Summary

Background and objective: Crystalloid haemodilution has been widely found to enhance coagulation onset, but the duration of this effect has never been documented. Methods: Twelve healthy, consenting volunteers had a rapid infusion of 14 mL kg−1 of normal (0.9%) saline. Blood samples were taken, prior to (control), and immediately after (30 min) the rapid saline infusion was completed (30 min). They were then repeated at regular intervals up to 120 min. Haematocrit/platelet counts were taken to determine the degree of dilution and thrombelastograms, with and without platelet antagonists (ReoPro, Abciximab), were measured in all samples. Antithrombin levels were selectively measured. Results: The haematocrit and platelet count showed a rapid dilutional decrease at 30 min (mean of −12.2% and −14.4%, respectively), with values returning towards baseline within 15 min after finishing the infusion. There was a significantly faster onset of coagulation (decrease in r-time) in the post-infusion sample (30 min) compared to control (P < 0.05), again returning towards normal as the dilution effect was reversed. Similar thrombelastograms findings were evident in the plasma factor only group (platelets inhibited by ReoPro). Antithrombin levels changed in keeping with the haemodilution effect (P < 0.0001). There was a linear relationship between antithrombin and thrombelastograms r-time (P = 0.012). Conclusion: The faster onset of coagulation brought on by haemodilution return towards normal as the dilutional effect is reversed. This effect is mediated through plasma clotting factors. Of interest is the significant inverse correlation of the onset of coagulation increasing as the antithrombin levels decreased with dilution.

Summary

Background and objective: To examine the calibration of the prognostic system Acute Physiology and Chronic Health Evaluation Score (APACHE II) regarding hospital mortality and predicting weaning outcome after long-term mechanical ventilation of the lungs.

Methods: Prospective observational cohort study performed in a respiratory intensive care unit including 246 patients whose lungs were ventilated for 42.1 ± 37.8 (median 30) days in the referring hospital. APACHE II (24 h after admission to our respiratory intensive care unit) and the cause of respiratory failure, underlying disease, prior duration of mechanical ventilation and gender were recorded. The predictive power was evaluated with sensitivity and specificity for different cut-off points and summarized in a receiver operating characteristic curve.

Results: No difference was found between survivors (APACHE II 16.0 ± 4.3) and non-survivors (APACHE II 16.9 ± 5.1). In a mean time of 8.0 ± 10.3 days, 146 patients (59.3%) were successfully weaned (APACHE II 15.2 ± 3.5). One-hundred patients (40.7%) were considered unweanable (APACHE II 17.7 ± 5.3). Recalibration of APACHE II to predict weaning failure was possible, resulting in an area under the receiver operating characteristic curve (AUC) of 0.638. Furthermore the AUC improved to 0.723 by changing the weights of selected APACHE items and introducing external factors. Diagnostic accuracy fell from group with mechanical ventilation ≤25 days (AUC 0.770) to group with mechanical ventilation >50 days (AUC 0.517).

Conclusions: APACHE II did not predict hospital mortality after long-term mechanical ventilation of the lungs. Not the original APACHE II but a recalibrated and adapted APACHE II can be useful to predict weaning outcome in patients with less than 25 days of prior lung ventilation.

Summary

Background and objective: The exact change in circulating blood volume (BV) during general anaesthesia is still unknown because there is no standard method of evaluating BV. We evaluated the changes in BV by general anaesthesia using simple and easy estimation methods.

Methods: Fourteen patients scheduled for minor surgery under general anaesthesia were enrolled. Propofol and vecuronium bromide were used for the induction of anaesthesia, and anaesthesia was maintained with sevoflurane and nitrous oxide. Haematocrit (Hct), total protein concentration (TP), as well as colloid osmotic pressure (COP) measured using a colloid osmometer, were determined before anaesthesia, and 30, 60 and 90 min after the induction of general anaesthesia. BV was calculated using Allen's formula and the changes in Hct, TP and COP. The estimated BV was compared with directly measured BV using indocyanine green dilution method (BVICG).

