[Small-volume resuscitation for hypovolemic shock. Concept, experimental and clinical results]

Helping prometheus: liver protection in acute hemorrhagic shock

Acute hemorrhagic hypovolemic shock is caused by a significant high blood loss and leads to hemodynamic instability. The decrease in intravascular volume results in cellular hypoxia and finally in damage to organs such as the liver and the kidney. The liver plays a decisive role in the development or prevention of multiple organ failure after hemorrhagic shock. Despite the large number of experimental studies, the knowledge of pathophysiological mechanisms in the liver after hemorrhagic shock is incomplete. The aim of this mini review was to provide an overview of the pathophysiological changes in liver function after acute hemorrhagic shock and to address treatment options to improve liver perfusion.

[The concept of small volume resuscitation for preclinical trauma management. Experiences in the Air Rescue Service]

BACKGROUND

Prompt hemorrhage control and adequate fluid resuscitation are the key components of early trauma care. However, the optimal resuscitation strategy remains controversial. In this context the small volume resuscitation (SVR) concept with hypertonic-hyperoncotic solutions is a new strategy.

PATIENTS AND METHODS

This was a retrospective study in the Helicopter Emergency Medical Service over a 5-year period. Included were all major trauma victims if they were candidates for SVR (initially 4 ml HyperHaes/kg body weight, followed by conventional fluid resuscitation with crystalloids and colloids). Demographic data, type and cause of injury and injury severity score (ISS) were recorded and the amount of fluid volume and the hemodynamic profile were analyzed. Negative side-effects as well as sodium chloride serum levels on hospital admission were recorded.

RESULTS

A total of 342 trauma victims (male 70.2%, mean age 39.0 ± 18.8 years, ISS 31.6 ± 16.9, ISS>16, 81.6%) underwent prehospital SVR. A blunt trauma mechanism was predominant (96.8%) and the leading cause of injury was motor vehicle accidents (61.5%) and motorcycle accidents (22.3%). Multiple trauma and polytrauma were noted in 87.4% of the cases. Predominant was traumatic brain injury (73.1%) as well as chest injury (73.1%) followed by limb injury (69.9%) and abdominal/pelvic trauma (45.0%). Within the whole study group in addition to 250 ml HyperHaes, mean volumes of 1214 ± 679 ml lactated Ringers and 1288 ± 954 ml hydroxethylstarch were infused during the prehospital treatment phase. There were no statistically significant differences in the amount of crystalloids and colloids infused regarding the subgroups multisystem trauma (ISS>16), severe traumatic brain injury (GCS<9) and entrapment trauma compared to the total study group. In patients with an initial systolic blood pressure (SBP) >80 mmHg significantly less colloids (1035 ± 659 ml vs. 1288 ± 954 ml, p<0.006) were infused, whereas in patients with an initial SBP ≤ 80 mmHg significantly more colloids were infused (1609 ± 1159 ml vs. 1288 ± 954 ml, p<0.002). There was a statistically significant increase in systolic as well as diastolic blood pressure at all times of blood pressure measurement during prehospital treatment after bolus infusion of HyperHaes within the whole study group. The same applies to the subgroups multisystem trauma, severe traumatic brain injury and entrapment trauma. Minor negative side-effects were observed in 4 cases (1.2%). The mean serum sodium chloride profile on hospital admission was 146.9 ± 5.0 mmol/l, the base excess (BE) was -5.7 ± 5.3 mmol/l) and the pH was 7.3 ± 0.1.

CONCLUSION

The concept of small volume resuscitation provides early and effective hemodynamic control. Clinical side-effects associated with bolus infusion of hypertonic-hyperoncotic solutions are rare.

Does increased prehospital replacement volume lead to a poor clinical course and an increased mortality? A matched-pair analysis of 1896 patients of the Trauma Registry of the German Society for Trauma Surgery who were managed by an emergency doctor at the accident site

INTRODUCTION

Severe bleeding after trauma frequently leads to a poor outcome. Prehospital fluid replacement therapy is regarded as an important primary treatment option. Our study aimed to assess the influence of prehospital fluid replacement therapy on the post-traumatic course of severely injured patients in a retrospective analysis of matched pairs.

