Aortic valve-sparing operation versus Bentall and mechanical aortic valve replacement--midterm results

OBJECTIVES

The primary aim of this retrospective study was to evaluate short-term (one-to-six months) and mid-term (six-to-forty-eight months) results of aortic valve-sparing procedures. The second endpoint was to compare the results with the group of patients undergoing mechanical aortic valve replacement during the same period.

METHODS

Between April 2008 and May 2012 at our institution, we treated 76 patients either with ascending aorta/root aneurysm/dissection or with isolated aortic regurgitation. A total of seventy-six patients undergoing aortic valve surgery.

RESULTS

Analyzed parameters were divided into two parts as function of time. In the first part, i.e. during hospitalization, the mortality, duration of hospitalization, duration of extra corporeal circulation (ECC), and duration of cardiac arrest (CA) were compared and assessed. In the second part, i.e. during monitoring of the patients after their discharge from hospital (one-to-six months, and six-to-forty-eight months), the grade of postoperative AR aimed mainly at the group of aortic valve-sparing operations (subgroups A1, A2, A3), postoperative peak gradient, presence of thromboembolic and bleeding complications, postoperative endocarditis and need for reoperation or hospitalization due to cardiac reasons were analyzed.

CONCLUSION

Based on our first experience, we believe that in spite of higher technical difficulty, the aortic valve-sparing operations can be possibly performed with the same or respectively lower rate of postoperative morbidity and mortality. Presented results show that compared with the aortic valve replacement, the aortic valve-sparing operation is a promising method, and an interesting therapeutic alternative for patients. After proper indications, we consider it to be a method of choice (Tab. 6, Fig. 7, Ref. 28).

Ventilation and cardiopulmonary resuscitation

Ventilation is essential for oxygenation of the alveoli and arterial blood. Comatose humans have upper airway soft tissue obstruction unless the head is tilted backwards and sometimes, in addition, the jaw thrust forward. In 1960, measurements on comatose humans with or without cardiac arrest, with or without a tracheal tube, showed essentially no ventilation by sternal compressions alone. This led to combining step A (airway control), step B (mouth-to-mouth ventilation), and step C (sternal (cardiac) compressions) into basic life support. In animal models, sternal compressions alone can produce some ventilation with or without a tracheal tube, because the straight upper airways of animals do not obstruct in coma. In witnessed sudden cardiac death, the C-A-B sequence makes physiological sense, but other causes of sudden coma need the A-B-C sequence. Lay persons should continue to be taught cardiopulmonary resuscitation steps A-B-C.

Improved resuscitation outcome in emergency medical systems with increased usage of sodium bicarbonate during cardiopulmonary resuscitation

BACKGROUND

The use of sodium bicarbonate (SB) in cardiopulmonary resuscitation (CPR) is controversial. This study analyzes the effects of SB use on CPR outcome in the Brain Resuscitation Clinical Trial III (BRCT III), which was a multicenter randomized trial comparing high-dose to standard-dose epinephrine during CPR. Sodium bicarbonate use in BRCT III was optional.

METHODS

The entire BRCT III database was reviewed. Analysis included only patients who arrested out of the hospital and whose time from collapse to initiation of ACLS was no longer than 30 min (total n = 2122 patients). Sodium bicarbonate use by the 16 participating study sites was analyzed. The study sites were divided according to their SB usage profile: 'low SB user' sites administered SB in less than 50% of CPRs and their first epinephrine to SB time exceeded 10 min; and 'high SB user' sites used SB in over 50% of CPRs and their first epinephrine to SB time was <10 min.

RESULTS

Sites' SB usage rates ranged between 3.1% and 98.2% of CPRs. Sodium bicarbonate usage rates correlated inversely with the sites' intervals from collapse (r = - 0.579 P = 0.018) from initiation of ACLS (r = - 0.685 P = 0.003) and from first epinephrine (r = - 0.611 P = 0.012) to SB administration. Mean ROSC rate in the 'high SB user' sites was 33.5% (CI = 30.0-37.0) compared to 25.7% (CI = 23.1-28.4) in the 'low SB user' sites. In the 'high SB user' sites, hospital discharge rate was 5.3% (CI = 3.6-7.0) compared to 3% (CI = 2.0-4.0) in the 'low SB user' sites, and 5.3% (CI = 3.6-7.0) had a favorable neurological outcome compared to 2.1% (CI = 1.2-3.0) in the 'low SB user' sites. Collapse to ACLS interval was 8.5 min (CI = 8.1-9.0) in the 'high SB user' sites compared to 10.2 min (CI = 9.8-10.6) in the 'low SB user' sites, and their ACLS to first epinephrine interval was 7.0 min (CI = 6.5-7.5) compared to 9.7 min (CI = 9.3-10.2). Multivariate regression analysis found that belonging to 'high SB user' sites independently increased the chances for ROSC (OR 1.36, CI 1.08-1.7) and for achieving a good neurological outcome (OR 2.18, CI 1.23-3.86).

CONCLUSIONS

Earlier and more frequent use of SB was associated with higher early resuscitability rates and with better long-term outcome. Sodium bicarbonate may be beneficial during CPR, and it should be subjected to a randomized clinical trial.

Gut damage during hemorrhagic shock: effects on survival of oral or enteral interleukin-6

It has been reported that oral interleukin (IL)-6, without deleterious systemic side effects, prevents bacteremia and gut epithelial apoptosis after hemorrhagic shock (HS) in rodents. The goal of this study was to explore potential benefit of oral or enteral IL-6 on the gut and, consequently, on survival in a long-term outcome model of HS in rats. In Study A, 20 rats (control and IL-6, n = 10 per group) were anesthetized by spontaneous breathing of halothane and N2O. The left femoral vein and artery were cannulated. HS was initiated with withdrawal of 3 mL of blood per 100 g body weight over 15 min, and mean arterial pressure was maintained at 40 to 50 mmHg for another 75 min (total HS 90 min) by blood withdrawal or infusion of Ringer's solution. At HS 90 min, resuscitation included reinfusion of shed blood and additional Ringer's solution to restore normotension for 30 min. After awakening at resuscitation time 30 min, the rats received either 300 units IL-6 or the same volume of vehicle (controls) injected into the stomach via a feeding cannula. In Study B, 20 rats (control and IL-6, n = 10 per group), fasted overnight, were prepared and treated as in Study A, except that HS was initiated with withdrawal of 2 mL blood per 100 g over 10 min, and mean arterial pressure was maintained at 35-40 mmHg. IL-6 rats received 3,000 units IL-6 in 5 mL of normal saline injected directly into the ileum lumen 20 min after induction of shock and again at resuscitation time 60 min. Control rats received normal saline alone. In both studies, survival was observed to 72 h. In Study A, 7 of 10 rats in the control group and 5 of 10 in the IL-6 group survived to 72 h (NS). Macroscopic assessment of gut injury was not different between the two groups. In Study B, 6 of 10 rats survived to 72 h in each group. Frequency of bacteria growth in liver tissue of 72 h survivors was not different between the two groups. IL-6, administered into the stomach or directly injected into the small intestine lumen, did not protect the gut from ischemic injury, nor did it improve survival following severe HS in rats.

Intraperitoneal, but not enteric, adenosine administration improves survival after volume-controlled hemorrhagic shock in rats

OBJECTIVE

To circumvent the potential adverse systemic side effects of adenosine, this study explored the potential benefit of intraperitoneal or enteric adenosine on survival and inflammatory responses after volume-controlled hemorrhagic shock.

DESIGN

Prospective, randomized, and blinded. A three-phase, volume-controlled hemorrhagic shock model was used: hemorrhagic shock phase (120 mins), resuscitation phase (60 mins), and observation phase (72 hrs). Three groups were compared: controls, intraperitoneal adenosine, and enteric adenosine.

SETTING

Animal research facility.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Starting at 20 mins of hemorrhagic shock and continuing through the resuscitation phase, all three groups received both intraperitoneal lavage and repeated bolus injections into the ileum of vehicle (normal saline) or adenosine. In the intraperitoneal adenosine group (n = 10), adenosine solution (0.1 mM) was used for intraperitoneal lavage. In the enteric adenosine group (n = 10), adenosine (1.0 mM) was injected into the ileum. Blood cytokine concentrations and leukocyte infiltration in lungs and liver were studied in 12 separate rats (control and intraperitoneal adenosine, n = 6 each) with the same hemorrhagic shock model at resuscitation time 1 hr or 4 hrs.

