Patient maintained sedation for colonoscopy using a target controlled infusion of propofol – pdf brain anoxia

1 anaesthesia, 2004, 59, pages patient maintained sedation for colonoscopy using a target controlled infusion of propofol* L. Campbell, 1 G. Imrie, 2 P. Doherty, 2 C. Porteous, 2 K. Millar, 3 G. N. C. Kenny, 4 and G. Fletcher 2 1 consultant anaesthetist, department of anaesthetics, the royal sussex county hospital, eastern road, brighton, BN2 5BE, UK 2 departments of anaesthesia and surgery, royal alexandra hospital, corsebar road, paisley PA2 9PN, UK 3 section of psychological medicine, university of glasgow, academic centre, gartnavel royal hospital, 1055 great western road, glasgow,G12 0XH, UK 4 department of anaesthetics, royal infirmary of glasgow, 10 alexandra parade, glasgow, G31 2ER, UK summary in this study, we evaluated safety and recovery using a patient maintained, target controlled infusion of propofol for sedation in 20 patients undergoing colonoscopy.Brain anoxia

using a handset with a two-minute lockout interval, patients could make 0.2 lg.Ml )1 increments to an initial target plasma concentration of 1 lg.Ml )1 up to a maximum 4.5 lg.Ml )1. Four patients became oversedated but required no airway or circulatory interventions. Subjects had a significant reduction in mean (SD) heart rate: 78.7 (15) vs (13.5) (p 5) and three were to increase sedation. All patients maintained an oxygen saturation 94% throughout the period of monitoring and although one patient vomited during the procedure this resulted in no airway soiling. Compared to pre sedation measurements, there was a significant decrease in mean (SD) heart rate 78.7 (15) vs (13.5) (p 0.001, 95% CI 4.47, 13.03) beat.Min )1 and systolic blood pressure (13.2) vs (8.6) (p % CI 18.8, 30.3) mmhg.Brain anoxia the median (IQR [range]) maximum target propofol level during the sedation period was 2.7 lg ml )1 (2.4, 3.0[2 3.4]) (fig. 2) and sedation score level was three or higher in all patients whilst the colonoscopy was carried out. Fifteen min after colonoscopy all patients had a sedation score of three or less and all were able to complete the CRT test. Comparison of pre and post sedation total CRT test results showed a statistically significant prolongation in total CRT post colonoscopy. The median (IQR [range]) total rise in CRT was 162 ()16, [) ]) ms (p % CI 50, 343). The subjects made a total of eight errors overall, in number selection, five were made in the presedation period and three after sedation was discontinued.Brain anoxia of note six patients had a faster total CRT following sedation. A postoperative questionnaire, given to patients in the recovery period, confirmed overall patient satisfaction and low rate of recall. All patients were satisfied with the technique and were prepared to have the same sedative in the future. Only two patients had any recall at all of the procedure and this was rated as not unpleasant. Only one patient made negative comment, which was related to mild discomfort in the arm caused by the infusion. Discussion time (minutes) figure 2 median TCI propofol levels during study period. We have assessed a PMS system for colonoscopy and demonstrated it has significant but mild effects on Ó 2004 blackwell publishing ltd 129

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4 L. Campbell et al. Æ propofol sedation for colonoscopy anaesthesia, 2004, 59, pages cardiovascular parameters, is associated with rapid recovery and is popular with patients. In its current form however, problems with oversedation exist. Although in this study, statistically significant haemodynamic changes in pulse and systolic blood pressure are documented, the actual clinical significance of these is debatable. In no case was treatment or intervention required. It has been noted in previous studies that changes in heart rate and blood pressure occur during colonoscopy with other forms of sedation and indeed, may also occur when no sedation at all is used [3, 27 30]. In this study the reduction in heart rate was seen more commonly either during or after colonoscopy.Brain anoxia the lowest pulse rate recorded in any patient was 46 beat.Min )1 and that patient had a low baseline pulse rate of 50. It is likely therefore that the reduction in heart rate we measured reflects reduction in level of anxiety and stimulation by the sedation rather than any true vagal response to the colonoscopy itself. Reduction in blood pressure occurred immediately prior to or at the start of colonoscopy. Propofol is known to have mild cardio-depressant and vasodilatory effects, which could be responsible for this observation. In addition, the patients in this study, having had colonic preparation, may be mildly dehydrated which would tend to exaggerate these effects on blood pressure. Although, as with heart rate reduction, no patient required treatment and the blood pressure normalised in the course of the procedure or during recovery, it may be that, for patients with cardiovascular disease, caution using the system should be recommended.Brain anoxia the patients in this study were a relatively young and fit group (table 2). Hypotension may be more problematic in elderly patients or less fit patients so this method of sedation cannot be currently recommended in those groups. However, it should be noted that other studies have documented hypotension following midazolam sedation for endoscopy [31, 32] so the PMS system may be no worse than sedation methods already in use for these groups. The mean upper limit target concentration used by patients for this procedure was 2.7 (range ) lg.Ml )1, which is higher that that seen in previous studies looking at the use of the system for premedication [22] and sedation during regional anaesthesia [23].Brain anoxia however, studies of its use in ERCP [24] have required similar doses, demonstrating that, unsurprisingly, the requirement for sedation is higher during more stimulating procedures. The need to override patient control was high in this study compared with previous studies. In the cases of undersedated patients (n ¼ 3) this appeared to be secondary to patient difficulty in double pressing the handset activation button. Although the double press was originally included as an additional safety feature, it may be that during colonoscopy patients desire to be more sleepy and in these circumstances co-ordination of a double press appears to be too complicated and single press may be more appropriate.Brain anoxia the system is currently being evaluated in another study of patients having ERCP using single press activation. Four patients in the study became oversedated, underlining the importance of supervision of any sedated patient by an individual other than the colonoscopist. A major benefit of the PMS system however, is that in the event of oversedation, drug offset is very swift and sedation can be very quickly lightened or terminated using the override facility. The high incidence of oversedation does however, indicate that the current increment and lockout interval may not provide an adequate safety feedback loop and a reduction in handset TCI increments or an increase in the lockout interval should be evaluated to address this oversedation problem in future trials.Brain anoxia not surprisingly, impairment of psychomotor function was seen 15 min following discontinuation of the infusion of propofol with a mean total rise in CRT of 162 ms. This compares favourably to post sedation CRT after morphine and midazolam where hay [33] found a rise of 517 ms in CRT was still present even after 2 h. As an index for comparison, in a previous study, grant [34] found a 118 ms rise in CRT at the legal limit of alcohol for driving a car in the united kingdom (80 mg.100 ml )1 ). Clearly, the rise in CRT documented in this study with propofol constitutes a considerable improvement over conventional forms of sedation with implications of reduced patient recovery time and therefore possible cost savings.Brain anoxia patient satisfaction is an important consideration when sedation is provided for colonoscopic procedures. The questionnaire given to patients in this study confirms that the PMS system is popular. This may be related to an increased feeling of control as seen with patient controlled analgesia with the added benefit of being able to self administer increments during the procedure. Another important factor contributing to satisfaction is the lack of unpleasant recall. In endoscopic practice the trend has been towards using lower doses of benzodiazipine to improve safety, however, these lower doses may be associated with higher incidence of patient recall of up to 70% with doses of 35 lg.Kg )1 of midazolam [31].Brain anoxia reduced patient willingness to return for repeat examination due to unpleasant experience undermines the potential benefits of colonoscopy as a screening procedure illustrating the potential importance of ensuring high patient satisfaction. 130 Ó 2004 blackwell publishing ltd

