PROBLEMS OF OXYGENATION AND OXYGEN TRANSPORT DURING HAEMORRHAGE

Myocardial Injury Is Associated with the Incidence of Major Adverse Cardiac Events in Patients with Severe Trauma

BACKGROUND

Severe trauma potentially results in end-organ damage such as myocardial injury. Data suggest that myocardial injury is associated with increased mortality in this cohort, but the association with the incidence of in-hospital major adverse cardiac events (MACE) remains undetermined.

METHODS

Retrospective cohort study including adult patients with severe trauma treated at the University Hospital Duesseldorf between January 2016 and December 2019. The main exposure was myocardial injury at presentation. Endpoints were in-hospital incidence of MACE and incidence of acute kidney injury (AKI) within 72 h. Discrimination of hsTnT for MACE and AKI was examined by the receiver operating characteristic curve (ROC) and the area under the curve (AUC). We conducted multivariate logistic regression analysis.

RESULTS

We included 353 patients in our final analysis (72.5% male (256/353), age: 55 ± 21 years). The AUC for hsTnT and MACE was 0.68 [95% confidence interval (CI): 0.59-0.78]. The AUC for hsTnT and AKI was 0.64 [95% (CI): 0.55-0.72]. The adjusted odds ratio (OR) for myocardial injury and MACE was 2.97 [95% (CI): 1.31-6.72], and it was 2.14 [95% (CI): 1.03-4.46] for myocardial injury and AKI.

CONCLUSION

Myocardial injury at presentation in patients with severe trauma is independently associated with the incidence of in-hospital MACE and AKI.

Peaks and valleys: oscillatory cerebral blood flow at high altitude protects cerebral tissue oxygenation

Introduction.Oscillatory patterns in arterial pressure and blood flow (at ∼0.1 Hz) may protect tissue oxygenation during conditions of reduced cerebral perfusion and/or hypoxia. We hypothesized that inducing oscillations in arterial pressure and cerebral blood flow at 0.1 Hz would protect cerebral blood flow and cerebral tissue oxygen saturation during exposure to a combination of simulated hemorrhage and sustained hypobaric hypoxia.Methods.Eight healthy human subjects (4 male, 4 female; 30.1 ± 7.6 year) participated in two experiments at high altitude (White Mountain, California, USA; altitude, 3800 m) following rapid ascent and 5-7 d of acclimatization: (1) static lower body negative pressure (LBNP, control condition) was used to induce central hypovolemia by reducing chamber pressure to -60 mmHg for 10 min(0 Hz), and; (2) oscillatory LBNP where chamber pressure was reduced to -60 mmHg, then oscillated every 5 s between -30 mmHg and -90 mmHg for 10 min(0.1 Hz). Measurements included arterial pressure, internal carotid artery (ICA) blood flow, middle cerebral artery velocity (MCAv), and cerebral tissue oxygen saturation (ScO2).Results.Forced 0.1 Hz oscillations in mean arterial pressure and mean MCAv were accompanied by a protection of ScO2(0.1 Hz: -0.67% ± 1.0%; 0 Hz: -4.07% ± 2.0%;P = 0.01). However, the 0.1 Hz profile did not protect against reductions in ICA blood flow (0.1 Hz: -32.5% ± 4.5%; 0 Hz: -19.9% ± 8.9%;P = 0.24) or mean MCAv (0.1 Hz: -18.5% ± 3.4%; 0 Hz: -15.3% ± 5.4%;P = 0.16).Conclusions.Induced oscillatory arterial pressure and cerebral blood flow led to protection of ScO2during combined simulated hemorrhage and sustained hypoxia. This protection was not associated with the preservation of cerebral blood flow suggesting preservation of ScO2may be due to mechanisms occurring within the microvasculature.

Preoperative Haemoglobin Levels

It is a common practice in many anaesthetic centres throughout the world to require a minimum preoperative haemoglobin level of 10g/100 ml of blood or more, but very few references are quoted by writers on this subject. A search of relevant medical literature has been made in an attempt to establish the origin and significance of the preoperative haemoglobin requirements recommended.

