Audit of postoperative pain control. Influence of a dedicated acute pain nurse

The inadequacies of conventional intramuscular opioid analgesia have fueled an expansion in the use of patient-controlled analgesia and epidural analgesia after surgery. This is not always accompanied by increased education and specialist supervision of ward staff and patients. A survey in our hospital prior to the appointment of an Acute Pain Nurse showed an unacceptable incidence of side effects when epidural analgesia was employed on ordinary surgical wards. More surprisingly, efficacy of patient-controlled analgesia was found to be low. Frequent review of patients and regular education of ward staff by a specialist Pain Nurse have achieved a substantial reduction in side effects of epidural analgesia and improvement in efficacy of patient-controlled analgesia. We have shown that the advantages of patient-controlled analgesia can be largely negated by failure to address deficiencies in knowledge of pain management among ward staff and patients.

Hypotension, subarachnoid block and the elderly patient

This article reviews the current literature on the management of hypotension during subarachnoid block in the elderly. Hypotension results from blockade of the sympathetic nervous system, which causes decreases in both systemic vascular resistance and cardiac output. Abolition of normal cardiovascular reflexes is also important and may explain unexpected cardiac arrests during subarachnoid block. Untreated block in the elderly results in decreases in systolic arterial pressure, systemic vascular resistance and central venous pressure. Cardiac output appears not to decrease as has been previously reported and heart rate is affected by several different factors. Preload to the heart should be maintained during block by giving adequate intravenous fluids and 8 ml.kg-1 is satisfactory in most cases. Adequate preloading prevents decreases in cardiac output and unexpected cardiac arrests. In this respect, mild head down till is also beneficial. Ideally, intravenous fluid should be given as the block is developing. Excessive fluid administration serves no useful purpose and can cause fluid overload and urinary retention. If systolic arterial pressure decreases by more than 25%, or to below 90 mmHg, treatment with a vasopressor is indicated. The efficacy of ephedrine has recently been questioned, as it is a poor vasoconstrictor and inotrope in the elderly. The alpha-adrenoceptor agonists may prove a more logical choice, because they increase both peripheral resistance and preload. Metaraminol by infusion (< 10 ml.h-1 of 10 mg in 20 ml) has been used successfully, though hypertension can occur.

Percutaneous transluminal angioplasty of the symptomatic atherosclerotic carotid arteries. Results, complications, and follow-up

BACKGROUND AND PURPOSE

Carotid endarterectomy reduces stroke risk in patients with > 70% symptomatic stenosis. We present our results of percutaneous transluminal angioplasty (PTA) as an alternative treatment.

METHODS

Ninety-eight patients with symptomatic > 70% stenosis of the internal carotid artery were considered for PTA. Details of the procedure, complications, and 4-year follow-up were registered.

RESULTS

Eighty-five PTAs were performed in a 4-year period. Transient cardiovascular effects were frequent: hypotension (54.1%), bradycardia (67.1%), asystole (25.9%), and syncope (16.5%). Transient ischemic attack occurred in 3 of 82 patients (3.7%), and disabling stroke occurred in 4 (4.9%); mortality was 0%. After a mean follow-up period of 18.7 months, 4 patients died, 1 due to fatal stroke. The overall probability of surviving any stroke or death was 86.7%. Restenosis (> 70%) was seen in 6 cases (7.4%).

CONCLUSIONS

PTA may be a reasonable treatment for symptomatic atherosclerotic stenosis, at least in patients at high risk for carotid endarterectomy.

