The effect of high-flow nasal oxygen flow rate on gas exchange in apnoeic patients: a randomised controlled trial.

High-flow nasal oxygen can be administered at induction of anaesthesia for the purposes of pre-oxygenation and apnoeic oxygenation. This intervention is claimed to enhance carbon dioxide elimination during apnoea, but the extent to which this occurs remains poorly quantified. The optimal nasal oxygen flow rate for gas exchange is also unknown. In this study, 114 patients received pre-oxygenation with high-flow nasal oxygen at 50 l.min-1. At the onset of apnoea, patients were allocated randomly to receive one of three nasal oxygen flow rates: 0 l.min-1; 70 l.min-1; or 120 l.min-1. After 4 minutes of apnoea, all oxygen delivery was ceased, tracheal intubation was performed, and oxygen delivery was recommenced when SpO2 was 92%. Mean (SD) PaCO2 rise during the first minute of apnoea was 1.39 (0.39) kPa, 1.41 (0.29) kPa, and 1.26 (0.38) kPa in the 0 l.min-1, 70 l.min-1 and 120 l.min-1 groups, respectively; p = 0.16. During the second, third and fourth minutes of apnoea, mean (SD) rates of rise in PaCO2 were 0.34 (0.08) kPa.min-1, 0.36 (0.06) kPa.min-1 and 0.37 (0.07) kPa.min-1 in the 0 l.min-1, 70 l.min-1 and 120 l.min-1 groups, respectively; p = 0.17. After 4 minutes of apnoea, median (IQR [range]) arterial oxygen partial pressures in the 0 l.min-1, 70 l.min-1 and 120 l.min-1 groups were 24.5 (18.6-31.4 [12.3-48.3]) kPa; 36.6 (28.1-43.8 [9.8-56.9]) kPa; and 37.6 (26.5-45.4 [11.0-56.6]) kPa, respectively; p < 0.001. Median (IQR [range]) times to desaturate to 92% after the onset of apnoea in the 0 l.min-1, 70 l.min-1 and 120 l.min-1 groups, were 412 (347-509 [190-796]) s; 533 (467-641 [192-958]) s; and 531 (462-681 [326-1007]) s, respectively; p < 0.001. In conclusion, the rate of carbon dioxide accumulation in arterial blood did not differ significantly between apnoeic patients who received high-flow nasal oxygen and those who did not.

Pre-oxygenation with facemask oxygen vs high-flow nasal oxygen vs high-flow nasal oxygen plus mouthpiece: a randomised controlled trial.

High-flow nasal oxygen used before and during apnoea prolongs time to desaturation at induction of anaesthesia. It is unclear how much oxygenation before apnoea prolongs this time. We randomly allocated 84 participants to 3 minutes of pre-oxygenation by one of three methods: 15 l.min-1 by facemask; 50 l.min-1 by high-flow nasal cannulae only; or 50 l.min-1 by high-flow nasal cannulae plus 15 l.min-1 by mouthpiece. We then anaesthetised and intubated the trachea of 79 participants and waited for oxygen saturation to fall to 92%. Median (IQR [range]) times to desaturate to 92% after pre-oxygenation with facemask oxygen, high-flow nasal oxygen only and high-flow nasal oxygen with mouthpiece, were: 309 (208-417 [107-544]) s; 344 (250-393 [194-585]) s; and 386 (328-498 [182-852]) s, respectively, p = 0.014. Time to desaturation after facemask pre-oxygenation was shorter than after combined nasal and mouthpiece pre-oxygenation, p = 0.006. We could not statistically distinguish high-flow nasal oxygen without mouthpiece from the other two groups for this outcome. Median (IQR [range]) arterial oxygen partial pressure after 3 minutes of pre-oxygenation by facemask, nasal cannulae and nasal cannulae plus mouthpiece, was: 49 (36-61 [24-66]) kPa; 57 (48-62 [30-69]) kPa; and 61 (55-64 [36-72]) kPa, respectively, p = 0.003. Oxygen partial pressure after 3 minutes of pre-oxygenation with nasal and mouthpiece combination was greater than after facemask pre-oxygenation, p = 0.002, and after high-flow nasal oxygen alone, p = 0.016. We did not reject the null hypothesis for the pairwise comparison of facemask pre-oxygenation and high-flow nasal pre-oxygenation, p = 0.14.

Survey of Smartphone Use among Anaesthetists In Saolta University Health Care Group Midlands Setting.

BACKGROUND: The use of smartphones in health care settings has become widespread. Although there are several benefits of smartphone usage for anaesthetists, there is a potential for negative effects on their performance and hence on patients' care. OBJECTIVES: To investigate the ownership and patterns of anaesthetists' usage of smartphones and to identify the concerns and opinions about the potentially harmful effects of their use. METHODS: We emailed an online survey to all anaesthetists working in the Saolta university healthcare group. RESULTS: A high proportion of anaesthetists owned 1-5 medical-related applications (61.1%). Drug and medical references was the most commonly used category of applications. DISCUSSION: There is an increasing number of useful medical-related apps with a potential for improving performance and new developments. The low level of awareness to smartphone use policies indicates the need for increasing awareness and developing guidelines that encourage the safe use of smartphones.

