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W L Lanier

Publications and source records attributed to W L Lanier.

At least 19 recordsLinked to original sources
PubMed2001

Postnatal growth retardation exacerbates acidosis-induced retinopathy in the neonatal rat.

PURPOSE: We have previously described a metabolic acidosis-induced retinopathy in the neonatal rat, similar to retinopathy of prematurity (ROP). We also have reported exacerbation of oxygen-induced retinopathy by postnatal growth retardation, produced by raising newborn rats in 'expanded' litters. In the present study, we investigated the effect of postnatal growth retardation on the incidence and severity of acidosis-induced retinopathy. METHODS: 100 newborn Sprague-Dawley rats were randomly assigned to two expanded litters of 25 pups each and five standard control litters of 10 pups each. All rats were gavaged with 10 mM/kg NH(4)Cl twice daily from days two to seven. Following five days of recovery, retinal vasculature was assessed using ADPase staining, light microscopy, and computer-assisted image analysis. The presence of neovascularization (NV), severity of NV (clock hours), and vascularized retinal areas, were evaluated in a masked manner. RESULTS: NV occurred in 52% of rats in expanded litters versus 18% of rats in standard control litters (p = 0.005). Postnatal growth retardation of pups in expanded litters was confirmed by comparing total body weight of pups raised in expanded and standard control litters (10.8g vs 13.4g on day 8, p < 0.001; 20.8g vs 25.2g on day 13, p = 0.002). CONCLUSIONS: Postnatal growth retardation increases the incidence of acidosis-induced retinopathy in the neonatal rat. Our study provides further evidence that postnatal growth retardation is a risk factor for preretinal neovascularization in immature retinae and is consistent with the clinical observation that the smallest and sickest premature infants are more likely to suffer from ROP.

Acidosis↗
PubMed2001

Preretinal neovascularization associated with acetazolamide-induced systemic acidosis in the neonatal rat.

PURPOSE: NH4Cl gavage in the neonatal rat produces a metabolic acidosis-induced retinopathy which serves as a model for retinopathy of prematurity (ROP). Acetazolamide induces a metabolic acidosis via an alternative biochemical mechanism (bicarbonate loss versus hydrogen ion load). In the present study, the following hypothesis was tested: acetazolamide-induced acidosis is associated with preretinal neovascularization in the neonatal rat. METHODS: All studies used newborn Sprague-Dawley rats raised in expanded litters of 25. Arterial blood pH was measured to determine the level of acidosis induced by intraperitoneal (IP) acetazolamide (50 or 200 mg/kg) or saline. In a separate retinopathy study, newborn rats (n = 75) were randomized to either IP acetazolamide, 50 mg/kg (low-dose), or IP saline twice daily from days 2 to 7. After 5 days of recovery, retinal vasculature was assessed using ADPase staining and light microscopy. The presence and severity (clock hours) of neovascularization were assessed by three masked observers. In an additional retinopathy study, newborn rats (n = 100) were randomized to either IP acetazolamide, 200 mg/kg (high-dose), or IP saline twice daily from days 2 to 7. After 5 days of recovery, the retinas were similarly analyzed. RESULTS: Neovascularization occurred in 59% of rats receiving high-dose acetazolamide (200 mg/kg). High-dose acetazolamide produced a severe acidosis (pH 7.13 +/- 0.06) during drug delivery. Low-dose acetazolamide (50 mg/kg) produced a pH (7.22 +/- 0.07) that was intermediate between high-dose (200 mg/kg) acetazolamide (P < 0.001) and saline controls (7.42 +/- 0.06, P < 0.001); however, neither low-dose acetazolamide nor saline induced preretinal neovascularization. CONCLUSIONS: Acidosis induced by high-dose acetazolamide, independent of hyperoxemia or hypoxemia, is associated with preretinal neovascularization in the neonatal rat. Induction of neovascularization appears to depend on a critical threshold of acidosis severity. This study further supports a proposed independent role for acidosis in the pathogenesis of ROP.

Acetazolamide↗
PubMed2000

The effect of chronic dexamethasone-induced hyperglycemia and its acute treatment with insulin on brain glucose and glycogen concentrations in rats.

