New postoperative pain instrument for toddlers-Secondary analysis of prospectively collected assessments after tonsil surgery

BACKGROUND

The Children's and Infant's Postoperative Pain Scale (CHIPPS) and the German version of the Parent's Postoperative Pain Measure (PPPM-D) are used to assess postoperative pain intensity in preschool children. However, they have shown low concordance in previous prospective studies on quality improvement.

AIMS

Our secondary analysis aimed to estimate the association strength between the pain score items and indication for rescue medication defined as CHIPPS ≥4 and/or PPPD-D ≥ 6. Thus, we intended to create a further developed pain instrument with fewer variables for easier routine use.

METHODS

We analyzed 1067 pain intensity assessments of hospitalized children for the development of our novel tool in two steps using modern statistical and machine-learning methods: (1) Boruta variable selection to analyze the association strength between CHIPPS score, PPPM-D items, age, weight, and elapsed time after surgery, including their interactions and pattern stability, and the binary outcome (analgesics required yes/no). (2) Symbolic regression to generate a short formula with the least number of variables and highest accuracy for rescue medication indication.

RESULTS

Additional analgesics were required in 19.96% of pain intensity assessments, whereby the PPPM-D showed higher variance than CHIPPS. Boruta identified PPPM-D score, CHIPPS score, 9 of the 15 PPPM-D variables, and time of assessment as associated with the indication for RM. Symbolic regression revealed that additional analgesics are required if CHIPPS is ≥4 OR PPPM-D item "less energy than usual" AND one of the items "more easily cry" or "more groan/moan" are answered with "yes." These PPPM-D items were not redundant and showed nonlinear course over time. The cross-validated accuracy for this assessment tool was 94.94%.

CONCLUSIONS

The new instrument is easy to use and may improve postoperative pain intensity assessment in children. However, it requires prospective validation in a new cohort.

The influence of labor epidural analgesia on maternal, uteroplacental and fetoplacental hemodynamics in normotensive parturients: a prospective observational study

BACKGROUND

Epidural analgesia provides sufficient analgesia during labor but can cause hypotension despite various prophylactic measures. We studied its effects on pre-placental, fetoplacental, and fetal hemodynamics using Doppler ultrasound. The primary endpoint was the pulsatility index of the umbilical artery at 30 min after establishing epidural analgesia. Secondary endpoints included maternal blood pressures and neonatal outcome data.

METHODS

We included healthy parturients at a cervical dilation ≥2 cm, with or without a request for epidural analgesia (n=32 per group). Ultrasound studies of the uterine arteries, umbilical artery and fetal middle cerebral artery were performed before insertion of the epidural catheter, and 30, 60 and 90 min after; the same time-points were assessed in the non-epidural control group. Maternal blood pressure was measured by a continuous non-invasive arterial pressure monitor.

RESULTS

Ultrasound studies detected no significant differences in pulsatility indices over time in any blood vessel. In contrast to the control group, maternal blood pressures were significantly lower for all measures after the onset of analgesia compared with baseline values (mean systolic pressure decreased from 132.7 ± 15.9 mmHg to 123.1 ± 14.4 mmHg at 30 min, P=0.003). The mean pH value of the umbilical arterial blood was 7.29 (±0.06) in the epidural group versus 7.31 (±0.08) in the control group (P=0.33). The median Apgar score at 5 min was 10 in both groups.

CONCLUSIONS

Pre-placental, fetoplacental and fetal hemodynamics remained stable despite a statistically significant decrease in maternal blood pressure in laboring parturients receiving epidural analgesia.

[Concept for allocation of acute stroke patients: evaluation of the quality of diagnosis reached by the emergency medical services of Münster]

BACKGROUND

Acute stroke is a time- and expertise-critical emergency. An immediate and correct diagnosis by emergency medical services (EMS) in the prehospital phase and patient transfer to the nearest adequate hospital with a stroke unit is required for early treatment of acute stroke.

PATIENTS AND METHODS

We evaluated all patients who were admitted by the EMS of Münster to one of the two stroke units in the town between October 2008 and December 2010 with a diagnosis of acute stroke. Furthermore all patients were critically analyzed who were admitted without a diagnosis of acute stroke by the EMS but nonetheless had a stroke and the correct diagnosis was not found until examination in the neurological department.

