was significantly lower than in the thiopentone group, except immediately after induction, when reduction in IOP was similar and significant with both agents. IOP following intubation in patients in whom anaesthesia was induced with thiopentone was not significantly different from baseline values, but showed a significant increase from the pressure before intubation. In contrast, IOP after intubation in the propofol group remained not only significantly less than the baseline value, but also showed only a minimal and insignificant change in comparison with values before intubation. The frequency of side effects was low in both groups except for a significantly greater reduction in arterial pressure in those receiving propofol.
Forty adult patients conforming to ASA grades I or II were included in the study after their informed consent and approval from the Regional Ethics Committee had been obtained. All were to undergo elective ophthalmic surgery and any patient with an increased IOP (more than 20 mm study. Premedication consisted of diazepam Hg) before operation was excluded from the 10-15 mg by mouth. On arrival in the anaesthetic room the patient was given fentanyl 2 (ig kg"1 i.v. R. K. MIRAKHUR, M.D., PH.D., F.F.A.R.C.S., F.F.A.R.C.S.I.; P. Preoxygenation was carried out for 5 min with the ELLIOTT, M.D., F.F.A.R.C.S., Department of Clinical Anaesface mask being held lightly by the patient. thesia, Royal Victoria Hospital, Belfast. W. F. I. SHEPHERD, was administered in a dose of 0.15 F.R.C.S., Department of Ophthalmology, Queen's University Vecuronium 1 of Belfast, Belfast. Accepted for Publication: October 9, mg kg" . This was followed, as soon as the earliest 1987. subjective feelings of muscle weakness such as the
Downloaded from http://bja.oxfordjournals.org/ at East Carolina University on April 24, 2015
Induction of anaesthesia with propofol (2,6,diisopropylphenol) has been reported to be smooth, without major adverse effects and associated with rapid, smooth recovery [1—3]. Previous studies have shown that its use is also associated with significant reduction in intraocular pressure (IOP) and some benefit in attenuating the increase in IOP associated with tracheal intubation. In addition, many of these patients may present with a full stomach, but the use of perforated eye injuries. This is particularly so during induction of anaesthesia and tracheal intubation. In addition, many of these patients may present with a full stomach, but the use of suxamethonium (which is the neuromuscular blocking agent of choice for a rapid sequence induction in patients with a full stomach) may be considered contraindicated in patients with perforated eye injuries because of its well documented effect in increasing IOP. In the present study, intraocular pressure changes have been studied during a rapid sequence induction using propofol or thiopentone in combination with vecuronium.
BRITISH JOURNAL OF ANAESTHESIA
380 TABLE I. Grading of iniubating conditions
Grade Excellent Satisfactory Fair Poor
Criteria Good jaw relaxation, vocal cords open, no response to intubation Good jaw relaxation, vocal cords open, minimal reaction to intubation Jaw relaxed, cords moving, intubation requiring firm pressure and accompanied by moderate bucking or coughing Intubation impossible because of poor jaw or cord relaxation
Baseline After induction After intubation 1 min after intubation 2 min after intubation 3 min after intubation
Differences Differences at all times < 0.005
Propofol
Thiopentone
14.4 + 2.46 k 9.1+3.09** 9.9 ±2.79*'* 6.6 + 3.05*'1 5.9±2.48*1• 5.7 + 2.58*1•
14.1 ±2.75 9.8 + 2.23** 13.0±3.77 10.8 + 4.21* 9.3 ±3.63** 7.8 + 2.90**
The results were tested for statistical significance by analysis of variance and t tests. Intubating conditions were compared using the Fisher's Exact Test. RESULTS
The mean age and weight were 40 (16.4) yr (SD) and 66 (12.9) kg for the propofol group, and 43 (18.3) yr and 71 (12.7) kg for the thiopentone group, respectively, and these were not significantly different. The baseline IOP values were 14.4 (2.4) and 14.1 (2.75) mm Hg in the propofol and thiopentone groups, respectively; again the difference was not significant. IOP decreased significantly (P < 0.001) following administration of both propofol and thiopentone (table II). The reduction was greater with propofol (5.3 mm Hg or 37%) than with thiopentone (4.3 mm Hg or 30%), but this difference between the groups was not statistically significant. The IOP after intubation and cuff inflation increased from 9.8 mm Hg to 13.0 mm Hg in the group in whom anaesthesia was induced with thiopentone. Although it was still less than the baseline value, the increase from the value just before intubation was significant (P < 0.01). The IOP in the group given propofol increased from 9.1 to only 9.9 mm Hg following intubation and this change was not statistically significant. IOP was significantly less than (P < 0.01) the baseline values in both groups for the remainder of the study period. IOP values in the propofol group were significantly lower (P < 0.05) than in the thiopentone group throughout the study period, with the exception of the value recorded immediately after induction. Mean systolic arterial pressures (table III) before induction of anaesthesia were not sig-
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heaviness of the eyelids appeared, by the rapid administration of propofol or thiopentone, in a dose sufficient to abolish verbal communication with the patient. Cricoid pressure was applied immediately after administration of the induction agent and intubation and cuff inflation carried out 30 s later. Ventilation was started at this stage with nitrous oxide and isoflurane in oxygen. IOP was measured using a hand-held applanation tonometer before induction of anaesthesia (using amethocaine), after administration of the induction agent, immediately after intubation and cuff inflation and 1, 2 and 3 min later. Heart rate and systolic arterial pressure were measured at the same time as IOP using an electrocardiograph and oscillotonometer (Dinamap). The time to onset of complete blockade and duration of clinical neuromuscular blockade by vecuronium were determined using a peripheral nerve stimulator (Myotest) delivering a train-offour stimulation at 2 Hz every 10 s via cutaneous electrodes. Onset of complete block was denned as the time from administration of the blocking drug to the disappearance of all four responses, and the duration of clinical blockade as the time from administration of the myoneural blocker to the reappearance of all the four responses. Further smaller increments of vecuronium were administered as required at this stage. Intubating conditions were graded on a four-point scale as excellent, satisfactory, fair or poor, according to criteria listed in table I. Residual neuromuscular blockade was antagonized at the end of surgery with a mixture of neostigmine and glycopyrrolate. Side effects such as pain on injection, hiccup or spontaneous movements were also recorded. Patients were questioned the next day about the acceptability of anaesthesia.