Fluid resuscitation: past, present, and the future

Hemorrhage remains a major cause of preventable death following both civilian and military trauma. The goals of resuscitation in the face of hemorrhagic shock are restoring end-organ perfusion and maintaining tissue oxygenation while attempting definitive control of bleeding. However, if not performed properly, resuscitation can actually exacerbate cellular injury caused by hemorrhagic shock, and the type of fluid used for resuscitation plays an important role in this injury pattern. This article reviews the historical development and scientific underpinnings of modern resuscitation techniques. We summarized data from a number of studies to illustrate the differential effects of commonly used resuscitation fluids, including isotonic crystalloids, natural and artificial colloids, hypertonic and hyperoncotic solutions, and artificial oxygen carriers, on cellular injury and how these relate to clinical practice. The data reveal that a uniformly safe, effective, and practical resuscitation fluid when blood products are unavailable and direct hemorrhage control is delayed has been elusive. Yet, it is logical to prevent this cellular injury through wiser resuscitation strategies than attempting immunomodulation after the damage has already occurred. Thus, we describe how some novel resuscitation strategies aimed at preventing or ameliorating cellular injury may become clinically available in the future.

Hemodynamic effects of combined treatment with oxygen and hypertonic saline in hemorrhagic shock

OBJECTIVE

In hemorrhagic shock, small volume resuscitation with hypertonic saline transiently increases mean arterial blood pressure (MABP) and cardiac output and augments organ perfusion. Inhalation of 100% oxygen after hemorrhage also increases MABP and redistributes blood flow to the splanchnic and renal vascular beds. We evaluated hemodynamic effects of combined resuscitation with hypertonic saline and oxygen in shock induced by controlled bleeding in rats.

DESIGN

Animal study.

SETTING

Research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Animals were assigned to four hemorrhage groups that received posttreatment with a) normal saline; b) normal saline + 100% oxygen; c) hypertonic saline; d) hypertonic saline + oxygen, and a fifth sham-shock group that received hypertonic saline + oxygen.

MEASUREMENTS AND MAIN RESULTS

Bolus infusion of small volume hypertonic saline markedly increased MABP (p < .001), hindquarter vascular resistance (p < .05), and distal aorta blood flow (p < .01). Hypertonic saline transiently increased superior (cranial) mesenteric artery (SMA) blood flow (p < .001) and small bowel perfusion (p < .01). Inhalation of oxygen after normal saline rapidly increased MABP (p < .01) and hindquarter vascular resistance (p < .02) and decreased distal aorta blood flow (p < .02) and perfusion of the gracilis muscle (p < .05). When given after normal saline, oxygen did not change SMA resistance and increased SMA flow (p < .05). The supplementation of oxygen after hypertonic saline did not exert additional effects on vascular resistance and blood flows in the two vascular beds. However, the combined treatment prevented the oxygen-induced decrease in distal aorta blood flow and gracilis muscle perfusion and maintained MABP at slightly higher values and SMA flow at significantly higher values than hypertonic saline alone until the end of the protocol (p < .01). The two hemorrhaged groups treated with oxygen exhibited the lowest final plasma lactate concentrations (p < .05 from normal saline and hypertonic saline groups).

CONCLUSIONS

We suggest that early combined use of hypertonic saline and oxygen exerts a favorable extended profile of hemodynamic effects that amends shortcomings of each treatment alone in hemorrhagic shock.

Metabolic changes after polytrauma: an imperative for early nutritional support

Major trauma induces marked metabolic changes which contribute to the systemic immune suppression in severely injured patients and increase the risk of infection and posttraumatic organ failure. The hypercatabolic state of polytrauma patients must be recognized early and treated by an appropriate nutritional management in order to avoid late complications. Clinical studies in recent years have supported the concept of "immunonutrition" for severely injured patients, which takes into account the supplementation of Ω-3 fatty acids and essential aminoacids, such as glutamine. Yet many aspects of the nutritional strategies for polytrauma patients remain controversial, including the exact timing, caloric and protein amount of nutrition, choice of enteral versus parenteral route, and duration. The present review will provide an outline of the pathophysiological metabolic changes after major trauma that endorse the current basis for early immunonutrition of polytrauma patients.

