Estimating discharge rates of oily wastes and deterrence based on aerial surveillance data collected in western Canadian marine waters

Illegal discharge of waste oil from ships is a major source of mortality for seabirds globally. Using linear and log-linear regression, we explored the relationship between detection rates of marine oily discharges and surveillance effort at different time scales, based on data collected in the Canadian Pacific Ocean by the National Aerial Surveillance Program (NASP) from 1997 to 2006. We introduce an approach for quantifying reductions in discharge rates with increased surveillance while controlling appropriately for surveillance effort, as standard linear correction for effort can introduce considerable bias. Despite low probabilities of detection (0.088-1.1%), we found evidence for reduced discharge rates with increasing surveillance effort for data summarized monthly and bimonthly in region A, which is closest to the NASP base airport. Using residuals derived from the best-fit log-linear models, we found detected discharge rates declined annually (-[0.070 spills/month]×year).

Plasma levels of potassium and magnessium after modified ultrafiltration in pediatric cardiac surgery with cardiopulmonary bypass

Objective: Modified ultrafiltration (MUF) reduces some of the complications associated with cardiopulmonary bypass (CPB) in pediatric cardiac surgery. However, we have observed hypokalemia and hypomagnesemia in children when MUF is used. Such alterations may elicit severe arrhythmias in the postoperative period. To date, no studies have focused on the effects MUF may have in plasma levels of potassium (K) and magnesium (Mg). The objective of our study was to determine if there is any variation in plasma levels of K (plK) and Mg (plMg) after MUF in children undergoing cardiac surgery with CPB.

Patients: Sixteen children scheduled for cardiac surgery with CBP and MUF were prospectively studied. Anesthetic, CPB and MUF management were standardized for all patients, the latter lasting for 10 minutes.

Results: Plasma K average levels before and after MUF were 4.16 mmol/L and 3.58 mmol/L, respectively. The average plasma Mg levels before and after MUF were 4.82 mmol/L and 4.81 mmol/L, respectively.

Conclusions: The plasma level of K is reduced by 13.7% after MUF (p<0.0001). The reduction in Mg at the same period of time was not statistically significant (p<0.970).

[Carotid endarterectomy under regional anesthesia: initial experience]

BACKGROUND

Endarterectomy is the treatment of choice for internal carotid artery critical stenosis. Some authors have proposed that the use of regional anesthesia has advantages over general anesthesia.

AIM

To report our initial experience with carotid endarterectomy under regional anesthesia.

PATIENTS AND METHODS

Between 1998 and 1999, patients with critical carotid artery stenosis, asymptomatic or with transient and recovered symptoms, were selected. A C2, C3, C4 root deep cervical block and superficial block was performed, using a mixture of lidocaine and bupivacaine. A carotid endarterectomy with patch and without routine shunt insertion, with standard and neurological monitoring, was performed.

RESULTS

During the study period, 94 carotid endarterectomies were done, 22 under regional anesthesia in 21 patients (12 male, age range 58-90 years old). Ninety five percent had hypertension, 52% smoked and 38% had renal dysfunction. One patient was converted to general anesthesia. Seventeen patients were discharged within 48 hours of the procedure and the rest, within 72 hours. There was no mortality or complications.

CONCLUSIONS

Endarterectomy under regional anesthesia is less invasive, has excellent results and is well accepted by patients.

Hemodilution does not alter the aortic-to-femoral arterial pressure difference in dogs

INTRODUCTION

Distal arterial pressure normally differs from aortic pressure. This difference is modified by changes of vascular resistance. Hemodilution, due to decreased viscosity, decreases vascular resistance. Therefore, the difference between aortic and distal arterial pressures could be altered as well. We investigated whether acute hemodilution affected this difference in dogs.

