Comparative usability of modern anaesthesia ventilators: a human factors study.

BACKGROUND: The anaesthesia ventilator represents the key equipment for intraoperative respiratory care. Improper operation of this device may threaten a patient's health. A self-explanatory interface facilitates handling and decreases the risk of operating errors. This study systematically evaluates the usability of user interfaces in four modern anaesthesia ventilators. METHODS: Twenty naïve operators were asked to execute 20 tasks on each of four different anaesthesia ventilators (Avance CS2™, GE Healthcare; Flow-i™, Maquet; and Perseus™ and Primus™, Dräger) in a randomized order. The success of task execution, frequency of requests for assistance, and processing times were recorded. During the tasks, the operators' visual focus was measured via eye-tracking. Additionally, subjective assessments of usability were evaluated by a standardized questionnaire. For comparison, six experienced operators undertook the same protocol. RESULTS: The overall rate of falsely executed tasks was low. Naïve operators requested assistance least when using the Perseus (26). Pooled processing times were shortest for the Perseus (222 s), followed by the Primus (223 s), the Avance (238 s), and the Flow-i (353 s). Task-specific processing times differed considerably between the devices. Eye-tracking analyses revealed associated interface issues that impeded the operators' performance. Operators rated usability best for the Perseus [mean (sd): 67 (17) arbitrary units] and worst for the Flow-i [50 (16) arbitrary units]. Results from experienced operators support these findings by trend. CONCLUSIONS: The usability of modern anaesthesia ventilators differs considerably. Interface issues of specific tasks impair the operator's efficiency. Eliminating the specific usability issues might improve the operator's performance and, as a consequence, the patient's safety.

Combined paravertebral and intrathecal vs thoracic epidural analgesia for post-thoracotomy pain relief.

BACKGROUND: Although thoracic epidural analgesia (TEA) is considered the gold standard for post-thoracotomy pain relief, thoracic paravertebral block (PVB) and intrathecal opioid (ITO) administration have also been shown to be efficacious. We hypothesized that the combination of PVB and ITO provides analgesia comparable with that of TEA. METHODS: After local ethics committee approval, 84 consecutive patients undergoing open thoracic procedures were randomized to the TEA (ropivacaine 0.2%+sufentanil) or the PVB (ropivacaine 0.5%)+ITO (sufentanil+morphine) group. The primary endpoints were pain intensities at rest and during coughing/movement at 1, 2, 4, 8, 12, 24, 48, and 72 h after operation assessed by visual analogue scale (VAS) score. Data were analysed by multivariate analysis (anova; P<0.05). RESULTS: Patient and surgical characteristics were comparable between the groups. The mean and maximal VAS scores were lower in the TEA (n=43) than in the PVB+ITO group (n=37) at several time points at rest (P<0.026) and during coughing/movement (P<0.021). However, in the PVB+ITO group, the mean VAS scores never exceeded 1.9 and 3.5 at rest and during coughing/movement, respectively; and the maximal differences between the groups (TEA vs PVB+ITO) in the maximal VAS scores were only 1.2 (3.4 vs 4.6) at rest, and 1.3 (4.4 vs 5.7) during coughing/movement. CONCLUSIONS: Although VAS scores were statistically lower in the TEA compared with the PVB+ITO group at some observation points, the differences were small and of questionable clinical relevance. Thus, combined PVB and ITO can be considered a satisfactory alternative to TEA for post-thoracotomy pain relief. ClinicalTrials.gov number. NCT00493909.

Assessment of volume preload on uteroplacental blood flow during epidural anaesthesia for Caesarean section.

BACKGROUND AND OBJECTIVE: Epidural and spinal anaesthesia are the preferred mode of anaesthesia for Caesarean section. Volume preloading is recommended to prevent maternal hypotension and a reduction in uteroplacental blood flow, although positive effects of volume preloading on maternal cardiac output and arterial pressure are debatable. Doppler measurements of the umbilical artery beyond deriving pulsatility indices are not routinely performed. METHODS: After Institutional Review Board approval and written informed consent, 14 consecutiVe women with epidural anaesthesia for Caesarean section received either hydroxyethyl starch 500 mL or gelatine 500 mL. Haemodynamic variables monitored were maternal arterial pressure, maximal blood flow velocity and pulsatility indices of the uterine artery derived from Doppler measurements. CONCLUSIONS: Maternal arterial pressure and pulsatility indices in both groups did not change from baseline after intravenous colloid infusion. However, uterine blood flow increased significantly in both groups. The effectiveness of volume preloading may therefore be better described by changes in maximum uterine blood flow velocity than by pulsatility indices or maternal arterial pressure.

