Systemic hypertension following myocardial revascularization

Optimizing Pain Management in Cardiac Surgery: A Review of Analgesic Adjuvants

PURPOSE OF REVIEW

Pain management following cardiac surgery is a critical component in optimizing both short- and long-term patient outcomes, with poor pain management associated with significant acute and chronic opioid use, opioid dependence and a significant rate of opioid related adverse drug events. The significant burden of both acute and chronic pain following cardiac surgery has given rise to the need for multimodel analgesic strategies, to optimize outcomes and minimize side effects.

RECENT FINDINGS

While significant research has focused recently on the additive value of peripheral nerve blocks, less emphasis has been given to the value of non-opioid based analgesics in preference to traditional opioid based anesthetic and analgesic strategies. In this review, we examine the evidence for several common analgesics, highlighting the evidence supporting efficacy following cardiac surgery, as well as the safety concerns with each agent. We demonstrate the value of a multimodal analgesic strategy to reduce pain scores and improve patient-centered outcomes, and highlight the need for further studies of combination analgesic strategies.

Comparison of traditional and upper thoracic epidural analgesia after off-pump coronary artery bypass graft surgery: A Quasi-experimental study

Background and Aims

Surgical trauma initiates changes in central and peripheral nervous systems that need to be treated therapeutically to facilitate postoperative pain. The quality of postoperative analgesia is expected to affect clinical outcomes positively. Albeit optimal pain relief following cardiac surgery is often complex, researchers have tried to explore several techniques other than conventional ones during the last decade to find a unique analgesic method for postcardiac surgical patients. This study aims to find a unique analgesic approach that maximizes patient satisfaction after off-pump coronary artery bypass graft (OPCABG) surgery.

Methods

The current study will compare the analgesic effect of upper thoracic epidural analgesia (TEA) with conventional analgesia after OPCAB graft surgery. For this, we will use a Quasi-experimental study design. Patients admitted for coronary artery bypass graft (CABG) surgery will be assigned into two groups. The control group (conventional) will receive intravenous opioids and nonsteroidal anti-inflammatory medications, and the study (case) group (TEA) will receive Inj. Bupivacaine 0.25% as an infusion through the epidural catheter. Physiologic parameters like hemodynamic and respiratory variables and pain scores will be recorded in predesigned format periodically.

Results

We expect to analyze a total of 130 consecutive off-pump CABG surgery patients in Group A (Case, 65 patients) and Group B (Control, 65 patients). Study variables will be the visual analog scale score, hemodynamic parameters (heart rate, mean arterial pressure, and respiratory parameters (respiratory rate, PaO2, PaCO2, PEFR, FEV1). After data collection, the result will be analyzed and published in the public domain and in journals.

Conclusion

We expect thoracic epidural analgesia with local anesthetics will be a reliable postoperative analgesic option.

Pharmacological Review of Postoperative Hypertension

Postoperative hypertension is an acute, transient increase in blood pressure that develops within 30 to 90 minutes following a surgical procedure and typically lasts for 4 to 8 hours after surgery. It is defined as a systolic blood pressure greater than 160 mm Hg or a diastolic blood pressure greater than 90 mm Hg. The increase in blood pressure is primarily due to increased systemic vascular resistance brought about by reflex changes in humoral factors, including increased levels of catecholamines, renin, and serotonin as well as alterations in baroreceptor function and carotid reflexes. Potential complications of untreated postoperative hypertension include depressed left ventricular performance, increased myocardial oxygen demand resulting in ischemic episodes, cerebrovascular accidents, arrhythmias, and suture line disruption and bleeding. Despite longstanding recognition that high blood pressure is a frequent complication after surgery, formal guidelines for the treatment of postoperative hypertension have not been developed. Postoperative hypertension is a pathophysiological state that requires rapid assessment and appropriate treatment. Several pharmacologic agents are available to achieve and maintain normotension after surgery, including nitrovasodilators (nitroglycerin and sodium nitroprusside), adrenergic blocking agents, and dihydroperidine calcium channel antagonists. Angiotensin-converting enzyme inhibitors and fenoldopam also have been used. Each has its own distinct mechanism of action and adverse effect profile. In cardiac surgery, nicardipine is as effective as nitrovasodilators and offers coronary selectivity. In patients who are hypertensive after neurosurgical procedures, avoid direct-acting vasodilators, which may exacerbate increased intracranial pressure; β-adrenergic receptor antagonists and ACEIs are the preferred agents in these patients. More data are needed to define roles and benefits of fenoldopam in managing postoperative hypertension.

