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Biomedical subjects

G C Kramer

Publications and source records attributed to G C Kramer.

At least 55 records · Page 3Linked to original sources
PubMed1994

Hypertonic saline dextran prime reduces increased intracranial pressure during cardiopulmonary bypass in pigs.

Children and adults who develop neurologic deficits after cardiac surgery may experience cerebral ischemia during cardiopulmonary bypass. Increased intracranial pressure (ICP) may contribute to cerebral ischemia during bypass. Hypertonic saline dextran (HSD), a hyperosmotic, hyperoncotic resuscitation solution, decreases ICP in trauma resuscitation. We hypothesized that HSD would decrease ICP, reduce brain water, and reduce intravascular fluid requirements during bypass. Twelve swine were divided into two bypass groups: Group 1 (ISO = isotonic) received as prime 1 L of lactated Ringer's solution and 500 mL of 6% hydroxyethyl starch. Group 2 (HSD = hypertonic saline/dextran) received as prime 1 L of lactated Ringer's solution, 500 mL of 6% hydroxyethyl starch, and 1 mL/kg of 24% hypertonic saline/25% dextran. Normothermic bypass was instituted at 100 mL.kg-1.min-1. ICP increased significantly during bypass with ISO prime but not with HSD. Brain water in the cerebrum did not differ between groups but was reduced in the cerebellum to 75.9% +/- 1.4%. We conclude that HSD prevented any significant increase in ICP during normothermic bypass, and substantially improved fluid balance during bypass. In cardiac surgery patients in whom maintaining decreased ICP and reducing isotonic fluid administration is important, HSD may be a useful addition to the bypass prime solution.

Animals↗
PubMed1993

Consequences of misfilling contemporary vaporizers with desflurane.

Desflurane is a volatile anaesthetic that combines low blood gas solubility (blood/gas partition coefficient = 0.42 at 37 degrees C), moderate potency (MAC = 6-7%), and high volatility (vapour pressure = 681 mmHg at 20 degrees C, boiling point = 23.5 degrees C). The volatility and potency of desflurane prevent its safe use in vaporizers of traditional design. We present a mathematical model which demonstrates the potential for desflurane overdose if contemporary vaporizers are misfilled with desflurane. The most hazardous filling error occurs if an enflurane vaporizer is misfilled with desflurane. The calculated desflurane output of a misfilled enflurane vaporizer at a dial setting of 1% and a temperature of 22 degrees C is 57.8%, or 9.6 MAC. For misfilled enflurane, isoflurane, and halothane vaporizers at dial settings equivalent to one MAC at 22 degrees C, the calculated desflurane output is 14.0, 10.2, and 7.8 MAC, respectively. We conclude that the safe delivery of desflurane will require engineering safeguards, additional monitoring, and education of the anesthesia community.

Accident Prevention↗
PubMed1993

Resuscitation of hypovolemia in pigs using near saturated sodium chloride solution in dextran.

A 7.5% sodium chloride/6% Dextran solution (HSD) is effective for restoration of cardiovascular function after hemorrhagic shock. In the present experiments, we tested the usefulness and side effects of a 25% NaCl/24% Dextran solution (SSD), compared to HSD and 0.9% NaCl (NS). After 1 hr of baseline observation, 21 anesthetized pigs were submitted to hemorrhagic shock, maintaining a mean arterial pressure of 45 mmHg for 60 min. Continuous intravenous infusion of one of the solutions was then initiated and the infusion rate adjusted to restore and maintain cardiac output at baseline levels for 2 hr. The NS group required 121 +/- 22 ml/kg to achieve full resuscitation, while the HSD and SSD groups required 6.3 +/- 1.3 and 1.7 +/- 0.2 ml/kg, respectively. We conclude that SSD infusions were exceedingly effective at restoring cardiovascular function in volumes equal to only 10% of bled volume, but were associated with transient hemolysis and peripheral vein inflammation.

Animals↗
PubMed1993

Liver hemodynamics during portal venous endotoxemia in swine.

