Des Gorman

The clinical toxicology of carbon monoxide.

Carbon monoxide (CO) is a dangerous exogenous poison and an essential endogenous neurotransmitter. This gas when inhaled has an anaesthetic effect, which is poorly understood, but which may be fatal if compensatory mechanisms are exhausted, if cardiac oxygen (O(2)) needs exceed myocardial oxygenation and/or if apnoea or asphyxia onsets. Although there is considerable evidence that hypoxia occurs late in CO poisoning, both the treatment of acutely poisoned people and environmental exposure limits are largely based on a hypoxic theory of toxicity. The significance of recent demonstrations of increased endogenous CO and NO production in neurons of animals exposed to exogenous CO, and of a related sequestration of leucocytes along the endothelium and subsequent diapedesis is also not fully understood, but may in part explain both acute and delayed deleterious effects of a CO exposure. Delayed brain injuries due to a CO exposure may be preventable by hyperbaric O(2). However, the ideal dose of O(2) in this context, if any, is unknown and other potential treatments need to be tested.

Cerebral protection by lidocaine during cardiac operations.

BACKGROUND Lidocaine improves outcome in animal brain injury models. Cardiac operations often cause postoperative neuropsychological (NP) impairment. We investigated cerebral protection by lidocaine in cardiac surgical patients. METHODS Sixty-five patients undergoing left heart valve procedures completed 11 preoperative NP tests, a self-rating inventory for memory, and inventories measuring depression and anxiety. These were repeated 10 days, 10 weeks, and 6 months postoperatively. Patients received a 48-hour double-blinded infusion of either lidocaine in a standard antiarrhythmic dose or placebo, beginning at induction of anesthesia. A postoperative deficit in any test was defined as decline by more than or equal to the group preoperative standard deviation. In addition, sequential postoperative percentage change scores were calculated for each patient in all NP tests and the inventories for memory, depression and anxiety. RESULTS Forty-two patients completed all three reviews, 8 completed two reviews, and 5 patients were reviewed once. Significantly more placebo patients had a deficit in at least one NP test at 10 days (p<0.025) and 10 weeks (p<0.05). The lidocaine group achieved superior sequential percentage change scores in 6 of the 11 NP tests (p<0.05) and in the memory inventory (p<0.025). There were no group differences in the remaining NP tests or the depression and anxiety inventories. CONCLUSIONS These data show that cerebral protection by lidocaine, which is unrelated to any effect on depression or anxiety, and is at a level that is noticed by the patients.

Venous air in the bypass circuit: a source of arterial line emboli exacerbated by vacuum-assisted drainage

BACKGROUND Arterial emboli cause neurocognitive deficits in cardiac surgical patients. Carotid artery emboli, detected ultrasonically, have been observed after venous air entrainment into the cardiopulmonary bypass circuit. We investigated in vitro the extent to which venous air affected emboli detected in the arterial line downstream from a 40-microm filter. METHODS Using salvaged clinical cardiopulmonary bypass circuits, fixed volumes of air were introduced into the venous return line at unrestricted rates and at fixed rates using gravity venous drainage and vacuum-assisted venous drainage. Emboli counts were recorded distal to the arterial line filter using a 2-MHz pulsed-wave Doppler monitor. Emboli counts were similarly recorded after the introduction of carbon dioxide into the venous return line instead of air. RESULTS The number of emboli rose with increasing volumes of entrained venous air (p < 0.001), and there was an almost tenfold increase with vacuum-assisted venous drainage (p < 0.0001) compared with gravity venous drainage. Venous air was entrained at a significantly faster rate under vacuum-assisted venous drainage (p < 0.0001). When the entrainment rate of venous air was fixed, the difference in emboli numbers recorded for gravity and assisted venous drainage was not significant. There was a significant reduction in arterial line emboli when carbon dioxide rather than air was entrained under both vacuum-assisted and gravity drainage (p < 0.001). CONCLUSIONS Entrained venous air during cardiopulmonary bypass is a potential hazard, particularly during vacuum-assisted venous drainage. Every effort should be made to avoid venous air entrainment.