METHODS

Eleven mongrel dogs weighing 16.6 +/- 4.4 kg were anesthetized with pentobarbital and sufentanyl and mechanically ventilated. Arterial presssure was recorded using Millar catheter-tipped pressure transducers in the proximal aorta and in the distal femoral artery. An electromagnetic flowmeter probe was placed around the aorta. Effective downstream pressure was estimated by extrapolation of exponential arterial pressure decay during 3-second occlusion of the proximal aorta. Hemodilution was effected by removal of 30 ml/kg of blood and replacement with 60 ml/kg of warmed saline. In addition, the effects of 1 microg/kg phenylephrine and 4 microg/kg of sodium nitroprusside were measured before and after hemodilution.

RESULTS

Hemodilution decreased hematocrit from 39 +/- 11.2% to 25.6 +/- 4.95%. Systolic and mean pressures were unchanged but aortic diastolic pressure decreased significantly, from 86 +/- 17 to 79 +/- 15 mmHg (p < 0.005). Peak systolic pressure was 13.5 +/- 7.2 mmHg higher in the femoral artery than in the aorta before, and 16 +/- 8.7 mmHg after, hemodilution (p > 0.05). Nitroprusside decreased the femoral to aortic peak systolic pressure difference from 14.3 +/- 6.3 to 7.7 +/- 15.3 mmHg, p = 0.05 before hemodilution and from 14.3 +/- 8.8 to 2.5 +/- 11 mmHg, p < 0.005 afterwards. Hemodilution significantly decreased the effective downstream pressure, from 44 +/- 9 to 36 +/- 6.8 mmHg in the aorta (p < 0.05), and from 51 +/- 2 to 37 +/- 3.1 mmHg in the distal femoral artery (p < 0.05).

CONCLUSION

Acute hemodilution did not alter the aortic-to-distal arterial pressure difference in dogs.

Cardiopulmonary bypass: new strategies for weaning from cardiopulmonary bypass

This review focuses on weaning from cardiopulmonary bypass, a very critical time for patients and anaesthetists and frequently requiring major therapeutic effort. Few novel strategies for weaning have been described recently. Most drugs or approaches described during the review period are already well established. Emphasis is placed on the importance of non-cardiac factors, and on the importance of diastolic ventricular function as opposed to systolic function.

An expert system for monitor alarm integration

OBJECTIVE

Intensive care and operating room monitors generate data that are not fully utilized. False alarms are so frequent that attending personnel tends to disconnect them. We developed an expert system that could select and validate alarms by integration of seven vital signs monitored on-line from cardiac surgical patients.

METHODS

The system uses fuzzy logic and is able to work under incomplete or noisy information conditions. Patient status is inferred every 2 seconds from the analysis and integration of the variables and a unified alarm message is displayed on the screen. The proposed structure was implemented on a personal computer for simultaneous automatic surveillance of up to 9 patients. The system was compared with standard monitors (SpaceLabs PC2), using their default alarm settings. Twenty patients undergoing cardiac surgery were studied, while we ran our system and the standard monitor simultaneously. The number of alarms triggered by each system and their accuracy and relevance were compared. Two expert observers (one physician, one engineer) ascertained each alarm reported by each system as true or false.

RESULTS

Seventy-five percent of the alarms reported by the standard monitors were false, while less than 1% of those reported by the expert system were false. Sensitivity of the standard monitors was 79% and sensitivity of the expert system was 92%. Positive predictive value was 31% for the standard monitors and 97% for the expert system.

CONCLUSIONS

Integration of information from several sources improved the reliability of alarms and markedly decreased the frequency of false alarms. Fuzzy logic may become a powerful tool for integration of physiological data.

[Minimally invasive coronary artery surgery]

BACKGROUND

There is a growing interest to perform a left internal mammary artery (LIMA) graft to the left anterior descending coronary artery (LAD) on a beating heart through a minimally invasive access to the chest cavity.

AIM

To report the experience with minimally invasive coronary artery surgery.

PATIENTS AND METHODS

Analysis of 11 patients aged 48 to 79 years old with single vessel disease that, between 1996 and 1997, had a LIMA graft to the LAD performed through a minimally invasive left anterior mediastinotomy, without cardiopulmonary bypass. A 6 to 10 cm left parasternal incision was done. The LIMA to the LAD anastomosis was done after pharmacological heart rate and blood pressure control and a period of ischemic pre conditioning. Graft patency was confirmed intraoperatively by standard Doppler techniques. Patients were followed for a mean of 11.6 months (7-15 months).

