Showing papers in "Acta Anaesthesiologica Scandinavica in 2002"

Preoperative predictors of moderate to intense acute postoperative pain in patients undergoing abdominal surgery

Abstract: Background: Pain is a sensory and emotional experience that is influenced by physiologic, sensory, affective, cognitive, socio-cultural, and behavioral factors. Consistent with the perspective to improve the postoperative pain control, the present study has the purpose of assessing the effect of presurgical clinical factors, psychological and demographic characteristics as predictors for reporting moderate to intense acute postoperative pain. Methods: A prospective cohort study was performed with 346 inpatients undergoing abdominal elective surgery (ASA physical status I-III, age range 18–60 years). The measuring instruments were Pain Visual Analog Scale, the State-Trait Anxiety Inventory, and the Montgomery-Asberg Depression Rating Scale. Multivariate conditional regression modeling was used to determine independent predictors for moderate to intense acute postoperative pain. Results: Moderate to intense acute postoperative pain was associated with status ASA III (odds ratio (OR) = 1.99), age (OR = 4.72), preoperative moderate to intense pain (OR = 2.96), chronic pain (OR = 1.75), high trait-anxiety and depressive mood moderate to intense (OR = 1.74 and OR = 2.00, respectively). Patients undergoing surgery to treat cancer presented lower risk for reporting moderate to intense pain OR = 0.39, as well as those that received the epidural analgesia and multimodal analgesia with systemic opioid (OR = 0.09 and OR = 0.16, respectively). Conclusions: The identification of predictive factors for intense acute postoperative pain may be useful for designing specific preventive interventions to relieve patient suffering. Especially because few of these variables are accessible for medical intervention, which would improve the clinical outcomes and quality of life of patients at risk of moderate to intense acute postoperative pain.

Nasal administration of opioids for pain management in adults.

Abstract: Background: Nasal administration of opioids may be an alternative route to intravenous, subcutaneous, oral transmucosal, oral or rectal administration in some patients. Key features may be self-administration, combined with rapid onset of action. The aim of this paper is to evaluate the present base of knowledge on this topic. Methods: The review is based on human studies found in Medline or in the reference list of these papers. The physiology of the nasal mucosa and some pharmaceutical aspects of nasal administration are described. The design of each study is described, but not systematically evaluated. Results: Pharmacokinetic studies in volunteers are reported for fentanyl, alfentanil, sufentanil, butorphanol, oxycodone and buprenorphine. Mean times for achieving maximum serum concentrations vary from 5 to 50 min, while mean figures for bioavailability vary from 46 to 71%. Fentanyl, pethidine and butorphanol have been studied for postoperative pain. Mean onset times vary from 12 to 22 min and times to peak effect from 24 to 60 min. There is considerable interindividual variation in

How to study postoperative nausea and vomiting

Abstract: Anesthesiological journals are flooded by innumerable studies of postoperative nausea and vomiting (PONV). Nevertheless, PONV remains a continuing problem with an average incidence of 20–30%. This paper should provide essential information for the design, conduct, and presentation of these studies. It should also increase comparability among future studies and help clinicians in assessing and reading the literature on PONV. First, future studies should address new and relevant questions instead of repeatedly investigating prophylactically given antiemetics whose main results are predictable (e.g. already proven by meta-analysis). Second, group comparability should be based on well-proven risk factors and a simplified risk score for predicting PONV. Endless listings of doubtful risk factors should be avoided. Third, a realistic sample size estimation should be performed, i.e. in most cases at least 100 patients per group are necessary. Fourth, nausea, vomiting and rescue medication should be recorded and reported separately with the corresponding incidences (and number of patients with these separate symptoms), and the main end-point should be PONV. The entire observation period should cover 24 h. Additional reporting of the early (0–2 h) and delayed (2–24 h) postoperative period is desirable and should consider single and cumulative incidences. Lastly, interpretation of results should take into account the study hypothesis, sources of potential bias or imprecision, and the difficulties associated with multiplicity of analysis and outcomes.

Skin conductance correlates with perioperative stress.

Abstract: Background: Skin conductance (SC) as a measure of emotional state or arousal may be a tool for monitoring surgical stress in anaesthesia. When an outgoing sympathetic nervous burst occurs to the skin, the palmar and plantar sweat glands are filled up, and the SC increases before the sweat is removed and the SC decreases. This creates a SC fluctuation. The purpose of this study was to measure SC during laparoscopic cholecystectomy with propofol and remifentanil anesthaesia and to evaluate whether number and amplitude of SC fluctuations correlate with perioperative stress monitoring. Methods: Eleven patients were studied nine times before, during and after anaesthesia. SC was compared to changes in stress measures such as blood pressure, heart rate, norepinephrine and epinephrine levels. SC was also compared to changes in Bispectral index (BIS). Results: The blood pressure, epinephrine levels and norepinephrine levels were positively correlated with both the number (P < 0.001) and amplitude (P < 0.01) of the SC fluctuations. Moreover, the BIS was positively correlated with the number (P < 0.001) and amplitude (P < 0.001) of the SC fluctuations. Furthermore, during tracheal intubation, the mean levels of the number of SC fluctuations from the 11 patients had the same stress response as measured in changes of the mean levels of norepinephrine. The mean BIS did not show any stress response during tracheal intubation. Conclusion: Number of SC fluctuations may be a useful method for monitoring the perioperative stress.

