Predicting value of prehospital body temperature for ICU admission of septic shock patients

To specify whether an association exists between pre-hospital body temperature collected by the emergency medical services (EMS) call centre, and intensive care unit (ICU) admission of patients with septic shock. An observational study based on data collected by the EMS of Paris. All septic shocks were included. Among, the 140 calls concerning septic shock, 22 patients (16%) were admitted to ICU. The mean core temperature was 37.4±1.6°C for ICU and 38.6±1.1°C (p<4.10^-5) for non-ICU patients. Using propensity score analysis, the relative risk for ICU admission of patients with pre-hospital fever or hypothermia was 0.31 and 2 respectively. The study highlights the potential usefulness of early temperature measurement in septic shock patients to allow early proper orientation.

Comment appréhender une tuerie de masse pour les équipes Smur primo-intervenantes ?

Le risque terroriste présent sur l’ensemble de notre territoire depuis plusieurs années conduit les équipes de Samu–Smur à intervenir sur les lieux d’une tuerie de masse aux côtés de forces de sécurité, voire en tant que primointervenants. De telles circonstances exposent les équipes à un environnement de travail inhabituel et hostile. Cette mise au point, proposée en complément de la recommandation formalisée d’experts sur la prise en charge de tuerie de masse, répond aux interrogations qui naissent sur le terrain en pareilles circonstances. Elle facilite une juste appréciation des événements, aide à réguler ses émotions, dans le but d’augmenter la capacité des soignants à agir, tout en réduisant la phase de sidération initiale, elle-même responsable d’une inertie à même d’impacter le pronostic des blessés en choc hémorragique. Des procédures anticipées, sous forme de check-lists, guident les actions à mener de manière sereine. Les équipes médicales préhospitalières doivent apporter sur le terrain non seulement une compétence médicale, mais également une compétence tactique et décisionnelle pour accélérer les flux d’évacuation. Le premier médecin engagé doit aider à la décision aux côtés du commandant des opérations de secours, du commandant des opérations de police et de gendarmerie et des médecins intégrés aux forces de sécurité intérieure en attendant le directeur des secours médicaux. Il doit donc également faire preuve d’une compétence de chef d’équipe.

Epinephrine administration in non-shockable out-of-hospital cardiac arrest

BACKGROUND

Epinephrine is recommended for the treatment of non-shockable out of hospital cardiac arrest (OHCA) to obtain return of spontaneous circulation (ROSC). Epinephrine efficiency and safety remain under debate.

OBJECTIVE

We propose to describe the association between the cumulative dose of epinephrine and the failure of ROSC during the first 30 min of advanced life support (ALS).

METHODOLOGY

A retrospective observational cohort study using the Paris SAMU 75 registry including all non-traumatic OHCA. All OHCA receiving epinephrine during the first 30 min of ALS were enrolled. Cumulative epinephrine dose given during ALS to ROSC was retrieved from medical reports.

RESULTS

Among 1532 patients with OHCA, 776 (51%) had initial non-shockable rhythm. Fifty-four patients were excluded for missing data. The mean value of cumulative dose of epinephrine was 10 ± 4 mg in patients who failed to achieve ROSC (ROSC-) and 4 ± 3 mg (p = 0.04) for those who achieved ROSC. ROC curve analysis indicated a cut-off point of 7 mg total cumulative epinephrine associated with ROSC- (AUC = 0.89 [0.86-0.92]). Using propensity score analysis including age, sex and no-flow duration, association with ROSC- only remained significant for epinephrine > 7 mg (p ≤10-3, OR [CI95] = 1.53 [1.42-1.65]).

CONCLUSION

An association between total cumulative epinephrine dose administered during OHCA resuscitation and ROSC- was reported with a threshold of 7 mg, best identifying patients with refractory OHCA. We suggest using this threshold in this context to guide the termination of ALS and early decide on the implementation of extracorporeal life support or organ harvesting in the first 30 min of ALS.

The concept of damage control: extending the paradigm in the prehospital setting

OBJECTIVE

The purpose of this review is to present the progressive extension of the concept of damage control resuscitation, focusing on the prehospital phase.

ARTICLE TYPE

Review of the literature in Medline database over the past 10 years.

DATA SOURCE

Medline database looking for articles published in English or in French between April 2002 and March 2013. Keywords used were: damage control resuscitation, trauma damage control, prehospital trauma, damage control surgery. Original articles were firstly selected. Editorials and reviews were secondly studied.

