Syringe pumps for infusion of vasoactive drugs: mechanical idiosyncrasies and recommended operating procedures

Syringe pumps for vasoactive infusions have the advantages of small size and weight, portability, and low cost of the disposable components. However, limited syringe capacity necessitates the use of high drug concentrations, and the accidental delivery of even a small volume of infusate could seriously alter the patient's hemodynamics. To determine the circumstances under which drug delivery might be delayed, or inadvertent boluses could be delivered into the manifold, two brands of commercially available clinical syringe pumps were connected to a stopcock manifold via small-bore tubing and a series of tests were performed. When the syringe pumps were operated at 3 mL/h against a closed stopcock, the pumps' occlusion alarms did not sound for 18-22 min, and when the stopcock subsequently was opened, 0.6-0.9 mL of infusate was delivered as a bolus. Elevating the syringe pump by 120 cm resulted in the delivery of up to 0.5 mL of infusate with the pump turned off. When a syringe pump operating at 6 mL/h was turned off, typically an additional 0.05 mL was delivered during the ensuing 2-3 min. Depending upon the method used to flush the tubing prior to use, delays in drug delivery of 2-3 min occurred at an infusion rate of 3 mL/h. These observations emphasize the need for careful equipment setup and proper use of the manifold stopcocks to avoid unintended drug administration or delay in drug administration.     

Design flaw can convert commercially available continuous syringe pumps to intermittent bolus injectors

OBJECTIVE: To investigate if unexpected behaviour of neonatal and paediatric patients connected to syringe pumps could be explained by transient elevation of these devices. DESIGN: Five different commercially available syringe-pumps were set at an infusion rate of 1 ml/h and then subjected to a vertical displacement manoeuvre (height 1 m). The actual delivered infusion volumes in association with the displacement manoeuvre were measured by a high precision weight scale connected to a computer. SETTING: A medical technology laboratory in a university hospital. MEASUREMENTS AND RESULTS: Elevation of the devices resulted in a rapid bolus injection of 0.19-2.28 ml. Returning the devices to their original positions resulted in an aspiration into the system of 0.06-0.34 ml. The times both for bolus injection and for aspiration into the system were less than 1 min in all cases. The updown manoeuvre was followed by a period with zero infusion ranging from 8 to 105 min. CONCLUSIONS: Design flaws in the construction of syringe pumps can expose patients to substantial danger following vertical displacement if potent drugs are being infused. If potent drugs are infused, care should be taken not to change the vertical position of the syringe pump even for short periods of time. Before buying new equipment, the authors recommend that the delivery characteristics of these devices should not only be tested during ordinary bench testing but should also include the reaction to a vertical displacement manoeuvre.     

Fluctuation of injection pressure of syringe pumps; the effect of syringe volumes and speed settings

We measured fluctuation of injection pressure by several types of commercially available syringe pumps in order to investigate the effect of syringe volumes (Terumo syringe) and speed settings on the irregularity of injection speeds. We recorded the injection pressure continuously with various speed settings, except that one of the pumps injected irregularly at the settings of 2 and 1 ml.h-1. With 50 ml syringes, only two of the six pumps injected precisely at all the speed settings. With the other four types, a steep increase in pressure was recorded at the speed setting of 1 ml.h-1. However irregular infusion was never observed by using a syringe of a high resistant type (TOP syringe). With 30 ml syringes, injection pressures fluctuated in most of the six syringe pumps at a speed lower than 5 ml.h-1. In conclusion, changes in injection pressures depend on types of syringes, syringe volumes and speed settings. We urge not to use a 30 ml syringe to infuse vasoactive drugs with syringe pumps.     

Clinical evaluation of a new programmable syringe infusion pump

A new programmable syringe infusion pump, Auto Syringe Model AS 40 A, was evaluated for infusion of muscle relaxants, vasodilators and opioids in 4 surgical patients. Every drug mentioned above was easily adjusted according to surgical requirement in these patients. Auto Syringe Model AS40A is light and compact. Its major advantages lie in the mechanisms for delivery of a bolus dose and automated delivery of intermittent doses, automatic rate calculation, and the applicability to various sizes of syringes. Auto Syringe Model AS40A was found to be very useful for intravenous infusion of drugs.     