TABLE II. Intraocular pressure (mm Hg±SD). from baseline significant: *P < 0.01; **P < 0.001. significant between propofol and thiopentone groups except baseline and after induction; P < 0.05-P
RAPID SEQUENCE INDUCTION AND IOP TABLE III. Systolic arterial pressure (mm Hg±SD). Differences significant compared with baseline: *P<0.05; **P < 0.005. Differences significant between propofol and thiopentone groups throughout except baseline (P < 0.005)
Propofol Baseline After induction After intubation 1 min after intubation 2 min after intubation 3 min after intubation
139+14.5 125+18.7** 129±27.2 115 + 21.4** 108±21.6** 104 + 21.3**
381 TABLE V. Intubating conditions and neuromuscular blockade
Propofol (n = 20)
Thiopentone (n = 20)
Thiopentone 151 + 24.6 154±29.2 163 ±30.3* 158±33.1 148 + 29.9 141 ±28.8*
Intubating conditions Excellent Satisfactory Time (± SD) to onset of complete blockade (s) Duration (± SD) of clinical blockade (min)
13 7
210±62.4
187 ±36.7
42 ±8.5
44±6.7
shown in table V. All the intugraded as satisfactory, but more as excellent in those receiving propofol (17 compared with 13). The onset and duration of clinical blockade of the initial 0.15Propofol Thiopentone mg kg"1 dose of vecuronium were 187 and 210 s and 42 and 44 min, respectively, in propofol and Baseline 82 + 21.3 77 + 17.3 thiopentone groups (ns). After induction 85 + 16.7 97±19.1** The average induction doses of propofol and After intubation 88 + 16.6 105 + 16.4** 1 min after intubation 85 + 16.1 100±16.4** thiopentone were 2.5 and 5.4 mg kg"1, respect2 min after intubation 83 + 16.0 93±15.7** ively, and the majority of injections were made 3 min after intubation 80 + 16.7 88 ±14.6* to a vein on the dorsum of the hand. End-tidal carbon dioxide concentration during surgery was maintained between 3.5 and 4.0 %. One patient in nificantly different in the two groups. Arterial each group complained of mild discomfort on pressure decreased significantly (P < 0.005) in the administration of the induction agent. There were propofol group and remained so throughout the no other side effects. Four patients in the propofol study period except after intubation. In the group and six in the thiopentone group suffered thiopentone group the only significant changes in from nausea, vomiting or both in the immediate arterial pressure were an increase after intubation postoperative period. There was no venous se(P < 0.01) and a decrease 3 min later (P < 0.05). quelae 24 h after anaesthesia. The induction The average peak decrease in systolic arterial sequence was deemed acceptable by all patients pressure was 25.4% in the propofol group and when they were questioned the day after anaes7.1% in the thiopentone group. Eleven patients thesia. receiving propofol demonstrated a decrease in arterial pressure of greater than 25%, three of DISCUSSION these exhibiting a reduction of more than 40%. However, hypotension was transient and res- Induction of anaesthesia for repair of a perforated ponded to 500-1000 ml of crystalloid solutions. eye injury in a patient with a full stomach is a Heart rate responses in the two groups were challenging situation for the anaesthetist. The also different (table IV). There was no significant important considerations are the protection of the change in mean heart rate in those given propofol, airway from the hazard of regurgitation and but heart rate increased significantly in those aspiration of the gastric contents, and preventing given thiopentone (P < 0.01) with a peak increase increases in IOP, consequent upon tracheal of approximately 37 % after intubation. intubation, with the harmful possibility of further The average time between administration of damage to the eye and even loss of the intraocular vecuronium and induction agent was approxi- contents. The role of neuromuscular blocking mately 35 s. The intubating conditions and the agents has been the subject of many previous onset and duration of clinical neuromuscular investigations, but in the present study the choice
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TABLE IV. Heart rate (beat min'1 ±SD). Differences from blockade are baseline significant: *P<0.05; **P < 0.005. Differences bations were significant between propofol and thiopentone throughout (Pwere < graded 0.01) except baseline
17 3
382
