Surgical pleth index: prospective validation of the score to predict moderate-to-severe postoperative pain.

BACKGROUND: Reported outcome benefits after surgical pleth index (SPI, GE Healthcare, Helsinki, Finland) guided anaesthesia are conflicting. One potential explanation may be the lack of evidence for the selection of meaningful SPI target values. A recently published trial found an SPI cut-off of 30 as a 'best-fit' to predict moderate-to-severe acute postoperative pain. This prospective trial was designed to validate this target and to investigate the influence of patient age on SPI in this context. METHODS: After ethics approval, 200 patients undergoing non-emergency surgery were enrolled. Data related to SPI, heart rate (HR), and mean arterial pressure (MAP) were recorded for the last 5 min of surgery, just before arousal. After admission to recovery, pain scores (numeric rating scale [NRS], 0-10) were obtained every 5 min for 15 min. RESULTS: The data of 196 patients were analysed. Receiver-operating curve analysis showed a cut-off SPI value of 29 to be the optimum intraoperative target to discriminate between NRS 0-3 and 4-10. This confirms the 'best fit' cut-off for SPI published previously. Though still superior to HR and MAP, the sensitivity and specificity of the SPI were only poor. Age had no influence on the predictive accuracy of SPI. CONCLUSIONS: An SPI of approximately 30 was confirmed as having the best sensitivity/specificity to predict moderate-to-severe pain in the postanaesthesia care unit. However, the predictive accuracy was overall poor and not influenced by patient age. CLINICAL TRIAL REGISTRATION: ACTRN12617001475336.

Cuffed vs. uncuffed tracheal tubes in children: a randomised controlled trial comparing leak, tidal volume and complications.

Cuffed tracheal tubes are increasingly used in paediatric anaesthetic practice. This study compared tidal volume and leakage around cuffed and uncuffed tracheal tubes in children who required standardised mechanical ventilation of their lungs in the operating theatre. Children (0-16 years) undergoing elective surgery requiring tracheal intubation were randomly assigned to receive either a cuffed or an uncuffed tracheal tube. Assessments were made at five different time-points: during volume-controlled ventilation 6 ml.kg-1 , PEEP 5 cmH2 O and during pressure-controlled ventilation 10 cmH2 O / PEEP 5 cmH2 O. The pressure-controlled ventilation measurement time-points were: just before a standardised recruitment manoeuvre; just after recruitment manoeuvre; 10 min; and 30 min after the recruitment manoeuvre. Problems and complications were recorded. During volume-controlled ventilation, leakage was significantly less with cuffed tracheal tubes than with uncuffed tracheal tubes; in ml.kg-1 , median (IQR [range]) 0.20 (0.13-0.39 [0.04-0.60]) vs. 0.82 (0.58-1.38 [0.24-4.85]), respectively, p < 0.001. With pressure-controlled ventilation, leakage was less with cuffed tracheal tubes and stayed unchanged over a 30-min period, whereas with uncuffed tracheal tubes, leakage was higher and increased further over the 30-min period. Tidal volumes were higher in the cuffed group and increased over time, but in the uncuffed group were lower and decreased over time. Both groups showed an increase in tidal volumes following recruitment manoeuvres. There were more short-term complications with uncuffed tracheal tubes, but no major complications were recorded in either group at long-term follow-up. With standardised ventilator settings, cuffed tracheal tubes produced better ventilation characteristics compared with uncuffed tracheal tubes during general anaesthesia for routine elective surgery.

Surgical pleth index: prediction of postoperative pain in children?

