Surgical treatment of spondylodiscitis in critically ill septic patients

PURPOSE

Surgical procedures in critically ill patients with spondylodiscitis are challenging and there are several controversies. Here, we present our experience with offering surgical intervention early in critically ill septic patients with spondylodiscitis.

METHOD

After we introduced a new treatment paradigm offering early but limited surgery, eight patients with spondylodiscitis complicated by severe sepsis and multiple organ failure underwent urgent surgical treatment over a 10-year period. Outcome was assessed according to the Barthel index at 12-month follow-up and at the last available follow-up (mean 89 months).

RESULTS

There were 7 men and 1 woman, with a mean age of 62 years. The preoperative ASA score was 5 in 2 patients, and 4 in 6 patients. Six of them presented with high-grade paresis, and in all of them, spondylodiscitis with intraspinal and/or paravertebral abscesses was evident in MR imaging studies. All patients underwent early surgery (within 24 h after admission). The median time in intensive care was 21 days. Out of the eight patients, seven survived. One year after surgery, five patients had a good outcome (Barthel index: 100 (1); 80 (3); and 70 (1)). At the last follow-up (mean 89 months), 4 patients had a good functional outcome (Barthel index between 60 and 80).

CONCLUSION

Early surgical treatment in critically ill patients with spondylodiscitis and sepsis may result in rapid control of infection and can provide favorable long-term outcome. A general strategy of performing only limited surgery is a valid option in such patients who have a relatively high risk for surgery.

[Economics of operating room use at a university eye hospital]

BACKGROUND

In ophthalmologic surgery, there are usually short operation times and thus many changes between the individual operations, which are not subject to remuneration. As in maximum care hospitals consecutive different operations with different durations are often performed, emergency operations have to be inserted and further training of colleagues is practiced, it is particularly important to generate the shortest possible transfer times in order to have both sufficient operation time and to be able to treat as many cases as possible. The aim of this work is to evaluate the efficiency of the surgical performance of a university eye hospital.

MATERIAL AND METHOD

The surgeries performed in 2021 at the MHH Eye Clinic were evaluated with respect to the spectrum, number, surgery duration, transfer times and process times. In terms of personnel, each operating room was staffed with one assistant anesthesiologist, one nurse anesthetist, two operating room nurses, one surgeon, and 20% senior anesthesiologist supervision. Based on a theoretical concept, which provides an increased staffing ratio while maintaining the same infrastructure, it was calculated how many more surgeries could be performed if the transfer time was halved and whether the additional financial expense could be compensated.

RESULTS

With a total of n = 2712 surgeries performed during regular duty hours (244 working days) in 2 operating rooms (average daily n = 11.1; weekly n = 53.6 and monthly n = 237.1), the average surgery duration was 37 min and the transition time 43 min. This means that the operating rooms were used for surgery for 51% of the total operating time. Main procedures were vitrectomy with n = 1350 and cataract surgery with n = 1308. The new personnel concept provided one additional operating room nurse per operating room and one additional anesthesiologist for both operating rooms. The additional costs for this personnel expenditure were calculated at approx. 300,000 € per year. The halving of the transfer time from 43 min to about 21 min through possible overlapping induction and parallel work, which was not possible until now, results in an additional operation time of about 100 min per operating room, so that at least 4 additional operations can be planned and performed. In this way, with stringent implementation and the same spatial structures with stable fixed costs, n = 976 more operations could be performed, which, minus the personnel costs, the additional material costs for surgery and anesthesia of 557,042 € and the inpatient hotel costs of 600,663 €, with an average length of stay of 2.8 days, would result in an additional revenue of about 2.4 times the additional personnel costs at the current flat rate of 3739.40 € and an average case mix index of the MHH Eye Hospital of 0.649 (total revenue: 2,155,449 €; profit margin II: 701,389 €) for the considered surgical patient collective in 2021.

CONCLUSION

An increase of the personnel expenditure in the operating room for surgical subjects such as ophthalmology with shorter interventions and many changes is economically worthwhile also for a large hospital in order to enable and optimize overlapping transfers of anesthesia and surgical care. This should therefore also be considered separately, contrary to standardized staffing of the overall hospital, in order to use existing resources with their fixed costs as optimally as possible.