The Use of Regional Anesthesia in Combination With General Anesthesia for Cardiac Surgery in Children

The use of regional anesthesia in combination with general anesthesia for children undergoing cardiac surgery is the subject of a growing number of publications and presenta tions. Benefits of regional anesthesia in patients having car diac surgery include attenuation of the neuroendocrine response to surgical stress, improved postoperative pulmo nary function, enhanced cardiovascular stability, and im proved postoperative analgesia. To the extent that regional anesthesia facilitates early tracheal extubation in cardiac surgical patients, complications and costs associated with postoperative mechanical ventilation may be reduced. These benefits must, however, be weighed against the ad verse effects that may accompany the use of regional anes thesia, including hypotension, postoperative respiratory de pression, and epidural hematoma formation. In this article, the benefits and risks of regional anesthesia in infants and children undergoing open heart surgery are reviewed. In addition, specific spinal and epidural techniques currently in use are described, including management of side effects. Copyright © 2001 by W.B. Saunders Company.

Epidural anesthesia improves outcome and resource use in cardiac surgery: a single-center study of a 1293-patient cohort

Thoracic epidural anesthesia (TEA) combined with general anesthesia in cardiac surgery has the potential to initiate earlier spontaneous ventilation and extubation, improved hemodynamics, less arrhythmia or myocardial ischemia, and an attenuated neurohormonal response. The aim of the current study was to characterize the correlation between TEA and postoperative resource use or outcome in a consecutive-patient cohort. The study was performed in a tertiary care, 3-surgeon, university-affiliated hospital that performs 350 to 400 cardiac surgeries per year. All 1293 adult patients who underwent cardiac surgery between July 1, 2002, and February 1, 2006, were included. Patients were assigned to anesthesiologists practicing TEA (TEA group, n = 506) or not (control group, n = 787) for cardiac surgery. The preoperative parameter values and Parsonnet scores for the 2 groups were similar. The 2 groups had the same distribution of surgery types. The TEA group presented with fewer intensive care unit (ICU) complications, such as delirium, pneumonia, and acute renal failure, and presented with better myocardial protection. The TEA group presented with a higher proportion of immediately postoperative extubations and with shorter ventilation times and ICU stays. Total ICU costs decreased from US $18,700 to $9900 per patient. Combining TEA and general anesthesia for cardiac surgery allows a significant change in anesthesia strategy. This change improves immediate postoperative outcomes and reduces the use and costs of ICU resources.

Incidence of epidural haematoma and neurological injury in cardiovascular patients with epidural analgesia/anaesthesia: systematic review and meta-analysis

Background

Epidural anaesthesia is used extensively for cardiothoracic and vascular surgery in some centres, but not in others, with argument over the safety of the technique in patients who are usually extensively anticoagulated before, during, and after surgery. The principle concern is bleeding in the epidural space, leading to transient or persistent neurological problems.

Methods

We performed an extensive systematic review to find published cohorts of use of epidural catheters during vascular, cardiac, and thoracic surgery, using electronic searching, hand searching, and reference lists of retrieved articles.

Results

Twelve studies included 14,105 patients, of whom 5,026 (36%) had vascular surgery, 4,971 (35%) cardiac surgery, and 4,108 (29%) thoracic surgery. There were no cases of epidural haematoma, giving maximum risks following epidural anaesthesia in cardiac, thoracic, and vascular surgery of 1 in 1,700, 1 in 1,400 and 1 in 1,700 respectively. In all these surgery types combined the maximum expected rate would be 1 in 4,700. In all these patients combined there were eight cases of transient neurological injury, a rate of 1 in 1,700 (95% confidence interval 1 in 3,300 to 1 in 850). There were no cases of persistent neurological injury (maximum expected rate 1 in 4,600).

Conclusion

These estimates for cardiothoracic epidural anaesthesia should be the worst case. Limitations are inadequate denominators for different types of surgery in anticoagulated cardiothoracic or vascular patients more at risk of bleeding.

New approaches and old controversies to postoperative pain control following cardiac surgery

OBJECTIVE

To evaluate the effect of postoperative pain control in cardiac surgical patients on morbidity, mortality and other outcome measures.

BACKGROUND

New approaches in pain control have been introduced over the past decade. The impact of these interventions, either alone or in combination, on perioperative outcome was evaluated in cardiac surgical patients.