Short-term hemodynamic effects of mibefradil in dogs with chronic heart failure: comparison with diltiazem

Despite the marked vasodilator and antiischemic actions of existing calcium channel blockers, their use in the treatment of patients with chronic heart failure (HF) remains highly controversial. We compared the short-term hemodynamic effects of i.v. mibefradil, a predominant T-type calcium channel blocker with only partial L-type calcium channel antagonism, and diltiazem, a selective L-type calcium channel antagonist in dogs with chronic HF. Each of three drugs namely, mibefradil, diltiazem and normal saline (as placebo control), were studied in random order (6 days between each drug intervention), in each of 8 dogs with chronic HF produced by multiple intracoronary microembolizations. Intravenous mibefradil and diltiazem were administered as a 100 micrograms/kg bolus followed by a continuous infusion of 6 and 4 micrograms/kg/min, respectively, for 15 min. Equal volumes of normal saline were administered in an identical fashion. In all instances, hemodynamics were obtained at base line and at 5, 10, 15, 30 and 60 min after bolus drug administration. Left ventriculograms were obtained at baseline, and at 15 and 60 min after bolus drug administration. Saline infusion had no effects on hemodynamic or angiographic indexes of left ventricular (LV) function. At 15 min, mibefradil caused significant increases of LV stroke volume and LV ejection fraction compared to baseline (40 +/- 5 vs. 31 +/- 3 ml, P < .05 and 41 +/- 1 vs. 28 +/- 1%, P < .05, respectively). In contrast, at 15 min, diltiazem produced no significant changes of LV stroke volume or ejection fraction compared to baseline despite reducing mean aortic pressure to the same extent as mibefradil. Short-term i.v. mibefradil improves LV function in dogs with chronic HF. The beneficial effects of mibefradil compared to diltiazem may be a consequence of T-type calcium channel selectivity resulting in a vasodilatory response that is free of negative inotropy.     

Continuous analgesia with a femoral catheter: plexus or femoral block?

OBJECTIVE: To evaluate the spread and quality of sensitive blockade produced by continuous and prolonged use of a femoral catheter inserted for postoperative analgesia. STUDY DESIGN: Prospective non comparative evaluation. PATIENTS: The study included 20 consecutive patients undergoing major knee surgery with postoperative analgesia obtained with a femoral catheter, a technique commonly used in our department. METHODS: Regional analgesia was induced after surgery with a bolus injection of 30 mL of 2% lidocaine with 1:200,000 epinephrine 1 in 200,000, maintained by continuous infusion of 1% lidocaine + morphine 0.03 mg.mL-1 + clonidine 2 micrograms.mL-1 for 48 h. The infusion rate was 0.1 mL.kg-1.h-1. The evaluation was based on: 1) the quality of analgesia at rest, at 30 min, h1, h3, h6, h12, h24 and h48; 2) the sensitive and motor blockade at the same time intervals. RESULTS: A "3 in 1" block was only observed in 50% of patients after the initial bolus via the femoral catheter. During the maintenance of analgesia with a continuous infusion a blockade of the three main nerves of the lumbar plexus occurred in less than 20% of patients after 6 h and was limited to the territory of the femoral nerve in 45 to 50% of patients after 12 to 48 h. In all cases the median values of VAS were below 42 mm. CONCLUSION: In most patients, a local anaesthetic administered continuously via a femoral catheter produces a blockade limited to the femoral nerve. These data do not substantiate the conclusions by those who consider they are producing a continuous "3 in 1" block with this technique. However, it is obviously not essential to produce a sensitive blockade of the three main nerves of the lumbar plexus to obtain an effective analgesia after knee surgery.     

