The cardiovascular effects of neuroleptanaesthesia

The effects of general anaesthesia on oxygen consumption: A meta-analysis guiding future studies on perioperative oxygen transport

BACKGROUND

Increased oxygen extraction, the ratio of consumption to delivery, has been associated with poor outcome after surgery. Oxygen consumption (VO2) can change in several ways in the perioperative period, but is seldom monitored directly in routine care. This study investigates the effects of general anaesthesia on VO2.

METHODS

We searched PubMed, EMBASE, and Cochrane Library 1946-2018 for studies including VO2 measurements before and after anaesthesia induction. Quality was assessed by Cochrane risk of bias tool and NIH Quality Assessment tool for before-and-after studies. Changes in VO2 after anaesthesia induction were pooled in a random effects model meta-analysis with standardized mean differences transformed to absolute changes of VO2. Changes in VO2 after surgical incision and after recovery from anaesthesia were analysed as secondary outcomes in the included studies.

RESULTS

Twenty-four studies including 453 patients were analysed for VO2 changes induced by anaesthesia. Studies were published during 1969-2000 and mean age of patients ranged 28-70 years. VO2 decreased after anaesthesia induction by -65 (-75; -55, 95% CI) mL min^-1 and indexed VO2 (VO2I) by -33 (-38; -28, 95% CI) mL min^-1  m^-2 . After surgical incision and in the post-operative period VO2 increased again. Heterogeneity was considerable among the studies and the overall quality of evidence was very low.

CONCLUSIONS

General anaesthesia probably reduces oxygen consumption but the effect estimate is uncertain. Given the limited generalizability and low quality of the available evidence, new studies in modern perioperative settings and in today's older high-risk surgical patient populations are needed.

Hemodynamic and catecholamine response to isoflurane versus droperidol in complement to fentanyl anaesthesia

Droperidol (0.03 mg.kg-1 to 0.25 mg.kg-1) with fentanyl has been reported to be less efficient than volatile agents in the prevention of haemodynamic responses to surgery. The aim of this study was to investigate the use of high-dose droperidol in complement to fentanyl in comparison with isoflurane and fentanyl anaesthesia. Thirty patients undergoing laryngectomy were studied. Systolic blood pressure (SBP), heart rate (HR) and plasma catecholamines were analysed both during anaesthesia and during recovery. During surgery, SBP epinephrine (E) levels did not change in either group. HR was slightly lower during droperidol fentanyl anaesthesia. Norepinephrine (NE) levels were significantly higher in the droperidol group than in the isoflurane group (P less than 0.05). During recovery, in both groups, SBP increased by 20% whereas E levels increased by 65%. NE levels increased post-operatively in both groups, but this rise was significantly higher in the droperidol group (P less than 0.01). It is concluded that the two techniques contribute to the haemodynamic stability during surgery, but do not prevent haemodynamic instability during recovery.

Neuroleptanesthesia versus thoracic epidural anesthesia for abdominal aortic surgery

The hemodynamic consequences of abdominal aortic surgery with infrarenal cross-clamping were studied in 21 patients randomized in two groups. In Group I (11 patients), neuroleptanesthesia was utilized, while Group II (10 patients) received thoracic epidural anesthesia at the T8-9 level. Hemodynamic measurements were performed using Swan-Ganz catheters during the surgical procedures in all patients, with special attention to the periods of clamping and unclamping of the abdominal aorta. The thoracic epidural anesthesia group was characterized by greater hemodynamic stability during surgery, while patients in the neuroleptanesthesia group had significant lability of blood pressure, heart rate, and cardiac index. Nevertheless, in the two groups of patients, it is suggested that cardiac function was unfitted to the tissue oxygen demand after unclamping of the aortic prosthesis because the saturation in oxygen of the mixed venous blood and an increase in arteriovenous difference in oxygen were documented. These results point out that, whatever the anesthesia technique, the critical period in abdominal surgery could be aortic unclamping.