The acute hemodynamic response of the liver to portal endotoxemia was measured in six isoflurane anesthetized pigs in which volume support was used to maintain normal cardiac output. After baseline monitoring, bacterial endotoxin (LPS) was infused over 1 hr into a mesenteric vein at a rate of 1 microgram.kg-1.hr-1, and monitoring was continued for 1 hr postinfusion. Peak vasoconstriction occurred during LPS infusion in both the hepatic artery (resistance increases 349% of baseline, P < 0.05) and the liver's portal circulation (resistance increases 159% of baseline, P < 0.05). Increased vascular resistance was also detected in lung (increases 433% of baseline) and intestine (increases 130% of baseline) at the midpoint of the LPS infusion. The non-splanchnic circulation, defined for our analysis as all of the peripheral circulation except the portal and hepatic arterial circulation, generally exhibited little change in vascular resistance during LPS infusion. LPS was incompletely cleared by the liver, but secondary clearance by the lung prevented large increases in the LPS concentration of arterial blood. During the first hour postinfusion, the systemic vascular resistance subsequently decreased to near normal in all vascular beds, with the exception of the liver's portal circulation. A sustained and secondary increase in vascular resistance of the liver's portal circulation and portal vein pressure occurred during the first hour after LPS infusion. We conclude that most of the vasoconstriction in the acute response to portal endotoxemia occurs in the liver and lung, organs directly exposed to elevated levels of endotoxins.

Animals↗
PubMed1992

Comparison of intraosseous and intravenous delivery of hypertonic saline/dextran in anesthetized, euvolemic pigs.

STUDY OBJECTIVES: With renewed interest in intraosseous (IO) infusion, the present study examined if sternal IO infusion provided vascular entry of 7.5% NaCl/6% dextran-70 (HSD) as efficiently as IV infusion. DESIGN, SETTING, TYPE OF PARTICIPANTS, INTERVENTIONS: Twelve anesthetized pigs were catheterized for measurement of cardiovascular parameters. Six pigs were given a 4-mL/kg IO infusion of HSD under pressure over two to six minutes; each pig was paired with another that had been given HSD IV over the same time course. Rapid arterial blood sampling was used to evaluate vascular entry of NaCl and dextran with monitoring continued for two hours after infusion. MEASUREMENTS AND MAIN RESULTS: Complete vascular entry of infused sodium and dextran was generally complete within one minute after infusion in all experiments. Increases in mean arterial pressure, cardiac output, and other cardiovascular parameters were indistinguishable between IO and IV infusions. Plasma volume expansion was about 20% above baseline in both groups of pigs. Histologic examination showed minimum pathology to the sternum and no significant pulmonary complications. CONCLUSION: 1O vascular delivery of HSD is a viable alternative in emergency scenarios in which vascular access is compromised.

Analysis of Variance↗
PubMed1992

Effects of hypertonic saline dextran resuscitation on oxygen delivery, oxygen consumption, and lipid peroxidation after burn injury.

We compared the effects of lactated Ringer's (LR) and hypertonic saline dextran (HSD) on postburn cardiovascular function, O2 consumption, lipid peroxidation, and bacterial translocation. Miniature pigs with 40% total body surface area (TBSA), third-degree burns received, 30 minutes postburn, either Parkland resuscitation (LR group, n = 8) or HSD, 10 mL/kg/30 minutes, followed by LR, 4 mL/kg/%burn over the next 23 hours (HSD group, n = 8). The HSD prevented the early decrease in cardiac index (CI); the early increase in the resistance of the systemic, mesenteric, celiac, and renal vascular beds; and the decrease in mesenteric O2 consumption seen after burns when LR alone is used for resuscitation. The HSD also moderated the systemic and mesenteric lipid peroxidation. Bacterial translocation was less in the HSD group (3 of 8 animals) compared with the LR group (5 of 8 animals), but was not statistically different. Hypertonic saline dextran may be beneficial in improving the postburn microcirculation and attenuating postburn oxidant-induced lipid peroxidation in the systemic tissues and the gut.

Animals↗
PubMed1992

Systemic blood flow to sheep lung: comparison of flow probes and microspheres.