PATIENTS AND METHODS

The data of 51,425 patients of the Trauma Registry of the German Society for Trauma Surgery were analysed. The following patients were included: Injury Severity Score ≥ 16 points, primary admission, age ≥ 16 years, no isolated brain injury, transfusion of at least one unit of packed red blood cells (pRBC), systolic blood pressure ≥ 60 mmHg at the accident site. The patients were divided into two groups according to the following matched-pair criteria (low-volume: 0-1500 ml prehospital volume replaced; high-volume: ≥ 1501 ml prehospital volume): intubation at the accident site (yes/no), time from injury to hospital ± 10 min., means of rescue (emergency helicopter, MICU), Abbreviated Injury Scale (body regions), injury year, systolic blood pressure and age (years). All patients were managed by an emergency doctor at the accident site.

RESULTS

A total of 948 patients in each group met the inclusion criteria. Increasing replacement volume was associated with an increased need for transfusion (pRBCs: low-volume: 7 units, high-volume: 8.3 units; p<0.001) and a reduced ability to coagulate (prothrombin ratio (PR): low-volume: 68%, high-volume: 61.5%; p<0.001). Patients in shock (systolic BP<90 mmHg) upon admission to the hospital were equally in both groups (25.6%; p=0.98). Significantly higher lethality was observed in cases of increasing volume (low-volume: 22.7%, high-volume: 27.6%; p<0.01).

CONCLUSIONS

Excessive prehospital fluid replacement leads to an increased mortality rate. The results of this study support the concept of restrained volume replacement in the prehospital treatment of patients with severe trauma.

Influence of prehospital fluid resuscitation on patients with multiple injuries in hemorrhagic shock in patients from the DGU trauma registry

Background:

Severe bleeding as a result of trauma frequently leads to poor outcome by means of direct or delayed mechanisms. Prehospital fluid therapy is still regarded as the main option of primary treatment in many rescue situations. Our study aimed to assess the influence of prehospital fluid replacement on the posttraumatic course of severely injured patients in a retrospective analysis of matched pairs.

Materials and Methods:

We reviewed data from 35,664 patients recorded in the Trauma Registry of the German Society for Trauma Surgery (DGU). The following patients were selected: patients having an Injury Severity Score >16 points, who were ≥16 years of age, with trauma, excluding those with craniocerebral injuries, who were admitted directly to the participating hospitals from the accident site. All patients had recorded values for replaced volume and blood pressure, hemoglobin concentration, and units of packed red blood cells given. The patients were matched based on similar blood pressure characteristics, age groups, and type of accident to create pairs. Pairs were subdivided into two groups based on the volumes infused prior to hospitalization: group 1: 0-1500 (low), group 2: ≥2000 mL (high) volume.

Results:

We identified 1351 pairs consistent with the inclusion criteria. Patients in group 2 received significantly more packed red blood cells (group 1: 6.9 units, group 2: 9.2 units; P=0.001), they had a significantly reduced capacity of blood coagulation (prothrombin ratio: group 1: 72%, group 2: 61.4%; P≤0.001), and a lower hemoglobin value on arrival at hospital (group 1: 10.6 mg/dL, group 2: 9.1 mg/dL; P≤0.001). The number of ICU-free days concerning the first 30 days after trauma was significantly higher in group 1 (group 1: 11.5 d, group 2: 10.1 d; P≤0.001). By comparison, the rate of sepsis was significantly lower in the first group (group 1: 13.8%, group 2: 18.6%; P=0.002); the same applies to organ failure (group 1: 36.0%, group 2: 39.2%; P≤0.001).

Conclusion:

The high amounts of intravenous fluid replacement was related to early traumatic coagulopathy, organ failure, and sepsis rate.