DATA SYNTHESIS

The importance of early management of life-threatening injuries and rapid transport to trauma centers has been widely promulgated. Technical progress appears for external methods of hemostasis, with the development of handy tourniquets and hemostatic dressings, making the crucial control of external bleeding more simple, rapid and effective. Hypothermia is independently associated with increased risk of mortality, and appeared accessible to improvement of prehospital care. The impact of excessive fluid resuscitation appears negative. The interest of hypertonic saline is denied. The place of vasopressor such as norepinephrine in the early resuscitation is still under debate. The early use of tranexamic acid is promoted. Specific transfusion strategies are developed in the prehospital setting.

CONCLUSION

It is critical that both civilian and military practitioners involved in trauma continue to share experiences and constructive feedback. And it is mandatory now to perform well-designed prospective clinical trials in order to advance the topic.

[Out-of-hospital management of elderly patients for trauma injury]

Elderly patients should benefit from maximum care in cases of serious trauma, starting with pre-hospital care. A proper evaluation of the gravity of the trauma is an essential element in the management. The elderly are at risk of "under-triage", which can result in inappropriate hospital admission and delayed trauma care. Particular attention must be paid to "common" trauma, because such trauma is often associated with a potentially serious outcome in elderly patients. The Vittel criteria offer an important tool to estimate the level of gravity and to help in patient triage. The kinetic of the accident is important in identifying serious trauma. Emergency medical services with physicians on board must be the norm in cases of severe trauma, irrespective of the age of the patient. The literature clearly indicates the benefit of an aggressive strategy in elderly trauma patients, thus justifying direct admission in a trauma center in cases of real or potentially serious trauma. There is no difference in pre-hospital care management between elderly and younger trauma patients. Analgesia must be a priority. When a self-assessment of pain intensity is impossible, specific scales for pain can be used, such as Algoplus(®). Morphine titration is the recommended strategy for analgesia in the pre-hospital setting and the same protocol must be used for both the elderly and younger patients. Locoregional anaesthesia should be used when possible in this setting, in particular the ilio-facial block. Age is not a criterion for a non-resuscitation order in trauma patients. The decisions of limitation of therapeutic, if they were not anticipated, will be discussed after admission, according to the principles of the current legislation.

Ultrafast and whole-body cooling with total liquid ventilation induces favorable neurological and cardiac outcomes after cardiac arrest in rabbits

BACKGROUND

In animal models of cardiac arrest, the benefit afforded by hypothermia is closely linked to the rapidity of the decrease in body temperature after resuscitation. Because total liquid ventilation (TLV) with temperature-controlled perfluorocarbons induces a very rapid and generalized cooling, we aimed to determine whether this could limit the post-cardiac arrest syndrome in a rabbit model. We especially focused on neurological, cardiac, pulmonary, liver and kidney dysfunctions.

METHODS AND RESULTS

Anesthetized rabbits were submitted to either 5 or 10 minutes of untreated ventricular fibrillation. After cardiopulmonary resuscitation and resumption of a spontaneous circulation, the animals underwent either normothermic life support (control) or therapeutic hypothermia induced by TLV. The latter procedure decreased esophageal and tympanic temperatures to 32°C to 33°C within only 10 minutes. After rewarming, the animals submitted to TLV exhibited an attenuated neurological dysfunction and decreased mortality 7 days later compared with control. The neuroprotective effect of TLV was confirmed by a significant reduction in brain histological damages. We also observed limitation of myocardial necrosis, along with a decrease in troponin I release and a reduced myocardial caspase 3 activity, with TLV. The beneficial effects of TLV were directly related to the rapidity of hypothermia induction because neither conventional cooling (cold saline infusion plus external cooling) nor normothermic TLV elicited a similar protection.

CONCLUSIONS

Ultrafast cooling instituted by TLV exerts potent neurological and cardiac protection in an experimental model of cardiac arrest in rabbits. This could be a relevant approach to provide a global and protective hypothermia against the post-cardiac arrest syndrome.

Minimum alveolar concentration of halogenated volatile anaesthetics in left ventricular hypertrophy and congestive heart failure in rats

BACKGROUND

Although many physiological and pathological conditions affect minimal alveolar concentration (MAC), there are no reliable data on the MAC for halogenated anaesthetics during left ventricular hypertrophy (LVH) and congestive heart failure (CHF). The aim of this experimental study was to determine the MAC values of halothane, isoflurane, and sevoflurane in rats, at early and later stages of cardiomyopathic hypertrophy.

METHODS

LVH was induced by ascending aortic stenosis in 3-4-week-old rats. LVH and CHF in each animal were assessed weekly by echocardiography. MAC of halothane, isoflurane, and sevoflurane was determined using the tail-clamp technique in spontaneously breathing rats from each group. Response vs no-response data were analysed using logistic regression analysis. Data are medians (95% confidence interval).