RESULTS

All patients were extubated in the operating room and transferred out of the intensive care unit on the next morning. Seven patients were discharged on the third postoperative day. Duplex scanning confirmed graft patency in all patients before discharge; in two patients, it was confirmed additionally by arteriography. There was no hospital mortality, no perioperative myocardial infarction and no bleeding problems. After follow up, ten patients were free of angina, in functional class I and pleased with the surgical and cosmetic results. One patient developed atypical angina on the seventh postoperative month and a selective arteriography confirmed stenosis of the anastomosis. A successful angioplasty of the original LAD lesion was carried out.

CONCLUSIONS

A minimally invasive left anterior mediastinotomy is a good surgical access to perform a successful LIMA to LAD graft without cardiopulmonary bypass, allowing a shorter hospital stay and earlier postoperative recovery. However, a larger experience and a longer follow up is required to define its role in the treatment of coronary artery disease.

Nutritional control of pregnant women on chronic hemodialysis

The authors describe their experience in the follow-up of four patients with chronic renal failure who became pregnant while being treated with chronic hemodialysis. The outcomes were successful and each gave birth to healthy babies. The adequate nutritional condition previous to the pregnancies added more safety to their management. Special dedication to the nutritional control enabled a good outcome of their pregnancies. It stressed the importance of the intervention of the nutritionist-dietitian in the follow-up of nephrologic patients and the integration of a multidisciplinary staff.

Estimation of ventricular volume and elastance from the arterial pressure waveform

We propose that it is possible to estimate cardiovascular parameters from the arterial pressure waveform, including ventricular maximal elastance and end-diastolic volume, if cardiac output is also known. We tested this hypothesis by means of a parameter estimation algorithm applied to simulated arterial pressure signals. The program first estimated three coefficients representing products of passive parameters from the diastolic part of the simulated arterial pressure waveform. Second, it estimated three parameter products pertaining to the ventricular function from the systolic part of the waveform. Third, mean blood flow was entered, enabling the program to compute individual parameters. This program was tested on 200 computer-generated arterial pressure signals, obtained by simulating the model with random but bounded parameters. Correlation between estimated parameters with those actually used in the simulations was excellent. Even though the value of this computer simulation is limited to the simplified model used and requires experimental validation, it demonstrates that the technique is theoretically feasible.

Renal preservation in cardiac surgery

There is no conclusive evidence that any pharmacological intervention is able to offer effective protection for the kidneys during cardiac surgery. More research is needed into the underlying mechanisms of postoperative renal failure, specifically with regard to the possible role played by endothelial factors and inflammatory response.

Renal protection in patients undergoing cardiopulmonary bypass with preoperative abnormal renal function

We prospectively studied the effects of renal protection intervention in 17 patients with preoperative abnormal renal function (plasma creatinine > 1.5 mg/dL) scheduled for elective coronary surgery. Patients were randomized to either dopamine 2.0 micrograms.kg-1.min-1 (Group 1, n = 10) or perfusion pressure > 70 mm Hg during cardiopulmonary bypass (CPB) (Group 2, n = 7). Glomerular filtration rate and effective renal plasma flow were measured with inulin and 125I-hippuran clearances before the induction of anesthesia, after sternotomy and before CPB, during hypo- and normothermic CPB, after sternal closure, and 1 h postoperatively. Plasma and urine electrolytes were measured, and free water, osmolar, and creatinine clearances, as well as fractional excretion of sodium and potassium, were calculated before and after surgery. Significant differences between groups were found before CPB for glomerular filtration rate (higher in Group 1), urine output (2.0 vs 0.29 mL/min in Group 1 versus Group 2), urinary creatinine (66 vs 175 mg/dL), urinary osmolarity (370 vs 627 mOsm/L), osmolar clearance (2.1 vs 0.7 mL/min), and urinary potassium (33 vs 71 mEq/L). There were no differences between groups during hypo- and normothermic CPB. After CPB, the only difference was a slightly higher urinary creatinine in Group 2. Renal plasma flow was lower than normal in all patients before the induction of anesthesia. A nonsignificant trend toward increased flow was seen during hypothermic CPB. Filtration fraction was high before CPB, which suggests efferent arteriolar vasoconstriction, descending toward normal during and after CPB. The same pattern of changes was present in both groups. In conclusion, there were no clinically relevant differences between the two treatment modalities during and after CPB. However, significant differences were observed before CPB, when dopamine seemed to partially revert renal vasoconstriction.