Systematic analysis of hydroxyethyl starch (HES) reviews: proliferation of low-quality reviews overwhelms the results of well-performed meta-analyses

PURPOSE

Hydroxyethyl starch (HES) is a synthetic colloid used widely for resuscitation despite the availability of safer, less costly fluids. Numerous HES reviews have been published that may have influenced clinicians' practice. We have therefore examined the relationship between the methodological quality of published HES reviews, authors' potential conflicts of interest (pCOI) and the recommendations made.

METHODS

Systematic analysis of reviews on HES use.

RESULTS

Between 1975 and 2010, 165 reviews were published containing recommendations for or against HES use. From the 1990s onwards, favorable reviews increased from two to eight per year and HES's share of the artificial colloid market tripled from 20 to 60 %. Only 7 % (12/165) of these reviews of HES use contained meta-analyses; these 7 % had higher Overview Quality Assessment Questionnaire (OQAQ) scores [median (range) 6.5 (3-7)] than reviews without meta-analysis [2 (1-4); p < 0.001]. The rates of recommending against HES use are 83 % (10/12) in meta-analyses and 20 % (31/153) in reviews without meta-analysis (p < 0.0001). Fourteen authors published the majority (70/124) of positive reviews, and ten of these 14 had or have since developed a pCOI with various manufacturers of HES.

CONCLUSIONS

Low-quality HES reviews reached different conclusions than high-quality meta-analyses from independent entities, such as Cochrane Reviews. The majority of these low-quality positive HES reviews were written by a small group of authors, most of whom had or have since established ties to industry. The proliferation of positive HES reviews has been associated with increased utilization of an expensive therapy despite the lack of evidence for meaningful clinical benefit and increased risks. Clinicians need to be more informed that marketing efforts are potentially influencing scientific literature.

[Lethality and outcome in multiple injured patients after severe abdominal and pelvic trauma. Influence of preclinical volume replacement - an analysis of 604 patients from the trauma registry of the DGU]

BACKGROUND

Uncontrollable hemorrhaging after blunt trauma and the resulting hemorrhagic shock is still one of the main causes of death in trauma patients. Starting volume replacement before admission to hospital is one of the main pillars of immediate treatment. The statements concerning the quantity of the preclinically administered fluid are still controversial and have a low level of evidence in the literature. Massive abdominal trauma and unstable pelvic fractures belong to the most relevant causes of hemorrhagic shock. The aim of this study was to analyze the influence of the quantity of the preclinically administered fluid on the posttraumatic course of patients with massive abdominal and pelvic injuries.

PATIENTS AND METHODS

All patients of the trauma registry of the DGU (German Society for Trauma Surgery) who met the following criteria were included: injury severity score ≥16 points, primary admission to hospital, age ≥16 years, initial blood pressure <100 mmHg and transfusion of erythrocyte concentrate (EC). Out of this collective patients with an AIS abdomen ≥4 or an AIS pelvis ≥4 were analyzed. Both groups were divided into 4 subgroups subject to the preclinically infused volume (<1000 ml, 1000-2000 ml, 2001-3000 ml and >3000 ml).

RESULTS

Of the 375 patients with abdominal trauma and 229 patients with pelvic trauma were consistent with the inclusion criteria. In both groups an increasing volume replacement was associated with an increased need for transfusion and a reduction of the coagulation ability (Quick 61% in the case of <1000 ml versus 49.1% in the case of >3000 ml). The rescue time had a relevant influence on the quantity of preclinically infused volume (62 min for <1000 ml versus 88 min for >3000 ml). On admission to hospital the blood pressure values were on average the same in all patients (~ 95 mmHg). With an increasing volume a slight elevation of lethality was found as well as a significant increase of the transfused erythrocyte concentrates, a significant deterioration of coagulation and an increase of patients with mass transfusions.

CONCLUSION

In the case of a preclinical relevant bleeding after blunt pelvic or abdominal trauma moderate volume replacement (<1000 ml) results in an enhancement of the initial coagulation situation and in a reduction in the need for transfusion. The results of this study support the concept of a restrained volume therapy after massive trauma with and bleeding requiring transfusion.

