Hemodynamic effects of high dose pentobarbital: studies in elective neurosurgical patients

High dose barbiturate therapy has been used clinically for about 10 years. However, the hemodynamic consequences of such therapy have not been well defined in humans. We therefore examined the effects of a brief (30-minute), high dose (0.6 mg/kg/minute or 18 mg/kg total) infusion of pentobarbital in nine otherwise healthy patients (aged 20 to 30) scheduled to undergo operation for the removal of large or deeply seated arteriovenous malformations. Monitored variables included intravascular pressures, cardiac output, arterial and mixed venous blood gases and hematocrit, and the electroencephalogram (EEG). After a brief rest period and the collection of control data, pentobarbital infusion was begun, muscle relaxants were given, and normocarbia was maintained by mask ventilation. Because our primary intent was to examine the effects of the drug on the heart and arterial circulation, lactated Ringer's solution was infused continuously to keep pulmonary capillary wedge pressure (PCWP) at control values in an attempt to keep constant the ventricular "preload" (although PCWP is only an approximation of the true preload). Drug infusion resulted in progressive EEG suppression ending in a pattern of deep burst suppression (1 to 3 bursts/minute) at t = 30 minutes, with measured plasma pentobarbital concentrations (in four patients) of 34 +/- 4 micrograms/ml (mean +/- SD). There were no changes in PaO2, PaCO2, or pH, nor were there any changes in PCWP. The cardiac index did not change.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of mannitol on blood volume and central hemodynamics in patients undergoing cerebral aneurysm surgery

The effects on hemodynamics and blood volume of 500 ml of 20% mannitol administered intravenously in 15 min at the beginning of cerebral aneurysm surgery have been studied in 10 patients. Measurements were made before the infusion of mannitol (control) and at 15-min intervals for 1 hr. Control measurements showed normal hemodynamic data, while blood volume was lower than normal (P less than 0.001). Immediately after the mannitol infusion cardiac index (25%; P less than 0.01), pulmonary capillary wedge pressure (48%; P less than 0.001), and blood volume (43%; P less than 0.001) increased. Thirty minutes after the mannitol infusion, blood volume had returned to control levels, while the cardiac index and pulmonary capillary wedge pressure decreased 21% (P less than 0.01 and P less than 0.05, respectively) below control levels. Forty-five minutes after the mannitol infusion, serum osmolality and urine volume remained high. Our data confirm the presence of hypovolemia in patients with subarachnoid hemorrhage and a transient increase in blood volume associated with the infusion of mannitol. The data emphasize, however, that the hemodynamic response is biphasic, with an initial increase in pulmonary capillary wedge pressure and cardiac index, followed by a hypokinetic circulatory pattern with pulmonary capillary wedge pressure and cardiac index below control levels. The hypokinetic state occurred in spite of return of blood volume to control levels, suggesting that redistribution of blood from central to peripheral circulatory compartments had occurred.     

Haemodynamic measurements during controlled hypotension by nitroglycerin (author's transl)

In nine patients undergoing neurosurgical operation for cerebral aneuryms haemodynamic measurements were made before, during and after continuous intravenous administration of Nitroglycerin at a mean dose of 6.5 micrograms/kg . min. Within 15 min of the start of the infusion mean arterial pressure fell from 94.2 +/- 10.5 to 73.4 +/- 11.1 mm Hg. A further decrease of mean arterial pressure even by a substantial raising of the Nitroglycerin dose was not possible. 15 min after the discontinuation of Nitroglycerin administration mean arterial pressure rose to the preinfusion level. The decrease of stroke volume index from 40.8 +/- 9.9 to 31.0 +/- 7.3 ml/m2 was partially compensated by an increase of heart rate from 65.9 +/- 9.6 to 77.7 +/- 19.4 beats/min. Consequently cardiac index fell only slightly from 2.9 +/- 0.6 to 2.5 +/- 0.5 ml/min . m2. The right atrial pressure decreased to 3.3 +/- 2.9 mm Hg, the mean pulmonary arterial pressure to 6.3 +/- 1.9 mm Hg and the pulmonary capillary wedge pressure to 2.3 +/- 2.1 mm Hg. The significant fall of total peripheral resistance to 983 +/- 194 dyn x s/cm5 (p less than 0.05) and the decrease of left ventricular stroke work index to 34.7 +/- 11.5 g . m/m2 contributed to reduce myocardial oxygen consumption. The authors conclude that, because of its effect on blood pressure, it reversibility of action and its absence of adverse side effects Nitroglycerin is a valuable agent for controlled hypotension.     