BACKGROUND: Surgical Pleth Index (SPI) is a non-invasive, dimensionless score (0-100) aimed to allow an estimate of intraoperative nociception. Thus, it may be a useful tool to guide intraoperative analgesia. However, no optimum SPI target range for the use in children has yet been defined. It was the aim of this study to define a clinically appropriate SPI target to predict moderate-severe postoperative pain in children. METHODS: After ethics approval 105 children (2-16 yr) undergoing elective sevoflurane/opioid-based anaesthesia were included. SPI was recorded directly before the end of surgery and compared with acute postoperative pain (age appropriately assessed on different pain scales in the age groups two to three yr, four to eight yr and nine to16 yr) in the postoperative acute care unit (PACU). RESULTS: Data of 93 children were analysed. A significant negative correlation was found between age and SPI (r=-0.43; P=0.03). The SPI cut-off value with the highest sensitivity (76%) and specificity (62%) in all children combined was 40. The negative predictive value for SPI ≤ 40 to predict the absence of moderate-severe pain in PACU was 87.5%. The commonly used SPI cut-off (50) published in all related studies had neither any clinically relevant sensitivity nor specificity to predict the presence or absence of acute pain in PACU. CONCLUSIONS: The results suggest that a lower (≤ 40) than previously published (50) target for SPI may be more appropriate in studies investigating SPI guided anaesthesia in children, if the avoidance of moderate-severe postoperative pain is the main goal. CLINICAL TRIAL REGISTRATION: ACTRN12616001139460.

The effect of deep muscle relaxation on the force required during Latissimus Dorsi dissection for breast reconstructive surgery: results of a prospective, double-blinded observational pilot study.

BACKGROUND: The use of neuromuscular blocking agents has previously been suggested to facilitate the dissection of the latissimus dorsi muscle during breast reconstructive surgery. The aim of this study was to quantify the influence of deep muscle relaxation on the force required to lift the latissimus dorsi muscle during flap preparation. METHODS: After ethics approval and written informed consent 15 patients scheduled for elective breast reconstruction with a latissimus dorsi pedicled flap (muscle flap, not myocutaneous flap) under general anaesthesia were prospectively included. Midway through the muscle dissection a sterile cotton tape was slung around the mid portion of the muscle and connected with a sterile strain gauge stably positioned just above the patient. Thereafter, the muscle was lifted by moving the strain gauge vertically upwards until a muscle tension similar to that created manually during muscle dissection was achieved. The force (N) and distance required to tension the muscle were recorded and the tension released. In a randomized and blinded crossover design either rocuronium (0.6 mg.kg-1) or normal saline were given intravenously, and the tension protocol was repeated 2 min after each drug administration. RESULTS: Muscle relaxation significantly reduced the force for flap tensioning (median [percentiles] - 22 [-32/-13] %; P = 0.011) in 10/15 patients. However, in the remaining 5 patients no significant effect was measured. Normal saline had no effect on the measured force. CONCLUSIONS: Deep muscle relaxation significantly reduces the force required to manually elevate the latissimus dorsi muscle during its dissection in the majority of but not all patients. TRIAL REGISTRATION: The study was retrospectively registered on [17.6.2014] with the Australian and New Zealand Clinical Trials Registry. ACTRN12614000637640.

Surgical pleth index: prediction of postoperative pain and influence of arousal.

BACKGROUND: There are conflicting reports concerning the outcome after anaesthesia guided by the surgical pleth index (SPI; GE Healthcare, Helsinki, Finland). One potential explanation may be the lack of evidence for the selection of SPI cut-off values. The aim of this trial was to investigate the correlation between SPI, arousal, and postoperative pain and to define a cut-off value for SPI to predict moderate-to-severe pain. METHODS: After obtaining ethical approval and written informed consent, 70 patients undergoing non-emergency surgery were enrolled. Data relating to SPI, heart rate, mean arterial pressure, and state entropy were recorded every 10 s for the last 10 min of surgery (state entropy <60 at all times). Subsequently, recordings continued during the phase of arousal. After recovery room admission, pain scores (numerical rating scale 0-10) were obtained every 3 min for 15 min. RESULTS: Data from 65 patients were analysed. Receiver-operating characteristic curve analysis revealed an optimal intraoperative cut-off SPI value of 30 to discriminate between numerical rating scale scores 0-3 and 4-10. For this value, the negative and positive predictive values to discriminate between numerical rating scale scores 0-3 and 4-10 were 50 and 89.7%, respectively. The SPI was significantly affected by arousal, and SPI scores obtained during this phase were not predictive of postoperative pain. CONCLUSIONS: Surgical pleth index values are predictive of postoperative pain only if obtained before patient arousal. In contrast to previous studies, a relatively low SPI, >30, appears to predict pain with a high positive predictive value and may therefore be suggested for future studies of SPI-guided anaesthesia. CLINICAL TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry: ACTRN12615000804583.

