Family Comes First: A Pilot Study of the Incorporation of Social Support Into Resident Well-being

BACKGROUND

Recent work has shown that understanding of work-related stress by family and friends is associated with increased resident well-being. However, it is often difficult for residents to communicate with their support persons (SPs), especially those who have minimal understanding of the medical field, regarding even the most basic functions of their role in the health care system. This study aimed to pilot test an innovative wellness event focusing on the social relatedness component of resident well-being.

METHODS

The target population included 30 new residents at 2 anesthesiology residency programs and their SPs in 2017. The Family Anesthesia Experience (FAX) began with didactic presentations and a panel discussion about wellness topics. It concluded with a multifaceted simulation experience. Participants were surveyed before and after the event. Measures included SPs' understanding of residents' work and residents' stress, burnout, resilience, and social support levels. Student t tests, Mann-Whitney U tests, Wilcoxon signed-rank tests, and repeated measures analysis of variance were used to examine the impact of the event.

RESULTS

Twenty-two (84.6%) of the 26 intervention clinical anesthesia year 1 residents who attended FAX completed the postevent surveys, and all intervention SPs (100%, n = 33) completed both pre-event and postevent surveys. The event was well received by the residents (100%) and their SPs (100%). Improvement in perceived understanding in the intervention SPs group (Pre: 1.44 ± 0.63, Post: 2.69 ± 0.33, P < .0001) was observed. Not all metrics of well-being for the residents achieved significance in change; however, decreased stress was observed compared with historical controls (Control: 1.91 ± 0.61, Intervention: 1.54 ± 0.42, P = .019).

CONCLUSION

The event led to improved SPs' understanding of the role of an anesthesiology resident.

Should Objective Structured Clinical Examinations Assist the Clinical Competency Committee in Assigning Anesthesiology Milestones Competency?

BACKGROUND

With the integration of Objective Structured Clinical Examinations into the Anesthesiology primary board certification process, residency programs may choose to implement Objective Structured Clinical Examinations for resident skill assessment. The aim of this study was to evaluate Objective Structured Clinical Examination-based milestone assessment and compare with Clinical Competency Committee milestone assessment that is based purely on clinical evaluations.

METHODS

An annual Objective Structured Clinical Examination event was used to obtain milestone assessment of clinical anesthesia year 0-clinical anesthesia year 3 residents for selected milestones in patient care, professionalism, and interpersonal/communication skills. The Objective Structured Clinical Examination scenarios were different for each training level. The Clinical Competency Committee evaluated each resident semiannually based on clinical evaluations of resident performance. The Clinical Competency Committee milestone assessments from 2014 to 2016 that were recorded closest to the Objective Structured Clinical Examination event (±3 months) were compared to the Objective Structured Clinical Examination milestone assessments. A total of 35 residents were included in this analysis in 3 different training cohorts: A (graduates 2016, n = 12); B (graduates 2017, n = 10); and C (graduates 2018, n = 13). All residents participated in Objective Structured Clinical Examinations because their clinical anesthesia year 0 year and Clinical Competency Committee milestone data had been reported since December 2014.

RESULTS

Both assessment techniques indicated a competency growth proportional to the length in training. Despite limited cumulative statistics in this study, average trends in the Objective Structured Clinical Examination-Clinical Competency Committee relationship indicated: (1) a good proportionality in reflecting competency growth; (2) a grade enhancement associated with Clinical Competency Committee assessment, dominated by evaluations of junior residents (clinical anesthesia year 0-clinical anesthesia year 1); and (3) an expectation bias in Clinical Competency Committee assessment, dominated by evaluation of senior residents (clinical anesthesia year 2-clinical anesthesia year 3).

CONCLUSIONS

Our analysis confirms the compatibility of the 2 evaluation methods in reflecting longitudinal growth. The deviation of Objective Structured Clinical Examination assessments versus Clinical Competency Committee assessments suggests that Objective Structured Clinical Examinations may be providing additional or different information on resident performance. Educators might consider using both assessment methods to provide the most reliable and valid competency assessments during residency.

Use of Dexmedetomidine in a Parturient With Multiple Endocrine Neoplasia Type 2A Undergoing Adrenalectomy and Thyroidectomy: A Case Report

Dexmedetomidine is a selective α2-agonist, frequently used in perioperative medicine as anesthesia adjunct. The medication carries a Food and Drug Administration pregnancy category C designation and is therefore rarely used for parturients undergoing nonobstetric surgery. We are reporting the use of dexmedetomidine in the anesthetic management of a parturient undergoing minimally invasive unilateral adrenalectomy for pheochromocytoma during the second trimester of pregnancy. Additionally, because of the multiple endocrine neoplasia type 2A constellation with diagnosis of medullary thyroid cancer, the patient underwent a total thyroidectomy 1 week after the adrenalectomy.

Replicating an Educational OSCE Project for Skill Assessment of Junior Anesthesiology Residents at Multiple Institutions: A Qualitative Description

BACKGROUND

Educational research projects are often developed and implemented at a single institution. However, the research project methods and results may not be generalizable and able to be replicated successfully at other institutions. The aim of this study was to investigate the process of replicating an effective educational Objective Structured Clinical Examination (OSCE) event at multiple other institutions.

METHODS

An OSCE event was initially designed and implemented at the primary institution to assess the skill level of junior residents on the performance of basic anesthesia tasks. After the initial implementation, additional institutions were recruited to participate in a replication of this OSCE event at their own institutions. The primary institution provided the OSCE scenarios, assessment tools, rater training, and resident participant instructions. The participating secondary institutions' (n = 4) event managers obtained Institutional Review Board [IRB] approval, developed the event schedule, assigned faculty evaluators, and organized the simulation space at their own medical centers. The events were assessed by the secondary institutions' resident and faculty participants via an anonymous survey regarding the event's content and their perception of its educational value.

RESULTS

We replicated a complex educational OSCE event, developed and implemented at 1 institution, at 4 other institutions. Resident participants (n = 60), participating faculty (n = 24), and event directors (n = 4) indicated a high level of appreciation for the OSCE event.

