Total Intravenous Anesthesia

Evaluation and correlation of nociceptive response index and spectral entropy indices as monitors of nociception in anesthetized patients

Objectives

During anesthesia, the response to these stimuli depends on the balance between nociception and antinociception. Recently, various monitoring systems based on the variables derived from electroencephalography, plethysmography, autonomic tone, reflex pathways, and composite algorithms have been introduced for monitoring nociception. The main aim of our study was to evaluate and correlate the physiological variables which reflect the autonomic nervous system response to nociception, such as heart rate (HR), systolic blood pressure (SBP), perfusion index (PI), and nociceptive response index (NRI), with the spectral entropy indices response entropy (RE) and RE-state entropy (SE), which reflects electromyographic (EMG) activation as a response to pain.

Materials and Methods

This is a retrospective analysis of the data from a prospective study on the hypnotic and analgesic effects and the recovery profile of sevoflurane-based general anesthesia. Eighty-six patients undergoing single-agent sevoflurane anesthesia were recruited in the study. The study parameters, HR, SBP, SE, RE, RE-SE, PI, and NRI, were recorded at predefined time points before and after a standardized noxious stimulus. Correlation between the variables was carried out by applying the Pearson correlation equation for normal and the Spearman correlation equation for non-normally distributed data. Receiver operating characteristic (ROC) graphs were plotted, and the area under the curve was calculated to assess the diagnostic accuracy of post-stimulus NRI in detecting pain which was defined as RE-SE >10.

Results

There was a significant increase in the SBP, HR, NRI, RE, SE, and RE-SE and a considerable decrease in PI values during the post-noxious period compared to the pre-noxious period. There was no correlation between the absolute values of NRI and entropy indices at T2. However, among the reaction values, there was a weak correlation between the reaction values of NRI and RE (r = 0.30; P = 0.05). The area under the ROC curve for NRI to detect pain as defined by RE-SE >10 was 0.56.

Conclusion

During sevoflurane anesthesia, the application of noxious stimulus causes significant changes in variables reflecting sympathetic response and EMG activity. However, NRI failed to detect nociception, and there was only a weak correlation between the reaction values of NRI and RE-SE.

Comparison of the Surgical Pleth Index with autonomic nervous system modulation on cardiac activity during general anaesthesia: A randomised cross-over study

BACKGROUND

Surgical plethysmographic index (SPI) has been proposed as a tool to measure the nociception/antinociception balance during general anaesthesia. Untreated nociception may increase sympathetic tone, but the relationship between SPI and the autonomic nervous system (ANS) is poorly understood.

OBJECTIVE

We hypothesised that two different levels of SPI might be associated with differences in ANS modulation, measured by the frequency domain analysis of heart rate variability (HRV).

DESIGN

A randomised, cross-over group study, conducted between February and November 2009.

SETTING

University tertiary referral hospital in Milan, Italy.

PATIENTS

Forty-two adult patients undergoing scheduled laparoscopic abdominal surgery.

INTERVENTIONS

ECG, noninvasive arterial blood pressure and SPI were recorded during balanced general anaesthesia with inhaled sevoflurane and intravenous remifentanil. After pneumoperitoneum induction, the remifentanil infusion rate was set to obtain two different levels of SPI (>50, HI-SPI, and <50, LO-SPI) for each patient.

MAIN OUTCOME MEASURES

Arterial pressure, heart rate (HR), low-frequency and high-frequency spectral components, the low frequency/high frequency ratio (measure of sympathovagal balance) and whole power spectrum density of HRV were measured at the two different levels of SPI.

RESULTS

Thirty-nine patients were included in the final analysis. During LO-SPI, HR and systolic and mean blood pressures were significantly lower than HI-SPI. The median low frequency/high frequency ratio was reduced during LO-SPI [1.29 interquartile range (IQR) 0.66 to 2.05) vs. 2.36 (1.30 to 3.62), P = 0.008]. The sensitivity analysis revealed a significant correlation between SPI changes and changes of all ANS indices, arterial pressure and HR, with a slightly better correlation for low frequency/high frequency (Spearman ρ = 0.70, IQR 0.484 to 0.834, P < 0.001).