[Current concepts of polytrauma management: from ATLS to "damage control"]

In recent years, the implementation of standardized protocols for polytrauma management has led to a significant improvement in trauma care as well as to a decrease in post-traumatic morbidity and mortality. As such, the "Advanced Trauma Life Support" (ATLS) protocol of the American College of Surgeons for the acute management of severely injured patients has been established as a gold standard in most European countries since the 1990s. Continuative concepts to the ATLS program include the "Definitive Surgical Trauma Care" (DSTC) algorithm and the concept of "damage control" surgery for polytraumatized patients with immediate life-threatening injuries. These phase-oriented therapeutic strategies appraise the injured patient of the whole extent of the sustained injuries and are in sharp contrast to previous modalities of "early total care" which advocate immediate definitive surgical intervention. The approach of "damage control" surgery takes into account the influence of systemic post-traumatic inflammatory and metabolic reactions of the organism and is aimed at reducing both the primary and the secondary, delayed, mortality in severely injured patients. The present paper provides an overview of the current state of management algorithms for polytrauma patients, with a focus on the standard concepts of ATLS and "damage control".

The effect of replacement fluids and normovolaemic haemodilution on the survival of dorsal skin flaps in rats

The objective of this study is to investigate the effect of normovolaemic haemodilution (anaemia), haemoglobin level and replacement fluids on the survival of local flaps in rats. Fifty male Wistar rats were divided into four study groups and one control group (10 rats for each). In the study groups, 20% or 30% of blood was withdrawn and replaced by either Gelofusine or saline (0.9%). Single 1.5 cm x 3 cm cranially based dorsal random skin flaps consisting of skin and panniculus carnosus were elevated in all rats. No difference was determined between the control and 20% exsanguinated groups regarding flap survival area. There was a statistically significant difference between the flap survival areas of 20% exsanguinated groups and 30% exsanguinated groups. If the blood loss exceeds 30% of total volume and/or haemoglobin (Hb) level is lower than 10.72 g/dL, the risk of flap necrosis increases significantly.

Effects of inspiratory oxygen concentration and ventilation method on a model of hemorrhagic shock in rats

The effect of inspiratory oxygen concentration and the ventilation method on hemorrhagic shock was investigated. Twenty-eight rats were divided into four groups: mechanical ventilation with pure oxygen (M100); mechanical ventilation with air (M21); spontaneous respiration with pure oxygen (S100); and spontaneous respiration with air (S21). Under intravenous pentobarbital anesthesia, hemorrhagic shock (HS) was induced by withdrawal of blood from the femoral artery. Mean arterial blood pressure (MAP) was maintained at 40-50 mmHg for 2 h. After HS, the blood remaining in the reservoir was reinfused. Then survival rate and MAP were monitored for 2 h. Blood samples were withdrawn and vascular reactivity to norepinephrine (NE; 3.0 micrograms/kg) was tested before and after HS. Results were shown by changes in MAP in response to NE. During HS, the survival rate of the S21 group was lower than that of the M100 and S100 groups (p < .05). Before HS, MAPs of M100 and S100 groups were significantly higher than those of M21 and S21 groups (p < .05). In the M100 and M21 groups, MAPs at 2 h after reinfusion were significantly lower than the baseline value (p < .05). Before HS, reactivity to NE of the M21 group was significantly higher than that of the other groups (p < .05). In the M21 group, reactivity to NE after HS was significantly lower than it was before HS (p < .05). Inspiratory oxygen concentration and the ventilation method affect the survival rate and vascular reactivity of the rat hemorrhagic shock model. Selection of the inspiratory oxygen concentration and the ventilation method should be made according to the purpose of the individual experiment.

Divergent effects of oxygen therapy in four models of uncontrolled hemorrhagic shock

Treatment with oxygen exerts beneficial effects and prolongs survival in hemorrhagic shock induced by controlled bleeding. We evaluated the effects of inhalation of 100% oxygen in four models of uncontrolled bleeding in rats: amputation of the tail, laceration of two branches of the ileocolic artery, incision of the spleen, and laceration of the lateral lobe of the liver. After tail amputation, oxygen caused a short and transient increase in mean arterial blood pressure (MABP; P < 0.01), decreased distal aorta (DA) blood flow by 27% (P < 0.01), and induced transient redistribution of blood flow to the superior mesenteric artery (SMA; P < 0.01). Later on, MABP in the oxygen group decreased gradually and was significantly lower than in air controls (P < 0.01). Oxygen therapy increased the mean blood loss by 40% (P < 0.01), increased blood lactate (P < 0.01), and shortened the survival time (P < 0.01). After laceration of two branches of the ileocolic artery, oxygen treatment caused a transient increase in MABP and redistribution of blood flow to the SMA that was followed by a comparable decrease in MABP, increase in vascular resistance, and decreased blood flow in the DA and SMA. In this model, oxygen did not affect bleeding volume, blood lactate, or survival. A similar transient regional hemodynamic effect was found when oxygen was administered after spleen or liver injury; however, in both models, oxygen maintained MABP at significantly higher values (P < 0.05). The results point to differential effects of oxygen in uncontrolled bleeding with benefits in bleeding from small parenchymal vessels and possible detrimental effect in bleeding from large size vessels.

