1 Statins for all: the new premed? Brookes et al. Br J Anaesth. 2009 Jul;103(1):99-107
This review article details the emerging potential benefits of statins during the perioperative period. Potential positive effects of statins extend beyond lipid lowering to include anti-inflammatory actions particularly in relation to the incidence of sepsis and cardiovascular complications, both coronary and cerebrovascular. With long-term administration, evidence suggests better outcomes in heart failure, Alzheimer’s disease, autoimmune disease and renal disease. The author emphasizes the modulation of role of nitric oxide (NO) that occurs with statins and the impact this has on the endothelium. Statins are believed to have differential effects on the subtypes of nitric oxide synthetase (NOS) to alter the balance and increase the favourable eNOS and inhibit the potentially harmful iNOS isoform that is associated with increased production of reactive oxygen species that contribute to endothelial dysfunction. Reduction in endothelial dysfunction and inflammation is thought to improve outcomes in major sepsis as well as reduce the incidence of atherosclerosis. Although benefits have been reported in the perioperative period, much of the data of relevance is retrospective and performed in small samples limiting the conclusions that can be drawn. There is a need for well-designed randomized clinical trials to examine the role of perioperative statins in cardioprotection and sepsis which will hopefully enable targeting of therapy for specific patient groups as well as define details such as dose and duration of statin administration necessary to obtain benefits.
Take home message: Patients already on statins should be continued on them in the perioperative period. Statins maybe of benefit for a larger subset of patients ‘at risk’ or coronary or cerebrovascular events in the perioperative period but the current evidence base is suggestive rather than conclusive.
For related reading this month: - Marcucci C et al. Perioperative statin therapy may be implicated in a wide array of drug-drug interactions. Anesthesiology. 2009 Jul;111(1):205; author reply 205-6.
2 Should we really be more 'balanced' in our fluid prescribing? Editorial: Morris C et al. Anaesthesia. 2009 Jul;64(7):703-5.
This excellent editorial calls attention to the fickle and unscientific approach to fluid prescribing in anaesthesia and intensive care. The author emphasizes that many widely held practices and opinions regarding fluids are not evidence based including the perceived superiority of ‘balanced’ solutions and ‘harm’ associated with normal saline induced hyperchloraemia. Available ‘balanced’ solutions invariably contain inorganic anions (lactate, acetate, maleate, gluconate) that need to be metabolized and may have vasodilatory or other consequences. The potential benefits of bicarbonate containing fluids such as renal replacement solutions need further study. Despite the massive expense associated with critical care fluid use, unfortunately the products are not required to satisfy the equivalent rigorous safety and efficacy standards that new drugs must satisfy prior to clinical use.
Take home message: There is little concrete evidence on which to base fluid prescribing so the threat of inadvertently causing harm to our patients with commercially available fluids is a real possibility.
See also: March Journal Watch (9); May Journal Watch (1)
For related reading this month: - Schramko AA et al. Role of fibrinogen-, factor VIII- and XIII-mediated clot propagation in gelatin haemodilution. Acta Anaesthesiol Scand. 2009 Jul;53(6):731-5. - Westphal M et al. Hydroxyethyl starches: different products--different effects. Anesthesiology. 2009 Jul;111(1):187-202.
3 A retrospective analysis of deep neck infections at Royal Perth Hospital. Matzelle S et al. Anaesth Intensive Care. 2009 July;37(4):604-607.
This retrospective paper details the outcomes of 129 patients with deep neck infections (DNIs) managed at Royal Perth Hospital and highlights a patient group where the potential for significant morbidity and mortality may be underestimated. Unlike many of our high-risk patient groups, complications can occur in a relatively young age group of otherwise healthy patients. Twenty patients (15.5%) of the sample had a complicated course with 7 patients requiring awake tracheostomies. In 8 patients failure of the primary airway plan occurred, 4 patients required postoperative re-intubation and there was 1 postoperative death associated with post-operative airway obstruction. Approximately 50% of the patients were admitted to ICU for postoperative ventilation. It is interesting to note that awake intubations were attempted in 6/8 of the cases where the primary airway plan failed. The major predictor for airway complications identified was lack of a consultant anaesthetist. The author recommends further prospective study in this area which may shed light on the association between complications and presenting symptoms as well as patient factors (ie. BMI, OSA), and possibly further delineate the approaches to the airway that are likely to be successful.
