Hematologic safety of intraosseous blood transfusion in a swine model of pediatric hemorrhagic hypovolemia

Red cell haemolysis secondary to intraosseous (IO) blood transfusion in adult patients with major trauma: a systematic review

INTRODUCTION

Intraosseous (IO) administration of medications and blood products is accepted practice in major trauma when intravenous access is not immediately available. However, there is a concern that the high infusion pressures required for IO transfusion may increase the risk of red cell haemolysis and its associated complications. The aim of this systematic review is to synthesise the existing evidence describing the risks of red cell haemolysis in IO blood transfusion.

METHODS

We undertook a systematic search of MEDLINE, CINAHL and EMBASE using the search terms: "intraosseous transfusion" and "haemolysis". Two authors independently screened abstracts, and reviewed full-text articles against the inclusion criteria. Reference lists of included studies were reviewed and a grey literature search undertaken. Studies were assessed for risk of bias. Inclusion criteria were: all human and animal study types that reported novel data on IO-associated red cell haemolysis. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline was used.

RESULTS

Twenty-three abstracts were identified; n=9 full papers met the inclusion criteria. No further studies were identified from reference lists or grey literature. These papers included: seven large animal translational studies, a prospective and a retrospective human study. The overall risk of bias was high. One animal study with good translatability to adult patients with trauma demonstrated haemolysis. Other animal studies had methodological constraints that limit their human applicability. No haemolysis was observed in low-density flat bones (sternum), whereas haemolysis was reported in long bones (humerus, tibia). IO infusion using a three-way tap was associated with haemolysis. Conversely, pressure bag transfusion was not associated with haemolysis, but this method may result in insufficient flow rates for effective resuscitation.

CONCLUSIONS

There is a paucity of high-quality evidence surrounding the risks of red cell haemolysis in IO blood transfusion. However, evidence from one study suggests that the likelihood is increased by use of a three-way tap to administer blood transfusion to young adult male patients with trauma. Further research is needed to address this important clinical question.

PROSPERO REGISTRATION NUMBER

CRD42022318902.

Fat intravasation, fat emboli and fat embolism syndrome in adult major trauma patients with intraosseous catheters: a systematic review

INTRODUCTION

Intraosseous (IO) administration of medication, fluids and blood products is accepted practice for critically injured patients in whom intravenous access is not immediately available. However, there are concerns that high intramedullary pressures resulting from IO infusion may cause bone marrow intravasation and subsequent fat embolisation. The aim of this systematic review is to synthesise the existing evidence describing fat intravasation, fat embolism and fat embolism syndrome (FES) following IO infusion.

METHODS

A systematic search of CINAHL, MEDLINE and Embase was undertaken using the search terms "intraosseous", "fat embolism", "fat intravasation" and "fat embolism syndrome". Two authors independently screened abstracts and full texts, against eligibility criteria and assessed risk of bias. A grey literature search (including references) was undertaken. Inclusion criteria were: all human and animal studies reporting novel data on IO-associated fat emboli. This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis.

RESULTS

22 papers were identified from the search, with a further 5 found from reference lists. N=7 full papers met inclusion criteria. These papers were all translational animal studies. The overall risk of bias was high. Studies demonstrated that fat intravasation and fat embolisation are near universal after IO infusion, but of uncertain clinical significance. The initial IO flush appears to cause the highest intramedullary pressure and highest chance of fat intravasation and embolisation. No conclusions could be drawn on FES.

CONCLUSIONS

IO catheters remain a useful intervention in the armamentarium of trauma clinicians. Although their use is widely accepted, there is a paucity of evidence investigating fat embolisation in IO infusions. Despite this, pulmonary fat emboli after IO infusion are very common. The existing data are of low quality with a high risk of bias. More research is needed to address this important subject.

PROSPERO REGISTRATION NUMBER

CRD42023399333.

