Casemix, management, and mortality of patients rreseceiving emergency neurosurgery for traumatic brain injury in the Global Neurotrauma Outcomes Study: a prospective observational cohort study

BACKGROUND

Traumatic brain injury (TBI) is increasingly recognised as being responsible for a substantial proportion of the global burden of disease. Neurosurgical interventions are an important aspect of care for patients with TBI, but there is little epidemiological data available on this patient population. We aimed to characterise differences in casemix, management, and mortality of patients receiving emergency neurosurgery for TBI across different levels of human development.

METHODS

We did a prospective observational cohort study of consecutive patients with TBI undergoing emergency neurosurgery, in a convenience sample of hospitals identified by open invitation, through international and regional scientific societies and meetings, individual contacts, and social media. Patients receiving emergency neurosurgery for TBI in each hospital's 30-day study period were all eligible for inclusion, with the exception of patients undergoing insertion of an intracranial pressure monitor only, ventriculostomy placement only, or a procedure for drainage of a chronic subdural haematoma. The primary outcome was mortality at 14 days postoperatively (or last point of observation if the patient was discharged before this time point). Countries were stratified according to their Human Development Index (HDI)-a composite of life expectancy, education, and income measures-into very high HDI, high HDI, medium HDI, and low HDI tiers. Mixed effects logistic regression was used to examine the effect of HDI on mortality while accounting for and quantifying between-hospital and between-country variation.

FINDINGS

Our study included 1635 records from 159 hospitals in 57 countries, collected between Nov 1, 2018, and Jan 31, 2020. 328 (20%) records were from countries in the very high HDI tier, 539 (33%) from countries in the high HDI tier, 614 (38%) from countries in the medium HDI tier, and 154 (9%) from countries in the low HDI tier. The median age was 35 years (IQR 24-51), with the oldest patients in the very high HDI tier (median 54 years, IQR 34-69) and the youngest in the low HDI tier (median 28 years, IQR 20-38). The most common procedures were elevation of a depressed skull fracture in the low HDI tier (69 [45%]), evacuation of a supratentorial extradural haematoma in the medium HDI tier (189 [31%]) and high HDI tier (173 [32%]), and evacuation of a supratentorial acute subdural haematoma in the very high HDI tier (155 [47%]). Median time from injury to surgery was 13 h (IQR 6-32). Overall mortality was 18% (299 of 1635). After adjustment for casemix, the odds of mortality were greater in the medium HDI tier (odds ratio [OR] 2·84, 95% CI 1·55-5·2) and high HDI tier (2·26, 1·23-4·15), but not the low HDI tier (1·66, 0·61-4·46), relative to the very high HDI tier. There was significant between-hospital variation in mortality (median OR 2·04, 95% CI 1·17-2·49).

INTERPRETATION

Patients receiving emergency neurosurgery for TBI differed considerably in their admission characteristics and management across human development settings. Level of human development was associated with mortality. Substantial opportunities to improve care globally were identified, including reducing delays to surgery. Between-hospital variation in mortality suggests changes at an institutional level could influence outcome and comparative effectiveness research could identify best practices.

FUNDING

National Institute for Health Research Global Health Research Group.

Anesthesia for meningioma surgery

Patients receiving treatment for a meningioma require anesthesia when undergoing open craniotomy and, in some cases, during preoperative tumor embolization and radiosurgery. Adequate anesthesia management is integral to patients' perioperative care, which consists of the three phases of preoperative assessment and optimization, intraoperative care, and postoperative recovery. The preoperative anesthesia evaluation focusses on the cardiorespiratory and neurologic systems, as well as the airway, but also extends to ensure the optimal treatment of significant comorbidities before surgical intervention. The goals of intraoperative care are maintenance of brain physiology, facilitating surgery, and correcting any adverse effects of surgery and underlying pathology to preserve general patient homeostasis. This requires adequate intraoperative patient monitoring, cardiorespiratory support, management of infusion therapy, and application of knowledge about the effects of anesthetic agents on brain physiology. The anesthesiologist's responsibilities for patient care extend well into the postoperative recovery period, with a focus on pain control, prevention, and treatment of postoperative nausea and vomiting (PONV), and, in some patients, intensive care therapy.