BACKGROUND: In the rat model of forebrain ischemia, long-term dexamethasone treatment is reported to cause hyperglycemia and worsen postischemic functional and histologic injury. This effect was assumed to result from glucose enhancement of intraischemic lactic acidosis within the brain. Short-term insulin therapy restored normoglycemia but did not return histologic injury completely to baseline values. Using a nonischemic rat model, the current study attempted to identify a metabolic basis for such outcome data. METHODS: Fifty-eight halothane-anesthetized (1.3% inspired) Sprague-Dawley rats were assigned randomly to be administered either no treatment (N = 18) or 2 mg/kg intraperitoneal dexamethasone (N = 40). The latter were administered dexamethasone 3 h before the study only (N = 8) or for 3 h before the study plus daily for 1 day (N = 8), 2 days (N = 8), or 4 days (N = 16). Of the rats treated with dexamethasone for 4 days, one half (N = 8) were administered an insulin-containing saline infusion subsequently to restore normoglycemia short-term. All other rats (N = 50) were administered an infusion of saline without insulin. Plasma glucose was quantified, and brains were excised after in situ freezing. Brain glucose and glycogen concentrations were measured using enzymatic fluorometric analyses. RESULTS: After 4 days of dexamethasone treatment, plasma glucose was 159% greater than in rats administered placebo (i.e., 22.01 +/- 4.66 vs. 8.51 +/- 1.65 micromol/ml; mean +/- SD; P < 0.0001). Brain glucose concentrations increased parallel to plasma glucose. An insulin infusion for 27 +/- 5 min restored normoglycemia but resulted in a brain-to-plasma glucose ratio that was 32% greater than baseline values (P < 0.01). Neither dexamethasone nor the combination of dexamethasone plus insulin affected brain glycogen concentrations. CONCLUSIONS: In a nonischemic rat model, dexamethasone alone had no independent effect on the brain-to-plasma glucose ratio. However, short-term insulin therapy caused a dysequilibrium between plasma and brain glucose, resulting in an underestimation of brain glucose concentrations when normoglycemia was restored. The dysequilibrium likely was caused by the rapid rate of glucose reduction. The magnitude of the effect may account for the failure of insulin to reverse dexamethasone enhancement of neurologic injury completely in a previous report that used the rat model of forebrain ischemia.

Animals↗
PubMed2000

Anesthetic management for two-stage computer-assisted, stereotactic thalamotomy in a child with Hallervorden-Spatz Disease.

We report the numerous management challenges surrounding the care of a child in whom bilateral thalamotomies were used to treat end-stage Hallervorden-Spatz Disease (HSD). The management of this patient was greatly facilitated by the use of modern anesthetic agents and a multidisciplinary team to care for the patient. The outcome was an improved life expectancy and quality of life.

Anesthesia↗
PubMed2000

Exaggerated hemodynamic responses to nasal injection and awakening from anesthesia in a Cushingoid patient having transsphenoidal hypophysectomy.

A 51-year-old female patient, with an adrenocorticotrophic hormone-secreting pituitary tumor, was scheduled for transphenoidal hypophysectomy. She had a history of recent onset diabetes mellitus and a 2-year history of arterial hypertension. Despite ongoing medical therapy, preoperative blood pressure was 150-160/90-120 mm Hg. During general anesthesia, in response to perinasal infiltration with 10 ml of a solution containing lidocaine 200 mg and epinephrine 100 microg, blood pressure increased from 144/80 mm Hg to 317/175 over 3 minutes, as assessed by direct blood pressure monitoring. At the completion of the anesthetic, as the patient awakened and coughed and moved, blood pressure again increased dramatically, this time from 154/87 mm Hg to 285/170 over 3 minutes. Five months postoperatively, the patient's serum cortisol concentrations had normalized and her cuff blood pressure was 126/82, despite a reduction in her antihypertensive medications. The dramatic intraoperative blood pressure changes in this patient were attributed to the effects of hypercortisolemia on the normal physiologic responses to epinephrine and patient movement.

Administration, Intranasal↗
PubMed1999

The prevention and treatment of cerebral ischemia.

Although the major focus of recent cerebral protection research has been aimed at developing receptor-specific drugs, this effort has currently resulted in few improvements in patient outcome. Until advances in pharmacology translate to improvements in humans, the clinician and his patients will be well served by using more traditional techniques to prevent and treat cerebral ischemic events. This approach will involve interventions to a) identify patients who are experiencing or are at risk for developing cerebral ischemia, and b) alter systemic physiology in an attempt to lessen the duration and severity of any ischemic insults. Initial therapy should include interventions to improve cerebral perfusion and the oxygen carrying capacity of the blood. Once this is accomplished, measures should be taken to control blood glucose concentrations and treat fever. In otherwise stable surgical patients, mild reductions in patient temperature also may be of benefit, provided the temperature reductions do not introduce problems in systemic physiology and the patient is rewarmed prior to awakening from general anesthesia. General anesthetic choice may be of importance in controlling intracranial pressure and seizure activity; however, if direct cerebral protection is desired, the anesthetic of choice should be a barbiturate. Finally, in the patient at risk for cerebral vasospasm, nimodipine treatment should be considered. Collectively, these interventions should increase the patient's chance for optimal neurologic recovery following ischemia.