Discrepancies exist between experimental measurements of the systemic blood flow to sheep lung by use of microsphere techniques and flow probes on the bronchial artery. In these studies, we simultaneously measured the blood flow through the bronchial artery, using a transit time flow probe, and the systemic blood flow to left lung, using radioactive microspheres. All measurements were made on conscious sheep previously prepared with chronic catheterizations of the left atrium, aorta, and vena cava and a flow probe around the bronchial artery. Inflatable occluder cuffs were placed around the pulmonary and bronchoesophageal arteries. Bronchial artery blood flow in six sheep was 25.3 +/- 5.2 ml/min or 0.4% of the cardiac output. Systemic blood flow to left lung, measured with microspheres, was 54.1 +/- 14.2 ml/min. Calculated systemic blood flow to that portion of sheep lung perfused by the bronchial artery was 127.6 +/- 35.3 ml/min or 1.9% of cardiac output. Occlusion of the bronchoesophageal artery reduced bronchial artery flow to near zero, whereas total systemic blood to the lung was reduced by only 55%. Blood flow to the intraparenchymal cartilaginous airways was reduced 60-90% after occlusion of the bronchoesophageal artery. Sheep, like most mammals, have multiple and complex systemic arterial inputs to the lungs. We conclude that multiple branches of the bronchoesophageal artery provide most but not all of the systemic blood flow to the intraparenchymal cartilaginous airways but that over one-half of the total systemic blood flow to sheep lung comes from sources other than the common bronchial artery.

Animals↗
PubMed1992

Resuscitation of intraoperative hypovolemia: a comparison of normal saline and hyperosmotic/hyperoncotic solutions in swine.

BACKGROUND AND METHODS: We compared a hypertonic saline-dextran solution (7.5% NaCl/6% dextran-70) with 0.9% NaCl (normal saline) for treatment of intraoperative hypovolemia. Fourteen anesthetized pigs (mean weight 36.3 +/- 2.1 kg) underwent thoracotomy, followed by hemorrhage for 1 hr to reduce mean arterial pressure to 45 mm Hg. A continuous infusion of either solution was then initiated and the flow rate was adjusted to restore and maintain aortic blood flow at baseline levels for 2 hrs. RESULTS: Full resuscitation to initial values of aortic blood flow was achieved with both regimens, but the normal saline group required substantially larger volumes and sodium loads to maintain stable hemodynamic values. Normal saline resuscitation produced increases in right ventricular preload (central venous pressure) and afterload (pulmonary arterial pressure and pulmonary vascular resistance), resulting in increased right ventricular work. CONCLUSIONS: Hypertonic saline-dextran solution resuscitation of intraoperative hypovolemia is performed effectively with smaller fluid and sodium loads, and is devoid of the deleterious effects associated with fluid accumulation induced by a conventional isotonic solution regimen.

Animals↗
PubMed1991

Marked increase of plasma hyaluronan after major thermal injury and infusion therapy.

Hyaluronan (HYA) is an important structural element in skin and is presumably participating in regulation of the interstitial fluid volume. HYA is transported via the lymphatics from the tissues to the blood, where its concentration is normally very low. Fluid flux through the interstitium is markedly increased after thermal injury. The present study was performed to determine whether major thermal injury would affect plasma levels of HYA. In halothane-anesthetized sheep subjected to 40% BSA full-thickness scald burns, plasma HYA concentration increased from 116 +/- 19 (mean +/- SEM) to 172 +/- 18 ng/ml within 1 hr after injury (P less than 0.05). After 3 hr of fluid therapy plasma HYA concentration was further elevated to 10 times baseline (1417 +/- 322 ng/ml) (P less than 0.01). To clarify whether this rise represented an increased "washout" of interstitial HYA, attributable either to the burn injury or the subsequent fluid therapy, awake sheep were subjected to overhydration. Following a 3-hr infusion of lactated Ringer's 2.5 liter/hr, plasma HYA concentration increased to 2-3 times baseline. Lung lymph flow and its concentration of HYA increased, leading to an increase in the lymphatic flux of HYA to 10-20 times baseline. In peripheral lymph HYA flux increased 2-3 times baseline. Infusion of lactated Ringer's markedly increased lymphatic removal of HYA. However, plasma concentrations of HYA were 3 times higher after thermal injury than following fluid challenge alone, suggesting that thermal injury per se may also increase input of HYA into the systemic circulation.