RESULTS

We analyzed 615 patients who were admitted to the stroke units with the diagnosis of acute stroke. In 561 cases (91%) this diagnosis could be confirmed, but in 54 patients (9%) the diagnosis by the EMS was incorrect. Epileptic seizure was the most frequent false-positive diagnosis in this group of patients (39%; n = 21). Although the acute symptoms were caused by a stroke, the correct diagnosis was not defined by the EMS in 127 patients. This accounted for 18% of all patients admitted to the emergency departments by the EMS where ultimately a stroke was diagnosed. In 24% of these cases (n = 30) the emergency doctor missed the correct diagnosis, which meant 4% of all patients admitted by the EMS, finally diagnosed with an acute stroke. In all other cases in the group with a false-negative diagnosis (76% or 97 patients) an emergency doctor was not involved in the referral by the EMS.

CONCLUSION

Emergency medical services should be involved in the establishment of admission programs for acute stroke patients to provide the fastest means of transportation to a stroke unit. Coma, symptoms of posterior cerebral circulation and epileptic seizures cause difficulties in ensuring an immediate and correct diagnosis. Sending an emergency doctor to the scene increases diagnostic certainty which is essential to initiate early treatment.

Teaching resuscitation in schools: annual tuition by trained teachers is effective starting at age 10. A four-year prospective cohort study

AIMS

Evaluation of school pupils' resuscitation performance after different types of training relative to the effects of training frequency (annually vs. biannually), starting age (10 vs. 13 years) and facilitator (emergency physician vs. teacher).

METHODS

Prospective longitudinal study investigating 433 pupils in training and control groups. Outcome criteria were chest compression depth, compression frequency, ventilation volume, ventilation frequency, self-image and theoretical knowledge. In the training groups, 251 pupils received training annually or biannually either from emergency physicians or CPR-trained teachers. The control group without any training consisted of 182 pupils.

RESULTS

Improvements in training vs. control groups were observed in chest compression depth (38 vs. 24 mm), compression frequency (74 vs. 42 min(-1)), ventilation volume (734 ml vs. 21 ml) and ventilation frequency (9/min vs. 0/min). Numbers of correct answers in a written test improved by 20%, vs. 5% in the control group. Pupils starting at age 10 showed practical skills equivalent to those starting at age 13. Theoretical knowledge was better in older pupils. Self-confidence grew in the training groups. Neither more frequent training nor training by emergency physicians led to better performance among the pupils.

CONCLUSIONS

Pupils starting at age 10 are able to learn cardiopulmonary resuscitation with one annual training course only. After a 60-min CPR-training update, teachers are able to provide courses successfully. Early training reduces anxieties about making mistakes and markedly increases participants' willingness to help. Courses almost doubled the confidence of pupils that what they had learned would enable them to save lives.

[Do sociodemographic factors influence emergency medical missions? : analysis in the City of Münster]

BACKGROUND

Demographic development and changes in healthcare utilization have led to a rising number of calls for emergency services. In Germany life-threatening situations are responded by physician-staffed ambulances in a 2-tier system whereas paramedic-staffed ambulances are dispatched in non-life-threatening emergencies. A nationwide protocol guides dispatchers in triage decisions. In the years 1999 to 2009 a continuous rise in the number of calls for a physician-staffed ambulance in Münster was recorded. The degree of healthcare utilization according to socioeconomic status and age structure was retrospectively examined.

METHODS

For the year 2006 all emergency calls in the City of Münster responded to by physician-staffed ambulances were analyzed. Each call was assigned to 1 of the 45 urban districts. The local incidence of emergency calls (calls/100 residents/year) was determined and compared to the socioeconomic status which was defined as the percentage of welfare and unemployment benefit recipients per district. Patient condition was assessed by the Munich National Advisory Committee for Aeronautics (M-NACA) score. This scoring system allows calls to be allocated to either life-threatening conditions or non-life-threatening conditions by objective vital parameters. The age structure of the emergency callers was also examined.

RESULTS

Urban districts with a low socioeconomic status showed a higher incidence of emergency calls requiring physician-staffed ambulance responses than districts with a high socioeconomic status. Measured by the M-NACA scoring system, the fraction of life-threatening emergencies among all calls proved to be equal to districts with a high socioeconomic status. A correlation between elderly patients and increasing numbers of life-threatening emergencies was found.

CONCLUSIONS

A low socioeconomic status of an urban district will result in more ambulance responses. However, the proportion of life-threatening emergencies is equal to districts with a high socioeconomic status. Thus, the greater need for physician-staffed ambulance responses matches clinical needs and legitimates current resource use in a 2-tier ambulance system. Indications for the abuse of physician-staffed ambulances were not found. Considering an aging population the number of emergency calls will rise in the future.