The role of pre-hospital blood gas analysis in trauma resuscitation

Background

To assess, whether arterial blood gas measurements during trauma patient's pre-hospital shock resuscitation yield useful information on haemodynamic response to fluid resuscitation by comparing haemodynamic and blood gas variables in patients undergoing two different fluid resuscitation regimens.

Methods

In a prospective randomised study of 37 trauma patients at risk for severe hypovolaemia, arterial blood gas values were analyzed at the accident site and on admission to hospital. Patients were randomised to receive either conventional fluid therapy or 300 ml of hypertonic saline. The groups were compared for demographic, injury severity, physiological and outcome variables.

Results

37 patients were included. Mean (SD) Revised Trauma Score (RTS) was 7.3427 (0.98) and Injury Severity Score (ISS) 15.1 (11.7). Seventeen (46%) patients received hypertonic fluid resuscitation and 20 (54%) received conventional fluid therapy, with no significant differences between the groups concerning demographic data or outcome. Base excess (BE) values decreased significantly more within the hypertonic saline (HS) group compared to the conventional fluid therapy group (mean BE difference -2.1 mmol/l vs. -0.5 mmol/l, p = 0.003). The pH values on admission were significantly lower within the HS group (mean 7.31 vs. 7.40, p = 0.000). Haemoglobin levels were in both groups lower on admission compared with accident site. Lactate levels on admission did not differ significantly between the groups.

Conclusion

Pre-hospital use of small-volume resuscitation led to significantly greater decrease of BE and pH values. A portable blood gas analyzer was found to be a useful tool in pre-hospital monitoring for trauma resuscitation.

[Hypertonic saline solution for reduction of intracranial pressure. Are there doubts?]

Osmotherapy, i.e. the intravenous administration of hyperosmolar solutions, is one of the mainstays of therapy for reduction of a pathologically increased intracranial pressure, in addition to analgosedation and raising the upper body of the patient. The administration of mannitol as a osmotherapeutic agent is, however, marred by considerable side-effects. A possible alternative is the use of hypertonic saline solution (NaCl). The advantages and disadvantages of this option are considered as well as points still in question.

[The preclinical care of polytraumatized patients]

In industrially developed countries, trauma is the major mortality factor for people younger than 40 years. The preclinical management of polytraumatized patients influences the prognosis of mortality and morbidity. In this period, a number of decisions have to be made under unfavourable conditions and with limited time. This situation represents a great challenge for the whole rescue team. Diagnostic overview, protection of the vital functions under the special situation of shock, immobilization of the spine and the treatment of the isolated injuries are part of the preclinical management efforts. Rescue of the polytraumatized patient, organization and announcement of transfer and the protection of the rescue team have to be taken into account.

Small volume resuscitation with HyperHaes improves pericontusional perfusion and reduces lesion volume following controlled cortical impact injury in rats

The hyperosmolar and hyperoncotic properties of HyperHaes (HHES) might improve impaired posttraumatic cerebral perfusion. Possible beneficial effects on pericontusional perfusion, brain edema, and contusion volume were investigated in rats subjected to controlled cortical impact (CCI). Male Sprague-Dawley rats (n = 60) anesthetized with isoflurane were subjected to a left temporoparietal CCI. Thereafter, rats were randomized to receive HHES (10% hydroxyethylstarch, 7.5% NaCl) or physiological saline solution (4 mL/kg body weight) intravenously. Mean arterial blood pressure (MABP) and intracranial pressure (ICP) were determined before and following CCI, after drug administration and 24 h later. Regional pericontusional cortical perfusion was determined by scanning laser Doppler flowmetry before CCI, and 30 min, 4 and 24 h after injury. At 24 h brain swelling and water content were measured gravimetrically. At 7 days, cortical contusion volume was determined planimetrically. MABP was not influenced by HHES. ICP was significantly decreased immediately after HHES infusion (5.7 +/- 0.4 vs. 7.1 +/- 1.0 mm Hg; p < 0.05). Pericontusional cortical perfusion was significantly decreased by 44% compared to pre-injury levels (p < 0.05). HHES significantly improved cortical perfusion at 4 h after CCI, approaching baseline values (85 +/- 12%). While increased posttraumatic brain edema was not reduced by HHES at 24 h, cortical contusion volume was significantly decreased in the HHES-treated rats at 7 days after CCI (23.4 +/- 3.5 vs. 39.6 +/- 6.2 mm3; p < 0.05). Intravaneous administration of HHES within 15 min after CCI has a neuroprotective potential, as it significantly attenuated impaired pericontusional perfusion and markedly reduced the extent of induced structural damage.