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure and heart rate were similar between the three groups during hemorrhagic shock and resuscitation. Potassium, lactate, and blood urea nitrogen concentrations were lower and arterial pH was higher in the intraperitoneal and enteric adenosine groups compared with the control group (both p <.05). Survival time to 72 hrs was longer in the intraperitoneal adenosine group than in the control group(p <.05). Neither plasma interleukin-1beta, interleukin-6, interleukin-10, and tumor necrosis factor-alpha concentrations nor leukocyte infiltration in the lungs and liver was different between the control and intraperitoneal adenosine groups.

CONCLUSIONS

The administration of adenosine via the intraperitoneal route improves survival time after severe volume-controlled hemorrhagic shock in rats without worsening hypotension or bradycardia. This beneficial effect may not be attributable to effects of adenosine on the inflammatory response.

Fructose-1,6-bisphosphate and MK-801 by aortic arch flush for cerebral preservation during exsanguination cardiac arrest of 20 min in dogs. An exploratory study

In our exsanguination cardiac arrest (CA) outcome model in dogs we are systematically exploring suspended animation (SA), i.e. preservation of brain and heart immediately after the onset of CA to enable transport and resuscitative surgery during CA, followed by delayed resuscitation. We have shown in dogs that inducing moderate cerebral hypothermia with an aortic arch flush of 500 ml normal saline solution at 4 degrees C, at start of CA 20 min no-flow, leads to normal functional outcome. We hypothesized that, using the same model, but with the saline flush at 24 degrees C inducing minimal cerebral hypothermia (which would be more readily available in the field), adding either fructose-1,6-bisphosphate (FBP, a more efficient energy substrate) or MK-801 (an N-methyl-D-aspartate (NMDA) receptor blocker) would also achieve normal functional outcome. Dogs (range 19-30 kg) were exsanguinated over 5 min to CA of 20 min no-flow, and resuscitated by closed-chest cardiopulmonary bypass (CPB). They received assisted circulation to 2 h, mild systemic hypothermia (34 degrees C) post-CA to 12 h, controlled ventilation to 20 h, and intensive care to 72 h. At CA 2 min, the dogs received an aortic arch flush of 500 ml saline at 24 degrees C by a balloon-tipped catheter, inserted through the femoral artery (control group, n=6). In the FBP group (n=5), FBP (total 1440 or 4090 mg/kg) was given by flush and with reperfusion. In the MK-801 group (n=5), MK-801 (2, 4, or 8 mg/kg) was given by flush and with reperfusion. Outcome was assessed in terms of overall performance categories (OPC 1, normal; 2, moderate disability; 3, severe disability; 4, coma; 5, brain death or death), neurologic deficit scores (NDS 0-10%, normal; 100%, brain death), and brain histologic damage scores (HDS, total HDS 0, no damage; >100, extensive damage; 1064, maximal damage). In the control group, one dog achieved OPC 2, one OPC 3, and four OPC 4; in the FBP group, two dogs achieved OPC 3, and three OPC 4; in the MK-801 group, two dogs achieved OPC 3, and three OPC 4 (P=1.0). Median NDS were 62% (range 8-67) in the control group; 55% (range 34-66) in the FBP group; and 50% (range 26-59) in the MK-801 group (P=0.2). Median total HDS were 130 (range 56-140) in the control group; 96 (range 64-104) in the FBP group; and 80 (range 34-122) in the MK-801 group (P=0.2). There was no difference in regional HDS between groups. We conclude that neither FBP nor MK-801 by aortic arch flush at the start of CA, plus an additional i.v. infusion of the same drug during reperfusion, can provide cerebral preservation during CA 20 min no-flow. Other drugs and drug-combinations should be tested with this model in search for a breakthrough effect.

Thiopental and phenytoin by aortic arch flush for cerebral preservation during exsanguination cardiac arrest of 20 minutes in dogs. An exploratory study

We are systematically exploring in our exsanguination cardiac arrest (CA) outcome model in dogs suspended animation (SA), i.e. immediate preservation of brain and heart for resuscitative surgery during CA, with delayed resuscitation. We have shown in dogs that inducing moderate cerebral hypothermia with an aortic arch flush of 500 ml normal saline solution of 4 degrees C, at start of CA 20 min no-flow, leads to normal functional outcome. We hypothesized that, using the same model, adding thiopental (or even better thiopental plus phenytoin) to the flush at ambient temperature (24 degrees C), which would be more readily available in the field, will also achieve normal functional outcome. Thirty dogs (20-28 kg) were exsanguinated over 5 min to CA of 20 min no-flow, and resuscitated by closed-chest cardiopulmonary bypass. They received assisted circulation to 2 h, 34 degrees C post-CA to 12 h, controlled ventilation to 20 h, and intensive care to 72 h. At CA 2 min, the dogs received an aortic arch flush of 500 ml saline at 24 degrees C by a balloon-tipped catheter, inserted through the femoral artery (control group 1, n=14). In group 2 (n=9), thiopental (variable total doses of 15-120 mg/kg) was added to the flush and given with reperfusion. In group 3 (n=7), thiopental (15 or 45 mg/kg) plus phenytoin (10, 20, or 30 mg/kg) was given by flush and with reperfusion. Outcome was assessed in terms of overall performance categories (OPC 1, normal; 2, moderate disability; 3, severe disability; 4, coma; 5, brain death), neurologic deficit scores (NDS 0-10%, normal; 100%, brain death), and histologic deficit scores (HDS, total and regional). The flush reduced tympanic temperature to about 36 degrees C in all groups. In control group 1, one dog achieved OPC 1, three OPC 2, six OPC 3, and four OPC 4. In thiopental group 2, two dogs achieved OPC 1, two OPC 3, and five OPC 4. In thiopental/phenytoin group 3, one dog achieved OPC 1, two OPC 3, and four OPC 4 (p=0.5). Median NDS were 36% (IQR 22-62%) in group 1; 51% (IQR 22-56%) in group 2; and 55% (IQR 38-59%) in group 3 (p=0.7). Median total HDS were 67 (IQR 56-127) in group 1; 60 (IQR 52-138) in group 2; and 76 (IQR 48-132) in group 3 (p=1.0). Thiopental and thiopental/phenytoin dogs achieved significantly lower HDS only in the putamen. Thiopental in large doses caused side effects. We conclude that neither thiopental alone nor thiopental plus phenytoin by flush, with or without additional intravenous infusion, can consistently provide 'clinically significant' cerebral preservation for 20 min no-flow. Other drugs and drug-combinations should be tested with this model in search for a breakthrough effect.

The role of the gut in the pathogenesis of death due to hyperthermia

Pathologic data from the gastrointestinal tract in heat-stroke victims, although documented, are confusing. The object of this study was to document the gastrointestinal changes observed during induced total body hyperthermia (42 degrees C) followed by cooling. An established heat-stroke model was used in a university animal laboratory. Group A underwent immersion hyperthermia for 1 hour, followed by cooling to normothermia. Group B underwent hyperthermia to cardiac arrest, followed by resuscitation plus cooling to normothermia. The postmortem findings in the gastrointestinal tract were evaluated. In group A, several hours after return to normothermia and stable vital signs, delayed secondary deterioration with massive gastrointestinal bleeding occurred. The postmortem findings revealed bleeding into the whole intestine and serosanguineous fluid in the peritoneal cavity. In group B, an adynamic gut was observed after 165 +/- 21 minutes (range 125-174) of heating when mean arterial pressure (MAP) decreased to 38 +/- 21 mm Hg (range 30-70). Cardiac arrest occurred at 178 +/- 26 minutes (range 140-208) of immersion. Eight monkeys could be resuscitated to spontaneous circulation with return of normal gut motility, then they rearrested at 158 +/- 68 minutes (range 45-228). The postmortem findings resembled those in group A. The Postmortem findings in the four monkeys in which restoration of spontaneous circulation failed, revealed only some intestinal wall edema and occasional petechial hemorrhages. It is concluded that after a hyperthermic event, tissue injury continues to develop. The pathologic findings are related to the time lapse between hyperthermia, cooling, and death. The similarity to the descriptions of septic shock, multiple organ failure, and the gut reperfusion syndrome is striking. An immunologic response as a mechanism for all these syndromes is discussed.

Mild hypothermia increases survival from severe pressure-controlled hemorrhagic shock in rats

BACKGROUND

In previous studies, mild hypothermia (34 degrees C) during uncontrolled hemorrhagic shock (HS) increased survival. Hypothermia also increased mean arterial pressure (MAP), which may have contributed to its beneficial effect. We hypothesized that hypothermia would improve survival in a pressure-controlled HS model and that prolonged hypothermia would further improve survival.

