Regional cerebral oxygen saturation during cardiopulmonary resuscitation as a predictor of return of spontaneous circulation and favourable neurological outcome - A review of the current literature

INTRODUCTION

Regional cerebral oxygen saturation (rSO2) can be measured non-invasively even at no- or low-flow states. It thus allows assessment of brain oxygenation during CPR. Certain rSO2 values had been associated with return of spontaneous circulation (ROSC) and neurological outcome in the past. Clear-cut thresholds for the prediction of beneficial outcome, however, are still lacking.

METHODS

We conducted a database search to extract all available investigations on rSO2 measurement during CPR. Mean, median, and ΔrSO2 values were either taken from the studies or calculated. Thresholds for the outcome "ROSC" and "neurological outcome" were sought.

RESULTS

We retrieved 26 publications for the final review. The averaged mean rSO2 for patients achieving ROSC was 41 ± 12% vs. 30 ± 12% for non-ROSC (p = .009). ROSC was not observed when mean rSO2 remained <26%. In ROSC patients, ΔrSO2 was 22 ± 16% vs. 7 ± 10% in non-ROSC patients (p = .009). A rSO2 threshold of 36% predicted ROSC with a sensitivity of 67% and specificity of 69% while ΔrSO2 of 7% showed a sensitivity of 100% and a specificity of 86% (AUC = 0.733 and 0.893, respectively). Mean rSO2 of 47 ± 11% was associated with favourable and 38 ± 12% with poor neurological outcome. There was, however, a great overlap between groups due to scarce data.

CONCLUSION

Higher rSO2 consistently correlated with increased rates of ROSC. The discriminatory power of rSO2 to prognosticate favourable neurological outcome remains unclear. Measuring rSO2 during CPR could potentially facilitate clinical decision-making.

A pilot study on reparixin, a CXCR1/2 antagonist, to assess safety and efficacy in attenuating ischaemia-reperfusion injury and inflammation after on-pump coronary artery bypass graft surgery

Reparixin, a CXCR 1/2 antagonist, has been shown to mitigate ischaemia-reperfusion injury (IRI) in various organ systems in animals, but data in humans are scarce. The aim of this double-blinded, placebo-controlled pilot study was to evaluate the safety and efficacy of reparixin to suppress IRI and inflammation in patients undergoing on-pump coronary artery bypass grafting (CABG). Patients received either reparixin or placebo (n = 16 in each group) after induction of anaesthesia until 8 h after cardiopulmonary bypass (CPB). We compared markers of systemic and pulmonary inflammation, surrogates of myocardial IRI and clinical outcomes using Mann-Whitney U- and Fisher's exact tests. Thirty- and 90-day mortality was 0% in both groups. No side effects were observed in the treatment group. Surgical revision, pleural and pericardial effusion, infection and atrial fibrillation rates were not different between groups. Reparixin significantly reduced the proportion of neutrophil granulocytes in blood at the beginning [49%, interquartile range (IQR) = 45-57 versus 58%, IQR = 53-66, P = 0·035], end (71%, IQR = 67-76 versus 79%, IQR = 71-83, P = 0·023) and 1 h after CPB (73%, IQR = 71-75 versus 77%, IQR = 72-80, P = 0·035). Reparixin patients required a lesser positive fluid balance during surgery (2575 ml, IQR = 2027-3080 versus 3200 ml, IQR = 2928-3778, P = 0·029) and during ICU stay (2603 ml, IQR = 1023-4288 versus 4200 ml, IQR = 2313-8160, P = 0·021). Numerically, more control patients required noradrenaline ≥ 0·11 μg/kg/min (50 versus 19%, P = 0·063) and dobutamine (50 versus 25%, P = 0·14). Therefore, administration of reparixin in CABG patients appears to be feasible and safe. It concurrently attenuated postoperative granulocytosis in peripheral blood.

Ventilation during cardiopulmonary bypass: impact on heat shock protein release

AIM

Cardiopulmonary bypass (CPB), utilized in on-pump coronary artery bypass graft procedures (CABG) induces generalized immune suppression, release of heat shock proteins (HSP), inflammatory markers and apoptosis-specific proteins. We hypothesized that continued mechanical ventilation during cardiopulmonary bypass attenuates immune response and HSP liberation.

METHODS

Thirty patients undergoing conventional coronary artery bypass graft (CABG) operation were randomized into a ventilated on CPB (VG; N.=15) and a non-ventilated CPB group (NVG; N.=15). Blood samples were drawn at the beginning and end of surgery, as well as on the five consecutive postoperative days (POD). Molecular markers were measured by ELISA. Data are given as mean ± (SD). Mann-Whitney-U-test was used for statistical analysis.

