A pilot study in intraparenchymal therapy delivery in the prostate: a comparison of delivery with a porous needle vs standard needle

BACKGROUND

New biologic therapies directly injected into the prostate are in clinical trials for prostatic diseases. There is a need to understand distribution of injected therapies as a function of prostatic anatomy, physiology, and device design.

METHODS

A needle with a porous length of customizable-length was tested and its performance compared with a standard needle. Injections of magnetic resonance contrast reagent were placed into ex-vivo human prostates after surgical excision in standard of care therapy for invasive bladder cancer patients. Magnetic resonance images were acquired using sequences to quantify volume delivered, distributed, and backflow.

RESULTS

Magnetic resonance images analysis revealed heterogeneity distribution with injection into the specimens. There was low resistance to flow along ductal pathways and high resistance to flow into glandular nodules and smooth muscle/fibrous parenchyma. Data confirm previous studies showing injection loss via urethra backflow, urethra, and prostatic ducts. Tissue fraction of dose was significantly higher with porous needle compared with standard needle (p = .03). We found that a greater volume of distribution divided by the amount infused (Vd/Vi) increased by 80% with the porous needle, though no statistically significant association due to small sample size.

CONCLUSIONS

This study demonstrated that prostatic tissue is anatomically heterogenic and limits distribution of needle injection. There is greater distribution in the ex-vivo prostate using a porous needle. The complexity of intra prostatic flow pathways suggests preoperative imaging and pre-treatment planning will enhance therapy.

Large-Volume Infusions into the Brain: A Comparative Study of Catheter Designs

BACKGROUND/AIMS

"Whole-brain" infusions have emerged as a potential need with the promise of disease-modifying therapies for neurodegenerative diseases. In addition, several current clinical trials in brain cancer utilize direct delivery of drugs that are required to fill large volumes. Such requirements may not be well served by conventional single port catheters with their "point source" of delivery. Our aim is to examine infusions into large volumes of heterogeneous tissue, aiming for uniformity of distribution.

METHODS

A porous catheter (porous brain infusion catheter, PBIC), designed by Twin Star TDS LLC, for brain infusions was developed for this study and compared with another convection-enhanced delivery catheter (SmartFlowTM NGS-NC-03 from MRI Interventions, a step end-port catheter, SEPC) in current use in clinical trials. The studies were in vivo in porcine brain. A total of 8 pigs were used: the size of the pig brain limited the porous length to 15 mm. The placements of the tips of the two catheters were chosen to be the same (at the respective brain hemispheres).

RESULTS

The PBIC and SEPC both performed comparably and well, with the PBIC having some advantage in effecting larger distributions: p ∼ 0.045, with 5 infusions from each.

CONCLUSIONS

Given the performance of the PBIC, it would be highly appropriate to use the device for therapeutic infusions in human clinical trials to assess its capability for large-volume infusions.

Theory of porous catheters and their applications in intraparenchymal infusions

Multiport catheters and catheters with a porous surface have been proposed for intraparenchymal infusions of therapeutics in fluid suspensions. Target diseases include brain cancer and serious neurodegenerative diseases, as well as peripheral tumors, for example in the prostate and the liver. We set up the theory for infusions from such devices, in particular the fluid flow equations which demand a coupling between the flow within the catheter and that in tissue. (Such a coupling is not necessary in the theory of infusion from single port catheters.) The new feature of such catheters, treated by our model, is revealed by infusions into inhomogeneous media. Multiport designs have the potential to overcome the limitation of single port catheters, for which the path of the fluid leaving the port is dominated by the inhomogeneities. We solve these equations for some simple cases to illustrate the key design features of porous catheters that show such advantages. The mathematics required for numerical solution with more realistic assumptions is also developed. We confirm the robustness of such catheters, when the ports are sufficiently resistive, against leakage paths that would compromise the infusions from catheters with one or a few large ports. The methods of this paper can be incorporated into a larger planning system for intraparenchymal infusions involving such devices.

Effect of Tissue Ultrafiltration on Skin Flap Survival

OBJECTIVE: Tissue ultrafiltration (TUF) is a method of reducing tissue edema by removal of interstitial fluid. Considering the deleterious effects of edema on microcirculation and tissue viability, the effect of TUF on skin flap survival was tested.

