Rectus Sheath Block Improves Patient Recovery Following Open Aortic Surgery

BACKGROUND

Postoperative pain management remains a barrier to recovery following aortic surgery. Although epidural catheters help in adjunctive pain management, less is known about the use of rectus sheath blocks. We compared patient recovery following open abdominal aortic surgery (OAS) with and without adjunctive rectus block.

METHODS

Adult patients undergoing open abdominal aortic aneurysm repair and aortobifemoral or aortoiliac bypass for occlusive disease were identified and stratified by use of general anesthesia alone (GA) versus adjunctive use of a rectus sheath block (GA + RB). A small number of patients with GA and concomitant epidural analgesia, along with patients that had retroperitoneal repairs, were not included in further analysis. Outcomes included time to extubation, intraoperative and postoperative morphine milligram equivalents (MME) utilization, length of stay, discharge MME, and postoperative complications. Categorial data were compared with Person Chi-Square tests or Fisher's exact tests. Continuous data were tested with independent t-tests or Mann-Whitney U-tests.

RESULTS

From January 2017 to April 2022, there were 106 patients who underwent open aortic surgery, 55 patients with GA alone, 39 with GA + RB, and 12 patients who had a GA with concomitant epidural analgesia. Between GA and GA + RB, patients were comparable in both groups in terms of age, BMI (body mass index), smoking history, hypertension, diabetes, CAD (coronary artery disease), COPD (chronic obstructive pulmonary disease), and ASA (American Society of Anesthesiologists) class and prior opioid use. Patients with GA + RB were more likely to have scheduled elective procedures (80% GA cohort vs. 94.9% RB, P = 0.040), and a lower incidence of retroperitoneal exposure (14.5% GA cohort vs. 0% RB, P = 0.019). Patients with GA + RB had shorter time to extubation than GA (84.6% < 12 hr vs. 44.4%, P < 0.001), greater rate of procedural ketamine usage (GA + RB: 61.5% vs. GA: 40.0%, P = 0.049), lower MME at first postoperative day (median MME GA + RB: 25.0 vs. GA: 67.5, P = 0.002), lower discharge MME (median MME GA + RB: 142.5 vs. GA: 225.0, P = 0.036), and overall shorter length of stay (median stay GA + RB: 5 vs. GA: 6 days, P = 0.006). Postoperative complications were similar between groups. Similar findings were found in the comparison between elective-only GA and GA + RB patients and after exclusion of patients who only had a single shot of regional anesthesia.

CONCLUSIONS

Patients that receive adjunctive rectus sheath blocks for pain control following OAS utilize fewer opioid medications during hospital stay and at discharge. Rectus sheath blocks represent an alternative option to other periprocedural analgesia following open aortic surgery.

Use of the right retroperitoneum as an alternative approach to the abdominal aorta

OBJECTIVE

The left retroperitoneal approach to the aorta is a well-established technique for aortic exposure. The right retroperitoneal approach to the aorta is performed less commonly, and the outcomes remain unknown. This study aimed to evaluate the outcomes of right retroperitoneal aortic-based procedures and to determine its utility in aortic reconstruction when faced with hostile anatomy or infection in the abdomen or left flank.

METHODS

A retrospective query of a vascular surgery database from a tertiary referral center was performed for all retroperitoneal aortic procedures. Individual patient charts were reviewed, and data were collected. Demographics, indications, intraoperative details, and outcomes were tabulated.

RESULTS

From 1984 through 2020, there have been 7454 open aortic procedures; 6076 were retroperitoneal-based, and 219 of which were performed from the right retroperitoneal approach (Rrp). Aneurysmal disease was the most common indication (48.9%), and graft occlusion was the most common postoperative complication (11.4%). The average aneurysm size was 5.5 cm, and the most common reconstruction was with a bifurcated graft (77.6%). Average intraoperative blood loss was 923.8 mL (range, 50-6800 mL; median, 600 mL). Perioperative complications occurred in 56 patients (25.6%) for a total of 70 complications. Perioperative mortality occurred in two patients (0.91%). The 219 patients treated with Rrp required 66 subsequent procedures in 31 patients. These included 29 extra-anatomic bypasses, 19 thrombectomies/embolectomies, 10 bypass revisions, 5 infected graft excisions, and 3 aneurysm revisions. Eight Rrp eventually underwent a left retroperitoneal approach for aortic reconstruction. Fourteen patients with a left-sided aortic procedure required a Rrp.

