a b s t r a c t

Purpose: Purposes of this study were to compare tibial intraosseous (TIO) and intravenous (IV) administration of vasopressin relative to return of spontaneous circulation (ROSC) and time to ROSC in an adult swine cardiac ar- rest model. In addition, the purposes were to compare the concentration maximum (Cmax), time to maximum concentration (Tmax), and odds of ROSC.

Methods: This was a between-subjects, prospective experimental study. Yorkshire swine (N = 21) were random- ly assigned to 1 of 3 groups: TIO, IV, or control groups. The swine were anesthetized and instrumented, and then cardiac arrest was induced and sustained for 2 minutes. Cardiopulmonary resuscitation was initiated and contin- ued for 2 minutes. Vasopressin was then administered via the TIO or IV route. Blood samples were collected for 4 minutes to determine the Cmax and Tmax of vasopressin. Concentration maximum and Tmax were calculated by use of liquid chromatography with mass spectrometry.

Results: There was no difference in ROSC between the TIO and IV groups (P = .63). The Cmax of vasopressin was significantly higher in the IV group compared to the TIO group (P = .017). However, there was no significant dif- ference in ROSC, time to ROSC, or Tmax between groups (P N .05). All subjects had ROSC in both the IV and TIO groups, and none had ROSC in the control group. There was 225 times greater chance of survival for both the IV and TIO groups compared to the control group.

Conclusion: The data support that the TIO is an effective route for vasopressin in a cardiac arrest model.

1. Introduction

Incidence of death attributable to cardiovascular disease has de- clined over the past 15 years but still accounts for 1 of every 3 deaths in the United States [1]. Cardiovascular disease continues to be the lead- ing cause of death in the United States. Cardiac arrest remains the lead- ing cause of morbidity and mortality with more than 900 occurrences daily in the United States [1,2]. When a patient is in cardiac arrest, it is essential to establish rapid and reliable vascular access. The chances of survival are worsened for every minute that resuscitation drugs are de- layed [3-6]. Often in a Cardiac arrest scenario, the patient’s veins have collapsed preventing vascular access. This makes the procedure not only difficult but also very time consuming, which could delay the ad- ministration of lifesaving drugs.

* Corresponding author. Tel.: +1 210 849 7364.

E-mail addresses: [email protected] (D. Johnson), [email protected] (K. Giles), [email protected] (A. Acuna), [email protected] (C. Saenz), [email protected] (M. Bentley), [email protected] (C. Budinich).

¹ At the time of the study, individual was a faculty member at the US Army Graduate Program in Anesthesia Nursing.

² At the time of the study, individual was a Graduate student at the US Army Graduate Program in Anesthesia Nursing.

If Intravenous access is unobtainable, many authorities recom- mend that the intraosseous route be used and can provide access to a rapidly obtained, noncollapsible, venous plexus [7,8]. The American Heart Association recommends that, if IV access cannot be ob- tained in a cardiac arrest situation, drugs should be administered via the IO route [3,9]. However, these recommendations are based on limited data. Two main drugs are used for patients in cardiac arrest: epineph- rine and vasopressin. Controversy exists as to which drug is more effec- tive. Epinephrine produces beneficial effects in patients during cardiac arrest primarily because of its ?-adrenergic effects which increase coronary perfusion pressure and cerebral perfusion pressure during car- diopulmonary resuscitation (CPR). However, the drug increases myo- cardial work and reduces subendocardial perfusion [10]. These potentially deleterious ?-effects have led to the use of alternative vaso- pressors specifically vasopressin. Vasopressin is a powerful vasocon- striction that acts by stimulation of smooth muscle V1 receptors but has neither chronotropic nor inotropic effects on the heart. It has a lon- ger half-life than epinephrine. Vasopressin has been speculated to be more effective than epinephrine based on the finding that the vasopres- sin levels have been found to be significantly higher in successfully re- suscitated cardiac arrest patients [11]. However, several randomized control trials have demonstrated no difference between vasopressin

