Non-directed bronchial lavage is a safe method for sampling the respiratory tract in critically ill patient.

Ventilated patients are at risk of acquiring ventilator-associated pneumonia. Various techniques are available for diagnosing ventilator-associated pneumonia including bronchoalveolar lavage, protected specimen brush and non-directed bronchoalveolar lavage. There is a paucity of evidence regarding the safety profile of these techniques, particularly non-directed bronchoalveolar lavage. This service evaluation aimed to establish whether non-directed bronchoalveolar lavage is a safe procedure. A prospective service evaluation of non-directed bronchoalveolar lavage on our adult intensive care unit was undertaken by a senior physiotherapist trained into carrying out the procedure, measuring pre- and post-procedure vital signs including heart rate (HR), tidal volume (VT), systolic blood pressure (SBP) and pulse oximetry (SpO2). Eighty-five episodes in 41 patients were included in the evaluation. There was a statistically significant difference between pre- and immediately post-procedure recordings for all vital signs measure. HR (min-1), means (SD) 87.1 (16.4), 91.5 (16.5), 87.5 (15.9), 87.7 (15.7) respectively pre, immediately, 5 min after and 30 min after procedure (P < 0.01). SBP mmHg, means (SD) 133.9 (26.1), 142.1 (25.6), 136.9 (25.3), 134.8 (23.4) pre, immediately, 5 min and 30 min after procedure (P < 0.01). VT mL, median (range) 0.523 (0.118-1.180), 0.512 (0.131-1.05), 0.519 (0.104-0.95), 0.534 (0.110-1.080) each pre, immediately, 5 min and 30 min post procedure (P < 0.05). SpO2 %, median (range) 98 (89-100), 100 (96-100), 98 (92-100), 97 (90-100) again each pre-, immediately post, 5 and 30 min post-procedure time-points (P < 0.0001). The statistically significant difference was not detected between pre-, 5 or 30 min post-procedure time-points. None of the changes observed were clinically significant and no untoward events happened to any of the subjects included. Non-directed bronchoalveolar lavage is a safe and inexpensive procedure that can be carried out easily in an intensive care setting by a trained physiotherapist, avoiding the need for invasive bronchoscopy.

Assessment of scoring systems to describe the position of tracheostomy tubes within the airway - the lunar study.

BACKGROUND: Malposition of tracheostomy tubes is difficult to detect at the bedside and may contribute to eventual device misplacement. Endoscopic examination can be undertaken via tracheoscopic (T-view) or trans-laryngeal (L-view) approach, offering more precise detail regarding positioning within the airway. The aims of this study were to evaluate inter-rater agreement between bespoke T and L view scoring systems and subsequently whether T-views could predict L-views. METHODS: Adult intensive care unit patients with percutaneous or surgical tracheostomies were included and paired T and L-views of their tracheostomy tube within the airway were taken on up to four occasions. Images were later scored by five independent raters using bespoke scoring systems. The primary outcome was to determine the T and L view scoring system with the best inter-rater agreement, defined by weighted kappa and intra-class correlation coefficients. The secondary outcome was to assess agreement between T and L-view scoring systems. RESULTS: Seventy-one T-views and 43 L-views were obtained from a total of 20 patients. Images were scored by five raters, resulting in 355 T-view scores, 215 L-view scores and 215 paired T and L-view scores for comparison. There was good inter-rater agreement (highest T-view k = 0.84, L-view k = 0.72). There was poor agreement between T and L-view scores for each of the paired images (highest k = 0.25) although extreme-to-extreme misclassification rates remained acceptable. CONCLUSIONS: Whilst our data demonstrated good inter-rater agreement between scoring systems, it is not possible to reliably predict the T-view orientation and position of a tracheostomy tube within the airway from the paired L-view. CLINICAL TRIAL REGISTRATION: NCT01356719.

Fetal effects of combined spinal-epidural vs epidural labour analgesia: a prospective, randomised double-blind study.