A physiologic basis for red blood cell transfusion decisions

Identification of a universal "transfusion trigger" has eluded surgeons for years. Optimization of cardiopulmonary hemodynamics should precede the decision to transfuse red blood cells. Red blood cell transfusion should be considered when global oxygen delivery falls below a critical point with increasing oxygen extraction and lactate levels. At present, these parameters must be monitored with invasive techniques. This article addresses some aspects of global oxygen delivery physiology that appear to correlate with cardiac function, metabolism, and tissue perfusion.

Minimum oxygen requirements during anaesthesia with the Triservice anaesthetic apparatus. A study of drawover anaesthesia in the young adult

Thirty-six servicemen were anaesthetised using the Triservice anaesthetic apparatus. They were allocated randomly into one of two groups, to breathe spontaneously or to receive artificial ventilation, and into subgroups who were given air alone, or air supplemented with 1 or 4 litres/minute of oxygen. A further 12 subjects were studied subsequently using 0.5 litres/minute of added oxygen. Intra-operative blood gases were compared with those of awake premedicated controls. Artificial ventilation was associated with an unchanged arterial oxygen tension with air alone; in the other subgroups arterial oxygen tension was higher than with spontaneous respiration when related to inspired oxygen fraction (p less than 0.05). Air anaesthesia caused significant hypoxaemia with spontaneous ventilation (p less than 0.05), and 50% of the subjects required assisted ventilation. There was also a significant respiratory acidosis (p less than 0.05). Intermittent positive pressure ventilation is the method of choice for field anaesthesia when oxygen is unavailable. Spontaneous respiration must be supplemented with at least 0.5 litres minute of oxygen.

Might the aphorism "there is no indication in medicine for a pint of blood" lie behind some of the residual morbidity and mortality of surgery?

Reconsideration of, and some uncertainty about, the risks of whole blood transfusion are stimulating renewed debate around and about transfusion policy. This essay -- 1) considers probable risks of retreating in fright from the approach which has significantly reduced the morbidity and mortality of surgical operations over the last 100 years, so that we may balance them against the known and putative risks of transfusion. 2) questions the universality of the aphorism "There is no indication in medicine for a pint of blood" -- because it presumes and implies that everyone can "tolerate"/not be harmed by/minor blood loss, or minor hypovolaemia from any other cause, and leads surgeons and anaesthetists to aim at "minimising" the degree and duration of hypovolaemia during surgery rather than to prevent it entirely. 3) proposes that circulating volume deficiencies, including small ones, are intrinsically intolerable pathological events to be prevented by a "positive" policy aiming at normovolaemia throughout operative procedures by "priming" patients about to undergo major operations with volume expanders before surgery, minimising their intraoperative blood loss, giving non-blood plasma expanders until dilution threatens significant anaemia, and whole-blood transfusion as a last resort when it does. 4) proposes that averting "minor" short-lived circulating volume depletion might avert the residual "minor" morbidity and mortality caused by venous thrombosis, pulmonary embolism, bronchopneumonia, intestinal ileus, postoperative abdominal distension, wound and anastomotic dehiscence, fat embolism, (alone or in various combinations) and give us a greater (insight into and) control over fluid and electrolyte balance.

