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*Département Bloc-Anesthésie, Institut Mutualiste Montsouris, Paris, France; and
Département dAnesthésie-Réanimation, Hôpital Pitié-Salpétrière, Paris, France
Address correspondence to Stéphane Mouren, MD, PhD, Département Bloc-Anesthésie, Institut Mutualiste Montsouris, 42 Boulevard Jourdan, 75674 Paris Cedex 14, France.
| Abstract |
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IMPLICATIONS:Beat-to-beat recordings of heart rate and blood pressure in patients undergoing carotid surgery revealed that hemodynamic stability was similar with remifentanil or sufentanil anesthesia both during and after surgery. Remifentanil was more effective in limiting the increase in blood pressure associated with intubation without increasing the blood pressure-lowering effect of induction or the blood pressure response to recovery.
| Introduction |
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| Methods |
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One hour before surgery, all patients were premedicated with oral midazolam 5 mg and their usual cardiovascular medication, except angiotensin-converting enzyme inhibitors. Monitoring included a five-lead ECG with ST segment trends on leads V4, V5, and II; invasive arterial BP (TRAM, Marquette Electronics, Inc., Loves Park, IL); and pulse oxygen saturation (SpO2), end-tidal CO2, and inspiratory and end-tidal anesthetic concentrations.).
After placement of an IV catheter and 10 mL/kg crystalloid infusion, the patients received either an initial loading dose of 1 µg/kg of remifentanil in 30 s followed by a continuous infusion of 0.5 µg · kg-1 · min-1 or 0.5 µg/kg sufentanil in 30 s, with an additional bolus, if required. Propofol was administered until loss of consciousness. After a 0.5 mg/kg atracurium infusion and tracheal intubation, the remifentanil infusion rate was changed or a bolus of sufentanil was given as required by the surgical stress. Ventilation (10 mL/kg, 12/min) was controlled to maintain an ETCO2 between 30 and 35 mm Hg. Isoflurane was administered for maintenance of anesthesia with a fresh gas flow of 2 L/min (50% N2O/50% oxygen). As usual in the vascular surgery unit, no specialized monitoring for cerebral ischemia or arterial shunting was used during the study.
During the procedure, the anesthesiologist was required to maintain SBP and HR within ±30% of baseline values. In both groups, fluid administration and vasoconstrictor (ephedrine or phenylephrine) administration were based on hemodynamic monitoring. In the two groups, 2 g propacetamol (a nonopioid analgesic) was infused IV 3045 min before the end of surgery. In addition, patients in the Remifentanil group received 0.1 mg/kg morphine IV at the same time. Isoflurane was stopped at the beginning of skin closure. Remifentanil infusion was stopped at the last surgical suture. All patients were tracheally extubated in the surgical room.
All the patients were admitted after surgery to the recovery room for at least 2 h. Postoperative care, including hemodynamic monitoring and treatments and standardized nursing care, was under the supervision of the attending anesthesiologist of the recovery room. The pain score, by using a visual analog scale (VAS) (6), and the sedation score, by using the Ramsay scale, were evaluated every 10 min after extubation for 40 min and at 1, 1.5, and 2 h after extubation. Morphine titration was used to obtain a VAS value of
30 mm before discharge from the recovery room.
A 12-lead ECG recording was performed at the end of the surgery and compared with the preoperative ECG. ECG was repeated daily on the three postoperative days. Troponin Ic levels were measured at the induction, 1 h after surgery, and on the three postoperative days. These measurements were repeated if any abnormal value was detected.
The SBP and HR signals obtained from the monitor (TRAM) were acquired at 200 samples per second and stored on a personal computer hard drive by using an analog-to-digital convertor data acquisition system (MP30; Biopac, Santa Barbara, CA). After reviewing for removal of artifacts and arterial catheter flushings, each complete arterial pressure tracing was scanned for a beat-to-beat analysis. Values of SBP and HR were stored in Excel 5.0 (Microsoft, Redmond, WA) files for each patient. All Excel files were scanned again to determine whether the hemodynamic abnormalities were artifacts or real events. The positive and negative CVs of SBP and HR [(SD of the mean/mean) x 100] were calculated for the period lasting from the induction of anesthesia to 5 min after extubation and for the recovery period until discharge. In addition, the highest and the lowest SBP and the highest and lowest HR of these two periods were recorded.