Results: Hct, TP and COP significantly decreased after the induction of anaesthesia (Hct: 42.1–39.4%; TP: 7.3–6.9 g dL−1; COP: 23–19 mmHg). The calculated BV as well as BVICG significantly increased after induction of anaesthesia (calculated by COP: 4.13–5.03 L; BVICG: 4.54–5.56 L). The change rate in BV calculated by the change of COP was larger than other calculated BVs, and was approximated to the change rate in BVICG. After emergence from anaesthesia, all values tended to return to baseline.

Conclusions: General anaesthesia increases BV. The value of BV calculated from the change in COP was most changeable.

Background and objective To compare the effects on cardiovascular changes induced by tracheal intubation when small doses of either remifentanil or sufentanil are used in the presence of midazolam.

Methods Thirty normotensive, ASA physical status I–II patients, receiving general anaesthesia for major abdominal surgery, received an intravenous midazolam premedication (0.05 mg kg−1) 10 min before induction. They were randomly allocated to receive in a double-blind fashion an intravenous bolusofeither(a)remifentanil given as a bolus dose 1 μg kg−1 (n = 15), or else (b) sufentanil 0.1 μg kg−1 infused over 60s (n = 15). In each instance this loading dose was followed by a continuous intravenous infusion (0.1 μg kg−1 min−1 or 0.01 μg kg−1 min−1 of remifentanil or sufentanil, respectively). General anaesthesia was induced with propofol (2 mg kg−1), followed by atracurium besilate (0.5 mg kg−1) to facilitate tracheal intubation. Following intubation, the lungs were mechanically ventilated with a 60% nitrous oxide in oxygen mixture and a 1% inspired sevoflurane.

Results Arterial pressure and heart rate were recorded before induction of anaesthesia (baseline), immediately before intubation, immediately after tracheal intubation and every minute for the first five minutes thereafter. No differences in systolic and diastolic arterial pressures were observed between the two groups. At the end of the study period, systolic and diastolic pressures slightly decreased from preinduction values in both groups. Four patients in the remifentanil group (26%) and five patients in sufentanil group (33%) showed at least one systolic pressure value <90 mm Hg during the study period (P = not significant); however, the observed decreases in systolic pressure were transient and did not require treatment. Heart rate values were not affected by tracheal intubation in either group.

Conclusions In healthy normotensive patients without cardiovascular disease the use of a relatively small dose of either remifentanil or sufentanil after standard midazolam premedication results in a similar and clinically acceptable effectiveness in blunting the cardiovascular changes induced by tracheal intubation.

A number of methods exist by which the pH of local anaesthetic solutions may be increased. Most commonly, these require the addition of differing amounts of sodium bicarbonate solution according to the local anaesthetic drugs. Sodium bicarbonate (1%) was titrated against pH in six commonly used local anaesthetic solutions. Titration curves of pH and volume of sodium bicarbonate solution added are shown for this group of local anaesthetics. This study demonstrates that 1 mL of 1% sodium bicarbonate solution may be used to alkalinize this range of local anaesthetics without the risk of precipitation. We also conclude that Ropivacaine (at concentration 0.75% and 1.0%), is unsuitable for alkalinization since it precipitates at a pH of 6.0.

Summary

Background and objective: Inhalation induction with sevoflurane provides acceptable conditions for tracheal intubation. Opioids significantly decrease the alveolar concentration needed to achieve tracheal intubation. The purpose of this study was to determine the target concentration of remifentanil providing excellent conditions for tracheal intubation with sevoflurane at 1 minimum alveolar concentration without muscle relaxant. Methods: Twenty-four consecutive patients, aged 18–50 yr, ASA I or II, were studied. Induction of anaesthesia was performed with sevoflurane at age-adjusted minimum alveolar concentration. Remifentanil was simultaneously administered using target-controlled infusion with the Minto model. Target plasma concentration of remifentanil was selected for each patient according to an up-and-down method. Results: The mean target concentration of remifentanil for successful tracheal intubation was 3.3 ng mL−1 (95% confidence interval: 2.6–3.9 ng mL−1). Arterial pressure, heart rate and bispectral index did not increase after tracheal intubation in the group of patients with successful intubation. Conclusions: Remifentanil at 3.3 ng mL−1 together with sevoflurane at 1 minimum alveolar concentration provides excellent conditions for tracheal intubation in 50% of patients.

