Exploring assessment of balance using virtual reality in patients at risk of chemotherapy-induced peripheral neuropathy

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a common dose-limiting toxicity for people treated for cancer. Impaired balance and falls are functional consequences of CIPN. Virtual reality (VR) technology may be able to assess balance and identify patients at risk of falls.

AIMS

To assess the impact of potentially neurotoxic chemotherapy on balance using VR, and explore associations between VR balance assessment, falls and CIPN.

METHODS

This prospective, repeated measures longitudinal study was conducted at two Australian cancer centres. Eligible participants were commencing adjuvant chemotherapy containing a taxane for breast cancer, or oxaliplatin for colorectal cancer (CRC), per institutional guidelines. Balance assessments using VR were conducted at baseline, end of chemotherapy and 3 and 6 months after completion of chemotherapy. Participants also completed a comprehensive CIPN assessment comprising clinical and patient-reported outcomes, and recorded falls or near falls.

RESULTS

Out of 34 participants consented, 24 (71%) had breast cancer and 10 (29%) had CRC. Compared to baseline, balance threshold was reduced in 10/28 (36%) evaluable participants assessed at the end of chemotherapy, and persistent in 7/22 (32%) at 6 months. CIPN was identified in 86% at end of chemotherapy and persisted to 6 months after chemotherapy completion in 73%. Falls or near falls were reported by 12/34 (35%) participants, and were associated with impaired VR balance threshold (P = 0.002).

CONCLUSIONS

While VR balance assessment was no better at identifying CIPN than existing measures, it is a potential surrogate method to assess patients at risk of falls from CIPN.

Machine learning methods applied to audit of surgical margins after curative surgery for facial (non-melanoma) skin cancer

We aimed to build a model to predict positive margin status after curative excision of facial non-melanoma skin cancer based on known risk factors that contribute to the complexity of the case mix. A pathology output of consecutive histology reports was requested from three oral and maxillofacial units in the south east of England. The dependent variable was a deep margin with peripheral margin clearance at a 0.5 mm threshold. A total of 3354 cases were analysed. Positivity of either the peripheral or deep margin for both squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) was 15.4% at Unit 1, 21.1% at Unit 2, and 15.4% at Unit 3. Predictive models accounting for patient and tumour factors were developed using automated machine learning methods. The champion models demonstrated good discrimination for predicting margin status after excision of BCCs (AUROC = 0.67) and SCCs (AUROC = 0.71). We demonstrate that rates of positive excision margins of facial non-melanoma skin cancer (fNMSC), when adjusted by the risk prediction model, can be used to compare unit performance fairly once variations in tumour factors and patient factors are accounted for.

Machine learning methods applied to risk adjustment of cumulative sum chart methodology to audit free flap outcomes after head and neck surgery

We describe a risk adjustment algorithm to benchmark and report free flap failure rates after immediate reconstruction of head and neck defects. A dataset of surgical care episodes for curative surgery for head and neck cancer and immediate reconstruction (n = 1593) was compiled from multiple NHS hospitals (n = 8). The outcome variable was complete flap failure. Classification models using preoperative patient demographic data, operation data, functional status data and tumour stage data, were built. Machine learning processes are described to model free flap failure. Overall complete flap failure was uncommon (4.7%) with a non-statistical difference seen between hospitals. The champion predictive model had acceptable discrimination (AUROC 0.66). This model was used to risk-adjust cumulative sum (CuSUM) charts. The use of CuSUM charts is a viable way to monitor in a 'Live Dashboard' this quality metric as part of the quality outcomes in oral and maxillofacial surgery audit.

Centralised pathology service for sentinel node biopsy in oral cavity cancer: The Southeast England Consortium experience

BACKGROUND

Sentinel lymph node biopsy is an increasingly recognised option for accurate staging and subsequent management of the clinically negative neck in early stage oral cavity squamous cell carcinoma. However, the technique is currently underused due to several logistic constraints including increased burden on pathology services. Here, we describe the feasibility of an outsourced centralised pathology processing and reporting service for sentinel lymph node biopsies in oral cavity squamous cell carcinoma.

PATIENTS AND METHODS

The Southeast England Consortium comprises four surgical centres utilising a central pathology service. Consecutive cases between January 2016 and February 2020 were retrospectively evaluated for survival outcomes and laboratory turnaround times.

RESULTS

Twenty-eight per cent from a cohort of 139 patients had positive sentinel nodes. There was a trend towards greater overall, disease-free and disease-specific survival (OS, DFS and DSS, respectively) in sentinel node negative compared to sentinel node positive patients, but these differences were not statistically significant. The sensitivity, negative predictive value and false negative rate were 92.8%, 97.0% and 6.8%, respectively. The mean and mode laboratory TAT were 5 and 4 working days, respectively.

CONCLUSION

An outsourced centralised pathology service is a feasible option to widen the availability of sentinel node biopsy in oral cavity squamous cell carcinoma.