Internet surveillance systems for early alerting of health threats

In order to gather a comprehensive picture of potential epidemic threats, public health authorities increasingly rely on systems that perform epidemic intelligence (EI). EI makes use of information that originates from official sources such as national public health surveillance systems as well as from informal sources such as electronic media and web-based information tools.

Ventral recumbency is crucial for fast and safe orotracheal intubation in laboratory swine

The aim of this study was to find the fastest, easiest and safest method of achieving orotracheal intubation for general anaesthesia in laboratory pigs. Twenty-one Yorkshire × Landrace crossbreed male castrated pigs (32.9 ± 4.8 kg) were investigated. Dorsal and ventral recumbency are the alternatives most frequently described for animal positioning during intubation procedures. Based on standardized induction of general anaesthesia using pentobarbital and remifentanil, the dorsoventral and ventrodorsal positions were compared with regard to the time needed, changes in oxygenation and circulatory response. Positioning was found to be crucial for fast orotracheal intubation. The time required for safe intubation is significantly shorter with the ventrodorsal position (17.3 s) in comparison with the dorsoventral position (58.4 s; P < 0.001). Hypoxia did not occur in either group. A significant drop in systolic blood pressure was observed in both groups. Diastolic and mean arterial pressures were not influenced by intubation. A significant increase in heart rate was observed in pigs intubated in ventral recumbency, but not after intubation in the dorsal position. Preoxygenation before intubation is vitally important for preventing hypoxia. With regard to clinical practice, the haemodynamic changes observed in this investigation do not appear to be relevant, as the mean arterial pressure was not altered and heart rates only increased moderately. It may be concluded that the ventrodorsal position can be recommended for orotracheal intubation in pigs as the first choice for providing a smooth and fast airway.

Perivascular axillary brachial plexus block and patient positioning: the influence of a lateral, head-down position

The aim of this study was to examine the effect of a 20 degrees Trendelenburg position on the blockade of nerves that exit the brachial plexus proximally in patients undergoing single-injection axillary brachial plexus block. After a pilot study of eight cadavers suggested that a head-down and lateral position would encourage the proximal spread of local anaesthetic, 72 patients undergoing elective surgery were divided into two equal groups: a Supine group and a Modified Position group (lateral position, 20 degrees head-down tilt). Patients were left in the allocated position for 30 min after an axillary block had been performed with alkalinised mepivacaine 1% 49.5 ml. Sensory and motor blockade evaluation showed that there was a significantly higher proportion of axillary nerve (76% vs. 0%, p < 0.001), thoracodorsal nerve (86% vs. 0%, p < 0.001) and subscapular nerve (89% vs. 0%, p < 0.001) blockade in the Modified Position group. Sensory block of the radial nerve was also improved by the modified position (100% vs. 86%, p < 0.05).

Oberarmkorrekturosteotomie bei einem Patienten mit McCune-Albright-Syndrom unter perivaskulärer axillärer Plexusanästhesie nach Weber

We report on a 20-year-old patient with McCune-Albright syndrome suffering from global respiratory insufficiency who required continuous mask ventilation and where intubation had to be avoided. Perivascular axillary anesthesia according to Weber was performed for a double corrective osteotomy of the humerus. During plexus anesthesia the patient was positioned on the non-anesthesized side in a 15 degrees Trendelenburg position. An extension of analgesia was observed up to the complete upper arm region. Using the modified positioning an extension of brachial plexus anesthesia is possible.

Anaesthetic strategies to reduce perioperative blood loss in paediatric surgery

In adults, a number of measures to reduce perioperative blood loss have been established. These techniques serve to reduce patients' exposure to homologous blood. Most adults are concerned with this issue especially since many patients became infected with human immunodeficiency virus (HIV) during the 1980s through exposure to blood components. While blood-saving strategies are widely used in adults, they are mostly neglected in infants. However, it is these young patients with their whole life in front of them who, it could be argued, would benefit especially from any potentially avoidable infection (HIV, hepatitis, etc.) or immunological complications. In infants and small children, these blood-sparing techniques may not be as effective as in adults and technical limitations may prevent their application. However, some of these measures can be used and may serve to prevent or reduce exposure to homologous blood. In the following review, blood-saving techniques established in adults are described and their applicability for paediatric patients discussed.