benefical effect of propofol may be the result of significantly greater hypotension with its use [2, 4, 5, 19], lack of antanalgesic action [20] or a possible greater "depth of anaesthesia " [21]. The doses of propofol and thiopentone required to induce anaesthesia in the present study are similar to those reported by others during normal induction in adult patients [2, 22]. The technique of induction has been shown to have important effects on IOP. Where an induction agent such as thiopentone is administered in a conventional manner before large doses of atracurium or vecuronium, there is still an increase in IOP following intubation [23]. This also occurs when propofol is the induction agent [24]. In the present study the administration of the induction agents after vecuronium ensured that the intubation was carried out at the peak effect of the induction agent and also approximately 90 s after administration of vecuronium (approximately 35 s between administration of the neuromuscular blocker and the induction agents, 25—30 s for administering the induction agent, and intubation 30 s after their administration). It has been shown previously that intubating conditions with vecuronium in doses of 0.1-0.15 mg kg"1 are satisfactory at approximately 90 s and that intubation using these doses can be carried out in the absence of complete paralysis [11, 25]. As a result of the use of propofol, vecuronium and this induction sequence, intubation was associated with only a small, insignificant increase in IOP. Careful assessment of the airway should be made before administration of the neuromuscular blocker, as would be the practice in any other situation. In the event of anticipated difficulty in intubation, it is prudent to avoid the use of myoneural blockade, to starve the patient and to use other means of securing the airway. Because of the significantly greater reduction in arterial pressure with the use of propofol, this agent should be used with caution or even avoided in situations in which severe hypotension is undesirable. However, the advantage of good control of IOP in otherwise healthy patients with perforated eye injuries may outweigh the risk of hypotension, which is usually transient and responds to simple measures such as i.v. fluid administration [5]. In conclusion, good control of IOP is achieved during a rapid sequence induction when vecuronium is followed by propofol. This may be a suitable technique for induction of anaesthesia in
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of the induction agent and the induction sequence itself have been examined. Suxamethonium is considered the myoneural blocker of choice for facilitating tracheal intubation during a rapid sequence induction in patients with a full stomach. However, its use is associated with an increase in IOP [6-8]. Vecuronium was used in the present study both for its beneficial effect in terms of a significant reduction in IOP [9, 10] and for its relatively short duration of action and lack of side effects, even when used in a moderately large dose of 0.15 mg kg~l [11]. It is well known that tracheal intubation itself may produce an increase in IOP irrespective of the neuromuscular blocking agent used [6, 8, 12, 13]. On this basis and because they could find no evidence of extrusion of ocular contents from retrospective analysis of case records, Libonati, Leahy and Ellison [14] advocated that it was safe to use suxamethonium in patients with perforated eye injuries, and this view has been supported in a more recent review [15]. However, Libonati, Leahy and Ellison [14] reviewed the records of fewer than 50% of the patients admitted with such eye injuries. In addition, they did not comment on the visual function of these patients and they could not have known if avoiding suxamethonium would have resulted in better functional results. It has been shown that, although the IOP increases following intubation with the use of both depolarizing and non-depolarizing neuromuscular blockers, the change is less with the use of the latter [8]. Non-depolarizing blocking agents such as pancuronium or alcuronium have been recommended for rapid sequence induction in patients with perforated eye injuries [16, 17], this suggestion being based on the fact that, in these studies, IOP after intubation was not significantly higher than the baseline values, even though the IOP increased following intubation. The technique of induction, in addition to the induction agent itself, has received little attention in rapid sequence inductions, regarding effects on IOP. Thiopentone is known to produce a significant reduction in IOP [13, 18]. Recent studies have not only confirmed this, but also shown that the newer agent, propofol, produces an even greater reduction in IOP and that its use may attenuate the subsequent increase in IOP produced by intubation [4, 5]. It appears that this advantage of propofol is also apparent when it is used as part of a rapid sequence induction. This
BRITISH JOURNAL OF ANAESTHESIA
RAPID SEQUENCE INDUCTION AND IOP
383
patients with a full stomach who are to undergo repair of perforated eye injuries, provided there are no contraindications to either the use of any of the agents used or the technique itself.