BAOMS QOMS: findings from the pilot phase and lessons learned in the feasibility evaluation of a national quality improvement initiative

The BAOMS QOMS pilot was developed and run in six England OMFS units between December 2019 - April 2020. The aims of this pilot project were: to evaluate feasibility of the questionnaires developed for the audit and how effective they were with regards to quality improvement, to test the processes associated with the data collection system and finally, to provide baseline data to support patient data collection without the requirement of prospective consent. The pilot included a series of six audits (oral and dentoalveolar [ODA], oncology, orthognathic, reconstruction, trauma, and skin). Data entry was clinician-led in five OMFS units and in one unit (EKHU), it was additionally supported by members of the clinical coding team. One hundred and twenty-eight REDCap account user details were issued and of these, 45 (35%) completed registration and 22 (17%) were active users who participated in the pilot data entry. Disproportionate focus on individual audits within QOMS was seen, though not all units offered the full range of service audited. Users suggest the skin and ODA audits were sufficiently clear, but improvement is required in the oncology and reconstruction questionnaire particularly. The pilot was successful in aiding the project team identify areas of weaknesses and strength in the design of the REDCap registry and implementation of the next phase of the initiative. The information and experience gained has to date enabled a successful application for section 251 approval from the HRA and progress for the next phase of national data collection.

Validating a risk stratification tool for audit of early outcome after operations for squamous cell carcinoma of the head and neck

The aim of this study was to validate a case-mix adjustment tool (neural network) for the audit of postoperative outcomes. We tested its calibration and discrimination on two unseen groups of patients being treated for squamous cell carcinoma (SCC) of the head and neck and compared observed complication rates with predicted rates. A total of 196 patients who were treated at two UK NHS institutions between 2016 and 2018 were audited. Preoperative data pertaining to risk (T classification, complexity of operation, and "high-risk" status) were collected, together with data on postoperative complications. Diagnostic test statistics and receiver operating curves (ROC) were used to test the performance of the tool. The score was well calibrated (predicted and observed complication rates both 43%), but discrimination suggested only fair accuracy (ROC 0.66 - 0.68). Adjustment of case mix for the audit of postoperative complications is difficult, although our model suggests that departmental audit is possible, and its accuracy is equivalent to that of other national audits. Further work may elucidate key variables that have not yet been assessed.

Validating a benchmarking tool for audit of early outcomes after operations for head and neck cancer

INTRODUCTION In 2013 all UK surgical specialties, with the exception of head and neck surgery, published outcome data adjusted for case mix for indicator operations. This paper reports a pilot study to validate a previously published risk adjustment score on patients from separate UK cancer centres. METHODS A case note audit was performed of 1,075 patients undergoing 1,218 operations for head and neck squamous cell carcinoma under general anaesthesia in 4 surgical centres. A logistic regression equation predicting for all complications, previously validated internally at sites A-C, was tested on a fourth external validation sample (site D, 172 operations) using receiver operating characteristic curves, Hosmer-Lemeshow goodness of fit analysis and Brier scores. RESULTS Thirty-day complication rates varied widely (34-51%) between the centres. The predictive score allowed imperfect risk adjustment (area under the curve: 0.70), with Hosmer-Lemeshow analysis suggesting good calibration. The Brier score changed from 0.19 for sites A-C to 0.23 when site D was also included, suggesting poor accuracy overall. CONCLUSIONS Marked differences in operative risk and patient case mix captured by the risk adjustment score do not explain all the differences in observed outcomes. Further investigation with different methods is recommended to improve modelling of risk. Morbidity is common, and usually has a major impact on patient recovery, ward occupancy, hospital finances and patient perception of quality of care. We hope comparative audit will highlight good performance and challenge underperformance where it exists.

Diagnostic investigation of parotid neoplasms: a 16-year experience of freehand fine needle aspiration cytology and ultrasound-guided core needle biopsy

This study aimed to examine the diagnostic yield of fine needle aspiration cytology (FNAC) and ultrasound-guided core needle biopsy (USCB) in the diagnosis of parotid neoplasia. A 16-year retrospective analysis was performed of patients entered into our pathology database with a final diagnosis of parotid neoplasia. FNAC and USCB data were compared to surgical excision where available. One hundred and twenty FNAC, 313 USCB, and 259 surgical specimens were analyzed from 397 patients. Fifty-six percent of FNAC and 4% of USCB were non-diagnostic. One hundred and thirty-two (33%) patients had a final diagnosis made by USCB and did not undergo surgery. Surgery was performed in 257 (65%) patients, 226 (88%) of whom had a preoperative biopsy. Most lesions were benign, but there were 62 parotid and 13 haematological malignancies diagnosed; false-negative results were obtained in three FNAC and two USCB samples. The sensitivity and specificity of FNAC were 70% and 89%, respectively, and for USCB were 93% and 100%, respectively. This study represents the largest series of patients with a parotid neoplasm undergoing USCB for diagnosis. USCB is highly accurate with a low non-diagnostic rate and should be considered an integral part of parotid assessment.

Is benchmarking possible in audit of early outcomes after operations for head and neck cancer?