The Comparative Effects of Desflurane and Isoflurane on Lumbar Cerebrospinal Fluid Pressure in Patients Undergoing Craniotomy for Supratentorial Tumors

We compared the effects of desflurane and isoflurane on cerebral perfusion pressure (CPP), lumbar cerebrospinal fluid pressure (LCSFP), and mean arterial blood pressure (MAP) in patients anesthetized with desflurane or isoflurane undergoing craniotomy for supratentorial mass lesions. Additionally, emergence from anesthesia was examined to determine if neurologic function could be assessed earlier after isoflurane or desflurane anesthesia. Thirty-six patients were randomized to receive either desflurane or isoflurane for maintenance of anesthesia at 1.2 minimum alveolar concentration (MAC). Patients were hyperventilated (PaCO(2), 30 +/- 2 mm Hg) after baseline LCSFP was obtained via the subarachnoid catheter. At a MAC of 1.2, mean LCSFP was not statistically different between the two study groups either before or after hyperventilation. Additionally, CPP was not significantly different between the two groups. Finally, patient's time to respond to commands was 50% shorter in the desflurane group (30 +/- 36 min) (mean +/- SD) when compared with the isoflurane group (72 +/- 126 min); however, this was not significant (P = 0.17). In patients undergoing craniotomy for supratentorial mass lesions, desflurane and isoflurane have similar effects on CPP and MAP. Additionally, desflurane in the setting of hyperventilation does not cause significant changes in LCSFP.

IMPLICATIONS

This is the largest study to date comparing the effects of desflurane and isoflurane on patients undergoing craniotomy for supratentorial mass lesion with evidence of midline shift or edema. Neither desflurane nor isoflurane significantly altered lumbar cerebrospinal fluid pressure when moderate hypocapnia was maintained.

The long-term survival of baboon-to-monkey kidney and liver xenografts

The present study was undertaken to develop an optimum immunosuppressive regimen in baboon-to-monkey life-supporting kidney xenografts. Baseline therapy for all groups include cyclosporine (CsA) and steroids. We compared adding (1) cyclophosphamide (CyP) at dose of 20 mg/kg/day given on post-operative day (POD) 0, 2, 5 and 7; (2) mycophenolic mofetil (MMF) at a dose of 40 mg/kg/day by daily gavage; or (3) CyP + rapamycin (Rap). The latter group was divided into high and low dose subgroups. Untreated xenografts were rejected on POD 6, CsA alone treated xenografts survived for 35 days and CsA + CyP treated xenografts survived for 45 days. Adding MMF significantly prolonged mean survival to 111 +/- 53 days, but the xenografts eventually developed rejection. Combination therapy including CsA, CyP and Rap reliably prevented xenogenic rejection and achieved a mean survival of 290 +/- 30 days. However, high dose CyP + Rap led to high incidence of post-transplant lymphoproliferation disorders (PTLD), while the incidence of PTLD was significantly less in the low dose subgroup (P < 0.01). Four animals in this subgroup survived for more than 300 days with normal renal function and histology. In addition, two liver recipients treated with CsA + CyP survived for 91 and 1,076 days. We conclude that long-term survival of kidney or liver xenografts can be achieved in a non-human concordant xenograft model using currently available immunosuppressive agents.

The effect of hypothermia on the expression of the apoptosis-regulating protein Bax after incomplete cerebral ischemia and reperfusion in rats

This study investigated the effects of hypothermia on apoptosis-regulating proteins in a rat model of incomplete cerebral ischemia. Twenty-seven fasted male Sprague-Dawley rats (300-420 g) were anesthetized, intubated, and mechanically ventilated with 2.0% isoflurane and N(2)O/O(2) (FiO(2) = 0.33). Catheters were inserted and cerebral blood flow velocity was measured using bilateral laser Doppler flowmetry. At the end of preparation, the administration of isoflurane was replaced by fentanyl (25 microg. kg(-1). h(-1)). Animals were randomly assigned to one of the following groups: group 1 (n = 9, normothermia), normothermia (37.5 degrees C) during ischemia; group 2 (n = 9, hypothermia), 34 degrees C pericranial temperature during ischemia; and group 3 (n = 9, sham-operated animals), normothermia, no cerebral ischemia. Ischemia (30 minutes) was produced by unilateral common carotid artery occlusion plus hemorrhagic hypotension (mean arterial blood pressure 30-35 mm Hg). Arterial blood gas tensions and pH were maintained constant. Four hours after 30 minutes of incomplete cerebral ischemia, the brains were removed for determination of the expression of the apoptosis-regulating proteins Bax, Bcl-2, p53, and Mdm-2 using immunofluorescence and Western blot analysis. Four hours after cerebral ischemia there was a significant increase in the expression of the pro-apoptotic protein Bax in normothermic animals compared with hypothermic (85-260%) and sham-operated animals (60-190%). The proteins Bcl-2, p53, and Mdm-2 showed no statistically significant differences between the groups or between the hemispheres. In conclusion, hypothermia during ischemia decreased Bax protein expression that is associated with programed cell death. This suggests that neuroprotection seen with hypothermia may be related to a reduction of pro-apoptotic events.