RESULTS

Serum concentrations of HSP70 were significantly lower in VG compared to NVG on POD-1 (VG: 1629±608 vs. NVG: 5203±2128.6 pg/mL, P<0.001). HSP27 and HSP60 depicted a minor increase in both study groups at the end of surgery without any intergroup differences (HSP27: VG 6207.9±1252.5 vs. NVG 7424.1±2632.5; HSP60: VG 1046.2±478.8 vs. NVG 1223.5±510.1). IL-8 and CK-18 M30 evidenced the highest serum concentrations at the end of surgery (IL-8: VG 119.5±77.9 vs. NVG 148.0±184.55; CK-18 M30: VG 62.1±39.2 vs. NVG 67.5±33.9) with no differences between groups. Decreased ICAM-1 serum concentrations were detected postoperatively, however ICAM-1 concentrations on POD-1 to POD-5 showed slightly elevated concentrations in both study groups with no intergroup differences.

CONCLUSION

Significantly less HSP70 was detectable in patients receiving uninterrupted mechanical lung ventilation on CPB, indicating either different inflammatory response, cellular stress or cell damage between the ventilated and non-ventilated group. These data suggest that continued mechanical ventilation has a modulatory effect on the immune response in patients after CABG surgery.

Comparison of the effects of albumin 5%, hydroxyethyl starch 130/0.4 6%, and Ringer's lactate on blood loss and coagulation after cardiac surgery

BACKGROUND

Infusion of 5% human albumin (HA) and 6% hydroxyethyl starch 130/0.4 (HES) during cardiac surgery expand circulating volume to a greater extent than crystalloids and would be suitable for a restrictive fluid therapy regimen. However, HA and HES may affect blood coagulation and could contribute to increased transfusion requirements.

METHODS

We randomly assigned 240 patients undergoing elective cardiac surgery to receive up to 50 ml kg(-1) day(-1) of either HA, HES, or Ringer's lactate (RL) as the main infusion fluid perioperatively. Study solutions were supplied in identical bottles dressed in opaque covers. The primary outcome was chest tube drainage over 24 h. Blood transfusions, thromboelastometry variables, perioperative fluid balance, renal function, mortality, intensive care unit, and hospital stay were also assessed.

RESULTS

The median cumulative blood loss was not different between the groups (HA: 835, HES: 700, and RL: 670 ml). However, 35% of RL patients required blood products, compared with 62% (HA) and 64% (HES group; P=0.0003). Significantly, more study solution had to be administered in the RL group compared with the colloid groups. Total perioperative fluid balance was least positive in the HA group [6.2 (2.5) litre] compared with the HES [7.4 (3.0) litre] and RL [8.3 (2.8) litre] groups (P<0.0001). Both colloids affected clot formation and clot strength and caused slight increases in serum creatinine.

CONCLUSIONS

Despite equal blood loss from chest drains, both colloids interfered with blood coagulation and produced greater haemodilution, which was associated with more transfusion of blood products compared with crystalloid use only.

Paraoperative change of sleep-disordered breathing in healthy snorers and sleep apnea patients compared to preoperative values

BACKGROUND

Patients with sleep-disordered breathing often show upper airway narrowing due to anatomical factors, which can be treated surgically. The paraoperative risk for sleep apnea patients is discussed from different points of view. We studied the effects of general anesthesia which is mainly used for surgery on the degree of disordered breathing.

METHODS

After two nights of polysomnographie 20 healthy subjects with snoring, light or severe sleep apnea were scheduled for surgery of the nose, the paranasal sinuses, the tonsils and/or the soft palate. A common screening device for disordered breathing was installed preoperatively. The raw data for snoring, oxygen saturation, heart rate and body position were edited visually in order to match them with polysomnography. Preoperative results were compared to the four hours following extubation and the first postoperative night.

RESULTS

Neither the respiratory disturbance indexes (RDI) nor the oxygen saturations nor the times of snoring differed significantly during the three examinations. Worsening was only found in the subgroup with predominantly mixed apnea. There was only one patient with a modified uvulo-palato-pharyngoplasty(UPPP) who had to be reintubated twelve hours after surgery due to massive oropharyngeal swelling. Patients without palatal surgery did not show any complications.

CONCLUSION

According to our experience surgically treated sleep apnea patients without any other cardiopulmonary disease may be kept in the general ENT ward. After oropharyngeal surgery intensive wound controls are required.

Direct mapping of nuclear shell effects in the heaviest elements

Quantum-mechanical shell effects are expected to strongly enhance nuclear binding on an "island of stability" of superheavy elements. The predicted center at proton number Z = 114, 120, or 126 and neutron number N = 184 has been substantiated by the recent synthesis of new elements up to Z = 118. However, the location of the center and the extension of the island of stability remain vague. High-precision mass spectrometry allows the direct measurement of nuclear binding energies and thus the determination of the strength of shell effects. Here, we present such measurements for nobelium and lawrencium isotopes, which also pin down the deformed shell gap at N = 152.