Effects of hypertonic versus isotonic infusion therapy on regional cerebral blood flow after experimental cardiac arrest cardiopulmonary resuscitation in pigs

OBJECTIVE

To evaluate the effects of hypertonic, isooncotic, and isotonic infusion therapy on cerebral blood flow (CBF) during and after cardiopulmonary resuscitation (CPR) from experimental cardiac arrest (CA).

METHODS

In 32 domestic swine (13-23 kg) open chest CPR was initiated after 8 min of ventricular fibrillation. With the onset of CPR animals randomly received 2 ml/kg per 10 min of either hypertonic saline (HS: 7.2% NaCl), hypertonic-isooncotic HES-saline (HHS: 7.2% NaCl in 6% HES 200,000/0.5), isooncotic HES (6% HES 200,000/0.5), or isotonic (normal) saline (NS: 0.9% NaCl). Haemodynamic variables were monitored continuously, and coloured microspheres were used to measure CBF quantitatively before CA, during CPR, and 20, 90 and 240 min after restoration of spontaneous circulation (ROSC).

RESULTS

In HES/NaCl treated animals, CBF significantly decreased during CPR compared to the prearrest level (P < 0.01, respectively; MANOVA). In contrast, CBF was sustained during CPR in HS/HHS treated animals and significantly higher compared to animals receiving NS (P < 0.05, respectively). During recirculation severe postischaemic hypoperfusion as indicated by a decrease of CBF below the prearrest level, was present only in animals receiving HES and NS.

CONCLUSIONS

Hypertonic solutions (HS/HHS) applied during internal cardiac massage enhanced CBF during CPR and after ROSC.

[Pre-clinical management of shock patients]

The preclinical diagnosis of shock is still based on the patient's history, the physical examination, the injury pattern and a few hemodynamic parameters available in the emergency set-up. The clinical picture is characterised by hypotension and tachycardia, tachypnoe and dyspnoea as well as cerebral impairment. Results from recent clinical trials indicate, that a adapted and specific therapeutic approach for the various shock forms is necessary. In case of traumatic hypovolemic-hemorrhagic shock it is of particular relevance if penetrating trauma and/or uncontrolled bleeding exists. Under these conditions an immediate definite surgical treatment is required ("scoop and run") and a moderate hypotension should be tolerated. ("treat and run"). Fluid substitution and therapy with catecholamines should be used conservatively. In all other forms of shock the treatment approach can and should be more aggressive in order to improve microvascular perfusion as early as possible. Besides adequate fluid resuscitation in a combination of crystalloid and colloid solutions catecholamines and-under specific circumstances-also vasopressin should be used. Of utmost importance in the pre-clinical management of patients in shock is the optimal selection of the centre that the patient is referred to in order to establish the fastest and best possible definite treatment for the patient.

The Effect of Different Volumes of Fluid Resuscitation on Traumatic-Hemorrhagic Shock at High Altitude in the Unacclimated Rat

