Allow elective ventilation to recruit more organ donors

Transplantation surgery started >50 years ago and has developed into an established medical practice in many countries. We consider it positive if our dead body could be used as an organ or tissue donor. If transplanted, our organs confer other human beings with a longer and better life. There is, however, a relative lack of organs compared with the needs, and many potential recipients die while on the waiting list for transplantation.

Thermogenic effect of amino acids not demonstrated in heart surgery with cardiopulmonary bypass

BACKGROUND

In abdominal surgery and in healthy volunteers, amino acids increased thermogenesis. In this double-blind study we investigated if a similar effect would ensue in heart surgery and accelerate the rewarming process postoperatively.

METHODS

Thirty-four patients undergoing coronary artery bypass grafting or aortic valve replacement were randomized into two groups, and received either 500 ml of amino acids or Ringer's solution intravenously during 4 h. The infusion was started approximately 30 min before the end of a cardiopulmonary bypass (CPB), performed at a temperature of 34 degrees C with rewarming to 36-37 degrees C. The lowest pulmonary artery (PA) temperature after the CPB and the time interval until the temperature reached 37 degrees C were recorded. Oxygen uptake was calculated from cardiac output (thermodilution) and the pulmonary av-difference of oxygen after induction of anaesthesia, at the end of surgery, and 1 and 2 h after the CPB.

RESULTS

Demographic data, medication including beta-blockers, CPB data and case mix were similar. The lowest temperature after the CPB was 35.9 +/- 0.1 degrees C in the amino acid group and 35.6 +/- 0.2 degrees C in the control group, and the increase per hour was 0.6 +/- 0.1 degrees C and 0.6 +/- 0.0 degrees C, respectively, with no differences between the groups. During the infusion, oxygen uptake was higher in the amino acid group, 115 +/- 4 ml m(-2), than in the controls, 102 +/- 3 ml m(-2) (P < 0.05). No adverse effects of the infusions were noted.

CONCLUSION

The lack of a thermal effect of the amino acids in the heart surgery was most probably due to the temperature gradients between the different body compartments, and also may have been due to the use of beta-blockers.

Brain death: an important paradigm shift in the 20th century

The description of death in medical or pathophysiological terms changed during the last century. The focus of attention shifted from the condition of the heart to the state of the brain. The current paper investigates the time period from 1866, when the effects of an increased intracranial pressure (ICP) were studied experimentally, to 1967, when the first heart transplantation was performed. Between 1894 and 1965 four neurosurgeons: Horsley in England, Cushing in USA, Wertheimer in France and Frykholm in Sweden made important contributions. Documented discussions, if ventilator treatment should be stopped in patients with a dead brain and a beating heart, began in 1959. However, already during the latter part of the 19th century it was shown that the heart could continue to beat if artificial ventilation was performed, when spontaneous respiration had ceased due to a high ICP. Furthermore, brain death was by chance implemented in clinical practice in heart surgery with cardiopulmonary bypass (CPB) some years before the expressions 'death of the nervous system' and 'brain death' were coined.

Better preserved pulmonary endothelium-dependent vasodilation with off-pump coronary surgery

OBJECTIVE

To investigate if endothelium-dependent vasodilation in the pulmonary circulation was better maintained after off-pump coronary artery bypass grafting (CABG). An impaired pulmonary vascular response to acetylcholine has been observed after cardiopulmonary bypass (CPB) in children, adults and experimentally.

DESIGN

Fourteen patients operated off-pump were compared with 21 patients undergoing conventional CABG with CPB. The indexed pulmonary vascular resistance was measured before and during an infusion of acetylcholine, aiming at a concentration of 10(-6) mol/l in the pulmonary artery. Twelve patients operated on-pump received saline instead of acetylcholine.

RESULTS

Before surgery pulmonary vascular resistance decreased during infusion of acetylcholine by 28% and 25% in the off-pump and on-pump groups. After surgery the decrease was 16% and 6%, respectively (p = 0.028 and p < 0.001, compared to preoperative response). The response did not differ between the two groups before, but did so after surgery (p = 0.01). Saline had no effect.

CONCLUSION

The better maintained endothelium-dependent vasodilation in the off-pump group indicated less endothelial dysfunction.

High serum S100B levels for trauma patients without head injuries

OBJECTIVE

Studies of patients with head trauma have demonstrated a correlation between a serum marker of brain tissue damage, namely S100B, and neuroradiological findings. It was recently demonstrated that the increases in serum S100B levels after heart surgery have extracerebral origins, probably surgically traumatized fat, muscle, and bone marrow. The current study examined multitrauma patients without head trauma, to determine whether soft-tissue and bone damage might confound the interpretation of elevated serum S100B concentrations for patients after head trauma.

METHODS

A commercial assay was used to determine serum S100B concentrations for a normal population (n = 459) and multitrauma patients without head injury (n = 17). Concentrations of the two subtypes of S100B (S100A1B and S100BB) were determined using separate noncommercial assays.

RESULTS

The mean serum S100B concentration for a normal healthy population was 0.032 microg/L (median, 0.010 microg/L; standard deviation, 0.040 microg/L). The upper 97.5% and 95% reference limits were 0.13 and 0.10 microg/L, respectively. No major age or sex differences were observed. Among trauma patients, serum S100B levels were highest after bone fractures (range, 2-10 microg/L) and thoracic contusions without fractures (range, 0.5-4 microg/L). Burns (range, 0.8-5 microg/L) and minor bruises also produced increased S100B levels. S100A1B and S100BB were detected in all samples.

CONCLUSION

Trauma, even in the absence of head trauma, results in high serum concentrations of S100B. Interpretation of elevated S100B concentrations immediately after multitrauma may be difficult because of extracerebral contributions. S100B may have a negative predictive value to exclude brain tissue damage after trauma. Similarly, nonacute S100B measurements may be of greater prognostic value than acute measurements.

