1 Magnesium: an emerging drug in anaesthesia. Editorial: James MF. Br J Anaesth. 2009 Oct;103(4):465-7.
Magnesium sulphate attenuates arterial pressure increase during laparoscopic cholecystectomy. Jee D et al. Br J Anaesth. 2009 Oct;103(4):484-9.
Controlled hypotension for middle ear surgery: a comparison between remifentanil and magnesium sulphate. Ryu JH et al. Br J Anaesth. 2009 Oct;103(4):490-5.
An editorial accompanies two articles exploring the benefits of intravenous magnesium in attenuation of perioperative haemodynamics. As well as blocking release of catecholamines and acting as a calcium antagonist, magnesium is also non-competitive inhibitor of NMDA receptors. Therapeutic uses of magnesium continue to emerge and include the well-established prevention and treatment of eclamptic convulsions, arrhythmia treatment (AF, torsade de pointes), vasodilator actions and alpha-adrenergic antagonism in conditions of catecholamine excess including phaeochromocytoma, neuronal and myocardial protection, treatment of severe asthma and tocolysis. The study by Jee is a placebo-controlled, randomized study (n=32) of the effect of a single bolus dose of magnesium sulphate (50 mg/kg; 0.5 mg/kg of 10% magnesium sulphate) on the haemodynamic and catecholamine responses to the production of pneumoperitoneum for laparoscopic cholecystectomy. In this study, magnesium limited the haemodynamic response to capnoperitoneum, prevented the increase in catcholamines seen in the control group and attenuated increases in vasopressin release. The study obviously has particular relevance to laparoscopic management of phaeochromocytoma. In the other study, Ryu report on a randomized, controlled trial (n=80) comparing infusions of remifentanil with magnesium sulphate for the maintenance of controlled hypotension during middle ear surgery. Similar, satisfactory levels of hypotension were achieved in both groups, but magnesium provided better control of arterial pressure in the immediate post-extubation period. The investigators also observed better analgesia and less shivering and PONV in the magnesium group. However, this study has notable features and several limitations. Neither group received any intraoperative analgesia (other than remifentanil in the remi group), so some degree of hyperalgesia would be expected in the remi group. There is no mention as to whether the surgeons used LA intraoperatively. Likewise, it is difficult to know whether more pain may have contributed to the higher incidence of PONV in the remi group. The only anti-emetic used was metoclopromide and was administered PRN in PACU. Although many endpoints are reported in this study, the sample size was calculated based on the predicted incidence of rescue analgesia. Both of these studies support the fact that magnesium has a large safety margin but it can potentiate non-depolarising neuromuscular blockers and in circumstances of massive overdose, hypotension can ensue & ventilatory support may be required.
NB: 1 g magnesium sulphate=4 mmol Mg2+; plasma concentration of 2-4 mmol/l accepted therapeutic range Mg2+; toxicity can be antagonised with IV calcium gluconate given IV in bolus dose of 2.5-5 mmol (Watson et al. CEACCP, 2001)
Take home message: A role for magnesium infusions for cardiovascular control in anaesthesia and critical care is gradually becoming established.
2 The association of malignant hyperthermia and unusual disease: when you're hot you're hot or maybe not. Editorial: Davis PJ et al. Anesth Analg. 2009 Oct;109(4):1001-3
Malignant hyperthermia-associated diseases: state of the art uncertainty. Editorial: Litman RS et al. Anesth Analg. 2009 Oct;109(4):1004-5.
Malignant hyperthermia and muscular dystrophies. Gurnaney H et al. Anesth Analg. 2009 Oct;109(4):1043-8.
Malignant hyperthermia, coexisting disorders, and enzymopathies: risks and management options. - Benca J et al. Anesth Analg. 2009 Oct;109(4):
The myotonias and susceptibility to malignant hyperthermia. -Parness J et al. Anesth Analg. 2009 Oct;109(4):1054-64
The relationship between exertional heat illness, exertional rhabdomyolysis, and malignant hyperthermia. Capacchione JF et al. Anesth Analg. 2009 Oct;109(4):1065-9.
Malignant hyperthermia-like syndrome and carnitine palmitoyltransferase II deficiency with heterozygous R503C mutation. Hogan KJ et al. Anesth Analg. 2009 Oct;109(4):1070-2.