The Efficacy of Intraosseous Access for Initial Resuscitation in Patients with Severe Trauma: A Retrospective Multicenter Study in South Korea

Background/Objective: In patients with severe trauma, intraosseous (IO) access is an alternative when intravenous (IV) access proves challenging. However, detailed insights into its utilization patterns and effectiveness are lacking. This study aims to evaluate the use and efficacy of IO access in hemodynamically unstable patients with trauma at level-1 trauma centers in South Korea. Methods: Data from six centers over 12 months were analyzed, focusing on patients with traumatic cardiac arrest or shock. Overall, 206 patients were included in the study: 94 in the IO group and 112 in the IV group. Results: The first-attempt success rate was higher in the IO group than in the IV group (90.4% vs. 75.5%). The procedure time in the IO group was also shorter than that in the IV group. The fluid infusion rate was lower in the IO group than in the IV group; however, the use of a pressure bag with IO access significantly increased the rate, making it comparable to the IV infusion rate. Further, regarding IO access, a humeral site provided a higher infusion rate than a tibial site. Conclusions: IO access offers a viable alternative to IV access for the initial resuscitation in patients with trauma, providing advantages in terms of procedure time and first-attempt success rate. The use of a pressure bag and a humeral site for IO access afforded infusion rates comparable to those associated with IV access.

Intraosseous access in the resuscitation of patients with trauma: the good, the bad, the future

The timely restoration of lost blood in hemorrhaging patients with trauma, especially those who are hemodynamically unstable, is of utmost importance. While intravenous access has traditionally been considered the primary method for vascular access, intraosseous (IO) access is gaining popularity as an alternative for patients with unsuccessful attempts. Previous studies have highlighted the higher success rate and easier training process associated with IO access compared with peripheral intravenous (PIV) and central intravenous access. However, the effectiveness of IO access in the early aggressive resuscitation of patients remains unclear. This review article aims to comprehensively discuss various aspects of IO access, including its advantages and disadvantages, and explore the existing literature on the clinical outcomes of patients with trauma undergoing resuscitation with IO versus intravenous access.

Fat embolism after intraosseous catheters in pediatric forensic autopsies

In our center, we performed the autopsy of a child who died from drowning and presented, at autopsy, a major pulmonary fat embolism (PFE). A cardiopulmonary resuscitation (CPR) was performed, including infusion by intraosseous catheter (IIC). No other traumatic lesions and diseases classically related to a risk of PFE were detected. According to some animal studies, we considered the IIC as the only possible cause for PFE. However, we could not find literature to confirm this hypothesis in humans, especially in a pediatric population. To verify the occurrence of PFE after IIC in a pediatric population, we retrospectively selected 20 cases of pediatric deaths autopsied in our center, in which a CPR was performed, without bone fractures or other possible causes of PFE: 13 cases with IIC (group A) and 7 cases without IIC (group B). Several exclusion criteria were considered. The histology slides of the pulmonary tissue were stained by Oil Red O. PFE was classified according to the Falzi scoring system. In group A, 8 cases showed PFE: 4 cases with a score 1 of Falzi and 4 cases with a score 2 of Falzi. In group B, no case showed PFE. The difference between the two groups was statistically significant. The results of our study seem to confirm that IIC can lead to PFE in a pediatric population and show that the PFE after IIC can be important (up to score 2 of Falzi). To the best of our knowledge, our study is the first specifically focused on the occurrence of PFE after IIC in a pediatric population by using autoptic data.

Single Versus Double Anatomic Site Intraosseous Blood Transfusion in a Swine Model of Hemorrhagic Shock

BACKGROUND

Blood transfusion via single site intraosseous access is a critical modality when caring for a trauma victim that lacks intravascular access. Flow rates and potential clinical complications when utilizing two sites of intraosseous access are not well known.

MATERIALS AND METHODS

Anesthetized adult female Yorkshire swine (Sus scrofa; n = 48; 76.7 ± 1.75kg; range 66-90kg) were cannulated and then bled approximately 30% total blood volume. Swine were randomly assigned to treatment groups: single sited humerus, single sited sternum, dual sited humerus or dual sited humerus and sternum. Flow rates, hemolysis, physiologic measurements, biochemical variables, and pulmonary histologic inflammation and occlusion were contrasted between groups.