The effects of different volumes of fluid resuscitation on traumatic hemorrhagic shock in unacclimated rats to high altitude were investigated. Seventy-eight Wistar rats were transported to LaSa, Tibet, 3760 meters above sea level, and traumatic hemorrhagic shock was induced by right-femur fracture plus bleeding to 45 mmHg of mean arterial pressure (MAP) for 1 h under the anesthesia of sodium pentobarbital (40 mg/kg, i.p.). Experiments were conducted in two series. In series I, 36 rats were equally divided into six groups: sham-operated, untreated (traumatic shock without fluid infusion), and with lactated Ringer's resuscitation (LR) of 1.0, 1.5, 2.0 or 3.0 times the shed blood (1, 1.5, 2, 3 vol LR group). MAP, left intraventricular systolic pressure, the maximal change rate of intraventricular pressure rise or decline (+/-dp/dtmax), the maximal physiological velocity of contractile element shortening, and the area of left intraventricular pressure-dp/dt vector loop (Lo) were observed at 30, 60, 90, and 120 min and the blood gases were determined at 30 and 120 min after resuscitation. Meanwhile the survival time was observed after the observation period. In series II, 42 rats were used to observe the effects of different volumes of fluid resuscitation on water content of lung and brain and hematocrit. One and 1.5 vol LR resuscitation significantly lifted MAP, left intraventricular systolic pressure, +dp/dtmax, and Lo, partially improved the blood gases and significantly prolonged the survival time. Although 2 and 3 vol of LR resuscitation caused apparent hemodilution and lung edema, they only partially improved hemodynamic parameters. Meanwhile 2 and 3 vol of LR resuscitation decreased the survival time. These results suggest that 1 and 1.5 vol of LR resuscitation can effectively resuscitate traumatic hemorrhagic shock at high altitude. More than two volumes of LR resuscitation would deteriorate the resuscitation outcome.

Effects of fluid resuscitation on mesenteric microvascular blood flow and lymphatic activity after severe hemorrhagic shock in rats

We investigated the acute microcirculatory effects, including mesenteric lymphatic pumping, of volume replacement with different iso- or hypertonic/oncotic solutions after severe hemorrhage (mean arterial pressure [MAP] approximately 35 mmHg during 30 min) in halothane-anesthetized Wistar rats. Resuscitation was achieved 30 min after induction of shock with one of the following solutions: autologous blood (BL); 0.9% NaCl (IS), 7.5% NaCl (HS); 5% bovine serum albumin (BSA); 0.9% NaCl-6% hydroxyethyl starch (HES), or 7.5% NaCl-HES (HES 7.5). MAP was partially and transiently restored by infusion of IS or HS, whereas in the groups treated with BL, HES, HES 7.5, or BSA, there was a complete restoration of blood pressure in the 30-min period after infusion. Microvascular blood flow (MBF), measured by laser Doppler flowmetry, was reduced by 59% +/- 7% 10 min after bleeding. MBF was also transiently restored after infusion of IS, HS, BL, BSA, or HES. HES 7.5 was the only solution able to induce immediate and sustained (60 min) restoration of preshock levels of MBF. Volume replacement with IS or HES 7.5 resulted respectively in long-lasting or transient lymphatic pumping overload. On the other hand, resuscitation with all other solutions, except BSA, did not restore lymphatic activity to preshock levels. We also observed a significant reduction of the diameter of mesenteric terminal arterioles (15-30 microm) after bleeding, which was reversed temporarily in IS, BL, and HES groups, whereas resuscitation with HES 7.5 solution was able to maintain arterioles dilated until the end of the experimental period. Therefore, it is concluded that the association of hyperoncotic and hyperosmotic solutions, represented here by HES 7.5, induces positive effects with respect to the macro- and microhemodynamics accompanied by restoration and maintenance of the interstitial drainage system, being indicated for maintenance of postresuscitation cardiovascular and microvascular function.

Current controversies in shock and resuscitation

Many controversies and uncertainties surround resuscitation of hemorrhagic shock caused by vascular trauma. Whereas the basic pathophysiology is better understood, much remains to be learned about the many immunologic cascades that lead to problems beyond those of initial fluid resuscitation or operative hemostasis. Fluid therapy is on the verge of significant advances with substitute oxygen carriers, yet surgeons are still beset with questions of how much and what type of initial fluid to provide. Finally, the parameters chosen to guide therapy and the methods used to monitor patients present other interesting issues.