The total volume of fluid infusion, the time spent at each isoflurane concentration, and the total doses of anesthetic drugs, ephedrine, phenylephrine, ß-adrenergic blockers, and calcium channel blockers were recorded for both groups. The same analysis was performed for the period lasting from induction to 5 min after intubation (inductionintubation period) and for the period lasting from 5 min before extubation to 5 min after extubation (extubation). In addition, the highest and the lowest SBP and the highest and lowest HR were recorded for each phase.
Hemodynamic events were defined as 1) hypotension (i.e., an SBP value less than 80 mm Hg or <30% of baseline value) lasting more than 1 min; 2) hypertension lasting more than 1 min (i.e., an SBP value more than 170 mm Hg or >30% of baseline value); 3) tachycardia lasting more than 1 min (i.e., an HR value more than 90 bpm or >30% of baseline value); and 4) bradycardia lasting more than 1 min (i.e., an HR value less than 40 bpm or <30% of baseline value). The total duration and the number of patients experiencing these events were calculated for each patient of both groups.
Recovery times were recorded from discontinuation of isoflurane to spontaneous ventilation, eye opening (assessed every minute), and extubation. Adverse events were defined as the appearance of transient ischemic attack, nonreversible neurologic deficits and myocardial infarction, death, and postoperative nausea and vomiting.
In a preliminary study performed during CE, we found a mean value for CV of SBP of 15.5% ± 4% with sufentanil/isoflurane anesthesia. Thus, we calculated that 52 patients would be necessary for the assessment of a 20% reduction of the mean of CV of SBP with
= 0.05 and a power of 80%. The Kolmogorov-Smirnov test was used to characterize the distribution of each continuous numeric variable. Intergroup comparisons for the CV of SBP and HR, total doses of drugs used during or after surgery, and the duration of anesthesia and hemodynamic events used the two-sample Students t-test when the distribution of the variables was normal and the Mann-Whitney U-test when the distribution of the variables was not normal. Intergroup comparison for ordinal variables used the
2 test and Fishers exact test for 2 x 2 tables. A two-way analysis of variance was used to compare time spent at each end-tidal isoflurane concentration, VAS, and Ramsay score. Data are expressed as mean ± SD or median (25th75th percentiles). For all tests, a two-sided P value <0.05 was considered significant.
| Results |
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During the recovery period, the mean values of SBP and the positive and negative CVs of SBP and HR were not significantly different between groups (Tables 1 and 6). The total duration of episodes of hypertension and tachycardia and the highest value and the lowest value of SBP and HR were similar in both groups (Table 6). No patient experienced bradycardia or hypotension. No significant difference was found between groups in the total doses of esmolol or nicardipine.
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| Discussion |
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To accurately evaluate BP stability, we used a continuous beat-to-beat computerized recording of BP. This contrasts with other studies performed in cardiac and noncardiac surgery, in which the evaluation of BP stability was often based on arterial BPs obtained in steady state, on intraoperative highest or lowest BPs, or on arterial BPs more or less than predefined values during stressful periods such as induction, intubation, skin incision, or extubation (811). The durations of these periods are short compared with the total duration of the anesthesia (see Tables 4 and 5). Consequently, a main part of the anesthesia is not considered in the analysis. In most studies, the failure to record BP continuously is a significant limitation because the absolute amount of change in BP that could have occurred during intermittent measurement intervals would not have been accurately detected. Thus, more potent tools are required for evaluation of hemodynamic stability during anesthesia. In a multicenter study, a 96-hour monitoring of SBP and HR every 10 seconds was used to evaluate the effects of the
2-adrenoceptor agonist mivazerol on hemodynamic stability and myocardial ischemia (12). A change in median mean arterial BP of at least 6% from a two-minute interval to the next in more than 30% of the intervals has been proposed as an index of hemodynamic stability before cardiopulmonary bypass (13). However, the latter approach is not validated in noncardiac surgery. Compared with handwritten generated records, the computerized records increase the amount of data collected (14), reduce interobserver disagreement (13,15), and avoid unobserved readings or faulty reconstructions from memory or bias in favor of less controversial values (16). Our comparison of the two anesthetic techniques considered the variations of SBP and HR during the whole anesthesia period and during the stressful periods such as the induction/intubation, extubation, and recovery phases, which are characterized by the largest variations in SBP and HR. We selected a beat-to-beat analysis instead of an analysis performed at standardized periods (e.g., every 15 seconds) to reduce the risk of missing short episodes of hyper- or hypotension (17). When using a beat-to-beat recording system, the number of valid data points may be increased in patients with faster HRs, inducing a potential bias. This did not occur in this study because the mean HRs in the two study groups were similar in each period of analysis.