Magnetic resonance imaging-monitored acute blood-brain barrier changes in experimental traumatic brain injury

The authors posit that cellular edema is the major contributor to brain swelling in diffuse head injury and that the contribution of vasogenic edema may be overemphasized. The objective of this study was to determine the early time course of blood-brain barrier (BBB) changes in diffuse closed head injury and to what extent barrier permeability is affected by the secondary insults of hypoxia and hypotension. The BBB disruption was quantified and visualized using T1-weighted magnetic resonance (MR) imaging following intravenous administration of the MR contrast agent gadolinium-diethylenetriamine pentaacetic acid. To avoid the effect of blood volume changes, the maximum signal intensity (SI) enhancement was used to calculate the difference in BBB disruption. A new impact-acceleration model was used to induce closed head injury. Forty-five adult Sprague-Dawley rats were separated into four groups: Group I, sham operated (four animals), Group II, hypoxia and hypotension (four animals), Group III, trauma only (23 animals), and Group IV, trauma coupled with hypoxia and hypotension (14 animals). After trauma was induced, a 30-minute insult of hypoxia (PaO2 40 mm Hg) and hypotension (mean arterial blood pressure 30 mm Hg) was imposed, after which the animals were resuscitated. In the trauma-induced animals, the SI increased dramatically immediately after impact. By 15 minutes permeability decreased exponentially and by 30 minutes it was equal to that of control animals. When trauma was coupled with secondary insult, the SI enhancement was lower after the trauma, consistent with reduced blood pressure and blood flow. However, the SI increased dramatically on reperfusion and was equal to that of control by 60 minutes after the combined insult. In conclusion, the authors suggest that closed head injury is associated with a rapid and transient BBB opening that begins at the time of the trauma and lasts no more than 30 minutes. It has also been shown that addition of posttraumatic secondary insult-hypoxia and hypotension-prolongs the time of BBB breakdown after closed head injury. The authors further conclude that MR imaging is an excellent technique to follow (time resolution 1-1.5 minutes) the evolution of trauma-induced BBB damage noninvasively from as early as a few minutes up to hours or even longer after the trauma occurs.

Lack of inhibitory effect of atrial natriuretic factor on renin release induced by renal hypotension

To examine the effect of atrial natriuretic factor (ANF) on renin release induced by renal hypotension, experiments were performed in seven barbiturateanaesthetized dogs with denervated kidneys. Renin release induced by renal arterial constriction to 55 mmHg was measured before and during intrarenal infusion of ANF (200 ng min-1 kg-1 body weight). Before ANF infusion, renal arterial constriction increased renin release from 0.2 +/- 0.1 to 21.8 +/- 3.3 micrograms angiotensin I min-1 (p < 0.05). During ANF infusion renal arterial constriction increased renin release as much as before from 0.8 +/- 0.6 to 23.7 +/- 4.6 micrograms angiotensin I min-1 (p < 0.05). Although ANF increased glomerular filtration rate from 33.9 +/- 4.2 to 43.4 +/- 5.6 ml min-1 (p < 0.05) and sodium excretion from 72 +/- 22 to 567 +/- 112 mumol min-1 (p < 0.05) at normal renal perfusion pressure, ANF was without effect on glomerular filtration rate and sodium excretion during renal arterial constriction. The present study shows that ANF is not an inhibitor of renin release induced by renal arterial constriction in anaesthetized dogs with denervated kidneys. Our findings indicate that ANF does not influence renin release induced by the haemodynamic mechanism.

Hypotension after blunt abdominal trauma: the role of emergent abdominal sonography in surgical triage

OBJECTIVE

Trauma victims with hypotension require a rapid and reliable localization of bleeding and expedient surgical triage. Our hypothesis is that emergent abdominal sonography (EAS) is a rapid and accurate test of the need for urgent laparotomy in blunt trauma victims with hypotension.

METHODS

Among 400 blunt trauma victims entered in a prospective blind study of EAS, a subgroup of 69 (17%) patients had a systolic blood pressure < or = 90 mm Hg during their initial assessment. Although the EAS results [(+) = fluid, (-) = no fluid] were not used in clinical decision making, the potential contribution of EAS to patient care was examined.