Renovascular interaction of epinephrine, dopamine, and intraperitoneal sepsis

OBJECTIVE: To determine the effect of intraperitoneal sepsis on the systemic and renal actions of the continous infusion of epinephrine or dopamine, and during the concurrent administration of both drugs. DESIGN: Prospective, randomized study. SETTING: Laboratory at a university hospital. SUBJECTS: Seven conscious, chronically catheterized, adult merino sheep. INTERVENTIONS: Epinephrine at 40 micrograms/min or dopamine at 2 micrograms/kg/min, or both drugs concurrently were infused for 4 hrs on separate study days in healthy sheep. This protocol was then repeated following the induction of sepsis after the intraperitoneal injection of 10(11) Escherichia coli, 10(12) Bacteroides fragilis, and bran. MEASUREMENTS AND MAIN RESULTS: Systemic oxygen delivery (DO2) and consumption were measured using thermodilution cardiac output and measured oxygen content. Renal blood flow was measured using an electromagnetic flow transducer, and creatinine clearance was calculated as the quotient of renal blood flow and the renal extraction ratio of creatinine. Infusion of epinephrine augmented systemic DO2 and mean arterial pressure (MAP) during both healthy and septic studies. Systemic oxygen consumption was only increased during epinephrine infusion in the septic study. During the healthy animal study, renal blood flow was initially decreased during epinephrine infusion, but increased to 36% above baseline (p = .003). However, creatinine clearance remained unchanged. During the experimental sepsis study, the infusion of epinephrine had less marked effects on renal blood flow (unchanged from baseline), while an initial reduction (15 mins) in creatinine clearance (p = .04) was not sustained and had returned to baseline by 3 hrs. Dopamine alone produced no change in systemic oxygen variables or MAP during the studies on healthy or septic animals. Although dopamine produced renal vasodilation and an increase in renal blood flow in the healthy state, these results were not found during the septic state. In addition, concurrent infusion of dopamine with epinephrine did not alter the systemic or renal effects of epinephrine during the healthy or septic states. CONCLUSIONS: These results do not support the routine use of low-dose dopamine, and demonstrate a change in renovascular responses to catecholamines during intraperitoneal sepsis. The infusion of epinephrine at 40 micrograms/min had few deleterious effects on the kidney, and augmented both MAP and systemic DO2. Its role as a catecholamine in the management of sepsis may need to be reconsidered.     

Basal and stimulated sympathetic responses after epinephrine: no evidence of augmented responses

Delayed facilitation of norepinephrine release through the action of epinephrine (NE) at presynaptic beta-adrenoceptors has been postulated to account for the delayed hemodynamic effects of epinephrine and to be a mechanism causally related to the development of hypertension. To determine whether a short-term increase in epinephrine concentrations resulted in subsequent facilitation of sympathetic responses, 9 healthy subjects (age, 21+/-0.9 years) were studied at rest and during physiological stress on 2 occasions when they received an infusion of either saline or epinephrine (20 ng/kg per minute) in random order. Heart rate, blood pressure, forearm blood flow, epinephrine concentrations, and NE spillover were measured at rest, during mental stress (Stroop test), and during a cold pressor test. Measurements were performed before, during the 1-hour infusion of epinephrine or placebo, and 1 hour after the infusion. A radioisotope dilution method was used to measure NE spillover. Hemodynamic measurements and NE spillover were increased during the infusion of epinephrine, but 1 hour after discontinuation of epinephrine there was no significant augmentation of hemodynamic or sympathetic responses. NE spillover 1 hour after saline or epinephrine infusion was similar (0.85+/-0.2 versus 0. 87+/-0.2 microg/min; P=0.92). In addition, there was no delayed facilitation of stress-induced hemodynamic or NE responses after epinephrine. These findings do not support the hypothesis that epinephrine results in delayed facilitation of NE release.     