Adsorption of sufentanil to epidural filters and catheters.

BACKGROUND AND OBJECTIVE: Stable drug concentrations must be administered to provide adequate patient-controlled epidural analgesia. This study investigated the stability of sufentanil after the epidural delivery system had been flushed with solutions containing the drug. METHODS: Sufentanil citrate, 5 microg mL(-1) was injected through an epidural catheter system into a glass container. The concentrations of the drug leaving the system, in 1 mL aliquots (1-5 mL) were measured using high-performance liquid chromatography. In the same manner, sufentanil samples were analysed after flushing the filter, as well as after priming the filter and catheter. RESULTS: ANOVA for repeated measurements demonstrated that sufentanil concentrations remained constant as long as the catheter had been adequately flushed. However, the concentration of sufentanil in the solution exiting the filter was reduced significantly. Hardly any sufentanil could be detected (0.09 +/- 0.01 microg mL(-1), P < 0.001) in the first 1 mL aliquot (probe) leaving the filter. Altogether, 3 mL sufentanil solution was needed to pass through the filter before the baseline values were restored (P > 0.05). The greatest decrease occurred when the whole epidural delivery apparatus (catheter and filter) was primed; to regain baseline values, as much as 4 mL solution was needed to flush the system. CONCLUSIONS: Sufentanil citrate is adsorbed by the materials used to manufacture systems (catheters, filters) used in epidural anaesthesia. Hence, the epidural catheter system should be primed with sufentanil before connecting it to the patient so as to deliver reliable concentrations.

Myocardial ischaemia in patients with impaired left ventricular function undergoing coronary artery bypass grafting--milrinone versus nifedipin.

BACKGROUND AND OBJECTIVE: Myocardial ischaemia and infarction are major complications immediately after coronary artery bypass grafting. They may be due to incomplete surgical revascularization, perioperative anaesthetic management or vasospasm of arterial grafts, e.g. the internal mammary artery. Infusions of nifedipine or milrinone have been advocated to prevent spasm of the mammary artery. The study compared the incidence of myocardial ischaemia after continuous infusion of either nifedipine (0.2 microg kg(-1) min(-1)) or milrinone (0.375 microg kg(-1) min(-1)) in patients with compromised left ventricular function scheduled for elective coronary artery bypass graft. METHODS: After Institutional Review Board approval, this double-blinded randomized clinical study enrolled 30 adult patients with compromised left ventricular function (ejection fraction < 0.4) scheduled for elective coronary artery bypass grafting after written informed consent had been obtained. Ischaemia was detected by Holter electrocardiographic monitoring. The incidence of myocardial cell death was monitored by serial determinations of the creatine kinase-MB (CK-MB) and troponin-I. RESULTS: New ST elevation > or = 0.2 mV or new ST depression < or = 0.1 mV occurred in five of 15 patients in the milrinone group (33.3%) and in 13 of 15 patients (86.6%) in the nifedipine group (P < 0.05). There were increases in CK-MB and troponin-I in both groups. Twenty-four hours postoperatively, CK-MB (P = 0.003) and troponin-I (P = 0.001) were significantly higher in the nifedipine group. CONCLUSIONS: Perioperative continuous infusion of milrinone, compared with nifedipine, results in a significantly lower incidence of myocardial ischaemia and myocardial cell damage after elective coronary artery bypass grafting.

Effect of pretreatment with ketorolac on propofol injection pain.