We have compared fetal heart rate patterns, Apgar scores and umbilical cord gas values following initiation of labour analgesia using either combined spinal-epidural or epidural. One hundred and fifteen healthy women requesting neuraxial analgesia in the first stage of labour were randomly assigned to receive either combined spinal-epidural (n = 62) or epidural analgesia (n = 53). Fetal heart rate traces, recorded for 30 min before and 60 min after neuraxial block, were categorised as normal, suspicious or pathological according to national guidelines. Sixty-one fetal heart rate tracings were analysed in the combined spinal-epidural group and 52 in the epidural group. No significant differences were found in fetal heart rate patterns, Apgar scores or umbilical artery and vein acid-base status between groups. However, in both combined spinal-epidural and epidural groups, there was a significant increase in the incidence of abnormal fetal heart rate patterns following neuraxial analgesia (p < 0.0001); two before compared with eight after analgesia in the combined spinal-epidural group and zero before compared with 11 after in the epidural group. These changes comprised increased decelerations (p = 0.0045) (combined spinal-epidural group nine before and 14 after analgesia, epidural group four before and 16 after), increased late decelerations (p < 0.0001) (combined spinal-epidural group zero before and seven after analgesia, epidural group zero before and eight after), and a reduction in acceleration rate (p = 0.034) (combined spinal-epidural group mean (SD) 12.2 (6.7) h(-1) before and 9.9 (6.1) h(-1) after analgesia, epidural group 11.0 (7.3) h(-1) before and 8.4 (5.9) h(-1) after). These fetal heart rate changes did not affect neonatal outcome in this healthy population.

Combined spinal epidural vs epidural labour analgesia: does initial intrathecal analgesia reduce the subsequent minimum local analgesic concentration of epidural bupivacaine?

Labour analgesia initiated using a combined spinal-epidural (CSE) technique may reduce subsequent epidural bupivacaine requirements compared with an epidural-only technique. We compared the minimum local analgesic concentrations (MLAC) of epidural bupivacaine following initial intrathecal or epidural injection. In a prospective, double-blind study, 115 women requesting epidural analgesia were randomly assigned to receive either an epidural with bupivacaine 20 mg and fentanyl 40 µg or a CSE with intrathecal bupivacaine 2.5 mg and fentanyl 5 µg. Analgesia was assessed using a visual analogue pain score. When further analgesia was requested, bupivacaine 20 ml was given, and the concentration was determined using the technique of up-down sequential allocation. The MLAC of bupivacaine in the epidural group was 0.032% wt/vol (95% CI 0.020-0.044) compared with 0.047% wt/vol (95% CI 0.042-0.052) in the CSE group. Bupivacaine requirements for the second injection were increased following intrathecal analgesia by a factor of 1.45 (p = 0.026) compared with epidural analgesia.

Use of thromboelastography to guide thromboprophylaxis after caesarean section.

BACKGROUND: Thromboprophylaxis is commonly required following caesarean section. However the effect of thromboprophylactic dosages of subcutaneous heparin on coagulation is unknown because conventional laboratory tests are largely unaffected. The aim of this study was to determine if thromboelastography could detect and quantify the effect of unfractionated heparin on coagulation profile when given at the time of surgery. METHODS: Nineteen women undergoing elective caesarean section were recruited. Blood samples collected before and after administration of subcutaneous unfractionated heparin 7500 IU underwent thromboelastography using both plain and heparinase cuvettes. Anti-factor Xa levels were also measured. RESULTS: There was a significant difference in R times between plain and heparinase samples (-10.6%, P=0.0072) indicating that thromboelastography could detect an effect of unfractionated heparin. Compared to baseline there were significant decreases of R times in plain (-20.4%, P=0.033) and heparinase (-28.8%, P=0.0001) samples despite the administration of unfractionated heparin. Anti-factor Xa levels were virtually undetectable (mean 0.01 U/mL). CONCLUSION: Thromboelastography was able to detect and quantify the effect of unfractionated heparin on blood coagulability, an effect not detected by conventional laboratory tests. Thromboelastography demonstrated a pro-coagulant effect of surgery that was only partially mitigated by the use of unfractionated heparin. In this study, at a dose of 7500 IU subcutaneous unfractionated heparin appears to have little anticoagulant effect.

Epidural volume extension in combined spinal epidural anaesthesia for elective caesarean section: a randomised controlled trial.