Core myopathies and risk of malignant hyperthermia. Klingler W et al. Anesth Analg. 2009 Oct;109(4):1167-73. Review.
This issue of AA brings together a collection of papers focused on the prevalence of malignant hyperthermia (MH), the possible association of exertional heat illness with MH, and the association of myotonias, muscular dystrophies, core myopathies, and enzymopathies with MH. For most neuromuscular disorders historically linked with MH, evidence for a causal relationship with MHS is weak. This group includes: muscular dystrophies, myotonias, osteogenesis imperfecta, arthrogryposis, and the enzymopathies (except possibly carnitine palmitoyltransferase II deficiency). The phenotype of almost all persons with a genetic susceptibility to MH does not include hypotonia or muscle weakness. Conversely, there are a limited number of relatively rare disease entities that are closely linked to MH susceptibility. These include central core and multiminicore myopathies, King-Denborough syndrome, Brody myopathy and possibly hypokalaemic periodic paralysis. Likewise, although evidence is inconclusive, it may be advisable to provide non-MH triggering anaesthesia to patients with unexplained exertional heat illness or exertional rhabdomyolysis, until definitive diagnostic muscle contracture testing can be performed. Regardless, anaesthetic management of patients with muscle diseases is challenging. In addition to unpredictable sporadic responses, such as rhabdomyolysis and hypermetabolic stimulation, more predictable risks are associated with respiratory and bulbar muscle weakness, myocardial involvement, and difficult airway anatomy. Hence, a formal clinical evaluation of respiratory and bulbar muscle function, appropriate to the age of the patient, is a mandatory aspect of the preoperative evaluation of patients with congenital myopathies. Patients with muscle disease should also have baseline serum potassium and CK measured. All anaesthetic techniques and drugs are associated with increased risk in patients with myopathies. Boys with Duchenne and Becker muscular dystrophy are at risk for life threatening hyperkalaemia and rhabdomyolysis when anaesthetized with MH triggering drugs. Likewise, patients with myotonia will likely develop muscle rigidity with suxamethonium that is not related to MH. The use of suxamethonium should generally be discouraged in patients with neuromuscular disease. The use of anticholinesterases is also generally not recommended in patients with neuromuscular diseases. Because of the rarity of the disorders discussed and their underlying genetic heterogeneity, absolute certainty with regard to MHS may never be established. Although the decision to proceed with a non-triggering versus a potentially triggering anaesthetic can be more fraught in paediatrics, it is important to note that there is no case reports of MH or an MH-like event in patients with rare enzyme deficiencies and weak association with MHS receiving brief exposure (i.e the time it takes for inhaled induction of anaesthesia and placement of an IV catheter). That said, clinicians should act on the side of caution if perioperative signs and symptoms of MH present themselves (in any patient), and treat the event as a potential MH episode. There is no significant downside to treatment with dantrolene in suspected but not true MH. Potential disaster awaits if true MH is undiagnosed and left untreated.
Take home message: Central core and multiminicore myopathies, King-Denborough syndrome, Brody myopathy and possibly hypokalaemic periodic paralysis are rare neuromuscular diseases with an established link to MH sensitivity. For many other neuromuscular diseases, the link remains weak & inconclusive. Regardless, serious consideration should be given before using suxamethonium and possibly volatile agents when anaesthetizing patients with significant neuromuscular disease who are potentially at risk of hyperkalaemia, rhabdomyolysis and hypermetabolic syndromes in response to these agents.
For related reading this month: Brady JE et al. Prevalence of malignant hyperthermia due to anesthesia in New York State, 2001-2005. Anesth Analg. 2009 Oct;109(4):1162-6. Carpenter D et al. Genetic variation in RYR1 and malignant hyperthermia phenotypes. Br J Anaesth. 2009 Oct;103(4):538-48.
See also: January Journal Watch (9)
3 GO Project teams. Global oximetry: an international anaesthesia quality improvement project. Walker IA et al; Anaesthesia. 2009 Oct;64(10):1051-60.
Extending the WHO 'Safe Surgery Saves Lives' project through Global Oximetry. Editorial: Merry AF et al. Anaesthesia. 2009 Oct;64(10):1045-8.