Routine postoperative admission to the neurocritical intensive care unit after microvascular decompression: necessary or can it be abandoned?

Postoperative neurocritical intensive care unit (NICU) admission of patients who underwent craniotomy for close observation is common practice. In this study, we performed a comparative analysis to determine if there is a real need for NICU admission after microvascular decompression (MVD) for cranial nerve disorders or whether it may be abandoned. The present study evaluates a consecutive series of 236 MVD surgeries performed for treatment of trigeminal neuralgia (213), hemifacial spasm (17), vagoglossopharyngeal neuralgia (2), paroxysmal vertigo (2), and pulsatile tinnitus (2). All patients were operated by the senior surgeon according to a standard protocol over a period of 12 years. Patients were admitted routinely to NICU during the first phase of the study (phase I), while in the second phase (phase II), only patients with specific indications would go to NICU. While 105 patients (44%) were admitted to NICU postoperatively (phase I), 131 patients (56%) returned to the ward after a short stay in a postanaesthesia care unit (PACU) (phase II). Specific indications for NICU admission in phase I were pneumothorax secondary to central venous catheter insertion (4 patients), AV block during surgery, low blood oxygen levels after extubation, and postoperative dysphagia and dysphonia (1 patient, respectively). There were no significant differences in the distribution of ASA scores or the presence of cardiac and pulmonary comorbidities like congestive heart failure, arterial hypertension, or chronic obstructive pulmonary disease between groups. There were no secondary referrals from PACU to NICU. Our study shows that routine admission of patients after eventless MVD to NICU does not provide additional value. NICU admission can be restricted to patients with specific indications. When MVD surgery is performed in experienced hands according to a standard anaesthesia protocol, clinical observation on a neurosurgical ward is sufficient to monitor the postoperative course. Such a policy results in substantial savings of costs and human resources.

Effect of mannitol on platelet function during elective craniotomy in adult patients with brain tumor

BACKGROUND

Mannitol is used in the treatment of raised intracranial pressure (ICP). The aim of this study was to investigate whether mannitol (MAN) leads to a relevant deterioration in platelet function in routine neurosurgical procedures.

METHODS

Thirty-eight patients undergoing elective craniotomy due to a brain tumor with elevated ICP were included. After induction of anaesthesia a blood sample was taken (T1). The patients then received 1 g-kg-1 MAN within 30 minutes. The second blood sample (T2) was obtained 60 minutes after T1. Blood samples were examined by means of aggregometry (Multiplate®) and PFA-100® tests.

RESULTS

No patient had clinical signs of increased bleeding. We could not find any deterioration in the aggregometry using Multiplate®, neither in the adenosinediphosphate (ADP), the arachidonic acid (ASPI), or the thrombin receptor activating protein (TRAP) test. PFA-100® closing times (cT) showed a significant prolongation between T1 and T2: collagen/adenosindiphosphate (COL/ADP) test 79s [70/99] and 91s [81/109]; p=0.002); collagen/epinephrine (COL/EPI) test 109s [92/129] and 122s [94/159]; p=0.0004). A subgroup analysis showed that the patients who received isotonic balanced infusions only, had no prolongation of cT, whereas the patients who received additionally gelatine solution had a significant prolongation.

COL/ADP

78s [70/98] and 91s [82/133]; p=0.0004). COL/EPI: test 111s [92/128] and 127s [103/146]; p=0.0026). Except for individual outliers, the measured values were in the normal range.

CONCLUSIONS

In this study, we found no clinically relevant deterioration of platelet function in neurosurgical patients with increased ICP after administration of MAN. Changes that occurred were all within normal ranges.

Analysis of risk factors for venous air embolism in the semisitting position and its impact on outcome in a consecutive series of 740 patients

OBJECTIVE

Routine use of the semisitting position, which offers several advantages, remains a matter of debate. Venous air embolism (VAE) is a potentially serious complication associated with the semisitting position. In this study, the authors aimed to investigate the safety of the semisitting position by analyzing data over a 20-year period.