Helicobacter pylori eradication in the healing and recurrence of benign gastric ulcer: a two-year, double-blind, placebo controlled study

STUDY OBJECTIVE: To evaluate the safety and efficacy of monitored anesthesia care (MAC) in patients who undergo a novel treatment for hepatocellular cancer in which procedure-related hemodynamic instability is problematic. DESIGN: Nonrandomized open study. SETTING: University cancer center operating room. PATIENTS: Nine patients scheduled for hepatic arterial infusion of doxorubicin with complete hepatic venous isolation and extracorporeal chemofiltration (no more than 3 procedures per patient). INTERVENTIONS: Hepatic venous isolation was achieved with a dual-balloon inferior vena cava catheter connected to an extracorporeal circuit containing chemofilters. Doxorubicin was infused through the hepatic artery and filtered from the venous blood, which was returned to the patient through an internal jugular venous catheter. Each patient received a bolus of propofol (200 micrograms/kg) and one of alfentanil (2 micrograms/kg) followed by simultaneous infusions of propofol and alfentanil for percutaneous placement of the catheters and operation of the extracorporeal circuit. Drug rates were varied to maintain a sedative-analgesic state of calm, comfort, minimal movement, and adequate respiratory function. Prior to circuit initiation, patients were preloaded with crystalloid. During circuit operation, hypotension was treated with intravenous (IV) phenylephrine and crystalloid. MEASUREMENTS AND MAIN RESULTS: End-tidal CO2 (PETCO2), respiratory rate, oxygen saturation (SaO2), arterial blood pressure (BP), and heart rate (HR) were monitored. Systolic, diastolic, and mean arterial pressure (MAP), and HR were compared before, during, and after hepatic venous isolation and chemofiltration. Doses and infusion rates of propofol, alfentanil, and phenylephrine were recorded for each treatment. Hypotension occurred in 11 of 13 procedures when blood was directed through the chemofilters and was successfully treated with phenylephrine (dose range 40 to 5,733 micrograms) and crystalloid. Blood pressure returned to the baseline value on termination of the circuit. Throughout the sedation, patients were easily arousable, analgesia was adequate, and PETCO2 level of 38 +/- 4 mmHg and SaO2 greater than 94% were maintained. Mean doses and infusion rates of MAC drugs were, respectively: propofol, 261 +/- 88 mg and 23.7 +/- 3.6 micrograms/kg/min; alfentanil, 3,350 +/- 1,468 micrograms and 0.32 +/- 0.14 microgram/kg/min. CONCLUSIONS: Patients undergoing this novel cancer treatment are safely and effectively managed by MAC achieved with simultaneous infusions of alfentanil and propofol. Procedure-associated hypotension is easily treated with IV phenylephrine and crystalloid.     

Infusion devices: risks and user responsibilities

The Medical Devices Agency of the UK Department of Health continues to receive and investigate reports of incidents that arise from the use of infusion devices. In 1996, the Medical Devices Agency received some 4300 reports of incidents, over 400 of which were classified as infusion-, transfusion-, or dialysis-related. There is, however, a trend towards more active management of medical devices focusing on aspects such as purchasing, training, clinical use, and maintenance, and clearly, nursing staff have an important role in developing such policies. Also, nurses with the responsibility for setting up and overseeing infusions should be aware of some of the problems that can arise during routine use, as an awareness of potential hazards allows users to manage the risks more effectively. This article examines some of the risks associated with the use of infusion devices; in particular, problems that arise while loading the administration set or syringe into the pump, the risks of fluid free flow and syringe siphoning, and the risks from air embolism, flow rate accuracy and infusion pump pressure.     

Tumour cell killing using chemically engineered antibody constructs specific for tumour cells and the complement inhibitor CD59