The Global Oximetry (GO) is a part of the WHO Second Global Patient Safety Challenge/Safe Surgery Saves Lives project that recognizes the rising importance of surgery to public health. Estimates put anaesthesia mortality in some developing countries, where anaesthesia providers have little training and appallingly inadequate resources, at 1000 times that of industrialized countries. Despite the fact that pulse oximetry is considered mandatory in many countries and a recommended international standard, there are still places where oximeters are simply not available. A widely criticized 2002 Cochrane review had negative conclusions regarding the beneficial impact of oximetry but nonetheless, anaesthetists are collectively, completely convinced that oximetry is essential to safe anaesthesia because it enables detection of hypoxia and intervention early enough to avert disaster and potential cardiac arrest, ischaemic injury and mortality. It is on this background that pilot projects have been undertaken in regions of Uganda, Vietnam (both low-income countries), the Philippines and India (both low-middle income countries) to investigate the utilization of pulse oximetry. Eighty-four donated pulse oximeters were distributed and formal training of oximeter naïve practioners undertaken. The pulse oximeter gap was defined as the difference between observed and expected number of pulse oximeters in the OR or acute care locations. The study found a substantial gap in pulse oximetry in the OR for patients in 3 out of 4 regions (all except the Philippines) and a sizable oximetry gap in acute care areas in all four regions. After oximetry education, provider logbook data revealed most responses to desaturation were appropriate. A survey of anaesthesia providers after the introduction of oximeters showed that they believed oximeters were essential for patient safety. Challenges encountered in the project included limited finance, language barriers, unfamiliarity of providers with oximetry, difficulties with data collection, oximeter malfunction and effecting sustained change in practice. It is sobering to contemplate that large populations living in resource challenged regions don’t have access to basic anaesthesia monitoring that many of us would expect the local veterinary hospital to utilize as standard care.
Take home message: “The WHO initiative to ensure that every patient undergoing anaesthesia has routine, continuous oximetry is bold, innovative and lifesaving. It is unlikely that anyone reading this editorial would volunteer to undergo anaesthesia without oximetry; no patient, anywhere, should have to do so either.“ (Merry et al, Anaesthesia, Oct 2009)
See also: January Journal Watch (2)
4 Perioperative beta-Blockade, Discontinuation, and Complications: Do You Really Know It When You See It? [Editoria l] London MJ. Anesthesiology 2009 Oct;111(4):690-4.
Effect of beta-blocker Prescription on the Incidence of Postoperative Myocardial Infarction after Hip and Knee Arthroplasty. van Klei WA et al. Anesthesiology. 2009 Oct;111(4):712-24 [Article]
This retrospective cohort study (n=5,158) evaluated associations of beta-blocker prescription in patients undergoing elective hip or knee arthroplasty with perioperative MI (POMI) in the first week post surgery. The patients were divided into 3 groups: beta-blocker ordered on the day of surgery and continued, ordered on the day of surgery and discontinued or never ordered on the day of surgery. The study data were obtained exclusively by linking administrative and clinical databases and, due to the limitations of this data, chronic preadmission outpatient use was not considered. Of the 77 patients in the study sustaining POMI (1.5%) 22 of 740 (2.9% occurred in the continuous group, 20 of 252 (7.9%) occurred in the discontinued group, and 35 of 4,166 (0.8%) occurred in the no beta-blocker group. Discontinuation of beta-blocker prescription was significantly associated with POMI (OR 2.0; 95% CI 1.1-3.9) and death (OR 2.0; 95% CI 1-3.9). A lower postoperative haemoglobin was also found to independently contribute to risk. There was no routine surveillance protocol for POMI, so troponin T measurements were left to the discretion of the treating team and silent post-operative MI (likely a majority) may have been missed. The accompanying editorial discusses the limitations of this study given its nonrandomized design and presumed unmeasured cofounders. No haemodynamic data was evaluated and no data pertaining to likely relevant co-variates such as anaesthetic technique, pain management and reasons for discontinuing beta-blocker therapy was collected. The author of the editorial emphasizes that forgetting to order (or discontinue based on obvious new contraindications) a chronic or newly instituted medication is never acceptable and should always be considered a breach of quality medical care.
Take home message: Accumulating evidence supports the ACC/AHA Class 1 Level of Evidence C recommendation not to withdraw B-blocker therapy perioperatively.