Hypertonic-hyperoncotic solutions decrease cardiac troponin I concentrations in peripheral blood in a porcine ischemia-reperfusion model

In this study we addressed the question of whether the measurement of cardiac Troponin I (cTnI) is able to reflect beneficial effects of hypertonic-hyperoncotic solutions after transient cardiac arrest. Ten pigs were anaesthetized and cardiac arrest was induced by electric fibrillation. After 5 minutes of global ischemia, cardiac arrest was reversed by electric defibrillation. Upon return of spontaneous circulation 5 animals received hypertonic-hyperoncotic solutions (10% Hydroxyethylstarch 200/0.5 and 7.2% NaCl). The other animals received equivalent volumes of physiological saline. We observed that cTnI serum levels of animals treated with hypertonic-hyperoncotic solutions were significantly lower than those treated with saline. We conclude that hypertonic-hyperoncotic solutions may have cardioprotective effects.

Hypertonic saline treatment of severe hyperkalemia in nonnephrectomized dogs

OBJECTIVES

To determine whether a hypertonic saline bolus improves cardiac conduction or plasma potassium levels more than normal saline infusion within 15 minutes of treatment for severe hyperkalemia. Previously with this model, 8.4% sodium chloride (NaCl) and 8.4% sodium bicarbonate (NaHCO(3)) lowered plasma potassium equally effectively.

METHODS

This was a crossover study using ten conditioned dogs (14-20 kg) that received, in random order, each of three intravenous (IV) treatments in separate experiments at least one week apart: 1) 2 mmol/kg of 8.4% NaCl over 5 minutes (bolus); 2) 2 mmol/kg of 0.9% NaCl over one hour (infusion); or 3) no treatment (control). Using isoflurane anesthesia and ventilation (pCO(2) = 35-40 torr), 2 mmol/kg/hr of IV potassium chloride (KCl) was infused until conduction delays (both absent p-waves and >/=20% decrease in ventricular rate in </=5 minutes) were sustained for 15 minutes. The KCl was then decreased to 1 mmol/kg/hr (maintenance) for 2 hours and 45 minutes. Treatment (0 minutes) began after 45 minutes of maintenance KCl.

RESULTS

From 0 to 15 minutes, mean heart rate increased 29.6 (95% CI = 12.2 to 46; p < 0.005) beats/min more with bolus than infusion and 23.4 (95% CI = 2.6 to 43.5; p < 0.03) beats/min more with bolus than control. No clinically or statistically significant difference was seen in heart rate changes from 0 to 30 minutes. Decreases in potassium from 0 to 15 minutes were similar with bolus, infusion, and control.

CONCLUSIONS

In this model, 8.4% NaCl bolus reversed cardiac conduction abnormalities within the first 15 minutes after treatment, more rapidly than did the 0.9% NaCl infusion or control. This reversal occurred despite similar reductions in potassium levels.

Effects of hypertonic saline-dextran solution on regional blood flow and thrombogenicity in PTFE grafts in the vena cava of the rabbit

OBJECTIVES

to study the effects of hypervolaemic haemodilution with hypertonic saline-dextran solution (HSD) on regional blood flow and thrombogenicity of small diameter polytetrafluoroethylene (PTFE) grafts.

DESIGN

blood flow in rabbit aorta, vena cava and femoral, renal and ear arteries was determined in five groups: controls, isovolaemic haemodilution with dextran-70 (10 ml/kg body weight (b.w. )), hypervolaemic haemodilution (10 ml/kg b.w.) with either dextran-70, 7.5% NaCl or a combination of dextran and NaCl (HSD). In a second series PTFE grafts were inserted into the vena cava of rabbits treated with hypervolaemic haemodilution with dextran, hypertonic saline or HSD and examined after two days.

RESULTS

blood flow increased in aorta, vena cava and femoral artery after haemodilution. The increase was transient in animals treated with hypertonic NaCl alone but sustained in the dextran-70 groups. The grafts from animals treated with hypertonic saline alone had a lower thrombus mass and higher blood flow compared to those from rabbits haemodiluted with dextran-70 only, indicating that both dextran and NaCl have antithrombotic effects. Superior results were obtained with HSD solution.

CONCLUSIONS

HSD solution has a strong flow-promoting action in several vascular beds and beneficial effects on the patency of small diameter vessel grafts.