RESULTS

Dual sited intraosseous transfusion flow rates (128ml/min, 95% CI 123-132) were double the flow rates of single sites (65ml/min, 95% CI 60-70), P < .0001.Single sited humeral flow rates were greater than sternal flow rates, with respective averages of 74ml/min and 55ml/min, though not reaching statistical significance (P < 0.17). There was no significant elevation of plasma free hemoglobin in any group after transfusion as compared to baseline (P = 0.7). Groups did not significantly differ in vitals or biochemical variables. Most pulmonary specimens had some intraparenchymal fat embolism, however no animals had evidence of occlusive intra-arterial fat embolism.

CONCLUSIONS

Dual anatomic site, pressure bag driven, intraosseous blood transfusion approximately doubles flow rates without evidence of clinical complications or hemolysis. Further research using a survivability model is needed to characterize long-term complications from pressurized IO transfusions.

Emergency Transfusions

Successful emergency transfusions require early recognition and activation of resources to minimize treatment delays. The initial goals should focus on replacement of blood in a balanced fashion. There is an ongoing debate regarding the best approach to transfusions, with some advocating for resuscitation with a fixed ratio of blood products and others preferring to use viscoelastic assays to guide transfusions. Whole-blood transfusion also is a debated strategy. Despite these different approaches, it generally is accepted that transfusions should be started early and crystalloid infusions limited. As hemodynamic stability is restored, endpoints of resuscitation should be used to guide the resuscitation.

Intraosseous access in the resuscitation of trauma patients: a literature review

PURPOSE

Intraosseous (IO) catheters continue to be recommended in trauma resuscitation. Their utility has recently been debated due to concerns regarding inadequate flow rates during blood transfusion, and the potential for haemolysis. The objective of this review was to examine the evidence for intraosseous catheters in trauma resuscitation, and to highlight areas for future research.

METHODS

A PubMed and Embase search for articles published from January 1990 to August 2018 using the terms ("intra-osseous access" or "intraosseous access" or "IO access") AND trauma was performed. Original articles describing the use of an IO catheter in the resuscitation of one or more trauma patients were eligible. Animal, cadaveric studies and those involving healthy volunteers were excluded.

RESULTS

Nine studies, comprising of 1218 trauma patients and 1432 device insertions, were included. The insertion success rate was 95% and the incidence of complications 0.9%. Flow-rate data and evidence of haemolysis were poorly reported.

CONCLUSION

Intraosseous catheters have high insertion success rates and a low incidence of complications in trauma patients. Existing evidence suggests that IO transfusion is not associated with haemolysis, however, further studies in humans are needed. There is a paucity of flow rate data for blood transfusion via IO catheters in this population, although much anecdotal evidence advocating their use exists.

Investigating the physiology of normothermic ex vivo heart perfusion in an isolated slaughterhouse porcine model used for device testing and training

Background

The PhysioHeart™ is a mature acute platform, based isolated slaughterhouse hearts and able to validate cardiac devices and techniques in working mode. Despite perfusion, myocardial edema and time-dependent function degradation are reported. Therefore, monitoring several variables is necessary to identify which of these should be controlled to preserve the heart function. This study presents biochemical, electrophysiological and hemodynamic changes in the PhysioHeart™ to understand the pitfalls of ex vivo slaughterhouse heart hemoperfusion.

Methods

Seven porcine hearts were harvested, arrested and revived using the PhysioHeart™. Cardiac output, SaO2, glucose and pH were maintained at physiological levels. Blood analyses were performed hourly and unipolar epicardial electrograms (UEG), pressures and flows were recorded to assess the physiological performance.