See also: May Journal Watch (12)
5 Cognitive aid for neonatal resuscitation: a prospective single-blinded randomized controlled trial. Bould MD et al. Br J Anaesth. 2009 Oct;103(4):570-5
This small study was conducted with the knowledge that exposure to neonatal resuscitation may be infrequent and retention of skills and knowledge after neonatal resuscitation courses (NRP) is known to be problematic. The investigators designed an RCT to prospectively investigate the effect of a cognitive aid on the performance of simulated neonatal resuscitation with a group of anaesthesia residents (n=32). All of the residents had previously completed the NRP course. Subjects in the intervention group were told that there would be a poster containing accurate information they could use during the 6-minute simulated scenario. Test scores were not different between the control group and the intervention group and when evaluated by a neonatologist, none of the subjects correctly performed all life-saving interventions necessary to pass the checklist. A minority of the intervention group used the cognitive aid frequently. The authors discuss the fact that poor retention of resuscitation skills echoes similar finding in other resuscitation courses and in the management of critical incidents by anaesthetists. The results of this small study also contrast with the use of cognitive aids in industries such as aviation which encourage pilots to avoid dependence on memory when decision making in critical situations.
Take home message: Retention of skills after neonatal resuscitation courses is poor.
6 Obstructive sleep apnea is not a risk factor for difficult intubation in morbidly obese patients. Neligan PJ et al. Anesth Analg. 2009 Oct;109(4):1182-6.
This prospective observational study (n=180), recruited morbidly obese patients undergoing bariatric surgery (mean BMI 49.4 kg/m2). Sixty-eight percent of the study patients had polysomnography-proven OSA (mean AHI 31.3). The primary outcome measure was correlation between AHI and difficult intubation, as quantified by the number of intubation attempts, the C&L view, the need for rescue airway management or case cancellation for failed tracheal intubation. Secondary outcome measures were correlation between intubation attempts and C&L grade with BMI, neck circumference, mallampati score, and gender. Of note, the first 3 laryngoscopic attempts were performed by an anaesthesiology resident. Six patients required 3 or more intubation attempts. Investigators reported an 8.3% incidence of C&L Grade≥3 and 3.3% rate of difficult intubation, which is much lower than similar published studies. There were no failed intubations and no rescue airway manoeuveres required, so the investigators concluded that there is no relationship between the presence and severity of OSA, BMI or neck circumference with difficult intubation. The authors speculate that their attention to achieving the ramped position for intubation with the head, shoulder, and upper body elevated above the chest is a key component in the relatively low rate of difficult intubation. A glaring omission from the study is any mention of sample size calculation in order to validate their initial hypothesis. Given the obvious challenges with anaesthetizing patients with this degree of obesity, it is disappointing that there was no detailed reporting of other adverse airway events such as difficult mask ventilation or desaturations, especially in the sub-group of patients who required 3 or more intubation attempts. Likewise, the authors make no mention of other considerations of morbid obesity with respect to airway management if difficulty with intubation was to be encountered such as difficulty with mask ventilation (OSA a risk factor in a recent large study-see JW April (3)) and time to desaturation with apnoea. It is well established that amongst almost all populations, failed intubation is a rare event. However, the consequences of an inadequately managed airway can be debilitating or fatal, so the stakes are obviously a lot higher in those patients who may also prove difficult to oxygenate.
Take home message: This study suggests that the majority of morbidly obese patients will not present difficulties with intubation if due attention is paid to achieving an optimal ‘ramped’ position.
See also: April Journal Watch (3)
7 Variation in hospital mortality associated with inpatient surgery--an S.O.S. Editorial: Jacobs DO. N Engl J Med. 2009 Oct 1;361(14):1398-400.