RESULTS

The MAC of halothane [1.30% (1.26-1.34)], isoflurane [1.52% (1.48-1.57)], and sevoflurane [2.93% (2.78-3.07)] in rats with LVH was not different from sham-operated rats [respectively, 1.23% (1.20-1.26), 1.52% (1.47-1.56), and 2.90% (2.79-3.00)]. Conversely, the MAC of halothane [1.44 (1.39-1.50)] and isoflurane [1.74 (1.69-1.78)], but not sevoflurane [2.99 (2.93-3.06)], was significantly increased in rats with CHF.

CONCLUSIONS

MAC values for halothane, isoflurane, and sevoflurane were unchanged in rats with pressure-induced overload LVH. Conversely, the MAC for halothane and isoflurane, but not sevoflurane, was significantly increased in rats with CHF.

An evaluation of capnography monitoring during the apnoea test in brain-dead patients

BACKGROUND AND OBJECTIVE

Diagnosis of brain death usually requires the absence of spontaneous respiratory movements during the apnoea test and an arterial carbon dioxide partial pressure above 60 mmHg. On the other hand, although capnography (end-tidal CO(2)) is currently monitored in intensive care unit patients, it has not been evaluated during the apnoea test in brain-dead patients. Therefore, the aim of this prospective study was first to investigate the usefulness of capnography monitoring, and secondly to evaluate the variation of the carbon dioxide partial pressure-end-tidal CO(2) gradient during the apnoea test in clinically brain-dead patients.

METHODS

After local Ethics Committee approval, 60 clinically brain-dead patients were investigated. End-tidal CO(2) was continuously recorded before, during and after the apnoea test. Arterial blood gases were sampled immediately before and after the apnoea test for calculation of the carbon dioxide partial pressure-end-tidal CO(2) gradient.

RESULTS

The apnoea test was clinically positive in 58 patients, whereas end-tidal CO(2) was equal to 0 during the apnoea. During the 20-min apnoea test, carbon dioxide partial pressure increased from 40 +/- 7 to 97 +/- 19 mmHg (P < 0.001) with a rate of 2.8 +/- 0.9 mmHg min(-1), end-tidal CO(2) increased from 31 +/- 6 to 68 +/- 17 mmHg (P < 0.001) and carbon dioxide partial pressure-end-tidal CO(2) gradient increased from 9 +/- 4 to 29 +/- 10 mmHg (P < 0.001). In two patients, the apnoea test was clinically negative because of the occurrence of spontaneous respiratory movements, whereas capnography showed contemporaneously significant increases in end-tidal CO(2).

CONCLUSIONS

End-tidal CO(2) should be systematically monitored and recorded, at least for medico-legal considerations, during the apnoea test in brain-dead patients. The high variability in the carbon dioxide partial pressure-end-tidal CO(2) gradient increase precludes any extrapolation of the carbon dioxide partial pressure from the end-tidal CO(2) at the end of the apnoea test.

Interaction of protamine with alpha- and beta-adrenoceptor stimulations in rat myocardium

BACKGROUND

Protamine alters the inotropic responses to beta-adrenoceptor stimulation, but its mechanism of action is not well-understood. Moreover, its interaction with alpha-adrenoceptor stimulation and the lusitropic (relaxation) response to beta-adrenoceptor stimulation remain unknown.

METHODS

The effects of protamine (10 or 100 microg/ml) on the responses induced by phenylephrine and isoproterenol were studied in rat left ventricular papillary muscles. Inotropic and lusitropic effects were studied under low and high loads. The authors also studied the interaction of protamine with forskolin (50 microm) and dibutyryl 3',5'-cAMP (0.5 mm). Data are mean percentage of baseline active force +/- SD.

RESULTS

In control groups, phenylephrine (135 +/- 17%, P < 0.05) and isoproterenol (185 +/- 44%, P < 0.05) induced a positive inotropic effect. Isoproterenol induced positive lusitropic effects under low and high loads. Protamine abolished the inotropic responses to alpha- (102 +/- 23%, not significant) and beta-adrenoceptor stimulations (99 +/- 17%, not significant) but did not modify the lusitropic responses to isoproterenol. Protamine abolished the inotropic responses to forskolin (89 +/- 6 vs. 154 +/- 20%, P < 0.05) and markedly decreased that of dibutyryl 3',5'-cAMP (132 +/- 31 vs. 167 +/- 30%, P < 0.05) but did not modify their lusitropic responses.

