Systemic hypertension associated with coronary artery bypass surgery

Comparative clinical study of pulsatile and non-pulsatile perfusion in 350 consecutive patients

Pulsatile perfusion has been shown to offer significant haemodynamic advantages over non-pulsatile perfusion in many experimental studies. Clinical acceptance of pulsatile perfusion during cardiac surgical procedures has, however, been hampered by the lack of technologically satisfactory pulsatile pump systems, and by inadequate clinical experience of routine use of pulsatile perfusion. The recent introduction of reliable pulsatile pump systems with low haemolysis characteristics has made possible the clinical validation of the previous experimental studies. We describe the results of a prospective study of mortality, haemodynamic morbidity, and haematological status, in 350 consecutive adult patients submitted to cardiopulmonary bypass procedures in a surgical unit over a 12-month period. One hundred and seventy five patients were perfused with conventional non-pulsatile flow and 175 with pulsatile flow, using a modified roller-pump pulsatile system (Cobe-Stockert). The groups were closely similar in terms of preoperative characteristics, referral category, and pathology requiring surgery. Operative techniques, bypass parameters, and anaesthetic regime were standardised in both groups. The results were as follows. (1) Total mortality was significantly lower in the pulsatile group (4.6%) compared with the non-pulsatile group (10.3%), p = 0.06. (2) The incidence of deaths attributable to post-perfusion low cardiac output was significantly lower in the pulsatile group (1.1% compared with 6.3%, p = 0.02). (3) Requirement for mechanical (intra-aortic balloon) or drug circulatory support was significantly lower in the pulsatile group. (4) The use of pulsatile perfusion was not associated with any increase in haemolysis, blood cell depletion, or postoperative bleeding problems.

Intravenous isosorbide dinitrate in the management of acute hypertension following cardiopulmonary bypass

Twenty-one patients with acute systemic hypertension following cardiopulmonary bypass received isosorbide dinitrate intravenously in order to determine its effectiveness in managing this postoperative problem. Twenty patients underwent coronary artery bypass operation, and 1 patient had a pulmonary valvotomy. Bolus administration (0.25 to 2.5 mg [3.0 to 40.0 micrograms per kilograms]) decreased systemic systolic blood pressure 23% and diastolic blood pressure 25% (both, p less than 0.01). Continuous controlled infusion (0.125 to 0.332 mg per minute [1.5 to 6.0 micrograms/kg/min]) caused a more modest drop in systemic blood pressure, with a 17% reduction in systolic blood pressure and an 11% drop in diastolic blood pressure (both, p less than 0.05). Additional pressure reduction and maintenance therapy were provided by intermittent bolus administration or a continuous infusion. Moderate venodilation (decrease in central venous pressure) accompanied the systemic pressure response. The heart rate was not appreciably altered and, with exception of 1 patient in whom systemic pressures were reduced to 105/60 mm Hg after bolus infusion, the desired level of systolic, diastolic, and mean arterial pressures were readily titrated and maintained in a stable, predictable manner. These observations suggest that intravenously administered isosorbide dinitrate is a practical, safe, and highly effective method of treatment of hypertension following cardiopulmonary bypass.

Changes in peripheral vascular and cardiac sympathetic activity before and after coronary artery bypass surgery: interrelationships with hemodynamic alterations

The plasma catecholamine levels obtained simultaneously from radial artery (A), pulmonary artery (MV), brachial vein (PV), and coronary sinus (CS) were measured concurrent with hemodynamic determinations during coronary artery bypass graft (CABG) operations. Arterial catecholamine levels decreased after induction of anesthesia and increased after sternotomy; changes in veno-arterial norepinephrine (NE) differences ([PV-A]ne, [MV-A]ne, and [CS-A]ne) were of the same magnitude and direction, suggesting that NE release from various organs was of the same extent. After operation, arterial NE increased further, but the veno-arterial NE differences were in striking contrast; [PV-A]ne became markedly positive, whereas [CS-A]ne became markedly negative, indicating that NE release from extremity peripheral vasculature increased markedly while cardiac NE release decreased. These differential changes in regional sympathetic activity appear to be related to postoperative hypertension (HT) and low cardiac output (CO). There were close relationships of changes in [MV-A]ne to mean arterial pressure (r = 0.78, p less than 0.001) and systemic vascular resistance (r = 0.62, p less than 0.010, suggesting that the sympathetic nervous system plays an important role in CABG perioperative hemodynamic alterations.