A global analysis of SBP and HR variations showed that the positive and negative CVs of SBP and HR were not different in the two groups during anesthesia; this suggests a similar intraoperative hemodynamic stability with remifentanil or sufentanil anesthesia during CE. A smaller dose of propofol was used for induction in the Remifentanil group. More patients in the Sufentanil group underwent at least one episode of bradycardia, whereas the incidence of hypertension, hypotension, and tachycardia was similar in the two groups. During the induction/intubation phase, the hemodynamic stability assessed by the CVs of SBP and HR was similar with remifentanil or sufentanil anesthesia. However, we found a higher peak value of SBP in the Sufentanil group, whereas the lowest value of SBP was similar in the two groups. Such results did not influence the global CV of SBP because hypertension during intubation lasted only three to four minutes, i.e., 2%3% of the total duration of the anesthesia (Table 5). Nevertheless, this confirms that remifentanil infusion during this period was more potent for limiting the increase in SBP during laryngoscopy and intubation. It is important to note that this beneficial effect was not associated with an increase in the BP-reducing effect of induction; this contrasts with the findings of previous reports (10,18). Our study protocol, which imposed slow infusion of remifentanil and propofol administration based on loss of consciousness, probably played a role in this result (19).
In patients undergoing CE, a remifentanil/volatile anesthetic technique provided rapid awakening and an early opportunity for neurologic examination (4).Our results indicate that these beneficial effects can be obtained without any increased risk for intraoperative hypotension or for postoperative hypertension or tachycardia. These results are of particular interest in patients undergoing CE, which carries the risk of substantial complications related to intra- and postoperative hemodynamic disturbances.
For our study, which investigated the use of a short-acting opioid for CE to have meaningful clinical implications, our control group followed a course that conformed to routine clinical practice (20). Because the level of analgesia may influence the stability of anesthesia, the equipotency of our opioid regimen is a major determinant of the hemodynamic stability during the maintenance of anesthesia. By using STANPUMP software (Bovill model), we ensured that our opioid regimens resulted in equipotent concentrations of sufentanil and remifentanil during maintenance. The remifentanil concentration at steady-state reached 17 ng/mL both in plasma and at the effect site, and sufentanil concentrations were close to 1.60 ng/mL in plasma and 1.80 ng/mL at the effect site. Assuming a ratio in sufentanil/remifentanil potency of 10 (21), the opioid infusions resulted in grossly equipotent concentrations. However, isoflurane was used at smaller concentrations in the Remifentanil group (Fig. 1). Yet a similar hemodynamic pattern was obtained at equipotent concentrations of sufentanil and remifentanil, with a smaller isoflurane concentration in the Remifentanil group. Because opioid concentrations were grossly equipotent, these results could be caused by the mode of administration (continuous versus bolus) or to the pharmacodynamic properties of remifentanils interacting with isoflurane (21).
We did not find any differences in the CVs of SBP or HR between the two groups during the recovery period. The similar hemodynamic response to recovery in both groups shows that the intraoperative stability noted with remifentanil is not associated with an increased circulatory response to recovery, which might have resulted from its pharmacokinetic properties. It should be noted that with IV administration of propacetamol and morphine before skin closure, no difference was found in the global hemodynamic stability or the requirement of ß-adrenergic blockers or calcium channel blockers between the two groups during extubation and the recovery period, because all patients in this study received antihypertensive treatments. The pain level was slightly but significantly increased in the Remifentanil group during the recovery period but reached a similar level in the two groups at the time of discharge from the recovery room (22 and 25 mm in the Remifentanil and Sufentanil groups, respectively). However, these different levels of postoperative pain did not result in more marked postoperative hemodynamic changes in the Remifentanil group.
In conclusion, a similar global hemodynamic stability was observed during and after CE in patients receiving remifentanil or sufentanil during surgery. Remifentanil was more effective in limiting the increase in BP associated with intubation without increasing the BP-reducing effect of induction. The circulatory response to recovery was not increased in patients who received intraoperative remifentanil. On the basis of these results and the pharmacokinetic properties of remifentanil, this short-acting opioid seems to be a useful alternative to sufentanil in patients undergoing carotid surgery.
| References |
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2-adrenoceptor agonist mivazerol on hemodynamic stability and myocardial ischemiaMcSPIEurope Research Group. Anesthesiology 1997; 86: 34663.[ISI][Medline]
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