IMPLICATIONS

Two protective interventions were compared in patients undergoing heart surgery to prevent deterioration of renal function; these were dopamine infusion throughout the operation and phenylephrine infusion during cardiopulmonary bypass. We found clinically relevant differences only during surgery before cardiopulmonary bypass.

Active infective endocarditis in infants and childhood: ten-year review of surgical therapy

We review our 10-year (June 1987-June 1997) experience in 26 children requiring early surgery due to active infective endocarditis (AIE) refractory to medical therapy. Mean age at operation was 5.0 (SD 3.5) years. Nineteen patients (73%) had predisposing factors: congenital heart disease (CHD) was the most common (10/19, 53%); endocavitary foreign materials (6/19); and previous cardiac surgery (3/19). Vegetations or valve dysfunction was detected by transthoracic echocardiography in all cases but one. Valvular location (17/26, 65%) was the most common; others locations included cardiac chambers (8/26) and intravascular thoracic aorta (1/26). Bacterial isolation was achieved in 19 patients (73%): Staphylococcus (10 patients); Streptococcus (6 patients); and Candida albicans (3 patients). The indication for surgery was progressive or persistent cardiac failure (2 patients) or infection (9 patients), or a combination of these (7 patients), despite adequate medical therapy; major embolic accident with a mobile vegetation (4 patients), recurrent pulmonary embolism with a mobile vegetation (3 patients), and mobile vegetation (> 10 mm) in left cardiac chambers (1 patient). All the patients required surgery before 6 weeks of antibiotic therapy had been completed. The hospital mortality was 19% (5/26, 70% confidential limits[CL]: 2-35%). Deaths were due to infective causes in all cases but one. No late deaths occurred in 18 patients followed up for a mean of 4.2 years (SD 2.4). Three patients needed four reoperations. We conclude that improvement in the treatment of children with AIE can be obtained with an early and accurate diagnosis, an adequate antibiotic treatment, and a more aggressive surgical approach.

Arterial pressure-flow relationship in patients undergoing cardiopulmonary bypass

We determined the arterial pressure-flow relationship experimentally by means of step changes of blood flow in 30 adult patients undergoing cardiopulmonary bypass (CPB). Anesthesia technique was uniform. CPB was nonpulsatile; hypothermia to 25-28 degrees C, and hemodilution to 18%-25% hematocrit were used. During stable bypass, mean arterial pressure was recorded first with blood flow 2.2 L.min-1.m-2. Flow was then increased to 2.9 L.min-1.m-2 for 10 s and reverted to baseline for 1 min. Then it was decreased to 1.45 L.min-1.m-2 for 10 s, and reverted to baseline for 1 min. Subsequently, it was decreased to 0.73 L.min-1.m-2 for 10 s and then reverted to baseline. Similar sets of measurements were repeated after 0.25 mg of phenylephrine and once the patient was rewarmed. The pressure-flow function was individually determined by regression, and the critical pressure estimated by extrapolation to zero flow. All patients had zero-flow critical pressure during hypothermia, with a mean value of 21.8 +/- 6.4 mm Hg (range 8.8-38.9). It increased after 0.25 mg phenylephrine to 25.4 +/- 7.2 mm Hg (range 12.2-43.9, P < 0.001). During normothermia, critical pressure was 21.2 +/- 5 mm Hg (range 13.4-30.9), not significantly different from hypothermia. During hypothermia, the slope of the pressure-flow function (i.e., resistance) was 14.9 +/- 3.5 mm Hg.L-1.min-1.m-2 (range 7.6-22.1). It increased significantly (P < 0.001) after phenylephrine, to 19.7 +/- 6.2 mm Hg.L-1.min-1.m-2 (range 11.4-40.5), and returned to 15.4 +/- 3.4 mm Hg.L-1.min-1.m-2 (range 10.1-24.2) during normothermic bypass. Systemic vascular resistance appeared to vary reciprocally with blood flow, although this finding may represent a mathematical artifact, which can be avoided by using zero-flow critical pressure in the vascular resistance equation.

