Assessment of Spinal Cord Ischemia With Near-Infrared Spectroscopy: Myth or Reality?

Non-invasive near-infrared spectroscopy is gaining popularity in the detection of spinal cord ischemia following aortic aneurysm repair. However, practical recommendations are lacking. This review focuses on the physiological and anatomical background, as well as on the clinical implementations of near-infrared spectroscopy as a tool for monitoring ischemia of the spinal cord. Clinical recommendations based on the currently available evidence are rendered.

Influence of variations in systemic blood flow and pressure on cerebral and systemic oxygen saturation in cardiopulmonary bypass patients.

BACKGROUND: Although both pressure and flow are considered important determinants of regional organ perfusion, the relative importance of each is less established. The aim of the present study was to evaluate the impact of variations in flow, pressure, or both on cerebral and whole-body oxygen saturation. METHODS: Thirty-four consenting patients undergoing elective cardiac surgery on cardiopulmonary bypass were included. Using a randomized cross-over design, four different haemodynamic states were simulated: (i) 20% flow decrease, (ii) 20% flow decrease with phenylephrine to restore baseline pressure, (iii) 20% pressure decrease with sodium nitroprusside (SNP) under baseline flow, and (iv) increased flow with baseline pressure. The effect of these changes was evaluated on cerebral (Sc(O2)) and systemic (Sv(O2)) oxygen saturation, and on systemic oxygen extraction ratio (OER). Data were assessed by within- and between-group comparisons. RESULTS: Decrease in flow was associated with a decrease in [from 63.5 (7.4) to 62.0 (8.5) %, P<0.001]. When arterial pressure was restored with phenylephrine during low flow, Sc(O2) further decreased from 61.0 (9.7) to 59.2 (10.2) %, P<0.001. Increase in flow was associated with an increase in Sc(O2) from 62.6 (7.7) to 63.6 (8.9) %, P=0.03, while decreases in pressure with the use of SNP did not affect Sc(O2). Sv(O2) was significantly lower (P<0.001) and OER was significantly higher (P<0.001) in the low flow arms. CONCLUSIONS: In the present elective cardiac surgery population, Sc(O2) and Sv(O2) were significantly lower with lower flow, regardless of systemic arterial pressure. Moreover, phenylephrine administration was associated with a reduced cerebral and systemic oxygen saturation.

Relation between mixed venous oxygen saturation and cerebral oxygen saturation measured by absolute and relative near-infrared spectroscopy during off-pump coronary artery bypass grafting.

BACKGROUND: We hypothesized that previously reported contradictory results regarding the equivalence of mixed venous (Smv(O(2))) and cerebral (rS(c)O(2)) oxygen saturation might be related to time delay issues and to measurement technology. In order to explore these two factors, we designed a prospective clinical study comparing with relative (INVOS(®)) and absolute (Foresight(®)) rS(c)O(2) measurements. METHODS: Forty-two consenting patients undergoing elective off-pump coronary artery bypass grafting were included. Two INVOS and two Foresight sensors continuously registered rS(c)O(2). Smv(O(2)) was measured continuously via a pulmonary artery catheter. Data were assessed by within- and between-group comparisons and correlation analysis. RESULTS: A similar time delay of 19 (4) and 18 (4) s was found for compared with rS(c)O(2) measurements by Foresight and INVOS, respectively, during haemodynamic changes. After adjusting for this time delay, the correlation between Smv(O(2)) and rS(c)O(2) increased from r=0.25 to 0.75 (P<0.001) for Foresight, and from r=0.28 to 0.73 (P<0.001) for INVOS. Comparison of Foresight and INVOS revealed significant differences in absolute rS(c)O(2) values (range 58-89% for Foresight and 28-95% for INVOS). Changes in rS(c)O(2) in response to acute haemodynamic alterations were significantly more pronounced with INVOS compared with Foresight (P<0.001). CONCLUSIONS: Considering the important time delay with Smv(O(2)), rS(c)O(2) seems to reflect more appropriately acute haemodynamic alterations. This might suggest its use as a valid alternative to invasive monitoring of tissue oxygen saturation. Relative and absolute rS(c)O(2) measurements demonstrated significant differences in measured rS(c)O(2) values and in the magnitude of rS(c)O(2) changes during haemodynamic alterations.