BACKGROUND: : Pain on injection is still a major problem with propofol. We performed this study to compare different doses of intravenous (i.v.) ketorolac with and without venous occlusion and its effect on the incidence and the severity of the pain after propofol injection. METHODS: We conducted a prospective, randomized and double-blind study of 180 patients (20-60 years of age.) scheduled to undergo elective surgery. Six groups of patients were generated: group A received normal saline (NS) 2 ml i.v.; groups B, C, D received ketorolac 10 mg in 2 ml NS with venous occlusion (VO) and a subsequent propofol injection at either 30, 60 or 120 s; groups E and F received ketorolac 15 mg and 30 mg in 2 ml NS and propofol was injected after 60 s. The pain perception was assessed during injection of propofol in all patients. RESULT: : The incidence of propofol-associated injection pain was for A: 46.7%; B: 43.4%; C: 23.3%; D:16.7%; E: 20%, and F: 10%. The incidence of pain following propofol injection was reduced by i.v. ketorolac 10 mg with venous occlusion for 120 s. Furthermore, i.v. ketorolac 15 mg and 30 mg but not 10 mg following propofol injection after 60 s without venous occlusion revealed significant pain reduction when compared to saline group. There was no difference in venous sequelae at 7 days postoperatively between the groups. CONCLUSION: Our results suggested that pretreatment with i.v. 15 and 30 mg ketorolac reduces pain following propofol injection. Moreover, pretreatment with i.v. ketorolac 10 mg with venous occlusion for 120 s achieves the same pain relief effect.

Amantadine, a N-methyl-D-aspartate receptor antagonist, does not enhance postoperative analgesia in women undergoing abdominal hysterectomy.

UNLABELLED: N-methyl-D-aspartate (NMDA) antagonists administered before surgery will improve postoperative analgesia, presumably by inhibiting spinal sensitization processes. However, current clinical formulations of NMDA antagonists either enable only an oral application (i.e., dextromethorphan) or are associated with psychotropic side effects, as with the IV delivery of ketamine. Because of its noncompetitive NMDA receptor antagonist characteristics, amantadine may improve postoperative analgesia when administered before surgically induced trauma. In this prospective, randomized clinical study, we examined whether female patients undergoing elective abdominal hysterectomy experienced less postoperative pain when IV amantadine was applied in comparison with placebo before the start of surgery. Thirty patients were randomly assigned to receive 500 mL saline IV before the induction of standardized general anesthesia in Group 1 (Control group) or, in a double-blinded manner, 200 mg amantadine IV in 500 mL saline in Group 2 (Treatment group). Postoperative pain control was provided via IV patient-controlled analgesia with piritramide. During the first 48 h after tracheal extubation, pain perception was assessed by visual analog scales, and all analgesic requirements were documented. There were no significant differences between the two groups with respect to pain scores, postoperative analgesic requirements, and the incidence of side effects. Because of no differences in postoperative pain or opioid consumption, we conclude that a preoperative dose of 200 mg amantadine IV fails to enhance postoperative analgesia in patients undergoing elective abdominal hysterectomy. IMPLICATIONS: Because of no differences in postoperative pain or opioid consumption, we conclude that a preoperative dose of 200 mg amantadine IV fails to enhance postoperative analgesia in patients undergoing elective abdominal hysterectomy.

[Efficacy of oncologic surgery. Does anesthesia influence the postoperative outcome?]. / Effizienz der onkologischen Chirurgie. Hat die Anästhesie einen Einfluss auf das postoperative Ergebnis?

Major surgical interventions in tumour surgery are still associated with perioperative cardiopulmonary, infectious, thromboembolic, cerebral, and gastrointestinal complications. There are different prophylactic and therapeutic possibilities to anticipate or counteract these perioperative complications. The most important, including beta blockers and alpha-2-agonists for patients at coronary risk, preoperative optimisation of oxygen transport in high risk surgical patients and the concept of multimodal perioperative therapy (analgesia, early mobilisation, early enteral nutrition, and others) combined with high perioperative inspiratory oxygen concentration and maintenance of normothermia to reduce wound infection and cardiac complications are described in this paper.

Multimodal perioperative management--combining thoracic epidural analgesia, forced mobilization, and oral nutrition--reduces hormonal and metabolic stress and improves convalescence after major urologic surgery.