[Abdominal aortic aneurysm: course of morbimortality of elective surgery in 20 years]

Abdominal aortic aneurysms (AAA) usually undergo progressive dilatation and eventually may rupture, complication that carries a high mortality rate. If certain clinical conditions, like operative risk and aortic diameter are met, all patients should be considered for surgical repair. Analysis of our results with the surgical treatment of asymptomatic AAA prompted this study. Out of 479 consecutive patients operated because of AAA between 1976 and 1995, 378 (79%) were electively treated. Two decades: 1976-85 (101 patients) and 1986-95 (277 patients) were compared as far as associated medical conditions, surgical procedures, complications and mortality rate. There was no difference in age, sex, risk factors and aortic diameter. During the second decade we favoured the use of aortic tube grafts (53% vs 25%, p < 0.01) and epidural anesthesia (94% vs 35%, p < 0.01). During the last decade only 53.3% of the patients received blood transfusion, compared to 95.3% during the first period (p < 0.001). Operative mortality decreased from 5.94% to 0.72% (p < 0.05). Postoperative hospital stay diminished from 11.2 +/- 8.2 to 9.6 +/- 6.3 days (p < 0.05). These results compare favourably with those reported from other academic centers and support our therapeutic approach. Our contemporary surgical results serve as a reference for future clinical evaluation of endovascular procedures currently under investigation.

Comparison of isoflurane, halothane and fentanyl in patients with decreased ejection fraction undergoing coronary surgery

The aim of the study was to compare three anaesthetic agents in patients with ejection fraction below 0.40 subjected to coronary revascularization surgery. Twenty five elective coronary surgical patients with ejection fraction below 0.40 were prospectively studied. Premedication was pethidine 1 mg/kg and induction was fentanyl 0.03 mg/kg and pancuronium 0.1 mg/kg. The patients were randomized to one of three maintenance techniques (fentanyl, isoflurane or halothane). Radial arterial pressure, heart rate, right atrial pressure, pulmonary arterial and occluded pressures, and thermodilution cardiac output were measured, and cardiac index and resistance calculated, at the following times: before induction; 5 min after intubation; 2 min after sternotomy; immediately after discontinuation of bypass; 15 min afterwards; immediately after sternal closure; during suture of the skin; 5 min after arrival in the postoperative care unit; and 60 min postoperatively. Mean arterial pressure decreased significantly in the isoflurane group and nonsignificantly in the halothane group after induction. Cardiac index decreased significantly in the isoflurane group and nonsignificantly in the halothane group after induction and after sternotomy. Neither pressure nor flow decreased in patients receiving fentanyl. Following weaning from cardiopulmonary bypass, systemic vascular resistance decreased significantly in all groups. Cardiac index, however, did not increase above control values and arterial pressure consequently decreased; there was no significant difference between groups.

[Surgical myocardial revascularization during the 1st 15 days of evolution of acute myocardial infarction]