CONCLUSIONS

Protamine abolished the inotropic responses to alpha- and beta-adrenoceptor stimulations but preserved the lusitropic responses to beta-adrenoceptor stimulation. Although protamine may act at several sites on the adrenoceptor stimulation cascade, one of its main sites of action is situated downstream from cAMP-mediated phosphorylation.

Prehospital use of minimally invasive direct cardiac massage (MID-CM): a pilot study

BACKGROUND

Internal cardiac compressions are more efficient than closed chest compressions (CCC) in cardiac arrest (CA).

AIM OF THE STUDY

To evaluate the prehospital feasibility of performing a new method of minimally invasive direct cardiac massage (MID-CM TheraCardia Inc.).

METHODS

Prospective non-randomized open study, after ethical committee approval. Inclusion of 18-85 years old patients in witnessed CA if BLS>5 min and unsuccessful ACLS>20 min after CA. The MID-CM is an atraumatic manual cardiac pumping system deployed in the thoracic cavity through a small incision. Evaluation of: ease of insertion and performing MID-CM, complications, end-tidal CO(2) (PETCO(2)), non invasive arterial blood pressure (NIBP) and return of spontaneous circulation (ROSC). Values are mean+/-SD (min-max).

RESULTS

Twenty-five patients included. Mean age 59+/-16 years (26-85); BLS started at 8+/-5 min (0-20), compressions started at 47+/-10 min (29-74) after CA. Dissection and insertion was fast and easy (<1 min). Deployment of the MID-CM was difficult in two patients because of pericardium adhesions and cardiomegaly. In six patients compressions were more difficult because of a 'stone heart' phenomenon. Compressions were possible during ambulance transport of four patients. There was a good palpable carotid pulse in all patients receiving internal compressions. There was a trend in increase of PETCO(2) compared to CCC. NIBP could be measured during MID-CM compressions in 9 patients (systolic>85 mmHg), never during CCC. Seven patients had a ROSC, but only four patients were admitted alive. There was no long term survival. One patient had a serious complication (heart rupture).

DISCUSSION

Prehospital use of MID-CM is possible, but it is not comparable to any other resuscitation technique. Training of medical teams is mandatory to obtain good skills and to avoid complications. Further studies are necessary to evaluate efficiency and survival compared to closed chest compressions.

Minimum alveolar concentration of volatile anesthetics in rats during postnatal maturation

BACKGROUND

Although neonatal rats have become widely used as experimental laboratory animals, minimum alveolar concentration (MAC) values of volatile anesthetics in rats during postnatal maturation remain unknown.

METHODS

We determined MAC values of volatile anesthetics in spontaneously breathing neonatal (2-, 9-, and 30-day-old) and adult Wistar rats exposed to increasing (in 0.1-0.2% steps) concentrations of halothane, isoflurane, or sevoflurane (n = 12-20 in each group), using the tail-clamp technique. MAC and its 95% confidence intervals were calculated using logistic regression and corrected for body temperature (37 degrees C).

RESULTS

In adult rats, inspired MAC values corrected at 37 degrees C were as follows: halothane, 0.88% (confidence interval, 0.82-0.93%); isoflurane, 1.12% (1.07-1.18%); and sevoflurane, 1.97% (1.84-2.10%). In 30-day-old rats, the values were as follows: halothane, 1.14% (1.07-1.20%); isoflurane, 1.67% (1.58-1.76%); and sevoflurane, 2.95% (2.75-3.15%). In 9-day-old rats, inspired MAC values were as follows: halothane, 1.68% (1.58-1.78%); isoflurane, 2.34% (2.21-2.47%); and sevoflurane, 3.74% (3.64-3.86%). In 2-day-old rats, inspired MAC values were as follows: halothane, 1.54% (1.44-1.64%); isoflurane, 1.86% (1.72-2.01%); and sevoflurane, 3.28% (3.09-3.47%).

CONCLUSION

As postnatal age increases, MAC value significantly increases, reaching the greatest value in 9-day-old rats, and decreases thereafter, and at 30 days is still greater than the adult MAC value.

Distribution of the probability of survival is a strategic issue for randomized trials in critically ill patients

BACKGROUND

Many randomized clinical trials in trauma have failed to demonstrate a significant improvement in survival rate. Using a trauma patient database, we simulated what could happen in a trial designed to improve survival rate in this setting.

METHODS

The predicted probability of survival was assessed using the TRISS methodology in 350 severely injured trauma patients. Using this probability of survival, the authors simulated the effects of a drug that may increase the probability of survival by 10-50% and calculated the number of patients to be included in a triad, assuming alpha = 0.05 and beta = 0.10 by using the percentage of survivors or the individual probability of survival. Other distributions (Gaussian, J shape, uniform) of the probability of survival were also simulated and tested.