We sought in this prospective study to use a multimodal approach to reduce stress and improve recovery in patients undergoing major surgery. During an initial study period, 30 patients were randomly allocated to receive general anesthesia (GA; Group 1) or a combination of GA and intraoperative thoracic epidural analgesia (TEA; Group 2) when undergoing radical cystectomy. Parenteral nutrition was provided for 5 days after surgery. During the second period, 15 patients were treated with a multimodal approach (Group 3) consisting of intraoperative GA and TEA, postoperative patient-controlled TEA, early oral nutrition, and enforced mobilization. Data for plasma and urine catecholamines, plasma cortisol, the nitrogen balance, the postoperative inflammatory nutrition index, pain relief, fatigue, sleep, overnight recovery, recovery of bowel function, and mobilization were recorded up to the fifth postoperative day. Plasma concentrations of catecholamines and cortisol were comparable in all patients, but those in Group 3 had lower levels of urinary catecholamine excretion. Protein intake was more effective with parenteral nutrition. Nitrogen balances were less negative, and the postoperative inflammatory nutrition index score increased significantly in the traditional groups but not in Group 3. Multimodally treated patients reported less fatigue and better overnight recovery. Along with improved pain relief, recovery of bowel function, and ambulation, there were no differences in the postoperative complication rates among the three groups. The multimodal approach reduced stress and improved metabolism and recovery after radical cystectomy.

Assessment of depth of anesthesia and postoperative respiratory recovery after remifentanil- versus alfentanil-based total intravenous anesthesia in patients undergoing ear-nose-throat surgery.

BACKGROUND: The authors investigated whether total intravenous anesthesia (TIVA) with precalculated equipotent infusion schemes for remifentanil and alfentanil would ensure appropriate analgesia and that remifentanil would result in better recovery characteristics. METHODS: Forty consenting patients (classified as American Society of Anesthesiologists physical status I-III) scheduled for microlaryngoscopy were randomized to receive, in a double-blind manner, either remifentanil (loading dose 1 microg/kg; maintenance infusion, 0.25 microg x kg(-1) x min-1) or alfentanil (loading dose, 50 microg/kg; maintenance infusion, 1 microg x kg(-1) x min-1) as the analgesic component of TIVA. They were combined with propofol (loading dose, 2 mg/kg; maintenance infusion, 100 microg x kg(-1) min(-1)). To insure an equal state of anesthesia, the opioids were titrated to maintain heart rate and mean arterial pressure within 20% of baseline, and propofol was titrated to keep the bispectral index (BIS) less than 60. Neuromuscular blockade was achieved with succinylcholine. Drug dosages and the times from cessation of anesthesia to extubation, verbal response, recovery of ventilation, and neuropsychological testing, orientation, and discharge readiness were recorded. RESULTS: Demographics, duration of surgery, and anesthesia were similar between the two groups. Both groups received similar propofol doses. There were no difference in BIS values preoperatively (mean, 96), intraoperatively (mean, 55), and postoperatively (mean, 96). Recovery of BIS and times for verbal response did not differ. At 20, 30, and 40 min after terminating the opioid infusion, the peripheral oxygen saturation and respiratory rate were significantly higher in the remifentanil group compared with the alfentanil group. CONCLUSIONS: When both the hypnotic and analgesic components of a TIVA-based anesthetic are administered in equipotent doses, remifentanil provides a more rapid respiratory recovery, even after brief surgical procedures, compared with alfentanil.

Effect of isoflurane versus nicardipine on blood flow of lumbar paraspinal muscles during controlled hypotension for spinal surgery.

STUDY DESIGN: This study compared the effects of isoflurane and nicardipine on regional blood flow of the lumbar paraspinal muscles. OBJECTIVES: The purpose of this study was to determine whether treatment with hypotensive agents result in ischemia of the lumbar paraspinal muscles, thereby facilitating surgical procedures. SUMMARY OF BACKGROUND DATA: Despite the general acceptance of controlled hypotension as effective in reducing blood loss during spinal surgery, the changes of blood flow that occur at the lumbar paraspinal muscles when this technique is applied remain unclear. The use of laser Doppler flowmetry allows changes of muscle blood flow to be easily detected in real time with minimal invasion, thereby allowing differences among distinct pharmacological approaches for induction and maintenance of controlled hypotension to be evaluated. METHODS: The prehypotensive and hypotensive (reduction of mean arterial pressure by 20 mm Hg) blood flow of the lumbar paraspinal muscles were assessed with a laser Doppler flowmeter in 40 patients undergoing lumbar spinal surgery. The first half of the patients (n = 20) received isoflurane, whereas the second half received nicardipine to achieve arterial hypotension. RESULTS: Compared with the prehypotensive state, during the hypotensive state, patients in the isoflurane group exhibited a 17% to 46% (mean, 33.7%) decrease in lumbar paraspinal muscle blood flow, whereas patients in the nicardipine group exhibited a 24% to 177% (mean, 82.5%) increase in lumbar paraspinal muscle blood flow. Statistical analysis showed a significant difference in the changes of flux after induced hypotension between the isoflurane and nicardipine group (P < 0.001). CONCLUSIONS: Depending on the pharmacological treatment used to achieve arterial hypotension in spine surgery, there will be either a reduction in paraspinal muscle blood flow (ischemia) or an enhancement of this blood flow (hyperemia).

