A randomized, controlled trial comparing arteriovenous to venovenous rewarming of severe hypothermia in a porcine model

BACKGROUND: The purpose of this study was to evaluate active rewarming using continuous arteriovenous rewarming (CAVR) and continuous venovenous rewarming (CVVR) methods during severe hypothermia using an electromagnetic fluid warmer. Rapid rewarming using these techniques is superior to passive rewarming and is possible with commercially available equipment. METHODS: Eighteen swine (55-65 kg) were assigned to CAVR, CVVR, or control. Vascular access was obtained via central lines (8.5-French) in all subjects. Subjects were cooled to 27 degrees C (80.6 degrees F) in an ice bath, and then dried, covered, and connected to the rewarming device. The carotid artery (CAVR) or internal jugular vein (CVVR) was used for circuit inflow. Warmed 39 degrees C (102.2 degrees F) blood was returned via the femoral vein. Hemodynamic parameters and temperatures (pulmonary artery and rectal) were recorded until reaching an endpoint of a pulmonary artery temperature of 37 degrees C (98.6 degrees F). RESULTS: Mean rewarming time in the CAVR group was 2 hours 14 minutes, with a mean rewarming rate of 4.5 degrees C/h (8.1 degrees F/h, 0.034 degrees C/kg/h). Total circulating volume averaged 65 L. CVVR averaged 3 hours 8 minutes, with a mean rewarming rate of 3.2 degrees C/h (5.8 degrees F/h, 0.024 degrees C/kg/h). Total circulating volume averaged 67 L. Controls averaged 10 hours 42 minutes, with a mean rate of 0.9 degrees C/h (1.7 degrees F/h, 0.007 degrees C/kg/h). The CAVR group was faster than the CVVR group in both the rewarming rate and total time to rewarming (p = 0.034 and p = 0.040, respectively). Both experimental groups were significantly different from controls in rewarming rate and total time to rewarming (p < 0.001). CONCLUSION: CAVR offers the most rapid rate of rewarming. CVVR offers a rapid rate using less invasive procedures. Both techniques are markedly superior to passive rewarming methods typically used during early resuscitation.     

Elevation in compartment pressure following hypovolemic shock and fluid resuscitation: a canine model

We induced hemorrhagic shock in seven dogs and then resuscitated them with intravenous (IV) lactated ringers. We then monitored anterior leg compartment pressures via a slit catheter during both bleeding and reperfusion. These values were compared with controls that received IV fluids without being bled. Compartment pressures in resuscitated dogs rose well above control values. These values were statistically significant when compared to controls via the paired student t test (P < .01). This model demonstrates that sufficient swelling occurs to significantly elevate compartment pressures, even in the absence of local trauma. While this elevation may not be sufficient enough to cause a compartment syndrome, it reinforces the notion that extremities that have experienced ischemia and reperfusion are at an increased risk for developing compartment syndrome.     

Ultraprofound hypothermia with complete blood substitution in a canine model

The potential for hypothermia to prevent or ameliorate ischemic injury to the central nervous system is well known. To determine if a more prolonged period of metabolic suppression with blood substitution is possible, a method was developed to lower body temperature to near the freezing point. Eight adult mongrel dogs underwent closed-chest extracorporeal circulation with both external and internal body cooling. As they were cooled, progressive hemodilution was employed until complete exsanguination and blood substitution with an aqueous solution was accomplished. Continuous circulation and a core temperature at a mean of 1.7 degrees C were maintained from 2 1/2 to 3 hours. After rewarming to 20 degrees C, the animals were autotransfused and allowed to recover. Of the eight animals, two died due to technical factors related to cardiac defibrillation. Of the six surviving animals, five survived over a long period and one died on the 10th postoperative day with hepatorenal failure resulting from a presumed blood transfusion incompatability reaction. All six showed normal neurological function and kennel behavior, except one dog with mild weakness of a hindlimb. When the dogs were sacrificed 1 to 2 months postoperatively, all organs were histologically normal. Specifically, there was no gross or microscopic evidence of ischemic or hypoxic injury to any central nervous system structures. This pilot study demonstrates that it is possible to successfully achieve complete exsanguination, blood substitution, and ultraprofound body temperature, while continuous circulation of the blood substitute is maintained. With the capability of controlling and repeatedly performing washout of the extracellular environment and by reaching lower temperatures, it may be possible to attain greater cellular metabolic suppression. This perhaps will extend the allowable times for circulatory arrest procedures. In addition, "bloodless ischemia" may be beneficial in removing both blood substances and formed elements which may mediate organ ischemia. With replacement of blood at warm temperatures, coagulopathy is avoided. This preliminary evidence demonstrates potential in the combination of ultraprofound hypothermia and complete blood component substitution. However, further study is required to confirm the potential of achieving circulatory arrest of longer duration.     