RESULTS

The distribution of the probability of survival was bimodal with two peaks (< 0.10 and > 0.90). There were major discrepancies between the number of patients to be included when considering the percentage of survivors or the individual value of the probability of survival: 63,202 versus 2,848 if the drug increases the probability of survival by 20%. This discrepancy also occurred in other types of distribution (uniform, J shape) but to a lesser degree, whereas it was very limited in a Gaussian distribution.

CONCLUSIONS

The bimodal distribution of the probability of survival in trauma patients has major consequences on hypothesis testing, leading to overestimation of the power. This statistical pitfall may also occur in other critically ill patients.

Extracellular calcium modulates the effects of protamine on rat myocardium

We studied the effects of protamine (10-300 microg. mL(-1)) as well as its interaction with heparin in rat left ventricular papillary muscles in vitro at calcium concentrations of 0.5 and 1 mM under low (isotony) and high (isometry) loads. Protamine induced a negative inotropic effect that was less pronounced at calcium 0.5 mM (active force at protamine 300 microg/mL, 84 +/- 20 vs 57 +/- 15% of baseline, P: < 0.05); whereas at calcium 1 mM there was a marked contracture of the muscle. For the smallest concentrations of protamine and at calcium 0.5 mM, we observed a moderate positive inotropic effect that was suppressed by nifedipine. Protamine induced a negative lusitropic effect under low load and decreased postrest potentiation, suggesting an impairment in the functions of the sarcoplasmic reticulum. Heparin was able to inhibit and reverse the negative inotropic effect of protamine. The negative inotropic effect of protamine is enhanced by an increase in extracellular calcium concentration. This negative inotropic effect is probably related to calcium overload and impairment in sarcoplasmic reticulum functions, and heparin can block these effects.

IMPLICATIONS

The negative inotropic effect of protamine is enhanced by an increase in extracellular calcium concentration. This negative inotropic effect is probably related to calcium overload and impairment in sarcoplasmic reticulum functions, and heparin can block these effects.

[Barotrama during apnea testing for the determination of brain death]

We describe three cases of tension pneumothorax occurring during apnea testing for the determination of brain death. Every case needed needle thoracostomy for emergency chest deflation and/or a chest tube to be inserted rapidly. Moreover, haemodynamic and oxygenation parameters were impaired in each of the patients after these pneumothorax. This was uneventful for the two first patients (organs harvesting was contra-indicated or not consented by the patient's family), but might be responsible for damaging lungs in the third patient and consequently loosing the pulmonary graft. Limitation of oxygen insufflation up to 8 L.min-1 with a 12 F oxygen supply tubing inserted within 5 cm into the endotracheal tube should be recommended to avoid this iatrogenic complication.

Peribulbar versus retrobulbar anesthesia for ophthalmic surgery: an anatomical comparison of extraconal and intraconal injections

BACKGROUND

Peribulbar and retrobulbar anesthesia have long been opposed on the basis of the existence of an intermuscular membrane, which is supposed to separate the intraconal from the extraconal spaces in a water-tight fashion. A local anesthetic injected outside the cone should spread through this septum to reach the nerves to be blocked. The existence of this septum is questioned. The aim of this study was to compare the spread of a colored latex dye injected intraconally or extraconally to simulate both retrobulbar and peribulbar anesthesia.

METHODS

The authors used 10 heads from human cadavers. For each head, one eye was injected intraconally, and the other eye was injected extraconally. The heads were then frozen and sectioned into thin slices following various planes. They were then photographed and observed.

RESULTS

There was no evidence of the existence of an intermuscular septum separating the intraconal and extraconal spaces. Those two spaces appeared to be part of a common spreading space, the corpus adiposum of the orbit.

CONCLUSIONS

These results are in accord with the fact that clinical studies were not able to clearly demonstrate that retrobulbar anesthesia is more efficient than peribulbar anesthesia. On the basis of a similar clinical efficacy of the two techniques as a result of similar spreading of the local anesthetic injected, and a potentially higher risk of introducing the needle into the muscular cone, the authors recommend replacing retrobulbar anesthesia with peribulbar anesthesia.