METHODS

We searched Medline for the period of 1980 to the present using the key terms analgesics, opioid, non-steroidal anti-inflammatory drugs, cardiac surgery, regional analgesia, spinal, epidural, fast-track cardiac anaesthesia, fast-track cardiac surgery, myocardial ischaemia, myocardial infarction, postoperative care, accelerated care programmes, postoperative complications, and we examined and discussed the articles that were identified to be included in this review.

RESULTS

Pain management in cardiac surgery is becoming more important with the establishment of minimally invasive direct coronary artery bypass surgery and fast-track management of conventional cardiac surgery patients. Advances have been made in this area and encompass specific techniques, such as central neuraxial blockade or selective nerve blocks, and drugs (opioids, sedative-hypnotics and non-steroidal anti-inflammatory drugs). Ideally, these therapies provide not only patient comfort but also mitigate untoward cardiovascular responses, pulmonary responses, and other inflammatory and secondary sympathetic responses. The introduction of these newer approaches to perioperative care has reduced morbidity, but not mortality, in cardiac surgical patients.

CONCLUSIONS

Understanding perioperative pathophysiology and implementation of care regimes to reduce the stress of cardiac surgery, will continue to accelerate rehabilitation associated with decreased hospitalization and increased satisfaction and safety after discharge. Reorganization of the perioperative team (anaesthesiologists, surgeons, nurses and physical therapists) will be essential to achieve successful fast-track cardiac surgical programmes. Developments and improvements of multimodal interventions within the context of 'fast-track' cardiac surgery programmes represents the major challenge for the medical professionals working to achieve a 'pain and risk free' perioperative course.

Intrathecal and Epidural Anesthesia and Analgesia for Cardiac Surgery

Adequate postoperative analgesia prevents unnecessary patient discomfort. It may also decrease morbidity, postoperative hospital length of stay and, thus, cost. Achieving optimal pain relief after cardiac surgery is often difficult. Many techniques are available, and all have specific advantages and disadvantages. Intrathecal and epidural techniques clearly produce reliable analgesia in patients undergoing cardiac surgery. Additional potential benefits include stress response attenuation and thoracic cardiac sympathectomy. The quality of analgesia obtained with thoracic epidural anesthetic techniques is sufficient to allow cardiac surgery to be performed in awake patients without general endotracheal anesthesia. However, applying regional anesthetic techniques to patients undergoing cardiac surgery is not without risk. Side effects of local anesthetics (hypotension) and opioids (pruritus, nausea/vomiting, urinary retention, and respiratory depression), when used in this manner, may complicate perioperative management. Increased risk of hematoma formation in this scenario has generated much of lively debate regarding the acceptable risk-benefit ratio of applying regional anesthetic techniques to patients undergoing cardiac surgery.

Coronary artery bypass grafting after a bilateral lung volume reduction operation

A 67-year-old man underwent coronary artery bypass grafting 31/2 months after a bilateral lung volume reduction operation for end-stage pulmonary emphysema. The principles of anesthetic management we have developed for use during volume reduction operations were applied with success in this individual and are described in detail. With the increasing application of this intervention as an alternative to lung transplantation, we anticipate further experience in the operative management of associated conditions after lung volume reduction operations.

Sodium nitroprusside after cardiac surgery: systemic and splanchnic blood flow and oxygen transport

BACKGROUND

Vasoactive drugs may interfere with splanchnic blood flow and tissue oxygenation. Sodium nitroprusside (SNP) is widely used in the treatment of postoperative hypertension after cardiac surgery, but the effects of SNP and other vasodilators on splanchnic blood flow have not been well documented.

METHODS

The effects of SNP on systemic blood flow, oxygen transport and gastric intramucosal pH (pHi) were studied in 12 patients with arterial hypertension after coronary artery bypass grafting. In 9 of these patients, the effect on regional (splanchnic and leg) blood flow and oxygen transport was also measured. Hemodynamic and regional blood flow responses were measured before and during SNP infusion (mean 2.8 +/- 1.7 micrograms/kg/min, range 0.6-6.3 micrograms/kg/min), when the goal of the vasodilator treatment, mean arterial pressure 70-80 mmHg, had been reached.

RESULTS

SNP increased splanchnic (0.65 +/- 0.22 vs. 0.87 +/- 0.37 L.min-1.m-2, P < 0.01) and femoral blood flow (0.15 +/- 0.04 vs. 0.21 +/- 0.06 L.min-1.m-2, P < 0.05) in parallel with cardiac index (2.6 +/- 0.6 vs. 3.3 +/- 0.7 L.min-1.m-2, P < 0.01). Fractional regional blood flows did not change. Mean gastric intramucosal pH decreased slightly (7.40 +/- 0.07 vs. 7.37 +/- 0.06, P < 0.05). Both systemic (420 +/- 85 vs. 495 +/- 90 mL.min-1.m-2, P < 0.05) and femoral oxygen delivery (25 +/- 5 vs. 32 +/- 10 mL.min-1.m-2, P < 0.05) increased, but neither systemic nor regional oxygen consumption changed.