The prehospital treatment of status epilepticus (PHTSE) study: design and methodology

Status epilepticus is a neurological emergency that is typically first encountered and managed in the prehospital environment. Although aggressive pharmacological treatment of status epilepticus is well established in the emergency department and hospital settings, the relative risks and benefits of active therapy for status epilepticus in the prehospital setting are not known. The Prehospital Treatment of Status Epilepticus (PHTSE) study is a prospective, randomized, double-blind, placebo-controlled study designed to address the following aims: (1) to determine whether administration of benzodiazepines by paramedics is an effective and safe means of treating status epilepticus in the prehospital setting and whether this therapy influences longer-term patient outcome, (2) to determine whether lorazepam is superior to diazepam for the treatment of status epilepticus in the prehospital setting, and (3) to determine whether control of status epilepticus prior to arrival to the emergency department influences patient disposition. The initial phase of the PHTSE study began in January 1994 and was completed in February 1999 after the successful enrollment of 205 patients into the three treatment arms. In this paper, we describe the rationale for the conceptualization of the study and details of the study design and methodology, and emphasize some aspects of study implementation that are unique to research involving the emergency medical system.

Lung volume reduction surgery for chronic obstructive pulmonary disease: where do we stand?

Lung volume reduction surgery (LVRS) is a promising new treatment for selected patients with moderate to severe symptoms of emphysema. Medical management, including pulmonary rehabilitation, has been shown to reduce oxygen requirements during exercise and probably to reduce hospitalization for patients with severe emphysema, but it does not improve pulmonary function. By improving the elastic recoil of the lung, LVRS is the first treatment to demonstrate substantial improvement in pulmonary function and quality of life for selected patients with emphysema. The most important selection factor for LVRS is the presence of a heterogeneous pattern of emphysema. Because it is found in only 20% of patients with emphysema, only a small number of patients are candidates for the procedure. Published reports indicate that the optimal operative technique appears to be a bilateral staple operation during a single anesthetic. This procedure offers a 68% chance of oxygen independence, 85% chance of prednisone independence, and 60% to 70% improvement in pulmonary function for patients with an upper lobe distribution of emphysema. The long-term benefits of the procedure are currently unknown, so several randomized, prospective studies are now comparing LVRS with maximal medical management.

The effects of clinical case management on hospital service use among ED frequent users

This study examined the impact of case management on hospital service use, hospital costs, homelessness, substance abuse, and psychosocial problems in frequent users of a public urban emergency department (ED). Subjects were 53 patients who used the ED five times or more in 12 months. Utilization, cost, and psychosocial variables were compared 12 months before and after the intervention. The median number of ED visits decreased from 15 to 9 (P < .01), median ED costs decreased from $4,124 to $2,195 (P < .01) and median medical inpatient costs decreased from $8,330 to $2,786 (P < .01). Homelessness decreased by -57% (P < .01), alcohol use by -22% (P = .05) and drug use by -26% (P = .05). Linkage to primary care increased 74% (P < .01). Fifty-four percent of medically indigent subjects obtained Medicaid (P < .01). There was a net cost savings, with each dollar invested in the program yielding a $1.44 reduction in hospital costs. Thus, case management appears to be a cost-effective means of decreasing acute hospital service use and psychosocial problems among frequent ED users.

Propofol prevents peroxide-induced inhibition of glutamate transport in cultured astrocytes

BACKGROUND

Glutamate transporters located in the plasma membrane of cerebral astrocytes take up excitatory neurotransmitters from the synaptic cleft. In diseases characterized by oxidative stress, the extracellular glutamate concentration increases and contributes to neuronal death. The authors wanted to determine whether propofol defends brain cells against oxidant-induced changes in their transport of glutamate.

METHODS

Primary cultures of rat cerebral astrocytes were exposed to tert-butyl hydroperoxide (1 mM) to serve as an in vitro model of oxidative stress. Astrocytes were incubated with propofol for 2 h and tert-butyl hydroperoxide was added for the final hour. Alternatively, astrocytes were incubated with tert-butyl hydroperoxide for 30 min and then with propofol for another 30 min. Control cells received drug vehicle rather than propofol. The rate of uptake of glutamate, the efflux of the nonmetabolizable analog D-aspartate, and the intracellular concentration of the endogenous antioxidant glutathione were measured.

RESULTS

Tert-butyl hydroperoxide decreased the glutathione concentration and inhibited glutamate uptake but had a negligible effect on D-aspartate efflux. At clinically relevant concentrations, propofol did not affect the glutathione concentration but did prevent the effect of tert-butyl hydroperoxide on glutamate transport. Furthermore, the addition of propofol after tert-butyl hydroperoxide reversed the inhibition of glutamate uptake.