Clevidipine blockade of L-type Ca2+ currents: steady-state and kinetic electrophysiological studies in guinea pig ventricular myocytes

Steady-state and transient effects of clevidipine, a rapidly degraded dihydropyridine (DHP) L-type Ca2+ channel antagonist, were examined on I(Ca) in guinea pig ventricular myocytes. When myocytes were voltage-clamped with holding potential (V(H)) at -80 mV, 10 nM clevidipine decreased I(Ca) at 0 mV by approximately 30%, but >50% when V(H) was -40 mV. Rapid (<50 ms) perfusion switching and repeated depolarizations delivered at 0.5-2 Hz were used to determine the time constants of onset (tau(on)) and recovery from (tau(off)) clevidipine inhibition of I(Ca). The tau(on) and tau(off) were monoexponential functions of time. The tau(on) of I(Ca) inhibition decreased from 21.5 +/- 1.2 to 9.9 +/- 0.9 s when the rapidly applied [clevidipine] was increased from 10 to 100 nM at V(H) = -80 mV; tau(off) was independent of the applied [clevidipine] and was 23.9 +/- 1.1 s. The dissociation constant (K(D)) calculated for clevidipine at V(H) = -80 mV was 65 +/- 3 nM, similar to the IC50 of 78 nM determined in steady-state measurements. Decreasing V(H) to -40 mV increased tau(off) more than threefold to 81 +/- 6 s, and K(D) was markedly decreased to 9.0 +/- 0.8 nM (IC50, 7.1 nM at V(H) = -40 mV). The increased affinity at depolarized V(H) may contribute to the varying concentration-effect relation observed in vivo.

Medial canthus episcleral (sub-Tenon) anesthesia imaging

Medial canthus single injection periocular anesthesia is an alternative technique to classical regional anesthesia techniques for cataract surgery. The occurrence of a chemosis at the end of this injection has made us question ourselves about the real site of injection. The purpose of this anatomic study was to identify this site with precision, and to describe the spreading of the injected solution. Various volumes of colored liquid latex were injected when using this technique on 10 human orbits. They were deeply frozen and sectioned in thin slices. The site of injection is clearly the episceral (sub-Tenon) space. This is a gliding space through which pass the ciliary nerves supplying the globe sensitivity. This could explain the high quality of the analgesia of the globe. With the larger volumes injected, spreading of the latex was detected in the orbicularis palpebra. This probably explains the good akinesia of the lids obtained without any facial block. Spreading of the latex to the rectus muscles sheaths should explain the good akinesia of the globe, but was only partially proved in this study. We conclude that the medial canthus single injection periocular anesthesia is an episcleral (sub-Tenon) injection which may explain good anesthesia.

Ophthalmic regional anesthesia: medial canthus episcleral (sub-tenon) anesthesia is more efficient than peribulbar anesthesia: A double-blind randomized study

BACKGROUND

Regional anesthesia and especially peribulbar anesthesia commonly is used for cataract surgery. Failure rates and need for reinjection remains high, however, with peribulbar anesthesia. Single-injection high-volume medial canthus episcleral (sub-Tenon's) anesthesia has proven to be an efficient and safe alternative to peribulbar anesthesia.

METHODS

The authors, in a blind study, compared the effectiveness of both techniques in 66 patients randomly assigned to episcleral anesthesia or single-injection peribulbar anesthesia. Motor blockade (akinesia) was used as the main index of anesthesia effectiveness. It was assessed using an 18-point scale (0-3 for each of the four directions of the gaze, lid opening, and lid closing, the total being from 0 = normal mobility to 18 = no movement at all). This score was compared between the groups 1, 5, 10, and 15 min after injection and at the end of the surgical procedures. Time to onset of the blockade also was compared between the two groups, as was the incidence of incomplete blockade with a need for supplemental injection and the satisfaction of the surgeon, patient, and anesthesiologist.

RESULTS

Episcleral anesthesia provided a quicker onset of anesthesia, a better akinesia score, and a lower rate of incomplete blockade necessitating reinjection (0 vs. 39%; P < 0.0001) than peribulbar anesthesia. Even after supplemental injection, peribulbar anesthesia had a lower akinesia score than did episcleral anesthesia. Peribulbar anesthesia began to wear off during surgery, whereas episcleral anesthesia did not.

CONCLUSION

Medial canthus single-injection episcleral anesthesia is a suitable alternative to peribulbar anesthesia. It provides better akinesia, with a quicker onset and more constancy in effectiveness.