Deep neuromuscular block reduces intra-abdominal pressure requirements during laparoscopic cholecystectomy: a prospective observational study.

BACKGROUND: Laparoscopic surgery causes specific post-operative discomfort and intraoperative cardiovascular, pulmonary, and splanchnic changes. The CO2 pneumoperitoneum-related intra-abdominal pressure (IAP) remains one of the main drivers of these changes. We investigated the influence of deep neuromuscular blockade (NMB) on IAP and surgical conditions. METHODS: This is an open prospective single-subject design study in 20 patients (14 female/6 male) undergoing laparoscopic cholecystectomy. Inclusion criteria were 18 years or older, and American Society of Anesthesiologists classification 1 to 3. Under a standardised anaesthesia, lowest IAP providing adequate surgical conditions was assessed without NMB and with deep NMB [post-tetanic count (PTC)<2] with rocuronium. The differences between IAP allowing for an adequate surgical field before and after administration of rocuronium were determined, as were effects of patient gender, age, and body mass index. RESULTS: Mean IAP without NMB was 12.75 (standard deviation 4.49) mmHg. Immediately after achieving a deep NMB, this was 7.20 (2.51). This pressure difference of 5.55 mmHg (5.08, P<0.001) dropped to 3.00 mmHg (4.30, P<0.01) after 15 min. Higher IAP differences were found in women compared with men. A modest inverse relationship was found between pressure difference and age. CONCLUSIONS: We found an almost 25% lower IAP after a deep NMB compared with no block in laparoscopic cholecystectomy. Younger and female patients appear to benefit more from deep neuromuscular blockade to reduce IAP.

A comparison of the i-gel(™) and the PRO-Breathe(®) laryngeal mask during pressure support ventilation in children.

Many studies comparing the i-gel(™) with laryngeal masks include patients in whom laryngeal mask cuff inflation pressures are higher than recommended, or involve the use of neuromuscular blocking drugs and positive pressure ventilation. We compared the i-gel with the PRO-Breathe(®) laryngeal mask in anaesthetised, spontaneously breathing children. Two hundred patients aged up to 16 years were randomly allocated to either the i-gel or the PRO-Breathe laryngeal mask. The PRO-Breathe was inflated to an intracuff pressure of 40 cmH2 O. All patients received pressure support of 10 cmH2 O and positive end-expiratory pressure of 5 cmH2 O. Successful insertion at the first attempt was 82% for the i-gel compared with 93% for the PRO-Breathe (p = 0.019). Leakage volume was significantly higher with i-gel sizes 1.5 (p = 0.015), 2 (p = 0.375), 2.5 (p = 0.021) and 3 (p = 0.003) compared with the equivalent-sized PRO-Breathe device. Device dislodgement following successful initial placement was more frequent with the i-gel (5%) compared with the PRO-Breathe laryngeal mask (0%). We conclude that the PRO-Breathe laryngeal mask is superior to the i-gel in terms of leakage volume and device dislodgement.

Analgesia Nociception Index (ANI) to predict intraoperative haemodynamic changes: results of a pilot investigation.