CONCLUSIONS

Propofol prevents and reverses the inhibition of excitatory amino acid uptake in astrocytes exposed to tert-butyl hydroperoxide. The ability of propofol to defend against peroxide-induced inhibition of glutamate clearance may prevent the pathologic increase in extracellular glutamate at synapses, and thus delay or prevent the onset of excitotoxic neuronal death.

Pulmonary artery pressure: an intraoperative guide to limiting resection volume

Lung volume reduction surgery (LVRS) has shown promising results in severe emphysema. However, intraoperative indicators are needed to define optimal resection volumes. Diffusing capacity (DLCO) worsens with larger LVRS and may correlate with pulmonary artery (PA) pressure. We hypothesized that there would be a greater increase in PA pressures with larger volume LVRS in an inhaled elastase animal emphysema model. Twenty-one rabbits were induced with 15,000 units of elastase via an endotracheal tube. Four weeks later, bilateral LVRS was performed through a median sternotomy using an endoscopic stapler. PA pressures were measured prior to LVRS, immediately after LVRS, and at sacrifice. Single-breath DLCO, static pressure-volume relationships, and forced expiratory flows were measured prior to induction and at corresponding times to PA pressures. Systolic PA pressures increased in both groups immediately after LVRS (small: 2. 67 +/- 9.2 mm Hg, ANOVA, P = 0.023; large: 3.8 +/- 8.5 mm Hg, P = 0. 002), and then decreased at time of sacrifice 1 week later (small: 9. 43 +/- 4.8 mm Hg, ANOVA, P = 0.053; large: 5.2 +/- 7.3 mm Hg, P = 0. 552). The decrease, at sacrifice, in PA pressures was greater for small LVRS animals than large LVRS animals. The mortality rate (MR) for the small resection group was 0%, whereas that for the large resection group was 24%. The MR associated with larger LVRS was appreciably greater than that associated with small LVRS. These studies suggest that PA pressures may prove to be a useful intraoperative indicator for limits of resection.

Diffusing capacity limitations of the extent of lung volume reduction surgery in an animal model of emphysema

OBJECTIVE

The purpose of this study was to investigate in an elastase-induced emphysema rabbit model the effects of increasing resection volumes during lung volume reduction surgery on pulmonary compliance, forced expiratory air flow, and diffusing capacity to assess factors limiting optimal resection.

METHODS

Emphysema was induced in 68 New Zealand White rabbits with 15,000 units of aerosolized elastase. Static respiratory system compliance, forced expiratory flow, and single-breath diffusing capacity were measured before the induction of emphysema, after the induction of emphysema, and 1 week after a bilateral upper and middle lobe lung volume reduction operation.

RESULTS

Static respiratory system compliance with 60 mL insufflation above functional residual capacity increased with emphysema induction and then decreased progressively with resection of larger volumes of lung tissue (P =.001 by analysis of variance). Expiratory flow improved after lung resection in the rabbits with large resection volumes. In contrast, diffusing capacity tended to deteriorate with larger resection volumes (P =. 18).

CONCLUSION

Improvements in respiratory system compliance and forced expiratory flow after lung volume reduction operations may account for the improvements seen clinically. Declines in diffusing capacity with extensive lung reduction may limit the clinical benefits associated with greater tissue resection volumes. Future investigations with animal models may reveal other physiologic parameters that may further guide optimal lung volume reduction procedures.

Effect of lung volume reduction surgery on pulmonary diffusion capacity in a rabbit model of emphysema

BACKGROUND

While there is renewed interest in lung volume reduction surgery (LVRS) for treatment of emphysema, many aspects of the operation such as patient selection and surgical end points of excision are uncertain. We studied the effects of LVRS on measured lung volumes and diffusion capacity in an animal model to investigate optimal resection volumes.

METHODS

Emphysema was induced in 32 New Zealand white (NZW) rabbits using aerosolized elastase. Helium dilution lung volumes and single breath DLCO were measured concurrently at baseline, following induction of emphysema (preop), and 1 week postoperatively (postop) following LVRS. Bilateral upper and middle lobe stapled lung resections were performed through midline sternotomies with excision of variable amounts of lung tissue from 1.8 to 5.8 g.

RESULTS

FRC increased following induction of emphysema and decreased postoperatively. DLCO improved with increasing lung tissue resection up to 3 g of tissue and then decreased as even greater amounts were removed (r = 0.54).

