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- Volume 14, Issue 1, 2008
Southern African Journal of Anaesthesia and Analgesia - Volume 14, Issue 1, 2008
Volume 14, Issue 1, 2008
Author M.F. NewmanSource: Southern African Journal of Anaesthesia and Analgesia 14 (2008)More Less
The brain is often a window to early changes in blood flow, tissue perfusion, or early neural damage manifested by a decline in higher cortical functions including recall memory and cognitive processing. The elderly population is particularly at risk of central nervous system injury, which may manifest as stroke and / or cognitive deterioration due to reduced cognitive reserve, as seen with aging-related cognitive decline. These changes in cognitive function are associated with reduced activities in daily living that substantially reduce the quality of life of the elderly, and can be magnified by physical or emotional stress in high-risk individuals.
Author H.J. PriebeSource: Southern African Journal of Anaesthesia and Analgesia 14, pp 92 –95 (2008)More Less
The aetiology of perioperative cardiac morbidity and mortality is multifactorial. With the many and diverse aetiological factors involved, it is highly unlikely that one single intervention will successfully improve cardiac outcome following noncardiac surgery. Based on increasing knowledge of the nature of atherosclerotic coronary artery disease, and in view of the poor positive predictive value of the non-invasive cardiac stress tests and the considerable risk of coronary angiography and coronary revascularisation in high-risk patients, the paradigm is shifting from an emphasis on extensive non-invasive preoperative risk stratification to an emphasis on a combination of selective non-invasive testing and aggressive pharmacological perioperative therapy. Perioperative plaque stabilisation by pharmacological means may well be one of the most important cardioprotective interventions.
Author J. MossSource: Southern African Journal of Anaesthesia and Analgesia 14 (2008)More Less
Methylnaltrexone (MNTX) (by Progenics Pharmaceuticals)* was developed to antagonise the peripheral adverse effects of opiates while preserving centrally mediated analgesia. MNTX is currently being evaluated to prevent or treat opiate-induced inhibition of GI motility in advanced illness (AI), chronic pain, and postoperatively (postoperative ileus (POI)). MNTX is the quaternary derivative of the opioid antagonist naltrexone.
In a preliminary randomised, double-blind, placebo-controlled study in human volunteers, the administration of small doses of morphine (3-5 mg) slowed GI transit, as measured by oral-cecal transit time, by 50%. These changes were reversed with MNTX (0.4 mg/kg IV) without influencing morphine-induced analgesia. In a subsequent human volunteer study, single oral doses of MNTX (ranging from 0.64 to 19.2 mg/kg) acted quite similarly.
Although the acute effects of opiates on GI motility proved to be completely reversible by MNTX, the efficacy of MNTX as a therapy in opiate-tolerant individuals represented a more complex problem of dose titration. To resolve this problem, a double-blind, placebo-controlled, randomised clinical trial was performed on 22 subjects undergoing chronic methadone maintenance therapy for addiction. Laxation occurred within one minute of injection of IV.MNTX in all subjects without withdrawal. The GI motility of methadone maintenance patients was exquisitely sensitive to MNTX (five times more sensitive in the chronic opiate users than in naïve subjects). Similar effects were noted with oral MNTX in 12 methadone maintenance subjects but over five hours. After subcutaneous (sc) administration, changes in oral cecal transit time occurred over a period of about 15 minutes.
While MNTX clearly worked in the setting of addiction, an important issue is whether response could be achieved in the setting of AI where co-morbidity is significant, and doses of opiates may be very high. A multi-institutional Phase 2b study of sc MNTX in 33 palliative care patients with opiate-induced constipation revealed dose-related laxation. More than 60% of the treated patients laxated, most within one hour, without significant side effects or any evidence of withdrawal. This was confirmed in a randomised double-blind placebo-controlled trial, in which 154 patients with AI received either a single sc dose of MNTX (0.15 or 0.3 mg/kg) or placebo with four weeks of open-label therapy. Sixty-two per cent laxated within four hours of their first drug injection vs 13% with placebo (p < 0.0001). Importantly, most patients responded within an hour of treatment, allowing a measure of predictability in these medically complex patients. In a second recently reported Phase 3 study of 133 AI patients, sc administration of MNTX induced laxation within four hours in 51.2% of severely constipated AI patients, more than three times the rate of placebo (15.5%), over a two-week period. For patients who responded to MNTX (0.15 mg/kg), median time to laxation was 30 minutes.