The Triservice anaesthetic apparatus

The Triservice anaesthetic apparatus is a draw-over using ambient air as the primary carrier gas. Its modules are a self-inflating bag, a vaporiser, a supplementary oxygen regulator and a ventilator; each is described. The outputs of halothane and trichloroethylene were measured with changes of temperature, continuous and intermittent gas flows and with alteration in barometric pressure. The output of oxygen from the Houtonox regulator was measured and the effect of the oxygen supplementation on the inspired oxygen concentration determined. The resistance to airflow of the apparatus was also measured and the effect of extreme cold observed. The merits, limitations and the way in which the equipment may be used are discussed. A carrying case with equipment for 10 anaesthetics is illustrated.

Hemodynamics following normovolemic hemodilution in elderly patients

The hemodynamic effects of acute hemodilution with dextran 70 as dilutional agent were evaluated in a group of elderly patients (mean age 68, range 60-79 years) anesthetized with neurolept analgesia. The isovolemic exchange of 1.1 liter of blood (mean) with a 6% solution of dextran 70 decreased the hematocrit value from 41 to 28%. As cardiac index did not exchange, the oxygen transport capacity was significantly reduced. The main compensating mechanism for this was an increased extraction of oxygen in the tissues and, to a minor extent, a raised arterial oxygen tension. The results of this study suggest that intentional hemodilution should be used with caution in aged patients.

Autologous blood transfusion

Autologous blood transfusion is a procedure in which blood is removed from a donor and returned to his circulation at some later time. Autologous transfusion can be performed in three ways: (1) preoperative blood collection, storage, and retransfusion during surgery; (2) immediate preoperative phlebotomy with subsequent artificial hemodilution and later return of the phlebotomized blood; and (3) intraoperative blood salvage and retransfusion. All three methods of autologous transfusion offer a potentially superior method of blood transfusion which eliminates many of the problems and complications associated with the banking and administration of homologous donor blood.

A hypothesis concerning the aetiology of venous thrombosis

The historical background against which a new hypothesis must be discussed is presented, and the main threads of thinking about thrombosis are isolated so far as they can be. The interplay between such ideas as pus, white thrombus, white blood corpuscles, platelets, fibrin, and red blood cells, is traced: the origins of our concepts of blood circulation, stasis and slow blood flow, and vessel wall damage, are likewise dug up. The new hypothesis rearranges concepts which are not themselves actually or entirely new: instead of postulating that reduced blood flow results in 'silting' of presumably lifeless blood cells, it proposes that slow flow is more likely to injure venous endothelium by metabolic deprivation: and, in place of 'passive' silting, it postulates attachment of white blood cells and platelets to the damaged endothelium by virtue of their phagocytic or reparative function/s. This implies that thrombi are likely to form wherever living blood cells pass through veins whose endothelium is dying or dead from impaired nutrition (or other cause). The death of endothelium may be widespread, as in the agonal state, or, very limited, as in venous valve pockets when stasis is prolonged. The hypothesis is novel in that it seeks to explain thrombogenesis in functional or physiological terms, rather than in terms of purely biochemical pathogenesis.

Intraoperative arterial oxygenation in obese patients

Although obese patients have been shown to represent a particularly high risk group with respect to hypoxemia both pre and postoperatively, no data exist to delineate the intraoperative arterial oxygenation pattern of these patients. Furthermore, no one has studied the effects of a change in operative position or a subdiaphragmatic laparotomy pack on arterial oxygenation (PaO2). Sixty-four adults undergoing jejunoileal bypass for morbid exogenous obesity, with a mean weight of 142.0 +/- 31.4 kg and a mean age of 33.3 +/- 10.4 years, were studied. Twenty-five patients (Group I) were maintained in the supine position throughout the operative procedure, while the remaining 39 patients (Group II) were changed to a 15 degrees head down position 15 minutes after a control blood sample was taken. Four additional markedly obese patients were studied to determine the effect of an abdominal pack of PaO2 values. The following findings were demonstrated: 1) 40% oxygen did not uniformly produce adequate arterial oxygenation for intra-abdominal surgery in otherwise healthy obese patients; 2) placement of a subdiaphragmatic abdominal laparotomy pack without a change in operative position resulted in a consistent fall in PaO2 in each patient to less than 65 mm Hg even though 40% oxygen was being administered; and 3) a change from supine to a 15 degrees head down operative position resulted in a significant (P less than 0.001) reduction in mean PaO2 (73.0 +/- 26.3 mm Hg). Seventy-seven per cent of these patients demonstrated PaO2 values of less than 80 mm Hg on 40% oxygen. Because of these findings, serious consideration should be given to the routine use of the Trendelenberg position intraoperatively in obese patients. However, if one elects this posture, prudence would dictate careful monitoring and maintenance of arterial oxygenation. Certainly, in obese patients, the intraoperative combination of the head down position and a subdiaphragmatic laparotomy pack should be avoided. In addition, since our data were collected in obese but otherwise healthy, young patients free of cardiorespiratory disease, special attention should be directed at the continuous measurement of arterial oxygenation in the older obese patient with either intrinsic dysfunction of vital organs (heart, lung, liver, kidney) or surgical disorders (peritonitis, sepsis).