Effect of moderate hypothermia in the treatment of canine hemorrhagic shock.

This study evaluated a possible protective and therapeutic effect of moderate hypothermia in the treatment of severe hemorrhagic shock. A modified Wiggers shock preparation was used. Normothermic dogs (Group I, N = 6) were maintained at normal body temperature throughout hemorrhagic shock and resuscitation. In Group II, hypothermia was initiated after 15 minutes of hemorrhagic shock (N = 12) and maintained for 60 minutes after fluid resuscitation. Animals were then rewarmed with Group IIA (N = 7) receiving sodium bicarbonate to correct acidosis, while Group IIB (N = 5) did not; all dogs were studied for an additional 120 minutes. During shock heart rate was lower in both hypothermic groups (IIA and IIB) compared to normothermic dogs (85.0 +/- 3.9, 77.7 +/- 4.6 vs. 136.7 +/- 4.2, respectively, p less than 0.05), while +dP/dt (mmHg/s) remained stable in all dogs. Furthermore, pH was lower in the hypothermic (Groups IIA and IIB) compared to normothermic animals at this time period (Group IIA: 7.19 +/- 0.02, Group IIB: 7.13 +/- 0.02 vs. Group I: 7.24 +/- 0.02). Arterial pCO2 was higher in the hypothermic hemorrhagic shock Groups IIA and IIB compared to normothermic group (34.5 +/- 2.2, 37.4 +/- 2.2 vs. 20.3 +/- 20,3 +/- 2.0, p less than 0.05) due to hypothermia-depressed respiration. A higher myocardial O2 consumption and a negative myocardial lactate balance occurred in the normothermic animals during hemorrhagic shock. After resuscitation and rewarming, stroke volume (mL/beat) and cardiac output (L/min) were lower in hypothermic animals with persistent acid-base derangements (12.6 +/- 2.5, 1.3 +/- 3.0, respectively) compared to hypothermic dogs with acid-base correction (20.1 +/- 3.3, 2.2 +/- 0.3) and normothermic dogs (24.6 +/- 3.0, 3.0 +/- 0.3, p less than 0.05), while myocardial O2 extraction and myocardial lactate production were higher. Results suggest hypothermia decreases the metabolic needs and maintains myocardial contractile function in hemorrhagic shock. Hypothermia may have a beneficial effect and, with normalization of acid-base balance, a therapeutic role in hemorrhagic shock.     

Continuous arteriovenous rewarming: experimental results and thermodynamic model simulation of treatment for hypothermia

We evaluated a technique for treating hypothermia that uses extracorporeal circulation but does not require heparin or pump assistance. Hypothermia to 29.5 degrees C was induced in eight anesthetized dogs, and thermistors placed in the pulmonary artery, liver, bladder, esophagus, rectum, muscle, and skin. Four experimental animals were rewarmed by creating a fistula which connected arterial and venous femoral lines to an interposed counter-current heat exchanger. External rewarming was used in four controls. Bleeding time (BT), coagulation profile (PT, PTT, TT), and cardiac output (CO) were measured during rewarming. Core temperature (T) rose significantly faster with CAVR (0.00001). Average time to rewarming was 45 min, vs. 4 hrs in controls. Haptoglobin, platelet, fibrinogen, and fibrin split product levels were unaffected. Continuous arteriovenous rewarming (CAVR) improved T, CO, BT, and coagulation profile faster than any method yet reported not requiring heparin or cardiac bypass. The application of CAVR in post-traumatic hypothermia warrants further investigation.     