Comparison of enoximone versus tobutamine in the treatment of low cardiac output after cardiac surgery

Enoximone, a new cardiotonic agent not related to glycosides or catecholamines, has been suggested for treatment of low cardiac output syndromes occurring after cardiopulmonary bypass (CPB). The aim of the present study was to compare enoximone with dobutamine in the management of such cases. Twenty consecutive patients who had undergone cardiac surgery with CPB and who had a cardiac index (CI) less than 2.5 l.min-1.m-2, pulmonary capillary wedge pressure greater than 12 mmHg, and no renal failure, were randomly assigned to receive either enoximone (group E, n = 10) or dobutamine (group D, n = 10). The following parameters were monitored at baseline, 15, 30, 60, 90 min, 2, 6, 10 and 14 h: arterial, central venous, pulmonary arterial and capillary wedge pressures (PCWP), cardiac index (CI), stroke volume index (SVI), stroke work index (SWI), systemic (SVR) and pulmonary vascular resistances, as well as heart rate-pressure product (HRPP). Patients in group E were given a bolus of 0.5-1 mg.kg-1 enoximone over a 20 min period, followed by a continuous infusion of 2-20 micrograms.kg-1.min-1, depending on clinical response. In group D, patients were given 2.5 to 15 micrograms.kg-1.min-1 dobutamine according to clinical response. No other inotropic drug was used during the study period. The aim was to obtain an increase in CI greater than or equal to 30% at the end of the first hour of treatment. Excessive systemic hypotension with low SVR was treated with volume loading.(ABSTRACT TRUNCATED AT 250 WORDS)     

Thoracic epidural anesthesia and central hemodynamics in patients with unstable angina pectoris

The effects of high thoracic epidural anesthesia (TEA) on central hemodynamics as measured by pulmonary arterial catheterization were studied in nine patients with severe coronary artery disease and unstable angina pectoris. The patients were also treated with a combination of beta-blockers, calcium antagonists, and nitrates, as well as salicylates, low-dose heparin, and nitroglycerin infusion for greater than 24 hr. Management of pain with high TEA was started with the bolus epidural injection of 4.3 +/- 0.2 mL bupivacaine (5 mg/mL), which induced a sympathetic blockade from Th. During ischemic chest pain, pulmonary artery and pulmonary capillary wedge pressures were significantly increased. TEA, while relieving the chest pain, significantly decreased systolic arterial blood pressure, heart rate, and pulmonary artery and pulmonary capillary wedge pressures, without any significant changes in coronary perfusion pressure, cardiac output, stroke volume, and systemic or pulmonary vascular resistances. In some patients, ST-segment depression was less pronounced during TEA. Thus, during ischemic chest pain, TEA has beneficial effects on the major determinants of myocardial oxygen consumption, without jeopardizing coronary perfusion pressure. TEA may therefore favorably alter the oxygen supply/demand ratio within ischemic myocardial areas.     

Hemodynamic effects of intravenous nitroglycerin: importance of the delivery system

Twenty patients about to undergo elective coronary artery bypass grafting entered a randomized double-blind trial comparing the hemodynamic effects of intravenous nitroglycerin (IV NTG) (0.5 micrograms/kg/min) (n = 9) versus placebo (n = 11). After a 20-min infusion period mean arterial pressure, mean pulmonary arterial pressure, pulmonary capillary wedge pressure, central venous pressure, stroke index, and left ventricular stroke work index were significantly decreased by NTG. Cardiac index was unchanged despite a marked reduction of filling pressures, indicating improved ventricular function. The endocardial viability ratio (DPTI/SPTI) was improved by NTG, suggesting a favorable alteration of myocardial oxygen balance. Three additional patients received a larger dose of NTG, (0.1 micrograms/kg/min). The hemodynamic effects were similar to, but more profound than, those noted at 0.5 micrograms/kg/min. The effects of IV NTG described here are compatible with a predominant venodilator effect of NTG and occurred at a dose previously reported to cause little or no hemodynamic change in a similar group of patients. We attribute the apparent increased potency of IV/NTG observed in our study to the use of an infusion system that does not absorb NTG. Previous investigators have used infusion systems containing polyvinyl chloride (PVC) plastic, a substance that avidly adsorbs NTG. The resultant decrease in the administered dose of NTG renders dose-response data invalid when PVC-containing systems are used to deliver NTG.     