Effects of pulsatile and non-pulsatile perfusion on the isolated canine heart

Isolated canine hearts with a critical stenosis on one coronary artery were perfused for 2 h with blood from supporting dogs using a new roller pump system that can deliver pulsatile or non-pulsatile flow perfusion. Non-pulsatile perfusion caused a decrease in coronary venous oxygen tension of 22% (P less than 0.05) accompanied by increasing carbon dioxide tension of 50% (P less than 0.02). With pulsatile flow coronary venous oxygen and carbon dioxide tensions remained stable. Non-pulsatile perfusion decreased the coronary arteriovenous oxygen difference by 35% (P less than 0.02), coronary blood flow by 40% (P less than 0.02), and myocardial oxygen consumption by 54% (P less than 0.01) whereas pulsatile flow did not change any of these variables. Subendocardial blood flow distal to the stenosis fell by 0.15 +/- 0.04 ml/min per gram myocardium (mean +/- S.E.M.) (P less than 0.01) during linear perfusion. The endocardial/epicardial-flow ratio was less than one and decreased further during fibrillation period indicating underperfusion of the endocardial muscle region. With pulsatile flow subendocardial flow remained unaltered during the two hours of fibrillation. Edema formation was 24% in hearts subjected to non-pulsatile flow but only 14% in hearts perfused by pulsatile perfusion (P less than 0.05). Accordingly, the ischemic area involved 40% of the left ventricle during non-pulsatile flow but 25% of the left ventricle in hearts perfused by pulsatile perfusion (P less than 0.05). The results indicate that pulsatile flow perfusion may prevent severe hemodynamic, hematologic, and metabolic alterations in fibrillating isolated canine hearts. It is suggested that pulsatile perfusion may be useful for fibrillating hearts during open heart surgery.

Haemodynamic responses to antagonism of pancuronium and alcuronium block

Using non-invasive methods, haemodynamic responses to antagonism of pancuronium (Pc) and alcuronium (Ac) block were compared in patients anaesthetized with thiopental-N2O-fentanyl and undergoing minor surgery. Neuromuscular block (90%) was maintained with Pc in 10 patients and Ac in 10 patients. After surgery, atropine 0.015 mg kg-1 and neostigmine 0.03 mg kg-1 (AN) were given simultaneously. The rate of reversal of the block was equal in the two groups. Between 4 and 16 min after AN, the decrease of heart rate (HR) was more pronounced in patients who had received Pc. The mean of the lowest HR was 43.2 beats min-1 in the Pc group, compared with 62.0 beats min-1 in the Ac group. The bradycardia was associated with a moderate decrease in arterial pressure in patients treated with Pc. However, due to an increase in stroke volume, mean cardiac output (CO) was not lower in the Pc group. Some patients treated with Pc developed a temporary nodal rhythm after AN and this was associated with a considerable decrease in CO. It is concluded that, in spite of marked bradycardia during antagonism of Pc block, circulation is well maintained, provided that sinus rhythm is present.

Suppression of renin production in patients undergoing coronary artery bypass

Twenty patients undergoing elective myocardial revascularization for coronary insufficiency were divided into two equal groups. In 10 patients, propranolol was discontinued 24 hours before operation while the remaining patients received propranolol until the day of operation. Plasma renin was elevated in the intensive care unit in the control group (p < 0.05) whereas patients receiving propranolol did not demonstrate significant elevation of plasma renin. Systemic vascular resistance was elevated in both groups in the intensive care unit (p < 0.05) and was associated with hypertension as defined by a blood pressure of greater than or equal to 160/100 mm Hg in 80% of the control patients and 70% of patients receiving propranolol. We conclude from this study that renin metabolism does not contribute significantly to the production of hypertension following coronary artery operation.

Pathogenesis of paroxysmal hypertension developing during and after coronary bypass surgery: a study of hemodynamic and humoral factors

A prospective study of hypertension first appearing during and after saphenous vein bypass coronary surgery was performed in 28 patients to examine the incidence, hemodynamics and mechanism of this problem. In 15 patients (54 percent) new hypertension developed (mean arterial pressure greater than 107 mm Hg), characterized by increased peripheral vascular resistance and unchanged cardiac output within 1 hour after surgery. These 15 patients had a longer history of angina of greater severity, but also had relatively well preserved ventricular myocardium. Because plasma renin activity was depressed in patients in the hypertensive group, activation of the renin-angiotensin system was not important in the pathogenesis of this postoperative hypertension. The expected decrease in total peripheral resistance at the onset of cardiopulmonary bypass was observed in all patients, but later during bypass the peripheral resistance increased in all patients in association with a rise in plasma epinephrine levels. Patients who had hypertension postoperatively had a greater increase in arterial pressure and total peripheral resistance during cardiopulmonary bypass than did those with normal postoperative blood pressure. An elevation in plasma epinephrine and norepinephrine concentration, suggesting enhanced sympathoadrenal responsiveness to the challenge of cardiopulmonary bypass, was characteristic of the hypertensive group. This evidence of enhanced sympathetic activity during surgery may be a useful predictor of the development of postoperative hypertension.