Minimum alveolar anesthetic concentration of volatile anesthetics in normal and cardiomyopathic hamsters

Minimum alveolar anesthetic concentrations (MAC) values of volatile anesthetics in cardiovascular diseases remain unknown. We determined MAC values of volatile anesthetics in spontaneously breathing normal and cardiomyopathic hamsters exposed to increasing (0.1%-0.3% steps) concentrations of halothane, isoflurane, sevoflurane, or desflurane (n = 30 in each group) using the tail-clamp technique. MAC values and their 95% confidence interval were calculated using logistic regression. In normal hamsters, inspired MAC values were: halothane 1.15% (1.10%-1.20%), isoflurane 1.62% (1.54%-1.69%), sevoflurane 2.31% (2.22%-2.40%), and desflurane 7.48% (7.30%-7.67%). In cardiomyopathic hamsters, they were: halothane 0.89% (0.83%-0.95%), isoflurane 1.39% (1.30%-1.47%), sevoflurane 2.00% (1.85%-2.15%), and desflurane 6.97% (6.77%-7.17%). Thus, MAC values of halothane, isoflurane, sevoflurane, and desflurane were reduced by 23% (P < 0.05), 14% (P < 0.05), 13% (P < 0.05), and 7% (P < 0.05), respectively in cardiomyopathic hamsters.

IMPLICATIONS

Minimum alveolar anesthetic concentrations of volatile anesthetics were significantly lower in cardiomyopathic hamsters than in normal hamsters.

Effects of propofol, propofol-nitrous oxide and midazolam on cortical somatosensory evoked potentials during sufentanil anaesthesia for major spinal surgery

Recording of cortical somatosensory evoked potentials (CSEP) enables monitoring of spinal cord function. We studied the effects of propofol, propofol-nitrous oxide or midazolam during sufentanil anaesthesia on CSEP monitoring during major spinal surgery. Thirty patients with normal preoperative CSEP were allocated randomly to one of the following anaesthesia regimens: propofol (2.5 mg kg-1 followed by 10-6 mg kg-1 h-1) with or without nitrous oxide, or midazolam (0.3 mg kg-1 followed by 0.15 mg kg-1 h-1) combined with sufentanil 0.5 microgram kg-1 h-1 in the propofol and midazolam groups, or 0.25 microgram kg-1 h-1 in the propofol-nitrous oxide group. CSEP were elicited by alternate right and left tibial posterior nerve stimulation and recorded before and after induction (15 min, 1, 2 and 3 h), and during skin closure. CSEP latencies were not significantly modified in the three groups. CSEP amplitude decreased significantly in the propofol-nitrous oxide group (from mean 2.0 (SEM 0.3) to 0.6 (0.1) microV; P < 0.05) but not in the propofol (from 1.8 (0.6) to 2.2 (0.3) microV) or midazolam (1.7 (0.5) to 1.6 (0.5) microV) groups. The time to the first postoperative voluntary motor response (recovery) delay was significantly greater in the midazolam group (115 (19) min) compared with the propofol and propofol-nitrous oxide groups (43 (8) and 41 (3) min, respectively). Consequently, the use of propofol without nitrous oxide can be recommended during spinal surgery when CSEP monitoring is required.

Myocardial effects of desflurane in hamsters with hypertrophic cardiomyopathy

BACKGROUND

The effects of desflurane on myocardial contraction and relaxation in diseased myocardium have not been completely understood.

METHODS

The effects of desflurane (1.8 to 9.4 vol%) in left ventricular papillary muscles of healthy hamsters and those with genetically induced cardiomyopathy (strain BIO 14.6) were investigated in vitro (29 degrees C, pH 7.40, Ca2+ 2.5 mM; stimulation frequency, 3/min) under low (isotony) and high (isometry) load. Data are mean percentages of baseline +/- SD.

RESULTS

Desflurane induced no significant inotropic effect in healthy muscles (maximum unloaded shortening velocity and isometric active force at 9.4 vol%: 97 +/- 9% and 92 +/- 20%, respectively). In contrast, in cardiomyopathic muscles, desflurane induced a moderate negative inotropic effect (maximum unloaded shortening velocity and active force at 9.4 vol%: 84 +/- 19% and 75 +/- 25%, respectively). The negative inotropic effect was more pronounced than that in healthy muscles under low (P < 0.05) but not high load, and even when concentrations were corrected for minimum alveolar concentrations in each strain. Adrenoceptor blockade or pretreatment with reserpine did not modify the inotropic effect of desflurane, suggesting the absence of intramyocardial catecholamine release. However, tyramine also did not induce any significant catecholamine release in hamster myocardium. In both strains, desflurane induced no significant lusitropic effect under low or high load.

CONCLUSIONS

Desflurane had no inotropic effect in healthy muscles and a moderate negative inotropic effect in cardiomyopathic muscles. The absence of desflurane-induced intramyocardial catecholamine release was related to hamster myocardium characteristics.

