Abstract
Dexmedetomidine is a centrally acting α-2 receptor agonist that is used as anaesthesia during surgical procedures. It has several properties that make it suitable for use during monitored anaesthesia care (MAC). DEX has analgesic properties thus there is considerably reduced opioids requirements both before and after surgery (Candiotti, et al., 2010). Tachychardia and hypertension are mitigated by the symphatholytic effect of DEX. It has also been known to be friendly to respiratory system as it does not depress the respiratory system during its use. These properties make it suitable for MAC during orthopedic, ophthalmic, plastic surgery, dental and diagnostic procedures. This study sought to establish the suitability of the use of DEX during the following surgical procedures: TRUS (Trans-Rectal Ultrasound-guided) biopsy, cytoscopy and hysteroscopy. The main focus was patient and surgeon satisfaction and airway manipulation during the procedures. The study was carried out on 9 hysteroscopy patients, 6 TRUS patients and 5 cytoscopy patients. Each patient was administered with a loading dose of dexmedetomidine 1.5 mcg per kg over 15 min and maintenance infusion of 1.4 mcg per kg per hour. Observations on the patients in each category were then made. For hysteroscopy the patients’ satisfaction was ranked at between 7.85 -8 on a scale of 10. The cytoscopy patients’ satisfaction ranged from 6 to 8 out of 10. The TRUS patients’ satisfaction was 8 out of 10. None of the TRUS patients developed respiratory complications. In all the procedures the surgeons were satisfied with the use of DEX and there was no airway manipulation except in cytoscopy. Dexmedetomidine can therefore be recommended for use during surgical procedures because of it does allows the patients to breath normally even under heavy sedation unlike other drugs such as midazolam.
1.0 Introduction
The Therapeutic Goods Administration has approved dexmedetomidine for use in Intensive care units during surgical procedures such as orthopedic, ophthalmic, plastic surgery, dental and diagnostic procedures. During this study the effects of Dexmedetomidine during three procedures was observers: cytoscopy, hysteroscopy and TRUS. Cytoscopy is a procedure that involves the use of cystoscope to view the urethra. During the insertion of the cystoscope, the patients might have to be injected with a sedative.
Hysteroscopy entails the insertion of hysteroscope into the vagina, uterus or cervix, introduction of a gas in order to expand the uterus and viewing the images on a monitor for diagnostic purposes. The distension of the uterus or the dilation of the cervix during hysteroscopy has been known to cause discomfort hence the need for anaesthesia to relieve the discomfort. The dilation of the cervix can be well tolerated to a certain extent but in some cases, surgeons have to perform a paracervical block which involves administration of local anaesthesia into the cervix. Trans-rectal Ultrasound guided biopsy of the prostate (TRUS biopsy) can either be performed in the radiology department or surgeon’s office with no systemic anaesthesia or sedation.
For each of these surgical procedures and for many others, the most commonly used sedatives are propofol, fentalyn and midazolam. The risk of hypoxemia has been known to increase as a result of the combination of fentalyn and midazolam. Dexmedetomidine is therefore regarded as a safer option since it does not trigger depression of the respiratory system.
2.0 Materials and methods
There were 9 hysteroscopy patients, 5 cytoscopy patients and 6 TRUS patients. The hysteroscopy patients were aged between 23 and 46 and their weight was between 49 and 109 (49 ,,64 ,65 ,65 ,66 ,68 ,72 ,106 ,109 ). All patients were provided with 6 litres of oxygen per minute which was delivered via a Hudson mask and intravenous fluid. 3 of the patients had cervical block which was performed by the surgeon. All the patients were administered with 0.4 mg of Glycopyrolate IV at the start of the procedure to avoid bradycardia. 2 micrograms per kg of fentalyn was administered. 1.5 mcg per kg of dexmedetomidine administered over 15 minutes and maintenance infusion initiated at 1.4 mcg per kg per hour. There were 6 TRUS patients whose weights were as follows: 64, 87, 83, 96, 104, and 109. The same doses that were administered for the hysteroscopy patients were administered for these patients. For the 5 cystoscopy patients whose ages fell between 60 and 76, with weights of 69, 80, 82, 87 and 89: the same doses were administered. The patients were monitored and requested to rank their satisfaction on a scale of 1 to 10 while surgeon were requested to state if they were satisfied with the use of DEX in the respective procedures.