Anesthesia↗
PubMed1999

Pulmonary edema after resection of a fourth ventricle tumor: possible evidence for a medulla-mediated mechanism.

A well-recognized fact is that some patients may have development of pulmonary edema in association with disorders of the central nervous system. The origin of this phenomenon, known as neurogenic pulmonary edema, is unclear but may result, in part, from select pulmonary venoconstriction modulated by autonomic outflow from the medulla oblongata. We describe a 21-year-old man who had development of pulmonary edema in association with surgical resection of a brain tumor that was close to the medulla. Other than the possibility of medullary dysfunction, which could have occurred after surgical manipulation, no other risk factor for pulmonary edema was identified. Of note, the patient's blood pressure remained normal throughout the perioperative period, and no fluid overload or primary cardiac dysfunction was evident. This case supports the theory that the medulla is an important anatomic site of origin for neurogenic pulmonary edema and that alterations in medullary function can induce pulmonary edema in humans, independent of systemic hypertension.

Adult↗
PubMed1999

Acute pulmonary edema associated with placement of waist-high, custom-fit compression stockings.

Compression stockings are a safe, noninvasive treatment for patients with symptomatic orthostatic hypotension due to autonomic nervous system dysfunction. In this report, we describe a 75-year-old man who had development of pulmonary edema approximately 45 minutes after placement of compression stockings on the first postoperative day following a carotid endarterectomy. No sudden changes were noted on an electrocardiogram or echocardiogram or in the cardiac isoenzymes associated with the pulmonary edema. The patient had a history of coronary artery disease, diabetes mellitus-induced autonomic nervous system dysfunction, and recent surgery near the carotid baroreceptor. All these factors may have limited his ability to compensate for a rapid increase in central blood volume. The temporal relationship of the patient's respiratory distress to the placement of the compression stockings, in the absence of laboratory findings of primary cardiac dysfunction, make stocking-related fluid shift the likely precipitating event in the formation of acute pulmonary edema. This case suggests that compression stockings should be used with caution in patients with limited cardiac reserve.

Acute Disease↗
PubMed1999

Metabolic acidosis-induced retinopathy in the neonatal rat.

PURPOSE: Carbon dioxide (CO2)-induced retinopathy (CDIR) in the neonatal rat, analogous to human retinopathy of prematurity (ROP), was previously described by our group. In this model, it is possible that CO2-associated acidosis provides a biochemical mechanism for CDIR. Therefore, the effect of pure metabolic acidosis on the developing retinal vasculature of the neonatal rat was investigated. METHODS: A preliminary study of arterial blood pH was performed to confirm acidosis in our model. In neonatal rats with preplaced left carotid artery catheters, acute blood gas samples were taken 1 to 24 hours after gavage with either NH4Cl 1 millimole/100 g body weight or saline. In the subsequent formal retinopathy study, 150 newborn Sprague-Dawley rats were raised in litters of 25 and randomly assigned to be gavaged twice daily with either NH4Cl 1 millimole/100 g body weight (n = 75) or saline (n = 75) from day 2 to day 7. After 5 days of recovery, rats were killed, and retinal vasculature was assessed using fluorescein perfusion and ADPase staining techniques. RESULTS: In the preliminary pH study, the minimum pH after NH4Cl gavage was 7.10+/-0.10 at 3 hours (versus 7.37+/-0.03 in controls, mean +/- SD, P < 0.01). In the formal retinopathy study, preretinal neovascularization occurred in 36% of acidotic rats versus 5% of controls (P < 0.001). Acidotic rats showed growth retardation (final weight 16.5+/-3.0 g versus 20.2+/-2.6 g, P < 0.001). The ratio of vascularized to total retinal area was smaller in acidotic rats (94%+/-4% versus 96%+/-2%, P < 0.001). CONCLUSIONS: Metabolic acidosis alone induces neovascularization similar to ROP in the neonatal rat. This suggests a possible biochemical mechanism by which high levels of CO2 induce neovascularization and supports the suggestion that acidosis may be an independent risk factor for ROP.

Acidosis↗