U. Kreimeier

Small-volume resuscitation: from experimental evidence to clinical routine. Advantages and disadvantages of hypertonic solutions

Background:  The concept of small‐volume resuscitatioin (SVR) using hypertonic solutions encompasses the rapid infusion of a small dose (4 ml per kg body weight, i.e. approximately 250 ml in an adult patient) of 7.2–7.5% NaCl/colloid solution. Originally, SVR was aimed for initial therapy of severe hypovolemia and shock associated with trauma.

Trauma management incorporating focused assessment with computed tomography in trauma (FACTT) - potential effect on survival.

BackgroundImmediate recognition of life-threatening conditions and injuries is the key to trauma management. To date, the impact of focused assessment with computed tomography in trauma (FACTT) has not been formally assessed. We aimed to find out whether the concept of using FACTT during primary trauma survey has a negative or positive effect on survival.MethodsIn a retrospective, multicentre study, we compared our time management and probability of survival (Ps) in major trauma patients who received FACTT during trauma resuscitation with the trauma registry of the German Trauma Society (DGU). FACTT is defined as whole-body computed tomography (WBCT) during primary trauma survey. We determined the probability of survival according to the Trauma and Injury Severity Score (TRISS), the Revised Injury Severity Classification score (RISC) and the standardized mortality ratio (SMR).ResultsWe analysed 4.817 patients from the DGU database from 2002 until 2004, 160 (3.3%) were from our trauma centre at the Ludwig-Maximilians-University (LMU) and 4.657 (96.7%) from the DGU group. 73.2% were male with a mean age of 42.5 years, a mean ISS of 29.8. 96.2% had suffered from blunt trauma. Time from admission to FAST (focused assessment with sonography for trauma)(4.3 vs. 8.7 min), chest x-ray (8.1 vs. 16.0 min) and whole-body CT (20.7 vs. 36.6 min) was shorter at the LMU compared to the other trauma centres (p < 0.001). SMR calculated by TRISS was 0.74 (CI95% 0.40-1.08) for the LMU (p = 0.24) and 0.92 (CI95% 0.84-1.01) for the DGU group (p = 0.10). RISC methodology revealed a SMR of 0.69 (95%CI 0.47-0.92) for the LMU (p = 0.043) and 1.00 (95%CI 0.94-1.06) for the DGU group (p = 0.88).ConclusionTrauma management incorporating FACTT enhances a rapid response to life-threatening problems and enables a comprehensive assessment of the severity of each relevant injury. Due to its speed and accuracy, FACTT during primary trauma survey supports rapid decision-making and may increase survival.

