Thomas Ledowski

Neuroendocrine stress response and heart rate variability: a comparison of total intravenous versus balanced anesthesia.

Attenuating intraoperative stress is a key factor in improving outcome. We compared neuroendocrine changes and heart rate variability (HRV) during balanced anesthesia (BAL) versus total IV anesthesia (TIVA). Forty-three patients randomly received either BAL (sevoflurane/remifentanil) or TIVA (propofol/remifentanil). Depth of anesthesia was monitored by bispectral index. Stress hormones were measured at 7 time points (P1 = baseline; P2 = tracheal intubation; P3 = skin incision; P4 = maximum operative trauma; P5 = end of surgery; P6 = tracheal extubation; P7 = 15 min after tracheal extubation). HRV was analyzed by power spectrum analysis: very low frequency (VLF), low frequency (LF), high frequency (HF), LF/HF ratio, and total power (TP). LF/HF was higher in TIVA at P6 and TP was higher in TIVA at P3–7 (P3: 412.6 versus 94.2; P4: 266.7 versus 114.6; P5: 290.3 versus 111.9; P6: 1523.7 versus 658.1; P7: 1225.6 versus 342.6 ms2). BAL showed higher levels of epinephrine (P7: 100.5 versus 54 pg/mL), norepinephrine (P3: 221 versus 119.5; P4: 194 versus 130.5 pg/mL), adrenocorticotropic hormone (P2 10.5 versus 7.7; P5: 5.3 versus 3.6; P6: 10.9 versus 5.3; P7: 20.5 versus 7.1 pg/mL) and cortisol (P7: 6.9 versus 3.9 &mgr;g/dL). This indicates a higher sympathetic outflow using BAL versus TIVA during ear-nose-throat surgery.

Heart Rate Variability Predicts Severe Hypotension after Spinal Anesthesia for Elective Cesarean Delivery

Background:Hypotension due to vasodilation during subarachnoid block (SAB) for elective cesarean delivery may be harmful. Heart rate variability (HRV), reflecting autonomic control, may identify patients at risk of hypotension. Methods:Retrospectively, HRV was analyzed in 41 patients who were classified into one of three groups depending on the decrease in systolic blood pressure (SBP): mild (SBP > 100 mmHg), moderate (100 > SBP > 80 mmHg), or severe (SBP < 80 mmHg). Prospectively, HRV and hemodynamic data of 19 patients were studied. Relative low frequency (LF), relative high frequency (HF), and LF/HF ratio were analyzed. Results:Retrospective analysis of HRV showed a significantly higher sympathetic and lower parasympathetic drive in the groups with moderate and severe compared with mild hypotension before SAB (median, 25th/75th percentiles): LF/HF: mild: 1.2 (0.9/1.8), moderate: 2.8 (1.8/4.6), P < 0.05 versus mild; severe: 2.7 (2.0/3.5), P < 0.05 versus mild. Results were confirmed by findings of LF and HF. Prospectively, patients were grouped according to LF/HF before SAB: low-LF/HF: 1.5 (1.1/2.0) versus high-LF/HF: 4.0 (2.8/4.7), P < 0.05; low-LF: 58 ± 9% versus high-LF: 75 ± 10%, P < 0.05; low-HF: 41 ± 10% versus high-HF: 25 ± 10%, P < 0.05. High-risk patients had a significantly lower SBP after SAB (76 ± 21 vs. 111 ± 12 mmHg; P < 0.05). Conclusions:Retrospectively analyzed HRV of patients scheduled to undergo elective cesarean delivery during SAB showed significant differences depending on the severity of hypotension after SAB. Preliminary findings were prospectively confirmed. High LF/HF before SAB predicted severe hypotension. Preoperative HRV analysis may detect patients at risk of hypotension after SAB.

The assessment of postoperative pain by monitoring skin conductance: results of a prospective study*

The number of fluctuations of skin conductance per second correlates with postoperative pain. The aim of this prospective study was to test the cut‐off value for the number of fluctuations of skin conductance per second obtained from a previous study. Seventy‐five patients were asked to quantify their level of pain on a numeric rating scale (0–10) in the recovery room. The number of fluctuations of skin conductance per second was recorded simultaneously. The number of fluctuations of skin conductance per second was different between patients with no (0.07), mild (0.16), moderate (0.28) and severe pain (0.33); p < 0.001. The tested cut‐off value for the number of fluctuations of skin conductance per second (0.1) distinguished a numeric rating scale ≤ 3 from > 3 with 88.5% sensitivity and 67.7% specificity. The number of fluctuations of skin conductance per second may be a useful means of assessing postoperative pain.

Monitoring electrical skin conductance: a tool for the assessment of postoperative pain in children?

Background:Monitoring changes in electrical skin conductance has been described as a potentially useful tool for the detection of acute pain in adults. The aim of this study was to test the method in pediatric patients. Methods:A total of 180 postoperative pediatric patients aged 1–16 yr were included in this prospective, blinded observational study. After arrival in the recovery unit, pain was assessed by standard clinical pain assessment tools (1–3 yr: Face Legs Activity Cry Consolability Scale, 4–7 yr: Revised Faces Scale, 8–16 yr: Visual Analogue Scale) at various time points during their stay in the recovery room. The number of fluctuations in skin conductance per second (NFSC) was recorded simultaneously. Results:Data from 165 children were used for statistical analysis, and 15 patients were excluded. The area under the Receiver Operating Characteristic curve for predicting moderate to severe pain from NFSC was 0.82 (95% confidence interval 0.79–0.85). Over all age groups, an NFSC cutoff value of 0.13 was found to distinguish between no or mild versus moderate or severe pain with a sensitivity of 90% and a specificity of 64% (positive predictive value 35%, negative predictive value 97%). Conclusions:NFSC accurately predicted the absence of moderate to severe pain in postoperative pediatric patients. The measurement of NFSC may therefore provide an additional tool for pain assessment in this group of patients. However, more research is needed to prospectively investigate the observations made in this study and to determine the clinical applicability of the method.