We investigated the effect of epidural volume extension on spinal blockade in pregnant women undergoing elective caesarean section with a combined spinal-epidural technique. We randomly allocated 90 healthy subjects to three groups to receive spinal hyperbaric bupivacaine 7.5 mg (group B7.5), spinal hyperbaric bupivacaine 7.5 mg immediately followed by epidural volume extension with saline 5 ml (group B7.5-EVE) or spinal hyperbaric bupivacaine 10 mg without epidural volume extension (group B10). We evaluated the height of the block every 5 min for 15 min following the spinal injection. The overall sensory block level increased with time (p < 0.001), regardless of the group studied, and there were significantly fewer failures of block in the group B10 compared with both B7.5 and B7.5-EVE groups (p = 0.001). In conclusion, we could not demonstrate a benefit in using epidural volume extension with 5 ml saline as part of a combined spinal epidural technique in term parturients undergoing elective caesarean section.

Minimum effective dose of spinal ropivacaine with and without fentanyl for postpartum tubal ligation.

BACKGROUND: Ropivacaine may be the ideal spinal anesthetic for postpartum tubal ligation due to its medium duration of action, low incidence of side effects and possibly reduced post-anesthetic care unit (PACU) stay. METHODS: Two prospective up-down sequential allocation studies were performed using hyperbaric spinal ropivacaine via a combined spinal-epidural anesthetic technique for patients undergoing postpartum tubal ligation. The first study was performed using an initial dose of 12.5 mg hyperbaric ropivacaine, which was adjusted in testing intervals of 0.5 mg. The second study used an initial dose of 16 mg hyperbaric ropivacaine, a testing interval of 1.0mg, and a fixed dose of fentanyl 10 µg. The need to supplement the block with intravenous or epidural agents was defined as a failure. Failures were treated with epidural lidocaine. RESULTS: The first and second studies recruited 24 and 17 patients, respectively. The median effective dose (ED50) for hyperbaric spinal ropivacaine was 16.4 mg (95% CI 13.7-19) with an ED95 estimate of 21.9 mg. The median effective dose of spinal ropivacaine with fentanyl 10 µg was 17.0 mg (95% CI 15.4-18.7) with an ED95 estimate of 21.3 mg. When data were combined, the overall ED50 for ropivacaine was 16.7 mg (95% CI 15.1-18.4) with an ED95 estimate of 22.5 mg (95% CI 16.3-28.8). A T8 block was not achieved in 4 patients receiving spinal ropivacaine alone, and 1 patient receiving spinal ropivacaine with fentanyl. The majority (82%) of patients who did not receive epidural local anesthetic supplementation had recovery of motor block within 60 min following PACU admission. CONCLUSION: Spinal hyperbaric ropivacaine 22 mg with or without fentanyl 10 µg could be used for postpartum tubal ligation surgery.

Effect of i.v. phenylephrine or ephedrine on the ED50 of intrathecal bupivacaine with fentanyl for caesarean section.

BACKGROUND: Prophylactic infusion of phenylephrine to prevent hypotension at Caesarean section has been shown to decrease the rostral spread of intrathecal plain levobupivacaine and intrathecal hyperbaric bupivacaine by a median of two dermatomes compared with ephedrine. The aim of this study was to determine the median effective dose (ED50) of intrathecal bupivacaine required to achieve a block to touch at the xiphisternum in patients undergoing Caesarean section when phenylephrine or ephedrine are used to prevent hypotension. METHODS: Seventy women were randomized in two groups to receive either phenylephrine at a rate of 16.6 microg min(-1) (concentration 1microg ml(-1)) or ephedrine at a rate of 1.5 mg min(-1) (concentration 90 microg ml(-1)). Patients received varying doses of hyperbaric bupivacaine with fentanyl 25 microg using a double-blinded, up-down sequential allocation design. Effective doses were defined as anaesthesia to touch with ethyl chloride spray to the xiphisternum within 20 min. RESULTS: The ED50 estimates of bupivacaine were similar in the two groups: 7.8 mg [95% confidence interval (CI) 6.7-8.9] with phenylephrine and 7.6 mg (95% CI 6.8-8.4) with ephedrine. Systolic blood pressure control was similar (P=0.18) with vasopressors but heart rate was higher with ephedrine (P=0.0014). CONCLUSIONS: Under the conditions of this study, we have shown that when phenylephrine or ephedrine were used to prevent post-spinal hypotension, the dosing requirement of hyperbaric bupivacaine was similar for intrathecal anaesthesia.