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10. Mirakhur RK, Shepherd WFI, Lavery GG, Elliott P. The effects of vecuronium on intra-ocular pressure. Anaesthesia 1987; 42: 944-949. 11. Mirakhur RK, Ferres CJ, Clarke RSJ, Bali IM, Dundee JW. Clinical evaluation of Org NC45. British Journal of Anaesthesia 1983; 55: 119-124. 12. Goldsmith E. an evaluation of succinylcholine and gallamine as muscle relaxants in relation in intraocular tension. Anesthesia and Analgesia 1967; 46: 557-561. ACKNOWLEDGEMENTS 13. Joshi C, Bruce DL. Thiopental and succinylcholine action The authors thank I.C.I, pic for supply of propofol used in the on intraocular pressure. Anesthesia and Analgesia 1975; present study and for financial assistance, and Miss Sharon 54: 471-475. Connery for secretarial help. 14. Libonati MM, Leahy JL, Ellison N. The use of succinylcholine in open eye surgery. Aneslhesiology 1985; 62: 637-640. 15. Cunningham AJ, Barry P. Intraocular pressure— physiology and implications for anaesthetic management. REFERENCES Canadian Anaesthetists Society Journal 1986; 33: 195-208. 16. Litwiller RW, Difazio CA, Rushia EL. Pancuronium and 1. Cummings GC, Dixon J, Kay NH, Windsor JPW, Major intraocular pressure. Anesthesiology 1975; 42: 750-752. E, Morgan M, Sear JW, Spence AA, Stephenson DK. Dose requirements of ICI 35868 (Propofol, 'Diprivan') 17. Balamoutsos NG, Tsakona H, Kanakoudes PH, Iliadelis in a new formulation for induction of anaesthesia. E, Georgiades CG. Alcuronium and intraocular pressure. Anaesthesia 1984; 39: 1168-1171. Anesthesia and Analgesia 1983; 62: 521-523. 18. Verma RS. "Self-taming" of succinylcholine-induced 2. Mackenzie N, Grant IS. Comparison of the new emulsion fasciculations and intraocular pressure. Anesthesiology; formulation of propofol with methohexitone and thio50: 245-247. pentone for induction of anaesthesia in day cases. British Journal of Anaesthesia 1985; 57: 725-731. 19. Fahy LT, VanMourik GA, Utting JE. A comparison of the induction characteristics of thiopentone and propofol. 3. Edelist G. A comparison of propofol and thiopentone as Anaesthesia 1985; 40: 939-944. induction agents in outpatient surgery. Canadian Journal 20. Briggs LP, Dundee JW, Bahar M, Clarke RSJ. Comof Anaesthesia 1987; 34: 110-116. parison of the effect of diisopropyl phenol (ICI 35868) and 4. Mirakhur RK, Shepherd WFI. Intraocular pressure thiopentone on response to somatic pain. British Journal changes with propofol ("Diprivan"): Comparison with of Anaesthesia 1982; 54: 307-311. thiopentone. Postgraduate Medical Journal 1985; 61 (Suppl. 3): 41^4. 21. Doze VA, Westphal LM, White PF. Comparison of propofol with methohexital for outpatient anesthesia. 5. Mirakhur RK, Shepherd WFI, Darrah WC. Propofol or Anesthesia and Analgesia 1986; 65: 1189-1195. thiopentone: effects on intraocular pressure associated with induction of anaesthesia and tracheal intubation 22. McCollum JSC, Dundee JW. Comparison of the induction characteristics of four intravenous anaesthetic (facilitated with suxamethonium). British Journal of agents. Anaesthesia 1986; 41: 995-1000. Anaesthesia; 59: 431-436. 6. Pandey K, Badola P, Kumar S. Time course of intraocular 23. Schneider MJ, Stirt JA, Finholt DA. Atracurium, vecuronium and intraocular pressure in humans. Anesthesia hypertension produced by suxamethonium. British and Analgesia 1986; 65: 877-882. Journal of Anaesthesia 1972; 44: 191-195. 7. Cook JH. The effect of suxamethonium on intraocular 24. Elliott P, Mirakhur RK, Shepherd WFI. Intraocular pressure during induction of anesthesia with propofol or pressure. Anaesthesia 1981; 36: 359-365. thiopental followed by vecuronium: influence of an 8. Lavery GG, McGalliard JN, Mirakhur RK, Shepherd addition dose of the induction agent. Anesthesiology 1987; WFI. The effects of atracurium on intraocular pressure 67: A484. during steady state anaesthesia and rapid sequence induction: a comparison with succinylcholine. Canadian 25. Agoston S, Salt P, Newton D, Bencini A, Boomsma P, Erdmann W. The neuromuscular blocking action of Org Anaesthetists Society Journal 1986; 33: 437^42. NC45, a new pancuronium derivative, in anaesthetized 9. Jantzen J-P, Hackett GH, Erdmann K, Earnshaw G. patients. A pilot study. British Journal of Anaesthesia Effect of vecuronium on intraocular pressure. British 1980;52:53S-59S. Journal of Anaesthesia 1986; 58: 433--136.