Immune response in asymptomatic smokers.

Abstract: Background: It has been demonstrated that cigarette smoking affects the immune system. Impairment of alveolar mononuclear cell function, described previously, may contribute to the higher rate of postoperative respiratory infections. However, increased susceptibility of smokers to infections of other origin (e.g. wound-related) implies that tobacco effect is not restricted to the respiratory immune competent cells. The present study was designed to investigate the systemic effect of tobacco smoking as it exerted on blood-derived immune cells. We measured systemic cytotoxic activity of natural killer cells, production of pro- and anti-inflammatory cytokines by blood mononuclear cells and their proliferation in response to mitogens. To minimize the immunosuppressive effect of other smoke-related factors, the smokers with chronic obstructive pulmonary disease (COPD) were excluded from this study. Methods: Peripheral blood mononuclear cells (PBMC) from 24 chronic asymptomatic smokers, and 28 controls, age and gender matched, were isolated and incubated in vitro with lipopolysaccharide (LPS) or phytohemagglutinin (PHA) to induce secretion of IL-1β, IL-1ra, IL-6, IL-10, TNFα and IL-2, respectively, from mononuclear cells. The level of the cytokines in the supernatants was measured using ELISA kits. The proliferative response to the mitogens PHA and concanavalin A (ConA) was evaluated by 3H-thymidine incorporation and NK cell cytotoxicity by 51Cr release assay. Results: Mononuclear cells from smokers showed increased production of the pro-inflammatory cytokines IL-1β, IL-6 and TNFα and enhanced proliferative response to mitogens as compared to non-smoking population. The secretion of IL-2 and the anti-inflammatory cytokines IL-1ra and IL-10 was similar in both groups. NK cell cytotoxic activity was suppressed in the smokers. Conclusion: Cigarette smokers without chronic obstructive pulmonary disease (COPD) exhibit impaired NK cytotoxic activity in peripheral blood and unbalanced systemic production of pro- and anti-inflammatory cytokines. These changes may serve as predisposing factors for respiratory and systemic infections in the postoperative period and should alert an anesthetist during perioperative management.

Victims of awareness

Abstract: Background: Intraoperative awareness with explicit recall may be followed by long-lasting mental symptoms. However, the average risk for developing mental sequelae after awareness, and the average severity and the duration of symptoms has not previously been illustrated in a consecutive series of awareness cases. Methods: Nine patients among 18 consecutive, prospectively identified cases of intraoperative awareness with recall could be located after approximately 2 years and agreed to an interview about possible persisting problems. Results: Four of the nine interviewed patients were still severely disabled due to psychiatric/psychological sequelae. All of these patients had experienced anxiety during the period of awareness, but only one had complained about pain. Another three patients had less severe, transient mental symptoms, although they could cope with these in daily life. Two patients denied any sequelae from their awareness episode. Conclusions: Up to 3 weeks after their unsuccessful anesthetic, repeated information and discussions had been offered. Despite the fact that all patients at that time claimed to be satisfied with this management, and eventually considered no further contacts necessary, this was obviously inaccurate. Therefore, professional psychiatric assessment, treatment and long-term follow-up should constitute standard practice for all patients who have experienced intraoperative awareness.

Dimenhydrinate for prophylaxis of postoperative nausea and vomiting: a meta-analysis of randomized controlled trials

Abstract: Background: Diphenhydramine and its theoclate salt dimenhydrinate are traditional antiemetics still in use. However, so far the quantitative effect of dimenhydrinate in the prophylaxis of postoperative nausea and vomiting (PONV) has not been evaluated systematically. Methods: Results from randomized controlled trials investigating the efficacy of dimenhydrinate vs. a control to prevent PONV were included in a meta-analysis. Studies were systematically searched through MEDLINE, EMBASE, the Cochrane-Library, manually screening of reference lists of matching review articles and current issues of locally available peer-reviewed anesthesia journals, up to June 2001. The numbers of patients with complete absence of PONV within 6 h and within 48 h after surgery were extracted as the main end point. Pooled relative benefits (RB) and numbers-needed-to-treat (NNT) with their corresponding 95% confidence intervals (CI) were calculated using a random effects model. This quantitative systematic review was performed following the recommendations of the QUORUM statement. In all, 18 trials with 3045 patients were included in the analysis: 1658 patients received a placebo (control) and 1387 patients received dimenhydrinate. Results: The RB to stay completely free of PONV was 1.2 (95% CI: 1.1–1.4) for the early period (NNT = 8; 95% CI: 5–25) and 1.5 (1.3–1.8) for the overall investigated period (NNT = 5; 95% CI: 3–9). Conclusion: Dimenhydrinate is a traditional and inexpensive antiemetic with an efficacy that might be considered as clinically relevant. Although in use for a long time, the dose–response, precise estimation of side-effects, optimal time of administration and the benefit of repetitive doses still remain unclear.

Tranexamic acid given intraoperatively reduces blood loss after total knee replacement: a randomized, controlled study.