CONCLUSIONS

The right retroperitoneal approach to the aorta is a useful technique in the setting of prior surgery, anatomic abnormality, or infection that complicates the use of other more frequently employed approaches. This review demonstrates comparable outcomes and the technical feasibility of this approach. The right retroperitoneal approach to aortic surgery should be considered a viable alternative to left retroperitoneal and transperitoneal access in patients with complex anatomy or prohibitive pathology for more traditional exposure.

Female sex is associated with worse outcomes following complex fenestrated or branched endovascular aortic repair

INTRODUCTION

Sex-related discrepancies after standard endovascular aneurysm repair (EVAR) are noted to disproportionally affect females. A growing body of literature suggests similar disparities may extend to complex fenestrated or branched endovascular aneurysm repair (FBEVAR). However, recent examination of complex FBEVAR by a consortium of high-volume centers noted equivalent mortality among sexes. Whether similar results extend to non-trial data is unknown.

METHODS

We examined all juxta-renal through type IV thoraco-abdominal aneurysms (sealing zones 6-8) who underwent elective FBEVAR within the Vascular Quality Initiative (VQI) database from January 2012 to December 2020. Urgent, symptomatic, ruptured, and staged cases were excluded, as were parallel stent grafts. Demographics, comorbid conditions, and technical factors were compared between sexes. Univariate analysis with Wilcoxon ranked sum tests and Chi-square tests of proportion were performed, followed by multivariate logistic regression for failure of target vessel technical success, reintervention, complications, and in-hospital mortality.

RESULTS

Our analysis included 1521 patients, 1180 males (77.6%) and 341 females (22.4%). There were noted differences in pre-operative demographics, medical optimization, and technical aspects of the procedure. However, no difference was noted in proximal or distal sealing stents, number of fenestrations, or immediate endoleaks. On multi variate logistic regression, female sex was an independent predictor of failure of target vessel technical success (OR 3.339, 95% CI: 2.173-5.132, p<.001), reintervention (OR 2.192, 95% CI: 1.304-3.683, p=.003), complications (OR 1.747, 95% CI: 1.282-2.381, p<.001), and in-hospital mortality (OR 2.836, 95% CI: 1.510-5.328, p=.001).

CONCLUSION

Females suffer worse outcomes after FBEVAR despite similar extent of disease, number of fenestrations, and incidence of immediate endoleak. Notable discrepancies were higher rates of COPD and lower rates of pre-operative aspirin, statin, and beta blocker therapy in females. Controlling for pre-operative demographics, female sex remained an independent predictor of worse outcomes. These discrepancies warrant further examination and should impact case planning for female patients undergoing complex aortic aneurysm repair.

Intraoperative electroencephalographic changes during transcarotid artery revascularization are more frequent than previously reported

OBJECTIVE

Up to 14% of patients undergoing carotid endarterectomy with continuous electroencephalographic (EEG) neuromonitoring will require shunt placement because of EEG changes. However, the initial studies of transcarotid artery revascularization (TCAR) found only one patient with temporary EEG changes. We report our experience with intraoperative EEG monitoring during TCAR.

METHODS

We conducted a retrospective review of patients who underwent TCAR at two urban hospitals within an integrated healthcare network from May 2017 to January 2020. The data included demographic information, patient comorbidities, symptom status, previous carotid interventions, anatomic details, contralateral disease, intraoperative vital signs and EEG changes, and postoperative major adverse events (transient ischemic attack, stroke, myocardial infarction [MI], and death) both initially and at 30 days postoperatively. The Fisher exact test was used for categorical data and the Wilcoxon rank sum test for continuous data.

RESULTS

A total of 89 patients underwent TCAR during the study period, of whom 71 (79.8%) received intraoperative EEG neuromonitoring. Of the 89 patients, 70.8% were men and 29.2% were women. The median age was 75 years (IQR, 68-82.5 years). Symptomatic patients accounted for 41.6% of the cohort. Of the 71 patients who received continuous neuromonitoring, 9 experienced EEG changes during TCAR (12.7%). The changes resolved in seven patients with pressure augmentation in three and switching to a low flow toggle in three. One patient who had sustained EEG changes had a new postoperative neurologic deficit. The median carotid stenosis percentage on preoperative computed tomography angiography was lower for patients with EEG changes than for those without (67% vs 80%; P = .01). No correlation was found between symptom status or 30-day stroke in patients with and without EEG changes (P = .49 and P = .24, respectively). Overall, three postoperative strokes, two postoperative deaths, and one MI occurred, for a composite 30-day stroke, death, and MI rate of 6.7%.