Cardiovascular changes during laparoscopy. Studies of stroke volume and cardiac output using impedance cardiography

The stroke volume and cardiac output changes in twenty-four patients undergoing laparoscopy were measured using the non-invasive technique of impedance cardiography. There was a moderate fall of stroke volume and cardiac output during intraperitoneal insufflation of carbon dioxide which was directly related to the volume of gas used. The need for caution during laparoscopy particularly in ill patients is emphasised.

Splanchnic oxygen uptake in relation to systemic oxygen uptake during postoperative splanchnic blockade and postoperative fentanyl analgesia

In 34 patients with gallbladder disease, but otherwise healthy, the systemic and splanchnic oxygen uptake were studied in connection with cholecystectomy. Postoperatively, 22 patients were given a posterior splanchnic blockade with 0.5% plain lidocaine, and 12 were given fentanyl intramuscularly in a dose of 3.5 mug/kg b.w. Postoperatively, before the analgesic agent was administered, both the systemic and splanchnic oxygen uptake were increased by 40--50%, the splanchnic fraction of the systemic oxygen uptake being the same as preoperatively. Following administration of fentanyl, as well as after splanchnic blockade, the systemic oxygen uptake decreased almost to the preoperative level. The splanchnic oxygen uptake, however, did not change after fentanyl administration but increased further significantly following splanchnic blockade. The splanchnic fraction of the systemic oxygen uptake increased rapidly after the blockade, while it increased slowly after fentanyl administration.

Circulatory and respiratory adaptation in man to acute withdrawal and reinfusion of blood

In eight healthy men 950 g of blood (12.2 17.6% of the blood volume) was withdrawn and reinfused after about half an hour. Respiration and circulation were studied by analyses of expiratory gas, blood gases and data from right heart catheterization. On hemorrhage oxygen uptake and cardiac output decreased by 10 and 28%, repectively; both varied indirectly with the blood loss. The pressures in the right ventricle, pulmonary and systemic arteries fell without relation to the cardiac output. Mean heart rate did not change significantly, but a moderate positive covariation (P less than 0.05) between heart rate and arterial blood pressure was found during bleeding. This result was confirmed by the relative bradycardia noted in the period prior to reinfusion. On refilling of the bood the oxygen uptake and the pulmonary arterial pressures increased above the initial value. The heart rate varied directly with the arterial pressure also during reinfusion. The observations demonstrate a depression of the metabolism and circulation on moderate hemorrhage. Part of these effects is tentatively referred to a lowered set point of the arterial baroreflexes.

Cerebral blood flow and metabolism during open-heart surgery

Branthwaite, M. A. (1974).Thorax, 29, 633-638. Cerebral blood flow and metabolism during open-heart surgery. Changes in cerebral blood flow and metabolism were investigated in 30 patients during the first five minutes of cardiopulmonary bypass. The ratio of blood flow to oxygen uptake (the cerebral blood flow equivalent or CBFE) rose by 54% and this change could not be attributed to simultaneous variations in arterial carbon dioxide tension, haematocrit or temperature.

A modified thermovelocity technique was used to assess changes in blood flow in the internal jugular vein in 12 of the 30 subjects. The method suffers from a number of serious limitations, but the evidence suggests that there was a reduction in cerebral blood flow at the onset of bypass in more than 50% of the patients studied. The fall was associated with a particularly marked reduction in systemic blood pressure and occurred in spite of high overall flow rates from the oxygenator.

It is argued that the findings indicate considerable depression of cerebral metabolism, which may be due to the decreased oxygen availability consequent upon haemodilution and hypotension and which may contribute to neurological damage in some patients.