CONCLUSION

In the context of a balanced general anaesthesia in healthy patients undergoing laparoscopic abdominal surgery, ANS modulation seems to correlate with changes in SPI. Further studies are warranted to assess whether this may reflect a change in nociception/antinociception balance or a pharmacodynamic effect of remifentanil.

Evaluation of remifentanil anesthesia for off-pump coronary artery bypass grafting surgery using heart rate variability

Heart rate variability (HRV) was used in the present study to evaluate a target-controlled approach compared with a constant-rate infusion for remifentanil anesthesia during off-pump coronary artery bypass grafting (OP-CABG) surgery. A total of 65 patients with American Society of Anesthesiologists (ASA) physical status II or III, who were aged 60–85 years and scheduled for OP-CABG, were selected for the study. All patients were administered an intramuscular premedication of 10 mg morphine and 0.3 mg scopolamine. In group I, remifentanil was infused using a target-controlled approach at 1.5–5.0 ng/ml, and in group II, remifentanil was infused at a constant-rate of 0.05–1.0 μg/kg/min and at additional single increments of 1 μg/kg when appropriate. The heart rate and other hemodynamic monitoring indices of the patients, including the mean arterial pressure, central venous pressure, pulmonary artery pressure and pulmonary capillary wedge pressure, were monitored at various time points, including prior to induction (T₀), at extubation (performed intraoperatively; T₇) and at 24 h post-surgery. The HRV indices, including total power (TP), low frequency (LF) and the LF/high frequency (HF) ratio of power (LF/HF), were reduced following induction at T₀ and remained low at 24 h post-surgery. At T₅ (right coronary or left circumflex artery anastomosis) and T₇ (tracheal extubation), all the HRV indices, with the exception of the HF power, were significantly increased (P<0.05). Additionally, the TP, LF and LF/HF values in group II were higher at T₅ compared with those in group I (P<0.05). Remifentanil target-controlled infusion is superior to constant-rate infusion in suppressing the stress response during OP-CABG, maintaining the balance of the cardiac autonomic nervous system and promoting the recovery of the autonomic function following surgery.

Changes in a surgical stress index in response to standardized pain stimuli during propofol–remifentanil infusion

BACKGROUND

The surgical stress index (SSI) is based on a sum of the normalized pulse beat interval (PBI) and the pulse wave amplitude (PPGA) time series of the photoplethysmography. As a measure of the nociception-anti-nociception balance in response to a standardized pain stimulus, SSI was compared with EEG changes in state and response entropy (SE and RE), PPGA, and heart rate (HR) during various targeted pseudo-steady-state concentrations of propofol and remifentanil.

METHODS

Forty ASA I patients were allocated to one of the four groups to receive a remifentanil step-up/-down effect-compartment target-controlled infusion (Ce(remi)) of 0, 2, 6, 2, 0 ng ml(-1), or 6, 2, 0, 2, 6 ng ml(-1), and an effect-compartment target-controlled propofol infusion (Ce(prop)) to keep the SE between 30 and 50 or 15 and 30, respectively. At each steady-state Ce(remi), maximum change in SSI, SE, RE, PPGA, and HR after a noxious stimulus was compared with the baseline value. A correlation and prediction probability (P(K)) with Ce(prop) and Ce(remi) was measured.

RESULTS

Static and dynamic values of SSI correlated to Ce(remi) better than SE, RE, HR, and PPGA. SSI was independent of Ce(prop), in contrast to SE and RE. The P(K) for Ce(remi) both before and during a noxious stimulus was better with SSI.

CONCLUSIONS

SSI appeared to be a better measure of nociception-anti-nociception balance than SE, RE, HR, or PPGA.