Permissive Hypotension beim schweren Trauma

ZusammenfassungBeim polytraumatisierten Patienten steht die hämodynamische Instabilität im Vordergrund, die in den meisten Fällen Folge der Verletzungen und des begleitenden ausgedehnten Blutverlusts ist. Bei Patienten nach schwerem Trauma und Schock ist die Steigerung des Intravasalvolumens zwecks Erzielung einer Normotension mit dem Risiko eines erhöhten Blutverlustes und damit möglicherweise mit einem negativen Einfluss auf die Überlebensrate verbunden. In Ermangelung kontrollierter klinischer Studien zu diesem Thema legen bislang v. a. die Ergebnisse tierexperimenteller Untersuchungen einen positiven Effekt auf die Überlebensrate und das neurologische Outcome mittels “hypotensive resuscitation” nahe. Bei den Konzepten zur Verminderung des Blutverlustes unter Berücksichtigung einer systemischen Hypotension ist zu unterscheiden zwischen “deliberate hypotension” (Synonym: “kontrollierte Hypotension”, die intraoperativ angewandt wird und Normovolämie und stabile Kreislaufverhältnisse voraussetzt), “delayed resuscitation” (wobei das hypotensive Intervall bewusst bis zur definitiven operativen Versorgung verlängert wird) und “permissiver Hypotension” (Synonym: “hypotensive resuscitation”, die alle therapeutischen Maßnahmen einschließlich der Volumentherapie beinhaltet, die zur Erhöhung des systemischen Drucks führen, ohne allerdings normotensive Werte zu erreichen). In dieser Übersicht wird das Konzept der permissiven Hypotension auf der Grundlage der infolge Hypovolämie und niedrigem Perfusionsdruck eingetretenen Veränderungen von Makro- und Mikrozirkulation erläutert. Mögliche Indikationen und Limitierungen bei der Versorgung von Traumapatienten werden diskutiert.SummaryHemodynamic instability in the polytraumatized patient is a predominant feature and most commonly secondary to blood loss accompanying injury. In these patients restoration of intravascular volume attempting to achieve normal systemic pressure faces the risk of increasing blood loss and thereby potentially affecting mortality. Due to the lack of controlled clinical trials in this field, the growing evidence that “hypotensive resuscitation” results in improved long-term survival and improved neurologic outcome, mainly stems from experimental studies in animals. In patient care, several concepts exist for the reduction of blood loss in conjunction with systemic hypotension: these involve “deliberate hypotension” (synonym “controlled hypotension”, used intraoperatively under conditions of normovolemia and stable hemodynamics), “delayed resuscitation” (where the hypotensive period is intentionally prolonged until operative intervention), and “permissive hypotension” (synonym “hypotensive resuscitation”, where all kinds of therapy are commenced including fluid therapy, thereby increasing systemic pressure without, however, reaching normotension). In this review the concept of “permissive hypotension” is delineated on the basis of macro- and microcirculatory changes secondary to hypovolemia and low driving pressure, and potential indications as well as limitations for the care of the traumatized patient are discussed.

Pathophysiology of fluid imbalance

Fluid imbalance can arise due to hypovolemia, normovolemia with maldistribution of fluid, and hypervolemia. Trauma is among the most frequent causes of hypovolemia, with its often profuse attendant blood loss. Another common cause is dehydration, which primarily entails loss of plasma rather than whole blood. The consequences of hypovolemia include reduction in circulating blood volume, lower venous return and, in profound cases, arterial hypotension. Myocardial failure may result from increased myocardial oxygen demand in conjunction with reduced tissue perfusion. Finally, anerobic metabolism due to reduced perfusion may produce acidosis and, together with myocardial dysfunction, precipitate multi-organ failure. The splanchnic organs are particularly susceptible to the deleterious effects of hypotension and hypovolemic shock, and these effects, depending upon their duration and severity, may be irreversible despite restoration of normovolemia by fluid administration. Patient monitoring in the intensive care unit typically relies upon central venous pressure devices, whereas the primary focus in the operating theater is blood volume deficit estimated from suction devices. However, estimates of intraoperative blood loss can be inaccurate, potentially leading to inappropriate fluid management. Normovolemia with maldistribution of fluid can be encountered in shock-specific microcirculatory disorders secondary to hypovolemia, as well as pain and stress. Consequent vasoconstriction and reduced tissue driving pressure, as well as leukocyte and platelet adhesion, and liberation of humoral and cellular mediators, may impair or abolish blood flow in certain areas. The localized perfusion deficit may contribute to multi-organ failure. Choice of resuscitation fluid may be important in this context, since some evidence suggests that at least certain colloids might be helpful in diminishing post-ischemic microvascular leukocyte adherence. Excessive volume administration may lead to fluid overload and associated impairment of pulmonary function. However, entry of fluid into the lungs may also be facilitated by increased vascular permeability in certain pathologic conditions, especially sepsis and endotoxemia, even in the absence of substantially rising hydrostatic pressure. Another condition associated with elevated vascular permeability is systemic capillary leak syndrome. The chief goal of fluid management, based upon current understanding of the pathophysiology of fluid imbalance, should be to ensure adequate oxygen delivery by optimizing blood oxygenation, perfusion pressure, and circulating volume.