Naloxone prevents increased atrial natriuretic peptide release during regional myocardial ischaemia and stunning in awake dogs

BACKGROUND

Atrial natriuretic peptide (ANP) release is increased in patients with ischaemic left ventricular dysfunction. A beneficial effect of naloxone on recovery from myocardial stunning was shown previously. The aim of this study was to investigate the effects of naloxone on ANP release during regional myocardial ischaemia and stunning in awake dogs.

METHODS

Ten dogs were chronically instrumented for measurement of heart rate, left atrial, aortic, and left ventricular pressure (LVP), LV dP x dtmax/min(-1), and myocardial wall-thickening fraction. An occluder around the left anterior descending artery (LAD) allowed induction of reversible ischaemia in the LAD-perfused myocardium. Each dog underwent two ischaemic episodes (randomized crossover fashion; separate days): 10 min of LAD occlusion (1) after application of naloxone (63 microg kg(-1)), and (2) without naloxone. ANP levels were measured at baseline (BL) and at predetermined time points until complete recovery of myocardial stunning occurred.

RESULTS

LAD ischaemia-induced release of ANP (peak level: 182 (30) vs 27 (7) pg ml(-1) BL) only in the control group without naloxone. Between 1 and 180 min of reperfusion, ANP levels were significantly higher only in the control group (P<0.05).

CONCLUSION

Pre-ischaemic application of naloxone prevents this ischaemia-induced ANP-release in conscious dogs.

Hemin, inducer of heme-oxygenase 1, improves functional recovery from myocardial stunning in conscious dogs

OBJECTIVE

To examine the effects of pretreatment with hemin, an inducer of the potential antioxidative enzyme heme-oxygenase 1 (HO-1) or heat-shock protein 32, on myocardial stunning.

DESIGN

Randomized animal study.

SETTING

Animal laboratory of a university hospital.

PARTICIPANTS

Chronically instrumented mongrel dogs (n = 44).

INTERVENTIONS

Dogs underwent chronic instrumentation for measurement of hemodynamics and myocardial wall thickening fraction (WTF). Experiments with 12 dogs were performed on separate days in a crossover fashion: (1) 10 minutes of left anterior descending (LAD) coronary artery occlusion after application of hemin (9 mg/kg/d) for 1 week and (2) 10 minutes of LAD coronary artery occlusion without hemin pretreatment. In control experiments (n = 32), the reversible induction of HO-1, using gel electrophoresis and Western blotting, was determined.

MEASUREMENTS AND MAIN RESULTS

WTF was measured as a baseline value before hemin administration and at predetermined time points until complete recovery from stunning. LAD artery occlusion caused a significant reduction in the WTF in the LAD-perfused area with and without hemin, without significant hemodynamic changes. At all time points, after 1 minute of reperfusion, the WTF as percentage of baseline values was significantly higher after hemin pretreatment (p < 0.05). Baseline WTF values were reached after 24 hours with and after >48 hours without hemin pretreatment (p < 0.05).

CONCLUSION

Hemin pretreatment attenuates myocardial stunning in conscious dogs.

Naloxone improves functional recovery of myocardial stunning in conscious dogs through its action on the central nervous system

This study tests the hypothesis that naloxone, but not its quarternary salt, naloxone methiodide (which does not enter the central nervous system), improves recovery from myocardial stunning in conscious dogs. Twenty dogs were chronically instrumented for measurement of heart rate, left atrial, aortic and left ventricular pressure (LVP), LV dP x dtmax(-1) and myocardial wall thickening fraction (WTF). Regional myocardial blood flow was determined with coloured microspheres. Occluder around the left anterior descending artery (LAD) allowed induction of reversible LAD ischaemia. Each of the 20 dogs underwent two LAD ischaemic challenges. Experiments (performed on separate days, in crossover fashion) were: (i) 10 min of LAD occlusion after application of naloxone 63 microg kg(-1) or naloxone methiodide 63 microg kg(-1) and (ii) occlusion without naloxone or naloxone methiodide. WTF was measured at baseline and until complete recovery occurred. LAD ischaemia significantly reduced LAD WTF with (mean (SD) 54 (15)% lower than baseline) and without naloxone (55 (16)% lower than baseline), without significant haemodynamic differences. Between I to 30 min of reperfusion, WTF was significantly higher with naloxone (P < 0.05). There was no difference in WTF with or without naloxone methiodide. We conclude that naloxone improved recovery from myocardial stunning in conscious dogs, and that this was centrally mediated.