Results

Normal cardiac performance was attained in terms of mean cardiac output (5.1 ± 1.7 l/min) and pressures but deteriorated over time. Across the experiments, homeostasis was maintained for 171.4 ± 54 min, osmolarity and blood electrolytes increased significantly between 10 and 80%, heart weight increased by 144 ± 41 g, free fatty acids (− 60%), glucose and lactate diminished, ammonia increased by 273 ± 76% and myocardial necrosis and UEG alterations appeared and aggravated. Progressively deteriorating electrophysiological and hemodynamic functions can be explained by reperfusion injury, waste product intoxication (i.e. hyperammonemia), lack of essential nutrients, ion imbalances and cardiac necrosis as a consequence of hepatological and nephrological plasma clearance absence.

Conclusions

The PhysioHeart™ is an acute model, suitable for cardiac device and therapy assessment, which can precede conventional animal studies. However, observations indicate that ex vivo slaughterhouse hearts resemble cardiac physiology of deteriorating hearts in a multi-organ failure situation and signalize the need for plasma clearance during perfusion to attenuate time-dependent function degradation. The presented study therefore provides an in-dept understanding of the sources and reasons causing the cardiac function loss, as a first step for future effort to prolong cardiac perfusion in the PhysioHeart™. These findings could be also of potential interest for other cardiac platforms.

Safety of Pressurized Intraosseous Blood Infusion Strategies in a Swine Model of Hemorrhagic Shock

BACKGROUND

Current guidelines support intraosseous access for trauma resuscitation when intravenous access is not readily available. However, safety of intraosseous blood transfusions with varying degrees of infusion pressure has not been previously characterized.

MATERIALS AND METHODS

Adult female Yorkshire swine (Sus scrofa; n = 36; mean (M): 80 kg, 95% CI: 78-82 kg) were cannulated and then bled approximately 30% total blood volume. Swine were randomly assigned to proximal humerus intraosseous blood infusion with either Rapid Infuser, or Pressure Bag, or Push-Pull methods (n = 12 each). Flow rates, infusion pressures, vitals, biochemical variables, and pulmonary and renal tissue pathology were contrasted between groups.

RESULTS

Flow rates were greater for the Push-Pull strategy than Pressure Bag (96.5 mL/min versus 72.6 mL/min, P = 0.02) or Rapid Infuser (96.5 mL/min versus 60 mL/min, P = 0.002) strategies. The pressures generated during the Push-Pull transfusion (3058 mmHg) were greater than the other strategies (≤360 mmHg). After the observation period, plasma-free hemoglobin levels were higher in the Push-Pull strategy than in the Rapid Infuser (40 mg/dL versus 12 mg/dL, P = 0.02) or Pressure Bag (40 mg/dL versus 12 mg/dL, P = 0.01). Groups did not significantly differ in vitals, biochemical variables, or tissue pathology.

CONCLUSIONS

Push-Pull conferred the highest flow rates, but with higher infusion pressures and evidence of intravascular hemolysis. Rapid Infuser and Pressure Bag infusions had no increase from baseline in plasma-free hemoglobin. Pressure Bag infusion was noted to confer an advantage in flow rates over Rapid Infuser. Intraosseous blood transfusion with pressure bags can safely bridge toward central access in the early phases of trauma resuscitation.

Emergency sternal intraosseous access for warm fresh whole blood transfusion in damage control resuscitation

BACKGROUND

Intraosseous (IO) vascular access is increasingly used as an emergency tool for achieving access to the systemic circulation in critically ill patients. The role of IO transfusion of blood in damage control resuscitation is however questionable due to possible inadequate flow rate and hemolysis. Some experts claim that IO transfusion is contraindicated. In this study, we have challenged this statement by looking at flow rates of autologous fresh whole blood reinfusion and hemolysis using two of the commonly used Food and Drug Administration-approved and Conformité Européenne (CE)-marked sternal needles. Additionally, the success rate of sternal access between the two devices is evaluated.

METHODS

Volunteer professional military personnel, were enrolled prospectively in a nonrandomized observational study design. We collected 450 mL of autologous whole blood from each participant. Participants were divided into the following three groups of 10: Tactically Advanced Lifesaving IO Needle (T.A.L.O.N.) IO, FAST1 IO, and intravenous group. The reinfusion was done by gravity only. Blood sampling was performed before blood collection and 30 minutes after reinfusion. Investigation of hemolysis was performed by measurements of haptoglobin and lactate dehydrogenase. Success rate was evaluated by correct aspiration of bone marrow.