CONCLUSION

Using a structured approach, educational OSCE events can be successfully replicated at multiple institutions. Organization of multi-institutional studies and collaborative efforts is complex. This study illustrates 1 example of how to successfully approach multi-institutional educational projects.

Dilemma during ultrasound-guided internal jugular venous catheterization

The presence of Internal Jugular Valves can pose a diagnostic and procedural challenge during ultrasound‐guided cannulation. After ruling out dissection, thrombus, or ultrasound artifacts, it can still be accessed and successfully cannulated with appropriate precautions including use of Live ultrasound, positioning, use of soft‐tipped catheters, and minimizing duration of catheter placement.

Emergency Manuals Improved Novice Physician Performance During Simulated ICU Emergencies

BACKGROUND

Emergency manuals, which are safety essentials in non-medical high-reliability organizations (e.g., aviation), have recently gained acceptance in critical medical environments. Of the existing emergency manuals in anesthesiology, most are geared towards intraoperative settings. Additionally, most evidence supporting their efficacy focuses on the study of physicians with at least some meaningful experience as a physician. Our aim was to evaluate whether an emergency manual would improve the performance of novice physicians (post-graduate year [PGY] 1 or first year resident) in managing a critical event in the intensive care unit (ICU).

METHODS

PGY1 interns (n=41) were assessed on the management of a simulated critical event (unstable bradycardia) in the ICU. Participants underwent a group allocation process to either a control group (n=18) or an intervention group (emergency manual provided, n=23). The number of successfully executed treatment and diagnostic interventions completed was evaluated over a ten minute (600 seconds) simulation for each participant.

RESULTS

The participants using the emergency manual averaged 9.9/12 (83%) interventions, compared to an average of 7.1/12 (59%) interventions (p < 0.01) in the control group.

CONCLUSIONS

The use of an emergency manual was associated with a significant improvement in critical event management by individual novice physicians in a simulated ICU patient (23% average increase).

Systemic-to-pulmonary artery pressure ratio as a predictor of patient outcome following liver transplantation

AIM

To assess the value of the mean systemic-to-pulmonary artery pressure (MAP/mPAP) ratio for predicting outcomes following orthotopic liver transplant (OLT).

METHODS

A retrospective data analysis was performed and data (mean arterial blood pressure, mean pulmonary artery pressure and Cardiac Index) were collected at several points during OLT. Outcomes evaluated were duration of postoperative endotracheal intubation [ET; minutes after intensive care unit (ICU) arrival], length of ICU stay, total hospitalization and frequency of immediate postoperative complications. A total of 91 patients were included in the data analysis. Based on the intraoperative course of the MAP/mPAP ratio, 2 hemodynamic responses were identified: Group 1 (MAP/mPAP ratio increase during anhepatic period with postreperfusion recovery, n = 66); and Group 2 (MAP/mPAP ratio with no change during anhepatic period or decreased without recovery, n = 25).

RESULTS

The main finding was that the lack of increased MAP/mPAP ratio in the anhepatic period was associated with: (1) longer intubation times; and (2) prolonged ICU stays and total hospitalization time, when compared to patients with an increase in MAP/mPAP ratio during the anhepatic period.

CONCLUSION

The data from this retrospective study should raise awareness to the mean systemic to pulmonary artery pressure ratio as a potential indicator for poor outcome after OLT. Further prospective studies are needed for validation.

Cognitive aid use improves transition of care by graduating medical students during a simulated crisis

BACKGROUND

Residents are expected to have transition of care (ToC) skills upon entering graduate medical education. It is unclear whether experience and training during medical school is adequate.

OBJECTIVE

The aim of the project was to assess: 1) graduating medical students' ability to perform ToC in a crisis situation, and 2) whether using a cognitive aid improves the ToC quality.

METHODS

The authors developed simulation scenarios for rapid response teams and a cognitive aid to assist in the ToC during crisis situations. Graduating medical students were enrolled and randomly divided into teams of three students, randomly assigned into one of two groups: teams using a cognitive aid for ToC (CA), or not using a cognitive aid (nCA). In the scenario, teams respond to a deteriorating patient and then transfer care to the next provider after stabilization. Three faculty reviewed the recording to assess completeness of the ToC and the overall quality. A completeness score was expressed as a fraction of the maximum score. Statistical analysis was performed using a t-test and Mann-Whitney U test.

RESULTS

A total of 112 senior medical students participated: CA n=19, nCA n=17. The completeness score of the ToC and overall quality improved when using the cognitive aid (completeness score: CA 0.80±0.06 vs. nCA 0.52±0.07, p<0.01; ToC quality: CA 3.16±0.65 vs. nCA 1.92±0.56, p<0.01). Participants' rating of knowledge and comfort with the ToC process increased after the simulation.

CONCLUSION

The completeness of information transfer during the ToC process by graduating medical students improved by using a cognitive aid in a simulated patient crisis.

Ultrasound Skill and Application of Knowledge Assessment using an Innovative OSCE Competition-Based Simulation Approach

BACKGROUND

Despite Point-of Care Ultrasound (PoC US) rapidly becoming an important tool in perioperative medicine structured education, PoC US is currently rarely integrated into the anesthesiology residency curriculum. The aim of this project was to assess the current ultrasound skills of anesthesiology residents at one institution and evaluate the needs for development of a formal ultrasound curriculum.

METHODS

A event containing 6 different OSCE PoC US stations was developed with following stations: vascular, peripheral nerve block, lung ultrasound, transthoracic echocardiography (TTE) human model, pathologic TTE (simulator), and inferior vena cava (IVC) evaluation (simulator). The ability to obtain an US image or to interpret the US information was evaluated using a checklist and global rating scale. After IRB approval, anesthesiology residents participated in this event (n=30; PGY 2-4).

RESULTS

All residents were able to identify vascular structures and demonstrated sufficient ultrasound skill for lung anatomy IVC assessment. The lowest scores were observed for performing and interpreting TTE. There were no differences in resident ultrasound skills for all OSCE stations except minor differences between PGY 2 and PGY 4 in TTE pathology station. While more advanced residents had more clinical exposure to ultrasound for procedures and point-of-care diagnosis, we did not find growth in ultrasound skill level. Despite performing sufficient ultrasound guided peripheral nerve blocks, PGY 4 residents were not able to consistently identify common nerve block targets.