Animals↗
PubMed1991

Laser Doppler velocimetry of tracheal blood flow in sheep.

A laser-Doppler velocimetry (LDV) apparatus was adapted to assess sheep airway blood flow. The LDV signal obtained was compared to microsphere determinations of blood flow to tracheal tissues utilizing 15 microns radioactive microspheres injected before and after intubation and anesthesia, during hemorrhagic hypotension, and after reinfusion-resuscitation. During hemorrhagic hypotension, airway wall blood flow decreased to 16% of control by the microsphere method and to 30% by LDV. After reinfusion-resuscitation, airway wall blood flow increased over control values 40% and 33% by the two methods, respectively. Although at low flows LDV values were greater than microsphere determinations, the overall LDV recordings correlated with airway microsphere flow determinations of tracheal wall blood flow (R = 0.85) and tracheal mucosa flow (R = 0.81), but not with tracheal muscularis flow (R = 0.32). With certain but significant limitations, such as calibration in absolute units, stability of position placement, motion artifacts, and the effects of mechanical irritation-induced hyperemia, LDV represents a relatively noninvasive means for qualitatively evaluating changes in the microcirculatory blood flow of airway mucosa.

Animals↗
PubMed1991

Resuscitation of hypovolemic sheep with hypertonic saline/Dextran: the role of Dextran.

We evaluated the role Dextran-70 plays in small volume resuscitation of hemorrhage using hypertonic saline dextran solutions. Sheep were hemorrhaged (1.5 to 2 liters) over 2 hr to an arterial pressure of 50 mm Hg and were then resuscitated with 100 ml of either 7.5% NaCl (HS/0% Dex) alone, 7.5% NaCl/6% Dextran-70 (HS/6% Dex), or 7.5% NaCl/24% Dextran-70 (HS/24% Dex). During hemorrhage cardiac output was reduced to 40-50% of baseline levels. The major effect of the added dextran was a greater initial increase and more sustained normalization of plasma volume and cardiac output. At 15 min post-infusion, plasma volume was expanded 17 +/- 2% with HS/0% Dex; 27 +/- 2% with HS/6% Dex; and 56 +/- 8% with HS/24% Dex. A dose response effect of the added dextran was also apparent in the post-resuscitation increases in arterial pressure and cardiac output. At 3 min post-infusion, both variables improved with all solutions, but baseline levels were reached and exceeded only in the HS/24% Dex. The increased cardiac output correlated significantly with the degree of vascular expansion. Regression and extrapolation of the post-resuscitation data of plasma volume expansion and increased cardiac output to no volume expansion suggests that the hypertonic saline also augments cardiac output by an additional mechanism independent of volume. Our data show that the addition of dextran to hypertonic saline can play an important role in small volume hypertonic resuscitation by improving both the initial cardiovascular response and the sustainment of that response. Higher concentrations of dextran than currently used in hypertonic formulations may make small volume resuscitation more efficacious.

Animals↗
PubMed1991

Effects of a highly concentrated hypertonic saline-dextran volume expander on cardiopulmonary function in anesthetized normovolemic horses.

Conventional fluid resuscitation is unsatisfactory in a small percentage of equine emergency surgical cases because the large volumes of fluids required cannot be given rapidly enough to adequately stabilize the horse. In anesthetized horses, the volume expansion and cardiopulmonary effects of a small volume of highly concentrated hypertonic saline-dextran solution were evaluated as an alternative initial fluid choice. Seven halothane-anesthetized, laterally recumbent, spontaneously ventilating, normovolemic horses were treated with a 25% NaCl-24% dextran 70 solution (HSD) at a dosage of 1.0 ml/kg of body weight, IV, infused over 10 minutes, and the effects were measured for 120 minutes after infusion. Plasma volume expansion was rapid and significant (from 36.6 +/- 4.6 ml/kg to 44.9 +/- 4.8 ml/kg), and remained significantly expanded for the duration of the experiment. Packed cell volume, total blood hemoglobin, and plasma protein concentrations significantly decreased, confirming rapid and sustained volume expansion with hemodilution. Cardiac index and stroke index immediately increased and remained high for the entire study (from 69.6 +/- 15.3 ml/min/kg to 106.6 +/- 28.4 ml/min/kg, and from 1.88 +/- 0.49 ml/beat/kg to 2.50 +/- 0.72 ml/beat/kg, respectively). Systemic vascular resistance significantly decreased immediately after HSD infusion and remained decreased for the duration of the study (from 1.41 +/- 0.45 mm of Hg/ml/min/kg to 0.88 +/- 0.22 mm of Hg/ml/min/kg). Arterial and venous blood oxygen content decreased significantly because of hemodilution, but actual oxygen transport transiently increased at the 10-minute measurement before returning toward baseline.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1991