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430 D. Johnson et al. / American Journal of Emergency Medicine 34 (2016) 429-432

and epinephrine in return of spontaneous circulation (ROSC), survival to discharge, or neurologic outcomes [11-14]. Link et al [10] in a review of evidence indicate that there are no significant differences in ROSC be- tween vasopressin and epinephrine use in cardiac arrest. Likewise, Larabee et al [15] in a systematic review concluded that vasopressin is equivalent for use as an initial vasopressor when compared to epineph- rine during resuscitation from cardiac arrest. Mentzelopoulos et al [16] performed a meta-analyses comparing vasopressin and epinephrine and concluded that ROSC was higher in the vasopressin group than in an epinephrine group but only in patients with witnessed arrest. Repeated injections of either vasopressin or epinephrine during prolonged advanced cardiac life support resulted comparable survival [16]. However, there may be differences in outcome with IO injections of these drugs. Intraosseous injection of epinephrine may cause vaso- constriction and impede the delivery of the drug into the systemic circu- lation. In fact, Voelckel et al [17] found that bone marrow blood flow was nearly absent after high-dose epinephrine but was maintained after high-dose vasopressin.

Bone marrow changes structure and composition with age. At birth, bone contains primarily red marrow, which is highly vascularized. After 5 years of age, the red marrow is replaced by yellow marrow, which in- cludes the tibia. By adulthood, red marrow is found primarily in the ster- num, proximal femur, humerus, and skull. Intraosseous site selection may be important given the variability of blood flow to these different types of marrow [5,18]. We speculated that when a patient is in cardiac arrest, tibial IO (TIO) compared to IV administration of vasopressin would result in lower concentrations, lower maximum plasma concen- trations (Cmax), and the time it takes to reach maximum concentration in plasma (Tmax). Furthermore, we reasoned that ROSC would be less and Time to achieve ROSC would be more for IO compared to IV administration.

No studies have compared the IV and TIO routes of vasopressin ad- ministration in an adult cardiac arrest model to determine the differ- ences among 6 variables: ROSC, time to ROSC, serum concentration, Cmax, and Tmax.

The purposes of this study were to compare ROSC and time to ROSC in TIO, IV, and CPR + defibrillation groups in an adult swine cardiac arrest model. In addition, the purposes were to compare the serum concentration, pharmacokinetics (Cmax and Tmax), and the odds of survival by group when vasopressin is ad- ministered by TIO and IV routes.

The following research questions guided the study:

1. Are there statistically significant differences in ROSC and time to reach ROSC between the groups?
2. Are there statistically significant differences in odds of ROSC by group?
3. Are there statistically significant differences in Cmax and Tmax of serum vasopressin when administered via tibial IO and IV routes?
4. Are there statistically significant differences in mean concentra- tion of vasopressin over 4 minutes when administered via tibial IO and IV routes?
5. Methods

This study was a prospective, between-groups, experimental design approved by the TriService Research Laboratory Institutional Animal Care and Use Committee (Navy-13-14). The animals received care in compliance with the Animal Welfare Act and the Guide to the Care and Use of Laboratory Animals. Twenty-one Yorkshire cross swine (Sus scrofa) were randomly assigned to 3 groups: TIO (n = 7), peripher- al IV (n = 7), and CPR+ defibrillation control (n = 7). To avoid any var- iability in subjects, the swine were purchased from the same vendor, approximately the same size, and all male sex. Male swine were used to avoid any potential hormonal effects. Subjects weighing between

60 and 80 kg were used as this range represents the average weight of an adult, male human [19].

Procedures

Food was withheld after midnight before the experiment. Water was allowed ad libitum up to the time of the experiment. Thirty minutes be- fore instrumentation, the swine were sedated, anesthetized, and placed on mechanical ventilation. Anesthesia was induced with an intramuscu- lar injection of Telazol (4-8 mg/kg) and inhaled isoflurane (4%-5%). The peripheral auricular vein was chosen because it is most comparable to the antecubital vein in humans [20]. The auricular peripheral IV was used as the site of vasopressin administration for the IV experimental group. After placement of an endotracheal tube, we reduced the isoflurane concentration to a maintenance dose (1%-2%) until cardiac arrest was induced.

The animals were ventilated at 8 to 10 mL/kg tidal volume with a Narkomed 3A anesthesia machine (Drager, Telford, PA). Respiratory rate was set at 10 to 14 breaths per minute. In all groups, a 20-gauge catheter was placed in the left carotid artery using a cut-down tech- nique. The arterial catheter was connected to a Phillips MP 50 system (Phillips Healthcare, Andover, MA) for continuous monitoring of systol- ic blood pressure (SBP), diastolic blood pressure, and mean arterial pressure. The Arterial line was also connected to a Vigileo Hemodynamic Monitor (Edwards Lifesciences, Irvine, CA) for continuous monitoring of cardiac output and stroke volume. The Phillips MP 50 system was also used to monitor heart rate and rhythm, pulse oximetry, end-tidal car- bon dioxide, and rectal temperature. Normothermia was maintained using a forced air-warming blanket to maintain body temperature greater than or equal to 37.0?C.