METHODS

Thirty rats were prepared under light nitrous oxide/halothane anesthesia with spontaneous breathing. The rats underwent HS with an initial blood withdrawal of 2 mL/100 g over 10 minutes and pressure-controlled HS at a MAP of 40 mm Hg over 90 minutes (without anticoagulation), followed by return of shed blood and additional lactated Ringer's solution to achieve normotension. Hemodynamic monitoring and anesthesia were continued to 1 hour, temperature control to 12 hours, and observation without anesthesia to 72 hours. After HS of 15 minutes, 10 rats each were randomized to group 1, with normothermia (38 degrees C) throughout; group 2, with brief mild hypothermia (34 degrees C during HS 15-90 minutes plus 30 minutes after reperfusion); and group 3, with prolonged mild hypothermia (same as group 2, then 35 degrees C [possible without shivering] from 30 minutes after reperfusion to 12 hours).

RESULTS

MAP during HS and initial resuscitation was the same in all three groups, but was higher in the hypothermia groups 2 and 3, compared with the normothermia group 1, at 45 and 60 minutes after reperfusion. Group 1 required less blood withdrawal to maintain MAP 40 mm Hg during HS and more lactated Ringer's solution for resuscitation. At end of HS, lactate levels were higher in group 1 than in groups 2 and 3 (p < 0.02). Temperatures were according to protocol. Survival to 72 hours was achieved in group 1 by 3 of 10 rats, in group 2 by 7 of 10 rats (p = 0.18 vs. group 1), and in group 3 by 9 of 10 rats (p = 0.02 vs. group 1, p = 0.58 vs. group 2). Survival time was longer in group 2 (p = 0.09) and group 3 (p = 0.007) compared with group 1.

CONCLUSION

Brief hypothermia had physiologic benefit and a trend toward improved survival. Prolonged mild hypothermia significantly increased survival after severe HS even with controlled MAP. Extending the duration of hypothermia beyond the acute phases of shock and resuscitation may be needed to ensure improved outcome after prolonged HS.

Rapid hypothermic aortic flush can achieve survival without brain damage after 30 minutes cardiac arrest in dogs

BACKGROUND

Neither exsanguination to pulselessness nor cardiac arrest of 30 min duration can be reversed with complete neurologic recovery using conventional resuscitation methods. Techniques that might buy time for transport, surgical hemostasis, and initiation of cardiopulmonary bypass or other resuscitation methods would be valuable. We hypothesized that an aortic flush with high-volume cold normal saline solution at the start of exsanguination cardiac arrest could rapidly preserve cerebral viability during 30 min of complete global ischemia and achieve good outcome.

METHODS

Sixteen dogs weighing 20-25 kg were exsanguinated to pulselessness over 5 min, and circulatory arrest was maintained for another 30 min. They were then resuscitated using closed-chest cardiopulmonary bypass and had assisted circulation for 2 h, mild hypothermia (34 degrees C) for 12 h, controlled ventilation for 20 h, and intensive care to outcome evaluation at 72 h. Two minutes after the onset of circulatory arrest, the dogs received a flush of normal saline solution at 4 degrees C into the aorta (cephalad) via a balloon catheter. Group I (n = 6) received a flush of 25 ml/kg saline with the balloon in the thoracic aorta; group II (n = 7) received a flush of 100 ml/kg saline with the balloon in the abdominal aorta.

RESULTS

The aortic flush decreased mean tympanic membrane temperature (Tty) in group I from 37.6 +/- 0.1 to 33.3 +/- 1.6 degrees C and in group II from 37.5 +/- 0.1 to 28.3 +/- 2.4 degrees C (P = 0.001). In group 1, four dogs achieved overall performance category (OPC) 4 (coma), and 2 dogs achieved OPC 5 (brain death). In group II, 4 dogs achieved OPC 1 (normal), and 3 dogs achieved OPC 2 (moderate disability). Median (interquartile range [IQR]) neurologic deficit scores (NDS 0-10% = normal; NDS 100% = brain death) were 69% (56-99%) in group I versus 4% (0-15%) in group II (P = 0.003). Median total brain histologic damage scores (HDS 0 = no damage; > 100 = extensive damage; 1,064 = maximal damage) were 144 (74-168) in group I versus 18 (3-36) in group II (P = 0.004); in three dogs from group II, the brain was histologically normal (HDS 0-5).

CONCLUSIONS

A single high-volume flush of cold saline (4 degrees C) into the abdominal aorta given 2 min after the onset of cardiac arrest rapidly induces moderate-to-deep cerebral hypothermia and can result in survival without functional or histologic brain damage, even after 30 min of no blood flow.

Peritoneal ventilation with oxygen improves outcome after hemorrhagic shock in rats

OBJECTIVE

In experimental pulmonary consolidation with hypoxemia in rabbits, peritoneal ventilation (PV) with 100% oxygen (PV-O2) improved PaO2. We hypothesized that PV-O2 could improve outcome after hemorrhagic shock (HS) with normal lungs, by mitigating dysoxia of the abdominal viscera.

DESIGN

Randomized, controlled, laboratory animal study.

SETTING

University animal research facility.

SUBJECTIVE

Male Sprague-Dawley rats.

INTERVENTIONS

Thirty rats under light anesthesia (N2O/oxygen plus halothane) and spontaneous breathing underwent blood withdrawal of 3 mL/100 g over 15 mins. After volume-controlled HS phase 1 of 60 mins, resuscitation phase 2 of 60 mins included infusion of shed blood and, if necessary, additional lactated Ringer's solution intravenously to control normotension from 60 to 120 mins. This was followed by observation phase 3 for 7 days. We randomized three groups of ten rats each: group I received PV-O2, starting at 15 mins of HS at a rate of 40 inflations/min, and a peritoneal "tidal volume" of 6 mL, until the end of phase 2. Group II received the same PV with room air (PV-Air). Control group III was treated without PV.

MEASUREMENTS AND MAIN RESULTS

During the second half of HS phase 1, mean arterial pressures were higher in the PV-O2 group I compared with the PV-Air group II and control group III (p < .05). All 30 rats survived the 120 mins of phases 1 and 2. Survival to 7 days was achieved by ten of ten rats in PV-O2 group I; by nine of ten in PV-Air group II; and by five of ten in control group III (p < .05 vs. group I; NS vs. group II). Survival times of <7 days were 5 days in the one death of group II and ranged between 6 hrs and 4 days in the five deaths of group III. In 7-day survivors, neurologic deficit scores (0% to 10% = normal, 100% = death) were normal, ranging between zero and 8%. Necropsies of rats that died during phase 3 showed multiple areas of necrosis of the gut, some with perforations. Necropsies in the five survivors to 7 days of group III showed marked macroscopic and microscopic changes (scattered areas of necrosis of stomach and intestine, adhesions, and pale areas in the liver). These changes were absent or less severe in the nine survivors of group II. Viscera appeared normal in all ten rats of PV-O2 group I.

CONCLUSIONS

Peritoneal ventilation with oxygen during and after severe hemorrhagic shock in rats seems to decrease morbidity and mortality by helping preserve viability of abdominal viscera.

Rapid induction of mild cerebral hypothermia by cold aortic flush achieves normal recovery in a dog outcome model with 20-minute exsanguination cardiac arrest

OBJECTIVES

Resuscitation attempts in trauma victims who suffer cardiac arrest (CA) from exsanguination almost always fail. The authors hypothesized that an aortic arch flush with cold normal saline solution (NSS) at the start of exsanguination CA can preserve cerebral viability during 20-minute no-flow.

METHODS

Twelve dogs were exsanguinated over 5 minutes to CA of 20-minute no-flow, resuscitated by cardiopulmonary bypass, followed by post-CA mild hypothermia (34 degrees C) continued to 12 hours, controlled ventilation to 20 hours, and intensive care to 72 hours. At CA 2 minutes, the dogs received a 500-mL flush of NSS at either 24 degrees C (group 1, n = 6) or 4 degrees C (group 2, n = 6), using a balloon-tipped catheter inserted via the femoral artery into the descending thoracic aorta.