Microvascular changes during anesthesia: sevoflurane compared with propofol

Background: We have developed a non‐invasive computer‐assisted venous congestion plethysmograph to measure the microvascular parameters in the lower limbs. This enables the assessment of microvascular changes following the induction of standardized anesthesia with either sevoflurane or propofol.

Veränderungen des Blutvolumens während akuter normovolämer Hämodilution mit 5% Albumin oder 6% Hydroxyäthylstärke und intraoperativer Retransfusion

ZusammenfassungFragestellung. Welche Auswirkung hat die akute präoperative normovoläme Hämodilution (ANH) auf das Blutvolumen, den intravasalen Kolloidbestand und den Verlust an Erythrozyten in der perioperativen Phase? Methodik. Bei 20 Patientinnen mit Zervixkarzinom wurde vor Wertheim-Meigs-Operation unter Verwendung von 5%igem Albumin (Albumin-Gruppe; n=10) oder 6%iger Hydroxyäthylstärke (HES; HES-Gruppe; n=10) eine ANH bis zu einem Hämatokrit von 22% durchgeführt. Ab einem intraoperativen Hämatokrit von 18% fand die Retransfusion des Hämodilutionsbluts statt. Gemessen wurden vor und nach ANH, vor Retransfusion und am OP-Ende das Plasmavolumen (Farbstoffverdünnungsmethode mit Indozyaningrün), der Hämatokrit und die Gesamteiweißkonzentration. Das Erythrozytenvolumen (Markierung von Erythrozyten mit Fluoreszein) bestimmten wir vor und nach ANH sowie am OP-Ende. In der HES-Gruppe wurden die HES-Konzentrationen im Plasma und Urin gemessen. Ergebnisse. Nach einem Blutentzug von rund 1500 ml und einer 15% höheren Kolloidinfusion konnte in beiden Gruppen das Blutvolumen während ANH aufrechterhalten werden. Bei einem Blutverlust von rund 1800 ml wurden in beiden Gruppen etwa 150 ml Erythrozyten durch die Hämodilution eingespart. Schlussfolgerungen. Die Double-label-Messungen des Blutvolumens zeigten, dass bei den verwendeten Kolloiden ein 15% höheres Infusionsvolumen in Relation zum Blutentzug Isovolämie nach ANH gewährleistete.AbstractQuestion. What is the impact of acute preoperative normovolemic hemodilution (ANH) on blood volume, intravascular colloid, and loss of red cells in the perioperative period? Methods. In 20 patients undergoing radical hysterectomy, preoperative ANH was performed to a hematocrit of 22% using 5% albumin (albumin group; n=10) or 6% hydroxyethylstarch solution (HES group; n=10). Intraoperative retransfusion of ANH blood was started at a hematocrit of 18%. Plasma volume (indocyanine green-dilution technique), hematocrit, and plasma protein concentration were measured before and after ANH, before retransfusion, and postoperatively. Red cell volume (labelling erythrocytes with fluorescein) was determined before and after ANH and postoperatively. In the HES group hydroxyethylstarch concentrations were measured in plasma and urine. Results. After removal of about 1,500 ml of blood and replacement with 15% more colloid solution, the blood volume was maintained in both groups after ANH. After a mean blood loss of about 1,800 ml, an average of 150 ml of red cells were saved due to ANH in both groups. Conclusions. Double label measurements of blood volume demonstrated that with the colloids used a surplus of 15% of colloid infusion in relation to blood removal was necessary to generate isovolemia after ANH.