CONCLUSIONS

These results suggest that vasoregulation is well preserved during treatment of early postoperative hypertension with SNP, and that SNP has no adverse effects on splanchnic tissue oxygenation.

Thoracic epidural analgesia in aortocoronary bypass surgery. I: Haemodynamic effects

Tachycardia and hypertension may cause myocardial ischaemia in patients with coronary heart disease going through major surgery. Thoracic epidural analgesia (TEA) has been reported to be beneficial in this situation. The haemodynamic effects of TEA in aortocoronary bypass surgery were investigated in 30 male patients < 65 years old and with ejection fraction > 0.5. They were randomized into 3 groups: the high dose fentanyl (HF) group receiving high-dose fentanyl (55 micrograms.kg-1) anaesthesia, the HF+TEA group receiving the same fentanyl dose+TEA with 10 ml bupivacaine 5 mg.ml-1 followed by 4 ml every hour, and the low dose fentanyl (LF) + TEA group receiving low-dose fentanyl (15 micrograms.kg-1) anaesthesia+TEA. Haemodynamic parameters, the use of vasoactive and inotropic drugs and fluid balance were followed during the operation and for 20 h postoperatively. Before bypass the only significant difference between groups was a higher mean pulmonary arterial pressure in the HF+TEA group and a lower systemic vascular resistance (SVR) in the LF+TEA group, both compared to the HF group. 89% of epidural group patients needed small doses of ephedrine whereas more HF group patients were given nitroglycerine. During bypass SVR and mean arterial pressure (MAP) were significantly higher and pump flow lower in the HF group compared to the LF+TEA group. More ketanserin to HF group patients and methoxamine to epidural group patients were given. After bypass heart rate increased in all groups. Lower MAP 0.5 h after bypass and higher filling pressures in the early post bypass period in the epidural groups, most pronounced in the HF+TEA group, were noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative study of isradipine and sodium nitroprusside in the control of hypertension in patients following coronary artery-bypass surgery

Essential hypertension is a common occurrence after coronary artery bypass-graft surgery. CABG and may lead to postoperative complications. In an open randomized study, either isradipine or sodium nitroprusside was given by infusion to 27 postoperative CABG patients who had a mean arterial pressure (MAP) greater than 100 mmHg. Both agents were able to achieve reductions in MAP to 80-90 mmHg quickly and safely, although the effects of isradipine at the dosage used were apparent sooner and gave smoother control than with sodium nitroprusside. There were two non-responders with the latter agent. Systemic vascular resistance fell and cardiac output increased in patients in both treatment groups. Also, an increase in heart rate was observed with both agents, although this increase was smaller with isradipine. In conclusion, isradipine appears to be a useful agent in the treatment of hypertension following CABG surgery and may have some advantages over sodium nitroprusside.

Clonidine improves perioperative myocardial ischemia, reduces anesthetic requirement, and alters hemodynamic parameters in patients undergoing coronary artery bypass surgery