Summary

Background and objective: Continuous spinal anaesthesia and continuous epidural anaesthesia are both able to provide adequate postoperative pain relief. Combining local anaesthetics and opioids results in synergistic effects. The purpose of this randomized, prospective study was to compare quality of analgesia, side-effects and patient's satisfaction between spinal bupivacaine alone and epidural bupivacaine with sufentanil postoperatively.

Methods: Fifty-nine patients scheduled for hip arthroplasty were randomly assigned either to Group 1 receiving continuous spinal anaesthesia or Group 2 receiving continuous epidural anaesthesia. Postoperatively, those in Group 1 received a 1 mL bolus followed by a continuous infusion of 10 mL/24 h of bupivacaine 0.25%. Those in Group 2 received a 5 mL bolus of lidocaine 2%, followed by a continuous infusion of bupivacaine 0.25% with sufentanil 0.001 mg mL−1 at 4 mL h−1. Pain was measured using a verbal rating score and a visual analogue scale.

Results: Group 1 and Group 2 of 43.3% and 37.9% reported complete analgesia on the verbal rating score. No statistically significant difference was found in the visual analogue scale. Nausea and vomiting occurred significantly more often in Group 2. The patient satisfaction rates did not differ significantly.

Conclusions: Continuous spinal analgesia with bupivacaine alone and continuous epidural analgesia with bupivacaine/sufentanil are both effective for postoperative pain relief after hip replacement. Those patients in the epidural group reported better analgesia but had a higher rate of postoperative nausea and vomiting. Efficacy of pain therapy did not correlate with patient satisfaction.

Summary

Background and objective: The prognosis of diabetic patients after surgery remains controversial. Some suggest that the rates of death and complications today are almost identical in diabetic and non-diabetic patients within hospital stay or for 30 days postoperatively, whereas others suggest that diabetes still constitutes a major risk factor for both short-term (≤30 days) and long-term (>30 days) patients especially after major cardiac surgery. We examined the long-term postoperative mortality of diabetic patients undergoing major non-cardiac surgery to identify possible perioperative risk factors.

Methods: Data from 179 consecutive diabetic patients, who underwent major non-cardiac surgery at Herlev Hospital, Denmark, during a 12 month period, have been retrospectively analysed. Data were obtained from patient records and from The Danish National Health Register. The main outcome measure was postoperative mortality. Patients were followed for a maximum of 18 months.

Results: The median postoperative observation period was 10 months (range 0–18 months). Overall postoperative mortality was 24% (95% confidence interval (CI) 17–31%). One third of the fatalities occurred during the first 30 days. Ischaemic heart disease diagnosed before the operation was associated with an overall postoperative mortality of 44% (95% CI 29–58%), which was significantly (P < 0.03) higher than in diabetic patients without known cardiovascular disease. The major causes of death in 18 out of 39 (46%) patients were diseases of the cardiovascular system.

Conclusions: Diabetic patients undergoing major non-cardiac surgery seem to have a high mortality, often because of cardiovascular death. Future strategies should focus on implementing cardio-protective treatment during the perioperative period.

Background and objective Hypothermia may alter the disposition of opioids. Because opioids are commonly used as analgesics in the postoperative period, it is of clinical interest to clarify whether perioperatively developed hypothermia affects postoperative opioid requirements.

Methods Fifty-nine patients undergoing subtotal hysterectomy were prospectively randomized and either treated intraoperatively with forced air warming, or served as controls covered with conventional blankets without active warming. Both groups received postoperative patient-controlled analgesia with the opioid ketobemidone. Total analgesic requirements, demands, analgesic requirements over 6-h intervals and pain scores were measured for 48 h. Core temperature at the tympanic membrane and ambient room temperature were measured during the perioperative period.

Results There were no postoperative differences in analgesic requirements or pain intensity between normothermic and hypothermic patients. Patients treated with warm air had an up to 1°C higher core temperature from 0.5 h after anaesthesia induction until almost 2 h postoperatively. The actively warmed patients also had a lower intraoperative blood loss than the hypothermic patients (186 ± 27 mL vs. 308 ± 47 mL; P < 0.05).