Neue Strategien in der Volumenersatztherapie beim Polytrauma

ZusammenfassungBeim polytraumatisierten Patienten steht die hämodynamische Instabilität im Vordergrund, die in den meisten Fällen Folge der Verletzungen und des begleitenden ausgedehnten Blutverlusts ist.Bei Patienten nach schwerem Trauma und Schock ist die Steigerung des Intravasalvolumens zwecks Erzielung einer Normotension mit dem Risiko eines erhöhten Blutverlusts und damit möglicherweise mit einem negativen Einfluss auf die Überlebensrate verbunden.In dieser Übersicht wird detailliert auf eines der zentralen Themen in der präklinischen Versorgung des Traumapatienten eingegangen.Dabei werden unterschiedliche Strategien wie eine forcierte vs.eine moderate Volumenersatztherapie ebenso dargestellt wie die Frage, welche Infusionslösungen am besten den Erfordernissen zur Wiederherstellung und Normalisierung der Makrohämodynamik und der Therapie der durch Schock induzierten Mikrozirkulationsstörung entsprechen.AbstractHemodynamic instability in polytraumatized patients is a predominant feature and most commonly secondary to blood loss accompanying injury. In these patients restoration of intravascular volume attempting to achieve normal systemic pressure faces the risk of increasing blood loss and thereby potentially affecting mortality.This review addresses one of todays key topics in preclinial trauma care, i.e.vigorous vs.moderate volume substitution therapy, and which kind of solutions seem to correspond best the needs of resuscitation of macrohemodynamics and shockinduced microcirculatory disturbances in particular.

Hypertonic fluid resuscitation from subarachnoid hemorrhage in rats.

OBJECTIVE:Increased intracranial pressure (ICP) and decreased cerebral blood flow leading to global cerebral ischemia are the primary causes of death after severe subarachnoid hemorrhage (SAH). Hypertonic saline has been demonstrated to exert neuroprotective properties after traumatic brain injury by osmotic mobilization of parenchymal water and improvement of microcirculation. We used a rat model to investigate the effects of hypertonic fluid resuscitation after SAH on ICP, cerebral blood flow, body weight, neurological recovery, and morphological damage. METHODS:Sixty rats were subjected to SAH induced by an endovascular filament. ICP and local cerebral blood flow were recorded continuously. Animals were assigned to three groups: 1) NaCl 0.9%; 2) NaCl 7.5% (4 ml/kg); and 3) NaCl 7.5% plus 6% dextran 70 (4 ml/kg) given 30 minutes after SAH. Body weight and neurological deficits were assessed daily. Morphological damage was evaluated on Day 7. RESULTS:SAH resulted in an immediate increase of ICP to approximately 60 mm Hg initially, and then to approximately 30 mm Hg for the next 90 minutes. Although NaCl 7.5% alone and in combination with dextran led to an immediate, significant, and lasting decrease of ICP to 15 to 20 mm Hg, only the combined therapy significantly increased body weight and improved neurological recovery. Furthermore, the group that received combined therapy exhibited significantly more surviving neurons in hippocampus, cortex, caudoputamen, and cerebellum. Mortality was reduced non-significantly, from approximately 65% in groups I and II to 35% in Group III. CONCLUSION:Treatment with NaCl 7.5% plus 6% dextran 70 is significantly effective for reducing the initial harmful sequelae of SAH. The regimen resulted in lowered ICP, improved neurological recovery, and less morphological damage after SAH in the rat.

Hyperosmotic‐hyperoncotic solutions during abdominal aortic aneurysm (AAA) resection

A largely positive perioperative fluid balance during both elective and emergency abdominal aortic aneurysm repair (AAA) may put patients at risk of developing left ventricular failure and may thus contribute to morbidity. In the present paper we report on a prospective study using hyperosmotic‐hyperoncotic solutions (HHS) infused during clamping of the aorta, for the prevention of declamping shock, and the associated reduction in perioperative fluid requirements. The major aim of this paper was to determine the efficacy of an HHS infusion when given over 20 minutes and to detect possible adverse effects of HHS.

