G. McLeod

Postoperative pain relief using thoracic epidural analgesia : outstanding success and disappointing failures

Six hundred and forty patients received epidural analgesia for postoperative pain relief following major surgery in the 6‐year period 1993–1998. Although satisfactory pain relief was achieved in over two‐thirds of patients for a median duration of 44 h after surgery, one‐fifth of patients (133 individuals) still experienced poor pain relief. Almost one out of three patients (194 individuals) had a problem with their epidural. Eighty‐three patients (13%) suffered a technical failure and 84 (13%) patients had their epidurals removed at night time when pain‐free because of pressure on beds. Seven patients had their epidural replaced and subsequently experienced excellent pain relief for a median of 77 h. Lack of resources prevented a further 480 patients from receiving the potential benefits of epidural analgesia. These results would suggest that the practical problems of delivering an epidural service far outweigh any differences in drug regimens or modes of delivery of epidural solutions.

Propofol 2% in critically ill patients: Effect on lipids

OBJECTIVE To investigate the concentrations of triglyceride, cholesterol, and high-density lipoprotein during a 50-hr infusion of 2% propofol, starting within 24 hrs of admission to the intensive care unit (ICU). DESIGN Prospective, clinical study. SETTING ICU, university hospital. PATIENTS Thirty adult patients, who were ventilated and expected to be sedated for >2 days, were studied for 50 hrs, beginning at 1800 hrs on the first day of ICU admission. MEASUREMENTS AND MAIN RESULTS Triglyceride, cholesterol, and high-density lipoprotein were measured at 2000, 0400, and 0800 hrs. Tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and C-reactive protein were measured at 2000 hrs. Median cholesterol and high-density lipoprotein concentrations were at the low end of the normal range. In seven patients, peak triglyceride concentrations were >3 mmol/L up to a maximum of 4.83 mmol/L. Although there was no statistical difference in lipid concentrations between days 1 and 2, there was an apparent pattern of increasing triglyceride concentrations. There was a correlation between peak triglyceride concentration and total propofol consumption, but there was no correlation between lipids and age, gender, or Acute Physiology and Chronic Health Evaluation II scores. There was a direct correlation between triglyceride and C-reactive protein concentrations, and an inverse correlation between cholesterol and C-reactive protein. Twenty-two patients had evidence of TNF and 11 patients had an IL-6 of >1000 pg/mL, but there was no relationship between concentrations of cytokines and triglycerides in plasma. CONCLUSIONS Infusion of 2% propofol to critically ill patients over a 50-hr period does not result in a significant increase in triglyceride concentrations. Mean cholesterol and high-density lipoprotein concentrations were low throughout the study period. There was a significant direct correlation between triglyceride and C-reactive protein and an inverse correlation between cholesterol and C-reactive protein, suggesting that the changes in lipids in critically ill patients may be partly attributable to the acute-phase response.

Skin blood flow changes in response to intradermal injection of bupivacaine and levobupivacaine, assessed by laser Doppler imaging.

Background and Objectives The vascular effects of local anesthetics are important determinants of their therapeutic activity. Drugs that vasoconstrict have the potential clinical advantages of limited systemic uptake and prolonged duration of effect. The aim of this study was to assess quantitatively the cutaneous vasoactivity of racemic bupivacaine and one of its enantiomers, levobupivacaine. Methods Four concentrations of each drug (0.1 mL each of 0.125%, 0.25%, 0.5%, and 0.75%), as well as normal saline, were injected intradermally into randomly assigned sites on the forearms of 10 volunteers. We measured skin blood perfusion using laser Doppler imaging before injection and at 2.5, 10, 20, 40, 60, and 90 minutes thereafter. Results Both drugs produced a rapid, dose-dependent increase in skin perfusion (P < .001). Saline also caused an increase in perfusion, although less sustained. By 40 minutes, most responses had returned to baseline levels. However, after this time, perfusion continued to decrease, below baseline, for both bupivacaine and levobupivacaine. The exception to this was 0.75% bupivacaine, the response to which was significantly higher than the same concentration of levobupivacaine over this later period (P < .05). Conclusions Bupivacaine and levobupivacaine both have a biphasic effect on skin microvessels. The vasoconstriction observed after 40 minutes may occur when the quantity of drug remaining at the administration site has decreased to a lower level. The continued vasodilatation caused by bupivacaine is more difficult to interpret. The results suggest that these local anesthetics cause vasodilatation at high doses and vasoconstriction at lower, subclinical doses. This hypothesis and the clinical relevance of these effects warrant further investigation.

