Daryl K. Gray

Inhalation of carbon monoxide prevents liver injury and inflammation following hind limb ischemia/reperfusion

The induction of heme oxygenase (HO), the rate limiting enzyme in the conversion of heme into carbon monoxide (CO) and biliverdin, limits liver injury following remote trauma such as hind limb ischemia/reperfusion (I/R). Using intravital video microscopy, we tested the hypothesis that inhaled CO (250 ppm) would mimic HO‐derived liver protection. Hind limb I/R significantly decreased sinusoidal diameter and volumetric flow, increased leukocyte accumulation within sinusoids, increased leukocyte rolling and adhesion within postsinusoidal venules, and significantly increased hepatocyte injury compared with naïve animals. Inhalation of CO alone did not alter any microcirculatory or inflammatory parameters. Inhalation of CO following I/R restored volumetric flow, decreased stationary leukocytes within sinusoids, decreased leukocyte rolling and adhesion within postsinusoidal venules, and significantly reduced hepatocellular injury following hind limb I/R. HO inhibition did not alter microcirculatory parameters in naïve mice, but did increase inflammation, as well as increase hepatocyte injury following hind limb I/R. Inhalation of CO during HO inhibition significantly reduced such microcirculatory deficits, hepatic inflammation, and injury in response to hind limb I/R. In conclusion, these results suggest that HO‐derived hepatic protection is mediated by CO, and inhalation of low concentrations of CO may represent a novel therapeutic approach to prevent remote organ injury during systemic inflammatory response syndrome, or SIRS.

Accuracy of technetium‐99m SPECT‐CT hybrid images in predicting the precise intraoperative anatomical location of parathyroid adenomas

This study evaluated the accuracy of single photon emission computed tomography (SPECT)‐CT imaging for the preoperative localization of parathyroid adenomas.

Success of Urgent-Start Peritoneal Dialysis in a Large Canadian Renal Program

♦ Background: Many patients start renal replacement therapy urgently on in-center hemodialysis via a central venous catheter, which is considered suboptimal. An alternative approach to manage these patients is to start them on peritoneal dialysis (PD). In this report, we describe the first reported Canadian experience with an urgent-start PD program. Additionally we reviewed the literature in this area. ♦ Methods: In this prospective observational study, we report on our experience in a single academic center. This program started in July 2010. We included patients who initiated PD urgently, that is within 2 weeks of catheter insertion. We followed all incident PD patients until October 2013 for mechanical and infectious complications. Peritoneal dialysis catheters were inserted either percutaneously or laparoscopically and dialysis was initiated in either an inpatient or outpatient setting. ♦ Results: Thirty patients were started on urgent PD during our study period. Follow-up ranged from 28 to 1,050 days. Twenty insertions (66.7 %) were done percutaneously and 10 (33.3%) were laparoscopic. Dialysis was initiated within 2 weeks (range: 0 – 13 days, median = 6 days). Twenty-four patients (80%) started PD in an outpatient setting and 6 patients (20%) required immediate inpatient PD start. Three patients (10%) developed a minor peri-catheter leak during the first week of training that was managed conservatively. There were no episodes of peritonitis or exit-site/tunnel infection during the first 4 weeks post-insertion. Four patients (13.3 %) from the percutaneous insertion group and 2 patients (6.7%) from laparoscopic insertions developed catheter dysfunction due to migration, which was managed by repositioning, without need for catheter replacement or modality switch. ♦ Conclusions: Our results are consistent with other studies in this area and demonstrate that urgent-start PD is an acceptable and safe alternative to hemodialysis in patients who need to start dialysis urgently without established dialysis access.

The role of endogenous heme oxygenase in the initiation of liver injury following limb ischemia/reperfusion