STUDY DESIGN AND SETTING: Survival of modified McFarlane skin flaps was determined in 40 Sprague-Dawley rats. In 20 treated animals, four 5-cm ultrafiltration catheters were placed in the subdermal plane of the distal flap 24 hours after flap elevation and connected to a down-regulated vacuum manifold for 8 hours. No catheters were placed in the control group.

RESULTS: Skin flap survival was improved in the experimental group (87.2 ± 1.6) over the control group (76.7 ± 2.2).

DISCUSSION: TUF effectively improved skin flap survival. These results provide evidence of the causal effect of edema on tissue viability. The relative ease of use of TUF would allow cost-effective clinical application of this technique.

Computed tomography scan does not correlate with patient experience of nasal obstruction

OBJECTIVES/HYPOTHESIS

Third-party payors have begun to demand imaging studies to document septal deviation prior to authorizing septoplasties. This study aims to determine whether septal deviation findings on computed tomography (CT) correlate with symptoms of nasal obstruction as determined by the Nasal Obstruction Symptom Evaluation (NOSE) scale.

STUDY DESIGN

Prospective and retrospective chart review.

METHODS

Patients 18 years or older undergoing CT scans, which included the nasal septum, were asked to complete a NOSE scale survey and report the laterality of any possible obstruction. Coronal CT images of subjects were graded by two blinded otolaryngologists and two blinded neuroradiologists using a grading system devised by the authors.

RESULTS

Seventy-three subjects met inclusion/exclusion criteria. Interobserver reliability about the degree of septal deviation on CT scans was moderately good to substantial (κ values, 0.43 to 0.72). There was poor correlation between NOSE scores and degree of deviation on CT scans (Kendall's τ, 0.031 to 0.045; P values all >.05). There was poor concordance between the side of symptoms that patients reported and the side that observers thought was most deviated on CT.

CONCLUSIONS

There is little correlation between septal deviation findings on CT scans and symptoms of nasal obstruction. The results do not support a role for CT scans as either a clinically meaningful or necessary test to investigate uncomplicated nasal obstruction.

LEVEL OF EVIDENCE

4.

Morbidity and cost of odontogenic infections

OBJECTIVE

Cost analysis of deep neck space infections from odontogenic origin and review of the morbidity of potentially preventable complications.

STUDY DESIGN

Case series with chart review.

SETTING

Level 1 trauma center and academic safety net hospital.

SUBJECTS AND METHODS

Patients treated for deep neck space infections due to an odontogenic source between 2001 and 2010 were reviewed. Two hundred patients were included in the study. Ninety-eight patients required inpatient admission. Twelve percent of these patients had difficult airways, and 16% had at least 1 day in the intensive care unit. Cost data were available only for the later 3.5 years of the study period.

RESULTS

The overall cost of treatment for these 71 individuals exceeded $1.1 million.

CONCLUSION

The cost of treatment for odontogenic infections is staggering. Based on assumptions of the percentage of infections in the metropolitan area captured at Hennepin County Medical Center, extrapolation to the total national cost of inpatient care approaches $200 million annually. This study highlights the importance of access to medical and preventative dental care for the general population and demonstrates the cost benefit that could be achieved through prevention of disease and, therefore, avoidance of its complications.

Implanted upper airway stimulation device for obstructive sleep apnea

OBJECTIVES/HYPOTHESIS

Previous feasibility studies have shown that electrical stimulation of the hypoglossal nerve can improve obstructive sleep apnea (OSA). The current study examined the safety and preliminary effectiveness of a second generation device, the Upper Airway Stimulation (UAS) system, and identified baseline predictors for therapy success.

STUDY DESIGN

Two consecutive open prospective studies.

METHODS

UAS systems were implanted in patients with moderate to severe OSA who failed or were intolerant of continuous positive airway pressure (CPAP). The study was conducted in 2 parts. In part 1, patients were enrolled with broad selection criteria. Apnea hypopnea index (AHI) was collected using laboratory-based polysomnography at preimplant and postimplant visits. Epworth Sleepiness Scale (ESS) and Functional Outcomes of Sleep Questionnaire (FOSQ) were also collected. In part 2, patients were enrolled using selection criteria derived from the experience in part 1.

RESULTS

In part 1, 20 of 22 enrolled patients (two exited the study) were examined for factors predictive of therapy response. Responders had both a body mass index ≤32 and AHI ≤50 (P < .05) and did not have complete concentric palatal collapse. Part 2 patients (n = 8) were selected using responder criteria and showed an improvement on AHI from baseline, from 38.9 ± 9.8 to 10.0 ± 11.0 (P < .01) at 6 months postimplant. Both ESS and FOSQ improved significantly in part 1 and 2 subjects.