[Cladismus and a 'historical' turn in the study of functional adaptation. A critical commentary on Rehkämper]

In a recently published article, Gert Rehkämper takes a critical stance towards cladistic influences on modern comparative morphology. He singles out as culprits a pre-darwinian notion of homology, a neglect of functional thinking and a misunderstanding of the principle of actualism. Furthermore, 'history' should not be used as an explanatory principle. In contrast, I argue that most central notions in evolutionary biology carry a pre-darwinian heritage, especially the term 'adaptation', without compromising their usefulness in contemporary debates. With the advent of new techniques of phylogenetic reconstructions and comparative analyses, 'history' has become a powerful and quantitative explanatory resource.

Recovery from myocardial stunning is faster with desflurane compared with propofol in chronically instrumented dogs

Volatile anesthetics exert a protective role in myocardial ischemia. An increase in sympathetic tone might exert deleterious effects on the ischemic myocardium. The use of the volatile anesthetic desflurane in myocardial ischemia is controversial because of its sympathetic activation. We compared propofol and desflurane on myocardial stunning in chronically instrumented dogs. Mongrel dogs (n = 8) were chronically instrumented for measurement of heart rate, left atrial, aortic, and left ventricular pressure, rate of rise of left ventricular pressure, and myocardial wall-thickening fraction (WTF). An occluder around the left anterior descending artery (LAD) allowed the induction of reversible LAD-ischemia. Two experiments were performed in a cross-over fashion on separate days: 1) Induction of 10 min of LAD-ischemia during desflurane anesthesia and 2) Induction of 10 min of LAD-ischemia during propofol anesthesia. Both anesthetics were discontinued immediately after completion of ischemia. WTF was measured at predetermined time points until complete recovery from ischemic dysfunction occurred. Both anesthetics caused a significant decrease of WTF in the LAD-perfused myocardium. LAD-ischemia led to a further significant decrease of LAD-WTF in both groups. During the first 3 h of reperfusion, WTF was significantly larger in the desflurane group. Mean arterial pressure and heart rate were greater during ischemia and the first 10 min of reperfusion in the desflurane group compared with the propofol group. Recovery from myocardial stunning in dogs was faster when desflurane was used at the time of ischemia as compared with propofol anesthesia. The mechanism for this difference is unclear, but sympathetic activation by desflurane was not a limiting factor for ischemic tolerance in chronically instrumented dogs.

Arteriovenous carboxyhemoglobin gradient is a technical artifact that is eliminated by special calibration (SAT 100)

Pulmonary enzyme heme oxygenase, which catalyses carbon monoxide production, may be responsible for arteriovenous carboxyhemoglobin (COHb) differences measured in humans. Unspecific inflammatory stimuli have been shown to induce pulmonary heme oxygenase possibly leading to increased pulmonary carbon monoxide production and elevated arterial COHb. Arteriovenous COHb gradients may therefore be a measurable parameter of lung injury severity. To exclude a technical artefact, we repeated measurements of central venous COHb and arterial COHb in healthy humans (ASA I-II) undergoing elective surgery with the ABL 625 and the updated version, ABL 725 (Radiometer, Copenhagen). In addition to the standard calibration, an especially accurate adjustment of the spectrophotometer wavelengths (SAT100) was performed. This adjustment eliminates the FCOHb dependency on the oxygen saturation. No significant differences were detectable between central venous and arterial COHb concentrations with either blood gas analyzer. The difference between central venous COHb and arterial COHb was 0.09 with the ABL 625 and -0.03 with the ABL 725. Therefore, we conclude that previously reported arteriovenous COHb differences are artifactual and may be eliminated by SAT 100 adjustment, as is possible with the ABL 725.

Optimal stopover decisions under wind influence: the effects of correlated winds

Wind speed and direction have a significant effect on a flying bird's ground speed. Migrants are therefore expected to be sensitive to wind conditions and this should have consequences for optimal strategies of stopover and refuelling. Based on an earlier model of time-minimizing migration which includes wind condition, we investigate the consequences of the temporal correlation of wind conditions. Day-to-day changes in wind conditions are modelled with a two-state Markov process and an expression for the expected speed of migration is derived. The policy of the migrants is described by two parameters: a day t(g) when the birds start to leave whenever favourable conditions occur and a later day t(b)when they leave even in unfavourable winds. The model predicts that in most cases departures should be close to the date which is predicted by a wind-free deterministic model and that the birds should never leave without wind assistance. Only if the probability that the condition remains the same on the following day is close to 1 should the birds leave even in unfavourable conditions shortly after the deterministic optimal date. If the transition matrix is highly asymmetrical, i.e. if it is very probable that unfavourable conditions remain and that favourable conditions will change into unfavourable, then the birds are predicted to start using good winds several days before the deterministic optimal date. An analysis of six years of wind data from two sites in Sweden shows that wind directions on successive days are in fact correlated in all years.