Local infiltration analgesia for total knee arthroplasty

for investigating the performance of standard operating procedures in anaesthesia. Br J Anaesth 2007; 99: 673–8 17 Bruppacher H, Alam S, LeBlanc V, et al. Simulation-based training improves physicians’ performance in patient care in high-stakes clinical setting of cardiac surgery. Anesthesiology 2010; 112: 985–92 18 Murray D, Boulet J, Avidan M, et al. Performance of residents and anesthesiologists in a simulation-based skill assessment. Anesthesiology 2007; 107: 705–13 19 Yee B, Naik V, Joo H, et al. Non-technical skills in anesthesia crisis management with repeated exposure to simulation-based education. Anesthesiology 2005; 103: 241–8 20 Toth J, Hunt R. Not one versus many, but zero versus any: structure and function in the context of the multiple memory-systems debate. In: Foster J, Jelicic M, eds. Memory: System, Process, or Function? Oxford: Oxford University Press, 1999: 232–72 21 Schacter D, Addis D, Buckner R. Episodic simulation of future events: concepts, data, and applications. Ann N Y Acad Sci 2008; 1124: 39–60 22 Maguire E, Frith C. Aging affects the engagement of the hippocampus during autobiographical memory retrieval. Brain 2003; 126: 1511–23 23 Aly M, Moscovitch M. The effects of sleep on episodic memory in older and younger adults. Memory 2010; 18: 327–34 24 Johnson M, Hashtroudi S, Lindsay D. Source monitoring. Psychol Bull 1993; 114: 3–28 25 Murdock B. The serial position effect of free recall. J Exp Psychol 1962; 64: 482–8

Mechanisms influencing the vasoactive effects of lidocaine in human skin

The vasodilator properties of lidocaine are believed to be due mainly to the inhibition of action potentials via sodium channel blocking in vasoconstrictor sympathetic nerves. However, mechanisms involving the vascular endothelium may also play a role, and in this study we investigated the potential influences of nitric oxide release, the cyclo‐oxygenase pathway and the β‐adrenoceptors of vascular smooth muscle. Laser Doppler imaging was used to measure microvascular blood flow responses to intradermal injection of lidocaine 2%, with or without the addition of preservatives, in eight healthy, male volunteers. Co‐injection of the nitric‐oxide–synthase inhibitor Nω‐nitro‐l‐arginine methyl ester caused a 60% reduction in the response after about 20 min, and this reduction was enhanced with the lidocaine solution containing the preservatives methylhydroxybenzoate and propylhydroxybenzoate. No reduction in response was seen after blocking the cyclo‐oxygenase or β‐adrenoceptor pathways. Nitric oxide release contributes to the vasoactivity of lidocaine in human skin.

A randomised controlled trial of oxytocin 5IU and placebo infusion versus oxytocin 5IU and 30IU infusion for the control of blood loss at elective caesarean section—Pilot study. ISRCTN 40302163

OBJECTIVE To compare the blood loss at elective lower segment caesarean section with administration of oxytocin 5IU bolus versus oxytocin 5IU bolus and oxytocin 30IU infusion and to establish whether a large multi-centre trial is feasible. STUDY DESIGN Women booked for an elective caesarean section were recruited to a pilot randomised controlled trial and randomised to either oxytocin 5IU bolus and placebo infusion or oxytocin 5IU bolus and oxytocin 30IU infusion. We wished to establish whether the study design was feasible and acceptable and to establish sample size estimates for a definitive multi-centre trial. The outcome measures were total estimated blood loss at caesarean section and in the immediate postpartum period and the need for an additional uterotonic agent. RESULTS A total of 115 women were randomised and 110 were suitable for analysis (5 protocol violations). Despite strict exclusion criteria 84% of the target population were considered eligible for study participation and of those approached only 15% declined to participate and 11% delivered prior to the planned date. The total mean estimated blood loss was lower in the oxytocin infusion arm compared to placebo (567 ml versus 624 ml) and fewer women had a major haemorrhage (>1000 ml, 14% versus 17%) or required an additional uterotonic agent (5% versus 11%). A sample size of 1500 in each arm would be required to demonstrate a 3% absolute reduction in major haemorrhage (from baseline 10%) with >80% power. CONCLUSION An additional oxytocin infusion at elective caesarean section may reduce blood loss and warrants evaluation in a large multi-centre trial.

Echogenic regional anaesthesia needles: a comparison study in Thiel cadavers.