BACKGROUND: The Analgesia Nociception Index has been described to reflect different levels of intraoperative nociceptive stimulation during total intravenous anaesthesia. The association between this index and haemodynamic changes during sevoflurane-based anaesthesia was investigated in 30 patients with the hypothesis that changes in the Analgesia Nociception Index may coincide with or even predict haemodynamic changes. METHODS: The Analgesia Nociception Index as well as blood pressure and heart rate were observed during induction, at skin incision, at times of an Analgesia Noceception Index decrease > 20% ('event') and pre-/post-fentanyl administration. RESULTS: The Analgesia Nociception Index decreased with airway manipulation [mean: 52 (before) vs. 33 (after); P < 0.005] and after skin incision [mean: 63 (before) vs. 38 (after); P < 0.001], and it increased after fentanyl administration [53 (before) vs. 59 (after); P < 0.05]. However, its predictive probability to indicate heart rate and blood pressure increases of >10% was low (heart rate 0.61; blood pressure 0.59). CONCLUSIONS: The Analgesia Nociception Index appears to reflect different levels of stimulation during sevoflurane-based general anaesthesia. However, it was of little predictive value to pre-empt significant haemodynamic changes.

Long-term quality of sleep after remifentanil-based anaesthesia: a randomized controlled trial.

BACKGROUND: Clinical and pre-clinical data agree that opioids disrupt sleep architecture. Recently, remifentanil has been suggested to cause possible long-term disturbances of sleep quality. This randomized controlled clinical trial was designed to substantiate or refute a possible long-term effect of remifentanil on the quality of sleep. METHODS: One hundred patients undergoing elective surgery were randomized to receive either fentanyl or remifentanil-based anaesthesia. Before operation (T0) and 3 (T3) and 6 (T6) months after operation, the quality of sleep was assessed by the Pittsburgh Sleep Quality Index (PSQI). RESULTS: Overall, the quality of sleep for patients in the remifentanil or fentanyl group was not significantly different at any time point. Patients in the fentanyl group screened as good sleepers before operation showed no differences across time course of the study in PSQI scores. In contrast, good sleepers in the remifentanil group had significantly impaired sleep quality for at least 3 months after operation. Patients who were before operation screened as poor sleepers showed no significant changes in PSQI scores at T3 and T6 in both groups. CONCLUSIONS: The intraoperative use of remifentanil in a general patient population does not significantly alter the quality of sleep in the postoperative period. However, it may result in a significant reduction in the quality of sleep in patients before operation considered good sleepers. These changes were not observed in the group of patients receiving fentanyl. The relevance of these findings in terms of patient recovery and quality-of-life warrants further investigation. Trial Registration. ACTRN12610000362099.

Analgesia nociception index: evaluation as a new parameter for acute postoperative pain.

BACKGROUND: A means of identifying the presence and severity of pain that is not reliant on the subjective assessment of pain is desirable whenever a patient self-rating of pain cannot be easily obtained (e.g. sedated patients, very young children, individuals with learning difficulties). The heart rate variability based analgesia nociception index (ANI) has been proposed to reflect different levels of acute pain. The aim of this study was to compare ANI scores with a numeric rating scale (NRS, 0-10) based on self-assessment of pain in the recovery room. METHODS: One hundred and twenty patients after non-emergency surgery were included. On arrival in the post-anaesthesia care unit (PACU) and subsequently at 5 min intervals, patients were asked to rate their level of pain on a 0-10 NRS. ANI values 0-100 points (low values indicating higher levels of pain) were recorded simultaneously. RESULTS: Eight hundred and sixteen pain ratings from 114 patients were included in the analysis. A small but statistically significant negative correlation was found between ANI and the NRS scores (ρ=-0.075; P=0.034). A small but significant difference in ANI was found comparing the extremes of pain [mean (se): NRS 0: 63 (1.4) vs NRS 6-10: 59 (1.4); P=0.027]. However, a receiver-operating analysis testing the value of ANI to distinguish between NRS 0 and NRS 6-10 revealed only low sensitivity and specificity. CONCLUSION: ANI did not reflect different states of acute postoperative pain measured on a NRS scale after adult sevoflurane-based general anaesthesia.