RESULTS

The mean Injury Severity Score was 32. Twenty-two (32%) patients were EAS (+), of which 19 required an acute laparotomy. No laparotomies were performed in the 47 EAS (-) patients. The EASs required 19 +/- 5 seconds in the EAS (+) group and 154 +/- 13 seconds in the EAS (-) group. Twenty of the 22 positive EASs had free fluid in Morison's pouch. All 13 patients with an ultrasound score > or = 3 had a laparotomy. The primary etiology of hypotension was blood loss in 42 patients, hemoperitoneum in 18, and retroperitoneal hemorrhage in 12.

CONCLUSION

EAS is a rapid and accurate indicator of the need for urgent laparotomy in the hypotensive blunt trauma victim. Further, a negative EAS can hasten the search for other causes of hypotension. Diagnostic peritoneal lavage may become obsolete in centers with EAS capabilities.

Factors associated with hypotension and bradycardia after epidural blockade

In order to identify patient-, anesthesia-, and surgery-related factors influencing the probability of hypotension and bradycardia after epidural blockade, an observational study was conducted on 1050 nonpregnant patients. Backward stepwise logistic regression was performed on the variables hypotension (systolic blood pressure < 90 mm Hg) and bradycardia (heart rate < or = 45 bpm). Hypotension and bradycardia occurred in 158 and 24 patients, respectively. The probability of hypotension increased when epidural fentanyl was administered (odds ratio [OR] = 2.18; 95% confidence interval [CI] = 1.16-4.11), with body weight and spread of epidural analgesia, and decreased when a tourniquet was used (OR = 0.01, CI = 0.01-0.02) and bupivacaine instead of carbonated lidocaine was administered (OR = 0.28, CI = 0.14-0.60). Sensitivity and specificity of the model were 89% and 88%, respectively. The probability of bradycardia was less in women (OR = 0.05, CI = 0.01-0.41) and when a tourniquet was used (OR = 0.04, CI = 0.02-0.09). Sensitivity and specificity were 50% and 97%, respectively. In conclusion, our analysis can contribute to identification of patients at high risk to develop hypotension and bradycardia after epidural blockade. If bupivacaine instead of carbonated lidocaine is used and epidural fentanyl is not administered a decrease in the incidence of hypotension may be anticipated.

Prediction of outcome for critically ill patients with unexplained hypotension

OBJECTIVES

To determine the clinical variables that affect the prognosis of critically ill patients with sustained unexplained hypotension. A further goal was to develop a prognostic scoring system based on clinical data available at the onset of hypotension.

DESIGN

Prospective cohort study.

SETTING

The intensive care units (ICUs) of an academic medical center.

PATIENTS

One hundred one adult ICU patients with sustained (> 60 mins) unexplained hypotension. Using the initial 50 patients (derivation set), a prognostic score was developed that was then tested in the next 51 patients (validation set).

INTERVENTIONS

None

MEASUREMENTS AND MAIN RESULTS

The main outcome variable was death or hospital discharge. The overall hospital mortality in the combined sets was 58%. Using a multivariable model we identified three independent (p < .05) predictors of hospital mortality, including the Acute Physiology and Chronic Health Evaluation (APACHE) II score at the time of hypotension, the time from hospital admission to hypotensive episode, and hospital admission for surgery or treatment of malignancy. These variables were weighted and combined to create a Hypotension Score which separated patients in the combined sets into three prognostic groups: a) Hypotension Score of < 40, mortality 7%, (n = 27); b) Hypotension Score of 40 to 64, mortality 70%, (n = 50); and c) Hypotension Score of > or = 65, mortality 92%, (n = 24). The area under the receiver operating characteristic curve was .85 for the derivation set and .83 for the validation set vs. .76 for the APACHE II score alone.

CONCLUSIONS

The prognosis of hypotension in the critical care setting is highly variable, but can be predicted from patient characteristics.

Subarachnoid neostigmine does not affect blood pressure or heart rate during bupivacaine spinal anesthesia

BACKGROUND AND OBJECTIVES

Intraspinal administration of neostigmine has been shown to prevent induction of hypotension in rats by bupivacaine spinal block, and thus to provide greater hemodynamic stability. This study was undertaken to determine whether subarachnoid neostigmine would prevent bupivacaine spinal anesthesia from causing hypotension or bradycardia in patients undergoing abdominal hysterectomy.