CONCLUSIONS

Our findings indicate that exposure and clinical use of ultrasound for procedures and point-of-care diagnosis is not sufficient for developing competency in PoC US and that a formal curriculum throughout the entire anesthesiology residency is needed to ensure PoC US competency.

Harlequin syndrome as a complication of epidural anesthesia

Harlequin syndrome is a rare neurological condition that results in unilateral facial flushing and sweating. Although the syndrome is generally a benign condition with complete resolution if appropriate treatment is initiated, unilateral facial flushing can be a sign of several serious conditions and should be thoroughly investigated. Sudden onset of facial flushing related to harlequin syndrome developed in a patient who had bilateral lung transplant with postoperative epidural anesthesia for pain control. Differential diagnosis includes neurovascular disease (acute stroke), malignant neoplasm of brain or lung, Horner syndrome, idiopathic hyperhidrosis, and Frey syndrome. Harlequin syndrome is often easily treated by discontinuing the anesthetic or adjusting placement of the epidural catheter.

Successful implementation of a packed red blood cell and fresh frozen plasma transfusion protocol in the surgical intensive care unit

Background

Blood product transfusions are associated with increased morbidity and mortality. The purpose of this study was to determine if implementation of a restrictive protocol for packed red blood cell (PRBC) and fresh frozen plasma (FFP) transfusion safely reduces blood product utilization and costs in a surgical intensive care unit (SICU).

Study Design

We performed a retrospective, historical control analysis comparing before (PRE) and after (POST) implementation of a restrictive PRBC/FFP transfusion protocol for SICU patients. Univariate analysis was utilized to compare patient demographics and blood product transfusion totals between the PRE and POST cohorts. Multivariate logistic regression models were developed to determine if implementation of the restrictive transfusion protocol is an independent predictor of adverse outcomes after controlling for age, illness severity, and total blood products received.

Results

829 total patients were included in the analysis (PRE, n=372; POST, n=457). Despite higher mean age (56 vs. 52 years, p=0.01) and APACHE II scores (12.5 vs. 11.2, p=0.006), mean units transfused per patient were lower for both packed red blood cells (0.7 vs. 1.2, p=0.03) and fresh frozen plasma (0.3 vs. 1.2, p=0.007) in the POST compared to the PRE cohort, respectively. There was no difference in inpatient mortality between the PRE and POST cohorts (7.5% vs. 9.2%, p=0.39). There was a decreased risk of urinary tract infections (OR 0.47, 95%CI 0.28-0.80) in the POST cohort after controlling for age, illness severity and amount of blood products transfused.

Conclusions

Implementation of a restrictive transfusion protocol can effectively reduce blood product utilization in critically ill surgical patients with no increase in morbidity or mortality.

The impact of exposure to liver transplantation anesthesia on the ability to treat intraoperative hyperkalemia: a simulation experience

The objective of this study was to assess whether resident exposure to liver transplantation anesthesia results in improved patient care during a simulated critical care scenario. Our hypothesis was that anesthesia residents exposed to liver transplantation anesthesia care would be able to identify and treat a simulated hyperkalemic crisis after reperfusion more appropriately than residents who have not been involved in liver transplantation anesthesia care. Participation in liver transplantation anesthesia is not a mandatory component of the curriculum of anesthesiology training programs in the United States. It is unclear whether exposure to liver transplantation anesthesia is beneficial for skill set development. A high-fidelity human patient simulation scenario was developed. Times for administration of epinephrine, calcium chloride, and secondary hyperkalemia treatment were recorded. A total of 25 residents with similar training levels participated: 13 residents had previous liver transplantation experience (OLT), whereas 12 residents had not been previously exposed to liver transplantations (non-OLT). The OLT group performed better in recognizing and treating the hyperkalemic crisis than the non-OLT group. Pharmacologic therapy for hyperkalemia was given earlier (OLT 53.3 ± 27.0 seconds versus non-OLT 148 ± 104.1 seconds; P < 0.01) and hemodynamics restored quicker (OLT 87.9 ± 24.9 seconds versus non-OLT 219.9 ± 87.1 seconds; P < 0.01). Simulation-based assessment of clinical skills is a useful tool for evaluating anesthesia resident performance during an intraoperative crisis situation related to liver transplantations. Previous liver transplantation experience improves the anesthesia resident's ability to recognize and treat hyperkalemic cardiac arrest.

Accuracy of point-of-care glucose measurements

Control of blood glucose (BG) in an acceptable range is a major therapy target for diabetes patients in both the hospital and outpatient environments. This review focuses on the state of point-of-care (POC) glucose monitoring and the accuracy of the measurement devices. The accuracy of the POC glucose monitor depends on device methodology and other factors, including sample source and collection and patient characteristics. Patient parameters capable of influencing measurements include variations in pH, blood oxygen, hematocrit, changes in microcirculation, and vasopressor therapy. These elements alone or when combined can significantly impact BG measurement accuracy with POC glucose monitoring devices (POCGMDs). In general, currently available POCGMDs exhibit the greatest accuracy within the range of physiological glucose levels but become less reliable at the lower and higher ranges of BG levels. This issue raises serious safety concerns and the importance of understanding the limitations of POCGMDs. This review will discuss potential interferences and shortcomings of the current POCGMDs and stress when these may impact the reliability of POCGMDs for clinical decision-making.

Postoperative analgesia after radical prostatectomy with high-dose intrathecal morphine and intravenous naloxone: a retrospective review

BACKGROUND AND METHODS

Intrathecal opioids (ITOs) have been used for decades to control postoperative pain. Intrathecal opioid dosing is limited, however, by opioid-related side effects, most importantly respiratory depression. To overcome these limitations, we combined intrathecal morphine with a continuous intravenous (IV) postoperative naloxone infusion to control opioid-related side effects. The purpose of this study is to document the efficacy and safety of high-dose intrathecal morphine combined with postoperative naloxone infusion to provide postoperative analgesia after major surgery. After IRB approval, a retrospective chart analysis was performed on 35 patients who had a radical prostatectomy from 2004 to 2006. All patients received a single injection of ITOs before anesthesia, a typical general Anesthestic, followed by naloxone infusion at 5 microg/kg/h started 1 hour post-ITOs and continued for 22 hours postoperatively. The following information was collected: patient age, height, weight, anesthesia technique/time, and dose of ITOs given. Postoperative pain relief was assessed for 48 hours using the Visual Analog Score (VAS) for pain (0, no pain; 10, worst pain), perioperative opioid use, NSAID consumption, and ability of patient to ambulate. The safety of this novel treatment was assessed with opioid-related side effects and vital signs. All data are reported as mean (SD).