METHODS

The incidence of VAE and its perioperative management were analyzed retrospectively in a consecutive series of 740 patients who underwent surgery between 1996 and 2016. The occurrence of VAE was defined by detection of bubbles on transthoracic Doppler echocardiography (TTDE) or transesophageal echocardiography (TEE) studies, a decrease of end-tidal CO2 (ETCO2) by 4 mm Hg or more, and/or an unexplained drop in systolic arterial blood pressure (≥ 10 mm Hg). From 1996 until 2013 TTDE was used, and from 2013 on TEE was used. The possible risk factors for VAE and its impact on surgical performance were analyzed.

RESULTS

There were 404 women and 336 men with a mean age at surgery of 49 years (range 1-87 years). Surgery was performed for infratentorial lesions in 709 patients (95.8%), supratentorial lesions in 17 (2.3%), and cervical lesions in 14 (1.9%). The most frequent pathology was vestibular schwannoma. TEE had a higher sensitivity than TTDE. While TEE detected VAE in 40.5% of patients, TTDE had a detection rate of 11.8%. Overall, VAE was detected in 119 patients (16.1%) intraoperatively. In all of these patients, VAE was apparent on TTDE or TEE. Of those, 23 patients also had a decrease of ETCO2, 18 had a drop in blood pressure, and 23 had combined decreases in ETCO2 and blood pressure. VAE was detected in 24% of patients during craniotomy before opening the dura mater, in 67% during tumor resection, and in 9% during wound closure. No risk factors were identified for the occurrence of VAE. Two patients had serious complications due to VAE. Surgical performance in vestibular schwannoma surgery was not affected by the presence of VAE.

CONCLUSIONS

This study shows that the semisitting position is overall safe and that VAE can be managed effectively. Persistent morbidity is very rare. The authors suggest that the semisitting position should continue to have a place in the standard armamentarium of neurological surgery.

Training of airway management for anesthesia teams - Measurement of transfer into daily work routine by questionnaire

THEORY

Problems in airway management are rare in anesthesia but when they occur, they have serious consequences for the patient. For this reason, training is recommended for professionals involved in anesthetic care. Here we investigated, if a newly developed technical/ non-technical hybrid airway training would be relevant for daily practice in a tertiary referral hospital.

HYPOTHESES

We hypothesized that: (a) both parts of the validated questionnaires meet the quality criteria for the application in anesthesia teams, (b) even though the team regularly deals with airway management, airway management training is relevant to all professions and (c) contents of the developed training can be integrated into the behaviour of the teams.

METHOD

In this observational study, 104 professionals took part in a one-day technical/non-technical hybrid airway training programme. Participants received a questionnaire six months after training, based on selected scales of the validated tools; "Training Evaluation Inventory" and "Transfer Climate Questionnaire".

RESULTS

The scales of "perceived usefulness", "task cues" and "positive reinforcement" showed good internal consistency and all were rated higher than 3.9 on a 5-point Likert scale (1=complete rejection; 5=fullest approval). The scale "negative reinforcement and punishment" showed satisfactory internal consistency for physicians (rated 2.75 ± 0.8). By removing an item in each case, the scales "attitude towards training" (rated 4.93 ± 0.2) and "extinction" (rated 3.02 ± 0.8) showed satisfactory internal consistency for nurses and anesthetic technicians. "Social Cues" did not meet qualitative criteria. There was no difference in the assessment by the professional groups.

CONCLUSIONS

The presented training course was perceived as useful by both professional groups equally, which supported the interprofessional concept. The content was positively reinforced in practice six months after training and is relevant for professionals who are regularly confronted with the topic "airway management". Scales which meet qualitative criteria for only one profession and the scale "social cues" should be reconsidered in the context of an interprofessional team.

[Complications and success rates of subclavian vein catheterization depending on experience]

BACKGROUND

The infraclavicular puncture of the subclavian vein is a standard procedure for anesthetists. Meanwhile the literature and recommendations are clear and the use of real-time ultrasound guidance is the standard procedure; however, anesthetists will always get into special circumstances were they have to use the landmark technique, so this competence must be preserved. Feared complications of infraclavicular subclavian vein puncture are pneumothorax and arterial puncture. Up to now there is no clear learning curve for the infraclavicular subclavian vein puncture in the landmark technique performed by anesthetists.