Induced mild hypothermia reduces mortality during acute inflammation in rats.

BACKGROUND: Hypothermia has been proposed as a therapeutic possibility in brain trauma, cardiac arrest and hemorrhagic shock. Experimental studies have shown that hypothermia may act by modulating the inflammatory response during endotoxemia. This study was carried out to test whether hypothermia could protect rats from endotoxemic insult. METHODS: After general anesthesia and oro-tracheal intubation, Sprague-Dawley rats were randomly assigned to either a hypothermic group or normothermic group. In each group, rats received intraperitoneal lipopolysaccharide (LPS) (10 or 20 mg/kg). Blood samples were taken prior to and 2 h after LPS injection to measure blood gases, liver enzymes, muscular enzymes, tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) plasma levels. After 2 h of hypothermia, the rats were extubated and brought back to their cages. The mortality rate was observed for 7 days following endotoxemia. In a second set of experiments, hypothermia was induced 1 h after endotoxemia (10 mg/kg of intraperitoneal LPS) and the mortality rate was observed for the following 7 days. RESULTS: The survival rate was significantly increased in the hypothermic group relative to the normothermic group, regardless of LPS dose. This increased survival rate was also observed when hypothermia was induced 1 h after endotoxemia. In the hypothermic group, IL-10 and the DeltaIL-10/DeltaTNF-alpha ratio were significantly increased relative to those in the normothermic group. CONCLUSION: Induced mild hypothermia reduces mortality during endotoxemia in rats. The modulation of the inflammatory response, with an increase in anti-inflammatory cytokines, may be involved in this protective effect.

Long-term evaluation of motor function following intraneural injection of ropivacaine using walking track analysis in rats.

BACKGROUND: There is a paucity of data regarding neurologic function following nerve injury. Our objective was the long-term evaluation of motor function following intraneural injection of ropivacaine in rats using the sciatic function index (SFI), derived from walking track analysis. METHODS: Rats were randomly assigned to one of four groups of 13 animals each. A needle was inserted under magnification into the left sciatic nerve and 0.2 ml of normal saline, formalin 15%, ropivacaine 0.2 or 0.75% were injected intraneurally. The right side was sham operated. Walking track analysis was performed the day before and on days 1, 4, 7, 11, 15, 18, 21, and 67 following intraneural injection. At the end of the experiment (day 67) a semi-quantitative evaluation of neuropathologic changes was performed by three independent observers. RESULTS: Animals treated with saline and ropivacaine (0.2 and 0.75%) had no detectable impairment of motor function at any time point. In contrast, rats treated with formalin had a complete loss of motor function immediately after the intraneural injection, which persisted until day 21 and returned to normal by day 67. Important histopathologic changes (score=2) with excellent inter-observer agreement were seen only in the group treated with formalin. This applied to both axonal degeneration and Schwann cell density evaluations. CONCLUSIONS: These findings suggest that intraneural injections of ropivacaine at concentrations routinely used in clinical practice appear to have no deleterious effect on sciatic nerve motor function in this experimental rat model.

Optimizing the dose of intrathecal morphine in older patients undergoing hip arthroplasty.

UNLABELLED: Intrathecal (IT) morphine provides excellent postoperative analgesia but may result in many side effects, including postoperative nausea and vomiting, pruritus, and respiratory depression, particularly at larger doses. Older patients may be at particular risk. The optimal dose of spinal morphine in older patients undergoing hip arthroplasty is not known. We designed this prospective, randomized, controlled, double-blinded study to evaluate the analgesic efficacy and side effect profile of 50-200 microg of IT morphine in older patients undergoing elective hip arthroplasty. Sixty patients older than 65 years undergoing elective hip arthroplasty were enrolled. Patients were randomized to receive spinal anesthesia with 15 mg of bupivacaine and IT morphine in four groups: 1). 0 microg, 2). 50 microg, 3). 100 microg, and 4). 200 microg. IT morphine 100 and 200 microg produced effective pain relief and decreased the postoperative requirement for morphine compared with control. IT morphine 50 microg did not provide effective pain relief. Both 100 and 200 microg of IT morphine provided comparable levels of postoperative analgesia. There were no between-group differences in postoperative nausea and vomiting, sedation, respiratory depression, or urinary retention. Pruritus was significantly more frequent with 200 microg of IT morphine. In conclusion, 100 microg of IT morphine provided the best balance between analgesic efficacy and side effect profile in older patients undergoing hip arthroplasty. IMPLICATIONS: The dosage of intrathecal morphine that provides the best balance between analgesic efficacy and side effect profile in the older patient undergoing hip arthroplasty is not known. This prospective, randomized, controlled, double-blinded clinical trial demonstrates that a dose of 100 microg of intrathecal morphine provides the best balance between efficacy and side effects, compared with doses of 0, 50, and 200 microg of morphine, in this patient population.