Systemic arterial hypertension associated with cardiac surgery

Significant hypertension can develop in 15 to 40 percent of patients undergoing various types of cardiac surgery. These hypertensive episodes can occur at almost any time before, during or after open or closed chest operations. The various hypertensions encountered in this context do not form a homogeneous entity; they are nt due to the same causes and do not necessarily develop by the same mechanisms. Their frequency and seriousness have been demonstrated by reports from many centers: hence, the urgent need for accurate definition of their various types to allow correct identification and therapy. A classification based on well defined clinical events is therefore proposed and possible mechanisms for the more common types of hypertension are reviewed. Prophylactic measures nclude reassurance, attention to details of anesthesia and maintenance of preoperative antihypertensive therapy when indicated; for patients with coronary artery disease, preventive nitrate therapy as well as prompt attention to chest pain is essential. Both general and specific antihypertensive measures to control the more common types of hypertension complicating cardiac surgery are outlined.

Hypertension following coronary artery bypass surgery. Role of preoperative propranolol therapy

Over a 9-month period, the incidence and characteristics of hypertension following coronary artery bypass surgery were studied in a group of 52 patients. Hypertension occurred in 61% of the patients and was characterized by an increase in arterial blood pressure of 35 +/- 2 mm Hg mean +/- SEM during the early postoperative period. Preoperative blood pressures and hemodynamic variables were similar in those who developed hypertension of those who remained normotensive. Ninety-four percent of those who developed hypertension as compared to only 40% of those who remained normotensive received propranolol during the 24 hours preceding surgery (x2 = 15.4; p less than 0.001). Maximal blood pressures during the first 5 hours following the termination of cardiopulmonary bypass were significantly positively correlated with preoperative propranolol dosage (p less than 0.01). Hypertension was not associated with significant changes in plasma renin activity or angiotensin II levels, but concomitant plasma catecholamine concentrations were elevated significantly (p less than 0.005). However, a similar rise in plasma catecholamine concentrations was found in those who remained normotensive. Hypertension was associated with an increase in systemic vascular resistance (p less than 0.001) and left ventricular stroke work index (p less than 0.05), and a fall in stroke volume (p less than 0.005) and cardiac index (p less than 0.001). These studies suggest that hypertension following coronary artery bypass surgery is common, results from an increase in systemic vascular resistance, is not renin-angiotensin mediated, and may, in part, be related to preoperative propranolol administration.

MB creatine kinase and the evaluation of myocardial injury following aortocoronary bypass operation

Myocardial injury was studied in 104 patients undergoing coronary artery grafting without cold chemical cardioplegia using the quantity of the isoenzyme MB of the creatine kinase liberated as an indicator. This method of evaluation, which is said to permit comparison of different techniques of myocardial protection, allowed us to consider the relative importance of several factors believed to have an influence on intraoperative myocardial injury. Indices of significance were duration of symptoms before operation, presence of chronic arterial hypertension, and the type of antiangina treatment employed. Other operative factors included severity of the arterial lesions, number of anastomoses performed, and duration of extracorporeal circulation and of aortic cross-clamping.

Effects of the converting enzyme inhibitor (SQ 20881) on the pulmonary circulation in man

The effects of the converting enzyme inhibitor (SQ 20881) on the pulmonary circulation were investigated in 13 patients in whom systemic hypertension developed following coronary artery bypass surgery. Pulmonary vascular resistance was decreased by the inhibitor, from 128 +/¿ 19 to 92 +/- 20 dynes sec cm-5 (or by 30 +/- 7 per cent; P less than 0.005), and this resulted in a decrease in mean pulmonary artery pressure from 17 +/- 1 to 13 +/- 1 mm Hg (or by 23 +/- 3 per cent, P less than 0.005). Consequently, right ventricular work was decreased by the inhibitor by 30 per cent (P less than 0.01), despite an increase in cardiac output (increase in stroke volume) by 16 +/- 6 per cent (P less than 01). This increase occurred despite a 13 +/- 3 per cent decrease in right ventricular filling pressure. The changes in pulmonary vascular resistance correlated with the pretreatment plasma renin activity (r = 0.74, P less than 0.01), as did the decrease in mean pulmonary artery pressure (R = 0.82, P less than 0.001), but neither change was related to the decrease in left ventricular fillling pressure nor to changes in cardiac output or mean arterial pressure. These results indicate that blockade of the formation of angiotensin II by the converting enzyme inhibitor results in reductions in pulmonary vascular resistance and pulmonary artery pressure which are unrelated to alterations in left ventricular function. Thus, angiotensin inhibition may have therapeutic value in various clinical states characterized by pulmonary hypertension--especially if renin levels are high.