Randomised clinical trial: the synbiotic food supplement Probiotical vs. placebo for acute gastroenteritis in children.

BACKGROUND: Some probiotic strains reduce the duration of acute diarrhoea. As a result of strain and product specificity, each product needs support by clinical data. AIM: In children with acute diarrhoea, to test the efficacy of the synbiotic food supplement Probiotical (Streptoccoccus thermophilus, Lactobacillus rhamnosus, Lactobacillus acidophilus, Bifidobacterium lactis, Bifidobacterium infantis, fructo-oligosaccharides). The primary end-points were duration of diarrhoea and the number of children that had a normalised stool consistency. METHOD: A total of 111 children with acute diarrhoea (median age 40 months) were included in this randomised, prospective placebo-controlled parallel clinical trial in primary health care. All children were treated with oral rehydration solution ad libitum and with the synbiotic (n=57) or placebo (n = 54). RESULTS: The median duration of diarrhoea was 3 days (IQ 25-75: 2-4 days) in the Probiotical group, compared with 4 days (IQ 25-75: 4-5 days) in the placebo group (P<0.005). The number of children with normal stool consistency (defined as stool Bristol score ≤4) was higher in the synbiotic group on days 2 and 3 [21 vs. 2% (P<0.001) and 50 vs. 24% (P<0.001) respectively]. Less additional medication (antipyretics, antiemetics, antibiotics) was administered in the synbiotic group. Physicians were globally more satisfied with the synbiotic food supplement treatment than with placebo (P=0.005). One patient in the placebo group was hospitalised. CONCLUSION: The median duration of diarrhoea was significantly 1 day shorter in the synbiotic than in the placebo group, associated with decreased prescription of additional medications.

Occupational exposure to sevoflurane during cardiopulmonary bypass.

Volatile anaesthetic agents are widely used for maintenance of anaesthesia in all kinds of surgical procedures. Despite the implementation of measures such as adequate ventilation of the operating room and the use of efficient scavenging systems, concern remains about the risks for occupational exposure, especially in situations associated with an increased risk of anaesthetic gas waste, such as with the use of volatile anaesthetic agents on cardiopulmonary bypass. The present contribution reports the results of a preliminary safety assessment involving measurements of sevoflurane concentrations in the ambient air of a cardiac surgery operating room. In 22 cardiac surgical procedures with cardiopulmonary bypass (11 with open and 11 with closed venous reservoir), measurements of trace concentrations were obtained every 10 min at the following sites: at the outlet of the oxygenator, at the outlet of the cardiotomy reservoir, in the breathing zone of the perfusionist and above the surgical field. The concentrations were measured on-line using a photoacoustic infrared spectrometer. Mean sevoflurane waste concentrations remained consistently below the recommended target value of 4.68 ppm throughout the observation period at the different measurement sites. These results indicate that, with the use of sevoflurane on cardiopulmonary bypass, the recommended levels for occupational exposure are not exceeded, provided adequate operation room ventilation and waste gas scavenging is performed.

Percutaneous implantation of the CoreValve aortic valve prosthesis in patients at high risk or rejected for surgical valve replacement: Clinical evaluation and feasibility of the procedure in the first 30 patients in the AMC-UvA.

Objective. To report the feasibility, safety and efficacy of percutaneous aortic valve implantation (PAVI) with the CoreValve self-expanding aortic valve bioprosthesis in elderly patients with aortic valve stenosis who are rejected for surgery or have a high surgical risk.Methods. PAVI using the CoreValve ReValving System was performed under general anaesthesia in 30 high-risk (surgical) patients with a symptomatic severe aortic valve stenosis.Results. The patients had a mean age of 80.5+/-7.7 years, a mean aortic valve area of 0.71+/-0.19 cm(2), a peak transvalvular aortic gradient of 79+/-25 mmHg, as measured with echo Doppler, a logistic EuroSCORE of 15+/-10% and a Society of Thoracic Surgeons (STS) score of 5.2+/-2.9%. Device success was achieved in all patients and acute procedural success in 27 patients (90%). In the surviving patients, there was in a reduction of the peak aortic pressure gradient from 76+/-24 mmHg to 22+/-7 mmHg (n=24, p<0.00001) 30 days after successful device implantation. At 30 days, major adverse cardiovascular and cerebral events had occurred in seven patients (23%). This included mortality in six patients (20%), of which one death was cardiovascular. The other five non-cardiovascular deaths involved two patients who died of an exacerbation of severe pre-existent pulmonary disease and three of infectious complications.Conclusions. Percutaneous aortic valve implantation was successfully performed in our centre in highrisk patients, with a 30-day mortality of 20%. When successful, marked haemodynamic improvement and relief of symptoms was achieved. (Neth Heart J 2010;18:18-24.).