The effect of increasing age on thiopental disposition and anesthetic requirement

The dose of thiopental required to induce anesthesia in adults decreases with age. The pharmacokinetic and pharmacodynamic properties of thiopental were studied in two groups of surgical patients to determine the mechanism of this decrease. In one group (29 patients 19-88 yr of age), thiopental was infused at a rate of 75-150 mg/min until the electroencephalogram (EEG) demonstrated early burst suppression (phase III). Arterial blood samples were obtained frequently during and after the infusion to measure serum thiopental concentrations, and power spectral analysis was used to calculate the spectral edge (Hz), defined as the frequency below which 95% of the EEG power is located. Pharmacodynamic modeling was used to relate the serum thiopental concentrations to the spectral edge in order to estimate the individual patient's brain sensitivity to thiopental. In a second group (28 patients 24-88 yr of age), pharmacokinetics were determined after a bolus or rapid infusion of thiopental. Arterial blood samples were obtained frequently to characterize the initial distribution phases, sampling continued for 24-48 h to characterize elimination processes. The dose of thiopental required to achieve early burst suppression on the electroencephalogram (EEG) decreased linearly and significantly with age. Pharmacodynamic modeling also demonstrated that brain sensitivity to thiopental does not change with age. The age-related decrease of the thiopental dose requirement is due to a change in the initial distribution of the drug. That is, the initial distribution volume (central compartment, or V1) of thiopental decreases exponentially with age. This smaller initial distribution volume in the elderly results in higher serum levels after a given dose of thiopental.     

Effect of furosemide on fully established low pressure pulmonary edema

It has been shown that furosemide, via nondiuretic vascular effects, reduces pulmonary shunt and lung water during the development of oleic acid permeability edema. We studied this effect in a fully established stable model of oleic acid permeability edema. Sixteen anesthetized mongrel dogs, mechanically ventilated with a FIO2 of 0.5, were studied 24 hr after induction of pulmonary capillary leak by intravenous oleic acid (0.06 cc/kg). After stabilization of pulmonary capillary wedge pressure (PCWP) in the range of 0.5-3 mm Hg, bilateral ureteral ligation was performed. Furosemide (2 mg/kg) was then administered intravenously to eight dogs (treated group). An equivalent volume of saline was given to eight control dogs (control group). Pulmonary artery (PAP) and capillary wedge pressures (PCWP), thermodilution cardiac output (Qt), thermal dye lung water (LW), venous admixture (Qva/Qt), arterial and mixed venous blood gases (PaO2, MVO2) were then measured at hourly intervals for 4 hr. During this period of time, central hemodynamics (PCWP, PAP, Qt) remained stable in both groups. Indices of gas exchange and edema formation (Qva/Qt, LW, PaO2) did not change significantly in either control or treated animals. We conclude that furosemide, previously shown to reduce pulmonary shunt and lung water in the early phase of oleic acid permeability edema, does not have any effect once the pulmonary injury is well-established.     

A modified formula of GIK (glucose-insulin-potassium) therapy for treatment of extensive burn injury in dogs

The effectiveness of a modified glucose-insulin-potassium (GIK) formula, which was derived from the results of a previous study (the maximal glucose disposal rate of 400 mg/M2/min required an insulin infusion rate at 1,200 mU/M2/min and KCl supplement rate at 0.08 mEq/M2/min), was evaluated in the treatment of extensive acute burn injury (EABI) in dogs. Under anesthesia initially with intravenous sodium pentobarbital 35 mg/kg followed by a maintenance dose of 5 mg/kg/hr, a third-degree burn of about 50% of the total body surface was created by acetylene torch over the ventral wall of the chest and abdomen. Cardiovascular parameters including heart rate, mean arterial blood pressure, pulmonary wedge pressure, cardiac index, and cardiac contractility (dP/dt of left ventricular pressure), as well as blood chemical data of pH value and K+ concentration were monitored. The present GIK therapy in EABI dogs effectively prevented a decrease in cardiac function, markedly enhanced cardiac function, steadily prolonged cardiac enhancement, and safely avoided hypoglycemic attack.     