Conclusion In a clinical setting, opioid requirements do not seem to be affected by mild postoperative hypothermia after lower abdominal surgery.

The antioxidant capacity of plasma taken from 10 patients before and during propofol anaesthesia was measured. Mean total plasma antioxidant activity fell from 1.73 to 1.64 mM L−1 trolox equivalents (P=0.047). This was caused by haemodilution since mean haemoglobin concentration fell from 13.0 to 12.5 g dL−1 (P=0.016). The time to 50% haemolysis (H50) of 10% red blood cell suspensions induced by 2,2'azo-bis(2-am-idinopropane) dihydrochloride (ABAP) was measured in blood from six patients. There was no change when red cells alone were studied, but when the patients' plasma was added to red cell suspensions (producing 10% plasma and 10% red cell suspensions), mean H50 increased from 291 to 308 min (P=0.049). Despite there being no overall increase in plasma antioxidant activity, the lipid soluble component of blood antioxidant activity appears to be increased by propofol.

Summary

Background and objective: Awareness with postoperative recall of intraoperative events is a rare but serious complication of general anaesthesia. This survey investigated the attitude of anaesthetists in the UK to awareness and depth of anaesthesia monitoring. Methods: Questionnaires were sent to 4927 consultant anaesthetists in 285 hospitals in the UK in September 2004. The responses were recorded in an electronic database, summarized and compared with the results of studies performed in Australia and the USA. Results: The response rate was 44%. When judged against published awareness rates, anaesthetists underestimated the incidence of awareness in their own practice (median 1: 5000). One-third of respondents have dealt with patients who have experienced intraoperative recall. The majority of anaesthetists perceived awareness as a minor problem on an 11-point scale (modal score 2, median score 3, IQR 2–5). Eighty-six percent of anaesthetists considered clinical signs unreliable but 91% felt that measurement of end-tidal anaesthetic agent concentration reduces the likelihood of awareness. The majority of anaesthetists would use a monitor at least some of the time if one was available to them. Overall, the attitudes of anaesthetists in the UK, USA and Australia are remarkably similar. Conclusions: Anaesthetists tend not to view awareness as a serious problem. Although most accept that clinical signs are unreliable indicators of awareness, few believe that monitors of anaesthetic depth should be used for routine cases.

Background and objective The incidence and clinical impact of perioperative myocardial infarction during coronary artery bypass graft surgery vary greatly depending upon the diagnostic criteria applied. Fatal perioperative myocardial infarction has a less arguable diagnosis and clinical impact. The aim of this paper is to find out the risk factors for fatal myocardial infarction after coronary surgery.

Methods Data from 1561 consecutive patients, who underwent coronary revascularization during a 10-month period, have been retrospectively analysed. After an univariate analysis for pre- and intraoperative risk factors, a multivariate model (logistic regression analysis) was settled.

Results Preoperative use of subcutaneous/intravenous heparin, a heparin sensitivity index <1.3 and need for a thromboendarterectomy of the left anterior descending coronary artery are independent risk factors for fatal myocardial infarction. The relative risk for fatal myocardial infarction was about 2 in the case of preoperative heparin use or heparin sensitivity index <1.3 and 5.5 in the case of thromboendarterectomy of the left anterior descending coronary artery.

Conclusions In patients undergoing coronary artery bypass surgery, preoperative anticoagulation management with heparin may represent a risk factor for fatal myocardial infarction. Patterns of heparin resistance, whether or not due to heparin pretreatment, seem to be closely related to fatal myocardial infarction.