Effects of moderate acute isovolaemic haemodilution on myocardial function in patients undergoing coronary surgery under volatile inhalational anaesthesia.

When myocardial oxygen demand is increased by elevated heart rate in patients undergoing coronary artery surgery under total intravenous anaesthesia, acute isovolaemic haemodilution may be associated with a deterioration of cardiac function. We investigated the effects of acute isovolaemic haemodilution during volatile inhalational anaesthesia. Forty patients undergoing coronary surgery were randomly assigned to two groups according to the rate of atrioventricular pacing (Group 70 at 70.min(-1) and Group 90 at 90.min(-1)). While paced at the fixed heart rate, acute isovolaemic haemodilution was performed before the start of cardiopulmonary bypass. In both groups mean (SD) stroke volume increased with haemodilution (from 65 (9) to 83 (10) ml.min(-1) (p < 0.01) in Group 70 and from 65 (9) to 81 (9) ml.min(-1) (p < 0.01) in Group 90) as a result of a decrease in systemic vascular resistance (from 1175 (231) to 869 (164) dynes.s.cm(-5) (p < 0.01) and from 1060 (185) to 849 (146) dynes.s.cm(-5) (p < 0.01), respectively) and an increase in end-diastolic volume (from 1049 (234) to 1405 (211) ml (p < 0.01) and from 1078 (106) to 1438 (246) ml (p < 0.01), respectively). Left ventricular pressure-derived data remained unchanged with acute isovolaemic haemodilution in both groups.

Cardioprotection in anesthesia.

Ischemic heart disease is the major cause of morbidity and mortality in the Western world. With the advancing age of the surgical population, anesthesiologists increasingly have to treat patients with known or suspected ischemic heart disease in the perioperative period. Over the years various strategies have been developed to prevent myocardial ischemia in the perioperative period and/or to minimize the extent of myocardial damage after perioperative ischemia. This review summarizes the current knowledge on the subject and focuses on the more recent data concerning perioperative cardioprotection by anesthetic agents.

Does the use of a volatile anesthetic regimen attenuate the incidence of cardiac events after vascular surgery?

OBJECTIVE: To compare the effects of a volatile anesthetic to a non-volatile anesthetic regimen on the incidence of postoperative cardiac events, including the postoperative elevation of troponin I values after arterial vascular surgery in high risk patients. DESIGN: Retrospective analysis of data of a phase II study that compared the Na+/H+ exchanger type II inhibitor, zoniporide to placebo on the occurrence of cardiac events. SETTING: Multicenter study conducted in 105 sites throughout the United States, South America, Europe and Asia. PARTICIPANTS: 784 subjects scheduled for urgent or elective major arterial vascular surgery and a history of at least 3 of the following: age > or = 65 years, hypertension, documented stroke or transient ischemic attack, previous myocardial infarction, active angina pectoris diabetes mellitus, congestive heart failure, or symptomatic cardiac arrhythmia. INTERVENTIONS: Type of anesthesia was retrospectively retrieved from the database and patients were subdivided in two groups: inhalational (group A) vs non-inhalational anesthetic regimen (group B). Incidence of postoperative cardiac events was compared between the two groups. MEASUREMENTS AND MAIN RESULTS: The incidence of postoperative cardiac events was not different between the two groups. Maximum postoperative troponin I levels was not different between the two groups in the total population and in the patients undergoing peripheral arterial surgery. In patients undergoing aortic surgery the incidence of elevated troponin levels higher than 1.5 and 4 ng x mL(-1) tended to be lower in group A than in group B in the aortic surgery (28% vs 18% and 30% vs 20% respectively) but this difference did not reach statistical significance. CONCLUSION: The results of this hypothesis-generating study suggest that potential beneficial effects on extent of postoperative myocardial damage in high risk patients undergoing arterial surgery will probably be more apparent in abdominal aortic surgery than in peripheral vascular surgery. Further sufficiently powered studies using a standardized protocol should now be performed to definitively address this question.