Take home message: Patients with deep neck infection are at significant risk of perioperative airway obstruction and should be managed by those with an appropriate level of experience, often in a HDU/ICU environment.
4 Liability related to peripheral venous and arterial catheterization: a closed claims analysis. Bhananker SM et al. Anesth Analg. 2009 Jul;109(1):124-9.
This article outlines the details from the American ASA closed claims database relating to peripheral venous and arterial catheterization over a 25- year period from 1975-2000. Approximately half of peripheral IV complications were related to the extravasation of drugs or fluids and consequences of such including fasciotomy scars. Peripheral catheter malpractice claims were the most common in cardiac surgery possibly because of ‘arm tucking’. The most commonly reported drugs causing skin slough were thiopentone, calcium chloride and inotropes. Claims due to air embolism were mostly associated with air in blood bags from cell savers and had the highest median compensation. There were multiple events of severe permanent brain was associated with air embolism in paediatrics. Notably there were no claims for complications of IV catheters in patients who had previously had an axillary node dissection. A death and a permanent brain injury resulted from iliac artery injury and retroperitoneal haemorrhage associated with femoral artery cannulation. Several amputations were required for digital or limb ischaemia resulted from arterial cannulation however, claims related to radial artery catheterization were uncommon. The author recommends meticulous attention to potential extravasation when the location of the catheter is in doubt, especially in cardiac surgery as well as always puncturing the femoral artery below the inguinal ligament. This is a retrospective analysis and the closed claims database is an incomplete and imperfect dataset, but outcomes are likely to be representative of clinical practice.
Take home message: Evidence from closed claims databases suggest claims relating to peripheral venous and arterial catheterization are relatively uncommon but occasionally associated with death or significant disability and are often highly preventable with adequate attention to detail.
5 Pharmacokinetic models for propofol--defining and illuminating the devil in the detail. Absalom AR et al. Br J Anaesth. 2009 Jul;103(1):26-37.
This article attempts to unravel some of the complicated intricacies behind the pre-programmed TCI Marsh and Schnider pharmacokinetic models for propofol. These models are based on a three-compartment PK model and use various estimated rate constants to predict time course of redistribution and metabolism in order to estimate plasma/effect site concentration. The basic difference is that the original Marsh model has fixed rate constants whereas compartment volumes and clearances are ONLY weight proportional. The Schnider model is more complex and it has fixed values for compartment volumes V1 & V3 and rate constants k13 and k31 adjusts V2, k12 and k21 for age and adjusts k10 according to total weight, lean body mass and height. The concept of effect site concentration was developed when it became apparent that there was hysteresis in the relationship between plasma concentration and clinical effect. The time course of plasma effect-site equilibration can be mathematically described by a first-order rate constant typically referred to as keo. Clinical studies have used the time to peak effect (TTPE) to estimate keo. The choice of keo will influence the degree of plasma concentration over-and undershoot when the target concentration is changed. The Marsh model uses a slower (smaller) keo compared with the Schnider model. It is interesting to note that the Marsh model was developed based on trial of only 18 patients and the Schnider model was developed based on a trial of only 24 patients. Importantly, the models make assumptions and estimates of the values of compartment volumes and rate constants so there are multiple potential sources of inaccuracy with both models. The combined effect of differing values means that the degree of overshoot of estimated plasma concentration is much greater with the weight based Marsh model. Conversely, a possible advantage of the Schnider model is that it adjusts doses and infusion rates according to patient age, which is potentially of significance in elderly and unwell patients because of PK and PD changes occurring with advanced age. Practically, this means the highest total dose will be given by the Marsh model in effect-site targeting mode followed by the Marsh model in plasma targeting mode, then the Schnider model in effect-site targeting mode, and finally the lowest dose will be administered by the Schnider model in plasma targeting mode. The major differences will be seen in the first 10 minutes of infusion except in the special circumstance of obese patients. In the obese, induction requirement are more closely related to lean body mass but maintenance requirements do increase significantly with severe obesity and are more closely related to total body mass. This has lead to some practioners to calculate a weight for obese patients (different to actual body weight) to input into the TCI pump based on various formulas using ideal body weight as a reference. TCI should be used with caution in severely obese patients, regardless of which model or effect-site implementation is used. In conclusion, there is little definitive evidence to demonstrate the superiority of any particular model or method of effect-site targeting implementation.