Increase in serum S100A1-B and S100BB during cardiac surgery arises from extracerebral sources

BACKGROUND

Elevated levels of serum S100B after coronary artery bypass grafting may arise from extracerebral contamination. Serum S100B content was analyzed in several tissues, and the two dimers S100A1-B and S100BB were analyzed separately in blood.

METHODS

Serum, shed blood, marrow, fat, and muscle were studied in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass using suction either to the cardiotomy reservoir (group 1, n = 10) or to a cell-saving device (group 2, n = 10), or operated on off-pump (group 3, n = 10).

RESULTS

Serum S100B was sixfold higher in group 1 than in groups 2 and 3, which were identical. The same ratio between S100A1-B and S100BB was found in all groups. When compared with serum, S100B was 10(2) to 10(4) times higher in marrow, fat, muscle tissue, and shed blood.

CONCLUSIONS

Separate analysis of S100A1-B and S100BB did not distinguish between S100B of cerebral and extracerebral origin. The concept that S100B only originates in astroglial and Schwann cells is wrong. Fat, muscle, and marrow in mediastinal blood contain high levels of S100B. Cardiopulmonary bypass caused no increase in S100B.

No effect of L-arginine supplementation on pulmonary endothelial dysfunction after cardiopulmonary bypass

BACKGROUND

Acetylcholine is an endothelium-dependent vasodilator through the L-arginine-nitric oxide pathway. After ischemia-reperfusion this effect is attenuated, also demonstrated in the pulmonary circulation after cardiopulmonary bypass. Administration of L-arginine has been shown to have a protective effect on endothelial function in reperfusion injury. The aim of the current study was to test the possible effect of L-arginine on the acetylcholine reactivity in the pulmonary circulation after cardiopulmonary bypass.

METHODS

Thirty-five patients with ischemic and/or valvular heart disease were investigated in a randomized, double-blinded, placebo-controlled study. The patients were divided into three groups. Group 1: high dose L-arginine (n=10), group 2: low dose L-arginine (n=10), group 3: placebo, no L-arginine, (n=15). The acetylcholine reactivity was tested with measurements of pulmonary vascular resistance before surgery and 1, 2 and 3-4 h after cardiopulmonary bypass.

RESULTS

After cardiopulmonary bypass an attenuation of the acetylcholine reactivity over time was observed in all groups, with no differences between groups.

CONCLUSION

In the current study L-arginine had no protective effect on the pulmonary endothelium after cardiopulmonary bypass, measured as reactivity to an infusion of acetylcholine.

The effect of cardiotomy suction on the brain injury marker S100beta after cardiopulmonary bypass

BACKGROUND

An increase of S100beta in serum during cardiopulmonary bypass (CPB) has been interpreted as a sign of brain injury. Cardiotomy suction may cause fat embolization, and its role in the S100beta increase was examined.

METHODS

Twenty coronary artery operation patients were randomly assigned to two groups, 10 with suction during CPB to cardiotomy reservoir (CR), 10 to cell saving device (CS). S100beta was measured (immunoassay) in blood from the patients and from cell saving device after processing. In 7 additional patients S100beta was measured in the cell saving device before processing and directly from the wound at sternotomy.

RESULTS

Before anesthesia, serum S100beta was 0.03+/-0.06 microg/L. At the end of CPB it was 2.47+/-1.31 microg/L and 0.44+/-0.27 microg/L (CR vs CS; p < 0.001). S100beta was 33+/-12 microg/L in CS reservoir and 42+/-18 microg/L in blood from the wound.

CONCLUSIONS

Most serum S100beta after CPB with cardiotomy suction may be of extracerebral origin. S100beta after CPB with cell saving device was the same as after off-pump operation. The interpretation that an increase in S100beta during CPB in patients reflects cerebral injury must be questioned.

Increased extracellular brain water after coronary artery bypass grafting is avoided by off-pump surgery

OBJECTIVE

To determine if coronary artery bypass graft (CABG) surgery without cardiopulmonary bypass (CPB) avoids the brain swelling known to occur after CPB, to quantify these brain water compartment changes, and to identify the water shifts as due to intracellular or extracellular water.

DESIGN

Prospective, controlled, and blinded.

SETTING

Cardiac surgical unit in a university teaching hospital.

SUBJECTS

Patients scheduled for CABG who were assigned to conventional (n = 10) or off-pump (n = 7) surgery according to their coronary anatomy.

INTERVENTIONS

Magnetic resonance imaging (MRI) examinations were performed 1 day before surgery and 1 hour and 1 week after CABG surgery.

MAIN OUTCOME MEASURES

Extracellular and intracellular water homeostasis was described quantitatively by calculating the averaged apparent diffusion coefficient of brain water using diffusion-weighted MRI. Blinded visual ordering of the images from the three examinations was performed according to brain size using conventional MRI.

RESULTS

The average diffusion coefficient of brain water increased 4.7%+/-1.5% immediately after CABG with CPB and normalized after 1 week but did not change after CABG without CPB. No focal ischemic changes were seen in either group, and no gross neurologic deficits were observed. Visual analysis showed consistent brain swelling after CPB and variable changes in those operated without CPB.

CONCLUSION

Changes consistent with increased extracellular brain water seen after CABG with CPB were not observed in patients undergoing CABG without CPB. The clinical significance of brain water changes and increased brain water content after surgery with CPB remains undefined.