Abstract: Background: Extensive blood loss in total knee replacement (TKR) surgery is well known and is associated with a high transfusion rate of allogenic blood. Tranexamic acid (TXA) has been shown to reduce blood loss by 50% in this patient group, but only in cases with a perioperative loss of 1400–1800 ml. This study was performed to see if TXA offers any advantages in knee replacement surgery with blood loss at 800 ml. Methods: Thirty consecutive patients scheduled for TKR in spinal anesthesia with the use of a tourniquet, were randomized to TXA or non-TXA. Tranexamic acid 10 mg kg−1 was given at conclusion of surgery and again 3 h later. Blood loss was registered. Results: Total blood loss was at all times significantly lower in the TXA group compared to the non-TXA group (409.7±174.9 ml vs. 761.7±313.1 ml; P<0.001). There were no differences in coagulation parameters. No patients in the TXA group had a blood transfusion vs. 13% in the non-TXA group (NS). No complications were registered in the two groups. Conclusion: We conclude that TXA significantly reduces blood loss after total knee replacement surgery.

Effects of lung recruitment maneuver and positive end-expiratory pressure on lung volume, respiratory mechanics and alveolar gas mixing in patients ventilated after cardiac surgery.

Abstract: Background: It is unclear whether positive end-expiratory pressure (PEEP) is needed to maintain the improved oxygenation and lung volume achieved after a lung recruitment maneuver in patients ventilated after cardiac surgery performed in the cardiopulmonary bypass (CPB). Methods: A prospective, randomized, controlled study in a university hospital intensive care unit. Sixteen patients who had undergone cardiac surgery in CPB were studied during the recovery phase while still being mechanically ventilated with an inspired fraction of oxygen (FiO2) 1.0. Eight patients were randomized to lung recruitment (two 20-s inflations to 45 cmH2O), after which PEEP was set and kept for 2.5 h at 1 cmH2O above the pressure at the lower inflexion point (14±3 cmH2O, mean ±SD) obtained from a static pressure-volume (PV) curve (PEEP group). The remaining eight patients were randomized to a recruitment maneuver only (ZEEP group). End-expiratory lung volume (EELV), series dead space, ventilation homogeneity, hemodynamics and PaO2 (oxygenation) were measured every 30 min during a 3-h period. PV curves were obtained at baseline, after 2.5 h, and in the PEEP group at 3 h. Results: In the ZEEP group all measures were unchanged. In the PEEP group the EELV increased with 1220±254 ml (P<0.001) and PaO2 with 16±16 kPa (P<0.05) after lung recruitment. When PEEP was discontinued EELV decreased but PaO2 was maintained. The PV curve at 2.5 h coincided with the curve obtained at 3 h, and both curves were both steeper than and located above the baseline curve. Conclusions: Positive end-expiratory pressure is required after a lung recruitment maneuver in patients ventilated with high FiO2 after cardiac surgery to maintain lung volumes and the improved oxygenation.

Post-operative analgesia following total knee replacement: an evaluation of the addition of an obturator nerve block to combined femoral and sciatic nerve block.

Abstract: Background: Femoral and sciatic nerve block may not provide complete post-operative analgesia following total knee replacement. This study was designed to evaluate whether the addition of an obturator nerve block to combined femoral and sciatic nerve block improves the quality of post-operative analgesia following primary total knee replacement. Methods: Sixty patients were randomised into one of two groups: combined femoral and sciatic nerve block with 15 ml 0.75% ropivacaine to each nerve or combined femoral and sciatic nerve block with 15 ml 0.75% ropivacaine to each nerve and an obturator nerve block with 5 ml 0.75% ropivacaine. Results: Peripheral nerve blocks were successful in 85% of patients. The group which received the obturator nerve block showed a significant increase in the time until their first request for analgesia (mean 257.0 vs. 433.6 min) and a significant reduction in the total requirements for morphine throughout the study period (mean 83.8 vs. 63.0 mg) (P<0.05). There were no systemic or neurological sequelae in any of the groups. Conclusions: The addition of an obturator nerve block to femoral and sciatic blockade improved post-operative analgesia following total knee replacement.

Small-volume resuscitation: from experimental evidence to clinical routine. Advantages and disadvantages of hypertonic solutions.

Abstract: Background: The concept of small-volume resuscitatioin (SVR) using hypertonic solutions encompasses the rapid infusion of a small dose (4 ml per kg body weight, i.e. approximately 250 ml in an adult patient) of 7.2–7.5% NaCl/colloid solution. Originally, SVR was aimed for initial therapy of severe hypovolemia and shock associated with trauma. Methods: The present review focusses on the findings concerning the working mechanisms responsible for the rapid onset of the circulatory effect, the impact of the colloid component on microcirculatory resuscitation, and describes the indications for its application in the preclinical scenario as well as perioperatively and in intensive care medicine. Results: With respect to the actual data base of clinical trials SVR seems to be superior to conventional volume therapy with regard to faster normalization of microvascular perfusion during shock phases and early resumption of organ function. Particularly patients with head trauma in association with systemic hypotension appear to benefit. Besides, potential indications for this concept include cardiac and cardiovascular surgery (attenuation of reperfusion injury during declamping phase) and burn injury. The review also describes disadvantaages and potential adverse effects of SVR: Conclusion: Small-volume resuscitation by means of hypertonic NaCl/colloid solutions stands for one of the most innovative concepts for primary resuscitation from trauma and shock established in the past decade. Today the spectrum of potential indications envolves not only prehospital trauma care, but also perioperative and intensive care therapy.

Compensatory fluid administration for preoperative dehydration--does it improve outcome?