Continuous cardiac output measurement: arterial pressure analysis versus thermodilution technique during cardiac surgery with cardiopulmonary bypass.

This study compared cardiac output measured with an arterial pressure-based cardiac output measurement system and a thermodilution cardiac output measurement system. We studied 36 patients undergoing cardiac surgery with cardiopulmonary bypass. Simultaneous arterial pressure-based and thermodilution cardiac output measurements were compared before and after cardiopulmonary bypass, and after phenylephrine administration. Bland-Altman analysis showed good overall agreement between the two methods. Bias (limits of agreement) before and after cardiopulmonary bypass were - 0.21 (- 2.97-2.55) lxmin(-1) and 0.01 (- 3.79-3.81) lxmin(-1), respectively. Phenylephrine administration decreased thermodilution cardiac output by a mean (SD) of 11 (16)% and increased arterial pressure-based cardiac output by 55 (34)%. We conclude that arterial pressure-based cardiac output and thermodilution cardiac output measurement systems yield comparable results during cardiac surgery with cardiopulmonary bypass. However, after phenylephrine administration, the two measurement systems provided opposing results.

Cardiac surgery with cardiopulmonary bypass: does aprotinin affect outcome?

BACKGROUND: Aprotinin, a non-specific serine protease inhibitor, has been used for two decades to reduce perioperative blood loss and the risk for allogeneic transfusion in cardiac surgery. This study evaluated the effects of aprotinin on outcome (mortality, cardiac events, renal failure, and cerebrovascular events) in such patients undergoing cardiac surgery with cardiopulmonary bypass. METHODS: Data were obtained in patients who received a strict blood conservation protocol: no antifibrinolytic therapy when at low risk (n = 854) and aprotinin (n = 1210) when at high risk for blood transfusion. Relative risk of different pre- and intra-operative variables was calculated for the different outcome variables. Backward stepwise logistic regression analysis was used to identify the independent risk factors associated with the different outcome variables. Statistical significance was accepted at P < 0.01. RESULTS: Postoperative mortality and morbidity were higher in the aprotinin group but this was related to an increased incidence of perioperative risk factors. Mortality was similar to that predicted by the Euroscore. Complex surgery was the only independent variable associated with postoperative cardiac events. Preoperative heart failure, preoperative creatinine > 1.5 mg dl(-1), urgent, and redo surgery were the independent variables associated with postoperative haemodialysis. Age > 70 yr was identified as the only independent variable associated with neurologic dysfunction. CONCLUSIONS: In the present study, patients receiving aprotinin as part of a strict blood conservation strategy represent a population at high risk for postoperative complications. For the outcome variables studied, aprotinin administration was not identified as an independent risk factor.

Closure of the cribriform fascia: an efficient anatomical barrier against postoperative neovascularisation at the saphenofemoral junction? A prospective study.

BACKGROUND: Neovascularisation at the sapheno-femoral junction (SFJ) ligation site in the groin may occur within one year after great saphenous vein (GSV) surgery. Several anatomical and prosthetic barrier techniques have been proposed to prevent this evolution. OBJECTIVE: A prospective study examined whether closing the cribriform fascia could reduce the incidence of postoperative neovascularisation in the groin. PATIENTS AND METHODS: Patients with primary varicose veins and incompetence at the level of the SFJ were included. After SFJ ligation in 235 limbs of 193 patients an anatomical barrier was constructed by closing the cribriform fascia. Postoperative duplex scanning was performed after 2 and 12 months. Results were compared with historical control groups in which either a silicone patch saphenoplasty or no barrier technique had been performed. RESULTS: After one year, 10 limbs had developed recurrent thigh varicose veins and duplex scan showed neovascularisation at the SFJ ligation site in 15 of 223 re-examined limbs (6.7%). This was comparable to the group of 191 limbs with silicone patch saphenoplasty (5.2%) (P=0.526) and superior to the group of 189 limbs without barrier (14.8%) (P<0.01). CONCLUSION: Interposition of an anatomical barrier by closing the cribriform fascia after SFJ ligation reduced ultrasound detected neovascularisation at the SFJ after one year. In primary varicose vein operations application of an anatomical barrier technique (without prosthetic patch) is an alternative option to prevent postoperative neovascularisation.