CONCLUSIONS

Changes in continuous EEG monitoring were more frequent in our study than previously reported. Less severe carotid stenosis might be associated with a greater incidence of EEG changes. Limited data are available on the prognostic ability of EEG to detect clinically relevant changes during TCAR, and further studies are warranted.

Safety and outcomes of simultaneous vasospasm and endovascular aneurysm treatment (SVAT) in subarachnoid hemorrhage

Background

Simultaneous vasospasm and endovascular aneurysm treatment (SVAT) has been shown to be effective with good clinical outcomes in small series, but these studies have not examined predictive factors for clinical outcome after treatment.

Objective

To identify the safety and efficacy of SVAT in a large multicenter patient cohort and evaluate prognostic markers of clinical outcome following SVAT.

Methods

This study retrospectively enrolled 50 consecutive patients undergoing SVAT at 11 different centers. We analyzed Hunt and Hess and Fisher grades, aneurysm location, angiographic vasospasm grade, Glasgow Outcome Scale (GOS) at discharge, and 90-day modified Rankin Scale (mRS) scores.

Results

A total of 50 patients undergoing SVAT between the years 2003 and 2009 were identified. Patients presented, on average, 6.48±4.45 days after subarachnoid hemorrhage. Hunt and Hess and Fisher grades were 1 (n=7), 2 (n=12), 3 (n=14), 4 (n=15), 5 (n=2), and 3 and 4 (n=33), respectively. Aneurysm location was distributed as follows: anterior (n=32), posterior (n=16), anterior and posterior (n=2). Patients with good clinical condition (Hunt and Hess score 1–3) had significantly higher odds of surviving (OR=17.5, 95% CI 1.9 to 161.5), favorable GOS (OR=4.2, 95% CI 1.2 to 14.8), and favorable 90-day mRS (OR=4.2, 95% CI 1.2 to 14.8).

Conclusions

SVAT is safe, with the majority of patients achieving good clinical outcome. Patients with lower Hunt and Hess grades have higher odds of surviving and favorable clinical prognosis.

General Surgery Residents can Be a Reliable Resource in the Evaluation of Residency Applications

OBJECTIVE

Surgical residents' ability to screen general surgery (GS) applicants has not been previously investigated. The objective of this study was to compare surgical residents' evaluation of Electronic Residency Application Service (ERAS) applicants to that of faculty using a standardized assessment instrument.

DESIGN

A prospective analysis of ERAS applications using a standardized assessment tool.

SETTING

A university-affiliated, academic, county GS residency program.

PARTICIPANTS

Before the interview day, 51 ERAS (2013-2014) applications were reviewed by 10 different assessors (6 GS faculty, including the program director, and 4 GS residents), who evaluated applicants on 10 characteristics (subjective and objective) using a 5-point Likert scale, a total score, and a Global Rating Scale that ranked candidates into deciles.

RESULTS

There were a total of 510 assessments. In 8 of 10 individual domains the interrater reliability (IRR) between residents and faculty was good. The IRRs of the total score and global score were excellent. The Spearman ρ between the total score and final rank list were similar for faculty (-0.558) and residents (-0.592).

CONCLUSIONS

The excellent IRR score between the total and global scores of faculty and residents demonstrates the reliability of GS residents in evaluating ERAS applications. The low correlations between the total score and final rank are consistent with those in previous studies, in which the interview has been demonstrated to be the most important factor in determining final selection.

Predictors of Mortality in Patients with Penetrating Inferior Vena Cava Injuries Surviving to the Operating Room

Inferior vena cava (IVC) injuries are associated with significant morbidity and mortality. To identify clinical factors associated with mortality in patients undergoing operative intervention for penetrating IVC injuries, a retrospective review of 98 patients was performed, excluding blunt injuries (n = 20) and deaths before surgery (n = 16). The overall mortality was 58 per cent. Nonsurvivors more commonly presented with hypotension (50% vs 23%, P = 0.03) and underwent resuscitative thoracotomy more frequently (42% vs 4%, P = 0.01). Retrohepatic injuries were more common among nonsurvivors ( P = 0.04). There was no difference in the use of ligation (7% vs 17%, P = 0.29) or the massive transfusion protocol (35% vs 25%, P = 0.41). On multivariate analysis, after controlling for mechanism of injury, admission hypotension, Glasgow Coma Scale score, preoperative cumulative fluids, resuscitative thoracotomy, absence of spontaneous tamponade, and location of IVC injury, the only independent predictor of mortality was the absence of spontaneous tamponade at the time of laparotomy (odds ratio = 5.4, 95% confidence interval: 1.11–25.95; P = 0.04). Penetrating IVC injuries continue to be associated with a high mortality, particularly among patients with free intraabdominal hemorrhage at laparotomy. Large multicenter studies are required to define the optimal resuscitative and operative management techniques in these severely injured patients.