Abstract: Background: Preoperative fasting may lead to a fluid deficit of about 1 litre, which may contribute to perioperative discomfort and morbidity. We therefore examined the association between perioperatively administered fluids aiming to correct dehydration and clinical outcome. Methods: Review of randomized, controlled, clinical trials evaluating clinical outcome, in which fluid versus no fluid was administered pre- or intraoperatively, attempting to correct preoperative fluid deficits. Data were obtained from a Medline search (1966–2001), and references cited in original papers. Seventeen trials met the inclusion criteria. Results: Based on the amount of fluid administered, we divided the studies into two groups. In nine studies, fluid administration was <1 litre, and in eight studies ≥1 litre of fluid was administered. Administration of low-dose fluid reduced preoperative thirst, but the limited data do not allow conclusions on postoperative outcome such as nausea, vomiting, headache and pain. Administration of ≥1 litre fluid generally reduced postoperative drowsiness and dizziness, while the effects on postoperative nausea, vomiting and thirst has not been clarified. Conclusion: Fluid administration to compensate preoperative dehydration improves symptoms related to dehydration. Based on the available data, administration of about 1 litre fluid pre- or intraoperatively in patients having fasted for minor surgical procedures seems rational.

Prehospital advanced life support provided by specially trained physicians: is there a benefit in terms of life years gained?

Abstract: Background: The benefit of prehospital advanced life support (ALS) is disputed, as is the prehospital use of specially trained, hospital-based physicians. The purpose of the study was to assess the health benefit from an anesthesiologist-manned prehospital emergency medical service (EMS), and to separate the benefit of the anesthesiologist from that of rapid transport. Methods: The anesthesiologist-manned helicopter and rapid response car service at Rogaland Central Hospital assisted 1106 patients at the scene during the 18-month study period. Two expert panels assessed patients with a potential health benefit for life years gained (LYG) using a modified Delphi technique. The probability of survival as a result of the studied EMS was multiplied by the life expectancy of each patient. The benefit was attributed either to the anesthesiologist, the rapid transport or a combination of both. Results: The expert panels estimated a benefit of 504 LYG in 74 patients (7% of the total study population), with a median age of 54 years (range 0–88). The cause of the emergency was cardiac diseases (including cardiac arrest) in 61% of the 74 pa

Volume-targeted therapy of increased intracranial pressure: the Lund concept unifies surgical and non-surgical treatments.

Abstract: Opinions differ widely on the various treatment protocols for sustained increase in intracranial pressure (ICP). This review focuses on the physiological volume regulation of the intracranial compartments. Based on these mechanisms we describe a protocol called 'volume-targeted' ('Lund concept') for treatment of increased ICP. The driving force for transcapillary fluid exchange is determined by the balance between effective transcapillary hydrostatic and osmotic pressures. Fluid exchange across the intact blood-brain barrier (BBB) is counteracted by the low permeability to crystalloids (mainly Na+ and Cl-) combined with the high osmotic pressure (5500 mmHg) on both sides of the BBB. This contrasts to most other capillary regions where the osmotic pressure is mainly derived from the plasma proteins (approximately 25 mmHg). Accordingly, the level of the cerebral perfusion pressure (CPP) is of less importance under physiological conditions. In addition cerebral intracapillary hydrostatic pressure (and cerebral blood flow) is physiologically tightly autoregulated, and variations in systemic blood pressure are generally not transmitted to these capillaries. If the BBB is disrupted, transcapillary water transport will be determined by the differences in hydrostatic and colloid osmotic pressure between the intra- and extracapillary compartments. Under these pathological conditions, pressure autoregulation of cerebral blood flow is likely to be impaired and intracapillary hydrostatic pressure will depend on variations in systemic blood pressure. The volume-targeted 'Lund concept' can be summarized under four headings: (1) Reduction of stress response and cerebral energy metabolism; (2) reduction of capillary hydrostatic pressure; (3) maintenance of colloid osmotic pressure and control of fluid balance; and (4) reduction of cerebral blood volume. The efficacy of the protocol has been evaluated in experimental and clinical studies regarding the physiological and biochemical (utilizing intracerebral microdialysis) effects, and the clinical experiences have been favorable.

Postoperative muscle paralysis after rocuronium: less residual block when acceleromyography is used.

Abstract: Background: Residual muscle paralysis after anesthesia is common after pancuronium, but less common following the intermediate-acting drugs vecuronium and atracurium. Therefore, many anesthetists do not monitor neuromuscular function when using an intermediate-acting agent. The purpose of this prospective, randomised and double-blind study was to establish the incidence and degree of postoperative residual block following the use of rocuronium in patients not monitored with a nerve stimulator, and to compare it with results obtained in patients monitored using acceleromyography (AMG). Methods: During propofol/opioid anesthesia, 120 adult patients were randomised to two groups, one monitored with AMG, the other using only clinical criteria without a nerve stimulator. Postoperatively, TOF-ratio was measured with mechanomyography; a TOF-ratio < 0.80 indicated residual muscle paralysis. Results: Residual muscle paralysis was found in 10 patients in the group without neuromuscular monitoring (16.7%) (95% confidence interval, 12–21%) and in two patients in the AMG-monitored group (3%) (95% CI, 0–8%); (P = 0.029, Fisher's exact test). Time from end of surgery to tracheal extubation was significantly longer in the AMG-monitored group (12.5 min) than in the group not monitored with AMG (10 min). Conclusion: Clinical evaluation of recovery of neuromuscular function does not exclude significant residual paralysis following the intermediate-acting muscle relaxant rocuronium, but the problem of residual block can be minimized by use of AMG.