Revascularization significantly improves early and late prognosis in acute myocardial infarction and has prompted substantial changes in therapeutic stategies. We report 140 patients aged 60.3 years old (123 male) operated within 15 days of sustaining an acute myocardial infarction, between January 1984 and December 1989. Coronary angiogram showed single vessel disease in 8 (6%), double vessel disease in 32 (23%), triple vessel disease in 85 (61%) and left main vessel disease in 13 (9%). Indications for surgery were postinfarction angina in 92 patients (66%), multiple severe coronary stenoses in 18 (13%), infarction of less than six hours from onset in 16 (11%), acute angioplasty failure in 7 (5%) and cardiogenic shock in 7 (5%). Thirty one patients were operated during the initial 24 h of infarction (16 with less than 6 h), 14 between the second and third day and 95 between the fourth and fifteenth day. Overall mortality was 4.3% (6/140). Among patients with failed angioplasty and cardiogenic shock, mortality was 23% (7/140), among patients with postinfarction angina this figure was 2.1% (2/92). No patient operated within 6 hours of infarction onset or due to severe coronary stenosis, died. Ninety seven percent of patients were followed during mean of 49 months. Three patients had a new acute myocardial infarction, two had sudden death and two died of unrelated causes. One required angioplasty and none was reoperated. Five years actuarial survival was 95% and the actuarial probability of being free of acute myocardial infarction, angioplasty or reoperation at five years was 99 and 100% respectively. It is concluded that early surgical revascularization in cute myocardial infarction is safe and has excellent long term results.

[Retrograde cerebral perfusion during circulatory arrest with deep hypothermia. A new technique for brain protection in surgery of ascending aorta and aortic arch]

Between May 1993 and August 1994, 15 patients (10 men) with type A aortic dissection (9 acute) had a replacement of the ascending aorta and/or aortic arch with circulatory arrest with profound hypothermia and retrograde cerebral perfusion. Mean circulatory arrest time was 47.5 min (range 23 to 68 min). Three patients (20%) died in relation to postoperative bleeding. No patient had a new neurologic damage related to surgery. Ten patients were awake and oriented before 24 hours of the operation and another one before 48 hours; 4 patients required more than 48 hours to be completely awake and oriented. Two patients were operated on with a recent stroke. One of them recovered without sequelae before hospital discharge and the other one had a major regression of his brain damage. Two other patients had emergency surgery because of cardiac tamponade and cardiogenic shock. Both of them had a satisfactory recovery. Six patients presented azotemia but only 2 of them needed dialysis. There was no case of Q wave infarction nor congestive heart failure in the perioperative period. Follow-up was 100% completed (12 patients) with a mean of 9.8 months (range 5 to 18 months). One patient died on the 10th postoperative month because of a late infectious process. Eight patients are in functional class I and 3 in II. Ten of them are back to their usual activities'. Although retrograde cerebral perfusion is a new surgical technique, it seems to be a very valuable complement for brain protection in ascending aorta and/or aortic arch surgery with circulatory arrest with profound hypothermia.

Effects of extracorporeal circulation on renal function in coronary surgical patients

We prospectively studied perioperative changes of renal function in 12 previously normal patients (plasma creatinine < 1.5 mg/dL) scheduled for elective coronary surgery. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured with inulin and 125I-hippuran clearances before induction of anesthesia, before cardiopulmonary bypass (CPB), during hypo- and normothermic CPB, after sternal closure, and 1 h postoperatively. Renal and systemic vascular resistances were calculated. Urinary N-acetyl-beta-D-glucosaminidase (NAG) and plasma and urine electrolytes were measured, and free water, osmolal, and creatinine clearances, and fractional excretion of sodium and potassium were calculated before and after surgery. 125I-hippuran clearance was lower than normal in all patients before surgery. During hypothermic CPB, ERPF increased significantly (from 261 +/- 107 to 413 +/- 261 mL/min) and returned toward baseline values during normothermia. GFR was normal before and after surgery and decreased nonsignificantly during CPB. Filtration fraction was above normal before surgery and decreased significantly during CPB (0.38 +/- 0.09 to 0.18 +/- 0.06). Renal vascular resistance (RVR) was high before surgery and further increased after sternotomy (from 18,086 +/- 6849 to 30,070 +/- 24,427 dynes.s.cm-5), decreasing during CPB to 13,9647 +/- 14,662 dynes.s.cm-5. Urine NAG, creatinine, and free water clearances were normal in all patients both pre- and postoperatively. Osmolal clearance and fractional excretion of sodium increased postoperatively from 1.54 +/- 0.06 to 12.47 4/- 11.37 mL/min, and from 0.44 +/- 0.3 to 6.07 +/- 6.27, respectively. We conclude that renal function does not seem to be adversely affected by CPB.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effects of platelet-rich plasma on hemostasis and transfusion requirement in vascular surgery]

OBJECTIVE

To assess the effect of intraoperative autologous platelet-rich plasma (PRP) transfusion on haemostasis, blood loss and blood requirements during vascular surgery.