CONCLUSIONS

The current study has demonstrated that therapy with upper airway stimulation is safe and efficacious in a select group of patients with moderate to severe OSA who cannot or will not use CPAP as primary treatment.

Efficacy of reductive ventricular osmotherapy in a swine model of traumatic brain injury

BACKGROUND

The presence of osmotic gradients in the development of cerebral edema and the effectiveness of osmotherapy are well recognized. A modification of ventriculostomy catheters described in this article provides a method of osmotherapy that is not currently available. The reductive ventricular osmotherapy (RVOT) catheter removes free water from ventricular cerebrospinal fluid (CSF) by incorporating hollow fibers that remove water vapor, thereby providing osmotherapy without increasing osmotic load.

OBJECTIVE

To increase osmolarity in the ventricular CSF through use of RVOT in vivo.

METHODS

Twelve Yorkshire swine with contusional injury were randomized to external ventricular drainage (EVD) or RVOT for 12 hours. MR imaging was obtained. Serum, CSF, and brain ultrafiltrate were analyzed. Histology was compared using Fluor-Jade B and hematoxylin and eosin (H & E) stains.

RESULTS

With RVOT, CSF osmolality increased from 292 ± 2.7 to 345 ± 8.0 mOsmol/kg (mean ± SE, P = 0.0006), and the apparent diffusion coefficient (ADC) in the injury region increased from 0.735 ± 0.047 to 1.135 ± .063 (P = 0.004) over 24 hours. With EVD controls, CSF osmolarity and ADC were not significantly changed. Histologically, all RVOT pigs showed no evidence of neuronal degeneration (Grade 1/4) compared to moderate degeneration (Grade 2.6 ± .4/4) seen in EVD treated animals (P = 0.02). The difference in intracranial pressure (ICP) by area under the curve approached significance at P = .065 by Mann Whitney test.

CONCLUSION

RVOT can increase CSF osmolarity in vivo after experimental traumatic brain injury (TBI). In anticipated clinical use, only a slight increase in CSF osmolarity may be required to reduce cerebral edema.

The effect of reductive ventricular osmotherapy on the osmolarity of artificial cerebrospinal fluid and the water content of cerebral tissue ex vivo

The purpose of this study was to explore a novel treatment involving removal of free water from ventricular cerebrospinal fluid (CSF) for the reduction of cerebra]l edema. The hypothesis is that removal of free water from the CSF will increase the osmolarity of the CSF, which will favor movement of tissue-bound water into the ventricles, where the water can be removed. Reductive ventricular osmotherapy (RVOT) was tested in a flowing solution of artificial CSF (aCSF) with two end-points: (1) the effect of RVOT on osmolarity of the CSF, and (2) the effect of RVOT on water content of ex vivo cerebral tissue. RVOT catheters are made up of membranes permeable only to water vapor. When a sweep gas is drawn through the catheter, free water in the form of water vapor is removed from the solution. With RVOT treatment, aCSF osmolarity increased from a baseline osmolarity of 318.8 ± 0.8 mOsm/L to 339.0 ± 3.3 mOsm/L (mean ± standard deviation) within 2 h. After 10 h of treatment, aCSF osmolarity approached an asymptote at 344.0 ± 4.2 mOsm/L, which was significantly greater than control aCSF osmolarity (p <<0.001 by t-test, n = 8). Water content at the end of 6 h of circulating aCSF exposure was 6.4 ± 0.9 g H₂O (g dry wt)⁻¹ in controls, compared to 6.1 ± 0.7 g H₂O (g dry wt)⁻ after 6 h of RVOT treatment of aCSF (p = 0.02, n = 24). The results support the potential of RVOT as a treatment for cerebral edema and intracranial hypertension.

Novel In Situ Collection of Tumor Interstitial Fluid from a Head and Neck Squamous Carcinoma Reveals a Unique Proteome with Diagnostic Potential

Introduction

Tumors lack normal drainage of secreted fluids and consequently build up tumor interstitial fluid (TIF). Unlike other bodily fluids, TIF likely contains a high proportion of tumor-specific proteins with potential as biomarkers.

Methods

Here, we evaluated a novel technique using a unique ultrafiltration catheter for in situ collection of TIF and used it to generate the first catalog of TIF proteins from a head and neck squamous cell carcinoma (HNSCC). To maximize proteomic coverage, TIF was immunodepleted for high abundance proteins and digested with trypsin, and peptides were fractionated in three dimensions prior to mass spectrometry.