Systemic, but not pulmonary, hemodynamics are depressed during combined high thoraco-cervical epidural and general anesthesia in dogs

PURPOSE: An epidural block is frequently combined with general anesthesia. Both systemic and pulmonary hemodynamics may be affected by high epidural anesthesia and the combined general anesthetic. These effects were investigated in a canine model. METHODS: Systemic and pulmonary hemodynamics during a combined high thoraco-cervical epidural and general anesthesia were studied in dogs; the animals were anesthetized with propofol, 10 mg.kg(-1).hr(-1), or 2% sevoflurane, and then 1% mepivacaine, 5 mL, was injected epidurally between T1 and T2. Cardiac output (CO), pulmonary capillary wedge pressure (PCWP), pulmonary arterial pressure (PAP), mean arterial pressure (MAP), central venous pressure (CVP), electrocardiogram, and arterial and mixed venous gases were monitored for over 90 min after epidural mepivacaine. The interval between sevoflurane and propofol studies was two hours. RESULTS: Baseline measurement of MAP with sevoflurane anesthesia was significantly lower (P < 0.05-0.01) at every time point than with propofol anesthesia. After epidural mepivacaine (C1)-T7/8 blockade), MAP (P < 0.05-0.01), CO (P < 0.05-0.01), and heart rate (P < 0.05-0.01) decreased significantly during both propofol and sevoflurane anesthesia. In the sevoflurane group, stroke volume decreased significantly (P < 0.05-0.01) but recovered; however, MAP (P < 0.01) and CO (P < 0.05) did not recover 90 min after the injection. Mean CVP and systemic vascular resistance were not altered. There were no changes in mean PAP, mean PCWP, and pulmonary vascular resistance. CONCLUSION: A combined high thoracic/general anesthesia depressed systemic hemodynamics, whereas the pulmonary circulation was not affected. The extent of the depression varied with the general anesthetics used, sevoflurane and propofol.     

Haemodynamic Changes during Sodium Nitroprusside Induced Hypotension and Halothane/Nitrous Oxide Anaesthesia

The haemodynamic effects of nitroprusside (SNP) were studied in six patients undergoing surgery for intracranial aneurysm under controlled hypotension in endotracheal anaesthesia with halothane-nitrous oxide during hypocapnia. Mean arterial pressure was reduced with SNP from mean 12.25 kPa to mean 8.29 kPa (32%). There were concomitant statistically significant decreases in systemic vascular resistance (-21%), cardiac index (-17%), stroke index (-23%), pulmonary arterial mean pressure (-27%) and pulmonary capillary wedge pressure (-27%). Heart rate, central venous pressure and pulmonary vascular resistance did not change significantly. After the infusion of SNP was discontinued all parameters, except cardiac index and heart rate, returned to values not significantly different from the control values. The hypotension induced by SNP resulted from reductions in cardiac index and systemic vascular resistance. The reduction in cardiac index did not reach a critical level in any of the patients.     

Hemodynamics of coronary surgery patients following magnesium aspartate infusion]