Oxygen uptake and central circulation during ketamine anaesthesia

Cardiac output, oxygen uptake and plasma catecholamines were studied in patients when awake and during ketamine anaesthesia prior to and during upper abdominal surgery. Oxygen uptake was determined by using a masspectrometer and cardiac output was measured according to the Fick principle. Plasma catecholamines were analysed by high performance liquid chromatography. Stroke volume had fallen by 27% while heart rate had increased after 15 min of anaesthesia, maintaining cardiac output at the awake level. Concomitantly, the oxygen uptake had fallen by 18%. During the succeeding hour of anaesthesia and surgery, cardiac output displayed a transient decrease and oxygen uptake returned to the awake value. The plasma adrenaline concentration fell during the initial phase of anaesthesia and then returned to the awake level. The noradrenaline concentration was increased during the whole anesthetic period. The data suggest a relationship between oxygen uptake and cardiac output during ketamine anaesthesia, similar to that seen during neurolept-nitrous oxide and halothane anaesthesia, except for the initial hyperkinetic period following the induction. No relationship could be shown between catecholamine concentrations in plasma and the central haemodynamics.

Haemodynamic effects of calcium chloride administered intravenously to patients with and without cardiac disease during neurolept anaesthesia

During neurolept anaesthesia, calcium chloride (15 mg/kg) was administered intravenously to two different groups of patients undergoing vascular surgery on the abdominal aorta. The patients in group I all suffered from cardiac disease and were treated with digoxin, while the patients in group II had no cardiac symptoms. Cardiovascular measurements were made during steady-state anaesthesia. In group I, CaCl2 increased cardiac index (CI) significantly while systemic vascular resistance index (SVRI) remained unchanged. Mean arterial pressure (MAP) increased. In group II, both MAP and SVRI increased while CI remained unchanged. No significant changes in heart rate were observed and no arrhythmias occurred. It is concluded that CaCl2 administered intravenously is an effective means of improving cardiac function when it is depressed by anaesthesia, underlying cardiac disease, or both.

Oxygen uptake, plasma catecholamines and cardiac output during neurolept-nitrous oxide and halothane anaesthesias

Cardiac output, oxygen uptake and plasma catecholamines were studied in patients both awake and during anaesthesia prior to and during upper abdominal surgery. Two different forms of anaesthesia were used: neurolept-nitrous oxide (NLA) and halothane (HALO) anaesthesia. Oxygen uptake was determined by using a masspectrometer, and cardiac output was measured according to the Fick principle. Plasma catecholamines were analysed by high performance liquid chromatography. Cardiac output fell by 40% during NLA and by 30% during HALO. Concomitantly, the oxygen uptake fell by 40% and 35%, respectively. A linear relationship between cardiac output and oxygen uptake could be established both in the awake state and during anaesthesia, with no significant change in the slope or position of the regression line when anaesthesia was commenced. Ventricular filling pressures fell during both anaesthetic procedures. Adrenaline fell to half the plasma concentrations seen in normal subjects under resting conditions, while noradrenaline returned to normal from an initially 30-40% increased value. Surgery caused no significant changes in either cardiac output or oxygen uptake, whereas plasma adrenaline increased by 20 times and noradrenaline by 60-90%. The findings suggest that the reduced oxygen uptake during anaesthesia causes the fall in cardiac output rather than any cardiodepressant action of the anaesthetic. It is possible that the anaesthetic depresses whole-body metabolism by either blocking the effects of catecholamines or interfering with cellular metabolism.