Perfusion without systemic heparinization for rewarming in accidental hypothermia

We report on a patient with accidental deep hypothermia (23.3 degrees C) and cardiorespiratory arrest resulting from severe craniocerebral injury. Systemic anticoagulation was contraindicated, and the decision was reached to rewarm the patient with cardiopulmonary bypass without systemic heparinization using heparin-coated perfusion equipment. The patient was successfully rewarmed, was weaned from cardiopulmonary bypass, and recovered.     

Feasibility of a novel veno-veno circuit as a central rewarming method in a severely hypothermic canine model

PURPOSE: Many victims of accidental hypothermia are successfully resuscitated, but questions remain regarding the optimum rewarming techniques. Most of the invasive warming techniques such as closed thoracic lavage, hemodialysis, peritoneal dialysis, and cardiopulmonary bypass require specialized personnel, equipment, and procedures that are not readily available in all facilities. The objective of this study was to investigate the technical feasibility of utilizing a novel veno-veno rewarming circuit to resuscitate severely hypothermic subjects. If this alternative invasive warming technique is successful, it could be available to treat hypothermic patients in virtually any emergency department setting. METHODS: The rewarming system consisted of a Baxter ThermaCyl warmer (Baxter Co., McGaw Park, IL), a roller pump, hemodialysis tubing, connectors, and 2 venous catheters. Blood was pumped from the body via the femoral vein, through the roller pump, into the warmer, and then returned to the body via the right jugular vein. Seven adult mongrel hounds of similar weights (20 to 25 kg) were anesthetized and instrumented for data collection. Temperature probes were placed in the rectum, the peritoneal cavity, and the esophagus to record core temperatures. Each animal was cooled by ice packing to a central core temperature of 29 degrees C and then rewarmed using the described veno-veno circuit. Vital signs, pulse oximetry, cardiac rhythm, and laboratory values were obtained prior to cooling the animals, and were repeated for every degree Celsius change once warming began. Christopher Haughn, MD, was the second place winner in the Basic Sciences Resident Competition at the Ohio American College of Surgeons meeting. RESULTS: Because of technical difficulties, data from 1 dog were not included in the results. Of the remaining 6 dogs, all were rewarmed from 29 degrees C to 37 degrees C. Adverse side effects included gross hematuria, acidemia (median pH decrease was 0.088), and decreases in haptoglobin (median decrease 13.5 g/dl), hemoglobin (median decrease 1.35 g/dl), and arterial pO(2) level (median decrease 167 mm Hg). Decreases in blood pressure and heart rate were also noted during the cooling process, but reversed upon rewarming. CONCLUSIONS: From this pilot study, we conclude that our novel veno-veno circuit rewarming is a feasible method of rewarming hypothermic subjects and warrants further investigation and comparison with other active warming methods.     

Partial cardiopulmonary bypass for core rewarming in profound accidental hypothermia