Swine in the TIO group had a 15 gauge x 45 mm EZ-IO device (Teleflex Medical, San Antonio, TX) inserted in the tibia. Placement of the TIO needle was verified by aspiration of bone marrow and ease of ir- rigation with 10 mL of normal saline. Swine were stabilized for 5 mi- nutes, and then cardiac arrest was induced using the transcutaneous electrical induction technique. Specifically, a needle was inserted at the left sternal border in the second intercostal space at a depth of

3.25 cm. A second needle was inserted immediately caudal to the xi- phoid process at a depth of 6 cm. Lead wires were attached to both needles. One lead wire was connected to the negative pole of three 9- V batteries connected in series. The other lead wire was rapidly tapped on the positive pole placing the swine into ventricular fibrillation. cardi- ac arrest was operationally defined as any nonperfusing arrhythmia resulting in a SBP less than or equal to 60 mm Hg. The subjects remained in arrest for 2 minutes without intervention. Most of the swine had ven- tricular fibrillation within 10 seconds, and all achieved arrest within 30 seconds. Cardiopulmonary resuscitation was initiated at 2 minutes postarrest using the “Thumper” mechanical compression Device, Model 1008 (Michigan Instruments, Grand Rapids, MI). The device was used to reproducibly compress the sternum to a predetermined depth of 2 in and a rate of hundred compressions per minute. Ventila- tions were administered at 12 breaths per minute.

At 4 minutes postarrest, the investigators administered 40 U of vaso- pressin, the current standard dose in humans, to the IV and TIO groups according to group assignment. The drug was followed by 10 mL of normal saline flush for both groups. We did note that there was re- sistance in the IO group and more force had to be used to inject both va- sopressin and NS at a similar rate as the IV administration. The control group did not receive vasopressin. Cardiopulmonary resuscitation con- tinued for an additional 4 minutes. During this 4 minutes, the re- searchers collected arterial blood samples from the carotid arterial line for pharmacokinetic analysis. Seven samples were collected at 30, 60, 90, 120, 150, 180, and 240 seconds. The analysis of plasma vasopres- sin levels was performed by liquid chromatography with liquid chroma- tography-mass spectrometry and liquid chromatography-tandem mass spectrometry considered to be the criterion standard in

D. Johnson et al. / American Journal of Emergency Medicine 34 (2016) 429-432 431

pharmacokinetic research [21]. At 8 minutes postarrest, the swine were defibrillated with 360 J. Defibrillation was repeated at 2-minute inter- vals up to 24 minutes or until ROSC was achieved. Return of spontane- ous circulation was defined as a SBP of at least 60 mm Hg and a palpable pulse for at least 20 minutes. Anesthesia, as tolerated by the animal, was immediately resumed.

Statistical analyses

Power analysis was performed using G*Power 3.1 for Windows (Heinrich Heine University, Dusseldorf, Germany). Statistical analyses were accomplished by the use of IBM SPSS Statistics for Windows v.

21.0 (IBM Corp, Armonk, NY). We used a multivariate analysis of vari- ance (MANOVA) to determine if there were any differences in the pre- test data, serum concentration, Cmax, and Tmax by group. A Fisher exact was used to determine if there were significant differences in ROSC by group. We also compared the chances of survival by group by using an odds ratio. An independent t test was used to determine if there were significant differences in time to ROSC between the TIO and IV groups. A repeated analysis of variance was used to determine if there were significant differences in concentration of vasopressin over time between the groups.

1. Results

The investigators used data from similar, previous studies and calcu- lated a large effect size of 0.6 [5,22,23]. Based on an effect size of 0.6, an ? of .05, and a power of .80, we determined that we needed 21 swine (n = 7 per group). A MANOVA indicated that there were no significant differ- ences in the groups relative baseline blood gases, weight, SBP, diastolic blood pressure, heart rate, mean arterial pressure, cardiac output, stroke volume, or temperature indicating that the groups were equivalent on these variables (P N .05). We evaluated pairwise outcomes of ROSC using Fisher exact test (FET) and odds ratio and found that there was no significant difference in the TIO and IV groups (FET, P = .63). There was a significant difference for both the IV and TIO groups compared to the control (FET, P = .001). (See Table 1 for a summary of subjects that achieved ROSC and those that did not.)

