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Canadian Journal of Anesthesia 47:211-214 (2000)
© Canadian Anesthesiologists' Society, 2000
Reports of Investigation

A comparison of midazolam, alfentanil and propofol for sedation in oupatient intraocular surgery

Fiona E. McHardy , MB CHB FRCA, Joanne Fortier, FRCPC, Frances Chung, FRCPC, Ananthan Krishnathas, MD and Scott I. Marshall , MB CHB FRCA

From the Department of Anaesthesiology, EC 2-046, Toronoto Western Hospital, 399 Bathurst St, University of Toronto, Toronto, Ontario, Canada.

Address correspondence to: Dr Frances Chung, Phone: 416-603-5118; Fax: 416-604-6494; E-mail: fchung{at}uhn.on.ca


   Abstract
TOP
 Abstract
Introduction
 Method
 Results
 Discussion
 References
 
Purpose: To determine the ideal sedative regimen for intraocular surgery under peribulbar or retrobulbar block. The addition of alfentanil and or propofol to midazolam was evaluated with regard to hemodynamic variables, respiratory rate, pain, anxiety, sedation, postoperative recovery and patient satisfaction.

Methods: Eighty two patients aged between 50 and 85 were recruited into this prospective, randomised, double blind study. Patients, in four groups, received 0.015 mg•kg–1 midazolam, 5 µg•kg–1 alfentanil and 0.15 mg•kg–1 propofol; 0.015 mg•kg–1 midazolam and 0.15 mg•kg–1 propofol; 0.015 mg•kg–1 midazolam and 5 µg•kg–1 alfentanil or 0.015 mg•kg–1 midazolam alone. Blood pressure, heart rate, respiratory rate, pain, anxiety and sedation scores were measured. Times to discharge from the Post Anesthesia Care Unit (PACU) and Day Surgery Unit (DSU) were documented. A 24 hr telephone interview was carried out to determine patient satisfaction.

Results: Systolic blood pressure of patients in groups that had received alfentanil was 6% lower than that of patients who had not (P < 0.05) at the time of insertion of intraocular block. Patients in the alfentanil groups also had lower respiratory rates during the first 15 min after drug administration, but all patients were given supplemental oxygen therefore oxygen saturation was unaffected. Pain scores of patients who had been given alfentanil were lower during the first postoperative hour than those who had not.

Conclusion: The addition of alfentanil to midazolam is advantageous in providing sedation for insertion of intraocular block.


   Introduction
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 Abstract
 Introduction
Method
 Results
 Discussion
 References
 
CATARACT extraction and intraocular lens implantation is one of the most frequently performed surgical procedures in the world. A sociodemographic analysis of 351 cataract patients revealed that the mean age was 70.6 ± 12.4 yr and 76.6% of the patients took medication for cardiovascular disease, diabetes, asthma or mental disorder.1 Cognitive impairment has been demonstrated in patients undergoing cataract surgery under local anesthesia with sedation, which has important implications for discharge.2 Sedation should increase comfort and provide amnesia, but not increase intraoperative complications, delay recovery or discharge.

Midazolam 0.015 mg•kg–1 provides effective sedation for cataract surgery in combination with fentanyl.3 Alfentanil 5 µg•kg–1 and 20 mg propofol have been used in combination with midazolam.4 We hypothesised that careful sedation with short acting drugs would be well accepted by patients and that increasing drug combinations may lead to more complications.


   Method
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 Abstract
 Introduction
 Method
Results
 Discussion
 References
 
Following ethics committee approval, informed consent was obtained from 82 patients aged 50 - 85 yr, ASA I - III, who were to undergo intraocular surgery under peribulbar or retrobulbar block. Surgery included cataract extraction, excision of pterygium, corneal transplant, trabeculectomy or a combination of these. Patients were excluded if they had: contraindications to any of the study drugs, visual impairment of the non operative eye, weight < 40 kg or > 100 kg, a history of drug or alcohol abuse, confusion, dementia, or communication difficulty resulting from deafness or language barrier. Baseline pain and anxiety scores were measured using a 100 mm visual analogue scale. Sedation scores were obtained on a 5 point scale with 1 = fully alert and oriented, 2 = drowsy, 3 = eyes closed but rousable to command, 4 = eyes closed but rousable to mild physical stimulation and 5 = unrousable to mild physical stimulation. Psychomotor testing was carried out using the Trieger Dot5 and Digit Symbol Substitution6 tests.

Patients were randomised by computer generated codes into one of four groups to receive: Group MAP - 0.015 mg•kg–1 midazolam + 5 µg•kg–1 alfentanil + 0.15 mg•kg–1 propofol; Group MP - 0.015 mg•kg–1 midazolam + placebo + 0.15 mg•kg–1 propofol; Group MA - 0.015 mg•kg–1 midazolam + 5µg•kg–1 alfentanil + placebo; Group M - 0.015 mg•kg–1 midazolam + placebo + placebo. Syringes were prepared by pharmacy and contained 1 mg•ml–1 midazolam, 500 µg•ml–1 alfentanil or an equivalent volume of saline, and 10 mg•ml–1 propofol or an equivalent volume of intralipid.

In the operating room, standard monitoring was instituted. Supplemental oxygen was administered at 6 1•min–1 by face mask. A 20 gauge intravenous cannula was inserted and attached to an infusion of normal saline. The anesthesiologist, who was blinded to the contents of the syringes, administered the drugs at 30 sec intervals in the order midazolam, alfentanil/placebo, propofol/placebo and the block was performed 30 sec later. If sedation was inadequate, further 0.0075 mg•kg–1 midazolam could be given every five minutes. Blood pressure, heart rate and respiratory rate were recorded every minute for five minutes and then every five minutes during surgery. Pain, anxiety and sedation scores were done after administration of the drugs, after the block and then every 20 min.