There is a need for a validated means of adjusting for case mix in morbidity audits of patients with cancer of the head and neck. To address this, we did a multicentre audit of 3 U.K. NHS cancer networks that treat patients with head and neck cancer, to compare the incidence of early adverse postoperative outcomes and to develop a means of adjusting for case mix. We did a retrospective and prospective audit of the case notes of 901 consecutive patients who had 1034 operations for squamous cell carcinoma (SCC) of the head and neck under general anaesthesia at 3 NHS hospitals. Analysis of raw data showed postoperative 30-day mortality (n=17) to be consistent between sites (1.7%-1.9%) but 30-day complication rates varied more (34%-49%). Logistic regression models predicting morbidity discriminated well (area under the curve 0.74-0.76). Adjusted morbidity rates for the 3 units were compared on a funnel plot with 95% and 99% confidence intervals to account for random variation. It is possible to benchmark surgical performance by focusing on early postoperative outcomes in head and neck surgery. Morbidity is common and usually has a considerable impact on recovery, bed occupancy, cost, and the patient's perception of the quality of care.

Aortoesophageal Fistula: A Case Report

Patients with impacted foreign bodies in the upper aerodigestive tract present commonly to ENT clinics. This case report highlights two important issues in the management of these patients. First, if the evidence of esophageal perforation is strong and contrast swallow is negative, the physician must consider further imaging, such as contrast computed tomography. Second, ENT physicians must beware of the complications of esophageal trauma, including major vascular injury and aortoesophageal fistula, in patients with retained sharp foreign bodies in the mid-esophagus.

Aortoesophageal fistula: a case report

Patients with impacted foreign bodies in the upper aerodigestive tract present commonly to ENT clinics. This case report highlights two important issues in the management of these patients. First, if the evidence of esophageal perforation is strong and contrast swallow is negative, the physician must consider further imaging, such as contrast computed tomography. Second, ENT physicians must beware of the complications of esophageal trauma, including major vascular injury and aortoesophageal fistula, in patients with retained sharp foreign bodies in the mid-esophagus.

With adequate supervision, the grade of the operating surgeon is not a determinant of outcome for patients undergoing urgent colorectal surgery

INTRODUCTION

It is essential that higher surgical trainees (HSTs) obtain adequate emergency operative experience without compromising patient outcome. The aim of this study was to compare the outcomes of patients operated by HSTs with those operated by consultants and to look at the effect of consultant supervision.

PATIENTS AND METHODS

A retrospective analysis of 362 patients who underwent urgent colorectal surgery was performed. The primary outcome was 30-day mortality. Secondary outcomes were intra-operative and postoperative surgery, specific and systemic complications, and delayed complications.

RESULTS

Comparison of the patients operated by a consultant (n = 190) and a HST (n = 172) as the primary surgeon revealed no significant difference between the two groups for age, gender, ASA status or indication for surgery. There was a difference in the type of procedure performed (left-sided resections: consultants 122/190, HST 91/172; P = 0.050). There was no difference between the two groups for the primary and secondary outcomes. However, HSTs operating unsupervised performed significantly fewer primary anastomoses for left-sided resections (P = 0.019) and had more surgery specific complications (P = 0.028) than those supervised by a consultant.

CONCLUSIONS

HSTs can perform emergency colorectal surgery with similar outcomes to their consultants, but adequate consultant supervision is vital to achieving these results.

CT-angiography for the detection of a lower gastrointestinal bleeding source

The evaluation of lower gastrointestinal bleeding (LGIB) often involves the collaborative efforts of the gastroenterologist, radiologist, and surgeon. Efforts to localize the acute LGIB have traditionally involved colonoscopy, technetium-labeled red blood cell (RBC) scintigraphy, angiography, or a combination of these modalities. The sensitivity of each method of diagnosis is limited, with the most common cause of a negative study the spontaneous cessation of hemorrhage. Other technical factors include vasospasm, lack of adequate contrast volume or exposure time, a venous bleeding source, and a large surface bleeding area. We report the use of multidetector computed tomography (MDCT), or CT-angiography (CT-A), in the initial evaluation of LGIB, and speculate on the incorporation of this technique into a diagnostic algorithm to treat LGIB. MDCT may offer a very sensitive means to evaluate the source of acute LGIB, while avoiding some of the morbidity and intense resource use of contrast angiography, and may provide unique morphologic information regarding the type of pathology. Screening with the more rapid and available MDCT, followed by either directed therapeutic angiography or surgical management, may represent a reasonable algorithm for the early evaluation and management of acute LGIB in which an active bleeding source is strongly suspected.