OBJECTIVE

The aim of this study was to examine the influence of the puncture experience on the success rate and mechanical complications, such as pneumothorax and arterial puncture in patients who received an infraclavicular subclavian vein puncture with the landmark technique. Three levels of experience were defined for comparison: inexperienced 0-20 punctures, moderately experienced 21-50 and experienced over 50 punctures.

MATERIAL AND METHODS

Post hoc analysis of a previously published noninferiority study to examine the influence of ventilation on the pneumothorax rate in the subclavian vein puncture using the landmark technique. This analysis included 1021 anesthetized patients who were included in the original study between August 2014 and October 2017. Demographic data as well as the number of puncture attempts, puncture success, the overall rate of mechanical complications, pneumothorax rate and arterial puncture rates were calculated.

RESULTS

The overall rate of mechanical complications (pneumothorax + arterial puncture) was significantly higher in the inexperienced group (0-21) compared to the experienced group (>50, 15% vs. 8.5%, respectively, p = 0.023). This resulted in an odds ratio of 0.52 (confidence interval, CI: 0.32-0.85, p = 0.027). Likewise, the rate of puncture attempts in the group of inexperienced (0-20) with 1.85 ± 1.12 was significantly higher than in the group of experienced (>50, 1.58 ± 0.99, p = 0.004) and resulted in an odds ratio of 0.59 (CI: 0.31-0.96, p = 0.028). Although the puncture attempts of the moderately experienced (21-50) compared to the inexperienced (0-20) was not significant lower, we found an odds ratio of 0.69 (CI: 0.48-0.99, p = 0.042). The rate of successful puncture was 95.1% in the experienced group versus 89.3% in the inexperienced group (p = 0.001), which resulted in an odds ratio of 2.35 (CI: 1.28-4.31, p = 0.018). When viewed individually, no significant differences were found for pneumothorax and arterial puncture.

CONCLUSION

In this post hoc analysis of the puncture of the subclavian vein using the landmark technique, we found a significant reduction of puncture attempts and overall mechanical complications. At least 50 punctures seem to be necessary to achieve the end of the learning curve; however, the landmark technique should only be used under special circumstances, when real-time ultrasound is not available. Anesthetists who want to complete their repertoire and learn the landmark technique should always perform a static ultrasound examination before starting the puncture in order to reduce complications due to anatomical variations or thrombosis.

[Cost unit accounting of strabismus surgery at a university eye hospital]

BACKGROUND

Strabismus surgery is frequently carried out in university centers. The aim of this work was to calculate the costs of strabismus surgery at a university hospital and to assess the remuneration of costs for outpatient procedures.

MATERIAL AND METHODS

Of all strabismus surgeries at the Hanover Medical School in the years 2018 and 2019, relevant surgical data, such as patient age, number of muscles operated on, incision to suture time, attendance time of the surgeons and anesthetists as well as the nursing staff, were evaluated based on the clinics own information system. During this process, the costs for personnel, material, room rental charges and overheads were computed applying cost unit accounting.

RESULTS

A total of 302 operations (inpatient proportion 92.1%) were carried out in most cases with the patient under general anesthesia. The mean patient age was 31 years (median 26 years), with 33 patients being children under 6 years of age. On average 1.84 muscles were treated per intervention. The mean incision to suture time was 51.5 min, mean anesthesia time was 85 min, the attendance time of surgical as well as anesthesia nursing staff each accounted for 104 min, the additional time in the postanesthesia care unit added 66 min. Average personnel costs originating from the overall process amounted to 642.14 €, with the addition of 109.23 € for material and medication (surgery and anesthesia) and costs for cleaning and room rental (including overheads) of 178.71 €. Therefore, the overall costs of an average strabismus surgery in our collective added up to 930.08 € (minimum 491.01 €, maximum 1729.29 €). Cost accounting of subgroups yielded substantially higher costs for anesthesia in children as well as for higher numbers of muscles operated on due to different treatment duration (37 min for 1 muscle to 72 min for 3 muscles) and anesthesia time, especially in children <6 years of age (on average 22 min longer than adults and children >5 years; the differences being 11 min for 1 muscle, 25 min for 2 muscles and 30 min for 3 or more muscles). The pure costs of a strabismus surgery at this clinic seem on average to exceed the revenues for strabismus surgery in the outpatient sector calculated by the German uniform evaluation benchmark (EBM) by about a factor of 2.