Procalcitonin and neopterin as indicators of infection in critically ill patients.

Abstract: Background: In critically ill patients, severe infection and systemic inflammation due to non-infectious causes produce very similar clinical presentations, and traditional infection markers do not always differentiate these two conditions. Both procalcitonin and neopterin have been suggested to aid in the early diagnosis of bacterial infections and in differentiating bacterial infections from systemic inflammatory, non-infectious diseases or from viral infections. Methods: Procalcitonin (PCT) and neopterin were analyzed in 208 ICU patients who developed acute fever or septic shock. Blood samples were taken every 8th h within 48 h of the onset of fever or septic shock. Results: A total 162/208 of patients had infection, the most common location being the respiratory tract. Mortality was higher in infected patients (31.4% vs. 10.9%; P < 0.01). The optimum cut-off levels in identifying patients with infection of daily peak PCT were 0.8 µg/L on day 1 and 0.9 µg/L on day 2, and both sensitivity (67.7% and 60.9%, respectively) and specificity (47.8% and 63%) were poor. Accordingly, the optimum cut-off values of peak neopterin were 18 and 16 pg/L. The sensitivity was 62.7% on day 1 and 69.3% on day 2, while specificity was correspondingly 78.3% and 67.9%. There were no significant differences between the markers in discriminating between patients with infection or inflammation. Both PCT and neopterin increased with the severity of infection. They were higher in non-survivors. Conclusion: PCT and neopterin were equally effective, although not very accurate in differentiating between infection and inflammation in critically ill patients. Neopterin was more specific than PCT, suggesting that neopterin is related to the activity of inflammatory response.

Postoperative pain relief following intrathecal bupivacaine combined with intrathecal or oral clonidine.

Abstract: Background: The purpose of the present study was to evaluate the postoperative analgesic and adverse effects of equal doses of oral or intrathecal clonidine in spinal anaesthesia with bupivacaine p ...

Detecting postoperative urinary retention with an ultrasound scanner.

Abstract: Background: Retention of urine is a common postoperative problem associated with risk of overdistention and permanent detrusor damage. Prevention of urinary retention by insertion of indwelling catheter may increase the risk of urinary infection. We have performed a reliability test of an ultrasound scanner, implemented in the postoperative monitoring equipment. Methods: Patients were monitored after different types of surgery under spinal anesthesia with an ultrasound scanner in the postanesthesia care unit (PACU). Patients: Patients who according to current guidelines required a urinary bladder catheter, were scanned before a catheter was inserted and urine volume was measured. These two urine volumes were compared and analyzed for agreement. Results: Nineteen female and 17 male patients were included. The mean difference between ultrasound estimates and catheter urine volume measurements was − 21.5 mL, and limits of agreement, calculated as a 95% confidence interval, were − 147 and + 104 mL. This means that the urine volume estimated by ultrasound was on average 21.5 mL smaller than the urine volume when the bladder was emptied. Conclusion: This study confirms a good agreement between the ultrasound scanner estimates of urinary bladder volume and urine volume measured after emptying the bladder. Nurses in the PACU could operate the ultrasound scanner after a brief instruction and training period. Considering the potentially serious long-term consequences of undiagnosed postoperative urinary retention, introducing this equipment for routine monitoring of urinary bladder volume should be considered.

Effects of propofol on cerebral blood flow and the metabolic rate of oxygen in humans.

Abstract: Background: Effects of propofol on human cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO 2 ), and blood flow-metabolism coupling have not been fully evaluated. We therefore assessed the effects of propofol on total-CBF and CMRO 2 in patients without noxious stimuli and neurologic disorders. Methods: General anesthesia was induced with midazolam (0.2 mg/kg) and fentanyl (5μg/kg) in 10 patients (ASA physical status I) undergoing knee joint endoscopic surgery. Epidural anesthesia was also performed to avoid noxious stimuli during surgery. Cerebral blood flow (CBF) and cerebral arteriovenous oxygen content difference (a-vDO 2 ) was measured using the Kety-Schmidt method with 15% N 2 O as a tracer before and after propofol infusion (6mg/kg/h for 40min), and the CMRO 2 was also calculated. Results: CBF decreased following propofol infusion from 34.4 ml/100g/min (range 28.4-52.0) to 30.0ml/100g/min (range 20.2-42.4) (P=0.04). Although there was no significant change in a-vDO 2 , CMRO 2 decreased following propofol infusion from 2.7ml/100g/min (range 2.2-4.3) to 2.2ml/100g/min (range 1.4-3.0) (P=0.04). There was a strong linear correlation between CBF and CMRO 2 (r=0.90). Conclusion: Propofol proportionally decreased CBF and CMRO 2 without affecting a-vDO 2 in humans, suggesting that normal cerebral circulation and metabolism are maintained.