METHODS

Of 40 patients scheduled for abdominal hysterectomy under spinal anesthesia, 20 were randomly assigned to each of two groups. The control group (CG) received 1.5 mL subarachnoid saline followed by 15 mg (3 mL) of hyperbaric bupivacaine 0.5%. The neostigmine group (NG) received 75 micrograms (1.5 mL) of subarachnoid neostigmine followed by 15 mg (3 mL) of hyperbaric bupivacaine 0.5%. No preload was given. Hypotension was treated with 4-mg intravenous boluses of ephedrine to keep blood pressure above 75% of the baseline value. The skin body temperature was measured with probes at the suprascapular region and at the foot.

RESULTS

Spinal neostigmine (75 micrograms) failed to prevent bupivacaine-induced hypotension. There was no statistical difference in the incidence of brady-cardia between the groups (NG, 2/20; CG 1/20), although the bradycardia appeared to be qualitatively different, being somewhat delayed in the NG. Spinal neostigmine did not alter the onset or duration of sensory block and did not affect skin body temperature in either anesthetized or unanesthetized sites. The incidence of intraoperative nausea was 20% in the NG and 5% in the CG.

CONCLUSION

A 75-micrograms subarachnoid neostigmine dose does not affect blood pressure or heart rate during bupivacaine spinal anesthesia.

Cardiovascular involvement in leptospirosis

Cardiovascular involvement was studied in 50 patients with serologically proved leptospirosis. Twelve (24%) patients had dyspnoea and 18 (36%) had transient hypotension during the illness. None of them had cardiac enlargement, development of new murmur or pericardial rub. Various electrocardiographic abnormalities occurred in 70 percent of patients. Atrial fibrillation was the most common major arrhythmia (14%). Conduction system abnormalities were seen in 36 percent of patients. T-wave changes were observed in 30 percent of patients. Left ventricular function as assessed by echocardiography and Doppler examination was normal. Three (6%) patients died due to renal failure. In conclusion, even though ECG abnormalities were frequently seen in leptospirosis, there was no data to support associated left ventricular dysfunction. Dyspnoea and hypotension occurring in patients of leptospirosis must be due to a noncardiac mechanism.

High level of circulating human tissue kallikrein induces hypotension in a transgenic mouse model

We established a unique transgenic mouse model in liver-targeted expression of human tissue kallikrein using a mouse albumin enhancer and promoter. Northern blot analysis and ELISA showed that human tissue kallikrein was predominantly expressed in the liver of transgenic mice and secreted into the circulation at a high level. The transcript was also detected in the kidney, pancreas, salivary gland and heart at a low level by reverse transcription-polymerase chain reaction followed by Southern blot analysis. Systolic blood pressures were measured by the tail-cuff method, all three independent transgenic mouse lines are hypotensive (84.6 +/- 1.0 mmHg, n = 17; 84.5 +/- 1.5 mmHg, n = 9; 83.1 +/- 0.8 mmHg, n = 13, P < 0.01) compared with the control mice (100.9 +/- 0.9 mmHg, n = 17). Administration of aprotinin, a potent tissue kallikrein inhibitor or Hoe 140, a bradykinin receptor antagonist, restored the blood pressure of transgenic mice but had no significant effect on control littermates. These studies show that over-production of tissue kallikrein in the circulation plays a role in blood pressure regulation.

Circulatory, respiratory, cerebral, and renal derangements in acute liver failure: pathophysiology and management

Many of the hemodynamic abnormalities seen in acute liver failure (ALF) have now been characterized. A lowered systemic vascular resistance with a raised cardiac output are prominent features, which in part are modulated by nitric oxide (NO). At a cellular level, oxygen supply and utilization are impaired by changes in vascular tone, plugging of nutritive vessels, and pathological shunting. The use of N-acetylcysteine (NAC) and prostacyclin, a vasodilator, have been shown to increase oxygen utilization in the microcirculation. NAC may act by enhancing the effect of NO on guanylate cyclase, increasing the formation of cyclic 3',5'-guanosine monophosphate (cGMP), and thereby resulting in vasodilatation. This suggests that despite overproduction of NO in ALF, there is a short-age/ failure of utilization at a cellular level. Appropriate management of these patients should be based on a good knowledge of the underlying pathophysiology, and thus on monitoring, during the course of the disease.