Limited upper thoracic epidural block and splanchnic perfusion in dogs

Epidural blockade leads to a sympathetic block in affected segments and an increase of sympathetic out-flow from various unblocked segments. A limited upper thoracic epidural block (LUTEB) is used during coronary artery surgery affecting the cardiac sympathetic fibers cephalad to the fifth thoracic segment. This block does not extend to the sympathetic fibers innervating the gastrointestinal organs. A LUTEB may lead to an increase of sympathetic activity in the unaffected splanchnic sympathetic segments and the decrease in splanchnic blood flow may contribute to gastrointestinal ischemia after cardiac surgery. We tested the hypothesis that a LUTEB decreases splanchnic perfusion in anesthetized dogs. Thirteen dogs were chronically instrumented with aortic and left atrial catheters, which were used for pressure measurement, as well as injection and withdrawal of reference samples. Thoracic epidural catheters were placed under general anesthesia the day before the experiment. Splanchnic blood flow was determined by using colored microspheres. Induction of a LUTEB did not change general hemodynamics in awake dogs. Propofol anesthesia induced an increase in heart rate that was abolished after LUTEB. LUTEB also decreased mean arterial pressure during propofol anesthesia. We conclude that thoracic epidural anesthesia had no effect on splanchnic blood flow. In propofol anesthetized animals, liver blood flow was increased compared with awake animals; however, it did not change after induction of LUTEB.

IMPLICATIONS

A sympathetic block in certain segments leads to increased sympathetic output in unblocked segments. For an upper thoracic epidural block, this might lead to impaired splanchnic perfusion. In awake and propofol-anesthetized, chronically instrumented dogs, however, a limited upper thoracic epidural blockade had no compromising effect on gastrointestinal perfusion.

Blissful Ignorance? Departure Rules for Migrants in a Spatially Heterogeneous Environment

Incomplete knowledge of the variation in site quality to be encountered during migration may make it necessary for birds to base their departure decisions on behavioural rules of thumb. Here I analyse four such rules for time-minimizers and show how they perform in spatially heterogeneous, autocorrelated environments. The first rule projects the currently experienced fuelling rate onto all the future sites, the second rule is based on a fixed expected rate along the route, the third rule assumes that the expected rate at sites nearby is close to the value currently experienced and the fourth rule uses the experienced values to form an expectation during migration. Simulations demonstrate that a global update rule which uses the current experience and interprets it as the global value to be expected at all the future sites is outperforming the second rule, which is based on fixed expectations, in nearly all circumstances and that it is very robust with respect to spatial autocorrelation and the degree of variability in fuelling rates. This rule leads to the repeatedly observed pattern of a shallow relationship between departure fuel load and fuel deposition rate. A third rule shows its best performance under the assumption that the quality of sites only changes little with distance and therefore comes close to the global update rule. The fourth departure rule, a modified version of the global update rule, which allows some adjustments of the expected value through all the experienced values so far, leads only to small increases in performance. Copyright 1999 Academic Press.

Thoracic epidural anesthesia does not affect functional recovery from myocardial stunning in sevoflurane-anesthetized dogs

OBJECTIVE

A beneficial effect of thoracic epidural anesthesia (TEA) on recovery from myocardial stunning was previously shown in awake dogs. The aim of this study was to investigate the effects of TEA on recovery from myocardial stunning in sevoflurane-anesthetized dogs.

DESIGN

Randomized animal study.

SETTING

Animal laboratory of a university hospital.

PARTICIPANTS

Chronically instrumented mongrel dogs.

INTERVENTIONS

Six dogs were chronically instrumented for measurement of hemodynamics and myocardial wall thickening fraction (WTF). The following experiments were performed on separate days in a crossover fashion: (1) 10 minutes of ischemia of the left anterior descending (LAD) coronary artery during sevoflurane anesthesia without TEA and (2) 10 minutes of ischemia during sevoflurane anesthesia with TEA.

MEASUREMENTS AND MAIN RESULTS

WTF was measured awake (baseline) and at predetermined time points until complete recovery of myocardial function occurred. Induction of anesthesia led to a decrease of WTF compared with baseline. Induction of ischemia led to a further decrease of WTF to negative values, which returned to positive values within the first minute of reperfusion. There were no differences between the two experimental conditions at any of the time points measured. In awake dogs, TEA improved the recovery from myocardial stunning compared with the control experiment. There was no difference between conscious dogs with TEA or sevoflurane-anesthetized dogs with or without TEA.