Influenza A-induced cardiogenic shock requiring temporary ECMO support and urgent heart transplantation

We report a case of a child with familial cardiomyopathy who contracted H1N1 influenza followed by cardiovascular collapse requiring immediate arteriovenous ECMO support. Despite the lack of experience with heart transplantation (HTx) soon after H1N1 infection, HTx was considered as an exit strategy since restoration of cardiac function was considered unlikely. In contrast to the most common indication for ECMO use in patients with H1N1 infection, early ECMO support in cases with infection-induced myocardial decompensation may be lifesaving. Additionally, this report shows that urgent heart transplantation in a patient on ECMO support can be performed safely after recent H1N1 infection and simultaneous heparin-induced thrombocytopenia, which has not been reported before. This case also indicates that H1N1 vaccination should be considered for potential transplantation candidates to prevent severe infection.

Secretion of soluble ST2 - possible explanation for systemic immunosuppression after heart surgery

BACKGROUND

Cardiopulmonary bypass is known to affect cytokine release leading to a generalized endogenous immune reaction similar to that described in sepsis, without having been explored in great detail. Therefore we evaluated the anti- and pro-inflammatory cytokine responses after heart surgery.

METHODS

16 patients who underwent coronary artery bypass graft (CABG) surgery with extracorporeal circulation were included. ST2, IL-4 and IL-10 served as markers for TH2 cytokine response; IL-6, IL-8 and IFN-gamma as TH1 markers. Furthermore, total immunoglobulin subtype analysis (IgM, IgG, IgE) was performed.

RESULTS

Serum levels of soluble ST2 started to climb at 60 minutes (from 38 +/- 14 preoperatively to 1 480 +/- 890 pg/ml) and peaked 24 hours after surgery (13 360 +/- 2 840 pg/ml, P < 0.001). IL-10 reached a maximum at 60 minutes and returned to baseline levels 24 hours later. IL-6 and IL-8 levels peaked 60 minutes after surgery. IL-4 and IFN-gamma did not change. Only IgM showed a significant peak on day eight ( P < 0.001).

CONCLUSION

Our results demonstrate that CABG surgery induces a massive long-lasting secretion of ST2, a protein related to immune suppression.

Mass measurements beyond the major r-process waiting point 80Zn

High-precision mass measurements on neutron-rich zinc isotopes (71m,72-81)Zn have been performed with the Penning trap mass spectrometer ISOLTRAP. For the first time, the mass of 81Zn has been experimentally determined. This makes 80Zn the first of the few major waiting points along the path of the astrophysical rapid neutron-capture process where neutron-separation energy and neutron-capture Q-value are determined experimentally. The astrophysical conditions required for this waiting point and its associated abundance signatures to occur in r-process models can now be mapped precisely. The measurements also confirm the robustness of the N=50 shell closure for Z=30.

Restoration of the n=82 shell gap from direct mass measurements of 132,134Sn

A high-precision direct Penning trap mass measurement has revealed a 0.5-MeV deviation of the binding energy of (134)Sn from the currently accepted value. The corrected mass assignment of this neutron-rich nuclide restores the neutron-shell gap at N=82, previously considered to be a case of "shell quenching." In fact, the new shell gap value for the short-lived (132)Sn is larger than that of the doubly magic (48)Ca which is stable. The N=82 shell gap has considerable impact on fission recycling during the r process. More generally, the new finding has important consequences for microscopic mean-field theories which systematically deviate from the measured binding energies of closed-shell nuclides.

Low-dose remifentanil to suppress haemodynamic responses to noxious stimuli in cardiac surgery: a dose-finding study

BACKGROUND

High-dose remifentanil (1-5 microg kg-1 min-1), commonly used for cardiac surgery, has been associated with muscle rigidity, hypotension, bradycardia, and reduced cardiac output. The aim of this study was to determine an optimal lower remifentanil dose, which should be accompanied by fewer adverse events, that still effectively suppresses haemodynamic responses to typical stressful stimuli (i.e. intubation, skin incision, and sternotomy).

METHODS

Total i.v. anaesthesia consisted of a target-controlled propofol (2 microg ml-1) and a remifentanil infusion. Forty patients were allocated to receive either a constant infusion of remifentanil at 0.1 microg kg-1 min-1 or up-titrations to 0.2, 0.3, or 0.4 microg kg-1 min-1, respectively, 5 min before each stimulus. Subsequently, changes in heart rate and mean arterial blood pressure were recorded for 8 min. Increases exceeding 20% of baseline were considered to be of clinical relevance. Patients who exhibited these alterations were termed responders.

RESULTS

The number of responders was less with the two higher remifentanil dosages (P<0.05) while propofol target doses could either be kept at the same level or even be reduced without affecting the plane of anaesthesia. Although single phenylephrine bolus had to be applied more frequently in these two groups (P<0.05), no severe haemodynamic depression was observed.