Sequential hemodynamic changes for large volume paracentesis in post-hepatitic cirrhotic patients with massive ascites

Large volume paracentesis (4.8 to 15.5 liters) was performed in 42 patients with post-hepatitic cirrhosis and massive ascites, not only to derive parameters capable of predicting the development of severe clinical hypotension after large volume paracentesis, but also to determine the optimal time to introduce preventive volume expanders. Systemic hemodynamics were sequentially measured for 72 hours in thirty-two patients. Severe clinical hypotension occurred in 13 (31.0%) patients 4-62 hours from the start of paracentesis. Univariate analysis, with the Mantel-Cox test used to compare Kaplan-Meier curves, and the subsequent multivariate analysis by stepwise Cox regression procedure were utilized to identify two variables, withdrawn ascitic fluid greater than 7.5 liters (p = 0.0121) and the absence of peripheral edema (p = 0.0148), reaching statistical significance to predict the occurrence of severe clinical hypotension. Compared to the baseline value, the cardiac output of patients not developing severe clinical hypotension increased (6.26 +/- 0.66 vs. 6.65 +/- 0.69 liter/min, p < 0.01) one hour from the start of paracentesis and right atrial pressure decreased (11.2 +/- 2.4 vs. 8.7 +/- 2.3 mmHg, p < 0.05). The cardiac output returned to the baseline value at the 9th hour. Based on the results presented herein, we can conclude that severe clinical hypotension occurs in a high percentage of patients with post-hepatitic cirrhosis and massive ascites within 72 hours from the start of large volume paracentesis. At potential risk of this occurring are those patients without peripheral edema and withdrawn ascitic fluid greater than 7.5 liters. Volume expanders should be introduced before 4th hour from the start of large volume paracentesis.

Hypotensive reactions to white cell-reduced plasma in a patient undergoing angiotensin-converting enzyme inhibitor therapy

BACKGROUND

Hypotensive reactions to platelet transfusions performed with white cell (WBC)-reduction filters with negatively charged surfaces have been reported recently in patients taking angiotensin-converting enzyme (ACE) inhibitors. Experimental studies have shown that the filter material can activate bradykinin, which may cause symptoms in patients with reduced bradykinin catabolism. Symptomatic adverse reactions after the administration of fresh-frozen plasma (FFP) through a WBC-reduction filter have not been reported in a patient on ACE Inhibitor medication.

CASE REPORT

A 58-year-old man with congenital coagulation factor V deficiency and hypertension treated with an ACE inhibitor was admitted for rehabilitation after orthopedic surgery. On 3 consecutive days, he received FFP through a WBC-reduction filter; within minutes of the beginning of each infusion, he experienced a drop in blood pressure, facial erythema, abdominal pain, and anxiety. When the infusions were stopped, symptoms quickly abated without treatment. Multiple prior transfusions of unfiltered FFP and FFP filtered through a WBC-reduction filter made by a different manufacturer, as well as subsequent transfusions of unfiltered FFP, had not produced such reactions.

CONCLUSION

Facial flushing, hypotension, and abdominal pain after FFP administration in a patient on ACE inhibitor medication appeared to be associated with a specific type of WBC-reduction filter. This association and other reported studies suggest that special caution is warranted when patients who are treated with ACE inhibitors receive blood components administered through WBC-reduction filters capable of generating bradykinin.

Hypotensive reactions: a previously uncharacterized complication of platelet transfusion?