Clinical perception of phantom limb sensation in patients with brachial plexus block.

BACKGROUND AND OBJECTIVE: Patients' perception of limb position during regional anaesthesia is frequently incorrect. The incidence and nature of this phenomenon has not yet been completely described. The aim of this prospective study was to assess phantom sensation in patients undergoing a brachial plexus block. METHODS: Axillary block was performed in 81 patients with the aid of a peripheral nerve stimulator. Immediately after the block, patients were allocated randomly to two groups (Group 1, n = 40; Group 2, n = 41) to have the blocked limb placed either on their thorax or in abduction. Fifteen minutes later, when the block was complete, the position of the limb was changed, without the knowledge of the patient, to a new position of abduction and flexion of the forearm. Patients were questioned about the new limb position. Fifteen minutes later, the limb was then transiently shown to the patient and further placed 'blindly' to another position. Patients were once more questioned about this new position. RESULTS: Correct perception was more frequently observed in both groups following the first interview. Thirty-two and 34 patients gave at least one erroneous response about their limb position when it was initially placed on the thorax or in abduction respectively. Transient visualization of the limb position did not improve the rate of correct response. CONCLUSIONS: Patients' perception of the position of the limb after axillary block in the majority of instances was probably due to persisting sensory inputs from the shoulder joint, which is not involved in this block. This is in contrast to supraclavicular or interscalene blocks. A significant number of patients experienced phantom limb sensation. They reported an arm position in fact related to the position of their arm before the axillary block.

Improvement of information gained from the pre-anaesthetic visit through a quality-assurance programme.

BACKGROUND: Pre-anaesthetic evaluation is a fundamental component of anaesthetic practice. The aims of the present study were to assess the quality of the preoperative anaesthetic information gathered and to observe the quality profile after the introduction of a standardized form. This occurred through a four-step quality assurance programme over a 4-yr period. METHODS: The proportion of cases in which a complete recording of data was collected at the preoperative assessment was evaluated by searching in each patient's medical record for what was considered to be the minimum information required to provide satisfactory perioperative care. Fifteen criteria were selected. The recovery profile for each indicator and a global quality index (GQI expressed in %) for each patient's record were collected. In phase 1, the existing situation was assessed. Next, a standardized pre-anaesthetic form (PAF 1) was designed and its implementation evaluated (Phase 2). Phase 3 was performed 16 months after implementation of PAF 1 to assess the long-term value. The form was revised (PAF 2) and its use evaluated again 6 months later (Phase 4). For each evaluation, the records of a 1-month period were examined. Overall 1129 medical records were audited. RESULTS: The GQI increased significantly from 62 to 88% with similar changes for both elective and emergency cases. The recovery profile was improved for most indicators. CONCLUSIONS: We conclude that the quality of information recorded from the pre-anaesthetic visit is improved by using a standardized form. This will hopefully help to improve patient outcome and facilitate computerization of the anaesthetic record.

Chlorhexidine versus povidone iodine in preventing colonization of continuous epidural catheters in children: a randomized, controlled trial.

BACKGROUND: Chlorhexidine is better than povidone iodine for skin preparation before intravascular device insertion or blood culture collection, but it is not known whether chlorhexidine is superior in reducing colonization of continuous epidural catheters. METHODS: Children requiring an epidural catheter for postoperative analgesia longer than 24 h were randomly assigned to receive skin preparation with an alcoholic solution of 0.5% chlorhexidine or an aqueous solution of 10% povidone iodine before catheter insertion. Using surgical aseptic techniques, catheters were inserted into either the lumbar or the thoracic epidural space based on the preferences of the anesthesia team, on clinical indication, or both. Immediately before epidural catheter removal, their insertion site and hub were qualitatively cultures. After their removal, the catheter tips were quantitatively cultured. Catheters were classified as colonized when their tips yielded 1,000 or more colony-forming units/ml in cultures. RESULTS: Of 100 randomly assigned patients, 96 were evaluable. The clinical characteristics of the patients and the risk factors for infection were similar in the two groups. Catheters were kept in place for a median (range) duration of 50 (range, 21-100) h. Catheters inserted after skin preparation with chlorhexidine were one sixth as likely and less quickly to be colonized as catheters inserted after skin preparation with povidone iodine (1 of 52 catheters [0.9 per 100 catheter days] vs. 5 of 44 catheters [5.6 per 100 catheter days]; relative risk, 0.2 [95% confidence interval, 0.1-1.0]; P = 0.02). Coagulase-negative staphylococci were the only colonizing microorganisms recovered, and the skin surrounding the catheter insertion site was the origin of all the colonizing microorganisms. CONCLUSIONS: Compared with aqueous povidone iodine, the use of alcoholic chlorhexidine for cutaneous antisepsis before epidural catheter insertion reduces the risk of catheter colonization in children.