INTRAOCULAR PRESSURE CHANGES DURING RAPID SEQUENCE INDUCTION OF ANAESTHESIA: COMPARISON OF PROPOFOL AND THIOPENTONE IN COMBINATION WITH VECURONIUM R. K. MIRAKHUR, W. F. I. SHEPHERD AND P. ELLIOTT
PATIENTS AND METHODS
SUMMARY Intraocular pressure (IOP) was measured during rapid sequence induction of anaesthesia using thiopentone or propofol as the induction agent and vecuronium for neuromuscular blockade. Vecuronium was administered in a dose of 0.15 mg kg~1 approximately 35 s before the induction agent. IOP was measured with a handheld app/anation tonometer before anaesthesia, following administration of the induction agent immediately after trachea/ intubation and cuff inflation and 1, 2 and 3 min later. IOP in the propofol group was significantly lower than in the thiopentone group, except immediately after induction, when reduction in IOP was similar and significant with both agents. IOP following intubation in patients in whom anaesthesia was induced with thiopentone was not significantly different from baseline values, but showed a significant increase from the pressure before intubation. In contrast, IOP after intubation in the propofol group remained not only significantly less than the baseline value, but also showed only a minimal and insignificant change in comparison with values before intubation. The frequency of side effects was low in both groups except for a significantly greater reduction in arterial pressure in those receiving propofol.
Forty adult patients conforming to ASA grades I or II were included in the study after their informed consent and approval from the Regional Ethics Committee had been obtained. All were to undergo elective ophthalmic surgery and any patient with an increased IOP (more than 20 mm study. Premedication consisted of diazepam Hg) before operation was excluded from the 10-15 mg by mouth. On arrival in the anaesthetic room the patient was given fentanyl 2 (ig kg"1 i.v. R. K. MIRAKHUR, M.D., PH.D., F.F.A.R.C.S., F.F.A.R.C.S.I.; P. Preoxygenation was carried out for 5 min with the ELLIOTT, M.D., F.F.A.R.C.S., Department of Clinical Anaesface mask being held lightly by the patient. thesia, Royal Victoria Hospital, Belfast. W. F. I. SHEPHERD, was administered in a dose of 0.15 F.R.C.S., Department of Ophthalmology, Queen's University Vecuronium 1 of Belfast, Belfast. Accepted for Publication: October 9, mg kg" . This was followed, as soon as the earliest 1987. subjective feelings of muscle weakness such as the
Downloaded from http://bja.oxfordjournals.org/ at East Carolina University on April 24, 2015
Induction of anaesthesia with propofol (2,6,diisopropylphenol) has been reported to be smooth, without major adverse effects and associated with rapid, smooth recovery [1—3]. Previous studies have shown that its use is also associated with significant reduction in intraocular pressure (IOP) and some benefit in attenuating the increase in IOP associated with tracheal intubation. In addition, many of these patients may present with a full stomach, but the use of perforated eye injuries. This is particularly so during induction of anaesthesia and tracheal intubation. In addition, many of these patients may present with a full stomach, but the use of suxamethonium (which is the neuromuscular blocking agent of choice for a rapid sequence induction in patients with a full stomach) may be considered contraindicated in patients with perforated eye injuries because of its well documented effect in increasing IOP. In the present study, intraocular pressure changes have been studied during a rapid sequence induction using propofol or thiopentone in combination with vecuronium.
BRITISH JOURNAL OF ANAESTHESIA
380 TABLE I. Grading of iniubating conditions
Grade Excellent Satisfactory Fair Poor
Criteria Good jaw relaxation, vocal cords open, no response to intubation Good jaw relaxation, vocal cords open, minimal reaction to intubation Jaw relaxed, cords moving, intubation requiring firm pressure and accompanied by moderate bucking or coughing Intubation impossible because of poor jaw or cord relaxation
Baseline After induction After intubation 1 min after intubation 2 min after intubation 3 min after intubation
Differences Differences at all times < 0.005
Propofol
Thiopentone
14.4 + 2.46 k 9.1+3.09** 9.9 ±2.79*'* 6.6 + 3.05*'1 5.9±2.48*1• 5.7 + 2.58*1•
14.1 ±2.75 9.8 + 2.23** 13.0±3.77 10.8 + 4.21* 9.3 ±3.63** 7.8 + 2.90**
The results were tested for statistical significance by analysis of variance and t tests. Intubating conditions were compared using the Fisher's Exact Test. RESULTS
The mean age and weight were 40 (16.4) yr (SD) and 66 (12.9) kg for the propofol group, and 43 (18.3) yr and 71 (12.7) kg for the thiopentone group, respectively, and these were not significantly different. The baseline IOP values were 14.4 (2.4) and 14.1 (2.75) mm Hg in the propofol and thiopentone groups, respectively; again the difference was not significant. IOP decreased significantly (P < 0.001) following administration of both propofol and thiopentone (table II). The reduction was greater with propofol (5.3 mm Hg or 37%) than with thiopentone (4.3 mm Hg or 30%), but this difference between the groups was not statistically significant. The IOP after intubation and cuff inflation increased from 9.8 mm Hg to 13.0 mm Hg in the group in whom anaesthesia was induced with thiopentone. Although it was still less than the baseline value, the increase from the value just before intubation was significant (P < 0.01). The IOP in the group given propofol increased from 9.1 to only 9.9 mm Hg following intubation and this change was not statistically significant. IOP was significantly less than (P < 0.01) the baseline values in both groups for the remainder of the study period. IOP values in the propofol group were significantly lower (P < 0.05) than in the thiopentone group throughout the study period, with the exception of the value recorded immediately after induction. Mean systolic arterial pressures (table III) before induction of anaesthesia were not sig-