Use of cerebral monitoring during anaesthesia: effect on recovery profile

This review article examines the effect of cerebral monitoring using an EEG-based device [i.e. bispectral index (BIS), patient state analyzer (PSA), auditory evoked potential (AEP), cerebral state index (CSI), or entropy] on titration of anaesthetic, analgesic and cardiovascular drugs during surgery. In addition, articles discussing the effects of these cerebral monitoring devices on recovery profiles following general anaesthesia, postoperative side effects, and anaesthetic costs are reviewed.

The effects of remifentanil and alfentanil-based total intravenous anesthesia (TIVA) on the endocrine response to abdominal hysterectomy

STUDY OBJECTIVE

To compare the effects of remifentanil with alfentanil as a part of total intravenous anesthesia (TIVA) on plasma concentrations of cortisol, insulin, and glucose, and hemodynamic responses in patients undergoing abdominal hysterectomy.

DESIGN

Randomized, double-blind study.

SETTING

University hospital.

PATIENTS

24 ASA physical status I female patients scheduled for abdominal hysterectomy.

INTERVENTIONS

Premedicated patients were randomly allocated to receive either remifentanil-propofol (Group R) or alfentanil-propofol (Group A). The loading dose of the study drug was administered over 60 seconds (remifentanil l microg kg(-l) or alfentanil 10 microg kg(-l)) followed by a continuous infusion (remifentanil 0.2 microg kg(-l) min(-l) or alfentanil 0.5 microg kg(-l) min(-l)). In both groups, propofol was administered until loss of consciousness and maintained with a propofol infusion rate of 100 microg kg(-l) min(-l). After induction of anesthesia, all patients were manually ventilated by mask with O2-air mixture for 20 minutes. Then rocuronium 0.6 mg kg(-l) was given for tracheal intubation.

MEASUREMENTS

Mean arterial pressure (MAP) and heart rate (HR) were recorded. Plasma concentrations of cortisol, insulin, and glucose were measured during anesthesia and in the recovery room.

MAIN RESULTS

In Group R, MAP and HR were lower after tracheal intubation and skin incision than in Group A (p < 0.05). Plasma cortisol concentrations decreased from baseline values at 20 minutes after induction, after tracheal intubation, and skin incision in Group R (p < 0.001). Plasma concentrations of cortisol and glucose increased from baseline values at 30 minutes after skin incision and continued to increase in both groups (p = 0.001). Plasma concentrations of cortisol, insulin, and glucose did not differ between groups at all sampling times.

CONCLUSION

Remifentanil provided better hemodynamic stability than alfentanil during anesthesia and surgery. However, both remifentanil and alfentanil had similar effects on the stress endocrine response to abdominal hysterectomy.

The Effect of Intraoperative Use of Esmolol and Nicardipine on Recovery After Ambulatory Surgery