Six cases of treatment of severe accidental hypothermia using cardiopulmonary bypass for core rewarming are reported and eleven cases from the literature are analyzed. Thirteen patients survived. Overall survival was more likely in patients who had vital signs initially. Initial mean core temperatures in the new cases was 22.8 C. Surface and conventional core rewarming methods resulted in an average temperature increase of 2.4 C per hr. Electrical defibrillation was generally without success until the core temperature had been raised to above 30 C. Between one and six hours after admission, partial femoral-femoral cardiopulmonary bypass (CPB) for core rewarming was started, causing a mean temperature increase of 9.5 C per hr. Four patients required a thoracotomy. Two patients had a massively dilated heart with contusions, and could not be weaned off bypass. None of the four long-term survivors had a demonstrable central nervous system (CNS) deficit. All patients developed temporary pulmonary problems; two developed wound infections. The average hospital stay was 21 days. CPB for core rewarming allows circulatory support while avoiding myocardial damage from prolonged external cardiac massage; rapidly increases the myocardial temperature and counteracts myocardial temperature gradients so that DC electroversion is successful; avoids "rewarming shock"; and improves microcirculatory flow. A prospective randomized trial to compare rapid surface rewarming and CPB rewarming is suggested. Immediate CPB for rewarming is recommended for patients in ventricular fibrillation with core temperatures below 30 C. Prolonged external cardiac massage (ECM) should not be used. The value of surface rewarming and non-CPB core rewarming methods remains undefined.     

Continuous arteriovenous rewarming: report of a new technique for treating hypothermia

Survival is rare after major trauma if core temperature falls below 32 degrees C. Available rewarming methods are often ineffective. We utilized arterial and venous catheters to create a circulatory fistula through the heating mechanism of a modified commercially available counter-current fluid warmer to achieve simple, rapid extracorporeal rewarming.     

Staged correction of surgical pathology of the stomach ("Damage Control") in conditions of decompensated hypovolemic shock

Based on an analysis of results of treatment of 184 patients the authors make a conclusion that staged surgical correction is an expedient method for traumas of the abdomen and acute intestinal obstruction with necrosis of the bowel.     

犬低血容量休克时血流动力学变化的研究

为探讨失血性休克时血流动力学的变化，用１４只犬进行了研究。实验发现随失血量的增加，犬中心静脉压（ＣＶＰ）、肺毛细血管嵌压（ＰＣＷＰ）、平均动脉压（ＭＡＰ）、平均肺动脉压（ＭＰＡＰ）、每搏量（ＳＶ）、心排血量（ＣＯ））均逐渐降低，周围血管阻力（ＳＶＲ）、肺血管阻力（ＰＶＲ）则逐渐升高。ＳＶ、ＣＯ对失血后反应最为敏感，且能反映失血性休克的严重程度。提示临床在大型手术，估计术中失血较多或需对失血性休克情况作出判断时，全面的血流动力学监测是必要的。     

Efficacy of propofol in controlling myoclonus during rewarming in a brain hypothermia patient

Propofol is an intravenous anaesthetic agent having anticonvulsant property. We report here a case in which propofol was effective in controlling myoclonus during rewarming in brain hypothermia patient. A 35-year-old male patient was admitted in a comatose state with right-sided hemiparesis, anisocoria and absence of bilateral light reflex. On admission, a head CT showed traumatic subarachnoid hemorrhage, left subdural hematoma, 10 mm midline shift and tentorial herniation with massive brain swelling together with extensive hypodensity in the frontal, temporal and occipital lobes bilaterally. Left decompressive hemicraniectomy, removal of hematoma and brain hypothermia therapy were started immediately. Postoperative head CT showed 15 mm midline shift. The temperature of the jugular bulb was maintained at 34 degrees C for 2 days together with sedation using midazolam under artificial ventilation. The patient was gradually rewarmed at a rate of 0.5 degree C per day from the third hospital day. Myoclonus of sudden onset developed on the patient's head and upper extremities on the third hospital day. An intravenous bolus injection of 10 mg midazolam and continued intravenous infusion of midazolam were given but they did not completely stop myoclonus. A bolus of propofol 60 mg was given intravenously and continuous intravenous infusion of propofol 2 mg.kg-1.hr-1 was started after which the progression of myoclonus disappeared. Myoclonus was kept controlled until the continuous intravenous infusion of midazolam and propofol was discontinued on the sixth hospital day, after which myoclonus occurred again after extubation on the seventh hospital day. The clinical course of this case suggests that propofol might be an alternative effective agent to suppress refractory myoclonus.     