Evaluation of remifentanil as single drug for awake fiberoptic intubation

Abstract: Background: Awake fiberoptic intubation is the standard of care for difficult airway management. Quality and success of this technique depend on the experience of the intubating physician and the proper preparation of the patient. The aim of this study was to compare remifentanil (R) as single agent to the combination of fentanyl (F) and midazolam (M), which have been the drugs for analgesia and sedation for this procedure. Methods: Seventy-four adult patients requiring nasotracheal intubation were randomly assigned to one of two groups. In group I, (n=37) R was administered in incremental dosages (0.1–0.25–0.5 µg/kg/min) by an infusion pump according to comfort, level of sedation and respiratory depression. In group II, (n=37) analgesia and sedation was achieved by F 1.5 µg/kg and doses of between 1 and 10 mg M, titrated to the individual needs. Patient reactions like grimacing, movement and coughing during intubation were assessed, as well as patient recall of the procedure. Haemodynamic and respiratory parameters were continuously recorded. Results: Group I patients better tolerated nasal tube passage (P<0.001) and laryngeal tube advancement (P<0.001) than group II. Remifentanil better suppressed hemodynamic response to nasal intubation (P<0.001). No significant difference in respiratory data was recorded. In group I more recall of the procedure was observed (six vs. zero patients, P<0.05). Conclusion: Remifentanil in high doses, as the single agent for patient preparation for awake fiberoptic intubation seems to improve intubating conditions, quality and reliability of the procedure. However, a higher incidence of recall is to be expected.

The influence of anaesthesia and surgery on the circadian rhythm of melatonin.

Abstract: Background: Operations are typically associated with sleep and other circadian rhythm disturbances. The present study was set up to evaluate the influence of spinal and general anaesthesia associated with knee surgery on the circadian rhythm of melatonin, which has sleep inducing properties. Previously this context has been studied only in some invasive operations and it might be that general anaesthesia induces more disturbances on circadian rhythm of melatonin than operations done with patients awake. Methods: The circadian secretion pattern of melatonin was monitored during the pre- and postoperative evenings, nights and mornings to clarify possible anaesthesia/surgery-induced changes in the nocturnal secretion of melatonin and in the phase of the melatonin rhythm. The study included 20 patients scheduled for minor orthopaedic operations. The patients were randomised to receive either spinal or general anaesthesia. Melatonin was measured from evening and morning saliva samples radioimmunologically. The nocturnal urine before and after surgery was radioimmunologically examined for 6-hydroxymelatonin sulphate. Results: Melatonin secretion evaluated from the saliva samples was significantly diminished during the first postoperative evening as compared with that during the preoperative evening (P<0.001). There was also a significant decline of 26% (P<0.05) in postoperative 6-hydroxymelatonin sulphate excretion. There was no significant difference in melatonin secretion between the spinal and general anaesthesia groups. Conclusion: Our findings suggest that anaesthesia in conjunction with surgery acutely disturbed the normal circadian rhythm of melatonin by delaying the onset of nocturnal melatonin secretion.

Intensive care unit syndrome/delirium is associated with anemia, drug therapy and duration of ventilation treatment.

Abstract: BACKGROUND: We have performed a prospective qualitative investigation of the ICU syndrome/delirium; the main parts of which have recently been published. The aim of the present study was to explore the relationship between the ICU syndrome/delirium and age, gender, length of ventilator treatment, length of stay and severity of disease, as well as factors related to arterial oxygenation and the amount of drugs used for sedation/analgesia. METHODS: Nineteen mechanically ventilated patients who had stayed in the ICU for more than 36 h were closely observed during their stay, and interviewed in depth twice after discharge. Demographic, administrative and medical data were collected as a part of the observation study. RESULTS: Patients with severe delirium had significantly lower hemoglobin concentrations than those with moderate or no delirium (P=0.033). Patients suffering from severe delirium spent significantly longer time on the ventilator and at the ICU, and were treated with significantly higher daily doses of both fentanyl (P=0.011) and midazolam (P=0.011) in comparison with those reporting only moderate or no symptoms of delirium. There were no significant differences in the Therapeutic Intervention Scoring System scores, reflecting the degree of illness, between patients with and without delirium. CONCLUSION: The development of the ICU syndrome/delirium seems to be associated with decreased hemoglobin concentrations and extended times on the ventilator. Prolonged ICU stays and treatment with higher doses of sedatives and opioids in patients with delirium appear to be secondary phenomena rather than causes.

Serum concentration of S‐100 protein in assessment of cognitive dysfunction after general anesthesia in different types of surgery

Abstract: Background: S-100 protein serum concentration (S-100) serves as a marker of cerebral ischemia in cardiac surgery, head injury and stroke. In these circumstances S-100 corresponds well with the results of neuropsychological tests. The aim of the present study was to investigate the value of S-100 and neuron specific enolase (NSE) in reflecting postoperative cognitive deficit (POCD) after general surgical procedures. Methods: One hundred and twenty patients undergoing vascular, trauma, urological or abdominal surgery were investigated. Serum values of S-100 and NSE were determined preoperatively and 0.5, 4, 18 and 36 h postoperatively. Neuropsychological tests for detecting POCD were performed preoperatively and on day 1, 3, and 6 after the operation. A decline of more than 10% in neuropsychological test results was regarded as POCD. Furthermore, we retrospectively compared the S-100 in patients with and without POCD in different types of surgery. Results: According to our definition, forty -eight patients had POCD (95% confidence interval: 37.5–58.5). These patients showed higher serum concentrations of S-100 (median 024 ng/ml; range 0.01–3.3 ng/ml) compared with those without POCD (n=69; median 0.14 ng/ml; range 0–1.34 ng/ml) 30 min postoperatively (P=0.01). Neuron specific enolase was unchanged during the course of the study. Differences of S-100 in patients with and without POCD were found in abdominal and vascular surgery but not in urological surgery. Conclusion: When all patients are pooled, S-100 appears to be suitable in the assessment of incidence, course and outcome of cognitive deficits. We suspect that in some surgical procedures, such as urological surgery, S-100 appears to be of limited value in detecting POCD. Neuron specific enolase did not reflect neuropsychological dysfunction after noncardiac surgery.