RESULTS

The flush at 24 degrees C (group 1) decreased tympanic membrane temperature [mean (+/-SD)] from 37.5 degrees C (+/-0.1) to 35.7 degrees C (+/-0.2); the flush at 4 degrees C (group 2) to 34.0 degrees C (+/-1.1) (p = 0.005). In group 1, one dog achieved overall performance category (OPC) 2 (moderate disability), one OPC 3 (severe disability), and four OPC 4 (coma). In group 2, four dogs achieved OPC 1 (normal), one OPC 2, and one OPC 3 (p = 0.008). Neurologic deficit scores (0-10% normal, 100% brain death) [median (25th-75th percentile)] were 62% (40-66) in group 1 and 5% (0-19) in group 2 (p = 0.01). Total brain histologic damage scores were 130 (62-137) in group 1 and 24 (10-55) in group 2 (p = 0.008).

CONCLUSIONS

Aortic arch flush of 4 degrees C at the start of CA of 20 minutes rapidly induces mild cerebral hypothermia and can lead to normal functional recovery with minimal histologic brain damage. The same model with aortic arch flush of 24 degrees C results in survival with brain damage in all dogs, which makes it suitable for testing other (e.g., pharmacologic) preservation potentials.

Suspended animation for delayed resuscitation from prolonged cardiac arrest that is unresuscitable by standard cardiopulmonary-cerebral resuscitation

Standard cardiopulmonary-cerebral resuscitation fails to achieve restoration of spontaneous circulation in approximately 50% of normovolemic sudden cardiac arrests outside hospitals and in essentially all victims of penetrating truncal trauma who exsanguinate rapidly to cardiac arrest. Among cardiopulmonary-cerebral resuscitation innovations since the 1960s, automatic external defibrillation, mild hypothermia, emergency (portable) cardiopulmonary bypass, and suspended animation have potentials for clinical breakthrough effects. Suspended animation has been suggested for presently unresuscitable conditions and consists of the rapid induction of preservation (using hypothermia with or without drugs) of viability of the brain, heart, and organism (within 5 mins of normothermic cardiac arrest no-flow), which increases the time available for transport and resuscitative surgery, followed by delayed resuscitation. Since 1988, we have developed and used novel dog models of exsanguination cardiac arrest to explore suspended animation potentials with hypothermic and pharmacologic strategies using aortic cold flush and emergency portable cardiopulmonary bypass. Outcome evaluation was at 72 or 96 hrs after cardiac arrest. Cardiopulmonary bypass cannot be initiated rapidly. A single aortic flush of cold saline (4 degrees C) at the start of cardiac arrest rapidly induced (depending on flush volume) mild-to-deep cerebral hypothermia (35 degrees to 10 degrees C), without cardiopulmonary bypass, and preserved viability during a cardiac arrest no-flow period of up to 120 mins. In contrast, except for one antioxidant (Tempol), explorations of 14 different drugs added to the aortic flush at room temperature (24 degrees C) have thus far had disappointing outcome results. Profound hypothermia (10 degrees C) during 60-min cardiac arrest induced and reversed with cardiopulmonary bypass achieved survival without functional or histologic brain damage. Further plans for the systematic development of suspended animation include the following: a) aortic flush, combining hypothermia with mechanism-specific drugs and novel fluids; b) extension of suspended animation by ultraprofound hypothermic preservation (0 degrees to 5 degrees C) with cardiopulmonary bypass; c) development of the most effective suspended animation protocol for clinical trials in trauma patients with cardiac arrest; and d) modification of suspended animation protocols for possible use in normovolemic ventricular fibrillation cardiac arrest, in which attempts to achieve restoration of spontaneous circulation by standard external cardiopulmonary resuscitation-advanced life support have failed.

Life supporting first aid (LSFA) teaching to Brazilians by television spots

Accidents in developing countries are frequent and have high mortality and morbidity rates. In Brazil, in 1995-1996, the year of this study, life supporting first aid (LSFA), which includes cardiopulmonary resuscitation (CPR) basic life support (BLS) was not taught in schools. With the population of 165 million, the only way to teach the adult population on a large scale would be by television (TV), that is widely viewed. This study compares two groups of factory employees - 86 controls without TV exposure to LSFA and 116 exposed to brief LSFA skill demonstrations on TV. Their ability to acquire eight LSFA skills was evaluated: external hemorrhage control; immobilization of a suspected forearm fracture; treatment of a skin burn by cold flush; body alignment after a fall; positioning for shock and coma; airway control by backward tilt of the head; and CPR (steps A-B-C). Simulated skill performance on the evaluating nurse or manikin was tested at 1 week, 1 month, and 13 months. In the control group, 1-31% performed individual skills correctly; as compared to 9-96% of the television group (P<0.001). There was excellent retention over 13 months. Over 50% of the television group performed correctly five of the eight skills, including positioning and hemorrhage control. Television viewing increased correct airway control performance from 5 to 25% of trainees, while it remained at 3% in the control group. CPR-ABC performance, however, was very poor in both groups. We conclude that a significant proportion of factory workers can acquire simple LSFA skills through television viewing alone, except for the skill acquisition of CPR steps B (mouth-to-mouth ventilation) and C (external chest compressions) which need coached manikin practice.

Delayed, spontaneous hypothermia reduces neuronal damage after asphyxial cardiac arrest in rats

OBJECTIVE

Core temperature is reduced spontaneously after asphyxial cardiac arrest in rats. To determine whether spontaneous hypothermia influences neurologic damage after asphyxial arrest, we compared neurologic outcome in rats permitted to develop spontaneous hypothermia vs. rats managed with controlled normothermia.

INTERVENTIONS

Male Sprague-Dawley rats were asphyxiated for 8 mins and resuscitated. After extubation, a cohort of rats was managed with controlled normothermia (CN) by placement in a servo-controlled incubator set to maintain rectal temperature at 37.4 degrees C for 48 hrs. CN rats were compared with permissive hypothermia (PH) rats that were returned to an ambient temperature environment after extubation. Rats were killed at either 72 hrs (PH72hr, n = 14; CN72hr, n = 9) or 6 wks (PH6wk, n = 6, CN6wk, n = 6) after resuscitation. PH72 rats were historic controls for the CN72 rats, whereas PH6 and CN6 rats were randomized and studied contemporaneously.

MEASUREMENTS

A clinical neurodeficit score (NDS) was determined daily. A pathologist blinded to group scored 40 hematoxylin and eosin -stained brain regions for damage by using a 5-point scale (0 = none, 5 = severe). Quantitative analysis of CA1 hippocampus injury was performed by counting normal-appearing neurons in a defined subsection of CA1.

MAIN RESULTS

Mean rectal temperatures measured in the PH6wk rats (n = 6) were 36.9, 34.8, 35.5, 36.7, and 37.4 degrees C at 2, 8, 12, 24, and 36 hrs, respectively. Mortality rate (before termination) was lower in PH compared with CN (0/20 vs. 7/15; p < .005). PH demonstrated a more favorable progression of NDS (p = .04) and less weight loss (p < .005) compared with CN. Median histopathology scores were lower (less damage) in PH72hr vs. CN72hr for temporal cortex (0 vs. 2.5), parietal cortex (0 vs. 2), thalamus (0 vs. 3), CA1 hippocampus (1.5 vs. 4.5), CA2 hippocampus (0 vs. 3.5), subiculum (0 vs. 4), and cerebellar Purkinje cell layer (2 vs. 4) (all p < .05). There was almost complete loss of normal-appearing CA1 neurons in CN72hr rats (6 +/- 2 [mean +/- SD] normal neurons compared with 109 +/- 12 in naïve controls). In contrast, PH72hr rats demonstrated marked protection (97 +/- 23 normal-appearing neurons) that was still evident, although attenuated, at 6 wks (42 +/- 24 normal-appearing neurons, PH6wk).

CONCLUSION

Rats resuscitated from asphyxial cardiac arrest develop delayed, mild to moderate, prolonged hypothermia that is neuroprotective.