There is controversy regarding the optimal technique for maintaining hemodynamic stability during anesthesia. We designed this prospective, randomized, double-blinded study to test the hypothesis that the technique used for maintaining hemodynamic stability during general anesthesia can influence recovery after ambulatory surgery. Forty-five healthy consenting women undergoing gynecologic laparoscopy procedures were randomly assigned to 1 of 3 treatment groups: Group 1 (control, n = 15) received normal saline 5 mL and 1 mL, followed by a saline infusion at a rate of 0.005 mL x kg(-1) x min(-1); Group 2 (n = 15) received esmolol 50 mg and saline 1 mL, followed by an esmolol infusion 5 microg x kg(-1) x min(-1); and Group 3 (n = 15) received esmolol 50 mg and nicardipine 1 mg, followed by an esmolol infusion 5 microg x kg(-1) x min(-1). The study drugs were administered after the induction of anesthesia with fentanyl 1.5 microg/kg, and propofol 2 mg/kg I.V. Tracheal intubation was facilitated with vecuronium 0.12 mg/kg I.V. Anesthesia was initially maintained with desflurane 2% end-tidal and N(2)O 67% in oxygen in all 3 groups. During surgery, the mean arterial blood pressure (MAP) was maintained within +/-15% of the baseline value by varying the study drug infusion rate and the inspired concentration of desflurane. In addition to MAP and heart rate values, electroencephalogram bispectral index values were recorded throughout the perioperative period. Recovery times and postoperative side effects were assessed. Compared with the control group, adjunctive use of esmolol and nicardipine attenuated the increase in heart rate (in Group 2) and MAP (in Group 3) after tracheal intubation. Furthermore, the use of an esmolol infusion as an adjunct to desflurane to control the acute autonomic responses during the maintenance period significantly decreased emergence times (4 +/- 2 versus 7 +/- 4 min), decreased the need for postoperative opioid analgesics (43% versus 80%), and reduced the time to discharge (209 +/- 89 versus 269 +/- 100 min). We conclude that the adjunctive use of esmolol alone or in combination with nicardipine during the induction of anesthesia reduced the hemodynamic response to tracheal intubation. Furthermore, use of an esmolol infusion as an adjuvant to desflurane-N(2)O anesthesia for controlling the acute hemodynamic responses during the maintenance period improved the recovery profile after outpatient laparoscopic surgery.

IMPLICATIONS

The adjunctive use of the beta-adrenergic blocker esmolol to control the acute sympathetic responses during desflurane-based anesthesia provided a more rapid awakening from anesthesia, reduced the postoperative opioid analgesic requirement, and decreased the time to discharge home after ambulatory laparoscopic surgery.

Early recovery after remifentanil-pronounced compared with propofol-pronounced total intravenous anaesthesia for short painful procedures †

BACKGROUND

We compared recovery from high-dose propofol/low-dose remifentanil ('propofol-pronounced') compared with high-dose remifentanil/low-dose propofol ('remifentanil-pronounced') anaesthesia.

METHODS

Adult patients having panendoscopy, microlaryngoscopy, or tonsillectomy were randomly assigned to receive either propofol-pronounced (propofol 100 microg x kg(-1) min(-1); remifentanil 0.15 microg x kg(-1) min(-1)) or remifentanil-pronounced (propofol 50 microg x kg(-1) min(-1); remifentanil 0.45 microg x kg(-1) min(-1)) anaesthesia. In both groups, the procedure was started with remifentanil 0.4 microg x kg(-1), propofol 2 mg x kg(-1), and mivacurium 0.2 mg x kg(-1). Cardiovascular measurements and EEG bispectral index (BIS) were recorded. To maintain comparable anaesthetic depth, additional propofol (0.5 mg x kg(-1)) was given if BIS values were greater than 55 and remifentanil (0.4 microg x kg(-1)) if heart rate or arterial pressure was greater than 110% of pre-anaesthetic values.

RESULTS

Patient and surgical characteristics, cardiovascular measurements, and BIS values were similar in both groups. There were no differences in recovery times between the groups (time to extubation: 12.7 (4.5) vs 12.0 (3.6) min, readiness for transfer to the recovery ward: 14.4 (4.4) vs. 13.7 (3.6) min, mean (SD)).

CONCLUSIONS

In patients having short painful surgery, less propofol does not give faster recovery as long as the same anaesthetic level (as indicated by BIS and clinical signs) is maintained by more remifentanil. However, recovery times were less variable following remifentanil-pronounced anaesthesia suggesting a more predictable recovery.