Extubation after breathing trials with automatic tube compensation, T-tube, or pressure support ventilation.

Abstract: BACKGROUND: Automatic tube compensation (ATC) is a new option to compensate for the pressure drop across the endotracheal or tracheostomy tube (ETT), especially during ventilator-assisted spontaneous breathing. While several benefits of this mode have so far been documented, ATC has not yet been used to predict whether the ETT could be safely removed at the end of weaning, from mechanical ventilation. METHODS: We undertook a systematic trial using a randomized block design. During a 2-year period, all eligible patients of a medical intensive care unit were treated with ATC, conventional pressure support ventilation (PSV, 5 cmH2O), or T-tube for 2-h. Tolerance of the breathing trial served as a basis for the decision to remove the endotracheal tube. Extubation failure was considered if reintubation was necessary or if the patient required non-invasive ventilatory assistance (both within 48 h). RESULTS AND CONCLUSIONS: After the inclusion of 90 patients (30 per group) we did not observe significant differences between the modes. Twelve patients failed the initial weaning trial. However, half of the patients who appeared to fail the spontaneous breathing trial on the T-tube, PSV, or both, were successfully extubated after a succeeding trial with ATC. Extubation was thus withheld from four and three of these patients while breathing with PSV or the T-tube, respectively, but to any patient breathing with ATC. It seems that ATC can be used as an alternative mode during the final phase of weaning from mechanical ventilation. Furthermore, this study may promote a larger multicenter trial on weaning with ATC compared with standard modes.

Accuracy of point-of-care-testing (POCT) for determining hemoglobin concentrations.

Abstract: Background: While point-of-care testing (POCT) is being used increasingly as a basis for deciding on perioperative erythrocyte transfusion, no valid standards currently exist concerning the accuracy of Hb concentration measurements. For clinical employment, however, the confidence limits (±2 SD) of these measurements should lie close to 5 g/l. The aim of the present study was to evaluate the accuracy and precision of point-of-care testing for blood hemoglobin concentration (cHb in g/l) measurements in critically ill patients. Methods: Fifty blood samples from 50 postoperative patients requiring intensive care treatment were withdrawn from a cannula in the radial artery into a 2-ml heparinized syringe (containing wet sodium heparinate in the conus), in a 2-ml Monovette with 50 IE lithium heparinate, and into a 2.7-ml cuvette with 1.6 mg potassium EDTA/ml blood. The POCT battery consisted of two blood gas analyzers (ABLTM 625 and 725, Radiometer, Copenhagen), the HemoCue® system (Mallinckrodt Medical, Germany), and an automated hematology analyzer (M-2000®, Sysmex, Germany). The cyanmethemoglobin method served as the reference ‘gold standard’ procedure. The blood gas analyzer and HemoCue® systems were tested using dry and wet heparinized blood samples. Results: Hemoglobin concentrations of the reference measurements ranged from 73.9 to 159.4 g/l. The automated hematology analyzer method did reveal a small but systematic deviation for higher cHb values. For the blood gas analyzer and HemoCue® system procedures there was no systematic deviation of bias for either the first measurement or the averaged data. Bland & Altman analysis revealed a larger scattering for the wet heparinized samples. Conclusions: The above-stated requirement for POCT systems, i.e. that the confidence limits should lie close to 5 g/l cHb, held true for the dry heparinized samples of the blood gas analyzer (1st measurement and mean of 2), the HemoCue® system (mean of 3) and the automated hematology analyzer.

Ultrasound-guided central venous cannulation in infants and children.

Abstract: Background: Percutaneous central venous cannulation in infants and children is a challenging procedure. Traditionally, an external landmark technique has been used to identify puncture site. An ultrasound-guided technique is now available and we wanted to evaluate this method in children and infants, looking specifically at the ease of use, success rate and complications. Methods: Forty-two consecutive infants and children (median 16.5 [0–177] months and 10 [3–45] kg) scheduled for central venous catheter placement were registered. An ultrasound scanner made for guiding puncture of vessels was used. After locating the puncture site, a sterile procedure was performed using an accompanying kit to aid puncture of the vessel. Results: Cannulation was successful in all patients and we had no complications during insertion of the catheters. The right internal jugular vein was preferred in most patients, and in 95% of the patients the vein was punctured at the first attempt. The median time from start of puncture to aspiration of blood was 12 (3–180) seconds. Conclusion: The ultrasound-guided technique for placement of central venous catheters was easy to apply in infants and children. It is our impression that it increased the precision and safety of the procedure in this group of patients.

No enhancement of sensory and motor blockade by ketamine added to ropivacaine interscalene brachial plexus blockade.