Author G. O'SullivanSource: Southern African Journal of Anaesthesia and Analgesia 14, pp 98 –100 (2008)More Less
Neuraxial analgesia remains the gold standard for achieving analgesia in labour. Many women, however, prefer to employ less invasive techniques to relieve pain during labour. Most non-neuraxial methods of analgesia will never provide complete pain relief during labour, but at best, represent techniques that allow a woman 'to cope' with her labour pain.
Source: Southern African Journal of Anaesthesia and Analgesia 14, pp 102 –106 (2008)More Less
The number of percutaneous coronary interventions (PCI) performed annually has increased rapidly over the last two decades. Coronary angioplasties are now commonly complemented with the insertion of coronary artery stents. Initially bare metal stents (BMS) were developed with drug-eluting stents (DES) subsequently being introduced. Drug-eluting stents reduce in-stent restenosis at the cost of prolonged anti-platelet therapy. While observational studies suggest that coronary artery bypass graft surgery protects against perioperative cardiac events in non-cardiac surgery, no such evidence exists for PCI. In order to prevent stent thrombosis, patients need to receive dual anti-platelet therapy (generally aspirin and clopidogrel) for four to six weeks with BMS, and at least one year with DES. Patients on dual anti-platelet therapy are at risk of severe bleeding during surgery. However, withdrawal of dual anti-platelet therapy is associated with the risk of stent thrombosis. The risk of cardiac complications seems to exceed the risk of bleeding, and maintenance of dual anti-platelet therapy is advocated whenever possible. Surgery in closed cavities (neurosurgery, intraocular surgery) necessitates the withdrawal of dual anti-platelet therapy. There is a significant risk of perioperative complications in patients who have DES, or recently inserted BMS, and consequently surgery should not be performed without a discussion involving the surgeon, cardiologist, anaesthetist, and the patient.
Author B.M. BiccardSource: Southern African Journal of Anaesthesia and Analgesia 14, pp 109 –115 (2008)More Less
South African vascular anaesthetic practice is strongly influenced by European and American literature. This is inappropriate, as the prevalence and aetiology of cardiovascular disease, the aetiology of the vascular pathology, and the vascular surgical outcomes in South African patients differ from those reported internationally. South African vascular surgical patients are at higher cardiac risk and have a higher mortality than that reported in the international literature.
Although cardiac clinical risk predictors are probably consistent globally, the epidemiological transition of cardiovascular disease and the socioeconomic consequences of apartheid have had a profound influence on the â??weightingâ?? of these risk factors in South Africans. Of the South African race groups, South African Indians have the highest cardiac mortality, secondary to a high prevalence of renal dysfunction, diabetes and cerebrovascular accidents. South African black patients now have a similar cardiovascular burden to that reported internationally. The perioperative cardiac mortality of black South Africans is lower than international comparisons, probably secondary to a cardioprotective lipid profile of these patients. Black South Africans have an unacceptably high non-cardiac mortality associated with vascular surgery. Access to medical therapy for South African vascular surgical patients is wholly inadequate, as only a quarter of vascular patients are on statin therapy.
Nearly 6% of South African vascular patients present with Human Immunodeficiency Virus (HIV) vasculopathy of predominantly two distinct clinical presentations: aneurysmal and occlusive vascular disease. Aneurysmal disease is associated with a worse long-term prognosis. The poor access to highly-active anti-retroviral therapy (HAART) for these patients is unacceptable.
It is imperative that practice guidelines based on South African epidemiological data be established, that clinical cardiac and HIV risk indices be developed specifically for South African vascular patients, that socioeconomic issues affecting outcome between race groups be addressed, and that access to statin therapy and HAART be improved.