Central haemodynamics during halothane and enflurane anaesthesia in vascular surgery

Central haemodynamics were studied before and during reconstructive vascular surgery in 18 patients receiving halothane or enflurane anaesthesia (nine patients in each group). In both groups cardiac output (CO), stroke volume (SV), oxygen uptake (VO2) and arterial blood pressure fell significantly after induction of anaesthesia, whereas the arterio-venous oxygen difference (AVD) and the total peripheral resistance (TPR) remained unchanged. In spite of an average intraoperative blood loss of 600 ml, which had not been substituted for, surgery brought about an increase in CO, SV and VO2, while the AVD and TPR remained unchanged. Following transfusion of 900 ml of blood, CO and SV showed a further significant increase in both groups, whereas VO2 was unchanged and the AVD and TPR fell significantly. The pulmonary capillary venous pressure (PPCV) was stable during induction of anaesthesia and surgery but increased after blood transfusion. The changes in SV and PPCV were analyzed in relation to the concept of ventricular function curves. It is concluded that there were no fundamental differences in central haemodynamics between halothane and enflurane anaesthesia either before or during surgery. In both groups the changes in CO and SV were due mainly to a reduced demand of oxygen transport and expected changes in sympatho-adrenergic tone rather than to myocardial depression.

Hemodynamics following normovolemic hemodilution in elderly patients

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

Thyroid blood flow rate in man. Electromagnetic flowmetry during operation in euthyroid normal gland, nontoxic goiter, and hyperthyroidism

Human thyroid blood flow rate (TBF) was measured during operations by electromagnetic flowmetry in 75 euthyroid patients with normal thyroid tissue, nodular goiter, or solitary adenoma, and in 22 hyperthyroid patients with diffuse or nodular goiter. Blood flow rate was measured in one to four of the thyroid arteries. No difference in blood flow rate was seen between the left and right lobes. The slight difference found between the inferior and superior arteries was not significant. In each subject, total TBF was calculated as 4 times the mean of the recorded blood flow in the single arteries. The total TBF was 31 (9-109) ml/min (inner 95 percentile range) in euthyroid patients, similar in all 3 groups. This is less than in most earlier reports. The relative TBF was 1.2 (0.4-3.8) ml/min/g thyroid tissue in normal thyroid tissue and 0.6 (0.1-3.7) ml/min/g in nontoxic nodular goiter (p less than 0.01). Patients with hyperthyroidism had a higher total TBF 54 (15-197) ml/Min (p less than 0.001), despite preoperative treatment giving euthyroidism, Similar TBF rates were found in 3 hyperthyroid patients given propranolol preoperatively. Electromagnetic flowmetry is applicable to study thyroid blood flow rate. Human TBF shows considerable interindividual variations, which must be kept in mind when studying directly the rate of thyroid hormone secretion from arteriovenous gradients.

Myocardial oxygen consumption and coronary haemodynamics during fentanyl-droperidol-nitrous oxide anaesthesia in patients with ischaemic heart disease

Eight patients with stable ischaemic heart disease were investigated to determine the effects of fentanyl (15 micrograms/kg) - droperidol (150 micrograms/kg) - nitrous oxide (75%) anaesthesia, without concomitant fluid challenge, on myocardial oxygen consumption and lactate uptake, and central and coronary haemodynamics. Anaesthesia induced reductions in mean arterial pressure (--35%, P less than 0.01), systemic vascular resistance (--30%, P less than 0.01), left ventricular stroke work index (--50%, P less than 0.01) and total body oxygen consumption (--23%, P less than 0.01), with no changes in heart rate, cardiac output or mean pulmonary arteriolar occlusion pressure. Mixed venous oxygen content increased (P less than 0.05). Systemic vasodilatation, circulatory adaptation to an overall lower metabolic rate, and clinically negligible cardiodepression are the likely mechanisms behind the central haemodynamic response to this form of anaesthesia. Coronary sinus blood flow (measured by the continuous thermodilution technique) decreased (P less than 0.01) in parallel with the decrease in coronary perfusion pressure. Thus coronary vascular resistance remained unchanged. As expected from the haemodynamic findings, myocardial oxygen consumption decreased (--37%, P less than 0.01). Coronary sinus oxygen content and myocardial oxygen extraction did not change, nor was myocardial lactate uptake affected. No ST-T-segment depressions or dysrhythmias were recorded. These observations indicate that myocardial oxygenation was adequate in spite of the reduction in coronary perfusion pressure. There was poor correlation between changes in myocardial oxygen consumption and rate pressure product (R = 0.455) or triple produce (R - 0.375).