CT-Angiography for the Detection of a Lower Gastrointestinal Bleeding Source

The evaluation of lower gastrointestinal bleeding (LGIB) often involves the collaborative efforts of the gastroenterologist, radiologist, and surgeon. Efforts to localize the acute LGIB have traditionally involved colonoscopy, technetium-labeled red blood cell (RBC) scintigraphy, angiography, or a combination of these modalities. The sensitivity of each method of diagnosis is limited, with the most common cause of a negative study the spontaneous cessation of hemorrhage. Other technical factors include vasospasm, lack of adequate contrast volume or exposure time, a venous bleeding source, and a large surface bleeding area. We report the use of multidetector computed tomography (MDCT), or CT-angiography (CT-A), in the initial evaluation of LGIB, and speculate on the incorporation of this technique into a diagnostic algorithm to treat LGIB. MDCT may offer a very sensitive means to evaluate the source of acute LGIB, while avoiding some of the morbidity and intense resource use of contrast angiography, and may provide unique morphologic information regarding the type of pathology. Screening with the more rapid and available MDCT, followed by either directed therapeutic angiography or surgical management, may represent a reasonable algorithm for the early evaluation and management of acute LGIB in which an active bleeding source is strongly suspected.

Pathophysiology of septic encephalopathy: a review

OBJECTIVES

Encephalopathy is a common complication of sepsis. This review describes the different pathologic mechanisms that may be involved in its etiology.

DATA SOURCES

The studies described here were derived from the database PubMed (http:¿¿www.nlm.nih.gov) and from references identified in the bibliographies of pertinent articles and books. The citations are largely confined to English language articles between 1966 and 1998. Older publications were used if they were of historical significance.

STUDY SELECTION

All investigations in which any aspect of septic encephalopathy was reported were included. This selection encompasses clinical, animal, and in vitro cell culture work.

DATA EXTRACTION

The literature cited was published in peer-reviewed clinical or basic science journals or in books.

DATA SYNTHESIS

Contradictions between the results of published studies are discussed.

CONCLUSIONS

The most immediate and serious complication of septic encephalopathy is impaired consciousness, for which the patient may require ventilation. The etiology of septic encephalopathy involves reduced cerebral blood flow and oxygen extraction by the brain, cerebral edema, and disruption of the blood-brain barrier that may arise from the action of inflammatory mediators on the cerebrovascular endothelium, abnormal neurotransmitter composition of the reticular activating system, impaired astrocyte function, and neuronal degeneration. Currently, there is no treatment.

Faecal peritonitis causes oedema and neuronal injury in pig cerebral cortex

Encephalopathy is a common complication of sepsis. However, little is known about the morphological changes that occur in the brain during sepsis. Faecal peritonitis was induced in pigs that were killed 8 h later and frontal cortex samples were taken immediately after death. The tissue was investigated using light and electron microscopy and compared with frontal cortex samples taken from sham-operated controls. Septic pigs had 49.5% more perimicrovessel oedema than sham pigs. However, the tight junctions between cerebral microvessel endothelial cells appeared morphologically intact in both septic and sham pigs. Sepsis also resulted in neuronal injury, disruption of astrocytic end-feet and swollen, rounded erythrocytes. These morphological changes may be sufficient to underlie the clinical features seen in septic encephalopathy.

Porcine hepatic response to sepsis and its amplification by an adrenergic receptor alpha1 agonist and a beta2 antagonist

1. We investigated the effect of adrenergic receptor stimulation or inhibition on the hepatic ultrastructural changes in a porcine faecal peritonitis model of multi-organ failure. We infused either the alpha1 adrenergic receptor agonist methoxamine or the beta2 adrenergic receptor antagonist ICI 118551 during 8 h of the study.2. Anaesthetized pigs (25-30 kg) were divided into four non-septic groups (control, non-septic, non-septic methoxamine and non-septic ICI 118551) and three septic groups (septic, septic methoxamine and septic ICI 118551).3. Changes in hepatic ultrastructure were measured by morphometric analysis. The septic group was significantly worse than all the non-septic groups. Septic methoxamine and septic ICI 118551 were significantly worse than the septic group.4. Septic methoxamine and septic ICI 118551 had a significantly increased perisinusoidal space; septic methoxamine had significant hepatocyte vacuolation.5. Hepatic ultrastructural changes were independent of hepatic blood flow.6. Septic methoxamine had significant myocardial depression.7. The alpha1 adrenergic receptor agonist methoxamine or the beta2 antagonist ICI 118551 both amplified the hepatic injury normally found during sepsis in our porcine model.8. These findings suggest that during sepsis a protective endogenous beta2 adrenergic receptor-mediated anti-inflammatory response is activated via cell membrane transduction to stimulate the trimeric G-protein complex Gs and activate the second cell messenger cAMP.9. In addition, it is likely that alpha1 adrenergic receptor agonists amplify the inflammatory response by stimulating the cell-surface receptor-linked trimeric G-protein complex to activate Gq and the second cell messenger phospholipase C.