RESULTS

Median reinfusion rate was 46.2 mL/min in the FAST1 group, 32.4 mL/min in the T.A.L.O.N. group, and 74.1 mL/min in the intravenous group. Blood samples from all participants were within normal ranges. There was no statistically significant difference in haptoglobin and lactate dehydrogenase between the groups. In the FAST1 group, 1 (9%) of 11 procedures failed. In the T.A.L.O.N. group, 4 (29%) of 14 procedures failed.

CONCLUSION

Although preferable, achieving peripheral venous access in the bleeding patient is a major problem. Our findings suggest that fresh whole-blood transfusion through the IO route is safe, reliable, and provide sufficient flow for resuscitation.

LEVEL OF EVIDENCE

Therapeutic/Care management study, level III.

Challenging the dogma of traumatic cardiac arrest management: a military perspective

Attempts to resuscitate patients in traumatic cardiac arrest (TCA) have, in the past, been viewed as futile. However, reported outcomes from TCA in the past five years, particularly from military series, are improving. The pathophysiology of TCA is different to medical causes of cardiac arrest, and therefore, treatment priorities may also need to be different. This article reviews recent literature describing the pathophysiology of TCA and describes how the military has challenged the assumption that outcome is universally poor in these patients.

The versatility of intraosseous vascular access in perioperative medicine: a case series

Intraosseous vascular access is a time-tested procedure that is reemerging in popularity. This is primarily a result of the emphasis on intraosseous access in the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Advanced Cardiac Life Support. Modern intraosseous insertion devices are easy to learn and use, suggesting the possibility of use beyond the resuscitation setting. We present a case series of recent intraosseous insertions for a variety of indications by anesthesiologists at our institution to demonstrate the potential utility of this alternative access technique.

Fat Intravasation from Intraosseous Flush and Infusion Procedures

STUDY HYPOTHESIS

The primary study objective was to delineate the procedural aspects of intraosseous (IO) infusions responsible for fat intravasation by testing the hypothesis that the fat content of effluent blood increases during IO infusions.

METHODS

IO cannulas were inserted into the proximal tibiae of 35 anesthetized swine (Sus scrofa, 50.1 ± 3.5 kg) and intravasated fat was assessed using a lipophilic fluoroprobe (Nile red) and by vascular ultrasound imaging. Effluent blood bone marrow fat was assessed at baseline, during flush, and with regimens of controlled infusion pressures (73-300 mmHg) and infusion flow rates (0.3-3.0 mL per second). Fat intravasation was also assessed with IO infusions at different tibial cannulation sites and in the distal femur. In 7 animals, the lipid uptake of alveolar macrophages and lung tissue assessed for fat embolic burden using oil red O stain 24 hours post infusion. Additionally, bone marrow shear-strain was assessed radiographically with IO infusions.

RESULTS

Fat intravasation was observed during all IO infusion regimens, with subclinical pulmonary fat emboli persisting 24 hours post infusion. It was noted that initial flush was a significant factor in fat intravasation, low levels of intravasation occurred with infusions ≤300 mmHg, fat intravasation and bone marrow shear-strain increased with IO infusion rates, and intravasation was influenced by cannula insertion site. Ultrasound findings suggest that echogenic particles consistent with fat emboli are carried in fast and slow venous blood flow fields. Echo reflective densities were observed to rise to the nondependent endovascular margins and coalesce in accordance with Stoke's law. In addition, ultrasound findings suggested that intravasated bone marrow fat was thrombogenic.

CONCLUSION

Results suggest that in swine the intravasation of bone marrow fat is a common consequence of IO infusion procedures and that its magnitude is influenced by the site of cannulation and infusion forces. Although the efficacy and benefits of IO infusions for emergent care are well established, emergency care providers also should be cognizant that infusion procedures affect bone marrow fat intravasation.