RESULTS

Mean ITOs given were morphine 1.3 (0.3) mg combined with fentanyl 56 (9) microg. The intrathecal morphine dose ranged from 0.8 to 1.7 mg. The mean worst pain VAS in the first 12 hours postoperatively was only 1.0 (1.7). The first NSAID dose was given 6.6 (3.1) hours post-ITOs. The first opioid on the floor was given an average of 22.6 (14.5) hours post-ITOs. A mean of only 5.7 (12.3) morphine equivalents were required on postoperative day 1 (POD 1). On POD 2, the mean worst pain VAS was only 2.6 (2.2) with only 5.7 (6.2) morphine equivalents needed to provide pain relief On POD 1, 25patients required no additional opioids for their entire hospital stay. Overall, 11 of 35 patients did not require any additional postoperative opioids. Thirty-four patients (97 percent) were able to ambulate in the first 12 hours postoperatively. No opioid-induced respiratory depression was observed. Opioid-related side effects (pruritus, nausea) were infrequent and minor.

CONCLUSIONS

High-dose ITOs combined with postoperative IV naloxone infusion provided excellent analgesia for radical prostate surgery. IV naloxone infusion appeared to control opioid side effects without diminishing the analgesia. No serious adverse effects were noted.

Blood viscosity modulates tissue perfusion: sometimes and somewhere

Each organ possesses specific properties for controlling microvascular perfusion. Such specificity provides an opportunity to design transfusion fluids that target thrombo-embolic or vasospasm-induced ischemia in a particular organ or that optimize overall perfusion from systemic shock. The role of viscosity in the design of these fluids might be underestimated, because viscosity is rarely monitored or considered in critical care decisions. Studies linking viscosity-dependent changes of microvascular perfusion to outcome-relevant data suggest that whole blood viscosity is negligible as a determinant of microvascular perfusion under physiological conditions when autoregulation is effective. Because autoregulation is driven to maintain oxygen supply constant, the organism will compensate for changes in blood viscosity to sustain oxygen delivery. In contrast, under pathological conditions in the brain and elsewhere, increases of overall viscosity should be avoided - including all the situations where vascular autoregulatory mechanisms are inoperative due to ischemia, structural damage or physiologic dysfunction. As latter conditions are not to identify with high certainty, the risks that accompany therapeutic correction of blood viscosity are outweighing the benefits. The ability to bedside monitor blood viscosity and to link changes in viscosity to outcome parameters in various clinical conditions would provide more solid foundation for evidence-based clinical management.

Dependence of acetylcholine and ADP dilation of pial arterioles on heme oxygenase after transfusion of cell-free polymeric hemoglobin

Polymers of cell-free hemoglobin have been designed for clinical use as oxygen carriers, but limited information is available regarding their effects on vascular regulation. We tested the hypothesis that the contribution of heme oxygenase (HO) to acetylcholine-evoked dilation of pial arterioles is upregulated 2 days after polymeric hemoglobin transfusion. Dilator responses to acetylcholine measured by intravital microscopy in anesthetized cats were blocked by superfusion of the HO inhibitor tin protoporphyrin-IX (SnPPIX) in a group that had undergone exchange transfusion with hemoglobin 2 days earlier but not in surgical sham and albumin-transfused groups. However, immunoblots from cortical brain homogenates did not reveal changes in expression of the inducible isoform HO1 or the constitutive isoform HO2 in the hemoglobin-transfused group. To test whether the inhibitory effect of SnPPIX was present acutely after hemoglobin transfusion, responses were measured within an hour of completion of the exchange transfusion. In control and albumin-transfused groups, acetylcholine responses were unaffected by SnPPIX but were blocked by addition of the nitric oxide synthase inhibitor N(omega)-nitro-l-arginine (l-NNA) to the superfusate. In hemoglobin-transfused groups, the acetylcholine response was blocked by either SnPPIX or l-NNA alone. The effect of another HO inhibitor, chromium mesoporphyrin (CrMP), was tested on ADP, another endothelial-dependent dilator, in anesthetized rats. Pial arteriolar dilation to ADP was unaffected by CrMP in controls but was attenuated 62% by CrMP in rats transfused with hemoglobin. It is concluded that 1) polymeric hemoglobin transfusion acutely upregulates the contribution of HO to acetylcholine-induced dilation of pial arterioles in cats, 2) this upregulation persists 2 days after transfusion when 95% of the hemoglobin is cleared from the circulation, and 3) this acute upregulation of HO signaling is ubiquitous in that similar effects were observed with a different endothelial-dependent agonist (i.e., ADP) in a another species (rat).

In situ immunoradiographic method for quantification of specific proteins in normal and ischemic brain regions

This study tested the application of an immunoisotopic assay for immunohistochemical localization and quantification of proteins in brain sections from rats without or with transient focal ischemia. We assessed the hypothesis that measurements of protein levels in injured brain determined by an isotopic assay using [(125)I]-protein A have greater reliability than those made by conventional immunoperoxidase labeling using diaminobenzidine. Quantification of immunoreactivities for glial fibrillary acidic protein (GFAP), glutamate transporter-1 (GLT-1) and heat shock protein-70 (HSP-70) was determined by optical density signal in the immunoisotopic and immunoperoxidase assays. In ischemic brain, the immunoisotopic assay detected protein increases (cortical penumbra HSP-70, 151+/-6%), protein decreases (cortical ischemic core GLT-1, 61+/-6%) and no changes in GFAP levels compared to controls animals. These results differed from the protein levels found by the immunoperoxidase assay, which showed elevated HSP-70, GLT-1 and GFAP in all ischemic regions. We conclude that nonspecific immunosignal confounds assessments of protein expression in injured brain and that the immunoisotopic method is a valid approach to regionally localize and quantify proteins after brain injury. The disadvantage of the falsely positive overestimation of protein immunoreactivity after stroke with the immunoperoxidase method has to be weighted with the advantage of the cellular resolution.