BACKGROUND/AIMS Heme oxygenase (HO) derived liver protection was tested in mice following 1 h bilateral hindlimb ischemia and either 1.5 or 3 h reperfusion. METHODS Groups consisted of limb ischemia/reperfusion (I/R), sham (no I/R), I/R+chromium mesoporphyrin (I/R+CrMP;40 micromol/kg, i.p.), or I/R+hemin (10 mg/kg, i.p.). The vital dye propidium iodide (PI), was used to measure hepatocellular death (#/0.1 mm(3)), while the number of sinusoids perfused by red blood cells (SP(RBC)) were measured from the periportal (Pp) and pericentral (Pc) zones of liver acini using intravital microscopy. Whole organ injury was estimated from serum alanine aminotransferase (ALT). RESULTS SP(RBC) reduced within 1.5 h with no further decline following 3 h. CrMP resulted in a dramatic loss of SP(RBC) following 3 h only. Hemin restored perfusion in both zones. Hepatocellular death and organ injury increased at 1.5 and 3 h. At 1.5 h, CrMP further increased cell death in the Pc zone, as well as whole organ injury, while hemin restored cell viability. Increased HO mRNA, protein and activity suggested induction within 3 h. CONCLUSIONS HO does not protect perfusion during the early stage (1.5 h), but becomes increasingly important in preserving liver perfusion and cell viability during the later stage (3 h) of liver injury.

Human Immunodeficiency Virus, Hepatitis B, and Hepatitis C Seroprevalence in a Canadian Trauma Population

BACKGROUND The current seroprevalence of human immunodeficiency virus (HIV), hepatitis B, and hepatitis C in the Canadian trauma population is unknown. Establishing the seroprevalence of these diseases is vital for education, postexposure prophylaxis, and counseling, and to establish potential screening guidelines. The purpose of this study was to determine the seroprevalence of HIV, hepatitis B, and hepatitis C in the trauma population of London, Ontario, Canada. METHODS All adult (aged > or = 18 years) trauma patients treated by the trauma team at London Health Sciences Centre were prospectively studied from January to December 2003. The study was conducted as a linked, confidential serosurvey with delayed full disclosure. Serum was analyzed for HIV, hepatitis C antibody, and Hepatitis B surface antigen. RESULTS A total of 287 (76%) of 377 consecutive trauma patients had blood testing completed. Of the 287 patients tested, 1 (0.3%) was positive for hepatitis B, 8 (2.8%) were positive for hepatitis C, and no patients tested positive for HIV. Hepatitis C-positive patients were predominantly men (63%) with a mean age of 46 years and a mean Injury Severity Score of 19; 63% were injured in a motor vehicle crash, and 88% were discharged alive. There were no statistically significant differences in the demographic and injury profiles from the hepatitis C-negative patients (p > 0.2 for all). CONCLUSION This is the first study to determine the rates of HIV, hepatitis B, and hepatitis C in the Canadian trauma population. Our trauma population demonstrated a threefold higher hepatitis C seroprevalence rate compared with the general population. Hepatitis C poses the highest risk to the trauma team of the three bloodborne diseases studied. With no vaccine or postexposure prophylaxis currently available for hepatitis C, this study highlights the importance of prevention and the strict use of universal precautions in the setting of trauma.

Delayed hemorrhagic complications in the nonoperative management of blunt splenic trauma: early screening leads to a decrease in failure rate.

BACKGROUND Delayed splenic rupture is the Achilles’ heel of nonoperative management (NOM) for blunt splenic injury (BSI). Early computed tomographic (CT) scanning for features suggesting high risk of nonoperative failure, splenic pseudoaneurysms (SPAs), and arterial extravasation (AE), in concert with the appropriate use of splenic arterial embolization (SAE) is a viable method to reduce rates of failure of NOM. We report our 12-ear experience with a protocol for mandatory repeat CT evaluation at 48 hours and selective SAE. METHODS A retrospective cohort analysis was performed on all consecutive adult trauma patients with BSI between 1995 and 2012. We evaluated an early/control (1995–1999) and a present/intervention (2000–2012) cohort in which SAE became available and 48-hour CT scans were implemented. RESULTS The study included 773 patients (157 early vs. 616 present) with BSI. The proportion of patients managed nonoperatively (53% vs. 77%, p < 0.01) and overall splenic salvage rate (46% vs. 77%, p < 0.01) were improved in the present cohort. Among patients selected for NOM, there was a significant improvement in the failure rate of NOM (12% vs. 0.6%, p < 0.01) as well as in the length of hospital stay (8 days vs. 6 days, p < 0.01). Delayed development of SPA and/or AE was detected in 6% of BSI in the present cohort and was distributed among all grades of injury. CONCLUSION The delayed development of SPA and AE is not an entirely rare event following BSI. Reevaluation with CT at 48 hours following admission and the use of SAE significantly decrease the failure rate of NOM. LEVEL OF EVIDENCE Therapeutic study, level III.