Effects of increased oxygen breathing in a volume controlled hemorrhagic shock outcome model in rats

It is believed that victims of traumatic hemorrhagic shock (HS) benefit from breathing 100% O(2). Supplying bottled O(2) for military and civilian first aid is difficult and expensive. We tested the hypothesis that increased FiO(2) both during severe volume-controlled HS and after resuscitation in rats would: (1) increase blood pressure; (2) mitigate visceral dysoxia and thereby prevent post-shock multiple organ failure; and (3) increase survival time and rate. Thirty rats, under light anesthesia with halothane (0. 5% throughout), with spontaneous breathing of air, underwent blood withdrawal of 3 ml/100 g over 15 min. After HS phase I of 60 min, resuscitation phase II of 180 min with normotensive intravenous fluid resuscitation (shed blood plus lactated Ringer's solution), was followed by an observation phase III to 72 h and necropsy. Rats were randomly divided into three groups of ten rats each: group 1 with FiO(2) 0.21 (air) throughout; group 2 with FiO(2) 0.5; and group 3 with FiO(2) 1.0, from HS 15 min to the end of phase II. Visceral dysoxia was monitored during phases I and II in terms of liver and gut surface PCO(2) increase. The main outcome variables were survival time and rate. PaO(2) values at the end of HS averaged 88 mmHg with FiO(2) 0.21; 217 with FiO(2) 0.5; and 348 with FiO(2) 1. 0 (P<0.001). During HS phase I, FiO(2) 0.5 increased mean arterial pressure (MAP) (NS) and kept arterial lactate lower (P<0.05), compared with FiO(2) 0.21 or 1.0. During phase II, FiO(2) 0.5 and 1. 0 increased MAP compared with FiO(2) 0.21 (P<0.01). Heart rate was transiently slower during phases I and II in oxygen groups 2 and 3, compared with air group 1 (P<0.05). During HS, FiO(2) 0.5 and 1.0 mitigated visceral dysoxia (tissue PCO(2) rise) transiently, compared with FiO(2) 0.21 (P<0.05). Survival time (by life table analysis) was longer after FiO(2) 0.5 than after FiO(2) 0.21 (P<0. 05) or 1.0 (NS), without a significant difference between FiO(2) 0. 21 and 1.0. Survival rate to 72 h was achieved by two of ten rats in FiO(2) 0.21 group 1, by four of ten rats in FiO(2) 0.5 group 2 (NS); and by four of ten rats of FiO(2) 1.0 group 3 (NS). In late deaths macroscopic necroses of the small intestine were less frequent in FiO(2) 0.5 group 2. We conclude that in rats, in the absence of hypoxemia, increasing FiO(2) from 0.21 to 0.5 or 1.0 does not increase the chance to achieve long-term survival. Breathing FiO(2) 0.5, however, might increase survival time in untreated HS, as it can mitigate hypotension, lactacidemia and visceral dysoxia.

Hypothermia and hyperthermia in children after resuscitation from cardiac arrest

OBJECTIVE

In experimental models of ischemic-anoxic brain injury, changes in body temperature after the insult have a profound influence on neurologic outcome. Specifically, hypothermia ameliorates whereas hyperthermia exacerbates neurologic injury. Accordingly, we sought to determine the temperature changes occurring in children after resuscitation from cardiac arrest.

STUDY DESIGN

The clinical records of 13 children resuscitated from cardiac arrest were analyzed. Patients were identified through the emergency department and pediatric intensive care unit arrest logs. Only patients surviving for > or =12 hours after resuscitation were considered for analysis. Charts were reviewed for body temperatures, warming or cooling interventions, antipyretic and antimicrobial administration, and evidence of infection.

RESULTS

Seven patients had a minimum temperature (T min) of < or =35 degrees C and 11 had a maximum temperature (T max) of > or =38.1 degrees C. Hypothermia often preceded hyperthermia. All 7 patients with T min < or =35 degrees C were actively warmed with heating lamps and 5 of 7 responded to warming with a rebound of body temperatures > or =38.1 degrees C. None of the 6 patients with T min >35 degrees C were actively warmed but all developed T max > or =38.1 degrees C. Six patients received antipyretics and 11 received antibiotics. Fever was not associated with a positive culture in any case. Conclusion. Spontaneous hypothermia followed by hyperthermia is common after resuscitation from cardiac arrest. Temperature should be closely monitored after cardiac arrest and fever should be managed expectantly.

Mild or moderate hypothermia, but not increased oxygen breathing, increases long-term survival after uncontrolled hemorrhagic shock in rats

OBJECTIVE

To test the hypotheses that, for uncontrolled hemorrhagic shock (UHS) in rats, mild hypothermia, compared with normothermia, would increase long-term survival as well as moderate hypothermia, oxygen breathing would increase survival further, and hypothermia and oxygen would mitigate visceral ischemia (dysoxia) during UHS.

DESIGN

Prospective, randomized study.

SETTING

Animal research laboratory.

SUBJECTS

A total of 54 male Sprague-Dawley rats.

INTERVENTIONS

Under light anesthesia and spontaneous breathing, rats underwent UHS phase I of 75 mins, with initial withdrawal of 3 mL/100 g of blood over 15 mins, followed by UHS via tail amputation and limited fluid resuscitation to maintain mean arterial pressure at > or =40 mm Hg; resuscitation phase II of 60 mins (from 75 mins to 135 mins) with hemostasis and aggressive fluid resuscitation to normalize hemodynamics; and observation phase III to 72 hrs. Rats were randomly divided into nine groups (n = 6 each) with three rectal temperature levels (38 degrees C [normothermia] vs. 34 degrees C [mild hypothermia] vs. 30 degrees C [moderate hypothermia]) by surface cooling; each with 3 FIO2 levels (0.25 vs. 0.5 vs. 1.0).

MEASUREMENTS AND MAIN RESULTS

Hypothermia increased blood pressure compared with normothermia. Increased FIO2 had no effect on blood pressure. Additional blood loss from the tail cut was small, with no differences among groups. Hypothermia and FIO2 of 0.5 decreased visceral hypoxia, as measured by the difference between visceral (liver and jejunum) surface Pco2 and PaCO2 during UHS. Compared with normothermia, mild hypothermia increased the survival time and rate as well as moderate hypothermia (p < .01 by life table), without a significant difference between mild and moderate hypothermia. Increased FIO2 had no effect on survival time or rate.

CONCLUSIONS

After severe UHS and resuscitation in rats, mild hypothermia during UHS, compared with normothermia, increases blood pressure, survival time and 72-hr survival rate as well as moderate hypothermia. Mild hypothermia is clinically more feasible and safer than moderate hypothermia. Increased FIO2 seems to have no significant effect on outcome.

Thiopental combination treatments for cerebral resuscitation after prolonged cardiac arrest in dogs. Exploratory outcome study

We postulate that mitigating the multifactorial pathogenesis of postischemic encephalopathy requires multifaceted treatments. In preparation for expensive definitive studies, we are reporting here the results of small exploratory series, compared with historic controls with the same model. We hypothesized that the brain damage mitigating effect of mild hypothermia after cardiac arrest can be enhanced with thiopental loading, and even more so with the further addition of phenytoin and methylprednisolone. Twenty-four dogs (four groups of six dogs each) received VF 12.5 min no-flow, reversed with brief cardiopulmonary bypass (CPB), controlled ventilation to 20 h, and intensive care to 96 h. Group 1 with normothermia throughout and randomized group 2 with mild hypothermia (from reperfusion to 2 h) were controls. Then, group 3 received in addition, thiopental 90 mg/kg i.v. over the first 6 h. Then, group 4 received, in addition to group 2 treatment, thiopental 30 mg/kg i.v. over the first 90 min (because the larger dose had produced cardiopulmonary complications), plus phenytoin 15 mg/kg i.v. at 15 min after reperfusion, and methylprednisolone 130 mg/kg i.v. over 20 h. All dogs survived. Best overall performance categories (OPC) achieved (OPC 1 = normal, OPC 5 = brain death) were better in group 2 than group 1 (< 0.05) and numerically better in groups 3 or 4 than in groups 1 or 2. Good cerebral outcome (OPC 1 or 2) was achieved by all six dogs only in group 4 (P < 0.05 group 4 vs. 2). Best NDS were 44 +/- 3% in group 1; 20 +/- 14% in group 2 (P = 0.002); 21 +/- 15% in group 3 (NS vs. group 2); and 7 +/- 8% in group 4 (P = 0.08 vs. group 2). Total brain histologic damage scores (HDS) at 96 h were 156 +/- 38 in group 1; 81 +/- 12 in group 2 (P < 0.001 vs. group 1); 53 +/- 25 in group 3 (P = 0.02 vs. group 2); and 48 +/- 5 in group 4 (P = 0.02 vs. group 2). We conclude that after prolonged cardiac arrest, the already established brain damage mitigating effect of mild immediate postarrest hypothermia might be enhanced by thiopental, and perhaps then further enhanced by adding phenytoin and methylprednisolone.