Cerebrovascular response to decreased hematocrit: effect of cell-free hemoglobin, plasma viscosity, and CO2

The effect of transfusing a nonextravasating, zero-link polymer of cell-free hemoglobin on pial arteriolar diameter, cerebral blood flow (CBF), and O2 transport (CBF x arterial O2 content) was compared with that of transfusing an albumin solution at equivalent reductions in hematocrit (approximately 19%) in anesthetized cats. The influence of viscosity was assessed by coinfusion of a high-viscosity solution of polyvinylpyrrolidone (PVP), which increased plasma viscosity two- to threefold. Exchange transfusion of a 5% albumin solution resulted in pial arteriolar dilation, increased CBF, and unchanged O2 transport, whereas there were no significant changes over time in a control group. Exchange transfusion of a 12% polymeric hemoglobin solution resulted in pial arteriolar constriction and unchanged CBF and O2 transport. Coinfusion of PVP with albumin produced pial arteriolar dilation that was similar to that obtained with transfusion of albumin alone. In contrast, coinfusion of PVP with hemoglobin converted the constrictor response to a dilator response that prevented a decrease in CBF. Pial arteriolar dilation to hypercapnia was unimpaired in groups transfused with albumin or hemoglobin alone but was attenuated in the largest vessels in albumin and hemoglobin groups coinfused with PVP. Unexpectedly, hypocapnic vasoconstriction was blunted in all groups after transfusion of albumin or hemoglobin alone or with PVP. We conclude that 1) the increase in arteriolar diameter after albumin transfusion represents a compensatory response that prevents decreased O2 transport at reduced O2-carrying capacity, 2) the decrease in diameter associated with near-normal O2-carrying capacity after cell-free polymeric hemoglobin transfusion represents a compensatory mechanism that prevents increased O2 transport at reduced blood viscosity, 3) pial arterioles are capable of dilating to an increase in plasma viscosity when hemoglobin is present in the plasma, 4) decreasing hematocrit does not impair pial arteriolar dilation to hypercapnia unless plasma viscosity is increased, and 5) pial arteriolar constriction to hypocapnia is impaired at reduced hematocrit independently of O2-carrying capacity.

Vascular response to infusions of a nonextravasating hemoglobin polymer

The clinical utility of cross-linked tetrameric hemoglobin solutions is limited by peripheral vasoconstriction thought to be due to scavenging of nitric oxide. In addition, transfusion of crude preparations of hemoglobin polymers can cause arterial hypertension. We tested the hypothesis that eliminating low-molecular-weight components from the polymer solution would prevent extravasation and its associated pressor response. A zero-link polymer of bovine hemoglobin was developed without chemical linkers left between the tetramers. Transfusion of unprocessed preparations of these polymers in rats resulted in appearance of the polymer in the renal hilar lymph. However, eliminating the low-molecular-weight components with a 300-kDa diafiltration resulted in an average hydrodynamic radius of 250 A and in undetectable levels of polymer in hilar lymph. Exchange transfusion in anesthetized rats and cats and in awake cats produced no increase in arterial pressure. In anesthetized cats, exchange transfusion with an albumin solution reduced hematocrit from 30 to 18%, increased cerebral blood flow, and dilated pial arterioles. In contrast, reducing hematocrit by transfusing the diafiltered polymer did not increase cerebral blood flow as pial arterioles constricted. These results are consistent with the hypothesis that the increase in arterial pressure associated with cell-free hemoglobin transfusion depends on hemoglobin extravasation. Constriction observed in the cerebrovascular bed with a nonextravasating hemoglobin polymer at low hematocrit is presumably a regulatory response to prevent overoxygenation at low blood viscosity.

Regional cerebral blood flow in cats with cross-linked hemoglobin transfusion during focal cerebral ischemia

The beneficial effect of hemodilution on cerebral blood flow (CBF) during focal cerebral ischemia is mitigated by reduced arterial oxygen content (CaO2). In anesthetized cats subjected to permanent middle cerebral artery occlusion, the time course of regional CBF was evaluated after isovolemic exchange transfusion with either albumin or a tetrameric hemoglobin-based oxygen carrier. The transfusion started 30 min after arterial occlusion. We tested the hypothesis that bulk oxygen transport (CBF x CaO2) to ischemic tissue is increased by hemoglobin transfusion at a hematocrit of 18% compared with albumin-transfused cats at a hematocrit of 18% or control cats at a hematocrit of 30% and equivalent arterial pressure. In the nonischemic hemisphere, CBF increased selectively after albumin transfusion, and oxygen transport was similar among groups. In the ischemic cortex, albumin transfusion increased CBF, but oxygen transport was not increased above that of the control group. Hemoglobin transfusion increased both CBF and oxygen transport in the ischemic cortex above values in the control group, but the increase was delayed until 4 h of ischemia. Consequently, acute injury volume measured at 6 h of ischemia was not significantly attenuated. In contrast to the cortex, CBF in the ischemic caudate nucleus was not substantially increased by either albumin or hemoglobin transfusion. Therefore, in a large animal model of permanent focal ischemia in which transfusion starts 30 min after ischemia, tetrameric cross-linked hemoglobin transfusion can augment oxygen transport to the ischemic cortex, but the increase can be delayed and not necessarily provide protection. Moreover, an end-artery region such as the caudate nucleus is less likely to benefit from hemodilution.

Lack of hypercapnic increase in cerebral blood flow at high blood viscosity in conscious blood-exchanged rats

BACKGROUND

The hypothesis of a compensatory dilation of cerebral vessels to maintain cerebral blood flow at a high blood viscosity was tested during hypercapnia in the study after replacement of blood by hemoglobin solutions of defined viscosities. If compensatory vasodilation exists at normocapnia at a high blood viscosity, vasodilatory mechanisms may be exhausted when hypercapnia is added, resulting in a lack of increase in cerebral blood flow at hypercapnia.