The odds of survival for both the TIO and IV groups in comparison with the control group (adjusting cells upwards 0.5 to account for zeros) was 225.00, 95% confidence interval (3.926-12895.826). There was no difference between the TIO and IV groups: both had 7 of 7 achieve ROSC. The means and SDs for the time to ROSC were as follows: IV group (mean, 541 +- 226) and the TIO group was (mean, 499 +- 110). An independent t test indicated that there were no significant differ- ences between the IV and TIO groups relative to the time to ROSC (P = .66). A MANOVA with univariate testing indicated that there was a significant difference in the Cmax in the groups but no difference in Tmax (see Table 2 for a summary of Cmax and Tmax). The results are summarized in means and SDs.

The mean concentration of vasopressin was consistently higher in the IV compared to the TIO group. A repeated analysis of variance indi- cated that there was a significant difference at the 60-, 90-, and 120- second times. The results are summarized in Table 3 and in the Figure.

1. Discussion

The purpose of this study was to compare the effects of vasopressin ad- ministrated via the IV and TIO routes on ROSC, time to ROSC, odds of

Table 1

Summary of subjects achieving ROSC

	IV	TIO	Control
ROSC	7	7	0
No ROSC	0	0	7

Table 2

Summary of Cmax in pg and Tmax in minutes by group

Group	Cmax	P	Tmax	P
IV	70717 +- 28118	.017?	1.7 +- 0.70	.20
TIO	38630 +- 12641		2.4 +- 1.2

* Significant at the .05 level.

survival, mean concentration, Cmax, and Tmax in a cardiac arrest swine model. We found that there was no difference between the TIO and IV groups relative to ROSC and time to ROSC, odds of survival, and Tmax. These results are consistent with the findings of Johnson et al [23] who also found the same results relative to humerus IO compared to IV admin- istration of epinephrine. Conversely, we found that the IV group had signif- icantly higher Cmax compared to the TIO group, whereas Johnson et al found no difference between the groups. We found that the concentration of vasopressin over time was consistently higher in the IV group compared to the TIO group, whereas Johnson et al found the humerus IO group was higher at the 30-second time compared to the IV group [23]. In addition, our results are different from the findings of Von Hoff et al [24] who found that there were no statistically significant differences between the Cmax after IO (Iliac crest) and IV administration of morphine sulfate in humans. We found that the IV group had significantly higher Cmax. Per- haps the reason for differences in the findings of the current study is be- cause both the iliac crest and humerus have red marrow (more vascular) compared to the tibial that has yellow marrow (less vascular).

Our results are consistent with the findings of Burgert et al [22] who found that the Cmax of the TIO group was less than that of the IV group when epinephrine was administered in a cardiac arrest model. Our re- sults are also consistent with Hoskins et al and Wenzel et al who found that IV administration of drugs resulted in higher Cmax compared to tibial IO administration [5,22,25]. Our study supports the findings of Wenzel et al [25] who found that vasopressin administration in a swine model of Pediatric cardiac arrest resulted in a comparable rate of ROSC compared to IV vasopressin. Voelckel et al [17] found that blood flow decreased significantly during hemorrhage shock which they speculated would impair absorption of drugs administered by the IO route in a pediatric model. The current study adds to the body of knowledge in that we investigated not only the pharmacokinetics but also ROSC and time to ROSC in an adult cardiac arrest model.

Limitations

This study was performed on swine, and the results of the study may not be generalizable to humans; however, the bone and cardiovascular system are comparable to humans [26,27]. In addition, the swine that achieved ROSC were only monitored for 20 minutes after ROSC and, hence, may not be predictive of long-term survivability or neurologic outcomes.

Table 3

Means, SD, and P values of mean concentration of vasopressin

Time in seconds	Group	Mean	SD	P
30	IV	18798	35953	.20
60	Tibial IO IV	502 39738	920 27887	.049?
Tibial IO		13557	15015
90	IV	56727	13029	.003?
	Tibial IO	27831	15424
120	IV	58911	26313	.044?
	Tibial IO	33907	13273
150	IV	55661	28515	.10
	Tibial IO	34224	14429
180	IV	50635	27065	.14
	Tibial IO	32670	13682
240	IV	40315	20573	.98
	Tibial IO	28113	11619

* Significant at the .05 level.