CONCLUSION

TEA has no additional protective effect on the recovery of WTF during sevoflurane anesthesia.

Clonidine improves recovery from myocardial stunning in conscious chronically instrumented dogs

Clonidine, an alpha2-adrenergic agonist, has been widely used in anesthesia because of its sedative, analgesic, sympatholytic, and specific hemodynamic effects. The use of clonidine in myocardial ischemia is controversial because of its bradycardic and hypotensive effects. In the present study, we tested the hypothesis that clonidine improves recovery from myocardial stunning in conscious dogs. Seven dogs were chronically instrumented to allow measurement of left atrial pressure (LAP), aortic blood pressure (ABP), left ventricular pressure (LVP), maximal rate of increase of LVP (LVdP/dtmax), and myocardial wall thickening fraction (WTF). The myocardial blood flow was measured using colored microspheres. To compensate for any potential interaction between the two ischemic episodes, experiments were performed on separate days in a cross-over fashion (four animals underwent Condition 1, and three underwent Condition 2 as their first experiment). The ischemic episodes involved 1) 10 min of ischemia of the left anterior descending (LAD) coronary artery without any intervention, and 2) 10 min of LAD ischemia 30 min after 10 microg/kg iv clonidine. WTF was measured before the induction of ischemia or the application of clonidine (baseline) and at predetermined time points until complete recovery of myocardial function. WTF recovered faster during the first 2 h of reperfusion when clonidine was administered. The increase in plasma epinephrine was attenuated by clonidine during ischemia, but there was no change during reperfusion. The increase of plasma norepinephrine levels was attenuated during ischemia and reperfusion. The hemodynamic effects of clonidine did not depress myocardial perfusion or impair myocardial function.

IMPLICATIONS

In this study, we investigated the effects of IV clonidine on myocardial stunning in chronically instrumented dogs. Clonidine improved the recovery from myocardial stunning and attenuated increases in catecholamine plasma levels.

A Life-history Invariant for Migration

Copyright 1998 Academic Press Limited

[Interaction of nimodipine and propofol in dogs. Hemodynamics and cardiodynamics]

Nimodipine is frequently used for treatment of cerebral vasospasm in patients undergoing intracerebral vascular surgery and during intensive care therapy of patients with subarachnoid haemorrhage. Propofol is being increasingly used as a hypnotic drug in neuroanaesthesia and for sedation in critically ill patients. There is evidence of a propofol effect on voltage-dependent calcium channels; hence, the administration of propofol may interact with the haemodynamic effects of nimodipine. We investigated the haemodynamic interactions of both compounds in chronically instrumented dogs.

METHODS

Five mongrel dogs were chronically instrumented for measurement of heart rate (HR), left atrial (LAP), aortic (ABP), and left ventricular pressure (LVP), LV dP/dt, cardiac output (CO), systemic vascular resistance (SVR), coronary blood flow velocity (CBFV), and myocardial wall-thickening fraction (WTF). After complete recovery from surgery and assessment of normal resting blood gas values and temperature, all animals received on separate days either propofol 30 mg/kg.h (P), nimodipine in two maintenance doses in the awake state (N), or the combination of nimodipine and propofol (N+P). The maintenance doses of nimodipine in N and N+P were 1 and 2 micrograms/kg.min for 40 min each after a bolus of either 10 or 20 micrograms/kg min over 2 min. Measurements were performed as controls, in the middle (20 min), and at the end (40 min) of each maintenance infusion of nimodipine or at equivalent points in time in group P (Fig. 1). Animals receiving propofol were mechanically ventilated after endotracheal intubation. Blood gas values were kept within the normal range. All data were analysed with repeated measures of ANOVA followed by student's t-test with Bonferroni correction.

RESULTS

There was no statistically significant difference for any of the measured parameters between N and N+P or between the two maintenance doses of nimodipine (Table 1). HR was significantly higher with both doses of nimodipine in the awake state compared to the control values (123 +/- 7.1 and 146 +/- 6.4 vs 78 +/- 2.4/min). The administration of nimodipine with and without propofol led to a significant increase in CBFV (Fig. 2). However, there was no difference in CBFV between nimodipine in the awake state and in combination with propofol (Fig. 2).

CONCLUSIONS

We conclude that administration of propofol does not alter the systemic haemodynamic and regional myocardial effects of a nimodipine infusion in a dose of 1 or 2 micrograms/kg.min in chronically instrumented dogs.