Variation in hospital mortality associated with inpatient surgery. Ghaferi AA et al. N Engl J Med. 2009 Oct 1;361(14):1368-75. [Abstract]
The main purpose of this multicentre observational study (n=84,730) was to determine the relationship between overall post-surgical hospital mortality, incidence of perioperative complications and mortality after major complications. The investigators used the American College of Surgeons National Surgical Quality Improvement Program database to identify a cohort of inpatients who had undergone general or vascular surgical procedures that have rates of death of more than 1% from 2005 to 2007 in more than 150 hospitals. They first ranked hospitals according to their risk-adjusted overall rate of death and divided them into five groups before assessing the incidence of overall and major complications and rate of death within each quintile. Rates of death varied widely across hospital quintiles, from 3.5% in very-low-mortality hospitals to 6.9% in very-high-mortality hospitals. Hospitals with either very high mortality or very low mortality had similar rates of overall complications (24.6% and 26.9%, respectively) and of major complications (18.2% and 16.2%, respectively). Mortality in patients with major complications was almost twice as high in hospitals with very high overall mortality as in those with very low overall mortality (21.4% vs. 12.5%, p<0.001). The procedures associated with the greatest number of perioperative deaths were colectomy, repair of AAA, lower-extremity bypass and above or below knee amputations. Approximately 1 in 6 patients who underwent general or vascular surgery in this study had a surgical complication and more than half of such complications were serious. Complications that were associated with high mortality included: acute renal failure, septic shock, AMI, CVA and postoperative bleeding. Increasingly, there is evidence that postoperative complications are more closely related to patient factors than to quality of care itself. Unfortunately exploration of the role of anaesthesia related mishaps, morbidity and mortality is beyond the scope of the study. Study authors speculate that ‘failure to rescue’ patients who suffer post-operative complications may be an important mechanism underlying hospital mortality associated with surgery. The accompanying editorial emphasizes that the observational study design means that the mechanisms that are responsible for differences in death rates after complications remain elusive. Limitations of this study include reliance on the NSQIP database that did not collect all data relevant to study endpoints as well as hospital selection bias because the study only collected data from hospitals participating in quality-improvement activities.
Take home message: In the effort to reduce rates of surgical mortality, the value of avoiding perioperative complications is obvious, however timely recognition and the effective management of complications when they occur, is also crucial to reducing mortality. The potential role of anaesthetists in optimizing perioperative care remains to be determined.
For related reading this month: Editorial: Surgical research: the reality and the IDEAL. Lancet. 2009 Sep 26;374(9695):1037.
8 Orkin FK et al. Substrate for Healthcare Reform: Anesthesia's Low-Lying Fruit. [Editorial] Anesthesiology. 2009 Oct;111(4):697-8
A Population-based Analysis of
Outpatient Colonoscopy in Adults Assisted by an
Anesthesiologist. Alharbi O et al.
Anesthesiology. 2009 Oct;111(4):734-40
[Abstract]
The authors of this study performed a population-based cross-sectional analysis using Canadian health administrative databases from 1993-2005 to investigate the impact of patient, physician and institutional factors in determining the presence of an anesthesiologist for colonoscopy sedation. American gastroenterology associations agree that routine anesthesiologist assistance with endoscopy is not warranted for average risk patients, however, non-anesthesiologist sedationists are not usually permitted to use propofol in North America. After reviewing 1,838,879 colonoscopies, the investigators found that the proportion of anesthesiologist assisted colonoscopies rose from 8.4% in 1993 to 19.1% in 2005. Patients in low volume community hospitals were five times more likely to receive anesthesiologist-assisted colonoscopy than patients in high volume hospitals. Less than 1% of colonoscopies in academic hospitals were anesthesiologist-assisted. Surgeons were more likely to perform anesthesiologist-assisted colonoscopy and remarkably, there was no association identified linking patient risk to anesthesiologist assistance. Unfortunately due to retrospective data collection, relying exclusively on administrative databases, there was no information available re proceduralist assessment of the adequacy of sedation provided, patient satisfaction and procedural morbidity rates. The author recommends further evaluation of patient and institution factors is warranted to ensure anesthesiologists’ services are allocated in a manner that is most beneficial to patients and the healthcare system. The accompanying editorial discusses the fact that historically, deaths have been associated with non-anesthesiologist sedation and emphasizes the narrow therapeutic index of propofol. The discussion also recognizes the demand for healthcare is infinite and resources are limited, so rationing is universal in healthcare systems. The editorial author also highlights the troubling study finding that anesthesiologist involvement was not associated with patient acuity and suggests that anesthesiologist involvement (with propofol) in colonoscopy confers no major patient benefit over sedation provided by other personnel (using older, less preferred drugs). However, one could also argue that is a ‘big call’ given the limited data available from this study and would ideally be confirmed with a large, multi-centre, prospective RCT and complete data collection followed by unbiased interpretation.