Comparison of the effects of sevoflurane, isoflurane and halothane on rat myocardium

The effects of sevoflurane on myocardial contraction and relaxation are poorly understood. Therefore, we studied the effects of equianaesthetic concentrations (0.5, 1, 1.5, 2 and 2.5 MAC) of sevoflurane, isoflurane and halothane on inotropic and lusitropic (myocardial relaxation) variables, and post-rest potentiation in rat left ventricular papillary muscles in vitro. Sevoflurane and isoflurane caused comparable concentration-dependent negative inotropic effects which were significantly lower than those induced by halothane (P < 0.05). Sevoflurane and isoflurane did not modify lusitropic variables under low or high load, whereas halothane showed a negative lusitropic effect at high concentrations. Halothane suppressed post-rest potentiation, whereas isoflurane and sevoflurane did not. Post-rest recovery was unaffected by halothane, isoflurane or sevoflurane at any concentration. Thus in rat myocardium, sevoflurane and isoflurane caused comparable negative inotropic effects, had no significant lusitropic effects and did not alter post-rest potentiation, suggesting that they did not significantly modify the functions of the sarcoplasmic reticulum.

Interaction of isoflurane and sevoflurane with alpha- and beta-adrenoceptor stimulations in rat myocardium

BACKGROUND

Halothane potentiates the positive inotropic effects of alpha- and beta-adrenoceptor stimulations but impairs the positive lusitropic effect of beta-adrenoceptor stimulations. However, the interactions of isoflurane and sevoflurane with alpha- and beta-adrenoceptor stimulation have not been entirely defined.

METHODS

The effects of 1 minimum alveolar concentration isoflurane and sevoflurane on the inotropic responses induced by phenylephrine (10(-8) to 10(-4) M) or isoproterenol (10(-8 to 10(-4) M) were studied in rat left ventricular papillary muscles in vitro (Krebs-Henseleit solution, 29 degrees C; pH, 7.4; 0.5 mM calcium; stimulation frequency, 12 pulses/min). The positive lusitropic effects of alpha- and beta-adrenoceptor stimulations were studied under isotonic and isometric conditions. Data are mean percentages of baseline +/- SEM.

RESULTS

In control groups, phenylephrine (134 +/- 8%; P < 0.05) and isoproterenol (171 +/- 7%; P < 0.05) induced a positive inotropic effect. Isoflurane enhanced the positive inotropic effects of phenylephrine (185 +/- 10%; P < 0.05) and of isoproterenol (203 +/- 11%; P < 0.05). Sevoflurane enhanced the positive inotropic effects of phenylephrine (187 +/- 10%; P < 0.05) and of isoproterenol (228 +/- 11%; P < 0.05). These potentiations were similar to those previously reported with halothane. Isoflurane and sevoflurane did not modify the positive lusitropic effects under low and high loads of isoproterenol.

CONCLUSION

Although isoflurane and sevoflurane have moderate negative inotropic effects, they potentiated the positive inotropic effects of alpha- and beta-adrenoceptor stimulations but did not modify the positive lusitropic effects of beta-adrenoceptor stimulation.

Myocardial effects of halothane and isoflurane in hamsters with hypertrophic cardiomyopathy

BACKGROUND

The effects of halothane and isoflurane on myocardial contraction and relaxation in diseased myocardium are not completely understood.

METHODS

The effects of equianesthetic concentrations of halothane and isoflurane on inotropy and lusitropy in left ventricular papillary muscles of healthy hamsters and those with genetically induced cardiomyopathy (strain BIO 14.6) were investigated in vitro (29 degrees C; pH 7.40; Ca2+ 2.5 mM; stimulation frequency, 3/min) in isotonic and isometric conditions.

RESULTS

Halothane induced a negative inotropic effect that was greater in cardiomyopathic than in healthy hamsters (1.5 vol%, active isometric force (AF): 19 +/- 8% vs. 28 +/- 11% of control values; P < 0.05). Isoflurane induced a negative inotropic effect that was greater in cardiomyopathic than in healthy hamsters (2.0 vol%, AF: 64 +/- 13% vs. 75 +/- 11% of control values; P < 0.01). However, the negative inotropic effects of halothane and isoflurane were not different for cardiomyopathic or healthy hamsters when their concentrations were corrected for minimum alveolar concentration (MAC) values in each strain. Halothane induced a negative lusitropic effect under low load, which was more important in cardiomyopathic hamsters, suggesting a greater impairment in calcium uptake by the sarcoplasmic reticulum. In contrast, isoflurane induced a moderate positive lusitropic effect under low load in healthy but not in cardiomyopathic hamsters. Halothane and isoflurane induced no significant lusitropic effect under high load.

CONCLUSIONS

Halothane and isoflurane had greater negative inotropic effects in cardiomyopathic than in healthy hamsters. Nevertheless, no significant differences in their inotropic effects were noted when concentrations were correlated as a multiple of MAC in each strain.