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 and > 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.

Retrospective investigation of postoperative outcome after reversal of residual neuromuscular blockade: sugammadex, neostigmine or no reversal.

BACKGROUND Postoperative residual neuromuscular blockade (RNMB) is associated with significant morbidity. OBJECTIVE The aim of this retrospective data analysis was to investigate the influence of the method of RNMB reversal on postoperative outcome. SETTING Tertiary teaching hospital in Western Australia. PATIENTS With Ethics Committee approval, data from 1444 patients who received at least one dose of a non-depolarising muscle relaxant intraoperatively during 2011 were analysed. MAIN OUTCOME MEASURES Endpoints included unwanted events in the postanaesthesia care unit (PACU); symptoms of pulmonary complications within 7 postoperative days (0 to 100 outcome score based on ‘temperature >38°C’, ‘leucocyte count >11 × 109 l−1’, ‘physical examination consistent with pneumonia’ and ‘shortness of breath’); PACU turnover time; and length of hospital stay. RESULTS Data from 1444 patients (722 sugammadex, 212 neostigmine and 510 no-reversal) were analysed. The incidence of postoperative nausea and vomiting (PONV) in PACU was higher in neostigmine-reversed than sugammadex-reversed patients (21.5 vs. 13.6%; P <0.05). No differences were found regarding other PACU incidents, length of PACU stay or hospital stay. Pulmonary outcome deteriorated significantly (outcome score increased) with age and American Society of Anesthesiologists (ASA) physical status. This was observed particularly in ASA 3/4 patients more than 60 years of age in neostigmine-reversed or non-reversed patients, but almost no detrimental effect of age on pulmonary outcome was found in the sugammadex group (P <0.05). CONCLUSION RNMB reversal with sugammadex was associated with the lowest rate of PONV and may reduce the risk of pulmonary complications in elderly ASA 3/4 patients. TRIAL REGISTRATION Australian New Zealand Clinical Trials Registry: ACTRN12612000087853.

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.

Bronchial mucus transport velocity in patients receiving Propofol and Remifentanil versus Sevoflurane and Remifentanil anesthesia

Volatile anesthetics reduce ciliary beat frequency in vitro. It has been reported that impaired bronchial mucus transport velocity (BTV) is associated with significantly increased pulmonary complications. In this study, we sought to determine in vivo differences in BTV, comparing patients having total IV anesthesia (TIVA) with propofol and remifentanil to anesthesia with sevoflurane and remifentanil. Twenty-two patients scheduled for elective general surgery were randomized to one of two groups: TIVA (propofol/remifentanil) or SEVO (sevoflurane/remifentanil). Thirty minutes after tracheal intubation, BTV was assessed by fiberoptic observation of the movement of methylene blue dye applied to the dorsal surface of the right main bronchus. BTV was significantly reduced in the SEVO group compared with the TIVA group (mean, 1.5 ± 0.7 [0–2.3] versus 4.8 ± 2.1 [2.3–8.8] mm/min; P < 0.0001). Anesthesia with sevoflurane may lead to significantly impaired bronchociliary clearance in comparison to TIVA. This could have implications for perioperative pulmonary complications, in particular in patients at risk for pulmonary complications.

Effects of acute postoperative pain on catecholamine plasma levels, hemodynamic parameters, and cardiac autonomic control.

Summary Measurements of hemodynamic, endocrine, and autonomic parameters are not useful as surrogates to estimate the severity of acute postoperative pain in the clinical setting. Abstract Postoperative pain is often stated to be a significant contributor to a sympathetic stress response after surgery. However, hardly any evidence has been published to support this assumption. Hence it was the aim of this trial to investigate the relationship between postoperative pain and hemodynamic, endocrine, and autonomic parameters. A total of 85 postoperative patients in the recovery room were repeatedly asked to rate their pain on a numeric rating scale (NRS). Concurrently, the parameters of heart rate variability (HRV) were analysed, and mean arterial pressure (MAP), heart rate (HR) and respiration rate (RR) were recorded. Pain was categorized into no, mild, moderate, and severe. Blood samples were taken for epinephrine (EPI) and norepinephrine (NE) plasma level assessment at the time of recovery room admission and discharge, and each time pain was found decreased in categorized severity. A total of 239 pain readings were obtained. None of the investigated parameters correlated with NRS scores. NE was higher at NRS 5 to 10 vs. NRS 0 to 4 (mean [SEM]: 1009 [73] pg/mL vs. 872 [65] pg/mL; P < 0.01). This was also found for MAP, but not for EPI or the parameters of HRV, HR, and RR. In contrast to common belief, the severity of postoperative pain does not appear to be associated with the degree of sympathetic stress response after surgery, and other factors such as surgical trauma may be more important. Importantly, the absence of signs of sympathetic stimulation cannot be seen as a guarantee for the absence of significant pain.

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.