Acute hypotension caused by rapid hypertonic saline infusion in anesthetized dogs.

Small volumes (4-6 mL/kg) of 7.5% hypertonic saline solution (HTS) are reported to be effective for resuscitation from circulatory shock. When infused rapidly into either hypovolemic or normovolemic subjects, HTS can cause an immediate and severe hypotension before cardiovascular improvement. In the present study, we examined the hypothesis that the early hypotension produced by HTS was mediated by an acute and transient depression of cardiac contractility. left ventricular pressure and wall motions were measured simultaneously in 10 anesthetized dogs for the assessment of cardiac contractility. Infusion of HTS at 3 mL/kg in 1 min significantly decreased mean arterial blood pressure by 49%, from 95 +/- 4 to 51 +/- 5 mm Hg (P less than 0.05, mean +/- SEM) at 45 s after the onset of infusion. This initial decrease in arterial blood pressure was abrupt and transient (106 +/- 9 s). Concomitantly, cardiac output and coronary blood flow increased significantly from 2.8 +/- 1.0 to 3.9 +/- 1.1 L/min and from 23.7 +/- 5.3 to 49.8 +/- 4.7 mL/min, respectively. Although heart rate remained constant, systolic shortenings of left ventricular diameter and wall thickness increased from 5.6% +/- 0.5% to 7.8% +/- 0.5% and from 13.9% +/- 0.6% to 15.1% +/- 1.2%, respectively, indicating an improvement in cardiac contractility. This was confirmed by subsequent analysis of the left ventricular end-systolic pressure-diameter relationship. Systemic and pulmonary vascular resistance decreased by 60% and 27%, respectively. Despite an initial period of hypotension after rapid infusion of HTS, mean arterial blood pressure, cardiac output, and contractility were all significantly increased at 5 min after HTS infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1990

Evaluation of an intraosseous infusion device for the resuscitation of hypovolemic shock.

An intraosseous infusion device designed for the prehospital administration of hypertonic saline-dextran solutions was evaluated by resuscitating hemorrhaged conscious sheep. Eight animals underwent 2 hours of hemorrhagic hypotension (50 mm Hg, bled volume = 43 +/- 7 ml/kg). This was followed by the intraosseous infusion of 200 ml (4-5 ml/kg) of 7.5% NaCl-6% dextran 70 into the bone marrow of the sternum. Results were compared to seven control animals (bled volume = 31 +/- 6 ml/kg) resuscitated through a central venous catheter. Despite the small volumes infused, mean arterial blood pressure and cardiac output were rapidly normalized in both groups by 10 minutes post resuscitation (p less than 0.01). Plasma sodium concentration increased an average of 12 mEq/L and plasma volume was rapidly expanded regardless of route. The metabolic acidosis of hemorrhagic shock was rapidly corrected, pulmonary pressures remained normal, and hypoxemia did not occur after intraosseous resuscitation. The device provided safe and rapid vascular access via the sternal bone marrow space. The use of intraosseous infusion of hypertonic saline dextran solutions via the sternal bone marrow may allow prehospital rescuers to consistently incorporate fluid replacement therapy into 'scoop and run' policies by avoiding the time delays associated with failures in IV access.

Animals↗
PubMed1990

Effectiveness of hypertonic saline-dextran 70 for initial fluid resuscitation of major burns.