CONCLUSIONS

Remifentanil at 0.3 and 0.4 microg kg-1 min-1 in combination with a target-controlled propofol infusion in the pre-bypass period is well tolerated. It appears to mitigate potentially hazardous haemodynamic responses from stressful stimuli equally well as higher doses when compared with data from the literature.

Magnesium moderately decreases remifentanil dosage required for pain management after cardiac surgery †

BACKGROUND

Magnesium is a calcium and an NMDA-receptor antagonist and can modify important mechanisms of nociception. We evaluated the co-analgesic effect of magnesium in the postoperative setting after on-pump cardiac surgery.

METHODS

Forty patients randomly received either magnesium gluconate as an i.v. bolus of 0.21 mmol kg(-1) (86.5 mg kg(-1)) followed by a continuous infusion of 0.03 mmol(-1) kg(-1) h(-1) (13.8 mg kg(-1) h(-1)) or placebo for 12 h after tracheal extubation. After surgery, remifentanil was decreased to 0.05 microg kg(-1) min(-1) and titrated according to a pain intensity score (PIS, range 1-6) in the intubated, awake patient and a VAS scale (range 1-100) after extubation. If PIS was > or =3 or VAS > or =30, the infusion was increased by 0.01 microg kg(-1) min(-1); if ventilatory frequency was < or =10 min(-1) it was decreased by the same magnitude.

RESULTS

Magnesium lowered the cumulative remifentanil requirement after surgery (P<0.05). PIS > or =3 was more frequent in the placebo group (P<0.05). Despite increased remifentanil demand, VAS scores were also higher in the placebo group at 8 (2 vs 8) and 9 h after extubation (2 vs 7) (P<0.05). Dose reductions attributable to a ventilatory frequency < or =10 min(-1) occurred more often in the magnesium group (17 vs 6; P<0.05). However, time to tracheal extubation was not prolonged.

CONCLUSIONS

Magnesium gluconate moderately reduced the remifentanil consumption without serious side-effects. The opioid-sparing effect of magnesium may be greater at higher pain intensities and with increased dosages.

Isoflurane applied during ischemia enhances intracellular calcium accumulation in ventricular myocytes in part by reactive oxygen species

BACKGROUND

Isoflurane applied before myocardial ischemia has a beneficial preconditioning effect which involves generation of reactive oxygen species (ROS); ROS, however, have been implicated in critical cytosolic calcium ([Ca2+]i) overload during ischemia. We therefore investigated isoflurane's effects on intracellular Ca2+ handling in ischemic ventricular myocytes and the association with ROS.

METHODS

Simulated ischemia was induced in electrically stimulated rat ventricular myocytes for 30 min (ischemia). Isoflurane-treated cells were additionally exposed to 1MAC of isoflurane (ischemia + iso). To determine the contribution of ROS to Ca2+ homeostasis during ischemia in both groups, the intracellular ROS scavenger, N-mercaptopropionylglycine (MPG), was added to the superfusion buffer. The fluorescent ratiometric Ca2+ dye fura-2 was employed to determine [Ca2+]i.

RESULTS

Resting and peak [Ca2+]i increased in the ischemia and the ischemia + iso group. However, Ca2+ accumulation was most prominent in isoflurane-treated cardiomyocytes (P < 0.05) and could be mitigated by MPG in both groups (P < 0.001). Isoflurane also decreased the rate constant of the Ca2+ transient decline but did not further diminish the amplitude of the transient during ischemia.

CONCLUSION

Isoflurane when applied during ischemia appears to worsen [Ca2+]i overload, which is caused by impeding Ca2+ clearance. As MPG mitigated the increase in [Ca2+]i, isoflurane seems to enhance ROS-mediated effects on intracellular Ca2+ handling in cellular ischemia.

Perfusion Temperature During Cardiopulmonary Bypass Does not Affect Serum S-100β Release

BACKGROUND

The potentially harmful effects of normothermia on neurological outcome during cardiopulmonary bypass (CPB) are controversial.

METHODS

In this study, we compared the early and late release patterns of S-100beta, a marker of cerebral injury, after normothermic and moderately hypothermic CPB. Forty-eight patients undergoing coronary artery bypass grafting were randomly assigned to either the normothermia (37 degrees C) or the hypothermia (32 degrees C) group. Serum S-100beta levels were measured until 24 h after CPB. Neurological examination was performed before and after surgery.

RESULTS

With the exception of intraoperative blood glucose levels, there were no differences between groups. This also applied to peak S-100beta values (Gr-N: 3.5 +/- 1.9 microg/l; Gr-H: 3.5 +/- 3.4 microg/l) and values after 24 h (Gr-N: 0.32 +/- 0.16 microg/l; Gr-H: 0.35 +/- 0.28 microg/l).