3.0 Results
For the hysteroscopy patients the following observations were made: In one of the patients the use DEX had to stopped and general anaesthesia used in its place due discomfort experienced by the patient. During the recovery of the patient, administration of intravenous fluid continued. 3 of the patients needed 500 mls bolus of normal saline for the treatment of hypotension. One patient required overnight admission due to on-going nausea. Patient satisfaction ranged between 7 and 8.5 with one of patients ranking it at 10. The surgeon was satisfied and there was no airway manipulation required.
For the TRUS patients, the following observations were made: the surgeons were satisfied given that none of the patients required airway manipulation. Patient satisfaction ranged between 6 -8 out of 10.
For the cytoscopy patients, one of patients required vasopressor intraoperation for hypotension (6 mg of Ephedrine). Patient satisfaction was between 8 and 10. Surgeons were dissatisfied due to the patients’ movement.
Discussion
Dexmedetomidine has a unique mechanism of action thus has been the subject of many reviews. It is α- 2 adrenergic agonist. Even under deep levels of sedation with dexmedetomidine, patients still maintain normal breathing functions (Reves et al ., 2006). In this study none of the patients required airway manipulation, an observation that concurs with other studies.
A study involving patients on a placebo (midazolam and fentalyn) and others on Dexmedetomidine showed that 13.1% and 16.1% of the patients, who were administered with the placebo respectively, required an intervention for respiratory depression at some point. It was also found that 12.7% had a documented oxygen saturation of less than 90% or respiratory rate of less than 8 (Candiotti, et al., 2010). This may be as a result of the considerably higher doses of midazolam and fentalyn which were needed for sedation and analgesia in the placebo group versus the dexmedetomidine treatment groups.
The manifestation of hypotension in some of the study subjects has been documented in other studies. In this study, 3 of the patients had to be administered with 500 mls of normal saline during recovery in order to treat them for hypotension. This was also seen in a study involving the patients on dexmedetomidine and those on placebo. Patients were observed to have mild to moderate forms on hypotension during which later on responded well to treatment (Candiotti, et al., 2010).
Dexmedetomidine is well tolerated among individuals with a diverse range of ages. It is also used for a broad range of procedures from those in this study to ophthalmic surgery, orthopaedic surgery and dental surgery. It has been known to cause a decrease in arterial blood pressure an effect that contributes to the prevention of anxiety during surgical procedures.
The levels of patient satisfaction recorded in the study were quite high with most of the patients ranking dexmedetomidine between 6 and 8 with a few exceptions of 10. Other trials have also shown considerably high levels of satisfaction with the drug. Higher levels of satisfaction have been seen in other trials as compared to patients who have been given midazolam during their surgery (Reves et al ., 2006).
Recommendations
The use of dexmedetomidine in the above named procedures offers further evidence of the advantage of dexmedetomidine over other anaesthetics since it does not depress the respiratory system. It use during surgical procedures would come in handy in reducing the instances of cases of malpractice. A review carried out in 2006 by American Society of Anesthesiologists’ Closed Claim Database showed that over sedation which triggers respiratory depression has a key role in causing injuries to patients during monitored anaesthetic care (Reves et al ., 2006) . The need for a sedative that does not pose a risk to the respiratory complications in both healthy and high risk patients is therefore met by the use of dexmedetomidine hence its use ought to be prescribed more often.
During the course of this study, a paracervical block was used for some of patients who underwent hysteroscopy. Further studies ought to be carried out to determine if the procedure can be performed without the use of the cervical block. This would enable the finding on the analgesic properties of dexmedetomidine to be studied and the findings made available for application by surgeons who perform the procedure.
Conclusion
Dexmedetomidine is a sedative that is well tolerated by patients during surgical procedures in addition to being safe given that it does not cause depression to the respiratory system. Although dexmedetomidine is an attractive drug for monitored anesthesia care (MAC), further studies on appropriate dosage according to patients’ age or race or the presence of other drugs and on method of infusion suitable for each procedures are required for safe use.
References
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Candiotti, K. A., Bergese, S. D., Bokesch, P. M., Feldman, M. A., Wisemandle, W., & Bekker, A. Y. (2010). Monitored Anesthesia Care with Dexmedetomidine: A Prospective, Randomized, Double-Blind, Multicenter Trial. Miami: Ambulatory Anesthesiology.
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Reves, J., Glass, P. S., Lubarsky, D. A., McEvo, M. D., & Martinez-Ruiz, R. (2006). Miller’s Anesthesia. In R. D. Miller, L. I. Eriksson, L. A. Fleisher, J. P. Young, Wiener-Kronis, & L. William, Intravenous Anesthetics (pp. 134-150). New York: Cambridge University.
