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.

Nociception, in contrast to pain, is not a subjective feeling, but the physiological encoding and processing of nociceptive stimuli. However, monitoring nociception remains a challenge in attempts to lower the incidence of acute postoperative pain and the move towards a more automated approach to analgesia and anaesthesia. To date, several commercialised devices promise a more accurate reflection of nociception than the traditionally used vital signs, blood pressure and heart rate. This narrative review presents an overview of existing technologies and commercially available devices, and offers a perspective for future research. Although firm conclusions about individual methods may be premature, none currently appears to offer a sufficiently broad applicability. Furthermore, there is currently no firm evidence for any clinically relevant influence of such devices on patient outcome. However, the available monitors have significantly aided the understanding of underlying mechanisms and identification of potential pitfalls.

SummaryThe 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. Postoperative complications may be prevented by a suitable choice of analgesic technique [1]. Moreover, adequate pain control is a prerequisite for the use of rehabilitation programmes to accelerate recovery from surgery [1], and existing data indicate that effective pain relief may lead to an improved overall postoperative outcome [2].Accurate assessment of postoperative pain is a key factor for successful pain management. Though various scoring systems are available for this purpose, they rely almost entirely on the co-operation of the patient. Hence these systems are bound to fail in unconscious, confused or otherwise uncooperative subjects. A more objective, subject-independent parameter for the assessment of pain is therefore highly desirable. As pain greatly modifies the surgical stress response [3], monitoring of parameters of postoperative stress, such as sympathetic tone, could be a helpful tool for assessment of analgesia. Increased sympathetic tone leads to a higher rate of firing in sympathetic, postganglionic cholinergic neurones [4,5]. The resulting change of sweat gland filling can be measured in terms of skin conductance. The number of fluctuations within the mean skin conductance per second has been reported to correlate well with intra-operative noxious stimuli, with a sensitivity and specificity of 86% for their detection [6].In a pilot study [7] we confirmed correlation between the number of fluctuations of skin conductance per second and postoperative pain in the recovery room rated on a numeric rating scale (0-10). As the number of fluctuations of skin conductance per second was highly Anaesthesia, 2007, 62, pages 989-993

The severity of postoperative pain significantly influences SC. Using cut-off values, NFSC may prove a useful tool for pain assessment in the postoperative period.

ANI did not reflect different states of acute postoperative pain measured on a NRS scale after adult sevoflurane-based general anaesthesia.

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 microg/dL). This indicates a higher sympathetic outflow using BAL versus TIVA during ear-nose-throat surgery.

Australian New Zealand Clinical Trials Registry: ACTRN12612000087853.

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.