Cell surface adrenergic receptor stimulation modifies the endothelial response to SIRS. Systemic Inflammatory Response Syndrome

The complex pathway seen in patients with the systemic inflammatory response syndrome (SIRS) does not readily respond to mediator blockade. All such trials conducted in SIRS patients have shown no benefit in reducing mortality. We have shown experimentally that in sepsis, the administration of beta 2-adrenoceptor agonists reduces hepatic cellular injury, whereas administration of an alpha 1-adrenoceptor agonist increases hepatic cellular injury. Inflammatory mediators can cause a dose-related reversible change in target endothelial cells (ECs). There is a substantial body of literature describing the anti-inflammatory effects of beta 2-adrenoceptor agonists. They reduce both the increased permeability and the production of inflammatory mediators from ECs. Cellular transduction processes are involved when adrenergic receptor agonists modify either the anti-inflammatory or proinflammatory response to sepsis in ECs. Inflammatory mediators and alpha 1-adrenoceptor agonists stimulate their trimeric G protein-linked receptors to produce diacylglycerol (DAG) and increase the intracellular concentration of calcium. DAG is involved in the production of both inflammatory proteins and lipids. In addition, mitogen-activated protein kinase (MAPK) is activated which is also involved in the production of inflammatory proteins and lipids. beta 2-adrenoceptor agonists activate their trimeric G protein-linked receptors to produce the stimulatory G protein (Gs). Gs stimulates adenyl cyclase to form cyclic adenosine monophosphate (cAMP) and activate protein kinase A (PKA). PKA is involved in activating gene transcription agents to produce anti-inflammatory proteins such as interleukin-10. PKA also inhibits phospholipase C and MAPK. Although promising, the use of beta-adrenoceptor agonists or agonists that increase cellular cAMP to activate the cells' endogenous anti-inflammatory pathway requires further study.

Goal-directed therapy with dopexamine, dobutamine, and volume expansion: effects of systemic oxygen transport on hepatic ultrastructure in porcine sepsis

OBJECTIVES

Can the hepatic structural deterioration that occurs during peritonitis be attenuated by increasing cardiac output and oxygen consumption (VO2)? Do the agents used to achieve these increases have any characteristic affects on these hepatic structural changes?

DESIGN

Randomized, prospective, observational animal study.

SETTING

Research laboratory of a university medical school.

SUBJECTS

Twenty-five Middle White adolescent pigs, weighing 25 to 30 kg, divided into five groups.

INTERVENTIONS

A thermodilution flotation catheter was advanced into the pulmonary artery. Additional catheters were inserted into the jugular, portal, and hepatic veins, and into the femoral artery. Ultrasound flow probes were placed around the portal vein and the hepatic artery. A metabolic cart was attached to the ventilator. Baseline measurements were made and cardiac output was increased by > 25% by administering either dobutamine (10 micrograms/min), dopexamine (10 micrograms/kg/min), or colloid. A control group had its cardiac output maintained at its baseline value. Peritonitis was induced in the four groups by contamination with cecal content and maintained for 6 hrs. Hepatic tissue was then removed for ultrastructural analysis and the animals were killed.

MEASUREMENTS AND MAIN RESULTS

Before infection, cardiac output, VO2, and hepatic blood flow were increased in the three treatment groups. In the dobutamine and dopexamine groups, oxygen delivery increased, but decreased in the volume group. Mean arterial pressure increased in the dobutamine and dopexamine groups, but in the volume group, mean arterial pressure was maintained. Six hours after infection, cardiac output and VO2 had further increased in the dobutamine and volume groups, but both variables had decreased in the dopexamine group. After infection in the control group, cardiac output had decreased, although oxygen delivery and VO2 increased. There were no significant differences between hepatic hemodynamic or oxygen transport variables in any of the groups during the infection period. Hepatic ultrastructure was well maintained in the dopexamine group, while considerable deterioration was seen in the volume and control groups. In the dobutamine group, hepatic deterioration was greater than in the other three groups.

CONCLUSIONS

Increasing cardiac output and VO2 before and during infection was only protective when dopexamine was administered. Dobutamine infusion was associated with greater hepatic deterioration than that effect seen in either the control or volume groups.

Comparison of proximal isovelocity surface area method with pressure half-time and planimetry in evaluation of mitral stenosis

OBJECTIVES

This study sought to 1) compare the accuracy of the proximal isovelocity surface area (PISA) and Doppler pressure half-time methods and planimetry for echocardiographic estimation of mitral valve area; 2) evaluate the effect of atrial fibrillation on the accuracy of the PISA method; and 3) assess factors used to correct PISA area estimates for leaflet angulation.

BACKGROUND

Despite recognized limitations of traditional echocardiographic methods for estimating mitral valve area, there has been no systematic comparison with the PISA method in a single cohort.

METHODS

Area estimates were obtained in patients with mitral stenosis by the Gorlin hydraulic formula, PISA and pressure half-time method in 48 patients and by planimetry in 36. Two different factors were used to correct PISA estimates for leaflet angle (theta): 1) plane-angle factor (theta/180 [theta in degrees]); and 2) solid-angle factor [1-cos(theta/2)].

RESULTS

After exclusion of patients with significant mitral regurgitation, the correlation between Gorlin and PISA areas (0.88) was significantly greater (p < 0.04) than that between Gorlin and pressure half-time (0.78) or Gorlin and planimetry (0.72). The correlation between Gorlin and PISA area estimates was lower in atrial fibrillation than sinus rhythm (0.69 vs. 0.93), but the standard error of the estimate was only slightly greater (0.24 vs. 0.19 cm2). The average ratio of the solid- to the plane-angle correction factors was approximately equal to previously reported values of the orifice contraction coefficient for tapering stenosis.