Cardiovascular effects of sodium nitroprusside in cerebral aneurysm surgery

Cardiovascular effects of sodium nitroprusside (SNP) were studied in 17 patients undergoing cerebral aneurysm surgery under controlled hypotension. In 10 patients oxygen uptake was also calculated. Mean arterial blood pressure was decreased from 91 to 58 mmHg by SNP due to reductions in both total peripheral resistance (29%) and cardiac output (15%). Mean right atrial and pulmonary capillary wedge pressures were reduced during hypotension. Total oxygen uptake remained constant throughout the procedure. There was no significant change in arterial oxygen tension in the hypotensive period, but after discontinuation of SNP infusion it was significantly increased. The haemodynamic effects of SNP in patients with a recent subarachnoid haemorrhage and its effect on blood oxygenation are discussed. It is concluded that the fall in cardiac output is related to a reduction of central blood volume and might be more pronounced in these patients than in normal subjects.

Haemodynamic and biochemical variables after induction of anaesthesia with fentanyl and nitrous oxide in patients undergoing coronary artery by-pass surgery

The effects on the haemodynamic and biochemical parameters of three different anaesthetic induction regimes, namely fentanyl (4.1 micrograms.kg-1 or 15 micrograms.kg-1) plus 60 per cent nitrous oxide with oxygen and fentanyl 15 micrograms.kg-1 plus 60 per cent nitrogen with oxygen, were studied in patients undergoing coronary artery surgery. Fentanyl 15 micrograms.kg-1 with nitrous oxide and oxygen produced simultaneous reductions in oxygen uptake, cardiac index and left ventricular stroke work with an unaltered oxygen extraction. Diastolic blood pressure (an index of coronary artery perfusion) was only slightly reduced, and there were no changes in arterial lactate, glucose and free fatty acids. The lower dose of fentanyl (4.1 micrograms.kg-1) with nitrous oxide produced no haemodynamic changes but decreased the oxygen uptake and extraction. The patients receiving fentanyl 15 micrograms.kg-1 with nitrogen and oxygen showed increases in heart rate, blood pressure, cardiac index and left ventricular stroke work, together with a significant fall in oxygen extraction. Moreover, in the patients who received fentanyl 4.1 micrograms.kg-1 with nitrous oxide and oxygen and fentanyl 15 micrograms.kg-1 with nitrogen and oxygen there were significant increases in blood lactate, glucose and free fatty acids, indicating increased sympathetic activity. We conclude that fentanyl 15 micrograms.kg-1, together with 60 per cent nitrous oxide with oxygen provides a satisfactory haemodynamic and biochemical state during induction of anaesthesia in patients with myocardial function prejudiced by coronary artery insufficiency.

Cardiovascular effects of neurolept anaesthesia in patients with coronary artery disease

An anaesthetic technique comprising a combination of phenoperidine (0.1 mg . kg-1), diazepam (0.06 mg . kg-1) and pancuronium bromide (0.1 mg . kg-1) with controlled ventilation was evaluated in 12 patients with severe coronary artery disease. The heart rate, cardiac output and mean arterial blood pressure did not change significantly between the preinduction and postinduction measurements. The right atrial pressure and pulmonary capillary wedge pressure decreased significantly by 33% and 36%, respectively, probably due to the influence of positive-pressure ventilation. There was no depression of the left ventricular performance.