BACKGROUND: Although beta blockers have been used primarily to decrease unwanted perioperative hemodynamic responses, the sedative properties of these compounds might decrease anesthetic requirements. This study was designed to determine whether esmolol, a short-acting beta 1-receptor antagonist, could reduce the propofol concentration required to prevent movement at skin incision. METHODS: Sixty consenting patients were premedicated with morphine, and then propofol was delivered by computer-assisted continuous infusion along with 60% nitrous oxide. Patients were randomly divided into three groups, propofol alone, propofol plus low-dose esmolol (bolus of 0.5 mg/kg, then 50 micrograms.kg-1.min-1), and propofol plus high-dose esmolol (bolus of 1 mg/kg, then 250 micrograms.kg-1.min-1). Two venous blood samples were drawn at equilibrium. The serum propofol concentration that prevented movement to incision in 50% of patients (Cp50) was calculated by logistic regression. RESULTS: The propofol Cp50 with nitrous oxide was 3.85 micrograms/ ml. High-dose esmolol infusion was associated with a significant reduction in the Cp50 to 2.80 micrograms/ml (P < 0.04). Propofol computer-assisted continuous infusion produced stable serum concentrations with a slight positive blas. Esmolol did not alter the serum propofol concentration. No intergroup differences in heart rate or blood pressure response to intubation or incision were found. CONCLUSIONS: Esmolol significantly decreased the anesthetic requirement for skin incision. The components and mechanism of this interaction remain unclear. A simple pharmacokinetic interaction between esmolol and propofol does not explain the Cp50 reduction. These results demonstrate an anesthetic-sparing effect of a beta-adrenergic antagonist in humans under clinically relevant conditions.     

Study on clinical effect of a continuous intravenous infusion of azasetron against nausea and vomiting induced by anticancer drugs including CDDP

Azasetron, a selective 5-HT3 receptor antagonist, has been previously shown to be highly effective in the prophylaxis of nausea and vomiting induced by anticancer drugs and is widely used in the clinical setting in Japan. In order to improve the antiemetic effect of azasetron, we designed a continuous intravenous infusion method of this drug and compared the antiemetic effect of this method with that of standard bolus intravenous injection on nausea and vomiting associated with anticancer drugs including 75 mg/m2 cisplatin (CDDP). A continuous group is intravenous bolus injection of 2.5 mg azasetron followed by 7.5 mg continuous intravenous infusion for 24 hrs, and a bolus group is intravenous bolus injection of 10 mg azasetron. The inhibitory effect on nausea of the continuous group was significantly superior to those of the bolus group on day 3 and 4 (p < 0.05) and inhibitory effect on vomiting of the continuous group was significantly superior to those of bolus group on day 2 (p < 0.05). No adverse effects were observed in either group of this study. From these data, continuous intravenous infusion of azasetron was considered to be highly effective in prophylaxis of nausea and vomiting induced by anticancer drugs.     

Incremental bolus versus a continuous infusion of propofol for deep sedation/general anesthesia during dentoalveolar surgery

PURPOSE: This article compared the use of the traditional incremental bolus technique with the continuous infusion technique for the administration of propofol for deep sedation/general anesthesia. PATIENTS AND METHODS: Patients were sedated with midazolam and fentanyl and then had maintenance of an anesthetic state achieved with propofol administered by either of the two techniques. Data were collected to evaluate the overall surgical/anesthetic procedure, movement of the patient, and his or her hemodynamic status. RESULTS: Both groups received a mean maintenance dose of propofol exceeding 6 mg/kg/hr. However, the patients in the continuous infusion group received a statistically greater maintenance dose (continuous infusion + supplemental vs incremental bolus). All patients were maintained in a deep sedation/general anesthetic state. Respiratory and blood pressure values were comparable in both groups. However, the continuous infusion group showed improved hemodynamic stability manifested as fewer fluctuations in heart rate. Visual analog scale (VAS) questionnaires completed by the surgeon and surgical assistant reported less patient movement and improved surgical/anesthetic conditions with the continuous infusion technique. Recovery of the two groups was comparable. CONCLUSION: This study, although finding advantages in the continuous infusion technique, showed satisfactory conditions associated with both techniques.     

Static and dynamic characteristics of fluid-filled esophageal manometry systems

Esophageal manometric systems with water-filled catheters have been characterized by the use of model experiments. The examined parameters have been: catheter dimension, catheter compliance, catheter resistance, pump type, pump compliance, and perfusion flow. Accurate static pressure measurements have been obtained for perfused systems independently of the investigated parameters. The dynamic characteristics vary with catheter diameter and perfusion flow. For catheters with low diameter, a narrow bandwidth is obtained for the investigated perfusion flows. The results have been expressed in terms of an electric model of the measurement system. Perfusion pumps with low compliance are recommended to improve the dynamic properties of the measurement system.     