The use of esmolol as an alternative to remifentanil during desflurane anesthesia for fast-track outpatient gynecologic laparoscopic surgery

We compared esmolol and remifentanil infusions with respect to their effect on intraoperative hemodynamic stability and early recovery after outpatient laparoscopic surgery when administered as IV adjuvants during desflurane anesthesia. After premedication with midazolam 2 mg IV, anesthesia was induced with propofol 2 mg. kg(-1) IV in combination with either esmolol 1 mg. kg(-1) IV (n = 27) or remifentanil 1 microg. kg(-1) IV (n = 26) and succinylcholine 1 mg. kg(-1) IV according to a randomized, double-blinded protocol. Anesthesia was initially maintained with desflurane 2.5% (subsequently titrated to maintain an electroencephalogram-bispectral index value of 60) and nitrous oxide 65% in oxygen. Before skin incision, an infusion of either esmolol (5 microg. kg(-1). min(-1)) or remifentanil (0.05 microg. kg(-1). min(-1)) was started and titrated to maintain the heart rate within 25% of the baseline value. Mivacurium, 0.04 mg/kg IV, bolus doses were administered to maintain a stable peak inspiratory pressure. Esmolol (12.8 +/- 13.1 microg. kg(-1). min(-1)) and remifentanil (0.04 +/- 0.02 microg. kg(-1). min(-1)) infusions were equally effective in maintaining a stable heart rate during these laparoscopic procedures. Although the mivacurium requirement was larger in the Esmolol group (7 +/- 5 vs 3 +/- 4 mg), the Esmolol group reported a smaller incidence of postoperative nausea and vomiting (4% vs 35%). Both drugs were associated with frequent "postanesthesia care unit bypass" rates (78-81%), short times to "home readiness" (119-120 min), excellent patient satisfaction (81-85%), and rapid resumption of normal activities (2.6-3.2 d). Fast-tracked patients were ready for discharge home significantly earlier (112 +/- 46 vs 151 +/- 50 min). We concluded that esmolol infusion is an acceptable alternative to remifentanil infusion for maintaining hemodynamic stability during desflurane-based fast-track anesthesia for outpatient gynecologic laparoscopic surgery.

The effect of fresh gas flow and anesthetic technique on the ability to control acute hemodynamic responses during surgery

We evaluated the effect of the fresh gas flow (FGF) rate and the anesthetic technique on the ability to control the acute hyperdynamic response to a specific surgical stimulus during surgery in 90 consenting ASA physical status I-III patients undergoing lower abdominal procedures. After the administration of midazolam 2 mg IV, anesthesia was induced in all patients with propofol 1.5 mg/kg IV and fentanyl 1 microg/kg IV and was initially maintained with desflurane or isoflurane, 0.7 minimum alveolar anesthetic concentration, at total FGF rates of either 1 or 3 L/min. In response to the surgical stimulation of skin incision and retropubic dissection, an increase in mean arterial pressure (MAP) >20% above the preincision baseline MAP value provoked a stepwise increase in the inspired concentration of the volatile anesthetic or the IV administration of a variable-rate infusion of esmolol. At both FGF rates, the acute hemodynamic response to surgical stimulation was more efficiently treated by increasing the inspired concentration of desflurane than isoflurane. At 1 L/min, the average time to control the increase in MAP was significantly shorter with desflurane (17+/-12 min) compared with isoflurane (29+/-16 min), with 60% of the patients in the isoflurane group requiring rescue therapy. When an esmolol infusion was used to control the increase in MAP, supplementation with fentanyl was required in 40% and 53% of patients anesthetized with desflurane and isoflurane, respectively. In conclusion, desflurane provided more rapid and reliable control of acute hemodynamic responses to surgical stimulation than isoflurane or esmolol when the volatile anesthetics were administered at low FGF rates.

IMPLICATIONS

At low fresh gas flow rates (1 L/min), desflurane more successfully and rapidly controlled the acute hemodynamic responses to painful surgical stimuli than isoflurane.