The effect of carbon monoxide on oxygen metabolism in the brains of awake sheep

Eight conscious chronically instrumented sheep were exposed to 1% inspired carbon monoxide (CO) for 35 min. In all sheep, carboxyhaemoglobin (COHb) levels at the end of the exposure were approximately 65%. Mean arterial blood pressure was unchanged with the exception of 2 sheep in which administration was stopped at 25 min following the sudden onset of hypotension. Oxygen delivery to the brain was sustained throughout the administration of CO due to a significant increase in cerebral blood flow (CBF). There was no evidence of either a metabolic acidosis or of lactate production by the brain suggesting the brain did not become hypoxic during the time-course of this study. Despite the apparent lack of hypoxia, oxygen consumption by the brain fell progressively and the sheep showed behavioural changes which varied from agitation to sedation and narcosis. The mechanism of these changes was therefore probably unrelated to hypoxia, but may have been due to raised intracranial pressure or a direct effect of CO on brain function. It is proposed that the time-course of progressive CO poisoning includes a phase in which CBF is elevated, blood pressure is unchanged and the brain is normoxic despite high COHb levels, but that this situation can rapidly evolve into a phase of haemodynamic collapse and severe hypoxia.

On the maldistribution of the medical workforce

At a recent medical education conference (MedEd 2007), the keynote speakers, Drs Haikerwal and Horvath, presented a common viewpoint that the ‘pendulum had swung too far’ to subspecialist practice. There are 48 general physician trainees in Australia, about a quarter of the number of either relevant vacancies (The Internal Medicine Society of Australia and New Zealand estimate) or the Royal Australasian College of Physians (RACP) cardiology trainees. Although problems for generalists and their patients are global, solutions need to be local. In New Zealand, we are ‘contracted’ to develop a local medical workforce and are obliged by way of the Treaty of Waitangi to maintain Maori taonga, which include health. Consequently, attention to workforce maldistributions in our medical programme is not discretionary. Medical workforce maldistributions can be variously disciplinary, cultural and demographic. The already-cited disciplinary maldistribution within the RACP contrasts with the relative economic and outcome utility of general scopes of practice. A generalist perspective is an advantage for clinical decisions, which involve concepts of relative benefit, and needs to be valued. There is little comfort for either Americans or Australians and New Zealanders in the related observations that the number of US graduates entering general practice training schemes decreased by 51% between 1998 and 2006 and more than half of all general practice trainees in the USA in 2006 were overseas graduates. These data suggest a close alignment of career interest and remuneration. Generalists will be disadvantaged as long as health financiers place an excess value on procedures. Fortunately, this driver of maldistributions should be easily fixed through remunerative and service parity. In addition to relatively lower remuneration and status, general physicians and trainees often have disproportionate amounts of on-call duties. The recommendations of the original ‘relative values’ study were not ratified federally, but we are delighted that new attendance items for complex assessments by physicians have been included in the 2007 Australian Budget. The anticipated ‘cost of health’ in Australia and New Zealand by 2020 may be such that politicians might at last override the selfinterests of the financially privileged elements of the medical profession. Judicious incentives, such as debt forgiveness for entering training schemes leading to jobs of need and high utility, may be helpful. The effects of the dual experiments of ‘bonding’ 25% of Australia’s medical students and of another 25% being domestic full fee payers are being watched with interest. Other frequently perverse drivers are the relative status of different medical disciplines and the effect of training schemes that are inaccessible and/or inflexible. As we have opined, the latter is important for an increasingly femaledominated profession. Flexibility not only applies to the opportunity for accelerated and interrupted and part-time learning, but also to recognition of prior learning, credit for conjoint training and broader community roles, development of common, across-disciplinary educational modules and facilitation of re-training and re-deployment. Affirmative and immersion programmes are needed throughout the education continuum. Affirmative schemes are the only way to diversify medical student populations sufficiently to create a cohort of practitioners that will address the health needs of indigenous and other minority populations. The professional colleges must ensure that students from such programmes progress seamlessly. Immersion programmes into regional and rural settings do result in increased local workforce capacities. The broader implications of the success of Australian rural medical schools must not be overlooked and it is time to apply the lessons learnt in Wagga Wagga to underresourced urban and metropolitan areas and to undersubscribed disciplines. The strategies and tactics so well used to advocate for rural general practitioners might work as well for urban psychiatrists. The role of the doctor in 2020 should be agreed before aligning health needs to resources and manipulating career choices to develop an effective health workforce. Doctor maldistributions will be easier to address when the roles of a professional, scientifically predicated, evidencebased cohort of health workers (i.e. doctors) are agreed and alternative fit-for-purpose health workers can be employed. An unpublished survey of junior doctors in an Auckland hospital showed that less than 15% of their employed time was spent doing things for which a medical education was necessary. There may already be enough doctors, at the least in the USA; the problem is that the