Take home message: Most experts would agree that when using TCI propofol if the Schnider model (available on newer Alaris Asena pumps or Base Primea) is chosen it should be used in effect-site targeting mode, whereas if the Marsh model is chosen it should be used plasma targeting mode.
6 Perioperative management of children with obstructive sleep apnea. Schwengel DA et al. Anesth Analg. 2009 Jul;109(1):60-75.
This comprehensive review discusses the significant implications of the presence of OSA in paediatric patients. OSA presents differently compared to the adult population and definitive diagnosis is challenging because of the requirement for polysomnography. The peak incidence is 2-6 years of age and it is more common in children with developmental abnormalities. Adenotonsillectomy is the treatment of choice for most children with OSA. Numerous authors have demonstrated that paediatric patients with OSA are at increased risk for postoperative respiratory complications ranging from increased work of breathing to post-operative death. Opioid sparing postoperative analgesia is preferred and there are evidence of improved outcomes with tramadol, non-apririn NSAIDs and intra-operative steroids. Children < 3years of age have twice the risk of complications compared with children 3-6 years of age therefore duration of hospital admission needs to be considered carefully in the younger age-group.
Take home message: Anaesthetists should routinely screen paediatric patients for snoring and apnoeas because perioperative complications are increased in OSA patients after all types of surgery, especially adenotonsillectomy.
7 Spread of injectate after ultrasound-guided subcostal transversus abdominis plane block: a cadaveric study. Barrington MJ et al. Anaesthesia. 2009 Jul;64(7):745-50.
This study provides a detailed description of the subcostal TAP block and used 7 cadavers to assess the spread of dye injected using a US guided subcostal TAP approach. In 7 hemi-abdomens, a single injection of 20 mls was placed immediately lateral to the linea semilunaris in the TAP. In the other 7 hemi-abdomens, a multi-injection technique was used comparing 4 injections of 5 ml. The first 5 ml injection occurred between rectus abdominis and transversus (posterior rectus sheath) and the subsequent 3 injections occurred in the TAP lateral to the linea semilunaris at progressively more lateral positions in the TAP. After dissection, the nerves most commonly involved in dye were T10 and T11 in the single injection sides and T9, T10 and T11 in the multiple-injection sides. In contrast, the standard posterior TAP approach where the probe is placed on the anterolateral abdominal wall between the iliac crest and the costal margin usually targets T11, T12 and L1. The authors recommend that the subcostal TAP injection should be performed laterally as close as possible to the costal margin to ensure that the thoracolumbar nerves are targeted proximal to their entry into the rectus sheath. There are obviously limitations to using cadavers to assess spread of dye however the findings of this study are consistent with preliminary findings in clinical studies.
Take home message: This study indicates that ultrasound-guided subcostal TAP block will most likely involve nerve roots, T9, T10 and T11 (periumbilical) and that a multiple-injection technique may increase spread of injectate compared with a single-injection technique.
8 Anaesthesiological considerations on tocolytic and uterotonic therapy in obstetrics. Vercauteren M et al. Acta Anaesthesiol Scand. 2009 Jul;53(6):701-9.