Sedation with sufentanil and midazolam decreases pain in patients undergoing upper limb surgery under multiple nerve block.

Multiple nerve blocks may be painful and a source of discomfort. We assessed the efficacy of sufentanil 5 microg combined with midazolam 1 mg in decreasing pain in outpatients after a midhumeral multiple nerve stimulation technique. Visual analog scores for pain were significantly lower in those patients who received sedation before the block, both at the time of block performance (14 +/- 1 vs 27 +/- 2 mm, P < 0.0001) and at discharge (11 +/- 1 vs 24 +/- 2 mm, P < 0. 0001). We conclude that the association of sufentanil and midazolam produced minimal sedation while significantly reducing pain experienced by patients undergoing multiple nerve stimulation.

Airway complications in infants: comparison of laryngeal mask airway and the facemask-oral airway.

PURPOSE: To compare the incidence of airway complications in children less than one year of age whose airways were maintained during anesthesia with either a laryngeal mask airway (LMA) or a facemask and oral airway (FM-OA). METHODS: We randomized 49 - ASA class 1&2 - infants to an LMA or FM-OA group. All infants were undergoing minor general, urological or orthopedic procedures. Anesthesia was induced and maintained with halothane in nitrous oxide 50% and oxygen. The airway was removed in both groups when the infant was awake. The occurrence of airway complications (breath-holding, coughing, laryngospasm, secretions, obstruction and oxygen saturation < 95%) at induction of anesthesia, intraoperatively and during emergence from anesthesia was recorded. RESULTS: Airway complications occurred perioperaively in 15 of 27 infants in the LMA group and in 5 of 22 infants in the FM-OA group (P: 0.02). CONCLUSION: In infants, the use of the LMA is associated with an increased incidence of airway complications compared with the use of the FM-OA.

Sufentanil does not prolong the duration of analgesia in a mepivacaine brachial plexus block: a dose response study.

UNLABELLED: To date, results of studies evaluating the efficacy of opioids and local anesthetic combinations in the brachial plexus are inconclusive. We examined whether increasing sufentanil in doses of 5, 10, and 20 microg decreased onset time or increased duration of an axillary brachial plexus block. Ninety-two patients scheduled for carpal tunnel release under axillary brachial plexus block were enrolled in the study. Patients were randomized to receive axillary plexus block with 40 mL 1.5% mepivacaine and saline (Group 1), sufentanil 5 microg (Group 2), 10 microg (Group 3), or 20 microg (Group 4). Onset and duration of sensory and motor block were measured. Opioid-related side effects were recorded. The addition of sufentanil did not improve speed of onset or increase the duration of sensory or motor block. Paradoxically, duration of sensory and motor block was longest in the control group: sensory, 241 min (188-284) and motor, 234 min (128-305), and decreased with increasing doses of sufentanil in Group 4: sensory, 216 min (115-315) and motor, 172 min (115-260) (P < 0.05). Side effects occurred in 55% of patients belonging to Groups 2 and 4, and in 60% of the patients in Group 3. In contrast, only 10% of the patients reported side effects in the control group. We conclude that sufentanil added to mepivacaine does not increase the onset or prolong the duration of an axillary plexus block. Furthermore, the addition of sufentanil was associated with a frequent incidence of side effects. IMPLICATIONS: This study demonstrates that the addition of sufentanil in a dose-dependent manner to 1.5% mepivacaine in the axillary plexus does not improve onset or duration of blockade, and that this admixture is associated with an increased incidence of side effects.

Management of peri-operative pulmonary hypertension in a patient presenting for a portosystemic shunt.

We report the successful management of intra-operative pulmonary hypertension in a patient with mitral valve insufficiency and portal hypertension. A 48-year-old male with portal hypertension presented for a portosystemic shunt. Previously undiagnosed mitral valve insufficiency and pulmonary hypertension complicated his anaesthetic management. His intra-operative course was marked by systolic hypotension, pulmonary hypertension and a reduction in cardiac output. The use of nitric oxide in this patient reduced right ventricular afterload, increased cardiac output, without exacerbating pre-existing systolic hypotension.

Recurarization in the recovery room.

A case of recurarization in the recovery room is reported. Accumulation of atracurium in the intravenous line led to recurarization after flushing the line in the recovery room. A respiratory arrest with severe desaturation and bradycardia occurred. Circumstances leading to this event and the mechanisms enabling a neuromuscular blockade to occur, following the administration of a small dose of relaxant, are discussed.