Efficacy of active core rewarming using fluid heating system HOTLINE before and during the operation in a patient with for panperitonitis in state of shock and hypothermia

A 62-year-old man was transported to the emergency room. He was in the state of shock and hypothermia of 34.2 degrees C. Fluid therapy was started using a HOTLINE to raise the body temperature, with vasopressors, vitamin B1 and sodium bicarbonate after checking arterial blood gas. Diagnosis of panperitonitis was made and operation was started immediately. We used HOTLINE before and during the operation. Body temperature returned to normal ranges, and hemodynamic state was stabilized at the end of the operation. After the operation, he received controlled artificial ventilation and nutrition support with intravenous hyperalimentation. Though he was complicated with disseminated intravascular coagulation, he went to general ward 17 days, and was discharged at 47 days after the operation. Sepsis accompanied with hypothermia leads to poor prognosis. We used fluid therapy with rapid-heating, and obtained good outcome. HOTLINE is effective for hypothermia in an emergency patient, because its effect is sure and does not obstruct the examination and management.     

Oxygen delivery and consumption during hypothermia and rewarming in the dog

Changes in oxygen consumption (VO2) and oxygen delivery (DO2) were compared in three groups of paralyzed, sedated dogs: 1) a group (n = 5) cooled to 29 degrees C and immediately rewarmed to 37 degrees C; 2) a group (n = 5) cooled to and maintained at 29 degrees C for 24 h, and then rewarmed; and 3) a group (n = 5) maintained at 37 degrees C for 24 h. During the cooling phase, in both the acute and prolonged hypothermia animals, VO2 and DO2 decreased significantly from control values (P less than 0.05). The decrease in DO2 occurred as a result of a similar decrease in cardiac index (CI; P less than 0.05) that was associated with a significant increase in systemic vascular resistance index (SVRI; P less than 0.05). Arteriovenous oxygen content difference (C(a-v)O2), O2 extraction ratio, mixed venous oxygen tension (PVO2), pH, and base deficit (BD) were not different from control values even during prolonged hypothermia. Normothermic control dogs also demonstrated a significant decrease in CI (P less than 0.05) at 24 h. Surface rewarming increased VO2 back to control values in the acute hypothermia group and to values above control (P less than 0.05) in the prolonged hypothermia group. DO2 remained below control in both groups, resulting in a significant increase in O2 extraction (P less than 0.05) and a decrease in PVO2 (P less than 0.05) in the prolonged hypothermia animals. Following rewarming administration of sodium nitroprusside returned DO2, CI, and SVRI to control values but did not increase VO2. All animals survived the study without need for inotropic support.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hypertonic saline in the traumatic hypovolemic shock: meta-analysis

Background

A wealth of evidence from animal experiments has indicated that hypertonic saline (HS) maybe a better choice for fluid resuscitation in traumatic hypovolemic shock in comparison with conventional isotonic saline. However, the results of several clinical trials raised controversies on the superiority of fluid resuscitation with HS. This meta-analysis was performed to better understand the efficacy of HS in patients with traumatic hypovolemic shock comparing with isotonic saline.

Materials and methods

According to the search strategy, we searched the PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials, which was completed on October 2013. After literature searching, two investigators independently performed the literature screening, assessment of quality of the included trials, and data extraction. Disagreements were resolved by consensus or by a third investigator if needed. The outcomes included mortality, blood pressure, fluid requirement, and serum sodium.

Results

Six randomized controlled trials were included in the meta-analysis. The pooled risk ratio for mortality at discharge was 0.96 (95% confidence interval [CI], 0.82–1.14), whereas the pooled mean difference for the change in systolic blood pressure from baseline and the level of serum sodium after infusion was 6.47 (95% CI, 1.31–11.63) and 7.94 (95% CI, 7.38–8.51), respectively. Current data were insufficient to evaluate the effect of HS on the fluid requirement for the resuscitation.

Conclusions

The present meta-analysis was unable to demonstrate a clinically important improvement in mortality after the HS administration. Moreover, we observed HS administration maybe accompanied with significant increase in blood pressure and serum sodium.