Adenosine by aortic flush fails to augment the brain preservation effect of mild hypothermia during exsanguination cardiac arrest in dogs - an exploratory study

Most trauma cases with rapid exsanguination to cardiac arrest (CA) in the field, as well as many cases of normovolemic sudden cardiac death are 'unresuscitable' by standard cardiopulmonary-cerebral resuscitation (CPCR). We are presenting a dog model for exploring pharmacological strategies for the rapid induction by aortic arch flush of suspended animation (SA), i.e. preservation of cerebral viability for 15 min or longer. This can be extended by profound hypothermic circulatory arrest of at least 60 min, induced and reversed with (portable) cardiopulmonary bypass (CPB). SA is meant to buy time for transport and repair during pulselessness, to be followed by delayed resuscitation to survival without brain damage. This model with exsanguination over 5 min to CA of 15-min no-flow, is to evaluate rapid SA induction by aortic flush of normal saline solution (NSS) at room temperature (24 degrees C) at 2-min no-flow. This previously achieved normal functional recovery, but with histologic brain damage. We hypothesized that the addition of adenosine would achieve recovery with no histologic damage, because adenosine delays energy failure and helps repair brain injury. This dog model included reversal of 15-min no-flow with closed-chest CPB, controlled ventilation to 20 h, and intensive care to 72 h. Outcome was evaluated by overall performance, neurologic deficit, and brain histologic damage. At 2 min of CA, 500 ml of NSS at 24 degrees C was flushed (over 1 min) into the brain and heart via an aortic balloon catheter. Controls (n=5) received no drug. The adenosine group (n=5) received 2-chloro-adenosine (long acting adenosine analogue), 30 mg in the flush solution, and, after reperfusion, adenosine i.v. over 12 h (210 microg/kg per min for 3 h, 140 microg/kg per min for 9 h). The 24 degrees C flush reduced tympanic membrane temperature (T(ty)) within 2 min of CA from 37.5 to approximately 36.0 degrees C in both groups. At 72 h, final overall performance category (OPC) 1 (normal) was achieved by all ten dogs of the two groups. Final neurologic deficit scores (NDS; 0-10% normal, 100% brain death) were 5+/-3% in the control group versus 6+/-5% in the adenosine group (NS). Total brain histologic damage scores (HDS) at 72 h were 74+/-9 (64-80) in the control group versus 68+/-19 (40-88) in the adenosine group (NS). In both groups, ischemic neurons were as prevalent in the basal ganglia and neocortex as in the cerebellum and hippocampus. The mild hypothermic aortic flush protocol is feasible in dogs. The adenosine strategy used does not abolish the mild histologic brain damage.

On the future of reanimatology

This article is adapted from a presentation given at the 1999 SAEM annual meeting by Dr. Peter Safar. Dr. Safar has been involved in resuscitation research for 44 years, and is a distinguished professor and past initiating chairman of the Department of Anesthesiology and Critical Care Medicine at the University of Pittsburgh. He is the founder and director of the Safar Center for Resuscitation Research at the University of Pittsburgh, and has been the research mentor of many critical care and emergency medicine research fellows. Here he presents a brief history of past accomplishments, recent findings, and future potentials for resuscitation research. Additional advances in resuscitation, from acute terminal states and clinical death, will build upon the lessons learned from the history of reanimatology, including optimal delivery by emergency medical services of already documented cardiopulmonary cerebral resuscitation, basic-advanced-prolonged life support, and future scientific breakthroughs. Current controversies, such as how to best educate the public in life-supporting first aid, how to restore normotensive spontaneous circulation after cardiac arrest, how to rapidly induce mild hypothermia for cerebral protection, and how to minimize secondary insult after cerebral ischemia, are discussed, and must be resolved if advances are to be made. Dr. Safar also summarizes future technologies already under preliminary investigation, such as ultra-advanced life support for reversing prolonged cardiac arrest, extending the "golden hour" of shock tolerance, and suspended animation for delayed resuscitation.

Do standard monitoring sites affect true brain temperature when hyperthermia is rapidly induced and reversed

BACKGROUND

Accurate measurements of brain and core temperatures during warming and cooling of the whole organism, accidentally or therapeutically, are important for studies of thermoregulation and cerebral insults and resuscitation.

HYPOTHESIS

During steady states and normal circulation, temperatures in the brain, nasopharynx, esophagus and rectum (the latter are core temperatures) equilibrate quickly; and that during rapid cooling or warming, slight temperature gradients occur, with esophageal core temperature reflecting brain temperature better than rectal temperature.

METHODS

We evaluated 5 mongrel dogs and 12 pigtail monkeys. The animals were exposed to total body hyperthermia by immersion into water at 45 degrees C to achieve cerebral temperature 42 degrees C which was maintained until cardiac arrest. In monkeys, at cardiac arrest, surface cooling and cardiopulmonary resuscitation were attempted for up to 30 min to determine resuscitability at 38.5 degrees C. Continuously monitored were brain (epidural) (Tep), esophageal (Tes), rectal (Tre) and nasopharyngeal temperatures (Tnp). Also monitored were mean arterial pressure and intracranial pressure.

RESULTS

At normothermia, in dogs and monkeys, Tep, Tre, Tes and Tnp correlated well. In the dogs, during heating, Tes, Tnp and Tre at first correlated well. Vigorous panting started as Tep reached 41 degrees C, which immediately lowered Tnp and Tep to increase less steeply than Tes and Tre. After about 40 min of panting, with cerebral perfusion pressure still normal, Tep decreased sharply and reached the levels of Tnp, while Tre remained high. In the monkeys during heating, Tep, Tes and Tre correlated well. When cerebral perfusion pressure decreased below 50 mmHg, Tep declined significantly as compared with Tre, which continued to be high in severe arterial hypotension. Tes at that time achieved levels between Tep and Tre. During cooling in monkeys, the decline in Tre was slower as compared with the decline in Tes and Tep.

CONCLUSIONS

In normal dogs and monkeys, rectal, esophageal and nasopharyngeal temperatures are almost identical with brain temperatures; but during rapid external warming or cooling, brain temperature is reflected in nasopharyngeal temperature, somewhat in higher esophageal temperature, but not in even higher rectal temperature. For clinical monitoring during temperature changes, one should use primarily esophageal temperature and, if feasible, brain (epidural) temperature as well.

Therapeutic hypothermia in traumatology

Despite its proven clinical application for protection-preservation of the brain and heart during cardiac surgery, hypothermia research has fallen in and out of favor many times since its inception. Since the 1980s, there has been renewed research and clinical interest in therapeutic hypothermia for resuscitation of the brain after cardiac arrest or TBI and for preservation-resuscitation of extracerebral organs, particularly the abdominal viscera in low-flow states such as HS. Although some of the fears regarding the side effects of hypothermia are warranted, others are not. Without further laboratory and clinical studies, the significance of these effects cannot be determined and ways to overcome these problems cannot be developed. Currently, at the turn of the century, there are significant data demonstrating the benefit of mild-to-moderate hypothermia in animals and humans after cardiac arrest or TBI and in animals during and after HS. The clinical implications of uncontrolled versus controlled hypothermia in trauma patients and the best way to assure poikilothermia for cooling without shivering are still unclear. It is time to consider a prospective trial of therapeutic, controlled hypothermia for patients during traumatic HS and resuscitation. The authors believe that the new millennium will witness remarkable advantages of the use of controlled hypothermia in trauma. Starting in the prehospital phase, mild hypothermia will be induced in hypovolemic patients, which will not only decrease the immediate mortality rate but perhaps also will protect cells and reduce the likelihood of secondary inflammatory response syndrome, multiple organ failure, and late deaths. The most futuristic applications will be hypothermic strategies to achieve prolonged suspended animation for delayed resuscitation in traumatic exsanguination cardiac arrest.

Hypothermic aortic arch flush for preservation during exsanguination cardiac arrest of 15 minutes in dogs

BACKGROUND

Trauma victims rarely survive cardiac arrest from exsanguination. Survivors may suffer neurologic damage. Our hypothesis was that a hypothermic aortic arch flush of 500 mL of isotonic saline solution at 4 degrees C, compared with 24 degrees C (room temperature), administered at the start of prolonged exsanguination cardiac arrest (CA) would improve functional neurologic outcome in dogs.

METHODS

Seventeen male hunting dogs were prepared under light N2O-halothane anesthesia. The animals were randomized into two groups: group I (n = 9) received 4 degrees C isotonic saline flush and group II (n = 6) received 24 degrees C flush. Two additional dogs received no flush. While spontaneously breathing, the dogs underwent normothermic (tympanic membrane temperature [Ttm] = 37.5 degrees C) exsanguination over 5 minutes to cardiac arrest, assured by electric induction of ventricular fibrillation. After 2 minutes of arrest, the flush was administered over 1 minute into the aortic arch by means of a 13 French balloon-tipped catheter inserted by means of the femoral artery. After 15 minutes of CA, resuscitation was with closed-chest cardiopulmonary bypass, return of shed blood, and defibrillation. For the first 12 hours after CA, core temperature was maintained at 34 degrees C. Mechanical ventilation was continued to 20 hours and intensive care to 72 hours, when final evaluation and perfusion-fixation killing for brain histologic damage scoring were performed.