CONCLUSIONS

1) The accuracy of PISA area estimates in mitral stenosis is at least comparable to those of planimetry and pressure half-time. 2) Reasonable accuracy of the PISA method is possible in irregular rhythms. 3) A simple leaflet angle correction factor, theta/180 (theta in degrees), yields the physical orifice area because it overestimates the vena contracta area by a factor approximately equal to the contraction coefficient for a tapering stenosis.

Dopexamine hydrochloride maintains portal blood flow and attenuates hepatic ultrastructural changes in a porcine peritonitis model of multiple system organ failure

Fifteen anesthetised pigs (25-30 kg) were divided into three equal groups, sham, dopexamine (D) (10 micrograms/kg/min), and placebo (P). Sepsis was induced by fecal peritonitis in the D and P groups and colloid was infused to try to maintain mean arterial blood pressure (MABP) at a constant value and the hemodynamics measured at baseline and hourly for 8 hr. There was an initial increase in MABP and systemic vascular resistance (SVR) in the P group but not the dopexamine (D) group. Cardiac output (CO) in the P group showed a small decline but increased in the D group. The portal blood flow (PVF) in the P group fell with MABP but increased in the D group as MABP fell. The sham group showed normal ultrastructure and cellular integrity. Occlusion of the hepatic sinusoids was similar in the D and P groups. There was a greater area of Kupffer cells and endothelial cells in the P group, suggesting a greater inflammatory reaction than was found in the D group. Ultrastructure and mitochondrial integrity was better maintained in the D group. Dopexamine hydrochloride infusion maintained CO, increased PVF, and attenuated hepatic ultrastructural changes compared to placebo in a porcine fecal peritonitis model of multisystem organ failure.

A narrow range, medium molecular weight pentastarch reduces structural organ damage in a hyperdynamic porcine model of sepsis

OBJECTIVE

to compare diafiltered 6% pentastarch (Pentafraction--PDP, MWn 120,000 and MWw 280,000) and native pentastarch (Pentaspan--PSP, MWn 63,000 and MWw 264,000 dalton) in a porcine model of faecal peritonitis.

DESIGN

Randomised prospective study in 12 adolescent pigs.

INTERVENTIONS

Prior to infection the study solution was infused to increase Qt by 25%. Thereafter adjustments in infusion rate were made (up to 1 l/h) in an attempt to maintain Qt at 25% above baseline values.

MEASUREMENTS AND RESULTS

Animals were sacrificed at 8 h. Tissue was excised from the right lobe of liver and from the right lung and fixed for later electron microscopy and digital morphometric analysis. Patent sinusoidal lumen was significantly greater in group PDP compared to PSP (11.3% +/- 2.3% of liver tissue versus 4.8% +/- 1.1%, p < 0.05) and this was accounted for by a significantly lower proportion of sinusoidal lumen occluded with white cells (2.1% +/- 0.6% versus 6.6% +/- 1.9%, p < 0.05). Similarly, patent capillary represented a significantly higher proportion of lung tissue for group PDP versus PSP (26.2% +/- 1.9% versus 18.5% +/- 2.7%, p < 0.05). The arithmetic mean alveolar capillary barrier thickness was significantly greater in group PSP than in group PDP (4.3 +/- 0.3 microns versus 2.5 +/- 0.3 microns, p < 0.01).

CONCLUSIONS

The molecular weight profile of Pentafraction was associated with less structural organ damage including less tissue oedema and less white cell occlusion.

Validation of bedside measurements of absolute human renal blood flow by a continuous thermodilution technique

BACKGROUND AND METHODS

There is a clinical need for a system that would allow rapid assessment of renal blood flow in patients with oliguric circulatory shock. A local, continuous thermodilution technique for the measurement of renal venous blood flow, using readily available equipment, was developed. To test the hypothesis that this system would allow measurement of renal blood flow in clinical situations, we compared simultaneous measurements made by the continuous thermodilution technique with measurements of: a) absolute flow measured by volumetric collection in an in vitro flow model; b) renal arterial blood flow measured by electromagnetic flow probe under changing hemodynamic conditions in nine pigs; and c) calculated renal blood flow derived from a clearance technique in 16 patients after cardiac catheterization. The technique utilizes a short-duration, constant infusion of room temperature normal saline into the renal vein via a retrograde thermodilution catheter, with measurement of flow at a thermistor 1 cm back from the tip of the catheter.

RESULTS

The method measured absolute blood flow in an in vitro model, with a correlation coefficient of .99 over blood flows ranging from 55 to 885 mL/min (r2 = .98). There was a .92 correlation coefficient with renal arterial blood flow measured by electromagnetic flow probe in a pig model (r2 = .85), and a .8 correlation with simultaneous measurement of renal blood flow by corrected iodohippurate clearance in humans (r2 = .64). Compared with electromagnetic flow probe measurements, a single measurement by the thermodilution technique would be accurate to within 80 mL/min in 95% of cases. Variability between individual measurements, expressed as the mean of the coefficient of variance for each patient, was 5.5 +/- 3.7%.