Small-volume resuscitation (4 ml/kg) with hypertonic saline-dextran (HSD) has been shown effective in hemorrhagic shock. In the present study the effectiveness of an initial 4 ml/kg bolus infusion of HSD on cardiovascular function and fluid resuscitation requirements after a major burn injury was evaluated in anesthetized sheep following a 40% BSA scald burn. One hour after injury resuscitation was initiated by a rapid intravenous bolus infusion (4 ml/kg) of either hypertonic saline-dextran (7.5% NaCl in 6% dextran 70) (HSD) or the same volume of normal (isotonic) saline (NS). Lactated Ringer's was later infused as needed to maintain cardiac output at 90% of baseline. HSD rapidly and effectively restored cardiac output and mean arterial pressure significantly better than the same volume of NS. Hemodynamic improvement by HSD was short lived, and need for further fluid therapy was only marginally delayed (HSD 38 +/- 8 min, NS 20 +/- 3 min; p = 0.06) (mean +/- SEM). The total requirements for fluid therapy during the first 6 hr postburn were not reduced by the initial HSD bolus (HSD 3,145 +/- 605 ml, NS 2,905 +/- 495 ml; n.s.), nor was skin edema formation reduced. We conclude that in anesthetized sheep HSD resuscitation was only transiently effective in treating burn shock. This may be attributed to the sustained increase in vascular permeability and continued plasma leak following thermal injury.

Animals↗
PubMed1990

Intrapulmonary distribution of bronchial blood flow after moderate smoke inhalation.

The systemic blood flow to the airways of the left lung was determined by the radioactive microsphere technique before and 17 h after smoke inhalation in six conscious sheep (smoke group) and six sheep insufflated with air alone (sham group). Smoke inhalation caused a sixfold increase in systemic blood flow to the lower trachea (baseline 10.6 +/- 1.7 vs. injury 60.9 +/- 16.1 ml.min-1.100 g-1) and an 11- to 14-fold increase to the intrapulmonary central airways (baseline range 9.5 +/- 1.9 to 13.5 +/- 3.7 ml.min-1.100 g-1 vs. injury 104.6 +/- 32.2 to 187.3 +/- 83.6 ml.min-1.100 g-1). There was a trend for this hyperemic response to be greater as airway diameter decreased from the trachea to 2-mm-diam central airways. In airways smaller than 2 mm, the hyperemic response appeared to diminish. The total systemic blood flow to whole lung is predominantly to small peripheral airways and showed no significant increase from its baseline level of 17.5 +/- 3.7 ml.min-1.100 g-1 in the lung homogenate. Occlusion of the bronchoesophageal artery decreased central airway blood flow 60-80% and peripheral airway blood flow 40-60% in both the sham and the smoke groups.

Animals↗
PubMed1989

Effects of sustained lymph drainage on cardiovascular function and thoracic duct lymph in sheep.

We studied the effect of lowering the plasma protein concentration on the cardiovascular function and thoracic duct lymph in awake adult sheep. Hypoproteinemia was induced in seven nonpregnant, splenectomized sheep by drainage of the thoracic duct lymph over a 5-day period. The plasma protein went from a mean of 6.4 +/- 0.2 (SE) to 4.9 +/- 0.2 g/dl on day 5, and the lymph-to-plasma protein concentration ratio decreased from 0.74 +/- 0.01 on day 1 to 0.48 +/- 0.04 on day 5. The percentage composition of the protein fractions in plasma and lymph remained unchanged. Lymph flow was 1.79 +/- 0.37 and 1.28 +/- 0.10 ml/min for days 1 and 5, respectively. Renin concentration in plasma increased 50-fold by day 5. Arterial pressure fell from 102.9 +/- 5.4 to 72.7 +/- 4.4 mmHg by day 5. Mean hematocrit was 28.9 +/- 1.7 at day 1, which was not significantly different than 24.6 +/- 2.9 at day 5 and indicated that the plasma volume did not decrease. Body weight also did not change significantly. There was a decrease in the transcapillary protein escape rate, determined as the thoracic lymph flow rate multiplied the lymph protein concentration, that suggests adaptations in the microcirculation to decrease vascular-to-interstitial protein transfer during hypoproteinemia. Hypoproteinemic animals also demonstrated greater vascular retention of a fluid volume challenge. In conclusion, the sheep adaptations to sustained hypoproteinemia produced by lymph drainage were a significant decrease in arterial pressure, large increases in vascular compliance and renin concentration, and reduced transcapillary escape rate of protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