Results

We identified 525 proteins with high confidence. The HNSCC TIF proteome was distinct compared to proteomes of other bodily fluids. It contained a relatively high proportion of proteins annotated by Gene Ontology as “extracellular” compared to other secreted fluid and cellular proteomes, indicating minimal cell lysis from our in situ collection technique. Several proteins identified are putative biomarkers of HNSCC, supporting our catalog’s value as a source of potential biomarkers.

Conclusions

In all, we demonstrate a reliable new technique for in situ TIF collection and provide the first HNSCC TIF protein catalog with value as a guide for others seeking to develop tumor biomarkers.

Electronic supplementary material

The online version of this article (doi:10.1007/s12014-010-9050-3) contains supplementary material, which is available to authorized users.

A Preliminary Theoretical Model of Hydrodynamics in the Inner Ear

Head movement should create a transient pressure imbalance across the membranous inner ear. We used basic concepts of fluid dynamics to develop a theoretical model of the inner ear. According to this model, two contiguous fluidic systems—the perilymphatic system and the endolymphatic system—are in hydrostatic equilibrium across a compliant membrane. Our model demonstrates that changes in resistance or compliance in one system results in a transient distortion of the membranous inner ear until equilibrium between the two systems is restored. The concept of hydrodynamic pressure changes in the inner ear has received little attention, but it may represent a new approach to understanding the inner ear and treating inner ear diseases.

A preliminary theoretical model of hydrodynamics in the inner ear

Head movement should create a transient pressure imbalance across the membranous inner ear. We used basic concepts of fluid dynamics to develop a theoretical model of the inner ear. According to this model, two contiguous fluidic systems-the perilymphatic system and the endolymphatic system-are in hydrostatic equilibrium across a compliant membrane. Our model demonstrates that changes in resistance or compliance in one system results in a transient distortion of the membranous inner ear until equilibrium between the two systems is restored. The concept of hydrodynamic pressure changes in the inner ear has received little attention, but it may represent a new approach to understanding the inner ear and treating inner ear diseases.

Diagnosis and treatment of deep neck space abscesses

Objective: To review our experience with deep neck abscesses and identify unique trends in our patient population.

Study Design: Case series with chart review.

Subjects and Methods: Evaluation of patients with deep neck space abscesses between 2001 and 2006. Peritonsillar abscess, superficial craniocervical infection, and salivary gland infections were excluded from selection of study population. A total of 106 cases were reviewed.

Results: Dental infections were the most common cause of deep neck abscesses (49.1%). Comorbidities included substance abuse (53.7%), psychiatric illness (10.4%), hypertension (9.4%), head and neck cancer (6.6%), and diabetes mellitus (5.7%). All patients received systemic antibiotics, eight patients required tracheotomy, 85 patients underwent surgical drainage in the operating room, and 11 had bedside drainage. Median and lower quartile of time in hospital was 2 and 3 days, respectively, whereas upper quartile was 4 days (range, 1 to 27 days). Patients with comorbidities or concurrent illness tended to stay longer ( P < 0.05, Mann-Whitney test). There were six complications and no mortality.

Conclusion: Substance abuse and poor orodental hygiene are important predisposing factors to deep neck abscesses. Appropriate management continues to favor a combination of early surgical drainage and systemic antibiotics.

Surgical debridement and adjunctive hyperbaric oxygen in cervical necrotizing fasciitis

Objective: To review our management of cervical necrotizing fasciitis (CNF) with the use of adjunctive hyperbaric oxygen therapy (HBO).

Study Design: Case series with chart review.

Subjects and Methods: Evaluation of ten patients with CNF between 2001 to 2006.

Results: There were five male and six female patients. Mean age was 43 ± 11 years. Eight cases resulted from an odontogenic source. Comorbidities included diabetes mellitus, hypertension, and substance abuse. All patients had computed tomography scans performed, received intravenous antibiotics, and underwent surgical debridement. Eight patients underwent surgery within 24 hours. The average number of debridements was 2.2 ± 0.8. Hospitalization was twice as long for diabetic patients (15.5 ± 8.16 days) compared with nondiabetic patients (7.5 ± 1.6 days, P = 0.029). Nine patients had HBO therapy. Combined data revealed a possible decrease in length of hospitalization with HBO therapy ( P < 0.001). No mortality was documented.