Downloaded from http://bja.oxfordjournals.org/ at East Carolina University on April 24, 2015
heaviness of the eyelids appeared, by the rapid administration of propofol or thiopentone, in a dose sufficient to abolish verbal communication with the patient. Cricoid pressure was applied immediately after administration of the induction agent and intubation and cuff inflation carried out 30 s later. Ventilation was started at this stage with nitrous oxide and isoflurane in oxygen. IOP was measured using a hand-held applanation tonometer before induction of anaesthesia (using amethocaine), after administration of the induction agent, immediately after intubation and cuff inflation and 1, 2 and 3 min later. Heart rate and systolic arterial pressure were measured at the same time as IOP using an electrocardiograph and oscillotonometer (Dinamap). The time to onset of complete blockade and duration of clinical neuromuscular blockade by vecuronium were determined using a peripheral nerve stimulator (Myotest) delivering a train-offour stimulation at 2 Hz every 10 s via cutaneous electrodes. Onset of complete block was denned as the time from administration of the blocking drug to the disappearance of all four responses, and the duration of clinical blockade as the time from administration of the myoneural blocker to the reappearance of all the four responses. Further smaller increments of vecuronium were administered as required at this stage. Intubating conditions were graded on a four-point scale as excellent, satisfactory, fair or poor, according to criteria listed in table I. Residual neuromuscular blockade was antagonized at the end of surgery with a mixture of neostigmine and glycopyrrolate. Side effects such as pain on injection, hiccup or spontaneous movements were also recorded. Patients were questioned the next day about the acceptability of anaesthesia.
TABLE II. Intraocular pressure (mm Hg±SD). from baseline significant: *P < 0.01; **P < 0.001. significant between propofol and thiopentone groups except baseline and after induction; P < 0.05-P
RAPID SEQUENCE INDUCTION AND IOP TABLE III. Systolic arterial pressure (mm Hg±SD). Differences significant compared with baseline: *P<0.05; **P < 0.005. Differences significant between propofol and thiopentone groups throughout except baseline (P < 0.005)
Propofol Baseline After induction After intubation 1 min after intubation 2 min after intubation 3 min after intubation
139+14.5 125+18.7** 129±27.2 115 + 21.4** 108±21.6** 104 + 21.3**
381 TABLE V. Intubating conditions and neuromuscular blockade
Propofol (n = 20)
Thiopentone (n = 20)
Thiopentone 151 + 24.6 154±29.2 163 ±30.3* 158±33.1 148 + 29.9 141 ±28.8*
Intubating conditions Excellent Satisfactory Time (± SD) to onset of complete blockade (s) Duration (± SD) of clinical blockade (min)
13 7
210±62.4
187 ±36.7
42 ±8.5
44±6.7
shown in table V. All the intugraded as satisfactory, but more as excellent in those receiving propofol (17 compared with 13). The onset and duration of clinical blockade of the initial 0.15Propofol Thiopentone mg kg"1 dose of vecuronium were 187 and 210 s and 42 and 44 min, respectively, in propofol and Baseline 82 + 21.3 77 + 17.3 thiopentone groups (ns). After induction 85 + 16.7 97±19.1** The average induction doses of propofol and After intubation 88 + 16.6 105 + 16.4** 1 min after intubation 85 + 16.1 100±16.4** thiopentone were 2.5 and 5.4 mg kg"1, respect2 min after intubation 83 + 16.0 93±15.7** ively, and the majority of injections were made 3 min after intubation 80 + 16.7 88 ±14.6* to a vein on the dorsum of the hand. End-tidal carbon dioxide concentration during surgery was maintained between 3.5 and 4.0 %. One patient in nificantly different in the two groups. Arterial each group complained of mild discomfort on pressure decreased significantly (P < 0.005) in the administration of the induction agent. There were propofol group and remained so throughout the no other side effects. Four patients in the propofol study period except after intubation. In the group and six in the thiopentone group suffered thiopentone group the only significant changes in from nausea, vomiting or both in the immediate arterial pressure were an increase after intubation postoperative period. There was no venous se(P < 0.01) and a decrease 3 min later (P < 0.05). quelae 24 h after anaesthesia. The induction The average peak decrease in systolic arterial sequence was deemed acceptable by all patients pressure was 25.4% in the propofol group and when they were questioned the day after anaes7.1% in the thiopentone group. Eleven patients thesia. receiving propofol demonstrated a decrease in arterial pressure of greater than 25%, three of DISCUSSION these exhibiting a reduction of more than 40%. However, hypotension was transient and res- Induction of anaesthesia for repair of a perforated ponded to 500-1000 ml of crystalloid solutions. eye injury in a patient with a full stomach is a Heart rate responses in the two groups were challenging situation for the anaesthetist. The also different (table IV). There was no significant important considerations are the protection of the change in mean heart rate in those given propofol, airway from the hazard of regurgitation and but heart rate increased significantly in those aspiration of the gastric contents, and preventing given thiopentone (P < 0.01) with a peak increase increases in IOP, consequent upon tracheal of approximately 37 % after intubation. intubation, with the harmful possibility of further The average time between administration of damage to the eye and even loss of the intraocular vecuronium and induction agent was approxi- contents. The role of neuromuscular blocking mately 35 s. The intubating conditions and the agents has been the subject of many previous onset and duration of clinical neuromuscular investigations, but in the present study the choice