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

ZusammenfassungDie Bolusinfusion einer hyperosmolaren Kochsalzlösung (4 ml/kg, 7,2–7,5 % NaCl) führt im hypovolämischen Schock zur raschen Normalisierung der zentralen Hämodynamik und zur Restitution der Organperfusion (Small-volume Resuscitation). Nach Ischämie ist die Wiederherstellung der Perfusion in der mikrovaskulären Strombahn vorrangig. Hyperosmolare Lösungen verbessern die Mikrozirkulation durch Reduktion der Endothelzellschwellung und Verminderung der Leukozytenadhäsion am Endothel. Die Wirkmechanismen und die Effizienz hyperosmolarer Lösungen sind durch experimentelle Untersuchungen gut belegt. Hingegen konnte bislang keine der präklinischen Studien die Überlegenheit hyperosmolarer Lösungen hinsichtlich der Überlebensrate sichern. Eine Metaanalyse von 9 präklinisch durchgeführten Studien ergab nach Small-volume Resuscitation gegenüber einer Standard-Primärtherapie mit Ringerlaktat allerdings eine signifikante Reduktion der Letalität (−5,1 %). Vielversprechende neue Indikationsgebiete für hyperosmolare Kochsalzlösungen stellen der Einsatz in der Kardio- und Gefäßchirurgie, bei Brandverletzten, bei Patienten mit Sepsis sowie die gezielte Therapie des post-ischämischen Reperfusionsschadens dar. Die Kombination hyperosmolarer Lösungen mit künstlichen Sauerstoffträgern ist zur Zeit in experimenteller Erprobung.AbstractThe concept of small-volume resuscitation, the rapid infusion of a small volume (4 ml/kg BW) of hyperosmolar 7.2–7.5 % saline solution for the initial therapy of severe hypovolemia and shock was advocated more than a decade ago. Numerous publications have established that hyperosmolar saline solution can restore arterial blood pressure, cardiac index and oxygen delivery as well as organ perfusion to pre-shock values. Most prehospital studies failed to yield conclusive results with respect to a reduction in overall mortality. A meta-analysis of preclinical studies from North and South America, however, has indicated an increase in survival rate by 5.1 % following small-volume resuscitation when compared to standard of care. Moreover, small-volume resuscitation appears to be of specific impact in patients suffering from head injuries with increased ICP and in severest trauma requiring immediate surgical intervention.Results from clinical trials in Austria, Germany and France have demonstrated positive effects of hyperosmolar saline solutions when used for fluid loading or fluid substitution in cardiac bypass and in aortic aneurysm surgery, respectively. A less positive perioperative fluid balance, a better hemodynamic stability and improved pulmonary function were reported. In septic patients oxygen consumption could significantly be augmented.The most important mechanism of action of small-volume resuscitation is the mobilisation of endogenous fluid primarily from oedematous endothelial cells, by which the rectification of shock-narrowed capillaries and the restoration of nutritional blood, flow is efficiently promoted. Moreover, after ischemia reperfusion a reduction in sticking and rolling leukocytes have been found following hyperosmolar saline infusion. Both may be of paramount importance in the long-term preservation of organ function following hypovolemic shock. An increased myocardial contractility in addition to the fluid loading effects of hyperosmolar saline solutions has been suggested as a mechanism of action. This, however, could not be confirmed by pre-load independent measures of myocardial contractility. Some concerns have been raised regarding the use of hyperosmolar saline solutions in patients with a reduced cardiac reserve. A slower speed of infusion and adequate monitoring is recommended for high risk patients.Recently, hyperosmolar saline solutions in combination with artificial oxygen carriers have been proposed to increase tissue oxygen delivery through enhanced O2 content. This interesting perspective, however, requires further studies to confirm the potential indications for such solutions.Many hyperosmolar saline colloid solutions have been investigated in the past years, from which a 7,2–7,5% sodium chloride in combination with either 6–10 % dextran 60/70 or 6–10% hydroxyethyl starch 200,000 appear to yield the best benefit-risk ratio. This has led to the registration of the solutions in South America, Austria, the Czech Republic, and is soon awaited for North America.