Abstract: Background: Ketamine can enhance anesthetic and analgesic actions of a local anesthetic via a peripheral mechanism. The authors' goal was to determine whether or not ketamine added to ropivacaine in interscalene brachial plexus blockade prolongs postoperative analgesia. In addition, we wanted to determine the incidence of adverse-effects in patients undergoing hand surgery. Methods: Sixty adults scheduled for forearm or hand surgery under the interscalene brachial plexus block were prospectively randomized to receive one of the solutions of the study. Group P received 0.5% ropivacaine 30 ml, group K received 0.5% ropivacaine 30 ml with 30 mg ketamine, and group C received 0.5% ropivacaine with 30 mg ketamine i.v. Loss of shoulder abduction, elbow flexion, wrist flexion and loss of pinprick in the C4–7 sensory dermatomes were assessed at 1-min intervals. Adverse-effects were assessed every 5 min. The duration of the sensory and motor blocks was assessed after operation. Adverse-effects were also recorded. Results: The onset time of sensory or motor blockade and the duration of sensory or motor blockade were similar in all groups. Adverse-effects occurred in 44% of patients in group K and 94% of group C. Conclusion: This study suggests that 30 mg ketamine added to ropivacaine in the brachial plexus block does not improve the onset or duration of sensory block, but it does cause a relatively high incidence of adverse-effects. These two findings do not encourage the use of ketamine with local anesthetics for brachial plexus blockade.

Pulse contour analysis versus thermodilution in cardiac surgery patients.

Abstract: Background: Previous studies have demonstrated that there is a lack of agreement between intermittent cold bolus thermodilution (ICO) and a semicontinuous method with dilution of heat (CCO) in cardiac surgical patients following hypothermic extracorporeal circulation (HCPB). Therefore, the aim of the present study was to compare both ICO and CCO with continuous pulse contour analysis (PCCO): a method based on a fundamentally different principle of determining cardiac output (CO). Methods: A prospective criterion standard study of 25 cardiac surgery patients undergoing HCPB. Cardiac output was determined using the three methods (ICO, CCO, and PCCO) before and after HCPB up to 12 h after arrival on the ICU. Bias and precision were evaluated. Results: A total of 380 triple determinations of CO could be analyzed. During the entire study period bias PCCO-ICO was −0.14 l*/min (precision 1.16 l*/min) and bias CCO-ICO was −0.40 l*/min (precision 1.25 l*/min). Up to 45 min after bypass PCCO agreed with ICO (bias −0.21 l*/min, precision 1.37 l*/min), while bias CCO-ICO was −1.30 l*/min (precision 1.45 l*/min). Conclusion: The agreement between PCCO and ICO in contrast to CCO in the first 45 min after HCPB indicates that CCO underestimates CO during this period.

Impact factor bias and proposed adjustments for its determination.

Abstract: Background: The impact factor (IF), a qualitative parameter used to evaluate scientific journals, has several flaws. The aim of the study was to evaluate two of its important constraints, journal self-citation and scientific field, and to investigate the potential for improvement. Methods: We studied the five or six highest impact journals from each of seven medical fields: anesthesiology, dermatology, genetics and heredity, immunology, general and internal medicine, ophthalmology and surgery. To correct for journal self-citation, we divided the number of 1998 citations of papers published in 1996 and 1997, minus the self-citations, by the number of papers published in the same period. For inter-field normalization we divided the IF by the mean of the IFs of the upper quartile for the same category of medical field (IF/fcat). Results: For the 36 journals, there was a negative correlation between IF and self-cited and self-citing rates (rs = −0.765, P < 0.001 and rs = −0.479, P < 0.003, respectively). Self-cited rate is the ratio of a journal's self-citations to the number of times it is cited by all journals including itself. Self-citing rate relates a journal's self-citations to the total references it makes. The IF/fcat for the 36 journals are positively correlated with their conventional IF (rs = 0.91, P < 0.001). Conclusion: Correcting the IF of the 36 journals for self-citation did not significantly change journal rankings. The adjusted IF/fcat to normalize for the scientific field was positively correlated with the conventional IF.

Interscalene brachial plexus block is superior to subacromial bursa block after arthroscopic shoulder surgery.

Abstract: Background: Arthroscopic shoulder surgery is often associated with severe postoperative pain. The results concerning subacromial bursa blockade (SUB) as a method of pain relief have been contradictory. We hypothesized that a SUB and interscalene brachial plexus block (ISB) would similarly reduce early postoperative pain and the need for oxycodone as compared to placebo (PLA). Methods: Forty-five patients scheduled for arthroscopic shoulder surgery were enrolled in this randomised, prospective study. The ISB and SUB blockades were performed with 15 ml of ropivacaine (5 mg/ml). In the PLA group, 15 ml of 0.9% saline was injected into the subacromial bursa. All patients received general anaesthesia. Results: The mean intravenously patient-controlled delivered oxycodone consumption during the first 6 h was significantly lower in the ISB group (6 mg) than in the SUB group (24.1 mg; P=0.001) or in the PLA group (27 mg; P<0.001). No significant differences were detected between the SUB and PLA groups (P=0.791). The postoperative pain scores during the first 4 h at rest and during the first 6 h on movement were significantly lower in the ISB group than in the SUB and PLA groups. Conclusion: After arthroscopic shoulder surgery SUB has a minor effect only on postoperative analgesia, whereas an ISB with low-dose ropivacaine effectively relieves early postoperative pain and reduces the need for opioids.