Obstetric analgesia using continuous epidural perfusion of bupivacaine, adrenaline, and fentanyl

OBJECTIVES: To determine the efficacy and complications of continuous epidural perfusion of bupivacaine, adrenaline and fentanyl in the relief of pain during first and second stage labour during vaginal birth. PATIENTS AND METHODS: Between January 1990 and March 1993 we used continuous epidural perfusion for control of pain during labor in 1307 women. The solution administered through an epidural catheter and maintained until expulsion was one 10 ml bolus of bupivacaine 0.25% with adrenaline 1:200,000 and fentanyl 25 micrograms followed by continuous perfusion of bupivacaine 0.0625% with adrenaline 1:200,000 and fentanyl 2 micrograms/ml at an infusion rate of 12 ml/h. When analgesia was insufficient, a bolus of local anesthetic was administered or a pudendal block was carried out. RESULTS: Ninety-two percent of the birthing women reported good analgesic effect during the first stage; for 7% the effect was fair and for 0.55% it was poor. During the second stage 88% reported satisfactory analgesia, and 8% fair or poor. Assessment was not possible for the remaining women, who underwent cesarean sections. Complications were few and easily controllable. CONCLUSIONS: Maintenance of epidural perfusion with 0.0625% bupivacaine with adrenaline 1:200,000 and fentanyl 2 micrograms/ml provides sufficient analgesia during all stages of childbirth.     

Effect of octreotide on systemic, central, and splanchnic haemodynamics in cirrhosis

BACKGROUND/AIMS: Cirrhosis with portal hypertension is associated with changes in the splanchnic and systemic haemodynamics, and subsequent complications, such as bleeding from oesophageal varices, have led to the introduction of long-acting somatostatin analogues in the treatment of portal hypertension. However, reports on the splanchnic and systemic effects of octreotide are contradictory and therefore the aim of the present study was to assess the effects of continuous infusion of octreotide on central and systemic haemodynamics, portal pressures, and hepatic blood flow. METHODS: Thirteen patients with cirrhosis underwent liver vein catheterisation. Portal and arterial blood pressures were determined at baseline and 10, 30, and 50 min after a bolus injection of octreotide 100 micrograms, followed by continuous infusion of octreotide 100 micrograms/ h for 1 h. Hepatic blood flow, cardiac output, central and arterial blood volume, and central circulation time were determined at baseline and 50 min after the start of the octreotide infusion. RESULTS: The mean arterial blood pressure increased during the first 10 min (p < 0.0005), but returned to baseline after 50 min. The central and arterial blood volume (-16%, p < 0.005) and the central circulation time (-8%, p < 0.05) were significantly decreased after 50 min, whereas the cardiac output did not change significantly. The hepatic venous pressure gradient and the hepatic blood flow did not change significantly at any time after infusion of octreotide. CONCLUSIONS: Octreotide does not affect the portal pressure or hepatic blood flow, whereas it may further contract the central blood volume and thereby exert a potentially harmful effect on central hypovolaemia in patients with cirrhosis. However, these early effects do not exclude the possibility that administration of longacting somatostatin analogues over a longer period may have a beneficial effect.     