METHODS

In conscious rats, blood was replaced by ultrapurified cross-linked hemoglobin solutions that had defined and shear rate-independent low or high viscosities (low- and high-viscosity groups). Blood viscosity differed threefold between both groups (1.2 vs. 3.6 mP x s). Thereafter, rats inhaled either a normal or an increased concentration of carbon dioxide in air. Cerebral blood flow was determined by the iodo[14C]antipyrine method.

RESULTS

During normocapnia, global and local cerebral blood flows did not differ between both groups. With increasing degrees of hypercapnia, global and local cerebral blood flows were gradually elevated in the low-viscosity group (2.8 ml x mmHg(-1) CO2 x 100 g(-1) x min(-1)), whereas they remained unchanged in the high-viscosity group.

CONCLUSIONS

Changes in blood viscosity do not result in changes of cerebral blood flow as long as cerebral vessels can compensate for these changes by vasodilation or vasoconstriction. However, such vascular compensatory adjustments may be exhausted in their response to further pathophysiologic conditions in blood vessels that have already been dilated or constricted as a result of changes in blood viscosity.

Oxygen delivery at high blood viscosity and decreased arterial oxygen content to brains of conscious rats

We addressed the question to which extent cerebral blood flow (CBF) is maintained when, in addition to a high blood viscosity (Bvis) arterial oxygen content (CaO2 ) is gradually decreased. CaO2 was decreased by hemodilution to hematocrits (Hct) of 30, 22, 19, and 15% in two groups. One group received blood replacement (BR) only and served as the control. The second group received an additional high viscosity solution of polyvinylpyrrolidone (BR/PVP). Bvis was reduced in the BR group and was doubled in the BR/PVP. Despite different Bvis, CBF did not differ between BR and BR/PVP rats at Hct values of 30 and 22%, indicating a complete vascular compensation of the increased Bvis at decreased CaO2 . At an Hct of 19%, local cerebral blood flow (LCBF) in some brain structures was lower in BR/PVP rats than in BR rats. At the lowest Hct of 15%, LCBF of 15 brain structures and mean CBF were reduced in BR/PVP. The resulting decrease in cerebral oxygen delivery in the BR/PVP group indicates a global loss of vascular compensation. We concluded that vasodilating mechanisms compensated for Bvis increases thereby maintaining constant cerebral oxygen delivery. Compensatory mechanisms were exhausted at a Hct of 19% and lower as indicated by the reduction of CBF and cerebral oxygen delivery.

Local coupling of cerebral blood flow to cerebral glucose metabolism during inhalational anesthesia in rats: desflurane versus isoflurane

BACKGROUND

It is not known whether the effects of desflurane on local cerebral glucose utilization (LCGU) and local cerebral blood flow (LCBF) are different from those of other volatile anesthetics.

METHODS

Using the autoradiographic iodoantipyrine and deoxyglucose methods, LCGU, LCBF, and their overall means were measured in 60 Sprague-Dawley rats (10 groups, n = 6 each) during desflurane and isoflurane anesthesia and in conscious controls.

RESULTS

During anesthesia, mean cerebral glucose utilization was decreased compared with conscious controls: 1 minimum alveolar concentration (MAC) desflurane: -52%; 1 MAC isoflurane: -44%; 2 MAC desflurane: -62%; and 2 MAC isoflurane: -60%. Local analysis showed a reduction of LCGU in the majority of the 40 brain regions analyzed. Mean cerebral blood flow was increased: 1 MAC desflurane: +40%; 1 MAC isoflurane: +43%; 2 MAC desflurane and 2 MAC isoflurane: +70%. LCBF was increased in all brain structures investigated except in the auditory cortex. No significant differences (P < 0.05) could be observed between both anesthetics for mean values of cerebral glucose use and blood flow. Correlation coefficients obtained for the relation between LCGU and LCBF were as follows: controls: 0.95; 1 MAC desflurane: 0.89; 2 MAC desflurane: 0.60; 1 MAC isoflurane: 0.87; and 2 MAC isoflurane: 0.68.

CONCLUSION

Differences in the physicochemical properties of desflurane compared with isoflurane are not associated with major differences in the effects of both volatile anesthetics on cerebral glucose utilization, blood flow, and the coupling between LCBF and LCGU.

[Cerebral effects of perfluorocarbons]

For the usage as blood substitutes perfluorocarbons (PFC) have been developed as artificial oxygen carriers. In addition they may have potency for protective use in ischemic tissue. Formulation improvement achieved higher oxygen carrying capacity and better compatibility than the first generation of PFC. Preclinical studies have been performed in animal heart and brain. Former and progressed emulsification for intravascular use have been investigated for infarction and reperfusion injury. This investigations are reviewed and the potencies for the use of PFC in neurology, neurosurgery, diagnostics today and in the future are emphasized.

Local cerebral blood flow, local cerebral glucose utilization, and flow-metabolism coupling during sevoflurane versus isoflurane anesthesia in rats

BACKGROUND

Compared to isoflurane, knowledge of local cerebral glucose utilization (LCGU) and local cerebral blood flow (LCBF) during sevoflurane anesthesia is limited.

METHODS

LCGU, LCBF, and their overall means were measured in Sprague-Dawley rats (8 groups, n=6 each) during sevoflurane and isoflurane anesthesia, 1 and 2 MAC, and in conscious control animals (2 groups, n=6 each) using the autoradiographic 2-[14C]deoxy-D-glucose and 4-iodo-N-methyl-[14C]antipyrine methods.