Low-dose inhaled carbon monoxide attenuates the remote intestinal inflammatory response elicited by hindlimb ischemia-reperfusion

Heme oxygenase (HO) represents the rate-limiting enzyme in the degradation of heme into carbon monoxide (CO), iron, and biliverdin. Recent evidence suggests that several of the beneficial properties of HO, may be linked to CO. The objectives of this study were to determine if low-dose inhaled CO reduces remote intestinal leukocyte recruitment, proinflammatory cytokine expression, and oxidative stress elicited by hindlimb ischemia-reperfusion (I/R). Male mice underwent 1 h of hindlimb ischemia, followed by 3 h of reperfusion. Throughout reperfusion, mice were exposed to AIR or AIR + CO (250 ppm). Following reperfusion, the distal ileum was exteriorized to assess the intestinal inflammatory response by quantifying leukocyte rolling and adhesion in submucosal postcapillary venules with the use of intravital microscopy. Ileum samples were also analyzed for proinflammatory cytokine expression [tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta] and malondialdehyde (MDA) with the use of enzyme-linked immunosorbent assay and thiobarbituric acid reactive substances assays, respectively. I/R + AIR led to a significant decrease in leukocyte rolling velocity and a sevenfold increase in leukocyte adhesion. This was also accompanied by a significant 1.3-fold increase in ileum MDA and 2.3-fold increase in TNF-alpha expression. Treatment with AIR + CO led to a significant reduction in leukocyte recruitment and TNF-alpha expression elicited by I/R; however, MDA levels remained unchanged. Our data suggest that low-dose inhaled CO selectively attenuates the remote intestinal inflammatory response elicited by hindlimb I/R, yet does not provide protection against intestinal lipid peroxidation. CO may represent a novel anti-inflammatory therapeutic treatment to target remote organs following acute trauma and/or I/R injury.

Compartment syndrome-induced microvascular dysfunction: an experimental rodent model.

BACKGROUND Acute compartment syndrome (CS) is a limb-threatening disease that results from increased intracompartmental pressure. The pathophysiologic mechanisms by which this occurs are poorly understood. This study was designed to measure the effects of increased intracompartmental pressure on skeletal muscle microcirculation, inflammation and cellular injury using intravital videomicroscopy (IVVM) in a clinically relevant small animal model. METHODS We induced CS in 10 male Wistar rats (175-250 g), using a saline infusion technique. Intracompartmental pressure was controlled between 30 and 40 mm Hg and maintained for 45 minutes. After fasciotomy, the extensor digitorum longus muscle was visualized using IVVM, and perfusion was quantified. We quantified leukocyte recruitment to measure the inflammatory response. We measured muscle cellular injury using a differential fluorescent staining technique. RESULTS The number of nonperfused capillaries increased from 12.7 (standard error of the mean [SEM] 1.4 ) per mm in the control group to 30.0 (SEM 6.7) per mm following 45 minutes of elevated intracompartmental pressure (CS group; p = 0.031). The mean number of continuously perfused capillaries (and SEM) decreased from 78.4 (3.2) per mm in the control group to 41.4 (6.9) per mm in the CS group (p = 0.001). The proportion of injured cells increased from 5.0% (SEM 2.1%) in the control group to 16.3% (SEM 6.8%) in the CS group (p = 0.006). The mean number of activated leukocytes increased from 3.6 (SEM 0.7) per 100 μm(2) in the control group to 8.6 (SEM 1.8) per 100 μm(2) in the CS group (p = 0.033). CONCLUSION Early CS-induced microvascular dysfunction resulted in a decrease in nutritive capillary perfusion and an increase in cellular injury and was associated with a severe acute inflammatory component.

Indomethacin reduces cell damage: shedding new light on compartment syndrome.