The effects of thoracic epidural anesthesia on functional recovery from myocardial stunning in propofol-anesthetized dogs

The purpose of this investigation was to examine the effects of thoracic epidural anesthesia (TEA) on myocardial stunning during propofol anesthesia. Six dogs were chronically instrumented for measurement of left atrial, aortic, and left ventricular pressure, maximal rate of increase of left ventricular pressure, and myocardial wall-thickening fraction (WTF). Myocardial blood flow was determined with colored microspheres. Experiments were performed on separate days with 1) 10 min of left anterior descending artery (LAD) ischemia during propofol anesthesia without TEA, and 2) 10 min of LAD ischemia during propofol anesthesia with TEA. WTF was measured as baseline (BL) prior to propofol anesthesia and at predetermined time points until complete recovery from stunning. Propofol anesthesia caused a significant decrease of WTF in the LAD-perfused myocardium (LAD-WTF) compared to BL in awake animals. LAD ischemia led to a further significant decrease of LAD-WTF. There were no significant differences in LAD-WTF between the two experimental conditions at any of the time points measured. TEA did not change subendocardial blood flow in nonischemic myocardium. During ischemia neither the subendocardial/subepicardial nor the occluded/normal zone blood flow ratio were affected by TEA. After myocardial ischemia during propofol anesthesia TEA does not affect functional recovery of stunned myocardium in dogs.

Intermolecular interactions involved in solute retention on carbon media in reversed-phase high-performance liquid chromatography

Carbon adsorbents for RPLC separations are greatly underutilized due to the poor chromatographic properties of the earliest commercially available materials and our limited understanding of solute interactions with the solid surface. Previously, we reported on the properties of a carbon surface prepared by vapor deposition on porous zirconia microspheres. The resulting material is a new type of carbon sorbent with considerably improved chromatographic properties. Here we present a fundamental study of the intermolecular interactions influencing solute retention on these novel carbon phases under RPLC conditions. Retention on seven unique carbon phases has been correlated with solute descriptors of dispersion, dipolarity/polarizability, and hydrogen bond basicity through the use of linear solvation energy relationships (LSERs). In stark contrast, conventional bonded phases do not show the large contribution from dipolarity/ polarizability, that is observed on these types of carbon. The presence of this interaction indicates a distinct difference between carbon and conventional bonded RPLC phases. Other results suggest that solvent sorption plays a significant role in controlling solute retention on carbon. In addition, we investigated the temperature dependence of retention on carbon and found typical RPLC-like behavior.

Thoracic epidural anesthesia improves functional recovery from myocardial stunning in conscious dogs

The effects of thoracic epidural anesthesia (TEA) on the contractile performance of ischemic and postischemic myocardium have not been well investigated. The purpose of this investigation was to examine the effects of TEA on severity and duration of myocardial stunning in an experimental model for sublethal acute myocardial ischemia. Seven dogs were chronically instrumented for measurement of heart rate (HR), left atrial (LAP), aortic and left ventricular pressure (LVP), LV dP/dtmax' and myocardial wall-thickening fraction (WTF). An occluder around the left anterior descending artery (LAD) allowed induction of reversible LAD ischemia. TEA was performed with lidocaine 4 mg/kg through a chronically implanted epidural catheter at the second thoracic level. Regional myocardial blood flow was determined with colored microspheres. Two experiments were performed in a cross-over design on separate days: Experiment 1, induction of 10 min of LAD ischemia without TEA; and Experiment 2, induction of 10 min of LAD ischemia with TEA. WTF was measured at baseline (BL) and predetermined time points until complete recovery from ischemic dysfunction occurred. LAD ischemia caused a significant decrease of LAD-WTF with (-28% +/- 5.1% versus BL) and without TEA (-15.5% +/- 5.3% versus BL). After 3 h of reperfusion, WTF as percent of BL values was significantly higher with TEA (P < 0.001). BL values of WTF were reached after 24 h with TEA and after more than 48 h without TEA (P < 0.05). There were no significant differences for mean arterial pressure (MAP), heart rate (HR), LVP, LAP, and LVdP/dtmax between the groups during ischemia and reperfusion. In nonischemic myocardium TEA caused an increase of subendocardial blood flow. During ischemia neither the subendocardial/subepicardial nor the occluded/ normal zone blood flow was affected by TEA. TEA attenuates myocardial stunning in conscious dogs. This finding is consistent with data regarding a reduction of infarct size due to TEA.