RESULTS

During anesthesia, mean cerebral glucose utilization was decreased: control, 56+/-5 micronmol x 100 g(-1) x min(-1); 1 MAC isoflurane, 32+/-4 micromol x 100 g(-1) x min(-1) (-43%); 1 MAC sevoflurane, 37+/-5 micromol x 100 g(-1) x min(-1) (-34%); 2 MAC isoflurane, 23+/-3 micromol x 100 g(-1) x min(-1) (-58%); 2 MAC sevoflurane, 23+/-5 micromol x 100 g(-1) x min(-1) (-59%). Local analysis showed a reduction in LCGU in the majority of the 40 brain regions analyzed. Mean cerebral blood flow was increased as follows: control 93+/-8 ml x 100 g(-1) x min(-1); 1 MAC isofurane, 119+/-19 ml x 100 g(-1) x min(-1) (+28%); 1 MAC sevoflurane, 104+/-15 ml x 100 g(-1) x min(-1) (+12%); 2 MAC isoflurane, 149+/-17 ml x 100 g(-1) x min(-1) (+60%); 2 MAC sevoflurane, 118+/-21 ml x 100 g(-1) min(-1) (+27%). LCBF was increased in most brain structures investigated. Correlation coefficients obtained for the relationship between LCGU and LCBF were as follows: control 0.93; 1 MAC isoflurane, 0.89; 2 MAC isoflurane, 0.71; 1 MAC sevoflurane, 0.83; 2 MAC sevoflurane, 0.59).

CONCLUSION

Mean and local cerebral blood flows were lower during sevoflurane than during isoflurane anesthesia. This difference cannot be explained by differing changes in glucose utilization because glucose utilization was decreased to the same extent in both groups.

Evolution of the bone-titanium interface on implants coated/noncoated with xenogeneic bone particles: quantitative microscopic analysis

Titanium cylinders having a sandblasted surface were implanted in holes drilled in the internal condyles of rabbit femurs. The right side received a titanium implant coated with xenogeneic bone particles and the left side received a titanium cylinder alone and was used as control. The femoral extremities were removed at 1, 2, and 3 months postsurgery and embedded undecalcified in methacrylic resins. Sections were studied by quantitative analysis and the interface contact between bone and titanium was measured at two microscopic magnifications due to the fractal dimension of this parameter. In addition the amount of bone volume in a given referent volume provided automatically by the image analyzer was obtained. No differences could be evidenced between the two series of implants, supporting the view that xenogeneic particles were ineffective in improving the attachment of bone to the implant. The bone-to-implant interface measured at the low magnification reflected the anchorage of the implant. In both series a progressive increase upon time of the bone-to-implant interface at the highest microscopic magnification evidenced the importance of late remodeling changes responsible for bone bonding and the fractal characteristics of this interface, related to surface quality of the implant responsible for stress transfer.

Osteoclast cytomorphometry in patients with femoral neck fracture

In patients with femoral neck fracture, nutritional deficiencies have been shown to be common. A low calcium diet and/or a reduced vitamin D intake have been suspected to cause secondary hyperparathyroidism responsible for increased bone turn over and bone loss. Parathyroid hormone (PTH) levels are increased in these patients, data which are in accordance with the pronounced changes observed on bone biopsies reflecting a true hyperparathyroidism. We have used a cytomorphometrical approach to characterize PTH-induced changes on the osteoclastic population. Osteoclasts were detected histochemically (by tartrate resistant acid phosphatase staining) on bone biopsies from 10 control subjects, 8 patients with primary hyperparathyroidism and 10 patients with a femoral neck fracture of osteoporotic origin. The maximum Feret's diameter of each osteoclast (Oc.Le) was determined with a semiautomatic image analyzer. In all groups, the frequency distribution of Oc.Le appeared positively skewed. In both hip fractured patients and primary hyperparathyroid patients, the mode of the distribution was higher (25-30 microns) than in controls (20-25 microns). When graphically converted on a probability graph, the osteoclastic populations appeared homogeneous and well described by a lognormal distribution in the three groups. However, osteoclasts appeared similarly enlarged in the groups of patients with primary hyperparathyroidism and with femoral neck fracture. PTH has been shown to increase both the recruitment of mononucleated precursors and their fusion into larger osteoclasts than controls. In the present study, a cytomorphometric method appeared able to identify the border line hyperparathyroidism in the hip fractured patients.

Altered trabecular architecture induced by corticosteroids: a bone histomorphometric study

Prolonged corticosteroid (CS) therapy induces osteoporosis and fractures. Osteoporosis is characterized at the histomorphometric level by reduced bone volume (BV/TV) and disruption of the three-dimensional (3D) trabecular architecture. Several stereological methods have been proposed to characterize these alterations: measurements of trabecular thickness and trabecular number, star volumes, interconnectivity index (ICI) of the bone marrow spaces, and trabecular bone pattern factor (TBP(f)). These methods were computerized with a single program running on an image analyzer to evaluate the bone changes in a series of iliac biopsies performed on 31 male patients. All of them were asthmatic and had received CS for a long period of time. BV/TV was reduced when compared with age-matched controls. In the CS-treated population, exponential relationships were obtained between bone volume and the different connectivity parameters. The various methods used to measure connectivity were well correlated. When the population was divided into two groups (BV/TV greater or less than an 11% threshold), the architectural disturbances were found to imply two mechanisms. A progressive decline in trabecular thickness was noted in both groups versus controls. Trabecular perforations were not established in the group with BV/TV> 11% with the star volume or ICI, although some alterations were detected by trabecular bone pattern factor measurement. However, perforations were revealed in the group with BV/TV < 11% by all the different methods. Perforations seemed to occur when the trabecular thickness was below 70 mu m. This strongly suggests that bone histomorphometry should take into consideration bone volume in combination with detailed 3D descriptors of the trabecular architecture. Several histological methods need to be used in combination to appreciate the 3D architecture of trabecular bone.

[New airbag-associated injuries in traffic accidents]

Experimental studies have shown that in traffic accidents with frontal impact the new airbag system can significantly reduce the incidence of severe injuries and fatal outcome. The question of whether the airbag itself induces specific patterns of injury needs further investigation. Two cases of traffic accidents with airbag protection are presented here. The first case report clearly shows the life-saving and injury-reducing effect of the airbag system in a traffic accident with frontal impact at 100 km/h. In the second case only minor injuries of the face were diagnosed initially. Hemodynamic instability occurred after 3 h of hospitalization due to rupture of the azygos vein. Analysis of the presented cases shows that, besides the well-known benefits, there are certain injury patterns that seem to be related to the use of airbags. These have not been described before. It is concluded that patients who were involved in traffic accidents with airbag deployment have to be hospitalized and followed up carefully over time, even though they are initially stable, as potentially fatal sequelae of deceleration trauma can occur later. In our opinion it is not possible to estimate the severity of airbag-associated injuries with conventional methods.