Introduction: Indomethacin may preserve tissue viability in compartment syndrome. The mechanism of improved tissue viability is unclear, but the anti-inflammatory effects may alter the relative contribution of tissue necrosis versus apoptosis to cellular injury. Existing studies have only considered indomethacin administration before induction of elevated intracompartment pressure. The purpose of this study was to determine the effect of timing of indomethacin administration on muscle damage in elevated intracompartment pressure and to assess apoptosis as a cause of tissue demise. Methods: Twenty-four Wistar rats were randomized to elevated intracompartmental pressure (EICP) for either 45 or 90 minutes (30 mmHg). In the 45-minute cohort, indomethacin was withheld in Group 1 (CS45), given before induction of EICP in Group 2 (CS45Indo0), or given after 30 minutes of EICP/15 minutes before fasciotomy in Group 3 (CS45Indo30). In the 90-minute cohort, indomethacin was withheld in Group 4 (CS90) or given after 30 or 60 minutes of EICP in Groups 5 (CS90Indo30) and 6 (CS90Indo60). Intravital microscopy and fluorescent staining assessed capillary perfusion, cell damage, and inflammatory activation within extensor digitorum longus muscle. Apoptosis was assessed using spectrophotometric assessment of caspase levels. Groups 1 to 3 and 4 to 6 were compared using analysis of variance with P < 0.05 deemed significant. Results: Perfusion and tissue viability improved in indomethacin-treated groups. Nonperfused capillaries decreased from Group 1 (CS45) (50.1 ± 2.5) to Group 2 (CS45Indo0) (38.4 ± 1.8) and Group 3 (CS45Indo30) (14.13 ± 1.73) (P < 0.05). Similarly, Group 5 (CS90Indo30) and Group 6 (CS90Indo60) had 25% fewer nonperfused capillaries compared with Group 4 (CS90) (P < 0.0001). Group 2 (CS45Indo0) and Group 3 (CS45Indo30) showed fewer damaged cells (1% ± 0.5% and 8.7% ± 2%) compared with Group 1 (CS45) (20% ± 14%) (P < 0.0001). Group 5 (CS90Indo30) showed decreased cell damage (13% ± 1%) compared with Group 4 (CS90) (18% ± 1%) (P < 0.01). Group 6 (CS90Indo60) also showed decreased cell damage (11% ± 1%) compared with Group 4 (CS90) (18% ± 1%); however, this difference was not significant (P > 0.05). Apoptotic activity was present with elevated intracompartment pressure. At 30 minutes, there were elevated caspase levels in Group 4 and Group 6 EICP groups (0.47 ± 0.08) compared with control subjects (0.19 ± 0.02) (P < 0.003). However, indomethacin-treated groups did not differ from control subjects with regard to caspase levels (P > 0.05). Conclusion: Indomethacin decreased cell damage and improved perfusion in elevated intracompartment pressure. The benefits of indomethacin were partially time-dependent; some improvement in tissue viability occurred regardless of timing of administration. Although apoptosis was common in elevated intracompartment pressure, the protective effect of indomethacin does not appear to be related to apoptosis. Clinical Relevance: Adjuvant treatment with indomethacin may improve outcome in compartment syndrome.

The role of trauma team leaders in missed injuries: does specialty matter?

BACKGROUND Previous studies have identified missed injuries as a common and potentially preventable occurrence in trauma care. Several patient- and injury-related variables have been identified, which predict for missed injuries; however, differences in rate and severity of missed injuries between surgeon and nonsurgeon trauma team leaders (TTLs) have not previously been reported. METHODS A retrospective review was conducted on a random sample of 10% of all trauma patients (Injury Severity Score [ISS] > 12) from 1999 to 2009 at a Canadian Level I trauma center. Missed injuries were defined as those identified greater than 24 hours after presentation and were independently adjudicated by two reviewers. TTLs were identified as either surgeons or nonsurgeons. RESULTS Of our total trauma population of 2,956 patients, 300 charts were randomly pulled for detailed review. Missed injuries occurred in 46 patients (15%). Most common missed injuries were fractures (n = 32, 70%) and thoracic injuries (n = 23, 50%). The majority of missed injuries resulted in minor morbidity with only 5 (11%) requiring operative intervention. On univariate analysis, higher ISS (p < 0.01), higher maximum Abbreviated Injury Scale (MAIS) score of the thorax (p < 0.01), and nonsurgeon TTL status were predictive of missed injuries (p = 0.02). Multivariable logistic regression revealed that, after adjustment for age, ISS, and severe head injuries, the presence of a nonsurgeon TTL was associated with an increased odds of missed injury (odds ratio, 2.15; 95% confidence interval, 1.10–4.20). CONCLUSION Missed injuries occurred in 15% of patients. A unique finding was the increased odds of missed injury with nonsurgeon TTLs. Further research should be undertaken to explore this relationship, elucidate potential causes, and propose interventions to narrow this discrepancy between TTL provider types. LEVEL OF EVIDENCE Therapeutic study, level IV. Prognostic and epidemiologic study, level III.