Decreased pulmonary vascular resistance during nasal breathing: modulation by endogenous nitric oxide from the paranasal sinuses

Nitric oxide is present in high concentration in the human nasal airways. During inspiration through the nose a bolus is transported to the lungs. In a randomized cross-over study the effect of two different patterns of breathing, nasal breathing and mouth breathing, was evaluated in 10 patients (mean age 65 years), breathing room air the morning of the first post-operative day after open heart surgery. Nasal breathing is defined as inspiration through the nose and expiration through the mouth, whilst mouth breathing is the converse of this: inspiration through the mouth and expiration through the nose. Pressure in the pulmonary artery and left atrium or pulmonary artery wedge was measured together with thermodilution cardiac output and arterial and mixed venous oxygenation and acid-base parameters. Pulmonary vascular resistance index (PVRI), venous admixture and alveolar-arterial gradient were calculated. Nasal breathing resulted in a lower PVRI, 256 dyn s cm-5 cm-2 vs. 287 (P < 0.01). The oxygen and carbon dioxide tension and pH of arterial and mixed venous blood, venous admixture and the alveolar-arterial gradient remained unchanged. The decreased level of PVRI during nasal breathing compared to that during mouth breathing supports the notion, that endogenous nitric oxide acts as an airborne messenger to modulate the pulmonary vascular tone during normal breathing.

Altered reactivity to acetylcholine in the pulmonary circulation after cardiopulmonary bypass is part of reperfusion injury

STUDY OBJECTIVE

To investigate whether a time sequence of acetylcholine (ACH) reactivity indicative of endothelial reperfusion injury could be demonstrated in the pulmonary circulation in patients after cardiopulmonary bypass (CPB).

DESIGN

Prospective study.

SETTING

Operating theater and intensive care unit of a university hospital.

PATIENTS

10 ASA physical status III and IV patients with ischemic or valvular heart disease.

INTERVENTIONS

Pulmonary vascular resistance index (PVRI) was measured before and during an infusion of ACH. This procedure was done after induction of anesthesia but before surgery, immediately after weaning from bypass, and at 1 to 1.5 and 4 hours after CPB.

MEASUREMENTS AND MAIN RESULTS

ACH caused a decrease in PVRI before (p < 0.01) and directly after CPB (p < 0.05) but not at 1 to 1.5 or 4 hours after bypass.

CONCLUSIONS

The maintained reactivity to ACH directly after CPB, followed by no reaction at 1 to 1.5 and 4 hours, was in agreement with experimental findings and indicates endothelial reperfusion injury caused by the period with no blood flow through the pulmonary artery during CPB and subsequent reperfusion.

Acetylcholine reactivity in the pulmonary artery during cardiac surgery in patients with ischemic or valvular heart disease

OBJECTIVE

During cardiopulmonary bypass, there is almost no blood flow through the pulmonary artery. Ischemia and reperfusion are known to attenuate the reaction to acetylcholine. An attenuated reactivity to acetylcholine in the pulmonary circulation after cardiopulmonary bypass was previously shown in children. The current study in adult patients was designed to analyze the change over time of acetylcholine reactivity after cardiac surgery.

DESIGN

A prospective study.

SETTING

The operating room and intensive care unit of a university hospital.

PARTICIPANTS

Eighteen patients with ischemic or valvular heart disease.

INTERVENTIONS

Pulmonary vascular resistance was measured with a pulmonary artery catheter before and during an infusion of acetylcholine. This procedure was done after induction of anesthesia before surgery and 1, 4, 8, and 20 to 24 hours after cardiopulmonary bypass.

MEASUREMENTS AND MAIN RESULTS

Pulmonary vascular resistance index decreased during infusion of acetylcholine before surgery by 27% from 286 +/- 27 dyne/sec/cm-5/m2 (mean and standard error of mean) to 209 +/- 28 and at 8 and 20 to 24 hours by 23% and 34%, respectively, 288 +/- 27 to 221 +/- 29 and 229 +/- 22 to 150 +/- 17 (p < 0.001, paired t-test). One and 4 hours after cardiopulmonary bypass, no significant decrease was observed.

CONCLUSIONS

These results confirm the finding of altered reactivity to acetylcholine in the pulmonary circulation after cardiopulmonary bypass. In view of the often prolonged tendency toward pulmonary hypertension observed in children, the recovery at 8 hours after surgery was unexpectedly rapid. The attenuated response to acetylcholine is most likely explained by relative ischemia in the pulmonary circulation during cardiopulmonary bypass.

Inhalation of nasally derived nitric oxide modulates pulmonary function in humans

The vasodilator gas nitric oxide (NO) is produced in the paranasal sinuses and is excreted continuously into the nasal airways of humans. This NO will normally reach the lungs with inspiration, especially during nasal breathing. We wanted to investigate the possible effects of low-dose inhalation of NO from the nasal airways on pulmonary function. The effects of nasal and oral breathing on transcutaneous oxygen tension (tcPO2) were studied in healthy subjects. Furthermore, we also investigated whether restoring low-dose NO inhalation would influence pulmonary vascular resistance index (PVRI) and arterial oxygenation (PaO2) in intubated patients who are deprived of NO produced in the nasal airways. Thus, air derived from the patient's own nose was aspirated and led into the inhalation limb of the ventilator. In six out of eight healthy subjects tcPO2 was 10% higher during periods of nasal breathing when compared with periods of oral breathing. In six out of six long-term intubated patients PaO2 increased by 18% in response to the addition of nasal air samples. PVRI was reduced by 11% in four of 12 short-term intubated patients when nasal air was added to the inhaled air. The present study demonstrates that tcPO2 increases during nasal breathing compared with oral breathing in healthy subjects. Furthermore, in intubated patients, who are deprived of self-inhalation of endogenous NO. PaO2 increases and pulmonary vascular resistance may decrease by adding NO-containing air, derived from the patient's own nose, to the inspired air. The involvement of self-inhaled NO in the regulation of pulmonary function may represent a novel physiological principle, namely that of an enzymatically produced airborne messenger. Furthermore, our findings may help to explain one biological role of the human paranasal sinuses.