Hypertension is a common phenomenon in patients undergoing aortocoronary bypass grafting. This hypertension increases myocardial oxygen consumption and can be prevented by application of vasodilators. A possible cause is activation of the renin angiotensin system. Magnesium is a potent vasodilator and has a beneficial effect after myocardial ischaemia. The study was performed to analyse the influence of magnesium infusion on the haemodynamic status and plasma renin activity in patients undergoing aortocoronary bypass grafting. METHODS. Eighteen patients (NYHA classification II-III) undergoing bypass surgery were divided into two groups, a magnesium and a control group. The magnesium group (n = 9) received 0.8 mEq/kg per h magnesium aspartate as an infusion for 15 min while still awake. After induction of anaesthesia, the magnesium infusion was reduced to 0.2 mEq/kg per h and stopped after aortic cannulation was completed. Plasma magnesium levels and concentrations within erythrocytes were measured. Anaesthesia was induced by flunitrazepam (0.01 mg/kg), fentanyl (0.005 mg/kg) and pancuronium (0.1 mg/kg). After intubation, patients were normoventilated with N2O/O2 = 1:1 and isoflurane (0.5-1.0 vol%). Additional doses of fentanyl (0.0025 mg/kg) were injected before the incision and before sternotomy. Mean arterial pressure, heart rate, cardiac index, total peripheral resistance, pulmonary vascular resistance, mean pulmonary arterial pressure, pulmonary capillary wedge pressure, left ventricular stroke work index, right ventricular stroke work index, intrapulmonary shunt and plasma renin activity were evaluated at five predefined points: (1) prior to magnesium infusion; (2) after magnesium infusion; (3) 10 min following induction of anaesthesia under steady-state conditions; (4) after sternotomy; (5) after aortic cannulation. RESULTS. Concerning the haemodynamic parameters (MAP, RAP, PAP, PCWP) no significant difference between the two groups could be demonstrated. In the control group peripheral resistance (TPR) was higher following sternotomy and aortic cannulation than in the magnesium group. Magnesium prevented decrease of the cardiac index (CI) under steady-state conditions, during sternotomy and following aortic cannulation. Left and right ventricular stroke work indexes (LVSWI and RVSWI) were higher in the magnesium group. Plasma renin levels were not significantly different between the two groups. CONCLUSION. Patients undergoing cardiac surgery benefit from magnesium administration in the pre-bypass phase. Due to its vasodilating effect, magnesium lowers the output impedance of the left ventricle and improves cardiac pumping function. It opposes detrimental cardiovascular responses to sternotomy and following aortic cannulation. Also of importance is the advantageous effect of magnesium on cardiac arrest elicited by cardioplegia and for reactivation of the ischaemic myocardium.     

Cardiovascular effects of etilefrine hydrochloride during abdominal aortic surgery

To counteract the decrease in blood pressure after release of the aortic cross-clamp, 2 mg etilefrine hydrochloride (Effortil; Boehringer Ingelheim) was administered intravenously to 13 patients undergoing aortofemoral bypass operations. It caused a statistically significant increase in mean arterial pressure, cardiac index, pulmonary capillary wedge pressure and left and right ventricular stroke work index. No significant changes were found in total peripheral resistance.     

Effect of intravenous clonidine on the dose of thiopental required to induce anesthesia.

A randomized, double-blind, controlled trial was conducted to investigate the influence of intravenous clonidine on thiopental dose requirements when used for induction of anesthesia and associated hemodynamic effects. Sixty ASA physical status I or II patients were randomly allocated to one of three treatment groups: normal saline solution (control, n = 20); clonidine (2.5 micrograms/kg, n = 20); or clonidine (5 micrograms/kg, n = 20). The test drug was administered 15 min before induction of anesthesia with intravenous thiopental. The dose of thiopental to produce loss of lash reflex was recorded as well as mean arterial blood pressure and heart rate at 3-min intervals up to induction of anesthesia and then at 1-min intervals for 5 min. Significant decreases in thiopental dose were observed in both groups receiving clonidine compared with the control group, but there was no significant difference between clonidine groups. With dosage calculated according to total body mass, the control group required 5.50 +/- 1.15 mg/kg (mean +/- SD) of thiopental, whereas those who received 2.5 micrograms/kg of clonidine required 4.15 +/- 1.46 mg/kg of thiopental (a reduction of 25%), and those who received 5.0 micrograms/kg of clonidine required 3.48 +/- 1.06 mg/kg of thiopental (a reduction of 37%). When thiopental dose was adjusted for lean body mass, similar reductions were obtained. Clonidine, in both doses, produced more sedation than control, and the 2.5-mg/kg dose produced less sedation than the larger dose. Mean arterial blood pressure was lower in the groups receiving clonidine. There were no significant differences in heart rate among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Thromboxane interaction with cardiopulmonary dysfunction in graded bacterial sepsis