Conclusion: In addition to early and aggressive medical management and surgical debridement, this study suggests that HBO therapy is a beneficial adjunct by potentially decreasing length of hospitalization. Randomized trials are still needed to demonstrate its efficacy.

Estimation of perilymph concentration of agents applied to the round window membrane by microdialysis

OBJECTIVE

The round window membrane (RWM) is known to be permeable to various biological substances. Application of biological substances to the RWM has been shown to affect inner ear fluid composition and damage hair cells, resulting in functional changes RWM instillation of gentamicin, a preferentially vestibulotoxic aminoglycoside, is used as a therapeutic treatment for patients with intractable vertigo and is gaining acceptance as a chemical vestibular ablation agent, despite considerable variations in the incidence and severity of hearing loss associated with gentamicin. Clearly, the susceptibility of vestibular and auditory hair cells to the ototoxic effects of gentamicin is not well understood. The aim of this study was to understand the kinetics of urea and methylene blue instilled into the inner ear space through the RWM and to establish a method for determining the optimal dosage for the treatment of inner ear disorders.

MATERIAL AND METHODS

We used inner ear microdialysis to quantify changes in perilymph concentration of low molecular weight agents applied to the RWM in a chinchilla model.

RESULTS

Preliminary results after placement of a microdialysis probe and application of a low molecular weight marker (urea) to the RWM were extrapolated from a time versus concentration plot from dialysates sampled over a 3-min interval using modifications of standard microdialysis equations for estimation of in vivo recovery. Our data suggest that inner ear microdialysis can be used to measure the pharmacokinetics of a low molecular weight agent within the perilymphatic space without the need for repeated direct sampling.

CONCLUSION

Inner ear microdialysis may be a useful method for establishing a therapeutic dosage for ototoxic agents used in the treatment of inner ear disorders.

The effect of capillary ultrafiltration probes on skin flap edema

OBJECTIVE

Edema clearly has deleterious effects on the microcirculation and, consequently, cell viability. Prior work from this laboratory demonstrated that hyperosmolar microdialysis can reduce tissue edema, but this method is technically challenging. A new, simpler technique of microdialysis using capillary ultrafiltration probes (CUPs) has been studied to determine if CUP microdialysis is as effective in reducing tissue edema in the same animal model.

METHODS

Twenty-four Sprague-Dawley rats were studied using a modified McFarlane skin flap. Microdialysis was accomplished using a catheter constructed of four 4-cm hollow fibers that were connected to polyethylene tubing. Catheters on the experimental side of the flap were attached to a vacuum manifold for 8 hours. The control side was treated in 2 ways. In group 1, catheters were placed but not applied to suction. In group 2, no catheters are placed on the control side. Tissue water content was determined by a biopsy-drying technique.

RESULTS

Tissue water content was significantly reduced (by paired t test) in both groups by a mean of 3.2 mL/100 g of wet tissue.

CONCLUSION

CUP microdialysis reduced tissue water content as effectively as did hyperosmolar microdialysis, but in a simpler and therefore more cost-effective method. The technique could be easily adapted for clinical application.

Financial support for research in otolaryngology

OBJECTIVES

This project describes the use of computer-assisted searches of medical literature in an attempt to track the prevalence and type of funding of medical research.

STUDY DESIGN AND SETTING

The study is a computer-assisted observational survey of the medical literature. To establish a database and track funding trends, a computer-assisted Medline search (CAMS) of the literature from 1986 to 1991 and 1992 to August 1996 was undertaken for 3 areas of interest: (1) sources of support, (2) comparison with other specialties, and (3) the validity of CAMS. A journal-based search examined the field of otolaryngology, which includes all the head and neck related sciences, and an institution-based search examined the clinical specialty of otolaryngology.

RESULTS

By selected journal search, the field of otolaryngology has about one-third funding (34% of 20,751 papers), and about one-half of that is supported by the National Institutes of Health. This proportion of federal support increased over time. By institution line search, the specialty of otolaryngology is less well funded (26% of 15,480 papers) as might be expected. However, in contrast to basic sciences, there is a trend of decreased funding over the 11-year period of the study.

SIGNIFICANCE

It appears that while the field of otolaryngology (basic scientists and clinicians) may be enjoying increasing support of research, the clinical specialty of otolaryngology is among the many specialties that exhibit a trend of decreasing level of NIH support.