Effect of nitrous oxide on middle ear pressure: a comparison between inhalational anaesthesia with nitrous oxide and TIVA

We have investigated the effect of nitrous oxide on the middle ear pressure, comparing inhalational anaesthesia with nitrous oxide and halothane and total intravenous anaesthesia with propofol-alfentanil. Fifty patients with normal healthy ears were divided into two groups. In one group (n = 25), anaesthesia was induced with thiopentone 6 mg kg-1, and maintained with halothane 1% and nitrous oxide 66% in oxygen. In the other group (n = 25), anaesthesia was induced with alfentanil 25 micrograms kg-1 and propofol 2 mg kg-1, and maintained with an infusion of alfentanil 10 micrograms kg-1 min-1 for the first 10 min and then with 0.5 microgram kg-1 min-1 and with propofol 10 mg kg-1 h-1 for the first 10 min, 8 mg kg-1 h-1 for the following 10 min and 6 mg kg-1 h-1 thereafter. Patients were ventilated with an oxygen-air mixture (F1O2 = 0.33). Middle ear pressures were measured during the pre-, intra- and post-anaesthetic period in both ears. A progressive rise was observed (P < 0.05) in the first group, whereas values were within the normal limits clinically and there was no statistically significant change in those receiving total intravenous anaesthesia during the intra-anaesthetic period. The time to reach peak pressure with inhalational anaesthesia was 60 min (181.5 mmH2O) and to return to normal was 30 min (49.5 mmH2O) after cessation of nitrous oxide administration. The incidence of nausea and vomiting was less in the patients not receiving nitrous oxide.

Haemodynamic instability and myocardial ischaemia during carotid endarterectomy: a comparison of propofol and isoflurane

The purpose of this study was to compare two anaesthetic protocols for haemodynamic instability (heart rate (HR) or mean arterial pressure (MAP) < 80 or > 120% of ward baseline values) measured at one-minute intervals during carotid endarterectomy (CEA). One group received propofol/alfentanil (Group Prop; n = 14) and the other isoflurane/alfentanil (Group Iso; n = 13). Periods of haemodynamic instability were correlated to episodes of myocardial ischaemia as assessed by Holter monitoring (begun the evening before surgery and ceasing the morning of the first postoperative day). In Group Prop, anaesthesia was induced with alfentanil 30 micrograms.kg-1 i.v., propofol up to 1.5 mg.kg-1 and vecuronium 0.15 mg.kg-1, and maintained with infusions of propofol at 3-12 mg.kg-1.hr-1 and alfentanil at 30 micrograms.kg-1.hr-1. In Group Iso, anaesthesia was induced with alfentanil and vecuronium as above, thiopentone up to 4 mg.kg-1 and maintained with isoflurane and alfentanil infusion. Phenylephrine was infused to support MAP at 110 +/- 10% of ward values during cross-clamp of the internal carotid artery (ICA) in both groups. Emergence hypertension and/or tachycardia was treated with labetalol, diazoxide or propranolol. Myocardial ischaemia was defined as ST-segment depression of > or = 1 mm (60 msec past the J-point) persisting for > or = one minute. For the entire anaesthetic course (induction to post-emergence), there was no difference between groups for either duration or magnitude outside the < 80 or > 120% range for HR or MAP. However, when the period of emergence from anaesthesia (reversal of neuromuscular blockade to post-extubation) was assessed, more patients were hypertensive (P = 0.004) and required vasodilator therapy in Group Iso (10/13 vs 5/14; P = 0.038 Fisher's Exact Test). The mean dose of labetalol was greater in Group Iso (P = 0.035). No patient demonstrated myocardial ischaemia during ICA cross-clamp. On emergence, 6/13 patients in Group Iso demonstrated myocardial ischaemia compared with 1/14 in Group Prop (P = 0.029). Therefore, supporting the blood pressure with phenylephrine, during the period of ICA cross-clamping, appears to be safe as we did not observe any myocardial ischaemia at this time. During emergence from anaesthesia, haemodynamic instability was associated with myocardial ischaemia. Under these specific experimental conditions, with emergence, hypertension and myocardial ischaemia were more prevalent with more frequent pharmacological interventions in patients receiving isoflurane.