Take home message: Some North American experts feel that anaesthesiologist presence for colonoscopy is a low benefit service resulting in disproportionate expenditures and represents an ideal substrate for healthcare reform.
9 Pre-operative coronary revascularisation before non-cardiac surgery: think long and hard before making a pre-operative referral. Editorial: Mythen M. Anaesthesia. 2009 Oct;64(10):1048-50.
A meta-analysis of the prospective randomised trials of coronary revascularisation before noncardiac vascular surgery with attention to the type of coronary revascularisation performed. Biccard BM et al. Anaesthesia. 2009 Oct;64(10):1105-13.
The aim of this meta-analysis was to analyse the efficacy of coronary revascularization prior to noncardiac vascular surgery, using data from prospective randomized trials and present outcomes according to whether the patients had pre-operative PCI or CABG. Only prospective randomized trials of pre-operative coronary revascularisation that reported mortality and non-fatal MI in patients undergoing vascular surgery were included. This effectively meant that only 2 trials were eligible for inclusion: the Coronary Artery Revascularisation Prophylaxis Study (CARP; n=510) and the Dutch Echocardiographic Cardiac Risk Evaluation Applying Stress Echo (DECREASE-V; n=101). Notable features of these studies include: a high ratio of patients screened to patients recruited, a higher risk profile in the DECREASE-V study, a large discrepancy between sample sizes of the two studies and the fact that DECREASE-V was only designed as a pilot study. In the CARP study, 41% (99/240) patients who underwent revascularization had CABG and 59% (141/240) had PCI. In the DECREASE-V study, 35% (17/49) patients underwent CABG and 65% (32/49) patients had PCI. The meta-analysis found that when comparing CABG and PCI, CABG had a trend to less deleterious effects on the composite outcome of death and nonfatal MI at 30 days when compared with PCI, which was subsequently statistically significant for the late composite outcome. However, CABG was associated with a trend to worse outcome for all 30-day events. The authors speculate that the significantly worse 30-day outcomes they observed in the PCI group in comparison to optimal medical therapy, and the significantly worse late composite outcome when compared to CABG, may be a result of both stent associated complications and incomplete revascularisation. The largest cohort publications have shown that mortality following noncardiac surgery is significantly increased for up to 90 days following insertion of a BMS and may be increased up to a year following insertion of a DES. Non-cardiac surgery followed an average of 42 days after PCI in the CARP trial and 31 days after PCI in the DECREASE-V study. In the CARP trial, 90% of the patients who had PCI received BMS and none had DES. In the DECREASE-V study, 30 patients had DES and 2 patients had BMS. In the CARP study, 45% of patients in the PCI group who underwent abdominal surgery had their anti-platelet therapy interrupted with no bridging therapy instituted. In the DECREASE-V study, antiplatelet therapy (aspirin and clopidogrel) was continued in the perioperative period. When interpreting the results of this meta-analysis, it is also imperative to consider that neither of the studies was designed to study the superiority of one method of revascularisation over the other and local investigators chose PCI or CABG based on the perceived benefits on a case by case basis in both studies. The meta-analysis included RCTs but randomization (revascularisation vs medical therapy) was not relevant to the metanalysis study question and the analysis is underpowered to assess this issue. PCI and CABG groups were unequal and there are multiple potential confounding factors such as severity of CAD, other comorbid conditions, unfavourable anatomy and perceived urgency of surgical procedure.
Take home message: The most compelling result of this meta-analysis is to support the well-established fact that post-operative outcomes are worse in patients who have recently had a coronary stent. In keeping with ACC/AHA guidelines, current evidence suggests coronary revascularisation prior to non-cardiac surgery should only be considered for patients in whom it would be indicated in the absence of surgery.