STUDY DESIGN

Randomized clinical trial.

PATIENTS

Twenty patients undergoing elective abdominal infrarenal aortic aneurysmectomy, using autologous transfusion techniques (predonation programme and/or preoperative normovolaemic haemodilution and/or intraoperative use of a cell-saver), were randomly allocated either into the PRP group (n = 10) or the Control group (n = 10).

METHOD

In patients of PRP group, 10 mL.kg-1 of PRP were obtained over 40 to 50 min, prior to induction of anaesthesia, and compensated simultaneously with an equivalent amount of hydroxyethyl starch. Each PRP unit was transfused to its donor after aortic declamping. Blood samples were obtained before induction, before incision, at wound closing and at the end of PRP unit transfusion for determination of biological variables.

RESULTS

The PRP units transfused in the patients of PRP group contained 755 +/- 117 mL of plasma with a platelet count of 62 +/- 31 G.L-1. The intra and postoperative blood losses were similar in both groups (1622 +/- 758 and 233 +/- 322 mL respectively in PRP group vs 1890 +/- 1331 and 291 +/- 303 mL respectively in Control group). In both groups, three patients required an additional transfusion of homologous blood. The results of biological tests (haematocrit, platelet and white cell counts, prothrombin time, aPTT, thrombin time, fibrinogen, D-dimers, proteins, calcium) were also similar between groups at the various times of sampling. The reinfusion of the PRP unit did not increase the platelet count.

CONCLUSIONS

This study demonstrates that intraoperative infusion of autologous PRP does not decrease blood loss and homologous transfusion requirements in patients undergoing elective abdominal infrarenal aortic aneurysmectomy. This result can be related to the relatively moderate enrichment in platelets obtained with the centrifugation speed used in this study.

Thermoregulatory vasoconstriction increases the difference between femoral and radial arterial pressures

OBJECTIVE

Thermoregulatory vasoconstriction locally increases arterial wall tension and arteriolar resistance, thereby altering physical properties of the arteries. The arterial pressure waveform is an oscillatory phenomenon related to those physical characteristics; accordingly, we studied the effects of thermoregulatory vasomotion on central and distal arterial pressures, using three hydraulic coupling systems having different dynamic responses.

METHODS

We studied 7 healthy volunteers. Central arterial pressure was measured from the femoral artery and distal pressure was measured from the radial artery, using 10.8-cm long, 20-gauge catheters. Three hydraulic coupling systems were used: (1) a 10-cm-long, 2-mm internal diameter connector; (2) a 150-cm-long, 1-mm internal diameter connector (Combidyn 520-5689, B. Braun, Melsungen, Germany); (3) a 180-cm long, 2-mm internal diameter connector (Medex MX564 and MX562, Medex Inc., Hillard, OH). Brachial artery pressure was measured oscillometrically. Core temperature was measured at the tympanic membrane. The vasomotor index, defined as finger temperature minus room temperature, divided by core temperature minus room temperature, was used to estimate the degree of vasoconstriction. Constriction was considered near maximal when the index was less than 0.1, and minimal when it exceeded 0.75. Measurements were taken every 3 min. Baseline readings were obtained when subjects were warm. They then were cooled by exposure to 20 degrees C to 22 degrees C room air and a circulating-water mattress set at 4 degrees C until index was less than 0.1. They then were rewarmed by increasing water temperature to 42 degrees C and adding a forced-air warmer until the vasomotor index exceeded 0.75. Data were analyzed by ANOVA and linear regression.