Ultrasound guidance is now the standard procedure for regional nerve block in anesthesiology. However, ultrasonic visualisation of needle manipulation and guidance within tissues remains a problem. Two new echogenic needles (Pajunk and Braun) have been introduced to anesthesiology clinical practice but evaluation has been restricted to preserved animal tissue. In this study, the visibility of both echogenic needles was compared with a standard nonechogenic needle in a Thiel cadaver model. A total of 144 intramuscular injections were made in the upper arm in-plane and out-of-plane to the ultrasound beam at four angles (30°, 45°, 60° and 75°). The visibility of the needle was assessed by two independent, blinded observers using a 5-point Likert ordinal scale. Weighted κ for interobserver agreement was 0.77 (95% confidence interval [CI]: 0.68-0.86). The Pajunk echogenic needle was more visible than the Braun standard needle in-plane (p = 0.04), and the Braun standard and Braun echogenic needles out-of-plane (p = 0.02). Independent predictors of visibility using logistic regression were needle (p < 0.001) and plane of insertion (p = 0.08), receiver operator characteristic (ROC) area under the curve 0.90. In conclusion, the Pajunk echogenic needle offers the best visibility for ultrasound-guided regional anesthesia.

An evaluation of Thiel-embalmed cadavers for ultrasound-based regional anaesthesia training and research:

Working hours of UK trainee doctors have recently been reduced to 48 hours per week, reducing exposure to clinical cases. As such, there is widespread acceptance that trainees need to train in environments other than the ward or operating theatre in order to gain practical skills. Formalin-fixed cadavers demonstrate gross muscle and nerve anatomy but needle insertion under ultrasound guidance is poor. In contrast, a new development in medical simulation is the use of Thiel-embalmed cadavers, developed by Professor Thiel of the University of Graz, Austria, using a novel preservation technique that retains full flexibility of the limbs. Thiel cadavers have been used to successfully simulate laparoscopic surgery, neurosurgery and oral surgery. This paper investigates, for the first time, the application of ultrasound-based regional anaesthesia to the Thiel cadaver by tracing the course of peripheral nerves, injecting local anaesthetic around nerves, and reproducing inadvertent intraneural injection by injecting preservative directly into the nerve. The Thiel cadaver provides good conditions for anaesthetists to simulate regional anaesthetic block techniques using ultrasound.

A cadaver study comparing spread of dye and nerve involvement after three different quadratus lumborum blocks

BACKGROUND Posterior variants of abdominal wall block include the quadratus lumborum type I, quadratus lumborum type II and quadratus lumborum transmuscular blocks. Our objectives were to compare the spread of injectate and nerve involvement, after conducting blocks using ultrasound guidance in soft embalmed cadavers. METHODS After randomization, an experienced anaesthetist conducted three quadratus lumborum 1, three quadratus lumborum 2 and four transmuscular blocks on the left or right sides of five cadavers. All cadavers were placed in the lateral position and the quadratus lumborum muscle seen using a 3-9 MHz ultrasound probe placed in the flank. For each block, a 20 ml mixture of 17.75 ml water, 2 mls latex and 0.25 ml India ink was injected. The lumbar region and abdominal flank were dissected 72 h later. RESULTS We conducted 10 blocks. Two quadratus lumborum 1 and two quadratus lumborum 2 blocks were associated with spread of dye within the TAP plane. One quadratus lumborum 1 block spread to the deep muscles of the back and one quadratus lumborum 2 block dispersed within the subcutaneous tissue surrounding the abdominal flank. All transmuscular quadratus lumborum blocks spread consistently to L1 and L3 nerve roots and within psoas major and quadratus lumborum muscles. CONCLUSIONS Consistent spread to lumbar nerve roots was achieved using the transmuscular approach through the quadratus lumborum.

A comparison of the ease of tracheal intubation using a McGrath MAC(®) laryngoscope and a standard Macintosh laryngoscope.

We compared the McGrath MAC® videolaryngoscope when used as both a direct and an indirect laryngoscope with a standard Macintosh laryngoscope in patients without predictors of a difficult tracheal intubation. We found higher median Intubation Difficulty Scores with the McGrath MAC as a direct laryngoscope, 1 (0–3 [0–5]) than when using it as an indirect videolaryngoscope, 0 (0–1 [0–5]) or when using the Macintosh laryngoscope, 0 (0–1 [0–5]), p = 0.04. This was mirrored in the subjective user reporting, scored out of 10, of difficulty for each method 3.0 (2.0–3.4 [0.5–80]); 2.0 (1.0–3.9 [0–70]) and 2.0 (1.0–3.3 [0–70]), respectively (p = 0.01). This difficulty is in part explained by the poorer laryngeal views recorded using the Cormack and Lehane classification system (p < 0.001) and reflected in the higher than normal operator force required (25%, 4%, 8% for each method, respectively, p < 0.001) and the increased use of rigid intubation aids (21%, 6%, 2%, respectively, p < 0.001). There was no difference between the groups in time taken to intubate or incidence of complications. There was no statistical difference in the performances as measured between the McGrath MAC used as an indirect videolaryngoscope and the Macintosh laryngoscope. We cannot recommend that the McGrath videolaryngoscope be used as a direct laryngscopic device in place of the Macintosh.