The purpose of this study was to determine if clonidine reduces myocardial ischemia or alters anesthetic requirement and perioperative hemodynamic parameters during coronary artery bypass grafting (CABG) surgery. Forty-three patients were randomized in a prospective, double-blind fashion to receive either clonidine (5 micrograms/kg) or placebo. Anesthetic induction and maintenance was accomplished with intravenous sufentanil-midazolam (S-M) in a 1:20 ratio; up to 1.0% enflurane was added during surgery when repeated boluses of S-M failed to maintain the blood pressure within 20% of preinduction values. Continuous ST segment analysis of leads II and V5 was performed throughout surgery with maximal ST segment deflection from baseline recorded every 5 minutes. Catecholamine levels were measured intermittently throughout the perioperative period and myocardial lactate use or excretion was determined just prior to cardiopulmonary bypass (CPB) and at 1, 5, 10, 30, and 60 minutes after release of the aortic cross-clamp. Patients who received clonidine required significantly less sufentanil for their surgical procedure (11.82 +/- 0.66 micrograms/kg v 14.55 +/- 0.90 micrograms/kg, P < 0.05) and also needed less enflurane for blood pressure control, particularly during CPB (P < 0.05). Baseline hemodynamic parameters were similar for both groups prior to induction. In the period between anesthetic induction and the initiation of CPB, patients treated with clonidine had a significantly slower heart rate (HR) (P < 0.01), a lower cardiac output (CO) (P < 0.05), and transiently higher systemic vascular resistance (SVR) (P < 0.05) than placebo-treated patients. Immediately after CPB, patients receiving clonidine continued to have a significantly lower CO (P < 0.01) and a higher SVR (P < 0.01) than placebo-treated patients. Clonidine treatment significantly increased the percentage of patients who required pacing after CPB (P < 0.05). In the intensive care unit, clonidine-treated patients displayed a persistently increased requirement for pacing (P < 0.01), decreased systolic blood pressures, and reduced sodium nitroprusside requirements relative to patients treated with placebo. Epinephrine and norepinephrine levels were lower in clonidine-treated patients throughout the perioperative procedure with significant differences noted immediately following sternotomy and release of the aortic cross-clamp (P < 0.05). Critical ST segment depression was significantly less in clonidine-treated patients for the period from sternotomy until application of the aortic cross-clamp (P < 0.01). Following CPB, absolute deviation of ST segments from isoelectric baseline was significantly less in the clonidine-treated group (P < 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of a cardiac surgical recovery area on the timing of extubation

The anesthetic and postoperative management of cardiac surgical patients was modified to achieve an early return to spontaneous ventilation. A total of 278 patients were studied to determine the effect of this change. Patients in group I (n = 198) were managed in a cardiac surgical recovery area according to the new policy. Group II (n = 80) was a comparable group of patients operated upon before this change. The median duration of postoperative ventilation was reduced from 5 hours in group II to 1 hour in group I, and the time to extubation was reduced from 7 hours to 2 hours, respectively. There were no major postoperative complications resulting from this change. The factors that influence the duration of postoperative ventilation are discussed.

Multicenter trial of automated nitroprusside infusion for postoperative hypertension. Titrator Multicenter Study Group

Hypertension is common after a cardiac operation and may result in postoperative hemorrhagic and other complications. Most often this problem has been treated using manually controlled doses of intravenous sodium nitroprusside. To evaluate the clinical impact of an automated closed-loop administration system on patients after cardiotomy, a prospective trial was conducted at nine clinical centers. Patients with hypertension were managed by either manual nitroprusside titration (n = 532) or a closed-loop automated titration system (n = 557). Patient groups were not significantly different in age, weight, or height. Moreover, the types of surgical procedures were comparable: primary coronary artery bypass grafting, 59.2% and 58.9%, manual group versus automated group; repeat coronary artery bypass grafting, 10.5% and 8.6%, respectively; valve procedures, 11.3% and 15.1%, respectively; and other cardiac procedures, 19.0% and 17.4%, respectively (all p = not significant). The automated group showed a significant reduction in the number of hypertensive episodes per patient (1.8 +/- 0.2 versus 0.6 +/- 0.07; p = 0.0001. At the same time, the number of hypotensive episodes per patient was reduced with automated closed-loop titration (0.40 +/- 0.05 versus 0.30 +/- 0.03; p = 0.02). Chest tube drainage (866 +/- 37 mL versus 693 +/- 23 mL [mean +/- standard error of the mean]; p = 0.0001), percentage of patients receiving transfusion (40.0% versus 33.0%; p = 0.02), and total amount transfused (2.4 +/- 0.12 units versus 2.0 +/- 0.10 units; p = 0.0003) were all reduced significantly by the use of an automated titration system.(ABSTRACT TRUNCATED AT 250 WORDS)

Does propranolol alter the vascular response to phenylephrine before or during halothane anaesthesia in patients with coronary artery disease?

Preoperative beta-adrenergic blockade with propranolol, by allowing unopposed alpha-adrenergic stimulation in response to stress, has been suggested as a factor contributing to hypertension following coronary artery bypass surgery (CABG). Thus, one might expect to find an exaggerated haemodynamic response to phenylephrine (PHE), an alpha 1 agonist. To study this, the cardiovascular response to PHE infusion at 30, 40, and 50 microgram.min-1 prior to and during halothane anaesthesia was measured before surgical stimulation during elective CABG in patients taking chronic propranolol therapy and compared with that of patients not taking any cardiovascular medications. Chronic propranolol therapy did not alter the haemodynamic response to PHE, before or during halothane anaesthesia, and the incidence of postoperative hypertension requiring vasodilator therapy was the same for both groups.