Critical oxygen delivery during cardiopulmonary bypass in dogs: pulsatile vs. non-pulsatile blood flow.

BACKGROUND AND OBJECTIVE: To determine the minimal oxygen delivery and pump flow that can maintain systemic oxygen uptake during normothermic (37 degrees C) pulsatile and non-pulsatile cardiopulmonary bypass in dogs. METHODS: Eighteen anaesthetized dogs were randomly assigned to receive either non-pulsatile (Group C; n = 9) or pulsatile bypass flow (Group P; n = 9). Oxygen delivery was reduced by a progressive decrease in pump flow, while arterial oxygen content was maintained constant. In each animal, critical oxygen delivery was determined from plots of oxygen uptake vs. oxygen delivery and from plots of blood lactate vs. oxygen delivery using a least sum of squares technique. Critical pump flow was determined from plots of lactate vs. pump flow. RESULTS: At the critical point, oxygen delivery obtained from oxygen uptake was 7.7 +/- 1.1 mL min(-1) kg(-1) in Group C and 6.8 +/- 1.8 mL min(-1) kg(-1) in Group P (n.s.). These values were similar to those obtained from lactate measurements (Group C: 7.8 +/- 1.6 mL min(-1) kg(-1); Group P: 7.6 +/- 2.0 mL min(-1) kg(-1)). Critical pump flows determined from lactate measurements were 55.6 +/- 13.8 mL min(-1) kg(-1) in Group C and 60.8 +/- 13.9 mL min(-1) kg(-1) in Group P (n.s.). CONCLUSIONS: Oxygen delivery values greater than 7-8 mL min(-1) kg(-1) were required to maintain oxygen uptake during normothermic cardiopulmonary bypass with either pulsatile or non-pulsatile blood flow. Elevation of blood lactate levels during bypass helps to identify inadequate tissue oxygen delivery related to insufficient pump flow.

Incidence of atrial fibrillation early after cardiac surgery: can choice of the anesthetic regimen influence the incidence?

Occurrence of atrial fibrillation is a common complication after coronary surgery. This study aimed to identify the perioperative factors that are associated with its occurrence with specific attention to the possible influence of the choice of the anesthetic regimen after elective coronary surgery. A retrospective chart analysis was performed in 460 patients who underwent elective coronary artery surgery with cardiopulmonary bypass using the standard institutional anesthetic, surgical and postoperative protocols. The only difference in management was the choice of the primary anesthetic regimen. 110 patients had a total intravenous anesthesia with propofol, 90 patients had a total intravenous anesthesia with midazolam, 150 patients were anesthetized with sevoflurane and 110 patients with desflurane. The primary outcome variable was the incidence of atrial fibrillation within the first 24 postoperative hours. Atrial fibrillation occurred in 64 of the 460 patients included (13.9%). Multiple logistic regression analysis identified increased age (> 70 years), EuroSCORE > 4, prolonged CPB time (> 100 min) and need for prolonged inotropic support (> 6 hours) as the significant independent risk factors for the occurrence of postoperative atrial fibrillation. The incidence of postoperative atrial fibrillation differed among the different anesthetic groups with the lowest incidence in the sevoflurane group (propofol: 17/110; midazolam: 15/90; sevoflurane: 9/150; desflurane: 23/110) (p = 0.004). This finding should be further confirmed in a prospective sufficiently powered multicenter study.

Effects of postural changes on cardiac function in healthy subjects.