BACKGROUND

In 1993, the American Association of Blood Banks (AABB) received reports of severe hypotensive reactions associated with platelet transfusions. The question arose as to whether these reports were indicative of a previously uncharacterized platelet transfusion reaction.

STUDY DESIGN AND METHODS

To further characterize these reactions, the AABB Transfusion Practices Committee developed a series of three questionnaires. The initial questionnaire was sent to all AABB institutional members; the two subsequent questionnaires were sent to those institutions reporting severe and/or unusual platelet transfusion reactions. This report focuses on the 24 responses to the third and most detailed questionnaire, which specifically addressed reactions that were characterized by hypotension and/or unexplained respiratory failure.

RESULTS

Of the 24 detailed responses received, 4 were not considered to represent unusual reactions to platelet transfusion, 3 described reactions consistent with a (presumably unrecognized) diagnosis of transfusion-related acute lung injury, and 17 described reactions that were primarily characterized by hypotension. The majority of the hypotensive reactions occurred within 1 hour of the beginning of the transfusion (88%), were associated with respiratory distress (82%), and resolved rapidly after cessation of the transfusion (82%). Eighty-eight percent of implicated components had been white cell reduced by filtration.

CONCLUSION

The hypotensive platelet transfusion reactions that were described appear to represent a previously uncharacterized complication of platelet transfusion. However, the nature of the questionnaires used in this investigation does not allow the drawing of firm conclusions as to the frequency or the cause of these reactions.

Attenuated blood pressure responsiveness during post-exercise hypotension

OBJECTIVE

To test the hypotheses that acute treadmill exercise would produce post-exercise hypotension (PEH) and that PEH would be associated with reduced mean arterial pressure (MAP) responsiveness to the alpha 1-adrenergic agonist phenylephrine.

METHODS

Arterial and venous catheters were implanted into exercise-trained female Dahl-salt sensitive rats (n = 9) for measurement of pulsatile blood pressure (BP) and heart rate (HR). The changes in BP following ganglionic blockade (hexamethonium/atropine) and the MAP responses to phenylephrine (PE) injections after ganglionic blockade (GB) were examined on separate days in testing cages (control) and following 40 min of treadmill exercise (post-ex).

RESULTS

Thirty minutes following graded treadmill exercise (20-40 m/min, 0% grade, 40 min duration) blood pressure was significantly reduced (-9 +/- 1) mmHg compared to control. After exercise, GB produced a 43 +/- 3 mmHg decrease in BP which tended (p = 0.08) to be less than the reduction observed during control studies (51 +/- 2 mmHg). PE-induced increases in BP were significantly lower post-ex than control for each of the dosages tested (0.5, 1.0 and 2.0 micrograms/kg).

CONCLUSIONS

These results demonstrate that there is sustained reduction in PE-induced MAP responsiveness which accompanies exercise-induced decreases in blood pressure in the Dahl salt-sensitive rat. Thus, decreased alpha-adrenoceptor responsiveness may contribute to the production of PEH.

Viscoelastic mechanisms of aortic baroreceptor resetting to hypotension and to hypertension

Viscoelastic and electrophysiological mechanisms have been implicated in the resetting of baroreceptors in hypertension, but resetting in response to hypotension has been less studied. To evaluate the temporal relationship between viscoelastic mechanisms and acute resetting, we examined the "in vivo" behavior of aortic caliber and aortic baroreceptor activity during step changes in pressure. Fifteen-minute hemorrhage in Wistar rats produced stable hypotension (30 mmHg) and viscoelastic contraction (111 +/- 14.2 microns systolic caliber; P < 0.01). Integrated aortic activity fell to 19.8 +/- 3.9% of control (P < 0.001) after 3 s of hypotension but recovered to 64 +/- 4.1% 15 min later (P < 0.01 from 3 s). Recovery of baroreceptor activity was linearly correlated to viscoelastic contraction (r = 0.963; P < 0.0001). Thirty-minute phenylephrine infusion (1.0-4.0 micrograms/min) produced stable hypertension (30 mmHg) and viscoelastic dilation (211 +/- 37.0 microns systolic caliber). Integrated aortic activity increased to 218.0 +/- 18% of control values (P < 0.001) 30 s after hypertension and was reduced to 164.0 +/- 12.0% (P < 0.001 from 3 s) within 30 min. Reduction of baroreceptor activity correlated linearly with viscoelastic relaxation (r = 0.963; P < 0.0001). The results indicate that in the in vivo rat aorta, viscoelastic mechanisms parallel and may contribute to the baroreceptor resetting during hypotension and hypertension.