Monitoring of intra-operative nociception: skin conductance and surgical stress index versus stress hormone plasma levels.

'Surgical Stress Index' and the 'Number of Fluctuations in Skin Conductance.s⁻¹, use different methods to analyse sympathetic tone and so provide an estimate of peri-operative analgesia. The aim of our study was to investigate the relationship between these methods and stress hormone plasma levels. In 20 patients scheduled for elective surgery, values of the two methods, mean arterial blood pressure, heart rate and blood samples (to measure plasma levels of adrenaline, noradrenaline, adrenocorticotrophic hormone and cortisol) were obtained at five time points. Changes in Surgical Stress Index and the Number of Fluctuations in Skin Conductance.s⁻¹ only partially reflected changes in plasma noradrenaline levels. Surgical Stress Index, heart rate and blood pressure, but not the 'Number of Fluctuations in Skin Conductance.s⁻¹ changed in response to changes in depth of analgesia by showing significant differences between before and after a bolus of fentanyl. However, the overall predictive ability of both methods was poor.

Monitoring of sympathetic tone to assess postoperative pain: skin conductance vs surgical stress index.

The number of fluctuations in skin conductance per second has been described as a potential tool for monitoring postoperative pain. More recently, the surgical stress index has shown promising correlations with intra-operative painful stimuli. We compared both methods for their ability to assess postoperative pain, in 100 postoperative patients who were also asked to quantify their level of pain at different time points in the recovery room. The number of fluctuations per second and surgical stress index were significantly different between pain scoring 5/10 on a numeric rating scale (mean (SE) number of fluctuations per second 0.12 (0.02) vs 0.21 (0.03), respectively; p = 0.017, and surgical stress index 57 (1.4) vs 64 (1.9) points, respectively; p = 0.001). Both number of fluctuations in skin conductance per second and surgical stress index identified timepoints with moderate to severe pain with only moderate sensitivity and specificity.

Induction dose of propofol in patients using cannabis.

BACKGROUND AND OBJECTIVE: An estimated 150 million people worldwide use cannabis. The effect of cannabis on anaesthetic requirements in humans does not appear to have been studied. METHODS: In this prospective, randomized, single-blinded study, 30 male patients using cannabis more than once per week (group C) and 30 nonusers (group NC), aged 18-50 years, were induced with propofol 1.5, 2, 2.5, 3 or 3.5 mg kg. Additional doses were given when required. The primary outcome was the 50% effective dose of propofol and successful induction was determined by loss of consciousness with a bispectral index value of less than 60 and satisfactory insertion of a laryngeal mask. Propofol requirements to achieve these outcomes were recorded. RESULTS: The dose required to achieve the target bispectral index value was not significantly higher in group C, but group C required a significantly higher propofol dose to achieve laryngeal mask insertion (314.0 +/- 109.3 vs. 263.2 +/- 69.5 mg, P < 0.04). The estimated effective propofol induction dose in 50-95% of patients did not significantly differ between groups. CONCLUSION: We conclude that cannabis use increases the propofol dose required for satisfactory clinical induction when inserting a laryngeal mask.

Skin conductance as a means to predict hypotension following spinal anaesthesia.