CONCLUSIONS

This technique is simple to use, requires only venous cannulation and injection of normal saline, and allows rapidly repeatable, immediately available measurements of renal blood flow in a wide range of clinical circumstances, including severe renal impairment or anuria.

The effects of dobutamine, dopexamine and fluid on hepatic histological responses to porcine faecal peritonitis

We studied the effects of two catecholamines with differing receptor profiles on hepatic blood flow and hepatic structure in a porcine model of faecal peritonitis. We treated animals with dopexamine (group Dp) or dobutamine (group Db) and fluid, or fluid alone as a control, to achieve a 25% increase in Qt from baseline values. After the induction of faecal peritonitis the increased Qt was maintained throughout the 8 h study period by adjustment of the fluid infusion rate. The dose of catecholamines remained constant. Hepatic blood flow was correspondingly maintained at above baseline values throughout the study. Post-mortem liver biopsy specimens were analysed from experimental animals and 5 sham animals who had not been instrumented or infected. In experimental animals there was a reduction in sinusoidal patency between sham and group Dp (76% of total sinusoid vs 51%, p less than 0.05) and group Dp and control (51% vs 33%, p less than 0.05) or groups Dp and Db (51% vs 34%, p less than 0.05) animals. This was accounted for by an increase in sinusoidal leukocytes and endothelial swelling. In addition to the changes noted above there was marked hepatocellular destruction in group Db. We conclude that maintenance of organ blood flow does not guarantee structural integrity in the sepsis syndrome and hepatocellular damage was greater in group Db than group Dp or control.

Advantages of a narrow-range, medium molecular weight hydroxyethyl starch for volume maintenance in a porcine model of fecal peritonitis

OBJECTIVE

To compare the effectiveness of two hydroxyethyl starch solutions of different molecular weight ranges for volume maintenance in a porcine model of fecal peritonitis.

DESIGN

Randomized prospective trial.

SETTING

Laboratory investigation.

SUBJECTS

Adolescent female pigs weighing approximately 30 kg.

INTERVENTIONS

We compared diafiltered 6% pentastarch with 6% high molecular weight hetastarch for volume maintenance in a porcine model of fecal peritonitis. The number average molecular weight of pentastarch is higher than hetastarch, although the weight average molecular weight is lower, i.e., a narrow range of medium weight molecules. The infusion rate of each agent was adjusted to maintain baseline arterial Hct for less than or equal to 7 hr after instrumentation and induction of fecal peritonitis.

MAIN OUTCOME MEASUREMENTS

The volume of fluid required to maintain arterial Hct was compared along with comparisons of hemodynamic and histologic responses associated with the two agents.

RESULTS

Significantly less pentastarch was required to prevent hemoconcentration than hetastarch (109 +/- 22.8 vs. 150 +/- 10.3 mL/kg; p less than .05) while hemodynamics, colloid osmotic pressure, and oxygen transport responses were similar. Capillary patency was greater (21.99 +/- 3.68 vs. 10.09 +/- 1.17%; p less than .05) and mean alveolar capillary barrier thickness was less (2.36 +/- 0.13 vs. 3.06 +/- 0.17 microns; p less than .05) with pentastarch than with hetastarch, as judged by electron microscopy.

CONCLUSIONS

These data suggest that pentastarch is better retained in the circulation in capillary leak syndromes compared with hetastarch.

Pretreatment with pentoxifylline improves the hemodynamic and histologic changes and decreases neutrophil adhesiveness in a pig fecal peritonitis model

We investigated pentoxifylline (PTF) as a pretreatment of septic syndrome in pigs with fecal peritonitis. In the untreated group there was a progressive decrease in mean arterial pressure (MAP), cardiac output, mean pulmonary artery wedge pressure (WP), and a progressive rise in mean pulmonary artery pressure (MPAP), pulmonary vascular resistance (PVR), systemic vascular resistance (SVR), heart rate (HR), and core temperature (T). In those pigs given PTF there was a significantly smaller increase in SVR throughout and in PVR after 270 min. No significant differences were seen in MAP, MPAP, WP, HR, and T. Neutrophil adhesiveness did not change in the untreated group. However, it decreased markedly with PTF, both before and after peritonitis induction. Electron microscopy of the lungs, liver, and spleen in the test group showed severe damage, with endothelial disruption, capillary or sinusoidal occlusion, leukostasis, and neutrophil degranulation. Pretreatment with PTF attenuated these changes.