432 D. Johnson et al. / American Journal of Emergency Medicine 34 (2016) 429-432

70000

Vasopressin in pg per mL

60000

50000

40000

30000

20000

10000

0

Mean Conctration over Seconds

30 60 90 120 150 180 240

non-Shockable rhythms: retrospective analysis of large in-hospital data registry. BMJ 2014;348:g3028.

1. Rea TD, Eisenberg MS, Sinibaldi G, White RD. Incidence of EMS-treated out-of- hospital cardiac arrest in the United States. Resuscitation 2004;63(1):17-24.
2. Rea TD, Eisenberg MS, Sinibaldi G, White RD. Incidence of out-of-hospital cardiac arrest. Am J Cardiol 2004;93(12):1455-60.
3. Neumar RW, Eigel B, Callaway CW, Estes III NA, Jollis JG, Kleinman ME, et al. American Heart Association Response to the 2015 Institute of Medicine Report on

IV strategies to improve Cardiac arrest survival. Circulation 2015;132(11):1049-70.

1. Link MS, Berkow LC, Kudenchuk PJ, Halperin HR, Hess EP, Moitra VK, et al. Part 7:

IO adult advanced cardiovascular life support: 2015 American Heart Association Guide- lines update for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation 2015;132(18 Suppl. 2):S444-64.

1. Lindner KH, Dirks B, Strohmenger HU, Prengel AW, Lindner IM, Lurie KG. Randomised comparison of epinephrine and vasopressin in patients with out-of- hospital ventricular fibrillation. Lancet 1997;349(9051):535-7.
2. Ong ME, Tiah L, Leong BS, Tan EC, Ong VY, Tan EA, et al. A randomised, double-blind,

multi-centre trial comparing vasopressin and adrenaline in patients with cardiac ar- rest presenting to or in the emergency department. Resuscitation 2012;83(8):

Figure. Mean concentration of vasopressin over time by group.

Conclusion

Time is of the essence when treating cardiac arrest. The time to ac- quire IV access would certainly take longer even with a skilled provider than the 10 seconds it took us to insert the IO device. Studies show that the time to establish IV access in a variety of settings ranges from 2 to 49 minutes [28-30]. Administration of vasopressin by IO and IV achieved excellent survival rates indicating that both are effective methods of ac- cess. Based upon these findings, the TIO route might be considered as a first-line intervention.

Acknowledgment

This study was funded with a study from TriService Nursing Re- search Program grant number (N13-P10).

References

1. Atwood C, Eisenberg MS, Herlitz J, Rea TD. Incidence of EMS-treated out-of-hospital cardiac arrest in Europe. Resuscitation 2005;67(1):75-80.
2. Mentzelopoulos SD, Zakynthinos SG, Siempos I, Malachias S, Ulmer H, Wenzel V. Heart disease and stroke statistics-2015 update: a report from the American Heart Association. Circulation 2015;131(4):e29-322.
3. Neumar RW, Otto CW, Link MS, Kronick SL, Shuster M, Callaway CW, et al. Part 8: adult advanced cardiovascular life support 2010 American Heart Association guide- lines for cardiopulmonary resuscitation and emergency cardiovascular care. Circula- tion 2010;122(18 Suppl. 3):S729-67.
4. Perkins GD, Jacobs IG, Nadkarni VM, Berg RA, Bhanji F, Biarent D, et al. Cardiac arrest and cardiopulmonary resuscitation outcome reports: update of the Utstein Resusci- tation Registry Templates for Out-of-Hospital Cardiac Arrest: a statement for healthcare professionals from a Task Force of the International Liaison Committee on Resuscitation (American Heart Association, European Resuscitation Council, Australian and New Zealand Council on Resuscitation, Heart and Stroke Foundation of Canada, InterAmerican Heart Foundation, Resuscitation Council of Southern Africa, Resuscitation Council of Asia); and the American Heart Association Emergen- cy Cardiovascular Care Committee and the Council on Cardiopulmonary, Critical Care, Perioperative and Resuscitation. Circulation 2015;132(13):1286-300.
5. Hoskins SL, do Nascimento Jr P, Lima RM, Espana-Tenorio JM, Kramer GC. Pharmaco- kinetics of intraosseous and central venous drug delivery during cardiopulmonary resuscitation. Resuscitation 2012;83(1):107-12.
6. Donnino MW, Salciccioli JD, Howell MD, Cocchi MN, Giberson B, Berg K, et al. Time to administration of epinephrine and outcome after in-hospital cardiac arrest with

953-60.