Low blood pressure in Down's syndrome, A link with Alzheimer's disease?

Low blood pressure is reported in Down's syndrome (DS). To assess this and determine whether low pressure results from the disease or from long-term residence in hospital, we measured blood pressure with a random-zero sphygmomanometer in three groups of patients: 52 DS inpatients, 62 DS outpatients, and 60 outpatients with other forms of mental handicap. Relative to normal reference populations, blood pressure was low in both DS inpatients (systolic, score -33 mm Hg, P < .0001) and DS outpatients (-25 mm Hg, P < .0001). It was normal in non-DS outpatients (-4.0 mm Hg, P = .3). Blood pressure rose normally with age in the non-DS group but not in the DS group. We conclude that blood pressure is low in DS and that this is a feature of the disease rather than of the protected environment in which patients live. A mechanism related to trisomy 21 is likely, and there may be a link with Alzheimer's disease (AD) because blood pressure is also low in Alzheimer's and a high proportion of Ds patients develop this disease. If, as is likely, blood pressure is lowered in Alzheimer's by the neuropathy, the same neuropathy developing early in DS may also reduce blood pressure.

Superoxide dismutase (SOD) prevents hypotension after hemorrhagic shock and aortic cross clamping

To determine if superoxide dismutase (SOD) administration attenuates injury caused by supraceliac aortic cross clamping, a randomized controlled study on 12 taconic rats was performed at the university hospital research center at Syracuse, New York. All animals were anesthetized and placed on a ventilator through a tracheotomy. Surgical preparation included catheterization of carotid and femoral arteries, and the jugular vein. A midline laparotomy was performed through which the supraceliac aorta was exposed and isolated. Animals were allowed to stabilize after surgery and baseline measurements [systemic pressure (Psys), central venous pressure, and blood gases] were recorded. Then, animals were subjected to 60 minutes of hemorrhagic shock (mean Psys = 35 mm Hg), followed by 45 minutes of supraceliac aortic cross clamping. After the release of the aortic cross clamp, shed blood was reinfused. After stabilization, all animals were monitored for 60 minutes. Rats were separated into two groups: the experimental group (n = 6) that received intravenous SOD before and during aortic cross clamping, and the control group (n = 6) that received an equivalent volume of saline at the same time periods. No difference was detected in overall arterial pH, partial arterial carbon dioxide pressure, or base excess at any time period between the groups. A significant increase in Psys was measured in the experimental group compared with the control group from the time of aortic cross-clamp release until the experiment was terminated. One hour after aortic cross-clamp release, the Psys for the experimental group was 69.2 +/- 10.6 mm Hg vs. 36.7 +/- 3.8 mm Hg for the control group (P < 0.05). These data demonstrate that superoxide dismutase significantly improves postaortic cross-clamp Psys. This suggests that oxygen-derived free radicals play a role in postaortic cross-clamp hypotension.

[The risk of surgical treatment in elderly patients]

The course of surgical treatment of 124 patients aged over 70 years was subjected to an assessment. On the basis of the ASA classification, 88% of all surgically treated patients fell into group III-IV of risk. Surgical operations were performed under intratracheal general anaesthesia (85%) or conduction anaesthesia (15%). The induction of general anaesthesia was accompanied by adverse reactions of the cardiovascular system in the form of arterial blood pressure drops and heart rhythm disturbances. Heart rhythm disturbances were not observed in patients under conduction anaesthesia. No intraoperative deaths were noted.