Determination of the EC50 of levobupivacaine for femoral and sciatic perineural infusion after total knee arthroplasty.

BACKGROUND: Infusion of local anaesthetic through femoral and sciatic catheters is an accepted method of providing pain relief after knee arthroplasty. However, the minimum effective concentration of perineural local anaesthetics is not known. METHODS: Twenty-four patients received femoral and sciatic perineural infusions of levobupivacaine in order to prevent pain relief after total knee arthroplasty. The primary endpoint of the study was patient request for analgesic rescue for anterior or posterior knee pain within the first 36 h of perineural infusion. Treatment was determined by the method of sequential allocation, with a dosing interval of 0.002% w/v. RESULTS: Thirteen patients did not require rescue analgesia for anterior knee pain and 16 patients did not require rescue analgesia for posterior knee pain. Median duration of failed blocks until rescue analgesia was 25 h (24-27 h) for the femoral block and 27 h (24-29 h) for the sciatic block. The minimum concentration at which patients did not require rescue analgesia was 0.024% for the femoral nerve and 0.014% for the sciatic nerve. Comparison of EC(50) showed that local anaesthetic requirements were significantly (P=0.03) higher by a factor of 1.25 (95% CI 1.03-1.55) for the femoral compared with the sciatic nerve. CONCLUSIONS: The EC(50) for femoral perineural infusion is greater than the EC(50) for sciatic perineural infusion.

Validation and application of a high-fidelity, computational model of acute respiratory distress syndrome to the examination of the indices of oxygenation at constant lung-state.

BACKGROUND: Calculated venous admixture (Qs/Qt) is considered the best index of oxygenation; surrogates have been developed (Pa(O(2))/Fi(O(2)), respiratory index, and arterioalveolar PO(2) difference), but these vary with Fi(O(2)), falsely indicating a change in lung-state. Using a novel model, we aimed to quantify the behaviour of the indices of oxygenation listed above during physiological and treatment factor variation. The study is the first step in developing an accurate and non-invasive tool to quantify oxygenation defects. METHODS: We present the static and dynamic validation of a novel computational model of gas exchange in acute respiratory distress syndrome (ARDS) based upon the Nottingham Physiology Simulator. Arterial gas tension predictions were compared with data derived from ARDS patients. The subsequent study examined the indices' susceptibility to variation induced by independent changes in Fi(O(2)) (0.3-1.0), haemoglobin concentration (Hb: 6-14 g dl(-1)), oxygen consumption (VO(2): 250-350 ml min(-1)), and Pa(CO(2)) (4-8 kPa). RESULTS: Static validation produced a mean error of -0.3%, a 10-fold improvement over previous models. Dynamic validation produced a mean prediction error of -0.05 kPa for Pa(O(2)) and 0.09 kPa for Pa(CO(2)). Every parameter, especially Fi(O(2)), induced variation in all indices. The least Fi(O(2))-dependent index was Qs/Qt (variation: 5.1%). In contrast, Pa(O(2))/Fi(O(2)) varied by 77% through the range of Fi(O(2)). CONCLUSIONS: We have improved simulation of gas exchange in ARDS by using a sophisticated respiratory model. Using the validated model, we have demonstrated that the current indices of oxygenation vary with alteration in Hb, Pa(CO(2)), and VO(2) in addition to their previously well-documented dependence on Fi(O(2)).

Estimation of the minimum motor blocking potency ratio for intrathecal bupivacaine and lidocaine.

BACKGROUND: The up-down sequential allocation model has been adapted to investigate a variety of clinical and pharmacological issues in neuraxial anaesthesia including the estimation of relative potency ratios for analgesia and motor block of the most commonly used epidural and intrathecal local anaesthetics. The aim of this study was to establish the median effective doses (ED50) for motor block with intrathecal lidocaine and bupivacaine and to define the relative motor blocking potency ratio. METHODS: In this prospective, randomised, double blind, parallel group, up-down sequential allocation study, we enrolled 71 parturients undergoing elective caesarean section under combined spinal-epidural anaesthesia. The women received either intrathecal lidocaine 2% w/v or bupivacaine 0.5% w/v. The initial dose was 4 mg for bupivacaine and 12 mg for lidocaine. Subsequent doses were determined by the outcome in the previous parturient, according to the up-down sequential allocation technique. The end point was the occurrence of any motor block in either lower limb within 5 min. RESULTS: The intrathecal ED50 for motor block was 13.7 mg for lidocaine (95% CI, 13.1 to 14.4) and 3.4 mg for bupivacaine (95% CI, 2.6 to 4.1) (P<0.0001) and the relative motor blocking potency ratio was 4.1 (95% CI 3.3 to 5.2). CONCLUSIONS: Intrathecal bupivacaine was 4.1 times more potent than lidocaine for motor block.