This article details the efficacy and adverse effects associated with the use of tocolytic and uterotonic therapies. Calcium channel blockers such as nifedipine are also relatively well tolerated although mild vasodilatation and hypotension may occur. In contrast, beta-adrenergic agonists are being abandoned due to adverse haemodynamic consequences including tachycardia, arrhythmias, pulmonary oedema, hyperglycaemia and rebound hyperkalaemia. Nitroglycerin is predominantly useful as a single dose (100 mcg) acute tocolytic. NSAIDs, including COX-2 inhibitors are still under investigation but their tocolytic benefit is questionable mainly due to potential foetal side effects. With respect to oxytocic drugs, oxytocin during labour can be associated with adverse fetal effects especially if hyperstimulation occurs and maternal water intoxication is also a risk. Post-delivery, oxytocin is has proven efficacy but a rapid bolus can be associated with hypotension and tachycardia. There is currently no evidence to support giving a bolus of more than 5 IU. Carbetocin is a new synthetic oxytocin analogue with comparable efficacy to oxytocin but lower rate of side effects and longer half-life. . Another new intravenous oxytocin antagonist called atosiban is likely to become first line tocolytic therapy because it is effective and devoid significant side effects. Prostaglandin E2 given intravenously may cause severe hypotension while PGF2-alpha can cause pulmonary hypertension and bronchospasm. Ergot alkaloids are associated with hypertension (pulmonary and systemic), coronary artery spasm, bronchospasm, nausea & vomiting and rarely myocardial infarction.
Take home message: It is important to consider the potential for adverse effects associated with the use of tocolytic and uterotonic therapies.
For related reading this month: - Bergum D, Lonnée H, Hakli TF. Oxytocin infusion: acute hyponatraemia, seizures and coma. Acta Anaesthesiol Scand. 2009 Jul;53(6):826-7.
9 Venous air embolism during total laparoscopic hysterectomy: comparison to total abdominal hysterectomy. Kim CS et al. Anesthesiology. 2009 Jul;111(1):50-4.
This study used TOE to compare the incidence and grade of venous air embolism in total laparoscopic hysterectomy (TLH; n=40) and total abdominal hysterectomy (n=40). All patients undergoing TLH showed some degree of VAE and 37.5 % of these patients showed bubbles filling more than half of the right heart. Haemodynamic variables remained stable and there were no neurological abnormalities detected despite an incidence of PFO(patent foramen ovale) of approximately 25%. Only 15% of patients undergoing conventional TAH showed evidence of VAE.
Take home message: Although VAE during TLH is common and rarely clinically significant, this study highlights the fact that the anaesthetist must be vigilant in diagnosis and management of embolic complications should they occur.
For related reading this month: -Schäfer ST et al. Cardiac air transit following venous air embolism and right ventricular air aspiration. Anaesthesia. 2009 Jul;64(7):754-61. -Schäfer ST et al. Venous air embolism induces both platelet dysfunction and thrombocytopenia. Acta Anaesthesiol Scand. 2009 Jul;53(6):736-41.
10 Optimal remifentanil dosage for providing excellent intubating conditions when co-administered with a single standard dose of propofol. Bouvet L et al. Anaesthesia. 2009 Jul;64(7):719-26.
This RCT (n=90) compared five remifentanil dose groups (1, 2, 3, 4, 5 mcg/kg) combined with 2.5 mg/kg of propofol in ASA 1 and 2 patients. The primary endpoint was optimal intubating scores. The study found that 4 mcg/kg was associated with best intubating conditions in 95% of patients however the only statistically significant difference between groups was vocal cord position. A remifentanil dose of 1.8 mcg/kg was associated with acceptable intubating conditions in 50% of patients. Maximum decrease in HR and BP was <30% of baseline however it is likely haemodynamic consequences of relatively high dose propofol and remifentanil would have much more significant consequences in older patients with end-organ disease. The small sample size limits external validity.