Predictors of Mortality in Patients with Penetrating Inferior Vena Cava Injuries Surviving to the Operating Room

Inferior vena cava (IVC) injuries are associated with significant morbidity and mortality. To identify clinical factors associated with mortality in patients undergoing operative intervention for penetrating IVC injuries, a retrospective review of 98 patients was performed, excluding blunt injuries (n = 20) and deaths before surgery (n = 16). The overall mortality was 58 per cent. Nonsurvivors more commonly presented with hypotension (50% vs 23%, P = 0.03) and underwent resuscitative thoracotomy more frequently (42% vs 4%, P = 0.01). Retrohepatic injuries were more common among nonsurvivors (P = 0.04). There was no difference in the use of ligation (7% vs 17%, P = 0.29) or the massive transfusion protocol (35% vs 25%, P = 0.41). On multivariate analysis, after controlling for mechanism of injury, admission hypotension, Glasgow Coma Scale score , preoperative cumulative fluids, resuscitative thoracotomy , absence of spontaneous tamponade, and location of IVC injury, the only independent predictor of mortality was the absence of spontaneous tamponade at the time of laparotomy (odds ratio = 5.4, 95% confidence interval: 1.11-25.95; P = 0.04). Penetrating IVC injuries continue to be associated with a high mortality, particularly among patients with free intraabdominal hemorrhage at laparotomy. Large multicenter studies are required to define the optimal resuscitative and operative management techniques in these severely injured patients.

The effect of residents as teaching assistants on operative time in laparoscopic cholecystectomy

BACKGROUND

We examined the effect of primary surgeon (PS) and teaching assistant (TA) seniority on operative time and outcomes for residents performing laparoscopic cholecystectomy (LC).

METHODS

This was a retrospective analysis of urgent LC at a county teaching hospital. Relevant data included postgraduate year (PGY) of the PS and TA and markers of disease severity. Primary outcome was operative time. Secondary outcomes were conversion to open cholecystectomy and complications.

RESULTS

There were 1,202 LCs; 415 included an intraoperative cholangiogram. On multivariable analysis, every PGY increase of PS decreased operative time by 3.2 minutes (P = .02). For every PGY increase of TA, operative time decreased 10.8 minutes (P < .001). Acute or gangrenous pathology increased conversion to open surgery (P < .001). Seniority of PS and TA was not associated with increases in conversion or complication rates.

CONCLUSIONS

Residents' operative time improves as experience with LC increases. These improvements become more profound after adjusting for the seniority of the TA.

Increased use of brachiocephalic arteriovenous fistulas improves functional primary patency

OBJECTIVE

As vascular surgeons strive to meet the Fistula First Initiative, some authors have observed a decrease in arteriovenous fistula (AVF) maturation rates in association with an increase in AVF creation. In May 2012, we adopted a practice change in an attempt to maintain the same high level of AVF creation while leading to a decrease in fistula failures.

METHODS

A retrospective study was conducted of all dialysis access procedures performed by a single vascular surgeon before (period 1; before May 1, 2012) and after (period 2; after May 1, 2012) the change in practice pattern. The adopted change included favoring the brachiocephalic location unless the patient was an ideal anatomic candidate for a radiocephalic AVF, creating a larger and standardized arteriotomy, and using a large venous footplate whenever possible. The main outcome measure was primary functional patency at 1 year. Secondary outcome measures included primary patency at 1 year, time to maturation, type of fistula created, steal syndrome, and tunneled hemodialysis catheter infections.

RESULTS

Of 213 vascular access procedures performed, 191 (90%) were AVFs. There was no difference in use of AVFs between period 1 (93% AVFs) and period 2 (88% AVFs; P = .2). Use of brachiocephalic AVFs increased from 38% in period 1 to 56% in period 2 (P = .01), with a corresponding trend toward a decrease in radiocephalic AVFs in period 2 (36% in period 1 to 27% in period 2; P = .2). Primary functional patency at 1 year was 47% in period 1 and 63% in period 2 (P = .03). Primary patency at 1 year was 51% in period 1 and 70% in period 2 (P = .001). Time to reach functional maturation was decreased in period 2 (median, 76 vs 82.5 days; P = .046). There was no difference in steal syndrome (P = 1.0), and the incidence of hemodialysis catheter infections was lower in period 2 (0 vs 7 [7%]; P = .006).

