Prediction of hemodynamic reactivity during total intravenous anesthesia for suspension laryngoscopy using Analgesia/Nociception Index (ANI): a prospective observational study.

BACKGROUND: The Analgesia/Nociception Index (ANI), a 0-100 non-invasive index calculated from heart rate variability, reflects the analgesia/nociception balance during general anesthesia. The principal objective of this study was to evaluate the performance of ANI to predict hemodynamic reactivity during suspension laryngoscopy. The secondary objectives were to investigate the performances of ANI and bispectral index (BIS) to assess sedation and of BIS to predict hemodynamic reactivity during the procedure. METHODS: Fifty patients undergoing suspension laryngoscopy with total intravenous anesthesia using propofol and remifentanil were analysed in this prospective observational study. The ANI, BIS and Observer's Assessment of Alertness/Sedation (OAA/S) scale were measured at predefined time-points during the procedure. Receiver-operating characteristic (ROC) curves were built to evaluate the performance of ANI and BIS to predict hemodynamic reactivity (increase by more than 20% of heart rate and/or systolic blood pressure within 5 min) and assess sedation (OAA/S ≤ 2) during the procedure. RESULTS: For the prediction of hemodynamic reactivity, better performance was observed with ANI in comparison to BIS (ROC curve AUC [95% CI] = 0.88 [0.83-0.92] vs. 0.73 [0.66-0.79], P < 0.05). The sensitivity and specificity of ANI ≤ 55 to predict hemodynamic reactivity within 5 min were 88% and 83%, respectively. For the assessment of sedation, a better performance was observed with BIS in comparison to ANI (ROC curve AUC [95% CI] = 0.91 [0.86-0.94] vs. 0.68 [0.61-0.74], respectively, P < 0.05). CONCLUSION: ANI exhibits good performance for the prediction of hemodynamic reactivity and BIS exhibits good performance for the assessment of sedation during suspension laryngoscopy with propofol/remifentanil total intravenous anesthesia.

Prediction of immediate postoperative pain using the analgesia/nociception index: a prospective observational study.

BACKGROUND: The analgesia/nociception index (ANI) is derived from heart rate variability, ranging from 0 (maximal nociception) to 100 (maximal analgesia), to reflect the analgesia/nociception balance during general anaesthesia. This should be correlated with immediate postoperative pain in the post-anaesthesia care unit (PACU). The aim of this study was to evaluate the performance of ANI measured at arousal from general anaesthesia to predict immediate postoperative pain on arrival in PACU. METHODS: Two hundred patients undergoing ear, nose, and throat or lower limb orthopaedic surgery with general anaesthesia using an inhalational agent and remifentanil were included in this prospective observational study. The ANI was measured immediately before tracheal extubation and pain intensity was assessed within 10 min of arrival in PACU using a 0-10 numerical rating scale (NRS). The relationship between ANI and NRS was assessed using linear regression. A receiver-operating characteristic (ROC) curve was used to evaluate the performance of ANI to predict NRS>3. RESULTS: A negative linear relationship was observed between ANI immediately before extubation and NRS on arrival in PACU. Using a threshold of <50, the sensitivity and specificity of ANI to discriminate between patients with NRS≤3 and NRS>3 were both 86% with 92% negative predictive value, corresponding to an area under the ROC curve of 0.89. CONCLUSIONS: The measurement of ANI immediately before extubation after inhalation-remifentanil anaesthesia was significantly associated with pain intensity on arrival in PACU. The performance of ANI for the prediction of immediate postoperative pain is good and may assist physicians in optimizing acute pain management. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov NCT01796249.

Prospective observational study of the non-invasive assessment of immediate postoperative pain using the analgesia/nociception index (ANI).