CONCLUSIONS

Measured lung volumes increase with development of emphysema and appropriately decrease in response to LVRS in this rabbit model. DLCO improves with moderate resection but then decreases with excessive excision of lung quantities and may help define one physiologic operative end point. In this rabbit model, excision of approximately 30% of lung volume was optimal and prevented further decrease in diffusion capacity.

Insight on emphysema--the first 300 cases of surgical treatment

Our experience with lung volume reduction surgery for emphysema now encompasses more than 300 cases, including several prospective trials. We have a 3.5% operative mortality rate and, with aggressive use of Heimlich valves over the past 6 months, an average hospital length of stay of 8 days. Proper patient selection is essential and can be based primarily on results of pulmonary function tests (PFTs), ventilation/perfusion (V/Q) scans, and computed tomography (CT) scans. We have found that bilateral is more effective than unilateral staple lung volume reduction surgery, which is in turn better than unilateral laser surgery. In patients with bilateral upper lobe disease, average FEV1 (forced expiratory volume in a 1-second interval) improvement is 82%; overall, it is 61% (range -33 to 217%). We conclude that lung volume reduction surgery can be performed safely with acceptable mortality and excellent clinical results in properly selected, motivated patients.

Effect of lung volume reduction surgery in a rabbit model of bullous lung disease

Clinical use of staple lung volume reduction surgery (LVRS) has proliferated for treatment of emphysema despite limited data regarding efficacy or optimal techniques. Recent studies in animal models of obstructive lung disease describe the decrease in lung compliance and increase in airway support as mechanisms of an improvement in pulmonary functions analogous to human data. We describe contrasting results in an animal model of bullous lung disease with a mixed but predominantly restrictive pattern of lung disease. Mixed restrictive and bullous lung disease was induced in 17 New Zealand white rabbits with i.v. Sephadex beads and endotracheally instilled carrageenan. Unilateral stapled lung volume reduction surgery was performed at 5 weeks postinduction of emphysema on the right lower lobe by lateral thoracotomy using a pediatric stapler. Static trans-pleural pressures were measured at 60, 40, and 20 cm3 inflation at preinduction (baseline), pre- and postoperatively, and 1 week postoperatively in anesthetized animals. Lungs were then harvested en bloc and examined histopathologically. The effects of volume reduction surgery on static lung compliance, lung conductance, and forced expiratory flows (FEF) were assessed. Five weeks after induction of lung disease, the animals had no significant change in static compliance and forced expiratory volume in 0.5 s (FEV0.5) or lung conductance compared to baseline. Immediately following LVRS, the animals showed a significant decrease in static compliance, FEV0.5, and conductance. One week postoperatively, compliance increased to approximately baseline levels along with a slight increase in FEFs and conductance toward preoperative levels. Histology examination revealed restrictive and bullous lung disease. Thus, we have demonstrated the feasibility of using an animal model for evaluation of volume reduction therapy for restrictive-obstructive lung disease. Physiologically, this model showed decrease conductance and decreased forced expiratory flows following lung volume reduction despite increased recoil. This is in contrast to increased conductance and flows seen in humans with severe emphysema following surgery and suggests that current criteria excluding patients with a significant restrictive component to their lung disease from LVRS surgery may be justified.

An animal model for lung volume reduction therapy of pulmonary emphysema

Stapled lung volume reduction surgery (LVRS) has recently been described for treatment of emphysema. Many questions arise regarding physiologic mechanisms of response from surgical treatment of emphysema. The objective of this study was to develop an animal model for the study of lung volume reduction surgery in diffuse heterogeneous emphysema. We hypothesized that elastic recoil would increase, static respiratory system compliance would decrease, and expiratory flows would increase after lung volume reduction surgery in animals with emphysema. In the study, emphysema was induced in 31 New Zealand White rabbits (3-5 kg) with endotracheally aerosalized porcine elastase (10,000-12,000 U). Lateral thoracotomies were performed 4-6 weeks postinduction under general anesthesia and mechanical ventilatory support. Stapled volume reduction was performed on the right lower lobe using a standard multirow pediatric stapler (U.S. Surgical). Pulmonary function tests were performed at baseline (preinduction), before stapling LVRS (postemphysema induction), immediately post stapling LVRS, and 1 week poststapling. Static respiratory system compliance, flow, conductance and forced expiratory flows, and peak flows at 20 and 40 cm3 of exhaled volume were analyzed. Animals were sacrificed 1 week poststapling, and bilateral lungs were harvested for histopathology. Diffuse but heterogeneous pulmonary emphysema was seen in these animals treated with high-dose aerosolized elastase. Static compliance increased, while expiratory flows and conductance decreased after induction of emphysema. Immediately post stapled volume reduction therapy, animals had decreased static compliance. By 1 week following surgery, animals showed increased forced expiratory flows and decreased expiratory resistance, although compliance was similar to preoperative levels. In conclusion, we describe initial results in an animal model of obstructive emphysema suitable for the study of lung volume reduction surgery. Changes in pulmonary function indicate that unilateral lower lobe LVRS increases airway conductance in the rabbits. Findings from LVRS studies in animal models such as this may help explain clinical improvement following LVRS in humans.