Myocardial performance early after aorto-coronary bypass surgery and the influence of nitroprusside infusion

The central and peripheral circulation were studied in 12 patients after aortocoronary bypass surgery. During the initial 5 h after termination of cardiopulmonary bypass, the oesophageal temperature rose from 36.5 degrees C to 39.4 degrees C, concomitant with cutaneous vasoconstriction and an increase in systemic vascular resistance (SVR) and mean arterial blood pressure (MABP). The oxygen uptake index (Vo2I) increased by 57% during the rewarming period. The cardiac index (CI), which was constant at 2.8 l.min-1.m-2, was too low to satisfy this oxygen demand and the arterio-venous oxygen content difference (AVDo2) increased to 3.0 mmol . l-1 by the 3rd hour. After 5 h, SVR had decreased and cutaneous vasodilation began. Vo2I and AVDo2 decreased. The postoperative myocardial function was moderately impaired and deteriorated after the cutaneous vasodilation. Twelve patients were given an infusion of sodium nitroprusside during the postoperative period (0.25--2.5 micrograms . kg-1 . min-1). The rewarming pattern was not influenced by this infusion, but the initial increases in MABP and SVR were eliminated. The myocardial performance was better in the nitroprusside group. CI was significantly higher than in the control group (3.5 l.min-1.m-2) and AVDo2 remained normal.

Does pulsatile flow influence the incidence of postoperative hypertension?

Twenty patients undergoing primary elective aorta--coronary artery bypass were divided into two equal groups, both receiving identical premedication, anesthetic, and pump primes. The control patients received hypothermic nonpulsatile flow and the study patients received hypothermic pulsatile flow. Hypertension, defined as a pressure of 160/100 mm Hg or higher, was observed in 80% of the control patients and 20% of the patients receiving pulsatile flow (p less than 0.05). Serial renin measurements demonstrated maximum values in the intensive care unit and coincided with the onset of postoperative hypertension in the control patients. Those patients who had received pulsatile flow did not demonstrate notable renin stimulation. Catecholamines were markedly elevated during bypass and in the intensive care unit, but there was no significant difference between the two groups. Peripheral vascular resistance was not significantly lower with pulsatile flow, except in the first study performed in the intensive care unit. We conclude that catecholamines and the renin-angiotensin system contribute to the production of postoperative hypertension and that pulsatile flow diminishes renin stimulation. Pulsatile flow results in a decreased incidence of postoperative hypertension.

Right stellate ganglion block for treatment of hypertension after cardiopulmonary bypass

Right stellate ganglion block was performed on 24 patients in whom hypertension developed after cardiopulmonary bypass. Changes in blood pressure, central venous pressure, cardiac output, and heart rate were evaluated. Most patients evidenced a decrease in systolic blood pressure (average, 40 mm Hg) and diastolic blood pressure (average, 19 mm Hg). Systemic vascular resistance was measured in 8 patients, and 7 demonstrated a decrease (average reduction, 6.7 resistance units). Changes in cardiac output were variable. Although stellate ganglion block can be safely performed and, in most patients, markedly reduces systolic blood pressure, the results suggest that other hypotensive agents may be more advantageous in the treatment of hypertension subsequent to coronary artery operation.

Unilateral stellate block in the treatment of hypertension after coronary bypass surgery. Implications of a new therapeutic approach

Unilateral stellate ganglion block (right or left) was achieved by local injection of 15 ml of lidocaine in 27 patients with hypertension after coronary bypass surgery. The stellate block led to rapid and sustained control of blood pressure in 18 patients (9 of 15 with right stellate block and 9 of 12 with left stellate block). The reduction in arterial pressure was associated with significant (P less than 0.01) reductions in total peripheral resistance and heart rate but no significant changes in cardiac output or central venous or left atrial pressures. This hemodynamic pattern as well as effectiveness of a unilateral approach suggests that the stellate block reduced arterial pressure by interrupting the afferent limb of a pressor reflex from the heart or great vessels, or both. The procedure was free from side effects and helped avoid prolonged parenteral administration of potent antihypertensive drugs.