[Viral origin of Paget's disease of bone?]

The viral aetiology of Paget's bone disease was suspected by the finding, in 1974, of microcylindric paramyxovirus nucleocapsid-like inclusions in nuclei and cytoplasm of pagetic osteoclast. Paramyxovirus antigens were detected, using monoclonal antibodies, in the osteoclasts of pagetic lesions. Paramyxovirus RNA sequences were identified in Paget's bone tissue, predominantly in osteoclasts, using specific hybridization. However, these last results are conflicting because some reports failed to reproduce hybridization with Paramyxovirus. Nevertheless, Paramyxovirus could be responsible for the cytopathologic aspect of multinucleated osteoclasts for the stimulation of hyperexpression, in Paget's disease, of interleukin 6 and of c-fos oncogene known to enhance osteoclastic resorption activity.

Effects of tiludronate on bone loss in paraplegic patients

Immobilization secondary to spinal cord injury is associated with a marked and rapid atrophy of trabecular bone (disuse osteoporosis). This is due to an early increase of osteoclastic bone resorption associated with a pronounced decreased osteoblastic bone formation. Bisphosphonates are antiosteoclastic compounds and they have been effective in preventing disuse osteoporosis. However, some of them also depress osteoblastic activity and may impair the mineralization process. Tiludronate was shown effective in reducing bone resorption in several metabolic bone diseases without inducing mineralization defects. Twenty paraplegic patients (6 females and 14 males) were randomly assigned to three groups: 6 patients entered the placebo group; 7 patients received tiludronate 200 mg/day; and 7 received 400 mg/day. Histomorphometric analysis was performed on transiliac bone biopsies before and after 3 months treatment. An insignificant decrease of bone volume was observed in the placebo group and the 200 mg group. In patients receiving 400 mg/day, a slight increase was noted. Osteoid parameters changed nonsignificantly in three groups although the 400 mg group exhibited a slight tendency to decrease osteoid volume and thickness. Eroded surfaces increased in all groups. The number of osteoclasts (identified histochemically by TRAP staining) increased in the placebo group but decreased in groups receiving tiludronate. Tiludronate appears effective in reducing bone resorption without impairing bone formation in a manner that preserved bone mass and bone cell coupling.

[Electron microscopic study of a macroporous calcium phosphate ceramic implanted in an osseous site]

Cellular and tissular responses to intraosseous graft of a macroporous calcium phosphate ceramic was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Twelve specimens were implanted in 6 rabbits (tibiae), taken at day 14 after implantation and processed either for TEM (6 samples) or SEM (6 samples). As early as day 14 after implantation osteogenesis so that resorption of the newly formed bone and of the biomaterial, were observed at the surface of the ceramic, inside the macropores. Osteoblasts were clearly visible and well differentiated with abundant rough endoplasmic reticulum and large Golgi zone. The resorption processes were associated with 2 types of multinucleated cells. Based on ultrastructural observations (cellular characteristics and measurement of the microporosity) it appears that incompletely differentiated osteoclast was the major cell responsible of the biodegradation of the ceramic. These results suggest that the cellular events occurring at the surface of a macroporous calcium phosphate ceramic are similar to that observed in physiological bone remodelings.

[Biomaterials for bone filling: comparisons between autograft, hydroxyapatite and one highly purified bovine xenograft]

Bone grafts are becoming increasingly common in orthopaedics, neurosurgery and periodontology. Twenty one New Zealand rabbits were used in the present study comparing several materials usable as bone substitutes. A 4.5 mm hole was drilled in the inner femoral condyles. Holes were filled with either an autograft (from the opposite condyle), an hydroxylapatite (Bioapatite), or a highly purified bovine xenograft (T650 Lubboc). Animals were sacrificed at 1, 3 and 6 months post implantation and a quantitative analysis of newly-formed bone volume (BNF/IV) and remaining biomaterials (BMAT/IV) was done. In addition, some holes were left unfilled and served as controls. At 6 months, there was no tendency for spontaneous repair in the control animals. The autografted animals have repaired their trabecular mass and architecture within the first month. Hydroxylapatite appeared unresorbed at six months and only thin and scanty new trabeculae were observed. The xenograft induced woven bone trabeculae formation on the first month. This was associated with resorption of the material by two multinucleated cell populations. At six months, the epiphyseal architecture was restored and the biomaterial has disappeared in most cases. Xenografts appear a promising alternative to autografts and allografts, whose infectious risks and ethical problems should always be borne in mind.

Osteoclastic resorption of Ca-P biomaterials implanted in rabbit bone

The nature of the multinucleated cells involved in the resorption processes occurring inside macroporous calcium-phosphate biomaterials grafted into rabbit bone was studied using light microscopy, histomorphometric analysis, enzymatic detection of tartrate-resistant acid phosphatase (TRAP) activity, scanning, and electron microscopy. Samples were taken at days 7, 14, and 21 after implantation. As early as day 7, osteogenesis and resorption were observed at the surface of the biomaterials, inside the macropores. Resorption of both newly formed bone and calcium-phosphate biomaterials was associated with two types of multinucleated cells. Giant multinucleated cells were found only at the surface of the biomaterials; they showed a large number of nuclei, were TRAP negative, developed no ruffled border, and contained numerous vacuoles with large accumulation of mineral crystals from the biomaterials. Osteoclasts exhibited TRAP positivity and well-defined ruffled border. They were observed at the surface of both newly formed bone and biomaterials, around the implant, and inside the macropores. In contract with the biomaterials, infoldings of their ruffled border were observed between the mineral crystals, deeply inside the microporosity. The microporosity of the biomaterials (i.e., the noncrystalline spaces inside the biomaterials) increased underneath this type of cell as compared with underneath giant cells or to the depth of the biomaterials. These observations demonstrate that macroporous calcium-phosphate biomaterials implanted in bone elicit osteogenesis and the recruitment of a double multinucleated cell population having resorbing activity: giant multinucleated cells that resorb biomaterials and osteoclasts that resorb newly formed bone and biomaterials.