AIMS: To analyse the response of Doppler measurements to increased venous return in middle-aged healthy subjects. METHODS AND RESULTS: Left ventricular pulsed Doppler parameters, colour M-mode of early left ventricular filling and septal mitral annulus velocities were measured at baseline and after leg lifting (n=24). Leg lifting resulted in increased stroke volume (69 +/- 14 to 74 +/- 14 ml, P<0.01) and peak systolic annulus velocity (6.8 +/- 1.3 to 7.3 +/- 1.1 cm/s, P<0.01). Leg lifting enhanced peak early (E) mitral flow (74 +/- 13 to 80 +/- 14 cm/s, P<0.01), flow propagation (53 +/- 10 to 59 +/- 13 cm/s, P<0.01) and E' diastolic mitral annulus velocity (10.8 +/- 2.2 to 11.7 +/- 2.0 cm/s, P<0.01). There was a shortening of E wave deceleration time (178 +/- 27 to 163 +/- 27 ms, P<0.01) and isovolumic relaxation time (76 +/- 11 to 68 +/- 10 ms, P<0.01). However, individual changes in Doppler parameters differed among subjects. CONCLUSIONS: Leg lifting improved myocardial function as manifested by increase in stroke volume, systolic annulus motion and acceleration of relaxation. Flow propagation velocity and diastolic mitral annulus velocities were influenced by the induced change in cardiac preload as well.

The negative inotropic effect of sevoflurane is not mediated through nitric oxide synthase in rat papillary muscle.

Sevoflurane has dose-dependent negative inotropic effects on myocardial contractility. The current study investigated whether the nitric oxide pathway is involved in these effects. A laboratory, ex-vivo experiment was performed on 66 isolated papillary muscles. Effects of increasing concentrations of sevoflurane (1, 2 and 3 MAC) were assessed in control conditions, in the presence of Nw-nitro-L-arginine (L-NOARG) and in beta-adrenergic stimulated rat papillary muscles. Contractility was assessed by total developed tension. In baseline conditions, the administration of increasing concentrations of sevoflurane caused a dose-dependent reduction in contractility of respectively 8.6 +/- 1.7%, 14.4 +/- 4.8% and 23.6 +/- 3.9%. This negative inotropic effect was not significantly altered by the administration of the NO-synthase inhibitor L-NOARG (p = 0.09). Under continuous administration of 3 MAC sevoflurane, 4 consecutive concentrations of isoproterenol induced a mean increase of contractility of respectively 43.0 +/- 13.7%, 65.9 +/- 22.6%, 131.2 +/- 25.6% and 122.3 +/- 31.2%. After administration of L-NOARG, the 4 consecutive concentrations of isoproterenol induced a mean increase in contractility of respectively 36.0 +/- 8.5%, 75.0 +/- 17.8%, 143.0 +/- 42.8% and 120.0 +/- 51.4% (p = 0.85). These data indicated that the negative inotropic effects of sevoflurane in rat papillary muscles, both in basic as in beta-adrenergic stimulated conditions, were not altered by blocking the NO-cGMP-system.

Effect of preoperative beta-blockade on perioperative mortality in coronary surgery.

BACKGROUND: Many preoperative factors can influence perioperative mortality in cardiac surgery. Because the perioperative use of beta-blocking agents may reduce perioperative cardiac complications in non-cardiac surgery, we considered the possibility that beta-blocking agents could improve survival in coronary surgery patients. METHODS: In a retrospective study on 1586 patients undergoing coronary bypass surgery, the relative risk of 30-day mortality was determined in relation to preoperative risk factors and medication. Factors included patient characteristics, pre-existing illness, specific cardiovascular risk factors, cardiac status and urgency of surgery. Treatment with beta-blocking agents, calcium antagonists, angiotensin-converting enzyme inhibitors, nitrates, anti-arrhythmic agents, diuretics and antithrombotic agents was taken into account. RESULTS: Sex, age, chronic obstructive pulmonary disease, urgency and the preoperative use of diuretics and chronic beta-blocking therapy were found to be linked to mortality (P<0.05). Backward stepwise regression testing identified age, urgency and beta-blocking therapy as independent factors that could predict mortality. CONCLUSIONS: Increasing age and urgency of surgery are associated with greater mortality, whereas preoperative beta-blocking therapy is associated with less mortality. The characteristics of patients who received chronic beta-blockade did not differ significantly from those of patients who did not. The results suggest that chronic preoperative beta-blocker therapy reduces 30-day mortality in coronary surgery.