CONCLUSIONS

Computer-assisted surveys are an effective method of tracking funding for research in otolaryngology and other specialties. CAMS may be a valuable tool for monitoring efforts to improve funding resources for otolaryngology.

Blood-labyrinth barrier and fluid dynamics of the inner ear

Under normal conditions, the inner ear possesses remarkably stable homeostatic mechanisms for the maintenance of functional integrity of the inner ear fluid. The inner ear fluid maintains its homeostasis by a variety of regulatory mechanisms such as an ion transport system, a blood-labyrinth barrier, and a constant blood supply. Highly regulated transport of ions into and out of the inner ear provides for the maintenance of inner ear fluid composition necessary for auditory transduction. Any disturbance in one of these mechanisms can disrupt homeostasis expressed by ionic, osmotic, or metabolic imbalance between the compartments. Free radicals, stress hormones, noise exposure, and aminoglycoside antibiotics may induce short- and long-term effects on cellular function of the auditory or vestibular system (or both) and serve as a triggering mechanism for abrupt functional disturbances of inner ear fluid ion homeostasis. In this article, we present a comprehensive review of the mechanisms underlying inner ear fluid homeostasis necessary for normal auditory function and factors that can disrupt homeostasis and lead to functional disturbances, namely sensorineural hearing loss, tinnitus, and vertigo.

Effect of stress-related hormones on inner ear fluid homeostasis and function

HYPOTHESIS

Induction of suprathreshold levels of stress-related hormone by systemic administration of epinephrine can change inner ear fluid homeostasis and function.

BACKGROUND

Meniere's disease is frequently associated with high levels of anxiety and other forms of psychological disturbance. Most clinicians agree that emotional stress or severe anxiety can precipitate relapse or aggravate the symptoms. In general, it is known that stress-related hormones such as epinephrine, norepinephrine, vasopressin, aldosterone, and cortisol are released into systemic circulation in response to stress. Significantly higher levels of plasma norepinephrine and vasopressin in patients with Meniere's disease have been reported.

METHODS

Concentrations of sodium and potassium in perilymph were measured by a flame photometer after systemic infusion of epinephrine (6.3 microg/min for 3 hours). Control animals were treated with equal volumes of 0.9% physiologic saline. Compound action potentials (CAP) elicited by brief tone bursts were measured before and 3 hours after the infusion of epinephrine. For chronic studies, epinephrine (10 microg/d/kg) was given by osmotic pump implanted subcutaneously for 1, 2, 3, and 4 weeks, respectively. Click- and tone-evoked auditory brain responses (ABRs) were measured at 1, 2, 3, and 4 weeks after epinephrine administration.

RESULTS

Concentrations of sodium and potassium increased significantly in perilymph (p < 0.001 and p < 0.01) after epinephrine infusion over controls. The osmolality increased significantly in serum and perilymph after epinephrine infusion. The CAP threshold was significantly elevated at all frequencies. The shift of the CAP threshold caused by epinephrine tended to be larger at higher frequencies. In chronic studies, epinephrine administration caused a transient 20 to 45 dB threshold shift that increased with time and was relatively constant across frequency.

CONCLUSIONS

There is good evidence to suggest that stress-related hormones such as epinephrine can alter inner ear fluid homeostasis and auditory function. This study confirmed this hypothesis and illuminated the processes of alteration by demonstrating specific changes in perilymph composition and auditory function.

Hyperosmosis of cerebral injury

Changes in tissue osmolarity or cerebrospinal fluid osmolarity after cerebral injury have received little attention in the literature, but osmosis may be an important cause of early cerebral edema. This paper reviews concepts and terms relating to osmosis, and reviews the few papers in the literature which have studied osmolarity after cerebral injury. In studies of both traumatic brain injury and ischemia, tissue osmolarity is elevated. Osmolarity of cerebrospinal fluid has also been shown to increase with injury. There have been no human studies examining osmolarity of tissue or cerebrospinal fluid after cerebral injury. Theoretical implications of the osmotic gradient are discussed.

Use of the tunable dye laser to delay McFarlane skin flaps

OBJECTIVE

To determine whether the argon tunable dye laser, used in a noncutting, hemocoagulative mode, improves skin flap survival as effectively as a surgical delay procedure.

DESIGN

A physiologic, controlled trial was completed with three groups: acute control skin flaps, surgical delay skin flaps, and experimental laser delay skin flaps. The outcome variable was percentage of skin flap survival.

SUBJECTS

Forty-four male Sprague-Dawley rats.