Summary

Background and objective: The haemodynamic effects of acute pulmonary hypertension can be largely attributed to ventricular interdependence during diastole. However, there is evidence that the two ventricles also interact during systole. The aim of the present study was to examine the effects of acute pulmonary hypertension on both components of left ventricular systole, i.e. contraction and relaxation, using load-independent indices. Methods: Ten pigs were instrumented with biventricular conductance catheters, a pulmonary artery flow probe and a high-fidelity pulmonary pressure catheter. Haemodynamic measurements were performed in baseline conditions and during stable pulmonary vasoconstriction induced by the thromboxane analogue U46619. Contractility was quantified using the end-systolic pressure–volume and preload recruitable stroke work relationships. The τ-end-systolic pressure relationship was used to assess load-dependency of relaxation. Results: Acute pulmonary hypertension caused a decrease in the slope of the left ventricular preload recruitable stroke work relationship (from 6.64 ± 1.7 to 5.19 ± 1.9, mean ± SD; P < 0.05), a rightward shift of the end-systolic pressure–volume relationship (P < 0.05), and an increase in the slope of the τ-end-systolic pressure relationship (from −0.15 ± 0.5 to 0.35 ± 0.17; P < 0.05). The diastolic chamber stiffness constant of both ventricles increased during pulmonary hypertension (P < 0.05). Conclusions: In the present model, acute pulmonary hypertension impairs left ventricular contractile function and relaxing properties. The present study provides additional evidence that, besides the well-known diastolic ventricular cross talk, systolic ventricular interaction may play a significant role in the haemodynamic consequences of acute pulmonary hypertension.

Summary

Background and objectives: The aim of this prospective, randomized, double-blind study was to determine the effects of adding two different target-controlled concentrations of remifentanil (1 and 3 ng mL−1) on the desflurane requirement for blunting sympathetic responses after surgical incision (minimum anaesthetic concentration (MACBAR)). Methods: 67 patients, aged 20–50 yr, ASA I, undergoing general anaesthesia for elective abdominal surgery were enrolled and randomly allocated to receive no remifentanil infusion (n = 21) or a target-controlled effect-site concentration of 1 ng mL−1 (n = 24) or 3 ng mL−1 remifentanil (n = 22). All patients were anaesthetized with propofol, cisatracurium and desflurane with a mixture of 60% nitrous oxide in oxygen. Sympathetic responses to surgical incision were determined after a 20-min period of stable end-tidal desflurane and target-controlled remifentanil concentrations. Predetermined end-tidal desflurane concentrations and the MACBAR for each group were determined using an up-and-down sequential-allocation technique. Results: The MACBAR of desflurane was higher in the group receiving no remifentanil (6.25% [95% confidence interval: 5.9–6.5%]) as compared with patients of the groups receiving 1 ng mL−1 (2.7% [2.6–2.8%]; P < 0.001) and 3 ng mL−1 remifentanil (2% [1.9–2.2%]; P < 0.01). When considering a MAC value in this age population and the contribution of 60% nitrous oxide (0.55 MAC), the combined MACBAR values, expressed as multiples of the MAC, were 1.9, 0.8 and 0.6 MAC, in the three groups, respectively. Conclusion: A target-controlled concentration of 1 ng mL−1 remifentanil results in a 57% decrease in the MACBAR of desflurane combined with 60% nitrous oxide. Increasing the target concentration of remifentanil to 3 ng mL−1 produces a further 26% decrease in the MACBAR values of desflurane.

Summary

Background and objectives: Supplemental oxygen is commonly given via nasal cannulae in spontaneously breathing patients. Our modified nasal cannula with a clamp between the nasal prongs can provide O2 via one nostril and CO2 can be sampled through the other one. We have studied whether this cannula can provide oxygenation similar to a standard cannula without affecting end-tidal CO2 monitoring. Methods: Eighty-six patients were studied during spinal anaesthesia and sedation. In 15 patients, arterial blood was sampled while O2 was delivered at flow rates of 0, 2 and 4L min−1, with or without clamping between the prongs of our modified nasal cannula. In the remaining 71 patients, arterial O2 was measured while using our modified nasal cannula with the clamp applied. End-tidal CO2 was recorded on a capnograph and the correlation between end-tidal and arterial values with our modified nasal cannula was investigated. Results: No end-tidal CO2 waveforms were found with oxygen flow greater than 2L min−1 without clamping between the prongs. With clamping there was a significant correlation (r = 0.83) between arterial and end-tidal CO2. A Bland–Altman analysis revealed a bias of 0.49 kPa with precision of ±0.76 kPa. Arterial oxygenation was not affected by our modified nasal prongs with clamp as compared to the standard cannula. Conclusion: Our modified nasal cannula can provide continuous monitoring of end-tidal CO2 without affecting oxygen delivery in sedated, spontaneously breathing patients.