Hepatic blood flow and right ventricular function during cardiac surgery assessed by transesophageal echocardiography

OBJECTIVE

To determine the effect of cardiopulmonary bypass (CPB) on hepatic blood flow (HBF) and the hepatic venous flow pattern.

DESIGN

Single-arm prospective study.

SETTING

University hospital operating room and intensive care unit.

PARTICIPANTS

Eight patients ranging in age from 57 to 73 years undergoing cardiac surgery.

INTERVENTIONS

Transesophageal echocardiography (TEE) was used to assess HBF before, during, and after CPB by pulsed-wave Doppler ultrasound recordings of hepatic venous flow velocity and two-dimensional recordings of the hepatic vein diameter. Hepatic vein oxygenation was monitored by hepatic vein catheterization, and gastric intramucosal pH (pHi) was followed by tonometry.

MEASUREMENTS AND MAIN RESULTS

The HBF was unchanged after the start of CPB but was reduced from the baseline value 415 (standard error of the mean 40) mL/min to 225 (25) mL/min during hypothermic CPB (p < 0.05). Cardiac index, right ventricular ejection fraction, and arterial and tonometric pH were essentially unchanged during the study period. Hepatic vein and mixed venous saturation were unchanged compared to control during CPB and were reduced at 2 and 3 hours after CPB (p < 0.01). Six of the patients had a normal predominant systolic flow pattern before surgery. In the postoperative period, seven patients showed an abnormal predominant diastolic filling pattern.

CONCLUSIONS

TEE represents a useful tool in assessing changes in the hepatic blood flow. The HBF was reduced during hypothermic CPB, but this was not accompanied by a reduced pHi. The changes in the venous flow pattern with a reduction in systolic flow could be explained by impaired atrial relaxation.

Clinical estimation of left and right ventricular volume with open chest compared with transesophageal echocardiography and fast-response thermodilution

OBJECTIVE

A clinical measure--inspection of the relation of the heart (acute margin) to the diaphragm--has shown a strong positive correlation to transesophageal echocardiographic (TEE) determination of left ventricular end-diastolic area (LVEDA) during weaning from cardiopulmonary bypass (CPB). The present study examines the correlation between right ventricular end-diastolic volumes (RVEDV) before and after CPB when using the same clinical measure of left ventricular dimension.

DESIGN

Prospective study.

SETTING

Operating room, university hospital.

PARTICIPANTS

Patients scheduled for elective coronary artery bypass grafting.

INTERVENTIONS

After induction of anesthesia and endotracheal intubation, a transesophageal echo-probe was inserted. A pulmonary artery right ventricular ejection fraction/volumetric TD catheter was placed in the pulmonary artery.

MEASUREMENTS AND MAIN RESULTS

Before going on CPB, a mark was made with cautery at the line of contact between the acute margin and the diaphragm. After CPB, the patients were transfused to the same level. At these two times, TEE recordings of the LVEDA and hemodynamic measurements including calculations of RVEDV were obtained. The LVEDA before and after CPB showed a positive correlation, r = 0.81, p < 0.001. The RVEDV after CPB showed a weak correlation, r = 0.54, p < 0.05, to RVEDV before CPB. There were no significant changes in right ventricular (RV) wall tension calculated as right atrial pressure x RVEDV and pulmonary artery systolic pressure x right ventricular end-systolic volume products. The only significant change regarding hemodynamic parameters was a decrease in mean arterial pressure.

CONCLUSIONS

It is concluded that there is only a weak correlation regarding RVEDV before and after CPB when the patient is transfused to the line of contact, whereas this clinical measure correlates well with LVEDA.

Dopexamine and dopamine in the prevention of low gastric mucosal pH following cardiopulmonary by-pass

The effect of low-dose dopexamine and dopamine on gastric intramucosal pH (pHi) during cardiac surgery and 16 hours postoperatively was studied in 35 adults patients (coronary artery bypass grafting and/or valve replacement). The patients were assigned randomly to treatment groups with either dopexamine (1 microgram.kg-1.min-1 (n = 12), dopamine 2.5 micrograms.kg-1.min-1 (n = 11) or to a control group (n = 12). The infusions were started after induction of anaesthesia and were continued until 16 hours after CPB. pHi and arterial pH (pHa) did not differ between groups and remained unchanged during cardiopulmonary by-pass and for the first four postoperative hours. Both the carbon dioxide tension of arterial blood (PaCO2) and of the saline in the tonometer (PtonCO2) changed in parallel with a decrease during CPB and an increase after CPB and surgery with maximal values 12 hours after termination of CPB. A significant correlation was noted between pHi and pHa and between arterial and tonometric PCO2. It is concluded that low dose dopexamine and dopamine have no influence on pHi during and after cardiac surgery. The observed changes in pHi and PtonCO2 were due to changes in pHa and in PaCO2 and not a sign of gastric mucosal ischemia.