RESULTS

Three dogs in group I were excluded because of extracerebral complications. All 14 dogs that followed protocol survived. During CA, the Ttm decreased to 33.6 +/- 1.2 degrees C in group I and 35.9 +/- 0.4 degrees C in group II (p = 0.002). At 72 hours, in group I, all dogs achieved an overall performance category (OPC) of 1 (normal). In group II, 1 dog was OPC 2 (moderate disability), 3 dogs were OPC 3 (severe disability), and 2 dogs were OPC 4 (coma). Both dogs without flush were OPC 4. Neurologic deficit scores (NDS 0% = normal, 100% = brain death) were 1 +/- 1% in group I and 41 +/- 12% in group II (p < 0.05). The two dogs without flush achieved an NDS of 47% and 59%. Total brain histologic damage scores were 35 +/- 28 in group I and 82 +/- 17 in group II (p < 0.01); and 124 and 200 in the nonflushed dogs.

CONCLUSION

At the start of 15 minutes of exsanguination cardiac arrest in dogs, hypothermic aortic arch flush allows resuscitation to survival with normal neurologic function and histologically almost clean brains.

Mild or moderate hypothermia but not increased oxygen breathing prolongs survival during lethal uncontrolled hemorrhagic shock in rats, with monitoring of visceral dysoxia

OBJECTIVE

To test the hypotheses that during lethal uncontrolled hemorrhagic shock (UHS) in rats compared with normothermia and room air breathing: a) mild hypothermia would prolong survival time as well as moderate hypothermia; b) oxygen breathing would prolong survival further; and c) hypothermia and oxygen would mitigate visceral ischemia (dysoxia) during UHS.

DESIGN

Prospective, randomized, controlled laboratory animal study.

SETTING

Animal research facility.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTION

Fifty-four rats were lightly anesthetized with halothane during spontaneous breathing. UHS was induced by blood withdrawal of 3 mL/100 g over 15 mins, followed by 75% tail amputation with topical application of heparin. Five minutes after tail cut, rats were randomly divided into nine groups (6 rats each) with three rectal temperature levels (38 degrees C [100.4 degrees F; normothermia] vs. 34 degrees C [93.2 degrees F; mild hypothermia] vs. 30 degrees C [86 degrees F; moderate hypothermia]) by surface cooling; each with 3 FIO2 levels (0.25 vs. 0.5 vs. 1.0). Rats were observed without fluid resuscitation until death (apnea and pulselessness). Visceral ischemia was monitored by observing liver and gut surface PCO2.

MEASUREMENTS AND MAIN RESULTS

Mean survival time, which was 51 mins in the control group with normothermia and FIO2 of 0.25, was more than doubled with hypothermia, to 119 mins in the combined mild hypothermia groups (p < .05) and to 132 mins in the combined moderate hypothermia groups (p < .05; NS for moderate vs. mild hypothermia). FIO2 had no statistically significant effect on survival time. Increases in visceral surface PCO2 correlated with hypotension (r2 = .22 for intestine and .40 for liver). Transiently, increased FIO2, not hypothermia, mitigated visceral ischemia.

CONCLUSIONS

Both mild and moderate hypothermia prolonged survival time during untreated, lethal UHS in rats. Increased FIO2 had no effect on survival. The effects of hypothermia and increased FIO2 during UHS on viscera, the ability to be resuscitated, and outcome should be explored further.

Life supporting first aid training of the public--review and recommendations

Since the introduction around 1960 of external cardiopulmonary resuscitation (CPR) basic life support (BLS) without equipment, i.e. steps A (airway control)-B (mouth-to-mouth breathing)-C (chest (cardiac) compressions), training courses by instructors have been provided, first to medical personnel and later to some but not all lay persons. At present, fewer than 30% of out-of-hospital resuscitation attempts are initiated by lay bystanders. The numbers of lives saved have remained suboptimal, in part because of a weak or absent first link in the life support chain. This review concerns education research aimed at helping more lay persons to acquire high life supporting first aid (LSFA) skill levels and to use these skills. In the 1960s, Safar and Laerdal studied and promoted self-training in LSFA, which includes: call for the ambulance (without abandoning the patient) (now also call for an automatic external defibrillator); CPR-BLS steps A-B-C; external hemorrhage control; and positioning for shock and unconsciousness (coma). LSFA steps are psychomotor skills. Organizations like the American Red Cross and the American Heart Association have produced instructor-courses of many more first aid skills, or for cardiac arrest only-not of LSFA skills needed by all suddenly comatose victims. Self-training methods might help all people acquire LSFA skills. Implementation is still lacking. Variable proportions of lay trainees evaluated, ranging from school children to elderly persons, were found capable of performing LSFA skills on manikins. Audio-tape or video-tape coached self-practice on manikins was more effective than instructor-courses. Mere viewing of demonstrations (e.g. televised films) without practice has enabled more persons to perform some skills effectively compared to untrained control groups. The quality of LSFA performance in the field and its impact on outcome of patients remain to be evaluated. Psychological factors have been associated with skill acquisition and retention, and motivational factors with application. Manikin practice proved necessary for best skill acquisition of steps B and C. Simplicity and repetition proved important. Repetitive television spots and brief internet movies for motivating and demonstrating would reach all people. LSFA should be part of basic health education. LSFA self-learning laboratories should be set up and maintained in schools and drivers' license stations. The trauma-focused steps of LSFA are important for 'buddy help' in military combat casualty care, and natural mass disasters.

Glucose plus insulin infusion improves cerebral outcome after asphyxial cardiac arrest

Hyperglycemia before ischemia worsens cerebral outcome. The aim of this study was to determine the cerebral effects of giving glucose with or without insulin after asphyxial cardiac arrest. Rats underwent 8 min of asphyxial cardiac arrest. After arrest, Group 1 received NaCl; Group 2, insulin; Group 3, glucose; and Group 4, glucose plus insulin, all intravenously. Neurological deficit (ND) scores were 14+/-10%, 22+/-12%, 12+/-10% and 2+/-2% in Groups 1-4, respectively, 72 h after reperfusion. Overall histological damage (HD) scores were 4, 2, 3 and 1, respectively. Group 4 fared significantly better than group 1 on both scores. Glucose after asphyxial cardiac arrest in rats produces no increased brain damage while glucose plus insulin improves cerebral outcome.

Prolonged severe hemorrhagic shock and resuscitation in rats does not cause subtle brain damage

OBJECTIVE

Some patients who survived severe hemorrhagic shock (HS) seem to exhibit persistent subtle neurobehavioral deficits. This finding is of concern if limited hypotensive fluid resuscitation is applied in hypotensive victims with penetrating trauma. This study was designed to determine whether subtle brain damage would occur in rats after severe prolonged HS. We hypothesized that rats surviving HS with mean arterial pressure (MAP) controlled at 40 mm Hg for 60 minutes would recover with slight permanent brain damage in terms of cognitive function without morphologic loss of neurons and that rats surviving HS with MAP at 30 mm Hg for 45 minutes (60 minutes were not tolerated) would have grossly abnormal brain function and loss of neurons.

METHODS

Under light nitrous oxide-halothane anesthesia, spontaneously breathing rats underwent MAP-controlled HS (HS phase I), volume resuscitation to normotension and invasive monitoring to 60 minutes (resuscitation phase II), and observation to 10 days with detailed assessment of cognitive function (observation phase III). Five conscious rats served as normal controls. Three treatment groups were compared: group 1, shams (11 of 12 rats survived to 10 days); group 2, HS at MAP 40 mm Hg for 60 minutes (10 of 17 rats survived); group 3, HS at 30 mm Hg for 45 minutes (10 of 14 rats survived).

RESULTS

On post-HS day 10, all normal controls and all survivors of all three groups were functionally normal with overall performance category = 1 (normal) (overall performance category 1 = normal, 5 = death) and neurologic deficit scores < or = 7% (neurologic deficit scores 0-10% = normal, 100% = brain death). Post-HS beam balance, beam walking, and Morris water maze test results in HS groups 2 and 3 showed latencies not significantly different from those in shams and normal controls. Light microscopic scoring of five selectively vulnerable brain regions and other regions in five coronal sections revealed no ischemic (pyknotic, shrunken, eosinophilic) neurons in any of the survivors to 10 days. There was no statistical difference between normal controls, sham animals, and both HS groups in the number of normal neurons counted in the hippocampal CA-1 region in the 10-day survivors. All nonsurvivors died with intestinal necrosis.