See also: January Journal Watch (10)
10 Primary versus Secondary Outcomes in Gargantuan Studies. [Editorial] Flood P. Anesthesiology. 2009 Oct;111(4):704-5
The Labor Analgesia Examining Group (LAEG). Epidural Analgesia in the Latent Phase of Labor and the Risk of Cesarean Delivery: A Five-year Randomized Controlled Trial. Wang F et al; Anesthesiology. 2009 Oct;111(4):871-80 [Article]
This large Chinese RCT (n=12,793) tested the hypothesis that patient controlled epidural analgesia given at a cervical dilation of 1 cm or more does not increase the risk of prolonged labour or LUSCS. Patients were randomized to an early epidural (cervical dilation at least 1 cm) or delayed epidural (cervical dilation at least 4 cm). The women were treated with pethidine until the assigned cervical dilation was reached. The duration of labour from analgesia request to vaginal delivery was equal in both groups (11.3+/-4.5 hours for an early epidural and 11.8+/- 4.9 hours for delayed epidural group). No statistically significant difference in the rate of LUSCS was observed between the two groups on the intention-to-treat analysis (23.3% vs 22.8% in the early and delayed group respectively). Notably, although it appears the sensory block was tested, patient satisfaction & VAS scores seems to be the only measurement recorded that would give any indication that the block was actually working adequately and there was no mention of a failed block rate. Factors which may limit generalizability to our patient population include labour epidural rate of 80% in nulliparous women. The accompanying editorial is critical of the investigators reporting on 29 secondary outcomes because large trials can identify spurious and trivial associations in secondary endpoints. The editorial author suggests such findings should be only considered a novel hypothesis that requires follow-up as a primary endpoint in a subsequent RCT.
Take home message: In keeping with previous publications, this study demonstrates that there is no clinically important relationship between epidural anaesthesia given as early as 1 cm cervical dilation and (1) LUSCS rate (2) labour duration and (3) rate of instrumentation.
11 A comparison of intravenous oxycodone and intravenous morphine in patient-controlled postoperative analgesia after laparoscopic hysterectomy. Lenz H et al. Anesth Analg. 2009 Oct;109(4):1279-83.
This RCT (n=91) investigated dose requirements, pain relief, and side effects of oxycodone versus morphine after laparoscopic hysterectomy. The accumulated oxycodone consumption was less than morphine (13.3+/-10.4 mg vs 22.0+/-13.1 mg; p=0.001). Of note, all patients received a non-relaxant TIVA GA with propofol/remifentanil and both groups received 0.07 mg opioid/kg 10-15 mins before the end of surgery. VAS scores were lower for oxycodone patients but only for the first hour post-op, after which no statistically significant differences were observed. Perhaps more importantly, the overall sedation level for 24 hours post-operatively was significantly less for the oxycodone group compared to the morphine group (p=0.006). There were no significant differences in the incidence of nausea, vomiting or itching. The investigators feel that the results suggest oxycodone maybe more potent for visceral versus somatic pain.
Take home message: This study found that oxycodone was more potent than morphine for visceral pain relief but not for sedation.
12 Transversus abdominis plane block: what is its role in postoperative analgesia? Editorial: Bonnet F et al. Br J Anaesth. 2009 Oct;103(4):468-70.
Analgesic efficacy of ultrasound-guided transversus abdominis plane block in patients undergoing open appendicectomy. Niraj G et al. Br J Anaesth. 2009 Oct;103(4):601-5.
This RCT (n=52) randomized patients undergoing open appendicectomy to receive unilateral US guided TAP block or standard care in addition to PCA morphine, regular paracetamol and NSAIDs. The investigators found US guided TAP block significantly reduced VAS scores immediately postoperatively and reduced postoperative morphine consumption in the first 24 hours. A major limitation of the study was there was no attempt to test the block to ice in PACU and two patients in the TAP group ‘apparently’ had a failed block. The accompanying editorial discusses the emerging analgesic efficacy pertaining to TAP blocks in abdominal surgery, hysterectomy, retropubic prostatectomy and LUSCS. The editorial author’s suggestion that TAP blocks have not been compared to ‘gold standard’ analgesic techniques such as epidural analgesia does not seem very practical considering that an epidural would not be considered for most procedures where TAP block has shown benefit. Recent evidence has indicated that the standard approach to the TAP is likely to only reliably anaesthetize T10-L1 dermatomes, so TAP blocks are unlikely to provide much benefit if the procedure is laparoscopic unless ports are inserted below the umbilicus such as in the rather strange study protocol where all the ports for a lap chole were inserted below the umbilicus (El-Dawlatly, BJA. June 2009).
Take home message: TAP block has potential benefits as part of a balanced postoperative analgesic regimen for patients undergoing open appendicectomy and other operations with the incision predominantly below the umbilicus.
See also: July Journal Watch (7)
Other articles of potential specific
interest: (Click here)
Written by Maryanne Balkin, October 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