CONCLUSIONS

The similar pattern of S-100beta release without evident neurological complications in the normothermia group does not suggest an increase in cerebral injury during normothermic CPB.

[The use of disposable instruments of a high performance polymer for tonsillectomy and adenoidectomy]

Cases of the new variant Creutzfeldt-Jakob disease (vCJD) in human beings have to be anticipated in Germany. In subclinical vCJD, the accumulation of prions in lymphoid tissue has been identified prior to their manifestation in cerebral tissue. The remarkable resistance of prions to standard methods of sterilisation questions the safety of reusing metallic surgical instruments. The transmission of vCJD via such reusable surgical instruments in tonsillectomies and adenoidectomies cannot be excluded. In this study, 96 tonsillectomies and adenoidectomies were performed with disposable instruments made of a high performance polymer (Aesculap, Tuttlingen). No increase in the number of intra- or postoperative complications was evident. These disposable instruments may represent an alternative to reusable metallic surgical instruments in potentially infected patients or in patients desiring the use of disposable instruments during their operation for safety reasons.

Mechanical trauma as the major cause of troponin T release after transvenous implantation of cardioverter/defibrillators

To study the cause of myocardial injury after elective transvenous insertion of a cardioverter/defibrillator, we measured troponin T (TnT) release in 27 patients. Five patients needing only replacement of the generator with threshold testing served as controls. Compared to the control group, a significant increase in TnT occurred in the patients undergoing insertion, which was greatest in the group receiving screw-in electrodes. There was no correlation between TnT and the number and energy of the shocks and the time in fibrillation. Duration of surgery and TnT release were positively associated. Cardiac injury therefore mainly results from mechanical trauma during insertion of the electrodes and only to a lesser degree from electrical and ischemic lesions.

The use of spectral measures of heart rate variability to differentiate between male snorers and patients with sleep apnoea syndrome

Snoring is a characteristic feature of habitual snorers and patients with sleep apnoea syndrome. However, unlike snorers, sleep apnoea patients have an increased peri-operative morbidity. Presently available methods to differentiate between these two groups are either expensive, invasive or time consuming. As cardiac reflexes are impaired in sleep apnoea syndrome, we tested whether heart rate variability could discriminate between snorers and patients with sleep apnoea syndrome. Heart rate variability measurement detects cardiac autonomic dysfunction non-invasively in an ambulatory setting. We studied 32 male patients undergoing polysomnography for suspected sleep apnoea. Total, low- and high-frequency power were measured using a Holter electrocardiogram. Differences in night- and daytime variability were then calculated. Differences between day and night values were more pronounced in the sleep apnoea group and related to the apnoea-hypopnoea-index and low oxygen saturation. Higher values in sleep apnoea patients resulted from increasing variability at night. Heart rate variability might thus help to differentiate between snorers and patients with severe sleep apnoea syndrome.

Late aortic dissection in a patient with a left ventricular assist device

The limited availability of donor hearts means that an increasing number of transplantation candidates are temporarily or permanently supported by mechanical circulatory assist devices. We report a patient undergoing implantation of a Novacor left ventricular assist device who suffered fatal aortic dissection on postoperative day 11 after satisfactory recovery from multiple organ failure. The dissection of the aorta initially presented as an embolic peripheral ischemia. Early complete echocardiography is thus warranted to rule out dissection.

First experiences with outpatient care of patients with implanted axial flow pumps

As known from patients with pulsatile ventricular assist devices (VADs), early mobilization, physical exercise, and return to normal life are essential for optimal recovery. Recently, implantable rotary pumps became available for extended left ventricular support as bridges to transplantation. Modified procedures are essential for patient training and hospital discharge. The MicroMed-DeBakey VAD was implanted in 10 patients with end-stage heart disease. After recovery, regular ergometer training was performed with loads adapted to the patient's condition. Procedures for patient observation under outdoor conditions and a blood pressure measuring device for low pulse pressure conditions were developed. Improvement of physical condition was achieved in 8 patients. In the first 2 patients, exercise capacity was limited due to flow obstruction. In the following patients, an increase of workload on the ergometer up to 120 W was observed. Correlated with training, lactate/load relationship and heart rate decreased. Three patients were discharged from the hospital during support. The DeBakey-VAD system can support patients for extended time periods and is suitable for recovery and exercise. Under optimal patient and environmental conditions, discharge from the hospital can be obtained.

Lessons learned from the first clinical implants of the DeBakey ventricular assist device axial pump: a single center report

BACKGROUND

The bridge to transplantation with pulsatile mechanical assist devices became a standard procedure for patients deteriorating on the waiting list. Recently, continuous flow axial impeller pumps were introduced to clinical application offering new advantages.

METHODS

From November 1998 till September 2000, 6 male patients (mean age 53 plus or minus 11 years) with end-stage left heart failure were implanted with a DeBakey ventricular assist device (VAD) axial-flow pump for bridge to transplantation.