Pentoxifylline reduces pulmonary leucostasis and improves capillary patency in a rabbit peritonitis model

This study examines the changes in pulmonary leucostasis and capillary ultrastructure in 18 rabbits divided into three groups. Those in the first group were sham operated, and those in the second and third groups underwent peritonitis induction; those in the latter group were treated with pentoxifylline (PTF). White blood cells (WBC) were counted, and tissue area, total capillary area, and capillary patency were measured from electron micrographs of lung tissue. Pulmonary WBCs were 1.2 per unit field in the sham group, 9.7 in the test group (P less than 0.001 compared with sham), and 2.5 in the PTF group (P less than 0.001 compared with sham). Capillary patency was 53 +/- 5% in the sham group, 12 +/- 4% (P less than 0.001 compared with sham) in the test group, and 24 +/- 2% (P less than 0.001 compared with sham) in the PTF group. Pentoxifylline treatment attenuates pulmonary leucostasis, pulmonary capillary occlusion, and endothelial and epithelial damage associated with peritonitis in rabbits. This study shows that PTF warrants investigation into its potential protective effects on the lungs in clinical sepsis.

Multi-organ damage resulting from experimental faecal peritonitis

1. Using specific-pathogen-free New Zealand White rabbits, we have compared the effects of faecal peritonitis over a period of 5 h in eight test animals with eight controls in which a sham operation was performed. 2. There was morphological damage to lungs, liver and spleen of test animals. Lung capillaries and sinusoids of the liver showed occlusion by cell debris and leucocytes, with endothelial damage. The lungs also showed alveolar epithelial disruption, basement membrane exposure and type II pneumocytes lacking lamellar bodies. In the liver there was fibrin deposition and swollen Kupffer cells. The spleen showed degranulating neutrophils, fibrin deposits, platelet aggregates and activated macrophages, with no damage to the endothelium. 3. There was no morphological damage to the kidney or heart of test animals or to any organs of sham-operated animals. 4. There were mixed anaerobes and aerobes in faecal material used to induce peritonitis. Cultures of liver, spleen and kidney isolated four different types of micro-organisms. Blood cultures showed two types of micro-organisms. Cultures of lung and heart showed one type of micro-organism. 5. The presence of micro-organisms in an organ could not be correlated with the degree of histological damage to that organ. 6. In test animals an early significant reduction in circulating leucocytes and platelets was sustained for the duration of the experiment with significant diffuse intravascular coagulation. 7. There was no change in test animal neutrophil adhesiveness until 120 min, when significant reduction was observed. 8. Serum phospholipase A2 (EC 3.1.1.4) activity in the test group showed a threefold increase at 300 min.

A phospholipase inhibitor modifies the pulmonary damage associated with peritonitis in rabbits

Peritonitis has been produced in rabbits by the spreading of 5 ml of caecal contents throughout the peritoneal cavity. After sacrifice at 5 h, electron microscopy revealed a increase of 600% in PMN and 1200% in lymphocytes in the pulmonary capillaries of the test animals when compared to the sham operated group. The pulmonary capillaries in the test group showed a 27% reduction in their luminal area, which was associated with a 73% reduction in their patency due to occlusion by WBC and cell debris. In addition there was endothelial and epithelial disruption with basement membrane exposure. The PMN were degranulated and adherent to the pulmonary endothelium. Pretreatment with the phospholipase inhibitor, mepacrine, significantly attenuated these responses, so that there was only an increase of 200% in PMN and 450% in lymphocytes in the lungs with no evidence of degranulation or adhesion to the pulmonary endothelium. Furthermore there was no change in capillary luminal area when compared to the sham operated group. In addition there was only slight damage to the endothelium and epithelium with no exposure of the basement membrane. Peripheral WBC in both the test and mepacrine groups showed a similar 62% and 75% reduction after 5 h when compared to baseline values. The sham group did not show this change. These results suggest that phospholipase inhibition plays an important role in attenuating the pulmonary response to faecal peritonitis and may be of potential benefit in treating clinical septicaemia.

Abolition, by dopamine blockade, of the natriuretic response produced by lower-body positive pressure

1. In a preliminary study, a positive pressure of 25 mmHg applied to the lower body raised right atrial pressure by a mean of 7 mmHg. 2. Sustained application of lower-body positive pressure (LBPP) in six normal adult males increased sodium excretion ([Na]V) from a control level of 126.5 +/- 10 mumol/min to 213 +/- 21 mumol/min (P = 0.003) and fractional sodium excretion (EfNa) from 0.7 +/- 0.1 to 1.2 +/- 0.1 (P = 0.001). 3. Urine flow (UF) increased from 0.85 +/- 0.07 ml/min to 4.1 +/- 0.8 ml/min (P = 0.002), osmolar clearance (Cosm) from 2.6 +/- 0.13 ml/min to 4.2 +/- 0.4 ml/min (P = 0.003) and free water clearance (CH2O) from -1.75 +/- 0.1 ml/min to -0.1 +/- 0.01 ml/min (P = 0.001). Creatinine clearance (Ccr) showed no significant change. 4. After dopamine blockade with domperidone, LBPP did not cause a rise in [Na]V or EfNa. However, urine flow, Cosm. and CH2O remained significantly above control values, implying persistent suppression of antidiuretic hormone. 5. Dopamine blockade without positive pressure did not affect basal sodium excretion.