Matching the production of doctors with national needs

Matching the supply of health workers to need is necessary if a health system is to be sustainable, affordable and fit for purpose. On the 30th anniversary of the 1988 Edinburgh Declaration of the World Federation for Medical Education, levels of compliance with the 10th recommendation, ‘Ensure admission policies that match the numbers of students trained with national needs for doctors’, warrant review. There are two domains to such a review, concerning, respectively, how well these health needs are known, and whether workforce supply is well matched.

On the future role of the doctor.

We recently participated, along with our Minister of Health, in a debate on the future role of the doctor. This was well summarized by the Minister as showing strong support for health service reform and that there was a need for more doctors, but no one seemed sure of what or how many. Absolutely yes, Minister. Although such a doctor shortage in the USA could be challenged, it is inevitable that the American health system will continue to recruit large numbers of doctors from Australia and New Zealand (NZ). Our purpose here is to invite commentary on the future role of the doctor. This is a debate that is recognized internationally as being overdue and is arguably already too late given that the emergent specialist medical workforce of 2021 entered training this year. To paraphrase Jean-Paul Sartre, you cannot choose not to choose; that is, to do nothing is to select the status quo of medical education and service delivery. We have argued that based on regional and racial differences in health access and outcome, and mortality, alone, the status quo is unacceptable. Most predictions of the health needs arising within an older population in Australia and NZ are such that this unacceptability will probably be exaggerated. Some compression of morbidity in later life might be possible, as may be the short-term solutions of increasing the relative number of medical professionals, as is intended in Australia, and of increasing the workloads or productivity of individual health professionals. Nevertheless, our view is that to even maintain current health service levels, the health system will need to be differently configured and to work differently. This will require the use of innovative disruptions and the better alignment of health need and service. It is reasonable then to conclude that the status quo is an untenable response to questions concerning the future role of the doctor. We have argued recently in the Journal that time in training is a poor facsimile of competency determination and that direct measures are needed. The utility of such a time-independent approach has been shown by the Faculty of Occupational Medicine. The acknowledged preface to such a system is agreement on the intended role of the worker group and consequent essential competencies. In our experience, by contrast, most specialty curriculum writing addresses extant roles. This editorial then will present some generic doctor ‘attributes’ that we believe are likely to be agreed on and sufficiently robust to stand the test of time. These must be debated vigorously as they will determine learning outcomes and responsive curricula and pedagogies.

A narcotic dose of carbon monoxide induces neuronal haeme oxygenase and nitric oxide synthetase in sheep.

Twelve Romney ewes were exposed to either 1% carbon monoxide (CO) in air (n=6) or room air alone for 120 min and were killed 15 days later for histological and immunohistochemical examination. This dose of CO was narcotic and induced both haeme oxygenase and nitric oxide synthetase in brain neurons, but not in endothelial cells. The mechanism of the induction is not established here, but cellular theories of CO toxicity will need to be re-examined given these results.

Medical colleges: whose purpose, if any, do they serve?