INTERVENTIONS

McFarlane skin flaps were raised in all groups. The first group had no delay procedure, the second had the standard surgical delay, and the third group was lased at the periphery of the flap 2 weeks before raising the acute flap.

RESULTS

The acute control group had survival of 85.7% +/- 1.5% (mean +/- SE) of skin flaps; surgical control group, 94.4% +/- 0.7%; laser delay group, 96.5% +/- 0.1%. The survival of the experimental group was better than the acute control group and was not different from the surgical delay group by the Scheffé multiple comparison test.

CONCLUSIONS

This research may lead to a technique to reproduce the benefits of the delay phenomenon without the risks and cost of a surgical procedure.

Comparison of tunable dye and KTP lasers in nonsurgical delay of cutaneous flaps

PROBLEM

Reproducing the benefits of the delay phenomenon without the risks and costs of a surgical procedure has long been a goal of skin flap physiologists. After the success of the suture-delay technique and argon tunable dye laser in improving survival in McFarlane skin flaps, important questions remained: (1) will laser delay be effective in dermal flaps, (2) can induction of collateral blood flow be documented, and (3) is the KTP laser, which is generally more available to otolaryngologists, more effective than the argon tunable dye laser.

METHODS

The KTP and argon tunable dye lasers were compared by use of the laser-delay technique, with two outcome measures - blood flow and survival. The laser-delay procedure was accomplished with the laser in a noncutting mode in an attempt to coagulate cutaneous vessels at the periphery of a planned skin flap. The objective was to induce collateralization and improve skin flap survival. Patterns of blood flow were tested by use of the base occlusion test. Flap survival of an acute control flap group was compared with that of the laser delay groups.

RESULTS

Blood flowing to the distal flap area originated from the base of the flap area after laser delay. Flap survival of the laser delay groups was significantly improved over that of the control group.

CONCLUSION

Both lasers were able to effectively induce collateralization and improve flap survival.

Comparison of Tunable Dye and KTP Lasers in Nonsurgical Delay of Cutaneous Flaps

PROBLEM: Reproducing the benefits of the delay phenomenon without the risks and cost of a surgical procedure has long been a goal of skin flap physiologists. After the success of the suture-delay technique and argon tunable dye laser in improving survival in McFarlane skin flaps, important questions remained: (1) will laser delay be effective in dermal flaps, (2) can induction of collateral blood flow be documented, and (3) is the KTP laser, which is generally more available to otolaryngologists, more effective than the argon tunable dye laser.

METHODS: The KTP and argon tunable dye lasers were compared by use of the laser-delay technique, with two outcome measures-blood flow and survival. The laser-delay procedure was accomplished with the laser in a noncutting mode in an attempt to coagulate cutaneous vessels at the periphery of a planned skin flap. The objective was to induce collateralization and improve skin flap survival. Patterns of blood flow were tested by use of the base occlusion test. Flap survival of an acute control flap group was compared with that of the laser delay groups.

RESULTS: Blood flowing to the distal flap area originated from the base of the flap area after laser delay. Flap survival of the laser delay groups was significantly improved over that of the control group.

CONCLUSION: Both lasers were able to effectively induce collateralization and improve flap survival.

Reduction of tissue edema by microdialysis

OBJECTIVE

This is the first report (to our knowledge) of the use of tissue microdialysis to reduce tissue edema. In this study, a hyperosmotic solution was perfused through microdialysis catheters, allowing direct treatment of interstitial edema by osmosis.

DESIGN

First, the catheter and perfusate characteristics were tested in vitro. A physiologic, controlled trial was then performed, with two outcome variables: osmolarity of the effluent and tissue water content.

SUBJECTS

Twenty male Sprague-Dawley rats. One rat was withdrawn.

INTERVENTIONS

Tissue microdialysis catheters were implanted in the rats. The control side of the animals was not perfused. The experimental side was perfused for 9 hours.

RESULTS

Osmolarity of the perfusate was reduced 16.5 mOsm after passing through the catheter, indicating that fluid was removed from the tissue. Tissue edema was reduced by an average 1.8 mL of fluid per 100 g of wet tissue.

CONCLUSIONS

Tissue microdialysis removed tissue fluid and reduced edema. This treatment may have a beneficial effect on edematous tissues. Potential use and limitations of this therapeutic modality are discussed.