Effect of dopexamine on calculated low gastric intramucosal pH following valve replacement

Gastric tonometry was used to study the possible effect of dopexamine infusion on a low calculated intramucosal pH (pHi) as a sign of splanchnic ischemia. Measurements were made during surgery and for approximately 18 hours postoperatively on 19 non-selected adult patients undergoing valve replacement. Patients developing a postoperative pHi > 7.30 were randomized to receive dopexamine (2 micrograms.kg-1 min-1) or placebo in a double blind fashion. Eighteen patients were randomized, 10 to receive dopexamine and 8 to placebo. The calculated pHi remained unchanged for the first 2 hours in both groups. After 4 hours a significant (P < 0.05) decrease in pHi was noted in the dopexamine group which remained significantly below the placebo group during the monitoring period. The dopexamine treated patients had a significantly longer period of low pHi but the pH-gap i.e. the difference between arterial pH and pHi did not differ between the two groups. Patients with postoperative complications, defined as infections (2), myocardial infarction (1), single- (2) or multiple organ failure and death (1), did not have longer periods with pHi below 7.30. In these patients, however, a pH-gap > 0.12 occurred more often than in those without complications, indicating that an increased incidence of complications was related to a pH-gap > 0.12. It is our opinion that true mucosal ischemia is best detected by estimating the difference in carbon dioxide tension between arterial blood and mucosa. This can be expressed either directly as PCO2-gap (PtonCO2-PaCO2) or indirectly as pH-gap.

Comparison between transesophageal Doppler echocardiography and nuclear cardioangiography for the evaluation of left ventricular filling during coronary artery bypass grafting

This study examines the relative contribution of early (E) and atrial (A) filling of the left ventricle. Ten patients were studied under anesthesia before and after coronary artery bypass grafting (CABG) using measurements of the mitral velocity-time integral (VTI) with transesophageal pulsed Doppler echocardiography and nuclear angiocardiography simultaneously. Thermodilution cardiac output measurements were made simultaneously in order to express the E and A filling in quantitative terms. The mean difference between methods in estimating E filling was -1.0 mL and the figures for the mean +/- 2 SD were 5.7 and -7.8 mL, r = 0.98 using regression analysis. The mean difference during A filling was 0.9 mL and the corresponding figures for the mean +/- 2 SD were 7.9 and -6.1 mL, r = 0.88. There was a reduction in the volume entering the left ventricle during the E filling (42-26 mL) and in the A phase (27-22 mL) from before surgery in comparison to after CABG. There was good agreement between transesophageal Doppler echocardiographic and nuclear angiocardiographic methods concerning the volume contribution during E and A phases of left ventricular filling.

Changes in left ventricular diameter during intravenous induction of anesthesia

Transthoracic two-dimensional echocardiography was used to measure left ventricular diameter in end-systole and end-diastole during anesthetic induction in 11 patients before coronary artery bypass grafting. Midazolam, 0.1 mg/kg, and fentanyl, 6 to 10 micrograms/kg, were used followed by pancuronium, 0.1 mg/kg. Lidocaine, 1.5 mg/kg, was given topically in the airways before intubation. During induction of anesthesia there was a gradual decrease in diastolic diameter (preload) and in systolic diameter and pressure (afterload). The decrease in end-diastolic diameter from 4.6 cm to 3.9 cm indicated a decrease in preload, defined as end-diastolic volume, by approximately 34%. These results are in agreement with earlier findings using calculated ventricular volumes, based on the determination of either ejection fraction with radionuclide cardiography or stroke volume with thermodilution, during induction of anesthesia with thiopental, diazepam, fentanyl, and pancuronium.

Comparison of clinical and echocardiographic determinations of left ventricular dimension during weaning from cardiopulmonary bypass

Twenty patients (age 45 to 78 years) were studied with ethical committee approval and informed patient consent during coronary artery bypass grafting. Transesophageal echocardiography (TEE) was used to validate a clinical measure of preload: inspection of the line of contact between the heart (acute margin) and the diaphragm. Immediately before going on cardiopulmonary bypass (CPB), with the cannulas and stay sutures in place, a small mark was made with the cautery on the diaphragm at the line of contact. After CPB the patients were transfused from the extracorporeal circuit to exactly the same level. At these two times, TEE recordings of the short axis of the left ventricle were performed and stored on videotape for later blinded evaluation off-line. The left ventricle short-axis area in end-diastole measured after CPB showed a close correlation to that measured before CPB, r = 0.88, P < 0.001. The regression line was close to the line of identity. The conclusion was that inspection of the line of contact between the heart and the diaphragm can be used clinically during weaning from bypass to obtain the same left ventricular end-diastolic volume as before CPB.

Influence of glucose-insulin-potassium on left ventricular function during coronary artery bypass grafting

To evaluate the hemodynamic effect of glucose-insulin-potassium administered during cardiopulmonary bypass grafting (CABG), i.v. infusion of glucose 0.5 g, insulin 1.35 IU and potassium 0.25 mmol/kg b.w/hour was begun after induction of anesthesia and continued until aortic cross-clamping in seven patients. Seven controls underwent CABG without such infusion. The left ventricular ejection fraction was measured after i.v. injection of Tc-99m-HSA before and at termination of cardiopulmonary bypass (CPB), in conjunction with invasive measurements to obtain left ventricular pressure-volume indices at end-systole and end-diastole. Three-step transfusion from the oxygenator was given before and after CPB in order to assess left ventricular contractility during volume-load, using the end-systolic pressure-volume index. Left ventricular contractility remained unchanged after CPB in the patients given glucose-insulin-potassium but decreased significantly in the controls. The left ventricular passive diastolic properties were unchanged after the ischemic period in both groups. The arterial glucose concentration rose markedly in the infused group (7.3-18.5 mmol/l) and moderately (6.4-8.2) in the controls. Glucose-insulin-potassium infusion thus favorably influenced left ventricular function during CABG by preventing decrease in contractility after CPB.