Acute pain management: analysis, implications and consequences after prospective experience with 6349 surgical patients.

An acute pain service (APS) was set up to improve pain management after operation. We attempted to reduce the length of stay in the intensive care unit (ICU) of patients undergoing major surgery and to improve their homeostasis and rehabilitation using a multimodal approach (pain relief, stress reduction, early extubation). Patient-controlled epidural analgesia (PCEA) was a keystone of this approach. If PCEA was not applicable, patients received patient-controlled intravenous analgesia (PCIA) instead. Brachial plexus blockade (BPB) was used for surgery of the upper limbs. A computer based documentation system was used to help evaluate prospectively (a) the quality of analgesia, (b) adverse effects and risks of the special pain management techniques, and (c) cost-effectiveness. Patients receiving PCEA (n = 5.602) received a patient-titrated continuous infusion into the epidural space of either bupivacaine 0.175% or ropivacaine 0.2%, with 1 microg sufentanil mL(-1) added, followed by patient-controlled boluses of 2 mL (lockout time 20 min). For patients receiving PCIA (n = 634) an initial bolus of 7.5-15 mg piritramide was given, and the subsequent bolus was 2 mg (lockout time 10 min). A continuous infusion of bupivacaine 0.25% was administered to patients receiving BPB (n = 113). The dose was titrated to a dynamic visual analogue scale (VAS) scores < 40. The mean treatment periods were: BPB = 4.33 days, PCEA = 5.6 days, PCIA = 5.0 days. In the case of PCEA, the quality of pain relief, vigilance and satisfaction were superior compared with the PCIA method, which resulted in greater sedation and nausea. Although personal supervision was higher for the PCEA-treated patients, cost analysis revealed final savings of Euro 91,620 for the year 1998 obviating the need for an ICU stay totalling 433 days. Provided that PCEA is part of a fast-track protocol employing early tracheal extubation and optimal perioperative management, the associated initial higher costs will be recouped by the benefits to patients of better pain relief after surgery and fewer days subsequently spent in the ITU.

Intra-articular clonidine analgesia after knee arthroscopy.

Recently, it was suggested that peripherally-mediated analgesia can be accomplished by the intra-articular delivery of the mu-opioid morphine or of the a2-agonist clonidine. This clinical study assesses the potential peripheral analgesic effect of the combination of morphine and clonidine after intra-articular administration. Sixty patients (American Society of Anesthesiologists status I or II) undergoing arthroscopic repair of the knee during general anaesthesia were randomized to receive after operation, in a double-blind manner, either 1 mg morphine intra-articularly (group 1); 150 microg clonidine intra-articularly (group 2); or 1 mg morphine + 150 microg clonidine intra-articularly (group 3); or normal saline intra-articularly (group 4) in a volume of 30 mL, respectively. Visual analogue pain scores (VAS), duration of analgesia as defined by first demand for supplemental analgesics, subsequent 24 h consumption of postoperative supplementary analgesics, and patient satisfaction were evaluated. Co-administration of morphine + clonidine (group 3) resulted in a significant VAS reduction at 2 h after injection compared with the other groups. There was a tendency towards a lower need for supplementary rescue analgesia and towards a more prolonged analgesia in group 3 (211 min +/- 224 min SD) compared with group 1 (173 min +/- 197 min SD) and group 4 (91 min +/- 21 min SD). More patients were very satisfied with the postoperative analgesic regimen receiving the combination of morphine and clonidine (group 3) at 24 h postoperatively. Thus we conclude, that the peripheral co-delivery of an opioid and an a2-agonist will result in improved postoperative pain relief, when compared with each single agent given alone.

The effect of spinal ibuprofen on opioid withdrawal in the rat.