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TABLE IV. Heart rate (beat min'1 ±SD). Differences from blockade are baseline significant: *P<0.05; **P < 0.005. Differences bations were significant between propofol and thiopentone throughout (Pwere < graded 0.01) except baseline
17 3
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benefical effect of propofol may be the result of significantly greater hypotension with its use [2, 4, 5, 19], lack of antanalgesic action [20] or a possible greater "depth of anaesthesia " [21]. The doses of propofol and thiopentone required to induce anaesthesia in the present study are similar to those reported by others during normal induction in adult patients [2, 22]. The technique of induction has been shown to have important effects on IOP. Where an induction agent such as thiopentone is administered in a conventional manner before large doses of atracurium or vecuronium, there is still an increase in IOP following intubation [23]. This also occurs when propofol is the induction agent [24]. In the present study the administration of the induction agents after vecuronium ensured that the intubation was carried out at the peak effect of the induction agent and also approximately 90 s after administration of vecuronium (approximately 35 s between administration of the neuromuscular blocker and the induction agents, 25—30 s for administering the induction agent, and intubation 30 s after their administration). It has been shown previously that intubating conditions with vecuronium in doses of 0.1-0.15 mg kg"1 are satisfactory at approximately 90 s and that intubation using these doses can be carried out in the absence of complete paralysis [11, 25]. As a result of the use of propofol, vecuronium and this induction sequence, intubation was associated with only a small, insignificant increase in IOP. Careful assessment of the airway should be made before administration of the neuromuscular blocker, as would be the practice in any other situation. In the event of anticipated difficulty in intubation, it is prudent to avoid the use of myoneural blockade, to starve the patient and to use other means of securing the airway. Because of the significantly greater reduction in arterial pressure with the use of propofol, this agent should be used with caution or even avoided in situations in which severe hypotension is undesirable. However, the advantage of good control of IOP in otherwise healthy patients with perforated eye injuries may outweigh the risk of hypotension, which is usually transient and responds to simple measures such as i.v. fluid administration [5]. In conclusion, good control of IOP is achieved during a rapid sequence induction when vecuronium is followed by propofol. This may be a suitable technique for induction of anaesthesia in
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of the induction agent and the induction sequence itself have been examined. Suxamethonium is considered the myoneural blocker of choice for facilitating tracheal intubation during a rapid sequence induction in patients with a full stomach. However, its use is associated with an increase in IOP [6-8]. Vecuronium was used in the present study both for its beneficial effect in terms of a significant reduction in IOP [9, 10] and for its relatively short duration of action and lack of side effects, even when used in a moderately large dose of 0.15 mg kg~l [11]. It is well known that tracheal intubation itself may produce an increase in IOP irrespective of the neuromuscular blocking agent used [6, 8, 12, 13]. On this basis and because they could find no evidence of extrusion of ocular contents from retrospective analysis of case records, Libonati, Leahy and Ellison [14] advocated that it was safe to use suxamethonium in patients with perforated eye injuries, and this view has been supported in a more recent review [15]. However, Libonati, Leahy and Ellison [14] reviewed the records of fewer than 50% of the patients admitted with such eye injuries. In addition, they did not comment on the visual function of these patients and they could not have known if avoiding suxamethonium would have resulted in better functional results. It has been shown that, although the IOP increases following intubation with the use of both depolarizing and non-depolarizing neuromuscular blockers, the change is less with the use of the latter [8]. Non-depolarizing blocking agents such as pancuronium or alcuronium have been recommended for rapid sequence induction in patients with perforated eye injuries [16, 17], this suggestion being based on the fact that, in these studies, IOP after intubation was not significantly higher than the baseline values, even though the IOP increased following intubation. The technique of induction, in addition to the induction agent itself, has received little attention in rapid sequence inductions, regarding effects on IOP. Thiopentone is known to produce a significant reduction in IOP [13, 18]. Recent studies have not only confirmed this, but also shown that the newer agent, propofol, produces an even greater reduction in IOP and that its use may attenuate the subsequent increase in IOP produced by intubation [4, 5]. It appears that this advantage of propofol is also apparent when it is used as part of a rapid sequence induction. This
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patients with a full stomach who are to undergo repair of perforated eye injuries, provided there are no contraindications to either the use of any of the agents used or the technique itself.