Early extubation after coronary artery surgery in efficiently rewarmed patients: a postoperative comparison of opioid anesthesia versus inhalational anesthesia and thoracic epidural analgesia

Twenty-eight patients were studied after uncomplicated aortocoronary bypass surgery with hypothermic cardiopulmonary bypass (CPB). In all patients residual hypothermia was effectively treated by the use of extended rewarming during CPB and postoperatively by an external heat source. This treatment almost eliminated postoperative shivering, and it resulted in the lowering of oxygen uptake, carbon dioxide production, and required ventilatory volumes to stable levels where spontaneous breathing could be used safely. The patients were divided into two groups. In group I (n = 12), intraoperative anesthesia was based on an intravenous (IV) opioid (phenoperidine), which caused persistent respiratory depression and made mechanical ventilation necessary for a mean postoperative time period of 10.7 +/- 3.8 hours even with the rewarming. In group II (n = 16), thoracic epidural analgesia and intraoperative general anesthesia with enflurane were used. In this group, postoperative metabolic and ventilatory requirements were stable and low, finger skin temperature was normalized earlier, systemic vascular resistance was lower, and stroke index was higher. Emergence from anesthesia was uneventful and was achieved early postoperatively in Group II. The patients had good pain relief and were mentally alert. Adequate spontaneous breathing was resumed quickly and endotracheal extubation was performed within the first two postoperative hours (1.6 +/- 0.5 hours). No complications or increased morbidity occurred, and no patient needed to be reintubated in Group II.

Automated control of postoperative hypertension: a prospective, randomized multicenter study

Hypertension after a cardiac operation is a frequent phenomenon. Complications resulting from this include bleeding, disruption of vascular suture lines, subendocardial ischemia, and possible cerebrovascular accidents. Treatment with sodium nitroprusside has become accepted practice to prevent these complications. To improve control of arterial blood pressure, a closed-loop system for sodium nitroprusside administration was developed. A prospective, randomized multicenter study was carried out postoperatively in 180 cardiac surgical patients to evaluate the performance of this system compared with manual control of infusion. Adherence of mean arterial blood pressure to +/- 10% of the target blood pressure occurred 85% of the time with the automatic system and 61% of the time with manual regulation (p less than 0.0001). With the automatic system, there was less hypertension (9% versus 22%; p less than 0.0001) and hypotension (6% versus 22%; p less than 0.0001). The superior control of hypertension was achieved more rapidly with less requirement for nurse regulation of infusion rate. The superior control of blood pressure resulted in less chest tube drainage in the automatic mode (720 mL versus 840 mL; p less than 0.05).

Effect of preoperative renin-angiotensin system blockade on hypertension following coronary surgery

Renin-angiotensin system activation is suspected of being involved in postcoronary surgery hypertension, but appears to be useful in maintaining blood pressure during anesthesia and cardiopulmonary bypass. To clarify these points, 19 patients were compared: ten as a control group and nine who received captopril during two days before surgery. Anesthesia was the same for the two groups, and cardiopulmonary bypass ensured nonpulsatile flow rates. Anesthesia induced a slight decrease in the mean arterial blood pressure of the treated group (91.1 +/- 3.3 mm Hg to 83.3 +/- 3.9 mm Hg), which did not occur in the control group (89.9 +/- 5.8 mm Hg to 89.7 +/- 4.9 mm Hg). During cardiopulmonary bypass, the mean arterial blood pressure was maintained at comparable levels in the two groups (65.6 +/- 3.5 mm Hg in the control group, 72.6 +/- 3.0 mm Hg in the treated group), with same pump flow rates. After cardiopulmonary bypass, the mean arterial blood pressure returned nearly to prebypass values. Postoperatively, three patients in the control group and four in the treated group developed hypertension. Thus, preoperative renin-angiotensin system blockade by a converting-enzyme inhibitor did not impair blood pressure regulation during anesthesia and cardiopulmonary bypass, but failed to prevent hypertension following coronary surgery.