UNLABELLED: This study examines the effect of spinal ibuprofen on the behavioral manifestations associated with the opioid abstinence syndrome. Rats (n = 8 per group) were infused for 5 days with morphine and then pretreated with a spinal bolus dose of ibuprofen before systemic naloxone antagonism (300 microg). Groups included ibuprofen S(+) 1. 36, 13.6, and 136 nmol, and ibuprofen R(-) 136 nmol. A separate group of saline-infused rats was given ibuprofen S(+) 136 nmol before naloxone antagonism. Ibuprofen S(+), but not R(-), dose-dependently and stereospecifically blocked opioid withdrawal hyperalgesia but did not significantly alter other signs of the opioid abstinence syndrome. We conclude that hyperalgesia associated with opioid withdrawal can be blocked by spinally administered ibuprofen, and suggest that there may be a role for spinal prostaglandins in the enhancement of nociception observed in association with the opioid abstinence syndrome. IMPLICATIONS: This study shows that spinal ibuprofen blocks opioid withdrawal hyperalgesia in the rat in a stereospecific fashion, implicating the likely release of spinal prostaglandins during withdrawal and their possible role as neuromodulators in the enhancement of nociception that accompanies this phenomenon.

What concentration of sufentanil should be combined with ropivacaine 0.2% wt/vol for postoperative patient-controlled epidural analgesia?

UNLABELLED: In this randomized double-blinded study, we sought to determine an optimal dose-combination of sufentanil with ropivacaine 0.2% wt/vol as postoperative epidural analgesics. One hundred twenty patients undergoing major abdominal surgery under general and thoracic epidural anesthesia (T9-11) were assigned to groups receiving patient-controlled epidural analgesia with ropivacaine 0.2% wt/vol (R), ropivacaine 0.2% wt/vol + sufentanil 0.5 microg/mL (R+S0.5), 0. 75 microg/mL (R+S0.75), 1.0 microg/mL (R+S1). A visual analog score of less than 40 was considered effective, and all side effects were recorded. In randomized subgroups (10 patients per group), plasma pharmacokinetic data were obtained for both epidural drugs. Four patients in Group R and two in Group R+S0.5 were excluded because of inadequate analgesia. The drug infusion rates (range of means: 5.4-5. 9 mL/h) were similar in all patients. Analgesia was superior for sufentanil 0.75 microg/mL with no further enhancement by the larger sufentanil concentration of 1 microg/mL. Sufentanil plasma levels were within the range of the minimal effective concentrations (highest in R+S1), and there was no covariation between plasma levels and pain relief. Free ropivacaine plasma concentrations remained stable for 96 h. No severe side effects were detected, although pruritus correlated with an increasing dose of sufentanil. We conclude that the combination of ropivacaine 0.2% wt/vol and 0.75 microg/mL sufentanil provided the best analgesia with the fewest side effects of the three combinations tested. IMPLICATIONS: Sufentanil is added to epidural infusions of ropivacaine 0.2% wt/vol to improve the effectiveness of postoperative pain management. Regarding the risk of side effects, however, it is still unclear what concentration of sufentanil should be added to the local anesthetic. For postoperative thoracic epidural analgesia after major abdominal surgery, the combination of ropivacaine 0.2% wt/vol and 0.75 microg/mL sufentanil resulted in an appropriate cost:benefit ratio between good analgesia and side effects.

Remifentanil for gynaecological and obstetric procedures.

Recently, with the introduction of the novel mu-opioid receptor agonist remifentanil, anaesthesiologists have acquired a unique tool to provide adequate, titratable and predictable analgesia throughout surgery, without the risk of opioid-related delay in postoperative recovery. This new compound will therefore mandate a change in anaesthesia practice from opioid-restricted to opioid-dominated anaesthesia. It is the first in the class of esterase-metabolized opioids within the 4-anilidopiperidine series of drugs, and it possesses an analgesic potency similar to that of fentanyl. The advantages of remifentanil are mainly related to its unique pharmacokinetics, whereas its pharmacodynamics are the same as those of fentanyl. Because of these characteristics, remifentanil-based anaesthesia allows profound opioid analgesia intraoperatively, with rapid and predictable awakening thereafter. Review of the recent literature reveals the potential of remifentanil for improving analgesia in gynaecological procedures and its theoretical advantage in obstetric procedures.