RESULTS

Three patients were successfully transplanted after 74, 115, and 117 days, respectively. Two other patients died after 25 and 133 days. One patient is still on the device after 108 days. Because of modification of the implantation technique after the first 2 patients, mean pump-flow within the first 3 weeks was increased from 4.3 +/- 0.6 L/min to 6.7 +/- 0.3 L/min. Patients were put on regular bicycle-ergometer training and improved their exercise capacities up to a mean maximum oxygen consumption of 20.2 mL/kg/min.

CONCLUSIONS

Initial implants of the DeBakey VAD demonstrated support properties comparable to pulsatile pumps but without significant restrictions for extended use.

Pulsatility does not change cerebral oxygenation during cardiopulmonary bypass

BACKGROUND

To determine the effect of pulsatility during cardiopulmonary bypass (CPB) on cerebral oxygenation, we measured oxyhaemoglobin (HbO2), deoxyhaemoglobin (Hb) and oxidised cytochrome aa3 (CtO2) with near-infrared spectroscopy (NIRS) in 14 patients electively scheduled for cardiac surgery.

METHODS

Cerebral oxygenation was measured during steady state CPB at a core temperature of 32 degrees C. Non-pulsatile flow and pulsatile flow were performed for 10 min each.

RESULTS

After 14 min of CPB, HbO2, Hb and CtO2 were significantly below prebypass values. HbO2 and CtO2 did not alter with changing flow patterns. Hb significantly increased both during the period of nonpulsatile (median: -0.7 vs. 0.25 micromol/l; P<0.05) and pulsatile flow (median: 0.25 vs. 0.5 micromol/l; P<0.001). This increase was independent of flow pattern.

CONCLUSIONS

Neither oxygenated haemoglobin, nor intracellular oxygenation, represented by CtO2, indicated a beneficial effect of pulsatile perfusion during hypothermic CPB. These results, however, are only valid for short time effects within 10 min before rewarming from CPB and patients without flow-limiting stenoses of the carotid artery.

Perioperative myocardial ischemia is associated with a prolonged cardiac vagal dysfunction after non-cardiac surgery

BACKGROUND

Heart rate variability (HRV), a measure of cardiac autonomic balance seems to be linked to coronary artery disease (CAD). Impaired vagal input facilitates the generation of fatal arrhythmias and has a great impact on morbidity and mortality. The purpose of this study was to determine the relationship between perioperative HRV and the incidence of silent myocardial ischemia (SMI) and ventricular dysrhythmias in CAD-patients undergoing non-cardiac surgery.

METHODS

31 patients were studied by continuous Holter electrocardiography preoperatively and again on the evening before surgery until postoperative day 3. Three frequency and one time domain measures of HRV (TP, 0.01-1.00 Hz: total power of the amplitude spectral plot; LF, 0.04-0.15 Hz: low-frequency power; HF, 0.15-0.40 Hz: high-frequency power; MeanRR: mean of all coupling RR-intervals between normal beats) as well as ischemic events and ventricular couplets and runs were computed.

RESULTS

Depending on the presence of ischemic episodes, each patient was assigned to either the no SMI-group (13 pts) or the SMI-group (18 pts). MeanRR, TP and LF significantly declined in both groups over time. The parasympathetically dominated index HF, however, only decreased in the SMI-group. Normalized HF power (HF/TP) even increased in the no SMI-group resulting in a postoperative decrease in LF/HF ratio. TP, LF, and HF inversely correlated with ischemia parameters whereas HF/TP and HF/LF ratio correlated with the number of ventricular couplets. Incidence and severity of SMI significantly increased after surgery.

CONCLUSION

Postoperatively, a prolonged vagal withdrawal occurred in CAD-patients exhibiting perioperative SMI. Whether the increased incidence of SMI after surgery in conjunction with the observed parasympathetic derangement contributes to adverse cardiac outcome still has to be determined.

[Exteroceptive suppression of activity of the temporal muscle. Principles and applications]