Nonsurgical delay of skin flaps: effect of a suture delay technique on blood flow and survival

Surgical delay is the only clinical means of improving survival of skin flap tissue, but it has inherent risks and costs of a surgical procedure. This study tested the hypothesis that any method of disrupting the circulation at the distal perimeter of a planned skin flap would induce collateral circulation from the base of the flap and thereby improve flap survival. The suture delay technique was performed on rats, and two outcome measures were used: blood flow patterns and skin flap survival. Blood flow patterns were tested before and after the suture technique by means of the base occlusion test. Flap survival in the suture delay group was compared with survival in acute and surgical delay control groups. Flap survival in the suture delay group (95.6% +/- 0.6%, n = 22) was significantly greater than in the acute control group (85.7% +/- 1.6%, n = 22) and was not different from that in the surgical delay model (95.2% +/- 0.5%, n = 21). Laser Doppler studies demonstrated a change in blood flow patterns. This study supports the theory that the mechanism of the delay phenomenon is the development of collateral blood from the base of the flap and suggests that the benefits of delay can be achieved with minimal surgical trauma.

Management of unilateral vocal fold paralysis

Management of unilateral vocal fold paralysis continues to generate controversy. Polytetrafluoroethylene (Teflon) injection remains the most popular procedure for medialization; however, there are problems involved with its use. Endoscopic assessment of patients treated with medialization laryngoplasty revealed a normal mucosal wave form in contrast to the stiff vocal fold observed with Teflon injection. Medialization laryngoplasty is also considered a reversible procedure. Based on these findings, medialization laryngoplasty should be considered the procedure of choice for unilateral vocal fold paralysis.

Fluorescein and acidosis. Implications for flap perfusion studies

The visual fluorescein technique underpredicts survival of a skin flap during the first 24 hours after raising the flap. This problem limits its use as a research and clinical tool. There is no compelling explanation for this observation, but two facts are known: fluorescein is a derivative of phthalein, a pH indicator, and ischemic tissues become acidotic, with the pH falling below 7.0. These observations lead to the hypothesis that acidosis quenches fluorescence in distal skin flaps. No data could be found regarding this effect. Therefore, the effect of acidosis on sodium fluorescein was studied in vitro. A spectrophotometer was used to measure the intensity of the fluorescence of sodium fluorescein in buffered solutions of different hydrogen ion concentrations. Two studies were performed at different concentrations of fluorescein. At a concentration of 10(-5) g/mL, there is a drop of 26% in fluorescence intensity from pH 7.5 to 7.0, and 51% between pH 7.5 and 6.5. At 10(-7) g/mL, there is a 43% decrease in fluorescence between pH 7.5 and 6.5. This study supports our hypothesis that acidosis quenches the fluorescence of fluorescein. This effect must be considered when interpretating basic studies of skin flap microcirculation.

Monocortical miniplate fixation of mandibular angle fractures

Noncompression monocortical miniplate fixation of mandibular fractures has become a reliable method of providing rigid fixation and eliminating the need for intermaxillary fixation. Recent studies, using a variety of internal fixation techniques, have described high complication rates at the mandibular angle. This article compares the use of one miniplate vs two miniplates in treatment of angle fractures. Since September 1985, 61 patients with 63 mandibular angle fractures have been treated with miniplates. Forty-four fractures were fixed with two miniplates. Six complications (3.1%) occurred, five of which were in the one-miniplate group. The complication rate in the double-miniplate group is the lowest reported of any plating technique. The use of two miniplates has proved to be an effective method of treating mandibular angle fractures.

Measurement of interstitial tissue compliance in skin flaps

Investigators speculate about the role of tissue pressure in skin flap necrosis as increased tissue pressure has been demonstrated to stop capillary blood flow in other conditions, both clinically and experimentally. Unfortunately, interstitial tissue pressure is difficult to measure by conventional methods. This article describes a new practical technique that measures interstitial tissue compliance as a correlate of interstitial tissue pressure. The instrument and method are described in detail. Tissue compliance was measured in normal dorsal skin and in modified McFarlane's skin flap in Sprague-Dawley rats. The skin flaps were measured at three sites (proximal, middle, and distal) at 2, 12, and 18 hours of age. The mean difference between the normal skin and all skin flaps was statistically significant. Within the skin flaps, there was a trend toward increased pressure with increasing age of the flap and distance from the flap base. These trends are statistically significant by the analysis of variance test. The data from this study support the validity of the technique and the hypothesis that increased interstitial tissue pressure is present in skin flaps.