5 anaesthesia, 2004, 59, pages L. Campbell et al. Æ propofol sedation for colonoscopy A disadvantage of the current system is the time taken for the patients to self-sedate. Although this was not formally measured the clinical impression was that min should be allowed for the process. As higher mean plasma levels of drug are clearly required by patients having colonoscopy, compared with sedation in nonstimulating situations, it may be possible to increase the initial target concentration above 1 lg.Ml )1, particularly in this group of relatively young fit patients.Brain anoxia another possible method of speeding up the self-sedation time is by using effect site targeting [35]. Systems developed in the future may be designed to target the estimated effect site (brain) concentration of propofol rather than the blood concentration therefore speeding onset of clinical drug action. In conclusion, the results of this study suggest that colonoscopy can be carried out using a PMS system. The system is well tolerated by patients and results in minimal recall and a high degree of patient satisfaction. The incidence of oversedation found in our study would suggest that modifications are required to the system. Further research is required prior to recommending its use during colonoscopy.Brain anoxia references 1 intercollegiate working party (chaired by the royal college of anaesthetists). Implementing and ensuring safe sedation practice for healthcare procedures in adults. (http://www.Rcoa. Ac.Uk/publications/index.Asp). 2 arrowsmith JB, gerstman BB. Fleischer DE, benjamin SB. Results from the american society for gastrointestinal endoscopy U.S. Food and drug administration collaborative study on complication rates and drug use during gastrointestinal endoscopy. Gastrointestinal endoscopy 1991, november 2001; 37: eckardt VF, kanzler G, schmitt T, eckardt AJ, bernhard G. Complications and adverse effects of colonoscopy with selective sedation. 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6 L. Campbell et al. Æ propofol sedation for colonoscopy anaesthesia, 2004, 59, pages marsh B, white M, morton N, kenny GN. Pharmacokinetic model driven infusion of propofol in children. British journal of anaesthesia 1991; 67: thompson AM, park KG, kerr F, munro A. Safety of fibreoptic endoscopy: analysis of cardiorespiratory events. British journal of surgery 1992; 79: hartke RH jr, gonzalez-rothi RJ, abbey NC. Midazolam-associated alterations in cardiorespiratory function during colonoscopy.Brain anoxia gastrointestinal endoscopy 1989; 35: herman LL, kurtz RC, mckee KJ, sun M, thaler HT, winawer SJ. Risk factors associated with vasovagal reactions during colonoscopy. Gastrointestinal endoscopy 1993; 39: ristikankare M, julkunen R, laitinen T et al. Effect of conscious sedation on cardiac autonomic regulation during colonoscopy. Scandinavian journal of gastroenterolology 2000; 35: froehlich F, schwizer W, thorens J, kohler M, gonvers JJ, fried M. Conscious sedation for gastroscopy: patient tolerance and cardiorespiratory parameters. Gastroenterology 1995; 108: patterson KW, casey PB, murrayjp, O boyle CA, cunningham AJ. Propofol sedation for outpatient upper gastrointestinal endoscopy: comparison with midazolam.Brain anoxia british journal of anaesthesia 1991; 67: hay A, black R, hooton G, porteous C, millar K, fletcher G. Psychomotor recovery after sedation for outpatient colonoscopy. Target controlled propofol infusion is significantly better than morphine and midazolam. European journal of anaesthesiology 2001; 18: grant SA, millar K, kenny GN. Blood alcohol concentration and psychomotor effects. British journal of anaesthesia 2000; 85: wakeling HG, zimmerman JB, howell S, glass PS. Targeting effect compartment or central compartment concentration of propofol: what predicts loss of consciousness? Anesthesiology 1999; 90: Ó 2004 blackwell publishing ltd