Take home message: This study shows muscle-relaxant free excellent intubating conditions can be achieved safely in healthy patients with propofol 2.5 mg and a remifentanil bolus of 4 mcg/kg over 1 minute, if intubation is attempted 150 seconds post induction.
For related reading this month: - Editorial: Kopman AF. How low can you go? Lowest effective dose of neuromuscular blocking agent for tracheal intubation. Can J Anaesth. 2009 Jul;56(7):473-477. - Siddik-Sayyid SM et al. Excellent intubating conditions with remifentanil-propofol and either low-dose rocuronium or succinylcholine. Can J Anaesth. 2009 Jul;56(7):483-488
11 Anaesthesia and myocardial ischaemia/reperfusion injury. Frässdorf J et al. Br J Anaesth. 2009 Jul;103(1):89-98
Cardiovascular pre/post conditioning in association with anaesthesia is an increasingly topical issue in the literature. Fortunately this brief review article is more readable than most. It discusses the three-time frames in which cardioprotection against ischaemia-reperfusion injury can be induced: before ischaemia occurs, during ischaemia, and after the ischaemia at the onset of reperfusion. There are clearly methodological issues with studying ischaemia in humans so most of the current evidence comes from animal studies, which obviously limits the conclusions that can be drawn. The positive effects of volatile anaesthetics are most evident when given throughout the surgical procedure. Although contentious, volatile anaesthesia seems superior to propofol based anaesthesia. Morphine compared with fentanyl has been associated with improved cardioprotection. Other drugs which have exhibited some cardioprotective effect are xenon, helium, phenylephrine and remifentanil. The optimal duration of administration, dose and timing of cardioprotective drugs remain unknown. Important drugs and physical states that may interefere with cardioprotection include ketamine, thiopentone, beta-blockers, aprotinin, sulphonyureas and hyperglycaemia.
Take home message: There is evidence to suggest improved outcomes due to pre- and/ or post-conditioning in association with volatile anaesthesia in cardiac surgery but further study is required to enable development of optimal cardioprotective anaesthetic protocols.
For related reading this month: - Gourdin MJ et al. The impact of ischaemia-reperfusion on the blood vessel. Eur J Anaesthesiol. 2009 Jul;26(7):537-47. - Hu Z-Y et al. Mechanism of cardiac preconditioning with volatile anaesthetics. Anaesth Intensive Care. 2009 July;37(4):532-538.
12 Muscle relaxants and airway management. Calder I, Yentis S, Patel A. Anesthesiology. 2009 Jul;111(1):216-7; author reply 218-9. [Correspondence]
A series of heated letters in this journal documents interesting dialogue between airway experts regarding the use of muscle relaxants in the potentially difficult airway in an emergent setting. Calder et al feel that not administering a NMBD until ventilation has been demonstrated is an unsound practice. They believe that available evidence indicates that NMBD facilitates mask ventilation and that NMBDs are much more often the answer than the problem. Boylan et al who authored an editorial (Anes, 2008, 109;945-7) accompanying an article (Schmidt, Anes, 2008, 209;973-7) reply to these comments. They feel that careful judgment should always be exercised when using NMB in acute airway management, especially by inexperienced trainees. Likewise, Schmidt et al believe that there is not enough evidence at present to recommend the use of NMBDs for emergent intubation and that there is equipoise for the use of muscle relaxants for emergent intubations.
Take home message: There is dissent between airway experts about the place of muscle relaxants in the potentially difficult airway in the emergent setting.
See also: April Journal Watch (3);
Other articles of potential specific interest:
CARDIAC - Taneja R et al. Elevated activated partial thromboplastin time does not correlate with heparin rebound following cardiac surgery. Can J Anaesth. 2009 Jul;56(7):489-496 - Editorial: Spiess BD. A little coagulation knowledge can be dangerous! Can J Anaesth. 2009 Jul;56(7):478-482 -Greilich PE et al. The effect of epsilon-aminocaproic acid and aprotinin on fibrinolysis and blood loss in patients undergoing primary, isolated coronary artery bypass surgery: a randomized, double-blind, placebo-controlled, noninferiority trial. Anesth Analg. 2009 Jul;109(1):15-24.