Incidence of sore throat and patient complaints after intraoperative transesophageal echocardiography during cardiac surgery

To evaluate the incidence of postoperative side effects and patient complaints following transesophageal echocardiography (TEE), 57 patients were interviewed by questionnaire and examined by pharyngeal inspection, preoperatively. The patients were randomized to undergo surgery with or without intraoperative TEE, and a second interview and examination were performed in 48 patients on the second postoperative day using a double-blind protocol. Twenty-four of the patients were investigated by TEE over a period of 5.4 +/- 2.3 hours and 24 had surgery without TEE. The intubation time for the two groups did not differ. There was no difference between controls and TEE patients with regard to painful swallowing evaluated by a visual analog scale. Furthermore, there was no difference between the controls and TEE patients regarding nausea or time elapsed from extubation to the first oral intake. No differences between the groups were found regarding the findings on pharyngeal inspection and no major complication attributable to the use of TEE occurred. A sore throat with painful swallowing was not a great problem for the patients in the present study; this indicates that endotracheal intubation rather than TEE caused the minor complaints. It is concluded that intraoperative TEE can be used without harmful postoperative pharyngeal side effects.

Left ventricular end-systolic pressure estimated from measurements in a peripheral artery

Aortic and radial arterial pressure measurements were compared after cannulation and before cardiopulmonary bypass in 26 patients scheduled for coronary artery bypass grafting. The radial artery blood pressure range was 89 to 147 mm Hg systolic and 44 to 75 mm Hg diastolic. A difference was found between the central and peripheral dicrotic notch pressures, the former being 7.9 +/- 2.7 (SD) mm Hg higher than the latter. When 8 mm Hg was added to the notch pressure measured in the radial artery to construct a calculated end-systolic pressure, there was good agreement with the centrally measured notch pressure. The mean difference was -0.15 mm Hg with a 95% confidence interval of -1.2 to 0.9 mm Hg. It was not possible to calculate peak systolic aortic pressure with the same accuracy from the systolic and diastolic pressure measurements in the radial artery. It is concluded that left ventricular end-systolic pressure measured as the aortic dicrotic notch pressure can be calculated from the dicrotic notch pressure in the radial artery with reasonable accuracy.

A comparative study of five different techniques to reduce left ventricular dysfunction during endotracheal intubation

Thirty-five non-selected, consenting patients were studied during induction of anesthesia before coronary artery bypass grafting. Anesthesia was induced with diazepam, thiopentone and fentanyl, followed by pancuronium. Before induction, 200 MBq Tc 99 m - HSA was given i.v. and ejection fraction (EF) of the left ventricle was measured with a collimated single-crystal probe. The patients were allocated to five groups (seven patients in each) treated with: Group A: nitroglycerin i.v. bolus 4 micrograms x kg-1 given 30-60 s before laryngoscopy; Group B: nitroglycerin i.v. in continuous infusion, 1 micrograms x kg-1 x min-1 started before induction; Group C: two-stage topical anesthesia of the vallecula region and larynx with lidocain; Group D: a combination of nitroglycerin and topical anesthesia (as in Group B and C); and Group E: propranolol i.v. 0.01 mg x kg-1 given 5 min before intubation. All groups reacted in the same way during induction of anesthesia up to the point of laryngoscopy. End-diastolic volume and systemic arterial pressure decreased while cardiac index remained unchanged and EF increased. During laryngoscopy and intubation, however, differences between the groups were evident. Nitroglycerin i.v. as a bolus effectively prevented a reduction in EF and an increase in left ventricular volume. In addition to these beneficial hemodynamic effects, there was a moderate increase in heart rate and a reduction of stroke index. Continuous infusion of nitroglycerin and propranolol i.v. had no effect, since EF fell and left ventricular volume increased. Patients receiving topical anesthesia demonstrated a blunted response to endotracheal intubation with a moderate decrease in EF and an unchanged (Group C) or slightly increased (Group D) left ventricular volume.

Release of neuropeptide Y and noradrenaline from the human heart after aortic occlusion during coronary artery surgery

STUDY OBJECTIVE

The aim was to study the influence of complete myocardial ischaemia during aortic occlusion on release of neuropeptide Y and noradrenaline from the human myocardium.

DESIGN

Coronary sinus neuropeptide Y and noradrenaline were measured after 46(SEM 7) min of aortic occlusion with cold cardioplegia in patients undergoing coronary artery surgery. Patients - Seven patients (all male), aged 64(SEM 3) years, were studied. All were undergoing coronary artery bypass grafting.

MEASUREMENTS AND MAIN RESULTS

Reperfusion was associated with an increase in coronary sinus blood flow as determined by thermodilution. Simultaneously there was cardiac release of both neuropeptide Y and noradrenaline during the first two sampling periods: 3(0.6) and 7(0.6) min after the start of reperfusion. The outflow of neuropeptide Y and noradrenaline returned to preischaemic values by 14(1) min after reperfusion. Coronary sinus blood lactate and pyruvate concentrations were also increased at the start of reperfusion, while the lactate/pyruvate ratio remained unchanged. Myocardial oxygen uptake was not influenced by cardiac ischaemia.

CONCLUSIONS

Ischaemia of the human heart in vivo is associated with an enhanced outflow of neuropeptide Y and noradrenaline from the heart. Since arterial blood concentrations of these substances were also increased on reperfusion, their release is probably due to increased sympathetic nerve activity, though other mechanisms such as temperature change and local metabolite formation could also participate. Local release of neuropeptide Y during cardiac ischaemia may be involved in the regulation of coronary vascular tone as well as in the release of noradrenaline and acetylcholine.