1. Stiell IG, Hebert PC, Wells GA, Vandemheen KL, Tang AS, Higginson LA, et al. Vaso- pressin versus epinephrine for Inhospital CArdiac arrest: a randomised controlled trial. Lancet 2001;358(9276):105-9.
2. Wenzel V, Krismer AC, Arntz HR, Sitter H, Stadlbauer KH, Lindner KH, et al. A com- parison of vasopressin and epinephrine for out-of-hospital cardiopulmonary resus- citation. N Engl J Med 2004;350(2):105-13.
3. Larabee TM, Liu KY, Campbell JA, Little CM. Vasopressors in cardiac arrest: a system- atic review. Resuscitation 2012;83(8):932-9.
4. Mentzelopoulos SD, Zakynthinos SG, Siempos I, Malachias S, Ulmer H, Wenzel V. Va- sopressin for cardiac arrest: meta-analysis of randomized controlled trials. Resusci- tation 2012;83(1):32-9.
5. Voelckel WG, Lurie KG, McKnite S, Zielinski T, Lindstrom P, Peterson C, et al. Effects of epinephrine and vasopressin in a piglet model of prolonged ventricular fibrillation and cardiopulmonary resuscitation. Crit Care Med 2002;30(5):957-62.
6. Blebea JS, Houseni M, Torigian DA, Fan C, Mavi A, Zhuge Y, et al. Structural and func- tional imaging of normal bone marrow and evaluation of its age-related changes. Semin Nucl Med 2007;37(3):185-94.
7. Paquette S, Gordon C, Bradtmiller B. Anthropometric survey (ANSUR) II pilot study: methods and summary statistics. US Army Natick Soldier Research. Natick, MA: De- velopment and Engineering Center; 2009 74-5.
8. Johnson D, Dial J, Ard J, Yourk T, Burke E, Paine C, et al. Effects of intraosseous and intravenous administration of hextend(R) on time of administration and hemody- namics in a swine model. J Spec Oper Med 2014;14(1):79-85.
9. Hsieh Y, Korfmacher WA. Increasing speed and throughput when using HPLC-MS/ MS systems for drug metabolism and pharmacokinetic screening. Curr Drug Metab 2006;7(5):479-89.
10. Burgert J, Gegel B, Loughren M, Ceremuga T, Desai M, Schlicher M, et al. Comparison of tibial intraosseous, sternal intraosseous, and intravenous routes of administration on pharmacokinetics of epinephrine during cardiac arrest: a pilot study. AANA J 2012;80(4 Suppl.):S6-S10.
11. Johnson D, Garcia-Blanco J, Burgert J, Fulton L, Kadilak P, Perry K, et al. Effects of hu- meral intraosseous versus intravenous epinephrine on pharmacokinetics and return of spontaneous circulation in a porcine cardiac arrest model: a randomized control trial. Ann Med Surg (Lond) 2015;4(3):306-10.
12. Von Hoff D, Kuhn J, Burris III H, Miller L. Does intraosseous equal intravenous? A pharmacokinetic study. Am J Emerg Med 2008;26(1):31-8.
13. Wenzel V, Krismer AC, Arntz HR, Sitter H, Stadlbauer KH, Lindner KH, et al. Intraosseous vasopressin improves coronary perfusion pressure rapidly during car- diopulmonary resuscitation in pigs. Crit Care Med 1999;27(8):1565-9.
14. Hannon JP, Bossone CA, Wade CE. Normal physiological values for conscious pigs used in biomedical research. Lab Anim Sci 1990;40(3):293-8.
15. Swindle MM, Makin A, Herron AJ, Clubb Jr FJ, Frazier KS. Swine as models in biomed- ical research and toxicology testing. Vet Pathol 2012;49(2):344-56.
16. Costantino TG, Parikh AK, Satz WA, Fojtik JP. Ultrasonography-guided peripheral intravenous access versus traditional approaches in patients with difficult intravenous access. Ann Emerg Med 2005;46(5):456-61.
17. Lapostolle F, Catineau J, Garrigue B, Monmarteau V, Houssaye T, Vecci I, et al. Prospective evaluation of Peripheral venous access difficulty in emergency care. Intensive Care Med 2007;33(8):1452-7.
18. Paxton JH, Knuth TE, Klausner HA. Proximal humerus Intraosseous infusion: a preferred emergency venous access. J Trauma 2009;67(3):606-11.