Patient monitoring during and after open heart surgery by an improved deep body thermometer

The deep body thermometer developed by Fox was improved by Togawa by thermal insulation of the probe. The present status of medical progress in clinical thermometry through the improved deep body thermometer was reviewed from the view point of cardiac surgery. The forehead and sole temperatures obtained by this improved thermometer were monitored and recorded by a multipotentiometric recorder continuously up to 12 days in the patients admitted to the ICU who underwent open heart surgery. The forehead tissue temperature measured by this thermometer is slightly lower than and parallel to the rectal temperature, being close to the pulmonary arterial blood temperature. On the other hand, the sole tissue temperature fluctuates from room temperature to the forehead tissue temperature, sometimes showing rhythmic changes. The former seems to be the core temperature and the latter, the shell temperature. The dissociation when the two temperatures are more than 7 degrees C apart from each other suggests that the hemodynamical condition is worse than in the convergence when they remain within 2 degrees C. A state of shock can be diagnosed when the arterial systolic pressure is less than 90 mmHg and the urine output less than 1 ml/min/mg in addition to the dissociation. The effect of treatment and the prognosis for the patient are predictable according to the trends of the two temperatures as divergent or convergent. The dynamic thermometry by this thermometer is very informative and the procedure is noninvasive without discomfort to the patient.

Pathophysiology of hypertension following coronary artery bypass surgery: an experimental dog model for postoperative hypertension

Immediate postoperative hypertension has been reported to occur during the first 3-6 h in 30%-75% of patients who have undergone aortocoronary bypass operations. Although some causes and potential predisposing factors of this type of hypertension have been cited, the mechanisms involved still remain unclear. Some studies have implicated the involvement of nerve reflexes originating from the heart, great vessels, and coronary arteries, but they do not explain the exact role of such impulses. The paucity of data in humans is, needless to say, due primarily to the invasive nature of the experimental procedure. To further our knowledge on the involvement of nerve reflexes as a factor in initiating immediate postoperative hypertension, we used a dog model and devised a modified form of surgery by inserting a soft catheter into the left coronary artery to form a stenosis; we measured several factors usually involved in hypertension. We succeeded in performing this modified form of surgery in 10 of 81 dogs. Our model showed that the mean aortic pressure significantly increased from 81 +/- 5.5 to 102 +/- 7.0 mmHg (P less than 0.05), systemic vascular resistance from 7604 +/- 833 to 9648 +/- 1101 dyn.s.cm-5 (P less than 0.05), and plasma noradrenaline levels from 0.45 +/- 0.092 to 0.51 +/- 0.087 ng/ml (P less than 0.01) immediately after restoration of blood flow to the distal area behind the stenosis. These dynamic and humoral characteristics are similar to ones documented in current clinical reports. To our knowledge, this is the first experimental animal model of hypertension after coronary artery bypass graft surgery.

Factors relating to the development of hypertension after cardiopulmonary bypass

Paroxysmal hypertension after cardiac surgery is a phenomenon of physiological and clinical significance. The possible preoperative and intraoperative factors that may predict its occurrence were studied in 81 consecutive patients undergoing coronary artery surgery (n = 58) or valve replacement (n = 27), of whom 45 (56%) developed postoperative hypertension. Hypertension occurred significantly more often in those patients who received beta adrenergic blocking agents preoperatively and who underwent coronary artery surgery. Patients with hypertension had significantly higher mean left ventricular ejection fractions preoperatively (52%) than those without (41%) and required phentolamine significantly more often and isoprenaline significantly less often intraoperatively. It is suggested that the significance of preoperative beta adrenergic blockade, the type of operation, and the intraoperative requirement for phentolamine in patients who developed post-operative hypertension may indicate the role of enhanced sympathetic activity and disturbance of cardiac receptors during surgery. Preoperative myocardial performance and the method of myocardial protection during surgery are likely to influence the occurrence of the hypertensive phenomenon.

The role of isosorbide dinitrate in the treatment of perioperative hypertension

Intravenous nitroglycerin (NTG) has recently been found to be useful for the control of blood pressure during the perioperative period, especially during coronary artery bypass procedures. The objective of this study was to determine whether intravenous isosorbide dinitrate (ISDN) could play a similar role. Sixty-seven patients undergoing coronary artery bypass grafting at three centers were randomly assigned to an ISDN or NTG treatment group. The hemodynamic performance of all patients was assessed by the methods commonly used for cardiac patients (ECG, arterial line, thermodilution pulmonary artery catheter). One of the two nitrates was infused whenever the systolic blood pressure or the pulmonary capillary wedge pressure exceeded predetermined values. Treatment by either agent was considered successful if the elevated values returned to normal. NTG reduced the blood pressure in a higher percentage of hypertensive events. The rates of success were 84% for NTG vs 72% for ISDN in the prebypass phase, 93% vs 64% in the postbypass phase, and 71% vs 54% in the postoperative phase. Increased ISDN effectiveness may be attained with the use of a bolus administration before continuous infusion or with the use of a rapid rate of infusion.