Changes in pulmonary physiology after lung volume reduction surgery in a rabbit model of emphysema

OBJECTIVE

The purpose of this study is to investigate the effects of lung volume reduction surgery on pulmonary compliance, airway flow, and helium lung volumes in an elastase-induced emphysema animal model.

METHODS

A 15,000-unit bolus of elastase was aerosolized through an endotracheal tube in 14 New Zealand White rabbits to induce emphysema. Stapled lung volume reduction of bilateral upper and middle lobes was performed through a midline sternotomy at 4 weeks after induction of emphysema. Lung functions were measured at baseline before induction of emphysema, preoperatively at 4 weeks, and 1 week postoperatively.

RESULTS

Compliance increased after induction of emphysema and decreased in response to lung volume reduction surgery. Functional residual capacity decreased after lung volume reduction surgery in proportion to the amount of excised lung tissue. Expired flows suggested improvement in response to lung volume reduction surgery. Histologic examination confirmed presence of diffuse heterogeneous emphysema in each animal at necropsy.

CONCLUSIONS

The decreased compliance and increased airway flow after volume reduction surgery in this model parallels findings in human studies and suggests that similar mechanisms of increased elastic recoil and airway support contribute to improvement.

Magnesium deficiency increases ketamine sensitivity in rats

PURPOSE

Inhibition of the NMDA receptor likely contributes to ketamine's neurodepressive properties. Magnesium also inhibits the NMDA receptor by binding to a site associated with the ketamine-binding domain. Electrophysiological studies suggest that magnesium prevents ketamine from binding to the NMDA receptor and thereby prevents ketamine inhibition. We undertook an in vivo study to determine if magnesium deficiency was associated with an increased sensitivity to ketamine.

METHODS

Weanling rats were maintained on a Mg(2+)-deficient or control diet for 14 days. In Study I, rats were anaesthetized then sacrificed and the Mg2+ concentrations in the brain and plasma were measured. In a second prospective study, experimental animals were rendered hypomagnesaemic and the potency of 125 mg.kg-1 ip ketamine was evaluated. Animals were then were fed a Mg(2+)-containing diet and ketamine sensitivity was re-examined 14 days later.

RESULTS

The Mg(2+)-deficient diets rendered the rats hypomagnesaemic as indicated by the brain and plasma concentration of Mg2+. In Study 2, the time to loss of righting reflex was shorter; 1.9 +/- 0.3 min (n = 12) and 2.6 +/- 0.2 min (n = 16, P < 0.05), whereas the latency to toe pinch was prolonged: 25.0 +/- 5.8 min (n = 12) vs 3.1 +/- 2.1 min (n = 16, P < 0.05) in the Mg(2+)-deficient compared with age-matched control animals, respectively. The hypomagnesaemic animals had a higher death rate following ketamine injection. The increased sensitivity to ketamine was no longer apparent when the animals were re-tested following replenishment of Mg2+.

CONCLUSION

Hypomagnesaemia is associated with an increased sensitivity to ketamine.

Objective predictors of response for staple versus laser emphysematous lung reduction

Recently described surgical approaches to the treatment of emphysema, including buttressed stapled volume reduction and laser coagulation, are associated with variable clinical outcomes. We examined objective preoperative factors as predictors of response to treatment in patients enrolled in a randomized trial of staple versus laser volume-reduction surgery in order to help define patient selection criteria for these procedures. Seventy-two patients with severe symptomatic emphysema without bullae were entered into the protocol (39 staple, 33 laser). Preoperative objective variables (pulmonary function tests, smoking history, demographics, and graded chest computed tomographic [CT] scans) were evaluated as predictors of response to treatment (defined as a change in FEV1) at 3- to 6-mo follow-up, using linear and multivariate regression analysis. Follow-up pulmonary function was obtained on 90% of the 68 patients surviving at 6 mo. Overall improvement was significant only for staple-treated patients, and improved outcome correlated with greater smoking history and younger age for staple-treated patients. When physiologic variables were analyzed, greater smoking history, lower DL(CO), and younger age predicted improved outcome for laser-treated patients. Preoperative FEV1 and gas-exchange variables did not predict outcome in staple-treated patients. When CT scan grading was included in multivariate regression analysis, hyperinflation (increased thoracic gas volume) was the primary predictor of response for laser-treated patients. These findings suggest that younger patients with evidence of advanced emphysematous lung disease and hyperinflation are optimal candidates for lung-volume-reduction surgery, particularly by staple-reduction techniques. Additional studies with long-term follow-up, bilateral procedures, and assessment of other outcome measures must be performed to further define operative criteria for lung-volume-reduction surgery for emphysema.