The effect of arterial pH on whole body oxygen uptake during hypothermic cardiopulmonary bypass in man

To test the hypothesis of Rahn and Reeves that the optimal arterial pH during hypothermia follows the alpha-stat concept, we studied 50 patients during coronary artery bypass grafting or valve replacement (or both) and aortic occlusion. Intravenous anesthesia was produced by high-dose fentanyl. Thiopentone 3 mg.kg-1 body weight and pancuronium 0.1 mg.kg-1 body weight were given at the start of cardiopulmonary bypass to prevent shivering. When the temperature of venous blood reached 25 degrees C, pump flow was reduced to 1.8 L.m-2.min-1. In 17 patients (group I), arterial pH was changed in a randomized order either from high to low or from low to high by adjusting the carbon dioxide fraction of the gas flow to the bubble oxygenator. At the end of 10-minute periods with stable arterial pH, oxygen uptake was calculated by multiplying pump flow and the arteriovenous oxygen difference. In 33 other patients (group II), arterial pH was kept constant during the period of stable hypothermia at 25 degrees C, and two to five determinations of oxygen uptake were performed in each patient. The carbon dioxide fraction in the gas and arterial pH varied between the patients. In group I, oxygen uptake was 31.4 ml.m-2.min-1 at pH 7.31 and 40.3 ml.m-2.min-1 at pH 7.52-a significant difference (p less than 0.001). In group II, oxygen uptake was positively correlated to arterial pH (r = 0.52, p less than 0.01). Thus the results were in line with the alpha-stat concept of acid-base management during hypothermia.

Isoflurane and intravenous anesthesia used for induction before coronary artery bypass grafting

Induction of anesthesia with isoflurane in combination with fentanyl, thiopentone, nitrous oxide and pancuronium was studied in nine patients scheduled for coronary artery bypass grafting. Ejection fraction (EF) of the left ventricle was monitored with a single crystal probe linked to a microcomputer, after injection of 200 MBq Tc 99m-HSA. Stroke volume index determined by thermodilution and EF were used to calculate left ventricular end-diastolic volume index (LVEDVI). The degree of ischemia was numerically scored as evaluated from the ECG (modified V5 lead). The study protocol covered seven periods from awake before induction to 5 min after intubation. EF decreased moderately during intubation (P less than 0.05). Systemic vascular resistance index (SVRI) was decreased (P less than 0.05) at all times except during intubation when it was unchanged compared to control. LVEDVI decreased during induction (P less than 0.05), while left ventricular filing pressure remained unchanged. Heart rate did not change. Systolic arterial pressure decreased from 147 mmHg (19.6 kPa) to about 100 mmHg (13.3 kPa) during induction (P less than 0.05). Two patients were given vasoconstrictors because of low arterial pressure. The mean ischemic score did not change. One patient, however, had signs of progressive ischemia. In this patient isoflurane administration was stopped after the last recording and the ECG normalized within 20 min.

Changes in ejection fraction during induction of anesthesia with two different i.v. techniques

Two intravenous induction techniques were compared with respect to changes in ejection fraction (EF) and central hemodynamics in 30 patients scheduled for coronary artery surgery. Left ventricular EF was measured with a collimated single crystal probe linked to a microcomputer, after injection of 200 MBq Tc 99 m HSA. Stroke volume index (SI) determined by thermodilution and EF were used to calculate left ventricular volume in end-systole and end-diastole. In 20 patients (Group I), anesthesia was induced with diazepam (94 micrograms x kg-1), thiopentone (3 mg x kg-1) and fentanyl (3 micrograms x kg-1). In 10 patients (Group II), fentanyl (30 micrograms x kg-1) was used for induction. In Group I, EF decreased from 0.43 to 0.26 at intubation, while systemic vascular resistance index (SVRI) showed an increase. Left ventricular volume decreased during induction of anesthesia except during intubation. In Group II, EF and left ventricular volume remained unchanged during the study period. SVRI showed no increase at intubation. No change in contractility was indicated from the relation between the end-systolic pressure and volume, in any of the groups.

The calculation of left ventricular stroke work index

The relation between left ventricular mean systolic pressure (LVSP) determined by planimetric integration and systolic and diastolic pressure measured in a peripheral artery (SAP and DAP) was calculated using data published by Ross & Braunwald in 1964. The relation was LVSP = SAP-0.32 +/- 0.06 (s.d.) X (SAP-DAP). The formula SAP- 0.32 (SAP-DAP) was used to calculated LVSP, and the correlation between measured and calculated LVSP was found to be 0.91 (P less than 0.001). It is concluded that LVSP can be calculated with reasonable accuracy from measurements of arterial pressure in patients without aortic stenosis. At present three different formulas are in use for the calculation of left ventricular stroke work index (LVSWI). The pressure work is defined as SAP, LVSP or mean arterial pressure minus mean pulmonary capillary wedge pressure or left ventricular end diastolic pressure. This makes comparisons between different studies with respect to LVSWI difficult or impossible.

The influence of isoflurane on blood flow in coronary bypass grafts

The effects of isoflurane on graft blood flow, central hemodynamics and ECG were evaluated in 20 patients during coronary artery surgery in the period immediately after cardiopulmonary bypass (CPB). Intravenous anesthesia with thiopentone, diazepam, fentanyl (continuous infusion), droperidol and pancuronium supplemented with nitrous oxide was used before, and thiopentone and fentanyl were used during CPB. A first measurement of graft flow was performed during fentanyl infusion and the patients were randomly allocated to a control (n = 10) and a study (n = 10) group. In the study group isoflurane was administered in a dose that reduced systolic arterial blood pressure (SAP) to approximately 100 mmHg (13.3 kPa) (inspired concentration 0.5-1.5%) and a second measurement was performed after 30 min. In the control group the infusion of fentanyl was continued. Isoflurane reduced graft blood flow from 52 +/- 5 (mean and s.e. mean) to 40 +/- 5 ml . min-1 (P less than 0.01) concomitant with reductions in SAP, cardiac index, stroke index, left ventricular stroke work index and power index, while these parameters as well as graft flow remained unchanged in the control group. Isoflurane did not produce any change in the degree of ischemia as judged from the ECG. A high blood flow in recently established coronary artery bypass grafts is essential for the prevention of early graft occlusion; therefore the graft-flow-reducing effect of isoflurane has to be taken into consideration when evaluating different anesthetic regimens in the period after CPB.