The exteroceptive suppression period (ES) of the temporalis muscle activity is a trigemino-trigeminal brain stem reflex. It will be elicited most when stimulating trigeminal sensory afferents by painful stimuli and typically leads to a biphasic interruption of voluntary muscle activity. The first phase of decreased voluntary activity is called the early exteroceptive suppression period (ES1), the second, the late exteroceptive suppression period (ES2). Between these two suppression periods a phase of increased muscle activity, the so-called facilitation period (FP), can be seen. This phenomenon can be modulated by different stimulating parameters and usually, in healthy subjects, this normal pattern of the exteroceptive suppression can be elicited regularly. The reflex answer may occur at low non-painful stimulus intensities; typically, however, it appears to be most pronounced with high-intensity stimuli. Because of the obvious relationship between stimulus intensity, pain perception and reflex, the reflex is regarded as an antinociceptive reaction. The absence of an inhibition of motor activity can be visualized, for example, in hemimasticatory spasm or dystonic disorders. However, above all the ES nowadays attracts most attention as a tool to analyse different pain syndromes. One main advantage of this method in man is the ability to evaluate certain antinociceptive brain stem mechanisms functionally by means of a simple noninvasive technique. A large number of results have been obtained showing that chronic pain syndromes such as chronic tension-type headache and migraine cause changes within the normal ES recording pattern. Furthermore, some substances used in pain therapy, such as serotonin agonists or antagonists, acetylsalicylic acid or naloxone, may also alter the general appearance of the ES. This review will summarize different parameters that influence the ES reflex answer. Furthermore, the diagnostic value of changes in the ES for pathophysiological processes regarding pain perception and processing in certain pain syndromes will be discussed.

[Effectiveness of Oleum menthae piperitae and paracetamol in therapy of headache of the tension type]

The effect of a locally applied peppermint oil preparation on tension-type headache was examined in the design of a randomized, placebo-controlled double-blind crossover study for the first time. The preparation was tested against both the reference substance acetaminophen and to the corresponding placebo. The liquid test preparation contained 10 g of peppermint oil and ethanol (90%) ad 100 (test preparation LI 170, Lichtwer Pharma, Berlin); the placebo was a 90% ethanol solution to which traces of peppermint oil were added for blinding purposes. The reference preparation contained 500 mg acetaminophen; the placebo tablet was identical to the verum in size and appearance. The study included the analysis of 164 headache attacks of 41 patients of both sexes ranging between 18 and 65 years of age, suffering from tension-type headache in accordance with the IHS classification. Four headache episodes per patient were treated in a double-blind, randomized crossover design. Each headache attack was treated by the application of 2 capsules of the oral medication (1,000 mg of acetaminophen or placebo) and the cutaneous application of the oil preparation (peppermint oil or placebo solution). The oil was spread largely across forehead and temples which was repeated after 15 and 30 minutes. Using a headache diary, the headache parameters were assessed after 15, 30, 45 and 60 minutes. Compared to the application of placebo, a 10% peppermint oil in ethanol solution significantly reduced the clinical headache intensity already after 15 minutes (p < 0.01). This significant clinical reduction of the pain intensity continued over the one hour observation period. Acetaminophen, too, proved to be efficient compared to placebo (p < 0.01). There was no significant difference between the efficacy of 1,000 mg of acetaminophen and 10% peppermint oil in ethanol solution. Simultaneous application of 1,000 mg of acetaminophen and 10% peppermint oil in ethanol solution leads to an additive effect which remains below the significance threshold, however. The patients reported no adverse events. This controlled study showed for the first time that a 10% peppermint oil in ethanol solution efficiently alleviates tension-type headache. Peppermint oil thus proves to be a well-tolerated and cost-effective alternative to usual therapies.

[Electrophysiological studies on headache: the contingent negative variation]

The contingent negative variation (CNV) is a slow cortical potential recorded from the scalp. This method allows the pathophysiology of chronic headaches to be elucidated. When assessed during the pain-free interval patients suffering from migraine without aura show significantly more negative amplitudes than healthy controls. This negativity reflects the activity of cerebral noradrenergic systems. Some studies using repeated recordings of the CNV show a periodicity in amplitude change. When migraine patients are assessed a few days before a migraine attack occurs, they show pronounced negativity, which normalized during the attack. Despite these interesting findings that are based on group comparisons, evaluating the CNV on an individual basis does not allow specific conclusions. Thus, assessment of the CNV is an important tool to examine pathophysiological aspects of chronic headaches, but is not suitable as a diagnostic procedure.

[Exteroceptive suppression of activity of the temporal muscle in analysis of pain mechanisms]

Stimulating afferent fibers of the trigeminal nerve usually causes two successive suppressions (ES1 and ES2) of the voluntary muscle activity of chewing muscles. The first phase of decreased voluntary activity is called the early exteroceptive suppression period (ES1); the second phase is called the late exteroceptive suppression period (ES2). Between these two suppression periods is a phase of increased muscle activity, the so-called facilitation period (FP). Usually, in healthy subjects this normal pattern of exteroceptive suppression can be elicited regularly. The reflex answer may occur at low non-painful stimulus intensities; however, typically it appears to be most pronounced with high-intensity stimuli. Because of the obvious relationship between stimulus intensity, pain perception and reflex answer, the reflex is regarded as an antinociceptive reaction. Chronic pain syndromes like chronic tension-type headache and migraine without aura cause changes within the normal ES recording pattern. Furthermore, some substances used in pain therapy such as serotoninagonists or antagonists, acetylsalicylic acid or naloxon may also alter the general appearance of the ES. In this review different parameters that influence the ES reflex answer are summarized. Above, the diagnostic value of the changes of the ES for pathophysiological procedures regarding pain perception and pain processing in certain pain diseases is discussed.