Predictors of carbon monoxide and hydrogen cyanide exposure in smoke inhalation patients

OBJECTIVE

A prospective study of civilian (nonfirefighter) smoke inhalation patients was carried out to test the hypotheses that: 1) absorption of carbon monoxide and hydrogen cyanide from smoke can be predicted by clinical examination and historical data; and, more specifically 2) a history of exposure to burning synthetic polymers is an important predictor of systemic cyanide levels.

METHODS

The study was conducted over a three-year period at six urban hospitals. Patients with or without burns who were exposed to smoke within five hours of hospital arrival were sampled for carboxyhemoglobin, whole blood cyanide, urine cotinine and urine creatinine. Controls consisted of a smaller group of smoking status-matched, nonsmoke-exposed burn patients.

ANALYSIS

Historical information was obtained on SMOKING status, FIRETYPE (structural vs other), MATERIAL burned (natural vs synthetic) and LAGTIME (from exposure to sampling). A smoke inhalation SCORE (0-10) was assigned to each case, based on physical examination findings and changes on chest X ray, and carboxyhemoglobin and cyanide levels were entered into various multivariate linear regression models.

RESULTS

A total of 40 cases and 9 controls were recruited, ranging in age from 15 to 92 years. Thirty-four cases were discharged alive and six expired in-hospital. Observed carboxyhemoglobin levels ranged from 1.2% to 41.6% in cases (mean 8.6%), and from 0.5 to 7.3% in controls (mean 2.9%). Observed cyanide levels ranged from nondetectable (< 0.05 micrograms/mL) to 2.79 micrograms/mL in cases (mean 0.25 micrograms/mL), and from nondetectable to 0.11 micrograms/mL in controls (mean 0.03 micrograms/mL). Among cases, linear regression models explained up to 35% of the observed variance in carboxyhemoglobin levels (p < 0.001) and up to 48% of the variance in cyanide levels (p = 0.0001).

CONCLUSIONS

SCORE was the strongest predictor of both carboxyhemoglobin and cyanide levels; LAGTIME also explained significant variance for [log-transformed] carboxyhemoglobin. Historical factors, such as FIRETYPE, MATERIAL, and SMOKING status, did not explain significant variance in most of the statistical models employed.

Infrared emission from reactions of high-velocity atomic oxygen with black surfaces: Z306 paint, anodized aluminum, and Teflon

Large optical telescopes are being placed into orbit at altitudes where the residual atmosphere can interact with the spacecraft to produce optical emissions, such as the visible shuttle glow. The near-field emissions produced from these interactions will reduce the far-field detection limits of these instruments. Here we present laboratory data on the intensities and spectral distributions of the infrared emissions created in the interaction at orbital velocity of the dominant atmospheric constituent, atomic oxygen, with optical baffle coating materials used on space observatory platforms: Z306 Chemglaze paint, black anodized aluminum, and black Teflon. Data over the 1.0-5.4-µm spectral region are presented. Adsorbed contaminants dominate the spectra of the less reactive coatings. We present data on contaminant removal with oxygen fluence. We also include a simple assessment, based on these data, of the magnitude of this interaction and its effect on mission performance.

Crohn's ileitis in a patient with longstanding HIV infection

The differential diagnosis of diarrhea in patients infected with HIV is broad, and includes a variety of bacterial, viral, and parasitic pathogens, as well as malignancies including lymphoma and Kaposi's sarcoma. Idiopathic non-specific inflammatory bowel disease rarely occurs in association with HIV infection. A recent case report described a patient with longstanding Crohn's disease who experienced remission of his bowel disease upon infection with HIV (6). The authors inferred that the remission was secondary to a depressed CD4 (T helper) lymphocyte count. We report the first case of Crohn's ileitis developing in a patient with established HIV infection, depressed CD4 lymphocyte count, and no prior history of inflammatory bowel disease. This case raises questions about the role of CD4 cells in the pathogenesis of Crohn's disease.

Langerhans' cell histiocytosis presenting with the superior vena cava syndrome: a case report

A case of Langerhans' cell histiocytosis confined to the mediastinum and presenting with de novo superior cava syndrome is reported. The causes of superior vena cava syndrome in childhood are discussed as is the importance of obtaining pathologic diagnosis prior to initiating therapy.