The relationship between plasma levels of thromboxane A2, radioimmunoassayed as thromboxane B2 (TxB), and cardiopulmonary dysfunction in graded bacterial sepsis was investigated. Five adult female pigs under anesthesia were intubated and allowed to breathe room air spontaneously. Femoral arterial, venous, and pulmonary artery catheters were inserted. After a 60-minute control period Aeromonas hydrophila (1.0 X 10(9)/ml) was infused intravenously at 0.2 ml/kg/hr, gradually increasing to 4.0 ml/kg/hr over 4 hours. Arterial and mixed venous blood gases, hemodynamic measurements, and TxB plasma concentrations were obtained during the control period, at 10, 20, 30, 45, and 60 minutes and at 30-minute intervals thereafter. Cardiac index increased significantly from control at 20 minutes, remained above control levels for 1 hour, and then declined to significantly low values at 150 minutes. TxB was increased from control at 20 minutes, rising to four times control at 120 minutes. Mean arterial pressure, pulmonary capillary wedge pressure, left ventricular stroke work, paO2, and pvO2 decreased significantly during the experiment. Pulmonary artery pressure and pulmonary vascular resistance increased significantly. Changes in TxB were significantly cross-correlated with changes in cardiac index, pulmonary vascular resistance, stroke volume, left ventricular stroke work, and paO2. TxB elevations led the cross-correlated variables by 0 to 60 minutes. Pulmonary vascular resistance cross-correlated with mean arterial pressure and cardiac index. TxB is increased early in graded bacterial sepsis. Changes in TxB appear to precede impaired cardiopulmonary function. The data suggest that TxB is involved in the detrimental hemodynamic effects of early septicemia.     

Concentrated platelets harvesting before cardiopulmonary bypass improved cardiac and pulmonary function

BACKGROUND: Sequestration of concentrated platelets (P-con) during cardiopulmonary bypass (CPB) has been performed to preserve platelet function after cardiac surgery. Since P-con also harvests leukocytes simultaneously, there might be a possibility that the inflammatory effects or ischemia-reperfusion injuries associated with CPB, such as a cardiac or pulmonary dysfunction after cardiac surgery, are reduced with its use. METHODS: We retrospectively evaluated 53 patients who underwent cardiac surgery after the introduction of the P-con technique at our institute. There were 20 patients in the P-con group and 33 patients in the control group in whom concentrated platelet were not harvested. RESULTS: The patients characteristics and preoperative cardiac and pulmonary function did not differ between the two groups. The percentages of platelets and leukocytes sequestrated were 20.2+/-5.4% and 8.5+/-3.9% of the total estimated circulating cell counts, respectively. There were no significant differences in the postoperative dose of dopamine used, cardiac index, pulmonary capillary wedge pressure or intubation period between the two groups. However, the stroke volume index (p=0.005), left ventricular stroke work index (p=0.002), and ratio of the arterial oxygen tension to the inspired fraction of oxygen on extubation (p=0.02) were significantly greater in the P-con group as compared with those in the control. CONCLUSIONS: P-con improved cardiac and pulmonary function after CPB. Simultaneous sequestration of platelets and leukocytes by P-con during CPB may contribute to the improvement of cardiac and pulmonary function after cardiac surgery.     

The effects of pre-operative dexmedetomidine infusion on hemodynamics in patients with pulmonary hypertension undergoing mitral valve replacement surgery

BACKGROUND: The aim of this study was to investigate the effects of pre-operative dexmedetomidine infusion on hemodynamics in patients with pulmonary hypertension undergoing mitral valve replacement surgery. METHODS: Patients were randomly divided into placebo (group P, n= 16) and dexmedetomidine (group D, n= 16) groups. In group D, a 1 microg/kg bolus dose of dexmedetomidine was administered 10 min before the induction of anesthesia, followed by a 0.4 microg/kg/h infusion until the surgical incision. Anesthesia was induced with lidocaine (1 mg/kg), midazolam (0.2 mg/kg) and fentanyl (5 microg/kg) in both groups. Anesthesia was maintained with 0.5% isoflurane and fentanyl depending on the hemodynamic situation. The hemodynamic values during the investigation were obtained. RESULTS: In group D, the mean arterial pressure (MAP), mean pulmonary arterial pressure (MPAP) and pulmonary capillary wedge pressure (PCWP) were decreased effectively in comparison with the values in the placebo group (P < 0.05), and there was an attenuation in the increase in the systemic vascular resistance index (SVRI) and pulmonary vascular resistance index (PVRI) at the post-sternotomy period. CONCLUSIONS: The pre-operative administration of the alpha(2)-agonist dexmedetomidine decreases the fentanyl requirement and attenuates the increase in SVRI and PVRI at the post-sternotomy period relative to the baseline levels, and decreases effectively MAP, MPAP and PCWP in comparison with the values in the placebo group, in patients with pulmonary hypertension undergoing mitral valve replacement surgery.     