Anesthetic management of a patient with hypertrophic cardiomyopathy using propofol, fentanyl and ketamine

A 59-year-old male with hypertrophic cardiomyopathy was scheduled for resection of a maxillary cyst. Metoprolol was discontinued the day before surgery. Thirty min before anesthesia, meperidine 35 mg was administered intramuscularly. After intravenous administration of midazolam 3 mg, a pulmonary catheter was inserted for monitoring hemodynamic parameters. Anesthesia was induced with propofol 75 mg, fentanyl 0.15 mg and ketamine 75 mg. Anesthesia was maintained with continuous infusion of propofol 5 mg.kg-1.h-1 and ketamine 1 mg.kg-1.h-1. Moreover, fentanyl was added as necessary during surgery. Blood pressure (BP), pulmonary arterial pressure (PA), systemic vascular resistance index (SVRI) and pulmonary vascular resistance index (PVRI) were measured using a pulmonary catheter during anesthesia. Since BP decreased after intubation, dopamine 3 micrograms.kg-1.min-1 was administered for 20 min. The hemodynamic state was stable during surgery. However, BP, PA, SVRI and PVRI increased temporally at extubation. His postoperative course was uneventful. In conclusion, total intravenous anesthesia with propofol, fentanyl and ketamine may be useful for anesthetic management of a patient with hypertrophic cardiomyopathy.     

Terlipressin (glypressin) versus somatostatin in the treatment of bleeding esophageal varices--final report of a placebo-controlled, double-blind study

One hundred and six episodes of bleeding from esophageal or gastric varices in 72 patients with cirrhosis of the liver were randomized to treatment either with intravenous terlipressin 2 mg initially and 1 mg every four hours for 24 hours together with bolus injection and continuous infusion of placebo, or with somatostatin 250 micrograms as a bolus and continuous infusion of 250 micrograms/h somatostatin for 24 hours and placebo injections. Standard treatment with transfusions, fluid and electrolyte correction, and lactulose was administered in both groups. In the terlipressin group, 48 out of 53 bleeding episodes (91%) and in the somatostatin group 43 out of 53 bleeds (81%) were initially stopped by the vasoactive drugs. Four of the five bleeds not arrested by terlipressin, and nine of the ten bleeds not arrested by somatostatin, were stopped by balloon tamponade. In one patient in each group variceal bleeding could not be stopped initially, and both patients died. The failure rate of the vasoactive treatment alone, including rebleeds within the study period, was 17% in the terlipressin, and 28% in the somatostatin, group. The initial hemostasis, including balloon tamponade, were 98%, and the definitive bleeding control rates were 89% in both groups. The hospital mortality rate was 21% (11/53) in the terlipressin, and 21% (11/53) in the somatostatin, group. Blood transfusions and duration of bleeding did not differ significantly. The study indicates that a large proportion of bleeds from esophageal and fundic varices can be stopped initially (86%) and definitively controlled (77%) by vasoactive drugs alone.     

Hemodynamic and regional blood flow responses to nicotine at rest and during exercise

We hypothesized that nicotine compromises cardiovascular responses to dynamic exercise. Hemodynamic variables were measured in conscious miniswine before and at 2 min of nicotine infusion (20 micrograms.kg-1.min-1; i.a.; N = 6) during resting conditions. Mean arterial pressure elevations (MAP; 14%) and plasma nicotine concentrations (49 +/- 7 ng.ml-1) were similar to those elicited by cigarette smoking in humans. In addition, nicotine increased systemic vascular resistance (SVR; 56%), the heart rate x systolic blood pressure product (RPP; 11%), and regional vascular resistance in the left-ventricular, renal, and splanchnic circulations, while cardiac output decreased (CO; 23%) and skeletal muscle blood flow and vascular resistance were unaffected. Plasma norepinephrine and epinephrine increased by approximately 30% and 90%, respectively. On separate days, the same hemodynamic responses were measured before and at 20 min of treadmill running during vehicle or nicotine infusion for the last 2 min of exercise (N = 10). Nicotine increased MAP (6%), SVR (14%), and RPP (3%), and elevated vascular resistance in the proximal colon and pancreas. Moreover, compared to exercise + vehicle, norepinephrine and epinephrine increased by approximately 13% and 24%, respectively, during exercise + nicotine infusion. These findings suggest that the detrimental effects of nicotine observed at rest are minimized during exercise. Nicotine's effects may be reduced during exercise by competition from local vasodilators in the heart and active musculature, and/or by differing activation of sympathetic nerve activity.