Effects of intravenous anesthesia on VA/Q distribution: a study performed during ventilation with air and with 50% oxygen, supine and in the lateral position

Distribution of ventilation and perfusion in relation to ventilation-perfusion ratio (VA/Q) were studied in 14 patients, with a mean age of 59 yr, before elective lung surgery, in the supine position when awake, during intravenous anesthesia and mechanical ventilation with air, after increasing the fraction of inspired oxygen (FIO2) to 0.5, and in the lateral position. Before anesthesia, small inert gas shunts and perfusion of low VA/Q regions, indicating some degree of VA/Q mismatch, were observed in several patients. After induction, FIO2 = 0.21, the major changes were a significant decrease in cardiac output and an increase in log SD for perfusion from 0.77 +/- 0.45 (SD) to 1.13 +/- 0.50 (SD), while the shunt remained low at 1% of cardiac output and arterial oxygen tension (PaO2) was unchanged. An increase to FIO2 = 0.5 induced only small changes with a shunt of 2.5% of cardiac output. In the lateral position, the shunt was 4.0% and increases in ventilation to high VA/Q regions were observed. The lack of marked changes in the VA/Q distribution after induction either could be a result of only minor alterations in the distribution of ventilation and perfusion or an effective vascular response to alveolar hypoxia (hypoxic pulmonary vasoconstriction, HPV).

Comparison of fentanyl and halothane as supplement to nitrous-oxide-oxygen anaesthesia for coronary artery surgery

Twenty unselected patients suffering from incapacitating angina, in spite of medication with nitrates, beta-blockers and calcium antagonists, were studied before and during coronary artery bypass surgery. Fentanyl or halothane was randomly used in combination with nitrous oxide for maintenance of anaesthesia in order to compare the haemodynamic response to surgery and cardiopulmonary bypass with these two anaesthetic regimens. Systemic and pulmonary artery pressure were kept within normal limits with the aid of volume replacement and/or nitroprusside. The haemodynamic response to surgery and bypass was benign and almost identical in the two groups. Cardiac index increased markedly after bypass (P less than 0.02-0.001) from 2.0 to 3.0 1 X min-1 X m-2 due to an increase in heart rate with no change in stroke index (40 ml X m-2). Oxygen delivery remained unchanged at 17 mmol X min-1 X m-2 in spite of a marked reduction in blood erythrocyte volume fraction (B-EVF), from 38% before bypass to 24% after bypass (P less than 0.001). Oxygen uptake remained unchanged until the end of surgery and did not differ between the groups. Systemic vascular resistance, corrected for the change in viscosity due to the altered B-EVF, was unchanged during the study. No difference was observed between the groups in the relation between pulmonary artery diastolic pressure and left ventricular stroke work index or stroke index, either before or at the end of cardiopulmonary bypass when the patients were transfused from the oxygenator.

Adenosine spares platelets during cardiopulmonary bypass in man without causing systemic vasodilatation

The effect of infusing adenosine during cardiopulmonary bypass (CPB) on platelet count and mean arterial blood pressure (MABP) was studied in 13 patients (age 42-74), with 12 patients (age 47-66) as controls. Adenosine infusion (0.1 mg/kg/min in a central vein) caused a ten- to twentyfold increase of the adenosine concentration in the venous blood to the oxygenator, while the arterial levels were close to basal values (0.3 +/- 0.1 microM). The platelet count was significantly higher in the treated than in the placebo group during and 30 min after CPB, but not on the postoperative day. The groups did not differ with regard to the postoperative blood loss from tube drainage. Adenosine did not cause major systemic vasodilation (MABP less than 30 mmHg) in any case, and the blood pressure levels showed no intergroup difference during CPB. However, seven control patients but none in the adenosine group required vasodilator treatment (sodium nitroprusside) during CPB to prevent MABP from exceeding 70 mmHg. We conclude that adenosine infusion during CPB in man spares platelets, with minor changes in blood pressure.

Sequential myocardial depressant and non-depressant anaesthesia for coronary artery surgery

Patients undergoing coronary artery surgery run a certain risk of developing myocardial infarction in situations with increased myocardial oxygen demand due to e.g. elevations in heart rate and blood pressure. After cardiopulmonary bypass (CPB) there is, however, also the risk of graft occlusion. The present study evaluated the haemodynamic effects of a sequential anaesthesiological technique using halothane 0.5-1.5% in combination with 50% nitrous oxide and droperidol 0.1 mg X kg b.w.-1 before CPB followed by fentanyl 0.2 mg X h-1 in continuous i.v. infusion and diazepam 10-15 mg during and after bypass. Fourteen patients were studied. In seven patients (Group I) halothane was discontinued immediately before CPB and in the following seven patients (Group II) 10-15 min before bypass. The aim was to depress moderately the inotropic state before bypass and to have a normalized myocardial oxygen demand after CPB in order to promote a good flow in the grafts. In Group II mean left ventricular stroke work index (LVSWI) was 0.54-0.79 J X m-2 after bypass as compared to 0.45-0.51 before at comparable filling pressure. Mean left ventricular power index (LVPI) increased from 0.42-0.55 W X m-2 before to 0.73-1.08 after CPB. The patients in Group I showed a similar pattern although with a less marked difference in LVSWI and LVPI values before and after bypass. No correlation was seen between oxygen delivery and oxygen uptake either below or above an oxygen delivery of 15 mmol X min-1 X m-2.