Central hemodynamic changes in experimental muscle crush injury in pigs

To investigate central and pulmonary hemodynamics in a standardized normovolemic experimental muscle injury model, 8 anesthetized and mechanically ventilated test pigs were intracavally infused with 100 ml of autologous muscle extract over a period of 100 min; 8 control pigs received Ringer's solution. The cardiac index decreased 20% and the heart rate decreased 10% within 30 min of starting the infusion in the muscle extract group and remained depressed. Mean arterial pressure increased significantly in both groups. The pulmonary capillary wedge pressure and central venous pressure remained relatively unchanged during the 5-hour study. A 2-fold increase in mean pulmonary arterial pressure and a nearly 4-fold increase in the pulmonary vascular resistance index was seen in the muscle extract infusion group, which however returned to normal. Arterial hemoglobin concentration and systemic vascular resistance index remained fairly stationary in both groups. Immediate significant decreases in both arterial oxygen saturation and arterial oxygen tension were observed in the muscle extract group, however both variables recovered towards the end of the experiment. A slight increase in arterial blood pH value was noted during the experiment. In conclusion, autologous muscle extract infusion causes decreases in heart rate and cardiac index, as well as a significant increase in pulmonary vascular tone and systemic hypoxemia, emphasizing the detrimental effects of skeletal muscle injury following severe trauma.     

Haemodynamic effects of propofol infusion for sedation after coronary artery surgery

We have compared the haemodynamic effects of a sedative dose of propofol with placebo (vehicle of propofol) in a randomized, double- blind study in 20 patients immediately after coronary artery bypass grafting (CABG). During a continuous infusion of a mixture of fentanyl and pancuronium, each patient was given in a crossover design, a loading dose of propofol 0.5 mg kg-1 and vehicle over 5 min followed by a continuous infusion of propofol 20 micrograms kg-1 min-1 and vehicle, respectively, for 55 min. Administration of propofol caused a significant decrease in mean arterial pressure (mean change from pre- drug values to those during drug infusion: -15.4% vs +1.3% with placebo; P < 0.001), mean pulmonary artery pressure (-6.5% vs +5.8%; P < 0.001), systemic vascular resistance (-13.8% vs -0.6%; P < 0.05), pulmonary vascular resistance (-2.0% vs +9.0%; P < 0.05), cardiac output (-2.4% vs +2.6%; P < 0.05) and pulmonary artery occlusion pressure (-8.0% vs +1.4%; P < 0.05). Propofol did not affect heart rate, but it tended to decrease stroke volume (P = 0.102). These data suggest that, during the recovery phase from CABG surgery, a short-term infusion of a sedative dose of propofol decreases systemic and pulmonary arterial pressure by decreasing systemic and pulmonary vascular resistance, respectively, and cardiac output. The decrease in cardiac output appeared to be caused mainly by a decrease in stroke volume.      

Thiopental Modification of Ischemic Spinal Cord Injury in the Dog

Spinal cord ischemia was produced in male mongrel dogs by permanent occlusion of the infrarenal aorta. All animals were anesthetized with a mixture of nitrous oxide and 1.5% halothane. Group 1 animals were the controls. Group 2 animals were pretreated, 30 minutes prior to aortic occlusion, with sodium thiopental, 20 mg per kilogram of body weight, over 5 minutes, followed by an infusion of 10 mg/kg/hr for 2½ hours. Groups 3 animals received the identical dose of sodium thiopental and, in addition, received mannitol, 1 gm/kg, and methylprednisolone 1 mg/kg. There were no differences in hemodynamic data or arterial blood gases among the groups, except that the thiopental bolus caused a transient reduction in mean arterial pressure.Ninety percent of Group 1 animals were paraplegic, while only 30% of Group 2 and 40% of Group 3 animals were paraplegic. The difference in the incidence of paraplegia in Groups 2 and 3 compared with Group 1 was statistically significant (p < 0.05). Therefore, thiopental significantly decreased the incidence of paraplegia, while methylprednisolone and mannitol did not enhance its protective effect.