BACKGROUND AND OBJECTIVE: Hypotension following spinal anaesthesia (SA) is common, especially in the elderly. Elevated sympathetic tone has been shown to correlate with severe hypotension after SA. The aim of this prospective trial was to investigate skin conductance (SC), as a measure of sympathetic tone, to predict hypotension after SA. METHODS: After ethical approval and written informed consent, 30 patients undergoing SA were included. Baseline measurements of SC [number of fluctuations per second (reflecting the firing rate of skin sympathetic nerves), area under the curve (AUC) A and B (reflecting the magnitude of the sympathetic impulse)], blood pressure and heart rate were recorded. After administration of SA, all parameters were assessed every 2.5 min for a total of 15 min. Baseline readings of SC were compared with the lowest blood pressure within the study period. RESULTS: Data from 30 subjects [73 (8) years] were analysed. After SA, the mean arterial blood pressure declined an average of 21.3 (11.3) mmHg. A cut-off value of 0.35 microSs for baseline AUC B allowed prediction of more than mild hypotension (>15% from baseline) after SA with a sensitivity of 72.5% and a specificity of 77.5%. CONCLUSIONS: AUC B, as a parameter of SC, may predict severe arterial hypotension after SA in the elderly.

Bronchial mucus transport velocity in patients receiving desflurane and fentanyl vs. sevoflurane and fentanyl.

BACKGROUND AND OBJECTIVE: Sevoflurane has been shown to distinctly reduce bronchial mucus transport velocity, an essential determinant of mucociliary clearance and pulmonary complications. However, sevoflurane is regarded as one of the least irritant volatile anaesthetics, especially when compared with desflurane. Hence, the aim of this double-blind, randomized, controlled trial was to assess differences in bronchial mucus transport velocity between sevoflurane and desflurane. METHODS: Twenty patients listed for general surgery were randomized to receive either maintenance of anaesthesia with desflurane and fentanyl, or sevoflurane and fentanyl. Thirty minutes after tracheal intubation, bronchial mucus transport velocity was assessed by fibreoptic observation of the movement of methylene blue dye applied to the dorsal surface of the right main bronchus. RESULTS: Both agents distinctly reduced bronchial mucus transport velocity when compared with previous studies, but the degree of impairment did not significantly differ between the investigated groups (median [25%/75% percentile]): desflurane 1.5 [0.5/4.2] vs. sevoflurane 1.3 [0.3/2.9] mm min(-1), P = 0.343). CONCLUSIONS: Desflurane is commonly regarded as more irritant to the airway, but as far as bronchial mucus transport velocity is concerned, the choice between sevoflurane and desflurane does not seem to matter.

Sugammadex: what do we know and what do we still need to know? A review of the recent (2013 to 2014) literature.

Since its launch in 2008, sugammadex has been considered one of the most significant developments in anaesthesia-related pharmacology. With almost 500 sugammadex-related publications and over nine million patient exposures worldwide, user experience and scientific data have grown exponentially. However, several important questions are yet to be answered. This article reviews the sugammadex-related literature in 2013 and 2014 to determine which of these questions have been answered more fully over the last 18 months and which questions require more information and research.

Unrestricted access to sugammadex: impact on neuromuscular blocking agent choice, reversal practice and associated healthcare costs.

Sugammadex is known to rapidly and completely reverse the effects of amino-steroidal neuromuscular blocking agents. However, the high costs of sugammadex have so far prevented its introduction as the standard reversal agent in most healthcare systems. At the Royal Perth Hospital, sugammadex was recently introduced as an unrestricted alternative to neostigmine for the reversal of amino-steroidal neuromuscular blocking agents. The aim of this retrospective observational audit was to investigate the impact of this change on clinical practice and associated healthcare costs. Data from all patients intubated during a one-month period in April to May 2010 and for a similar period in 2011 were retrospectively collected and the use of neuromuscular blocking agents and reversal agents were identified and the associated costs were calculated. More steroidal neuromuscular blocking agents and sugammadex (+743%), but less glycopyrrolate and neostigmine (-48%) were used in 2011. Using the manufacturer's list price, muscle relaxation and reversal costs increased from about A$42 per case to about A$127 per case. Between the investigated time periods no differences were found for anaesthesia time, operating time or time spent in the post anaesthesia care unit. However, there was a statistically significant decrease in the time between surgery and discharge (median 2.0 vs 2.2 days). While the design of the audit was such that no inferences can be made about the cause of this change, this is an interesting observation worthy of further investigation.