CONCLUSIONS

Increasing brachiocephalic AVF creation and reducing our reliance on radiocephalic AVFs resulted in a significant increase in primary functional patency at 1 year. This was achieved while maintaining the same high percentage of fistulas, a lower rate of central catheter infections, and the same low incidence of steal syndrome.

The impact of a massive transfusion protocol on outcomes among patients with abdominal aortic injuries

BACKGROUND

Injuries of the abdominal aorta are uncommon and associated with a high mortality. The purpose of this study was to examine the impact of an institutional massive transfusion protocol (MTP) on outcomes in patients with injuries of the abdominal aorta.

METHODS

A 12.5-year retrospective analysis of a Level 1 trauma center database to identify patients with abdominal aortic injuries was conducted. Demographics, associated injuries and severity, operative procedures, resuscitation requirements, and outcomes were compared among patients before and after implementation of an MTP.

RESULTS

Of the 46 patients with abdominal aortic injuries, 29 (63%) were in the pre-MTP group and 17 (37%) were in the post-MTP group. The mean age of the entire cohort was 32 ± 17 years and the two most common mechanisms of injury were gunshot wounds (63%) followed by motor vehicle collisions (24%). Thirteen patients (28%) underwent an emergency department thoracotomy and 11 patients (24%) sustained concomitant inferior vena cava injuries. There was a significant reduction in the volume of pre- and intraoperative crystalloids administered between the pre- and post-MTP groups. Intraoperatively, the use of tranexamic acid was increased in the post-MTP group (P < 0.001). A statistically significant difference in achievement of a low packed red blood cells to fresh frozen plasma ratio was observed for the post- versus the pre-MTP group (88% vs. 30%, P = 0.015). Overall survival was improved among post- versus pre-MTP patients (47% vs. 14%, P = 0.03).

CONCLUSIONS

Abdominal aortic injuries continue to represent a challenge and remain associated with a high mortality. Modern improvements in damage control resuscitation techniques including implementation of an institutional MTP may improve outcomes in patients with these injuries.

Strategies and outcomes for coiling very small aneurysms

OBJECTIVE

Coiling of aneurysms 3 mm in diameter or less has been associated with a relatively high rate of complications, including iatrogenic rupture. The present study aimed to determine the clinical outcome of our technique for coiling small aneurysms.

METHODS

A retrospective chart review was performed of prospectively collected data for all patients who had endovascular coiling of an aneurysm 3 mm in diameter or less between 2003 and 2008. Follow-up imaging with magnetic resonance or catheter angiography was performed at varying intervals after coiling, ranging from 1 to 6 years after the procedure. Angiographic results were assessed using the Raymond-Roy (RR) grading system. Clinical outcomes during the same period were measured using the modified Rankin Scale.

RESULTS

Between March 2003 and April 2008, 20 patients underwent coil embolization of an aneurysm 3 mm or smaller--17 ruptured and 3 unruptured. After the procedure, 10 aneurysms were completely occluded (RR 1), 7 had residual filling of the neck (RR 2), and 3 had residual filling of the fundus (RR 3). There were no iatrogenic ruptures. Stent assistance was used in three cases. Balloon assistance was not used. Two patients were retreated, but no aneurysm reruptured. Clinical outcomes were as expected on the basis of the presenting Hunt & Hess grade. One patient with a ruptured aneurysm died from complications related to severe vasospasm.

CONCLUSION

Aneurysms 3 mm in diameter or smaller can be coiled safely with the use of both bare platinum and hydrogel-coated coils. In most cases, coiling of small aneurysms can be performed without the use of adjunctive devices such as balloons or stents.

The effectiveness of microballoon angioplasty in treating middle cerebral artery occlusion beyond the bifurcation

BACKGROUND AND PURPOSE

PTA effectively treats vasospasm and arterial disease in peripheral, coronary, and large proximal cerebral vessels but rarely reaches small vessels like the distal MCA beyond the bifurcation. Our purpose was to evaluate the safety and efficacy of PTA for distal MCA occlusions in acute ischemic stroke.

MATERIALS AND METHODS

Seven patients had strokes in branches of their MCAs. Following diagnostic angiography, all received microballoon angioplasty and various combinations of IA alteplase (rtPA), abciximab, and/or nitroglycerin. Two also underwent stent placement. Comprehensive retrospective review of the patients' records was performed. Patients' NIHSS scores were reassessed before discharge. Recanalization was evaluated by angiography after treatment and at follow-up.