AIRWAY - Savoldelli GL et al. Learning curves of the Glidescope, the McGrath and the Airtraq laryngoscopes: a manikin study. Eur J Anaesthesiol. 2009 Jul;26(7):554-8. - Turkstra TP et al. Cervical spine motion: a fluoroscopic comparison of the AirTraq Laryngoscope versus the Macintosh laryngoscope. Anesthesiology. 2009 Jul;111(1):97-101.
REGIONAL ANAESTHESIA - O'Donnell BDet al. Ultrasound-guided axillary brachial plexus block with 20 milliliters local anesthetic mixture versus general anesthesia for upper limb trauma surgery: an observer-blinded, prospective, randomized, controlled trial. Anesth Analg. 2009 Jul;109(1):279-83. - Fredrickson MJ et al. Speed of onset of 'corner pocket supraclavicular' and infraclavicular ultrasound guided brachial plexus block: a randomised observer-blinded comparison. Anaesthesia. 2009 Jul;64(7):738-44 - Liu SS et al. A prospective, randomized, controlled trial comparing ultrasound versus nerve stimulator guidance for interscalene block for ambulatory shoulder surgery for postoperative neurological symptoms. Anesth Analg. 2009 Jul;109(1):265-71. - Soeding P et al. Review article: anatomical considerations for ultrasound guidance for regional anesthesia of the neck and upper limb. Can J Anaesth. 2009 Jul;56(7):518-533.
GENERAL TOPICS - Rex C et al. Reversal of neuromuscular blockade by sugammadex after continuous infusion of rocuronium in patients randomized to sevoflurane or propofol maintenance anesthesia. Anesthesiology. 2009 Jul;111(1):30-5 - Cook TM et al. Litigation related to anaesthesia: an analysis of claims against the NHS in England 1995-2007. Anaesthesia. 2009 Jul;64(7):706-18. - Mongardon N et al. Pharmacological optimization of tissue perfusion. Br J Anaesth. 2009 Jul;103(1):82-8. - Baumann A et al. Refractory anaphylactic cardiac arrest after succinylcholine administration. Anesth Analg. 2009 Jul;109(1):137-40. - Parsons AJ et al. Carotid dissection: a complication of internal jugular vein cannulation with the use of ultrasound. Anesth Analg. 2009 Jul;109(1):135-6. -Srivastava A et al. Reversal of neuromuscular block. Br J Anaesth. 2009 Jul;103(1):115-29 - Fagerlund MJ et al. Current concepts in neuromuscular transmission. Br J Anaesth. 2009 Jul;103(1):108-14.
OBSTETRICS - McDonnell NJ et al. Analgesia after caesarean delivery. Anaesth Intensive Care. 2009 July;37(4):539-551. - Bergum D et al. Oxytocin infusion: acute hyponatraemia, seizures and coma. Acta Anaesthesiol Scand. 2009 Jul;53(6):826-7
PERIOPERATIVE MEDICINE - Krolikowska M et al. Mortality in diabetic patients undergoing non-cardiac surgery: a 7-year follow-up study. Acta Anaesthesiol Scand. 2009 Jul;53(6):749-58 - Bolsin SNC et al. Cardiac complications and mortality rates in diabetic patients following non-cardiac surgery in an Australian teaching hospital. Anaesth Intensive Care. 2009 July;37(4):561-567. - Editorial: Sessler DI. Long-term consequences of anesthetic management. Anesthesiology. 2009 Jul;111(1):1-4.
Written by Maryanne Balkin, July 2009
Feedback welcome: M.Balkin@alfred.org.au
Disclaimers:
1 Best attempts are made to include articles representative of recent publications but no attempt is made to include every important article.
2 Commentary & take home message is only one of many possible opinions/interpretations of the literature.
For other 2009 editions of journal watch: http://www.anaesthesiacases.com.au/cpd