RESULTS

Thermoregulatory vasoconstriction was associated with marked arterial pressure waveform changes. Radial pressure showed, in lieu of a dicrotic notch, large oscillations of decreasing amplitude. Femoral pressure showed a single diastolic oscillation of smaller amplitude. The waveforms appeared different, depending on the hydraulic coupling system used, artifact being more marked with the longer connectors. On the average, radial systolic pressure exceeded femoral systolic pressure during vasoconstriction; however, during vasodilatation, femoral systolic pressure exceeded radial systolic pressure (p < 0.05). Oscillometric measurements underestimated systolic pressure, and did so more markedly during vasoconstriction. There were no differences in the values of mean and diastolic pressures.

CONCLUSION

Thermoregulatory vasoconstriction alters radial arterial pressure waveform, artifactually increasing its peak systolic pressure compared with the femoral artery. Poor dynamic responses of recording systems further distort the waveforms. Consequently, radial artery pressure may be misleading in vasoconstricted patients.

Renal function and cardiopulmonary bypass: effect of perfusion pressure

Controversy continues as to whether hypotension during cardiopulmonary bypass (CPB) impairs intraoperative and postoperative renal function. Therefore, 21 patients with normal renal function (plasma creatinine less than 1.2 mg/dL, creatinine clearance greater than 70 mL/min), aged 50 to 70 years, without associated pathology, scheduled for elective coronary surgery were studied prospectively. Patients were randomized into two groups: group 1 included 14 patients whose arterial blood pressure during CPB was left untreated, and group 2 consisted of 7 patients who received phenylephrine to maintain their arterial pressure above 70 mmHg. Plasma and urine creatinine, sodium, potassium, and osmolality were measured preoperatively, intraoperatively and postoperatively. Creatinine, osmolal and free water clearances, and excreted sodium fraction were calculated. Plasma creatinine remained normal throughout the study in all patients. Creatinine clearances were similar preoperatively (101.9 +/- 36.7 in group 1 and 120.6 +/- 50.7 mL/min in group 2). In group 1, creatinine clearance decreased during CPB to 88.7 +/- 39.7 mL/min, whereas in group 2 it increased to 157.6 +/- 79.5 mL/min; the difference between groups was significant. Early postoperatively, there was no difference: 136.2 +/- 86.6 mL/min in group 1 and 100 +/- 21.4 mL/min in group 2. One week postoperatively, values were 100.5 +/- 37.9 and 101.9 +/- 18.4, respectively. There was a significant correlation between the creatinine clearance and perfusion pressure intraoperatively, but not postoperatively. Osmolal clearance also correlated with perfusion pressure intraoperatively, but it was significantly lower in the phenylephrine group postoperatively. Postoperative renal function was normal in all patients; no deleterious effect of a low arterial pressure during bypass could be identified.

Anesthesia for elective cardioversion: a comparison of four anesthetic agents

Elective cardioversion is a short procedure performed under general anesthesia for the treatment of cardiac dysrhythmias. Selection of the anesthetic agent is important, because a short duration of action and hemodynamic stability are required. Forty-four patients scheduled for elective cardioversion in the coronary care unit were studied prospectively. All patients were randomly assigned, according to the last digit of their clinical record number, to receive one of the four anesthetic agents studied: group 1, 12 patients who received 3 mg/kg of sodium thiopental; group 2, 10 patients who received 0.15 mg/kg of etomidate; group 3, 12 patients who received 1.5 mg/kg of propofol; and group 4, 10 patients who received 0.15 mg/kg of midazolam. All patients also received 1.5 micrograms/kg of fentanyl 3 minutes before induction. All four drugs provided satisfactory anesthesia for cardioversion and there were no major complications. Midazolam produced a more prolonged duration of effect and more interindividual variability. Propofol was associated with hypotension and a higher incidence of apnea, and its duration of action was similar to that of etomidate or thiopental. Etomidate produced myoclonus and pain on injection; however, it was the only agent that did not decrease arterial blood pressure. Thiopental reduced blood pressure but otherwise seemed an appropriate anesthetic for this procedure. In conclusion, all four anesthetic agents were acceptable for cardioversion, although their pharmacological differences suggest specific indications for individual patients.