RESULTS

PTA was successfully performed in 7 patients without treatment-associated intracerebral hemorrhage. Two patients received distal MCA angioplasty as a secondary intervention: 1 following failed treatment with a Merci retriever and the other after successful removal of proximal clot with a Merci retriever. One patient did not recover from the initial ischemic event despite an excellent angiographic result. Complete recanalization (modified TIMI grade 4) was achieved in 4 patients and near-complete recanalization with mild flow deficit (modified TIMI grade 3), in 3 patients.

CONCLUSIONS

PTA of the distal MCA with a microballoon is safe and effective for acute ischemic stroke. This case series demonstrates that endovascular treatment beyond the MCA bifurcation can dramatically reverse neurologic deficits.

The effect of increased ground-level habitat complexity on mouse population dynamics

We investigated experimentally the influence of habitat structure on the population dynamics of house mice. Three habitat types were used. In one, dense stands of regenerating cypress pine were felled and left in situ to cover at least 40% of experimental plots, providing high complexity at ground level; in another, dense stands of regenerating pine were left intact, providing low complexity at ground level; in the third, open grassland adjacent to dense stands of regenerating pine also provided low complexity at ground level. Mouse populations occurred at higher densities in felled pine plots compared with both the standing pine and grassland plots, consistent with the hypothesis that the presence of increased habitat complexity at ground level reduced the impact of predation. Even though populations responded to the felled pine, they dropped to very low densities over winter, suggesting that the habitat was still marginal for the persistence of mice, probably due to a lack of food. The results are discussed with reference to their implications for the influence that habitat structure may have on the impact of introduced predators on native species.

Improved QSARs for predictive toxicology of halogenated hydrocarbons

In our continuing efforts to provide a predictive toxicology capability, we seek to improve QSARs (quantitative structure-activity relationships) for chemicals of interest. Currently, although semi-empirical molecular orbital methods are hardly the state of the art for studying small molecules, AM1 calculations appear to be the method of choice when calculating quantum-chemical descriptors. However, with the advent of modern computational capabilities and the development of fast algorithms, ab initio molecular orbital and first principles density functional methods can be expeditiously applied in current QSAR studies. We present a study on halogenated alkanes to assess whether more accurate quantum methods result in QSARs that correlate better with experimental data. Furthermore, improved QSARs can also be obtained through development of new descriptors with explicit physical interpretations that should lead to better understanding of the mechanisms involved in the toxic response. We show that descriptors calculated from chemical intermediates may be useful in future QSARs.

Trapping efficiency for foxes (Vulpes vulpes) in central New SouthWales: age and sex biases and the effects of reduced fox abundance

A total of 276 red foxes (Vulpes vulpes) was captured over 40 597 trap-nights during 1994–96 at three separate sites in central New South Wales, resulting in an overall trapping efficiency of one fox per 147 trap-nights. Trapping using multiple trap sets placed at carcases was 3.2 times more efficient than trapping using single trap sets. During 1994–95, when two of the sites suffered a severe drought, fox abundance declined to less than 0.2 foxes km–1 of spotlight transect; trapping efficiency at those sites also declined, to an average of one fox per 315 trap-nights. Mean trapping efficiency for non-drought periods was one fox per 135 trap-nights, 2.3 times more efficient than during the drought period. In 1995 and 1996, 353 foxes were shot in areas adjacent to each site. This gave the opportunity to compare sex and age biases between the trapped and shot samples: the ratio of males to females was significantly higher in the trapped sample than in the shot sample, and there was also a significantly higher ratio of adults to juveniles in the trapped sample than in the shot sample.

A graph-theoretic approach to modeling metabolic pathways

The metabolic pathways of medazepam, oxazepam, and diazepam were modeled using graph-theoretic transforms which are incorporable into computer-assisted metabolic analysis programs. The information, represented in the form of a graph-theoretic transform kit, which was obtained from these pathways was then used to predict the metabolites of other benzodiazepine compounds. The transform kits gave statistically significant predictions with respect to a statistical method for evaluating the performance of the transform kits.

Report on five and a half years of the Cancer Detection Centre, Aukland Division, Cancer Society of New Zealand

An account is given of the setting up of a cancer detection centre at Auckland. In the first five-and-a-half years 3001 patients were examined. Forty-two cancers were detected and 1056 patients had non-malignant medical diseases.