CONCLUSION

HS at MAP 40 mm Hg for 60 minutes or MAP 30 mm Hg for 45 minutes does not cause subtle functional or histologic brain damage in surviving rats. Controlling MAP at 30 mm Hg carries a risk of sudden cardiac arrest. These data suggest that limited fluid resuscitation, to maintain MAP at about 40 mm Hg, as recommended for victims of penetrating trauma with uncontrolled HS, is safe for the brain.

Delayed death after uncomplicated hot tub bathing in dogs and monkeys

Prolonged heat exposure as in hot tub bathing, although frequently practiced, has occasionally resulted in fatalities that have been explained by an underlying disease. We explored the tolerance of hot water immersion of 60 min in five previously healthy animals (three dogs and two monkeys). With invasive monitoring, experimental body immersion in water at 40-45 degrees C, with core temperature kept at 40-42 degrees C for 60 min, caused no significant cardiovascular, pulmonary or metabolic changes during hyperthermia or for 2 h after return to normothermia. Then secondary deterioration occurred with progressive hypotension, petechial hemorrhages throughout the viscera, gross gastrointestinal hemorrhages and irreversible (hypovolemic) shock. These effects occurred earlier in the monkeys than in the dogs. This shock state did not respond to standard resuscitation attempts. One dog survived the secondary shock state. We conclude that during and after hot tub immersion, good initial tolerance to heat exposure can, several hours after return of normothermia, result in delayed secondary deterioration and death. We recommend that the mechanism of this delayed shock state with apparent capillary leakage be clarified.

Moderate hypothermia for 48 hours after temporary epidural brain compression injury in a canine outcome model

In a previous study with this dog model, post-insult hypothermia of 31 degrees C for 5 h prevented secondary intraventricular pressure (IVP) rise, but during 35 degrees C or 38 degrees C, one-half of the dogs developed delayed IVP rise to brain death. We hypothesized that 31 degrees C extended to 48 h would prevent brain herniation. Using epidural balloon inflation, we increased contralateral IVP to 62 mm Hg for 90 min. Controlled ventilation was to 72 h and intensive care to 96 h. Group 1 dogs (n = 10) were normothermic controls (37.5 degrees C). Group 2 dogs (n = 10) were surface-cooled from 15 to 45 min of balloon inflation and maintained at moderate hypothermia (31 degrees C) to 48 h. Rewarming was from 48 to 72 h. Four additional dogs of hypothermia Group 2 had to be excluded from analysis for pneumonia and/or bleeding diathesis. After balloon deflation, IVP increased to 20 mm Hg or greater at 154 +/- 215 (range 15-720) min following the insult in Group 1 and at 1394 +/- 1191 (range 210-3420) min in Group 2 (p = 0.004), still during 31 degrees C but without further increase during hypothermia. Further IVP rise led to brain death in Group 1 in 6 of 10 dogs at 44 +/- 18 (range 21-72) h (all during controlled ventilation); and in Group 2, in 6 of 10 dogs at 87 +/- 11 (range 72-96) h (p = 0.001), all after rewarming, during spontaneous breathing. Survival to 96 h was achieved by 4 of 10 dogs in Group 1, and by 7 of 10 dogs in Group 2 (NS). Three of the six brain deaths in Group 2 occurred at 96 h. The macroscopically damaged brain volume was only numerically smaller in Group 2. The vermis downward shift was 6.8 +/- 3.5 mm in Group 1, versus 4.7 +/- 2.2 mm in Group 2 (p = 0.05). In an adjunctive study, in 4 additional normothermic dogs, hemispheric cerebral blood flow showed post-insult hypoperfusion bilaterally but no evidence of hyperemia preceding IVP rise to brain death. In conclusion, in this model, moderate hypothermia during and for 48 h after temporary epidural brain compression can maintain a low IVP during hypothermia but cannot prevent lethal brain swelling after rewarming and may cause coagulopathy and pulmonary complications.

Hypothermia, but not 100% oxygen breathing, prolongs survival time during lethal uncontrolled hemorrhagic shock in rats

OBJECTIVE

To test the hypothesis that moderate hypothermia (Hth) (30 degrees C) or breathing 100% oxygen (best with both combined) would prolong survival during lethal uncontrolled hemorrhagic shock (UHS) compared with normothermia (38 degrees C) and breathing air.

METHODS

Forty Sprague-Dawley rats were anesthetized with halothane during spontaneous breathing of N2O/O2 (50:50). UHS was induced by volume-controlled blood withdrawal of 3 mL/100 g over 15 minutes, followed by 75% tail amputation and randomization to one of four UHS treatment groups (10 rats each): group 1 (control) was maintained on room air and rectal temperature of 38 degrees C; group 2 (Hth) was maintained on air and 30 degrees C; group 3 (O2) was maintained on FiO2 100% (starting immediately after tail cut) and 38 degrees C; and group 4 (O2-Hth) was maintained on FiO2 100% and 30 degrees C. Rats were observed otherwise untreated until death (apnea and pulselessness) or for a maximum of 5 hours.

RESULTS

During the initial blood withdrawal, mean arterial pressure (MAP) decreased to an average of 24 mm Hg. Seventeen of 40 rats then showed an increase in MAP (attempted self-resuscitation). Induction of hypothermia increased MAP to around 35 mm Hg at 30 minutes but did not increase bleeding. Additional blood loss from the tail stump averaged 1.0, 2.3, 2.9, and 1.7 mL in groups 1, 2, 3, and 4, respectively (not significant). Breathing 100% oxygen did not affect MAP or blood loss. Survival time was a mean of 47 and 52 minutes in normothermic groups 1 and 3 versus 121 and 135 minutes in hypothermic groups 2 and 4, respectively (p < 0.001, Kaplan-Meier). Breathing FiO2 100% increased PaO2 but did not change MAP, blood loss, or survival time.

CONCLUSION

Moderate hypothermia, but not increased FiO2, prolonged survival time during untreated UHS in rats. The effect of hypothermia on survival after resuscitation from UHS needs to be determined.

Mapping the active site of factor Xa by selective inhibitors: an NMR and MD study

The structure of two selective inhibitors, Ac-Tyr-Ile-Arg-Ile-Pro-NH2 and Ac-(4-Amino-Phe)-(Cyclohexyl-Gly)-Arg-NH2, in the active site of the blood clotting enzyme factor Xa was determined by using transferred nuclear Overhauser effect nuclear magnetic resonance (NMR) spectroscopy. They represent a family of peptidic inhibitors obtained by the screening of a vast combinatorial library. Each structure was first calculated by using standard computational procedures (distance geometry, simulated annealing, energy minimization) and then further refined by systematic search of the conformation of the inhibitor docked in the active site and repeating the simulated annealing and energy minimization. The final structure was optimized by molecular dynamics simulations of the inhibitor-complex in water. The NMR restraints were kept throughout the refinement. The inhibitors assume a compact, very well defined conformation, embedded into the substrate binding site not in the same way as a substrate, blocking thus the catalysis. The model allows to explain the mode of action, affinity, and specificity of the peptides and to map the active site.

Discovery of a novel, potent, and specific family of factor Xa inhibitors via combinatorial chemistry

A series of low molecular weight peptide inhibitors of factor Xa, unrelated to any previously described, was identified by screening a combinatorial peptide library composed of L-amino acids. The minimal inhibitory sequence is a tripeptide, L-tyrosinyl-L-isoleucyl-L-arginyl, which competitively inhibits the hydrolysis of small chromogenic substrates by factor Xa but binds in an orientation which prevents a productive nucleophilic attack by serine 195 of the catalytic triad on the carbonyl carbon of the carboxyterminal arginine. The initial leads identified in an octamer combinatorial peptide library ranged in potency from 4 to 15 microM. These peptides were modified into peptide mimetics with a greater than 1000-fold increase in potency while retaining unusual selectivity for factor Xa over the related serine proteases thrombin, factor VIIa/tissue factor, plasmin, activated protein C, kallikrein, and trypsin. One of the most potent analogues, SEL 2711, with a Ki of 0.003 microM for factor Xa and 40 microM for thrombin, is active in in vitro and ex vivo coagulation assays, suggesting the potential application of these inhibitors in anticoagulant therapy.