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10. Mirakhur RK, Shepherd WFI, Lavery GG, Elliott P. The effects of vecuronium on intra-ocular pressure. Anaesthesia 1987; 42: 944-949. 11. Mirakhur RK, Ferres CJ, Clarke RSJ, Bali IM, Dundee JW. Clinical evaluation of Org NC45. British Journal of Anaesthesia 1983; 55: 119-124. 12. Goldsmith E. an evaluation of succinylcholine and gallamine as muscle relaxants in relation in intraocular tension. Anesthesia and Analgesia 1967; 46: 557-561. ACKNOWLEDGEMENTS 13. Joshi C, Bruce DL. Thiopental and succinylcholine action The authors thank I.C.I, pic for supply of propofol used in the on intraocular pressure. Anesthesia and Analgesia 1975; present study and for financial assistance, and Miss Sharon 54: 471-475. Connery for secretarial help. 14. Libonati MM, Leahy JL, Ellison N. The use of succinylcholine in open eye surgery. Aneslhesiology 1985; 62: 637-640. 15. Cunningham AJ, Barry P. Intraocular pressure— physiology and implications for anaesthetic management. REFERENCES Canadian Anaesthetists Society Journal 1986; 33: 195-208. 16. Litwiller RW, Difazio CA, Rushia EL. Pancuronium and 1. Cummings GC, Dixon J, Kay NH, Windsor JPW, Major intraocular pressure. Anesthesiology 1975; 42: 750-752. E, Morgan M, Sear JW, Spence AA, Stephenson DK. Dose requirements of ICI 35868 (Propofol, 'Diprivan') 17. Balamoutsos NG, Tsakona H, Kanakoudes PH, Iliadelis in a new formulation for induction of anaesthesia. E, Georgiades CG. Alcuronium and intraocular pressure. Anaesthesia 1984; 39: 1168-1171. Anesthesia and Analgesia 1983; 62: 521-523. 18. Verma RS. "Self-taming" of succinylcholine-induced 2. Mackenzie N, Grant IS. Comparison of the new emulsion fasciculations and intraocular pressure. Anesthesiology; formulation of propofol with methohexitone and thio50: 245-247. pentone for induction of anaesthesia in day cases. British Journal of Anaesthesia 1985; 57: 725-731. 19. Fahy LT, VanMourik GA, Utting JE. A comparison of the induction characteristics of thiopentone and propofol. 3. Edelist G. A comparison of propofol and thiopentone as Anaesthesia 1985; 40: 939-944. induction agents in outpatient surgery. Canadian Journal 20. Briggs LP, Dundee JW, Bahar M, Clarke RSJ. Comof Anaesthesia 1987; 34: 110-116. parison of the effect of diisopropyl phenol (ICI 35868) and 4. Mirakhur RK, Shepherd WFI. Intraocular pressure thiopentone on response to somatic pain. British Journal changes with propofol ("Diprivan"): Comparison with of Anaesthesia 1982; 54: 307-311. thiopentone. Postgraduate Medical Journal 1985; 61 (Suppl. 3): 41^4. 21. Doze VA, Westphal LM, White PF. Comparison of propofol with methohexital for outpatient anesthesia. 5. Mirakhur RK, Shepherd WFI, Darrah WC. Propofol or Anesthesia and Analgesia 1986; 65: 1189-1195. thiopentone: effects on intraocular pressure associated with induction of anaesthesia and tracheal intubation 22. McCollum JSC, Dundee JW. Comparison of the induction characteristics of four intravenous anaesthetic (facilitated with suxamethonium). British Journal of agents. Anaesthesia 1986; 41: 995-1000. Anaesthesia; 59: 431-436. 6. Pandey K, Badola P, Kumar S. Time course of intraocular 23. Schneider MJ, Stirt JA, Finholt DA. Atracurium, vecuronium and intraocular pressure in humans. Anesthesia hypertension produced by suxamethonium. British and Analgesia 1986; 65: 877-882. Journal of Anaesthesia 1972; 44: 191-195. 7. Cook JH. The effect of suxamethonium on intraocular 24. Elliott P, Mirakhur RK, Shepherd WFI. Intraocular pressure during induction of anesthesia with propofol or pressure. Anaesthesia 1981; 36: 359-365. thiopental followed by vecuronium: influence of an 8. Lavery GG, McGalliard JN, Mirakhur RK, Shepherd addition dose of the induction agent. Anesthesiology 1987; WFI. The effects of atracurium on intraocular pressure 67: A484. during steady state anaesthesia and rapid sequence induction: a comparison with succinylcholine. Canadian 25. Agoston S, Salt P, Newton D, Bencini A, Boomsma P, Erdmann W. The neuromuscular blocking action of Org Anaesthetists Society Journal 1986; 33: 437^42. NC45, a new pancuronium derivative, in anaesthetized 9. Jantzen J-P, Hackett GH, Erdmann K, Earnshaw G. patients. A pilot study. British Journal of Anaesthesia Effect of vecuronium on intraocular pressure. British 1980;52:53S-59S. Journal of Anaesthesia 1986; 58: 433--136.