Recovery of fibrinogen concentrate after intraosseous application is equivalent to the intravenous route in a porcine model of hemodilution

BACKGROUND

Fibrinogen concentrate is increasingly considered as a hemostatic agent for trauma patients experiencing bleeding. Placing a venous access is sometimes challenging during severe hemorrhage. Intraosseous access may be considered instead. Studies of intraosseous infusion of coagulation factor concentrates are limited. We investigated in vivo recovery following intraosseous administration of fibrinogen concentrate and compared the results with intravenous administration.

METHODS

This study was performed on 12 pigs (mean [SD] body weight, 34.1 [2.8] kg). Following controlled blood loss (35 mL/kg) and fluid replacement with balanced crystalloid solution, intraosseous (n = 6) administration of fibrinogen concentrate (80 mg per kilogram of bodyweight) in the proximal tibia was compared with intravenous (n = 6) administration of the same dose (fibrinogen infusion time approximately 5 minutes in both groups). The following laboratory parameters were assessed: blood cell count, prothrombin time index, activated partial thromboplastin time, and plasma fibrinogen concentration (Clauss assay). Coagulation status was also assessed by thromboelastometry.

RESULTS

All tested laboratory parameters were comparable between the intraosseous and intravenous groups at baseline, hemodilution, and 30 minutes after fibrinogen concentrate administration. In vivo recovery of fibrinogen was also similar in the two groups (89% [23%] and 91% [22%], respectively). There were no significant between-group differences in any of the thromboelastometric parameters. Histologic examination indicated no adverse effects on the tissue surrounding the intraosseous administration site.

CONCLUSION

This study suggests that intraosseous administration of fibrinogen concentrate results in a recovery of fibrinogen similar to that of intravenous administration. The intraosseous route of fibrinogen concentrate could be a valuable alternative in situations where intravenous access is not feasible or would be time consuming.

LEVEL OF EVIDENCE

Prospective, randomized, therapeutic feasibility study in an animal model, level V.

Vascular Access in Resuscitation

Intraosseous vascular access is a time-tested procedure which has been incorporated into the 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation. Intravenous access is often difficult to achieve in shock patients, and central line placement can be time consuming. Intraosseous vascular access, however, can be achieved quickly with minimal disruption of chest compressions. Newer insertion devices are easy to use, making the intraosseous route an attractive alternative for venous access during a resuscitation event. It is critical that anesthesiologists, who are often at the forefront of patient resuscitation, understand how to properly use this potentially life-saving procedure.

[Intraosseous infusion. An important technique also for paediatric anaesthesia]

Timely establishment of venous access in infants and toddlers can prove a particularly challenging task. Since the 1940s the technique of intraosseous infusion has established itself as a valuable alternative means for rapid, efficient and safe delivery of drugs and fluids to critically ill children. Whereas international guidelines for paediatric emergency medical care have assigned intraosseous infusion a high priority, most anaesthetists utilize this well-proven technique with great reluctance. This article describes the technique of intraosseous infusion, introduces two different cannulation systems, and discusses its potential indications in paediatric anaesthesia, based on current emergency medical care guidelines as well as some of our own case studies. In particular, children with acutely life-threatening conditions, such as circulatory arrest, laryngospasm, acute airway haemorrhage, hypovolaemic shock or hypothermia secondary to extensive burns, should receive an intraosseous cannula if intravenous access cannot be rapidly established. Future discussion may reveal whether a transiently inserted intraosseous infusion would also be indicated if the child with difficult or impossible venous access presents without acute life-threatening conditions for anaesthesia. Successful application of the intraosseous infusion technique requires immediate access to the necessary equipment, intensive education, continuous training and clear guidelines for its application in an anaesthesia department.

Coagulopathy in the equine critical care patient

Disseminated intravascular coagulation (DIC) is a clinicopathologic syndrome resulting from a multitude of underlying causes that manifests itself clinically as hemostatic/fibrinolytic failure. There is much debate on the definition, diagnosis, and treatment of DIC, a situation that is most likely the result of the multifaceted clinical presentation of the syndrome and the fact that patient outcome is often influenced by the underlying disease process. The fact that DIC increases morbidity and mortality in critical care patients is well established, but the exact mechanism of what specifically occurs on a microvascular level is still often argued.