Hyaluronidase reduces local anaesthetic volumes for sub-Tenon's anaesthesia.

BACKGROUND: Volumes of local anaesthetics for sub-Tenon's anaesthesia vary. Lower volumes produce less akinesia, whereas higher volumes increase chemosis and intra-ocular pressures. Hyaluronidase is often added to local anaesthetics to improve akinesia without increasing the volume of the injection, but this is controversial. This randomized, sequential allocation study examines the addition of hyaluronidase on the minimum local anaesthetic volume (MLAV) required for a sub-Tenon's block. METHODS: Sixty-two patients having sub-Tenon's blocks for cataract surgery were randomized into two groups. The control group (n=31) received 2% w/v lidocaine and the study group (n=31) received 2% w/v lidocaine with hyaluronidase 15 IU ml(-1). Using parallel up-down sequential allocation from a 4 ml starting volume, the volumes in both groups were changed using a testing interval of 1 ml according to the quality of globe akinesia. The median effective local anaesthetic volume (MLAV) was calculated for both groups using probit regression. RESULTS: The groups were similar for age, sex, and ocular axial length. The MLAV in the hyaluronidase group was 2.6 ml [95% confidence interval (CI), 2.1-3.l] and 6.4 ml (95% CI, 5.1-8.1) in the control group (P<0.002). CONCLUSIONS: Hyaluronidase permits a significant 2.4-fold (95% CI, 1.8-3.4) reduction in MLAV for sub-Tenon's anaesthesia.

An isobolographic analysis of diamorphine and levobupivacaine for epidural analgesia in early labour.

BACKGROUND: Few data describe the pharmacological interactions between local anaesthetics and opioids. The aim of this study was to measure the median effective concentration (MEC) of diamorphine and levobupivacaine when given separately and as mixtures for epidural analgesia, and determine whether the combination is additive or synergistic. METHODS: One hundred and twenty patients were enrolled in this prospective randomized, two-phase, double-blind study. In the first phase, 60 women were randomized to receive a fixed 20 ml volume of either levobupivacaine or diamorphine epidurally . Dosing was determined using up-down sequential allocation with testing intervals, respectively, of 0.01%w/v and 12.5 microg ml(-1). After estimations of the MEC of levobupivacaine and diamorphine, a further 60 patients were randomized in the second phase to one of the three mixtures: (a) diamorphine 70 microg ml(-1) (fixed) and levobupivacaine (testing interval 0.004%w/v, starting at 0.044%w/v); (b) levobupivacaine 0.044%w/v (fixed) and diamorphine (testing interval 7 microg ml(-1), starting at 70 microg ml(-1)); and (c) bivariate diamorphine and levobupivacaine (testing intervals of 7 microg ml(-1) and 0.004%w/v starting at 70 microg ml(-1) and 0.044% w/v respectively). RESULTS: The MEC estimates from the first phase were 143.8 microg ml(-1) (95% CI 122.2-165.3) for diamorphine and 0.083%w/v (95% CI 0.071-0.095) for levobupivacaine. In the second phase, the MEC and interaction index (gamma) of the three combinations were: diamorphine 65.5 microg ml(-1) (56.8-74.2), gamma = 0.99; levobupivacaine 0.041%w/v (0.037-0.049), gamma = 0.98; and for the fixed combination diamorphine 69.5 microg ml(-1) (60.5-78.5) and levobupivacaine 0.044%w/v (0.039-0.049), gamma = 1.02. CONCLUSION: The combination of diamorphine and levobupivacaine is additive and not synergistic when used for epidural analgesia in the first stage of labour.