BACKGROUND: The analgesia/nociception index (ANI), a 0-100 non-invasive index calculated from heart rate variability, reflects the analgesia/nociception balance during general anaesthesia. The aim of this study was to evaluate the ANI in the assessment of immediate postoperative pain in adult patients undergoing general anaesthesia. METHODS: Two-hundred patients undergoing scheduled surgery or endoscopy with general anaesthesia were included in this prospective observational study. Pain intensity was assessed using a 0-10 numerical rating scale (NRS) after arousal from general anaesthesia. Receiver-operating characteristic (ROC) curves were built to assess the performance of ANI to detect patients with NRS>3 and NRS ≥ 7 on arrival in the postoperative care unit. RESULTS: A negative linear relationship was observed between ANI and NRS (ANI=-5.2 × NRS+77.9, r(2)=0.41, P<0.05). At the threshold of 57, the sensitivity and specificity of ANI to detect patients with NRS>3 were 78 and 80%, respectively, with a negative predictive value of 88%, corresponding to an area under the ROC curve (AUC) of 0.86. At the threshold of 48, the sensitivity and specificity of ANI to detect NRS ≥ 7 were 92 and 82%, respectively, with a negative predictive value of 99%, corresponding to a ROC curve AUC of 0.91. CONCLUSIONS: A measurement of ANI during the immediate postoperative period is significantly correlated with pain intensity. The measurement of ANI appears to be a simple and non-invasive method to assess immediate postoperative analgesia.

The effects of clonidine on sensitivity to phenylephrine and nitroprusside in patients with essential hypertension recovering from surgery.

UNLABELLED: Clonidine reduces postoperative circulatory instability in patients with essential hypertension. It also increases the sensitivity to vasopressors before and during anesthesia. We investigated blood pressure responses to phenylephrine and nitroprusside pre- vs postoperatively and the effect of clonidine on these responses in patients with essential hypertension. Twenty patients received clonidine 6 microg/kg orally 120 min before anesthesia and 3 microg/kg IV over the final hour of surgery or an identical placebo. During increasing bolus doses of phenylephrine and nitroprusside (30-300 microg), the maximal systolic pressure responses were recorded at baseline on the day before surgery, before the induction of anesthesia, and 1 and 3 h postoperatively. Sensitivity to phenylephrine and nitroprusside was interpolated from linear regression of the data. There was no difference between preoperative and postoperative sensitivity to phenylephrine or nitroprusside in either group. Clonidine increased sensitivity to phenylephrine versus placebo before and after surgery (response to dose of 1.5 microg/kg: 42+/-14 vs 27+/-8 mm Hg preinduction, 37+/-10 vs 26+/-8 mm Hg 3 h postoperatively; both P < 0.01), but not to nitroprusside (38+/-6 vs 37+/-10 mm Hg preinduction and 40+/-6 vs 39+/-8 mm Hg postoperatively). Clonidine increases the sensitivity to phenylephrine but not nitroprusside at baseline and postoperatively in hypertensive patients. IMPLICATIONS: Clonidine increases the sensitivity to bolus injections of the vasoconstrictor phenylephrine, but not the vasodilator sodium nitroprusside, before and after surgery in patients with preexisting hypertension. The doses of vasopressors should be reduced accordingly in hypertensive patients receiving perioperative clonidine.

Cardiac baroreflex during the postoperative period in patients with hypertension: effect of clonidine.

BACKGROUND: Patients with essential hypertension show altered baroreflex control of heart rate, and during the perioperative period they demonstrate increased circulatory instability. Clonidine has been shown to reduce perioperative circulatory instability. This study documents changes in measures of heart rate control after surgery in patients with essential hypertension and determines the effects of clonidine on postoperative heart rate control in these patients. METHODS: Using a randomized double-blind placebo-controlled design, 20 patients with essential hypertension (systolic pressure >160 mm Hg or diastolic pressure >95 mm Hg for > or =1 yr) were assigned to receive clonidine (or placebo), 6 microg/kg orally 120 min before anesthesia and 3 microg/kg intravenously over 60 min before the end of surgery. The spontaneous baroreflex ("sequence") technique and analysis of heart rate variability were used to quantify control of heart rate at baseline, before induction of anesthesia, and 1 and 3 h postoperatively. RESULTS: Baroreflex slope and heart rate variability were reduced postoperatively in patients given placebo but not those given clonidine. Clonidine resulted in greater postoperative baroreflex slope and power at all frequency ranges compared with placebo (4.9+/-2.9 vs. 2.2+/-2.1 ms/mm Hg for baroreflex slope, 354+/-685 vs. 30+/-37 ms2/Hz for high frequency variability). Clonidine also resulted in lower concentrations of catecholamine, decreased mean heart rate and blood pressure, and decreased perioperative tachycardia and hypertension. CONCLUSIONS: Patients with hypertension exhibit reduced heart rate control during the recovery period after elective surgery. Clonidine prevents this reduction in heart rate control. This may represent a basis for the improved circulatory stability seen with perioperative administration of clonidine.