Intraosseous infusion and pulmonary fat embolism

OBJECTIVES: To determine the incidence of pulmonary fat embolism after the intraosseous (IO) infusion of normal saline and drugs and to determine whether pulmonary capillary blood is a predictor of lung fat embolism. DESIGN: A randomized, prospective, animal study. SETTING: Animal research laboratory of a university hospital. SUBJECTS: Twenty-eight mixed breed piglets (average weight 30.9 kg). Interventions and Methods: Animals were anesthetized, intubated, mechanically ventilated, and instrumented. IO needles were placed in the tibial bone. Animals were assigned to one of four groups: Group 1 received fluid (20 mL/kg) under 300 mm Hg pressure (n = 6); group 2 received fluid (20 mL/kg) at free flow under gravity (n = 6); group 3 received 100 mL of fluid over 20 mins (n = 8); and group 4 received 100 mL of fluid over 7 mins (n = 8). MEASUREMENTS AND MAIN RESULTS: Buffy coat samples were obtained from pulmonary arterial catheter in the occluded position at baseline, after IO needle placement, and at the end of infusion. Lung specimens (both upper and lower lobes) were obtained at the end of the infusion. Specimens were stained with oil red O and graded for fat emboli by a pathologist blinded to experimental conditions. Fat emboli (one to three emboli per high power field) were found in about 30% of the lung specimens. The difference in number of fat emboli between groups was not statistically significant. Buffy coat stains yielded fat emboli, which were distributed sporadically in all groups. CONCLUSION: Fat embolism is common; however, the method of IO fluid administration does not influence the number of emboli. Our study therefore implies that the risk of fat embolization is of concern, but its clinical relevance is unclear. Until the clinical significance of pulmonary fat emboli and the prevalence of fat emboli syndrome are delineated more precisely, the IO route is an effective but not necessarily safe route for delivery of fluids and drugs.

Intraosseous infusions in the adult

Intraosseous infusions are used in children when intravenous access is difficult or impossible. The intraosseous route is also applicable to adults, but is not widely used. In this article, the anatomy and physiology of bone marrow is described and techniques and sites of intraosseous needle placement are discussed. Fluid and drug administration by the intraosseous route is also discussed. Intraosseous anaeasthesia and diagnostic testing is possible through intraossoeous needles. Potential complications and contraindications are considered.

Fat embolism with the use of intraosseous infusion during cardiopulmonary resuscitation

The objective of this prospective study was to assess the incidence and magnitude of fat emboli after cardiopulmonary resuscitation and intraosseous infusions. An animal laboratory at a university center was used to study 33 mixed-breed piglets. The piglets underwent hypoxic cardiac arrest followed by chest compressions and mechanical ventilation for a minimum of 30 minutes. The animals were divided in groups: group 1 (n = 5), which had no intraosseous cannulas, group 2 (n = 6), which had intraosseous cannulas with infusion, groups 3 (n = 6), 4 (n = 6), and 5 (n = 8), which had intraosseous cannulas with infusion of epinephrine, normal saline, and sodium bicarbonate respectively, and group 6 (n = 2), which was a sham group with no intraosseous cannulas and no cardiopulmonary resuscitation. At cessation of cardiopulmonary resuscitation, representative lung samples were collected from upper and lower lobes of each lung and observed for fat globules and bone marrow elements. Fat globules were seen in the peribronchial blood vessels and intravascular areas throughout all lung fields of groups 1 through 5. There was no difference in appearance or distribution of fat globules among the 5 treatment groups. Analysis of variance showed no statistical significance (P < 0.05) within or among groups 1 through 5. The use of the intraosseous cannula for infusion of emergency drugs and fluids did not increase the magnitude of fat embolization over cardiopulmonary resuscitation alone in this animal model. The benefits of using this procedure in critically ill children as a means of rapid vascular access for resuscitation is well established. However, the risk of fat embolism in this population needs further study.