Role of renin-angiotensin system in cardiopulmonary bypass hypertension

The role of the renin-angiotensin system in the aetiology of perioperative hypertension was studied in 15 previously normotensive patients undergoing coronary artery surgery and anaesthetized with fentanyl. Measurements of plasma renin activity were made at intervals before and during cardiopulmonary bypass (CPB). In addition, angiotensin II blockade with saralasin was used in an attempt to treat hypertension during CPB. Nine of the patients became hypertensive (increase in systemic pressure of more than 20 per cent) before CPB and although the mean plasma renin activity was higher in this group than in the normotensive patients it was within normal limits for each group. Hypertension during CPB (mean blood pressure greater than 100 mmHg at 1.8 l X m-2 flow), occurred in seven patients but was not associated with increased renin activity and did not respond to saralasin in doses up to 20 micrograms X kg-1 X min-1. It is concluded that cardiopulmonary bypass associated hypertension is not mediated by activation of the renin-angiotensin system.

Cardiac factors in response to antihypertensive treatment

The cardiac status of hypertensive patients will influence not only the indications for and choice of antihypertensive agents but can also alter the effectiveness of antihypertensive therapy. The heart may interfere with adequate blood pressure control either because of marked increases in cardiac output or as result of decompensation activating various pressor mechanisms or through the generation of pressor reflexes. Reflex increases in cardiac output may blunt or even nullify the effect of reduction in peripheral resistance by vasodilators. Cardiac decompensation from incidental disease or secondary to some antihypertensive drugs can lead to hypertension rather than reduction in blood pressure. It is particularly liable to develop from excessive fluid retention, particularly when associated with reduction of cardioadrenergic support. Coronary insufficiency from either coexisting coronary disease or triggered by injudicious antihypertensive treatment can stimulate pressor reflexes leading to marked fluctuations in arterial pressure. Alterations in left ventricular relaxation and rapid filling have been reported with some antihypertensive drugs; these changes could conceivably influence blood pressure responses through their effect on reflexes from low pressure baroceptors.

The adverse effect of systemic hypertension following myocardial reperfusion

Transient myocardial ischemia in postoperative hypertension is relatively common with coronary artery bypass surgery. This study examines the effect of hypertension during reperfusion of transiently ischemic myocardium. The animal model was open chest pigs with myocardial ischemia induced by the occlusion of the left anterior descending coronary artery for 30 min followed by 2 hr of reperfusion. A normotensive control group was compared with animals rendered hypertensive with phenylephrine during the ischemic and reperfusion times. In the hypertensive group, systolic blood pressure was raised from 106 to 161 mm Hg and peripheral vascular resistance from normal to 3600 dyn-sec-cm-5. Regional left ventricular wall thickness, mitochondrial function, sarcoplasmic reticulum Ca2+ uptake, tissue calcium, water content, and hemorrhage were evaluated. Compared to controls the hypertensive group had (1) loss of systolic wall thickening with increased diastolic wall thickness in the reperfused zone, (2) intramyocardial hemorrhage in the area of reperfusion, (3) significant impairment of oxidative phosphorylation by mitochondria isolated from the reperfused zone, (4) a marked reduction in the rate of Ca2+ uptake by sarcoplasmic reticulum vesicles, and (5) an increase in ischemic tissue calcium. Thus, hypertension associated with revascularization of acutely ischemic myocardium may accentuate myocardial damage.

Hypertension following coronary artery bypass graft

Hypertension following coronary surgery is generally reported at an alarmingly high incidence (30 to 75 per cent). A vigilance program carried out in 1977 at the Montreal Heart Institute disclosed a low incidence of 3.5 per cent in 200 consecutive unselected cases. A similar program in 1980 based on 160 cases showed an incidence of 23.7 per cent. This highly significant difference is found to be related to the differences in anaesthetic management which have occurred since 1977 when anaesthesia was primarily morphine 1.0 to 1.5 mg . kg-1 supplemented as needed with low dose halogenated agents and vasodilation therapy. In 1980, only one of the authors (J.T.) still uses this technique. The incidence of hypertension in 40 of his patients was 2.5 per cent. The others use low dose fentanyl (7.5 to 10 micrograms . kg-1) supplemented as needed with halogenated agents and vasodilating therapy; the incidence of hypertension in 160 cases was 23.7 per cent. Would these results be the same with an anaesthetic technique comparing both drugs at equipotent doses? A prospective clinical study is addressing this question.

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.