Summary

Background and objectives: To evaluate the effectiveness of acupressure in preventing nausea and vomiting in patients undergoing gynaecological operations and receiving a patient-controlled analgesia device. Methods: Patients aged between 40 and 65 yr were included. Exclusion criteria were obesity, diabetes mellitus, and history of motion sickness, postoperative nausea and vomiting, or smoking. Patients were randomized into one of two groups, acupressure and control. In the acupressure group, acupressure bands were placed on both wrists with the plastic bead positioned at the P6 point. In controls, beads were placed at a non-acupoint site. All patients received a standard general anaesthetic. Postoperatively, patients were connected to a patient-controlled analgesia device with morphine (loading dose 5 mg, background infusion 1 mg h−1, bolus dose 1 mg and lock-out time 10 min). Pain and sedation scores, respiratory rate, heart rate, arterial pressure and oxygen saturation were recorded for 24 h. Metoclopramide 10 mg was administered intravenously as a rescue antiemetic. Results: Fifty patients received acupressure and 50 were controls. In the acupressure group, 33% of patients had nausea compared with 63% controls. The cumulative incidence of vomiting at 24 h was 25% with acupressure and 61% in controls. The incidence of nausea, vomiting and antiemetic use was significantly lower with acupressure. Conclusions: Acupressure at the P6 meridian point is an effective alternative for the prevention of nausea and vomiting in patients receiving patient-controlled analgesia with morphine after gynaecological surgery.

Summary

Background and objective: We evaluated the effect of duration of mechanical ventilation with different tidal volumes (VT) on ventilator-induced lung injury in healthy rats. Methods: Anaesthetized rats were ventilated with VT between 9 and 45 mL kg−1 for 1 or 7 h with a positive end-expiratory pressure of 2.5 cmH2O. Results: After 1 h, rats ventilated even with the highest applied VT (36 and 45 mL kg−1, resulting in average peak airway pressures of 30 ± 3 and 37 ± 4 cmH2O), had no detectable alterations in dynamic or static lung mechanics, gas exchange or pulmonary permeability, but a moderate degree of lung inflammation (neutrophil accumulation in broncho-alveolar lavage) observed in all groups. In contrast, after 3 h of ventilation, rats ventilated with the highest VT (36 and 45 mL kg−1) died from progressive circulatory failure and high-permeability pulmonary oedema, manifested by hypoxaemia, an increased alveolar–arterial protein concentration ratio and a reduced static lung compliance (mortality rate at 7 h, 62.5% and 100%). Animals with lower VT all survived and presented no changes in the measured variables. Conclusion: These results in normal rats demonstrate the preponderant effect of the duration (>3 h) of ‘aggressive’ ventilation and the cut-off value of the level of VT applied (>27 mL kg−1).

Summary

Background and objective: The optimal depth of insertion of left-sided double-lumen endobronchial tubes is strongly correlated with body height in average-sized adults. However, this relationship has not been studied in below average-sized adult patients. We investigated whether or not there is a clinically useful relationship in below average-sized adult patients. Methods: One hundred and ninety six consecutive adult patients undergoing thoracic surgery under one-lung anaesthesia (body height ≤ 155 cm) were included in this study. Left-sided double-lumen tubes were inserted under the guidance of a fibre-optic bronchoscope. Optimal depth was defined as the proximal surface of the bronchial cuff positioned just below the carina. Results: There was a statistically significant positive correlation between body height and the optimal depth of insertion (r = 0.61, P < 0.0001); however, the correlation coefficient was low. The actual optimal depth of insertion of one patient was even 4.5 cm shorter than that obtained from the equation. Conclusion: Although there was a statistically significant correlation between body height and the optimal depth of insertion of left sided double lumen tubes in adult patients of short stature (≤ 155 cm), clinical application of the equation is not warranted and these tubes should be inserted under direct vision with a fibre-optic bronchoscope.