Cardiovascular effects of human insular cortex stimulation

Recent investigations indicate a site of cardiac representation within the left insular cortex of the rat. Moreover, the results of lesion studies suggest left-sided insular dominance for sympathetic cardiovascular effects. It is unclear whether similar representation exists within the human insular cortex. Five epileptic patients underwent intraoperative insular stimulation prior to temporal lobectomy for seizure control. On stimulation of the left insular cortex, bradycardia and depressor responses were more frequently produced than tachycardia and pressor effects (p less than 0.005). The converse applied for the right insular cortex. We believe this to be the first demonstration of cardiovascular changes elicitable during insular stimulation in humans, and of lateralization of such responses for a cortical site. In humans, unlike the rat, there appears to be right-sided dominance for sympathetic effects. These findings may be of relevance in predicting the autonomic effects of stroke in humans and in the explanation of sudden unexpected epileptic death.

Isoflurane for refractory status epilepticus: a clinical series

General anesthesia has been recommended to control convulsive status epilepticus that is refractory to conventional anticonvulsant therapy. Halothane has been the recommended agent, but without experimental justification. Isoflurane, which has no reported organ toxicity and produces electrographic suppression at clinically useful concentrations in normal humans, should be a better volatile anesthetic for this purpose. The efficacy and safety of isoflurane administered to control convulsive status epilepticus were assessed on 11 occasions in nine patients in seven North American hospitals. Isoflurane, administered for 1-55 h, stopped seizures in all patients and was able to be titrated to produce burst-suppression patterns on electroencephalograms. Blood pressure support with iv fluids and/or pressor infusions was required in all of the patients. Seizures resumed upon discontinuation of isoflurane on eight of 11 occasions. Six of the nine patients died. The three survivors sustained cognitive deficits. In one patient urine fluoride concentrations were elevated, although not to nephrotoxic levels. These cases suggest that isoflurane 1) is an effective, rapidly titratable anticonvulsant; 2) does not reverse underlying causes of the refractory seizures; and 3) usually necessitates hemodynamic support with fluids and/or pressors. Isoflurane may be administered for seizures, but only when iv agents in anesthetic doses are ineffective or produce unacceptable side effects.

Angiostrongyliasis: a rare cause of gastrointestinal hemorrhage

Angiostrongylus costaricensis is an intestinal nematode, endemic to Central and South America. Affecting mostly children, it causes an eosinophilic gastroenteritis with involvement of the appendix, distal small bowel, and right colon. We report a case of a 41-yr-old man, from a non-endemic area, with the unique presentation of recurrent gastrointestinal bleeding. The diagnosis was made after surgical exploration.

Patient anesthesia and monitoring at a 1.5-T MRI installation

This paper describes the facilities successfully used to provide patient monitoring and anesthesia support in a 1.5-T imaging installation. The requirements for the MRI site for anesthetic gases, shielded power, and radiofrequency ports are outlined. Specific modifications in anesthesia machines, anesthesia cart, laryngoscope, mercury sphygmomanometer, oximeter, and remote blood pressure devices are described. Additional aspects of patient monitoring and support, e.g., electrocardiogram and pressure infusion, are also discussed.

Aminophylline increases the toxicity but not the efficacy of an inhaled beta-adrenergic agonist in the treatment of acute exacerbations of asthma

We studied 40 patients with acute exacerbations of asthma to determine the efficacy of a 3-h intravenous infusion of aminophylline in patients who were already being treated with an inhaled beta-adrenergic agonist (metaproterenol). Each patient was treated with inhaled metaproterenol at hourly intervals for 3 h. In addition, patients were randomly assigned to therapy with either intravenous aminophylline or placebo. Neither the patient nor the house officers and nurses caring for the patient knew whether aminophylline or placebo was given. The FEV1 improved continually throughout the study to a similar extent in both treatment groups, but the patients treated with aminophylline had significantly more adverse effects (p less than 0.025, Mann-Whitney). There was no apparent benefit from aminophylline even in patients who presented to the emergency room with severe airway obstruction (FEV1 less than 0.8L) or with plasma theophylline levels less than 10 mg/L. We conclude that intravenous aminophylline adds to the toxicity but not the efficacy of inhaled metaproterenol in the treatment of acute exacerbations of asthma.

Isospora belli in a patient with acquired immunodeficiency syndrome

Isospora belli is a cause of protracted diarrhea in immunocompromised patients. Acquired immunodeficiency syndrome (AIDS), seen mostly in homosexual men and narcotic addicts, predisposes affected persons to a number of opportunistic infections. As Isospora belli has been reported only once in this group, we report Isospora belli in an AIDS patient with chronic diarrhea.