[18 months long-term analysis of effectiveness, safety and tolerance of sumatriptan s.c. in acute therapy of migraine attacks]

The aim of the open prospective study was to investigate the efficacy, safety and tolerability of subcutaneous sumatriptan in acute migraine treatment. Patient self-treatment was monitored over a time period of 6-18 months with 6 mg of sumatriptan administered subcutaneously by an autoinjector. In total, 2,263 patients participated in the study. Headache intensity was documented by the patient in a headache diary before and 1 and 2 h after application. During the study period from October 1991 to June 1993, 43,691 migraine attacks were investigated. Treatment with sumatriptan was efficient in 89.5% of the attacks. Headache relief was achieved in 71%. Headache reoccurred in 22.7% of the attacks, and therefore a second injection was administered. An intraindividual treatment efficacy of 80-100% was achieved in 82.9% of the patients. During long-term treatment the ratio of effective treatment and headache frequency was constant; 4.9% of the patients withdrew from the study because of adverse events and because they felt the treatment was not effective. A total of 44.5% of the patients reported adverse events that were serious in 1.7%. Subcutaneous self-treatment with sumatriptan in the acute treatment of migraine is effective and well tolerated by the patients.

Exteroceptive suppression of temporalis muscle activity during migraine attack and migraine interval before and after treatment with sumatriptan

We compared the early (ES1) and late (ES2) exteroceptive suppression (ES) periods of temporalis muscle activity in 18 migraine patients during both the migraine interval and migraine attack and investigated the effect of sumatriptan and placebo on ES parameters. The measurements were performed in a balanced sequence at four different times on each patient, twice during the migraine interval and once in each of two migraine attacks. First ES1 and ES2 were measured (stimulus intensity 20 mA, stimulus duration 0.2 ms, stimulation frequency 2 Hz, averaging of 10 responses), then the medication was given on a double-blind basis with an autoinjector using either 6 mg sumatriptan or a placebo solution. Thirty minutes after application the measurements were repeated. No significant differences were found in early and late exteroceptive suppression latencies and durations between baseline measurements. Treatment did not affect the latencies of ES1 and ES2. While sumatriptan caused a significant increase in ES1 duration (p < or = 0.05) both during the migraine interval and during the migraine attack, placebo showed no significant effect on ES1 duration. Treatment with sumatriptan during the migraine attack was accompanied by a significant increase in the duration of ES2 (p < or = 0.05), but no significant changes in the durations of the late suppression periods were observed under any other conditions. The results do not support the assumption that under the experimental conditions chosen migraine attacks are accompanied by a paroxysmal change in the brain-stem mechanisms involved in the modulation of the ES parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Exteroceptive suppression of temporalis muscle activity: perspectives in headache and pain research

The paper describes possible future applications of the exteroceptive suppression (ES) of temporalis muscle activity in headache and pain research. ES is examined as a method for investigating the pathophysiology of pain mechanisms, for assisting clinical diagnosis, and for evaluating therapeutic effects. ES is one of the newest methods in headache research which permits an objective analysis of head pain as well as pain mechanisms and accordingly has an important future in headache research.

Long-term observation following traumatic-hemorrhagic shock in the dog: a comparison of crystalloidal vs. colloidal fluids

The effect of volume replacement with crystalloidal and colloidal solutions was analyzed in 40 anesthetized Foxhounds subjected to a standardized traumatic-hemorrhagic shock. Following trauma and hypotension (MAP 40 mmHg; 3.0 +/- 0.5 hr) the animals were randomized to treatment with autologous blood and hydroxyethyl starch 6% (HES 450/0.7), or human serum albumin 5% (ALB), dextran-60 6% (DX), Ringer's lactate (RL), and hyperosmolar saline 1.3% (HS), respectively. While analgesia and sedation were maintained, the hemodynamic measurements were continued for a 24-hr period. Crystalloids and colloids were found equally effective in maintaining the macrohemodynamics following resuscitation from traumatic-hemorrhagic shock. To keep central hemodynamics at pre-shock level required at least four times higher volumes of crystalloids than colloids. No specific advantage for one of the substitutes tested was found with regard to accumulation of water in the lung during the first 24 hr following shock in dogs. Extravascular lung water (thermo-dye) and organ water (gravimetry) were not different between the groups. However, fluid loss into the abdominal cavity as well as albumin extravasation into lung interstitium and abdominal cavity were more pronounced in the crystalloid-treated animals, whereas albumin redelivery by the lymph was decreased. The deterioration of tissue oxygen extractions as well as the changes in acid-base balance in both crystalloid-treated groups reflect the persistent microcirculatory inhomogeneity in spite of normal macrohemodynamics.