The purpose, if any, that medical colleges could or do serve in 2017 is uncertain. The future college role might be constrained to professional and technical evaluation of doctor competence and up-skilling. The sentinel question is whether or not the medical guilds can become effective socially beyond intrinsic guild-need and play a role in preventing and mitigating, and in responding to, health system failures. Medical colleges have long been a part of the ‘health system architecture’. The Royal College of Surgeons (RCS) arose first as the Guild of Surgeons within the City of London in 1368. An agreement in 1493 resolved a consequential long-standing dispute between the surgeons and the barber-surgeons (from whose unqualified ranks the quaint habit of the titular Mr, and now similar feminine forms, arose instead of Dr). In 1540, Henry VIII formed the Company of Barber Surgeons as a union of the Worshipful Company of Barbers and the Guild of Surgeons. The surgeons broke away from the barbers to form the Company of Surgeons in 1745, and the RCS in London was created by way of a royal charter in 1800. The RCS in London is nevertheless well predated by the Barber Surgeons of Dublin, who were incorporated in 1446 by a royal decree from Henry VI, and just preceded in 1505 by the Barber Surgeons of Edinburgh, who were formerly incorporated as a Craft Guild of Edinburgh. In response to considerable lobbying from physicians and apothecaries, and sometime after similar regulatory interventions elsewhere in Europe, Henry VIII also formed the Royal College of Physicians by a royal charter in 1518, followed by an Act of parliament in 1523. There is no doubt about the craft-guild origins of the medical colleges and/or their longevity. The question to be debated is do the colleges still have any utility or are they anachronisms? To balance this historical introduction, it needs to be acknowledged that increasing patient safety by way of practitioner regulation was a strong element of the foundation debates. Critics of the medical profession, such as Roy Porter, argue that the sociological construct of the medical colleges has proven resilient and that they remain craft guilds. It is tautological then to argue that colleges are self-serving, as this is a central purpose and function of any guild. Both Porter, and other critics, such as Ivan Illich, would also suggest an alternative market-control (i.e. patch-protection and/or constraint-of-trade) rationale for practitioner regulation that is masked by patientsafety rhetoric. They would accept the various colleges’ public health affirming mottos but counter that craft guilds have always used community-service-type ‘platforms’ to advance their own causes, and in the case of health, sometimes at the expense of societal best interests. The history of medicine is littered with atrocities perpetuated by and/or tolerated by the medical profession, and by doctor-led health system failures; notwithstanding the considerable good for which the medical profession has been responsible, the unanswerable question in this context is why have the medical guilds repeatedly failed in their core and founding ‘patient-safety’ mission? Recent British examples of such systemic failures, which resulted in considerable patient-harm, such as in Bristol, and about a decade later in Mid-Staffordshire, suggest that little is learnt and that medical colleges are, at best, somewhat passive bystanders. Similarly, contemporary treatment injury data do not illustrate contextual college efficacy. Extrapolating from the most recent annual report of New Zealand’s comprehensive and no-fault Accident Compensation Corporation, treatment injury costs will soon exceed those of any other source of injury (i.e. either road traffic accidents, or industrial and domestic accidents). In the USA, medical error is now reported as the third most common cause of death, exceeded only by heart disease and cancer. The late Professor Sir John Scott and I argued that not only had the medical guilds ‘medicalised’ society, but also that medical practice had become consequentially socially distorted. We saw no real winners in the interaction. We also noted what we regarded as the classic definition of professionalism, which was made early in the 20th century by Justice Brandeis of the United States Supreme Court. He listed the peculiar characteristics of a profession as:

A lignocaine infusion worsens the leukoencephalopathy due to a carbon monoxide exposure in sheep.

Poisoning by carbon monoxide (CO) is common and conventional treatment of affected people is frequently unsuccessful. Lignocaine was identified as a potential therapy in this context because of the benefit shown for it in other brain injuries for which the received toxic mechanisms are similar. Twelve Romney ewes were exposed to 1% CO for 120 min were then infused intravenously with either lignocaine (N=6) or saline for 72 h, and were killed 5 days after the exposure for histological and immunohistochemical examination. This dose of CO was narcotic and caused white matter brain infarcts, with associated glial cell activation, axonal dysfunction and induction of both neuronal and glial haeme oxygenase and nitric oxide synthetase. The frequency of the white matter infarcts was significantly greater in the lignocaine-treated group. The mechanism of this adverse interaction is neither established here nor is it deducible from other published data; alternative antidotes to CO clearly need to be tested.