LEg venous oxygen saturation in the evaluation of intra-operative blood flow during arterial reconstructive surgery

In twenty-four patients, undergoing a femoro-popliteal saphenous vein bypass graft for symptomatic atherosclerotic occlusion of the superficial femoral artery, oxygen saturation values for the femoral and popliteal veins were compared to the directly measured blood flows in the common femoral artery and in the bypass graft, respectively. Blood flow and venous oxygen saturation increased significantly after transfusion of 900 ml of blood. Pharmacological vasodilation caused a significant increase in blood flow both before and after transfusion, whereas the changes in venous oxygen saturation were significant only before blood transfusion. A close statistical relationship was found between initial femoral venous oxygen saturation and initial blood flow in the common femoral artery as well as between initial popliteal venous oxygen saturation and initial byapss blood flow. However, especially at low saturation values, the evaluation of blood flow was very uncertain. Whole leg and lower leg oxygen uptakes were not altered by intraoperative changes in blood volume. It is concluded that blood flow in the common femoral artery and the bypass graft can be roughly estimated from analysis of oxygen saturation in the femoral and popliteal veins, respectively. Furthermore, by determining leg venous oxygen saturation both before and after flow augmentation, induced by pharmacological vasodilation, a conception of the load on the vascular system may be obtained.

Effects of neurolept anaesthesia (NLA) on haemodynamics and oxygen consumption in the dog with special reference to the liver and preportal tissues

The effects of neurolept anaesthesia (NLA) on central circulation, total oxygen uptake and splanchnic circulation and oxygen uptake were studied in 12 artificially ventilated dogs, basally anaesthetized with thiopental and nitrous oxide. Hepatic arterial, superior mesenteric arterial and portal venous blood flows were measured with electromagnetic flowmetry. Cardiac output was measured by thermodilution. Determinations of oxygen contents were made in arterial, pulmonary arterial, portal venous and hepatic venous blood. NLA was induced with droperidol 0.5 mg . kg-1 b.w. and fentanyl 0.01 mg . kg-1 b.w. Arterial blood pressure decreased to 63% of control value due to reductions of cardiac output to 78% and of total peripheral vascular resistance to 81% of control values. Hepatic arterial, superior mesenteric arterial and portal venous blood flows all diminished to 75% of control values. Hepatic arterial, superior mesenteric arterial and preportal tissue vascular resistances all decreased. Total oxygen uptake declined to the same extent as cardiac output, leaving the arterio-venous oxygen difference unchanged. Oxygen uptake of the preportal tissues was unaffected and hepatic oxygen uptake was not significantly reduced, although there were decreases of hepatic oxygen uptake in some of the individual dogs. It is suggested that the cardiovascular depression following NLA was due to adaptation to a lowered total oxygen uptake. It is further concluded that splanchnic circulation was well preserved due to decreases in splanchnic vascular resistances, and that splanchnic oxygen consumption was maintained by means of increased oxygen extraction.

The effect of surgical stress on haemodynamics during neurolept anaesthesia

The influence of surgical stress on haemodynamics during neurolept anaesthesia (NLA) was studied in ten patients, while they were awake, under anaesthesia prior to surgery and peroperatively. Systemic arterial, pulmonary arterial, right atrial and pulmonary capillary wedge pressures, as well as cardiac ouput (Qt), arterial oxygen content and mixed venous oxygen content, were measured. Systemic and pulmonary vascular resistances, arterial-venous oxygen content difference (AVD), oxygen consumption (VO2) and cardiac index (CI) were calculated. On institution of anaesthesia, CI fell from 2.8 +/- 0.1 1/min-m2 to 2.5 +/- 0.2 1/min-m2 and systolic arterial pressure (SBP) fell from 13.4 +/- 0.5 kPa to 10.2 +/- 0.3 kPa. During surgery CI rose to 3.3 +/- 0.1 1/min-m2 and SBP rose to 15.7 +/- 0.6 kPa. Prior to anaesthesia, AVD was 40.2 +/- 0.2 ml/l. Under anaesthesia prior to surgery, AVD did not change, but VO2 declined from 207 +/- 13ml/min to 171 +/- 10 ml/min. During surgery, AVD fell to 30.5 +/- 0.3 ml/l, while VO2 remained unchanged. It is concluded that NLA has a direct metabolic depressant effect and, in association with surgery, is accompanied by hyperkinetic circulation.