On arrival in the PACU, hemodynamic variables, respiratory rate, pain, anxiety and sedation scores were recorded every 30 min. The time to achieve a Post Anesthesia Discharge Scoring System7 score of 9 was noted. At 24 hr, patients were telephoned and asked whether they had experienced any nausea and vomiting, dizziness, drowsiness or pain.

Statistical analysis
The data were analysed using factorial analysis of variance, chi-square test, and Fisher's exact test, where appropriate. P < 0.05 was considered statistically significant. All analyses were carried out using SAS (version 6:12) statistical software.


   Results
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 Abstract
 Introduction
 Method
 Results
Discussion
 References
 
Data from 81 patients were analysed. There were 20 patients in groups MAP, MP and M, and 21 patients in group MA. There were no differences in demographic data among groups. The MAP group patients received 1.2 ± 0.4 mg midazolam, 345 ± 73 µg alfentanil and 10 ± 2 mg propofol. The MP group patients received 1.3 ± 0.4 mg midazolam and 11 ± 2.0 mg propofol, the MA group patients received 1.3 ± 0.3 mg midazolam and 365 ± 64.1 µg alfentanil, and group M received 1.2 ± 0.3 mg midazolam.

Systolic blood pressure of patients who received alfentanil, was 6.0% lower at five minutes than that of patients who had not (P < 0.05, Figure 1Go). This is the time at which the intraocular block was inserted. These patients also had lower respiratory rates for 15 min after drug administration, the lowest mean being 12.1 bpm at three minutes in Group MAP (P < 0.05, Figure 2Go). Oxygen saturation was unaffected.



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  		FIGURE 1 Graph of systolic blood pressure against time

 


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  		FIGURE 2 Graph of respiratory rate against time

 
Intraoperatively, addition of alfentanil and or propofol to midazolam did not affect pain, anxiety or sedation scores. Although postoperative pain scores were low in all groups, those of patients who had received alfentanil were lower during the first postoperative hour (P < 0.05, Table IGo).


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  		TABLE I Postoperative pain scores.
 
Increasing the number of sedative agents used did not have a deleterious effect on performance in the Trieger Dot and Digit Substitution tests (Table IIGo).


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  		TABLE II Results of the Digit Symbol Substitution (DSST) and Trieger Dot tests (TDT).
 
Average time spent in the PACU ranged from 29.5 min(Group MAP) to 35.5 min (Group M), and in the DBU from 41.8 min (Group MA) to 50.5 min (Group MAP). No patient suffered from nausea and vomiting.


   Discussion
TOP
 Abstract
 Introduction
 Method
 Results
 Discussion
References
 
In our study, alfentanil minimized the hemodynamic response to local anesthetic injection and reduced pain scores in the first postoperative hour. Neither midazolam alone or in combination with propofol was found to have these effects. Comparison of premedication for outpatient cataract surgery with intramuscular injections of alfentanil 12.5 µg•kg–1, midazolam 20 µg•kg–1 or placebo 15 min preoperatively,8 also found that alfentanil obtunded the hemodynamic response to block insertion. The importance of reassurance and gentle technique when performing the local anesthetic block cannot be overemphasised.9 We would also recommend that supplemental oxygen be administered to all patients who receive sedation.

We have demonstrated that the use of alfentanil is advantageous as part of a sedative regimen for ambulatory patients undergoing ophthalmic surgery. There was no increase in the incidence of postoperative nausea and vomiting or respiratory depression associated with its use.

Accepted for publication November 28, 1999.


   References
TOP
 Abstract
 Introduction
 Method
 Results
 Discussion
 References
 
1 Lumme P, Laatikainen L. Sociodemographic aspects and systemic diseases of cataract patients. Acta Opthalmol Scand 1994; 72: 79–85.

2 Chung FF, Chung A, Meier RH, Lautenschlaeger E, Seyone C. Comparison of perioperative mental function after general anaesthesia and spinal anaesthesia with intravenous sedation. Can J Anaesth 1989; 36: 382–7.[Abstract/Free Full Text]

3 Salmon JF, Mets B, James MFM, Murray AD. Intravenous sedation for ocular surgery under local anaesthesia. Br J Opthalmol 1992; 76: 598–601.[Abstract/Free Full Text]

4 Weinberg EJ, Sung Y. A comparison of midazolam and propofol as amnestics when used with retrobulbar and peribulbar blocks. Abstract from the Society for Ambulatory Anaesthesia 1995 Annual Meeting.

5 Newman MG, Trieger N, Miller JC. Measuring recovery from anesthesia - a simple test. Anesth Analg 1969; 48: 136–40.[Medline]

6 Lezak MD. Neuropsychological Assessment, 2nd ed. New York: Oxford University Press, 1983.

7 Chung F. Recovery pattern and home-readiness after ambulatory surgery. Anesth Analg 1995; 80: 896–902.[Abstract]

8 Virkkila MEJ, Ali-Melkkila TM, Kanto JH. Premedication for outpatient cataract surgery: a comparative study of intramuscular alfentanil, midazolam and placebo. Acta Anaesthesiol Scand 1992; 36: 559–63.[Medline]

9 Hamilton RC, Gimbel HV, Strunin L. Regional anaesthesia for 12000 cataract extraction and intraocular lens implantation procedures. Can J Anaesth 1988; 35: 615–23.[Abstract/Free Full Text]





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