CONCLUSION

It could be shown that the purely economically calculated costs for strabismus surgery at a university clinic are significantly higher than the revenues achieved in the outpatient sector according to paragraph 115b, section 1, of the Social Security Act V (SGB V). Under these circumstances, such operations cannot be performed in a cost-effective manner.

[Catheterization of the subclavian vein and the risk of pneumothorax : Mechanical ventilation increases the risk of pneumothorax during infraclavicular landmark-guided subclavian vein puncture: a prospective randomized study]

BACKGROUND

Infraclavicular subclavian vein (SCV) catheterization is a standard procedure in anesthesia and intensive care. There is a lack of evidence on how mechanical ventilation during venipuncture of the SCV influences pneumothorax rates.

OBJECTIVE

Primary hypothesis: non-inferiority of continuing vs. discontinuing mechanical ventilation during infraclavicular puncture of the SCV with respect to the pneumothorax rate.

MATERIAL AND METHODS

This prospective, randomized and single-blinded study was approved by the local ethics committee. A total of 1021 eligible patients who underwent cranial neurosurgery in 2 different university hospitals were assessed between August 2014 and October 2017. Patients were randomly assigned to two groups directly before induction of anesthesia. Intervention groups for venipuncture of the SCV were mechanical ventilation: tidal volume 7 ml/kg ideal body weight, positive end expiratory pressure (PEEP) ideal body weight/10, n = 535, or apnea: manual/spontaneous, APL valve 0 mbar, n = 486. Patients and the physicians who assessed pneumothorax rates were blinded to the intervention group. Venipuncture was carried out by both inexperienced and experienced physicians.

RESULTS

The pneumothorax rate was significantly higher in the mechanical ventilation group (2.2% vs. 0.4%; p = 0.012) with an odds ratio (OR) of 5.63 (95% confidence interval, CI: 1.17-27.2; p = 0.031). A lower body mass index (BMI) was associated with a higher pneumothorax rate, OR 0.89 (95% CI: 0.70-0.96; p = 0.013).

CONCLUSION

In this study landmark-guided infraclavicular SCV catheterization was associated with a significantly higher rate of pneumothorax when venipuncture was performed during mechanical ventilation and not in apnea. If a short phase of apnea is justifiable in the patient, mechanical ventilation should be discontinued during the venipuncture procedure.

[Anaesthesia in Patients after Transplantation of Solid Abdominal Organs]

An ever-evolving and successful transplantation medicine is providing a large number of living patients after solid organ transplantation. Anaesthetists should therefore be prepared to come into contact with such a patient. In addition to the preoperative assessment of the pre-existing diseases, including the function of the transplanted organ, immunosuppression also plays an important role. Immunosuppression must always be continued perioperatively. Strict adherence to all hygienic regulations is essential in these patients due to immunosuppression and the associated increased risk of infection and sepsis. This includes the strict risk-benefit assessment of all invasive procedures.There are no significant differences between the anaesthetic approaches and agents in transplant and non-transplant patients. However, in the first group, homeostasis of all organ systems should be more focused on.

Changes of collective orientation through a medical student's anaesthesia simulation course - simulation-based training study with non-technical skills debriefing versus medical debriefing

BACKGROUND

Non-technical skills (NTS) are known to have a positive impact on quality of medical care. The team performance enhancing behaviour, as an example for NTS, is termed "Collective Orientation" (CO). In this study, we investigated the effect of a simulator-based anaesthesia training upon student's CO in relation to medical and TeamGAINS (guided team self-correction, advocacy-inquiry and systemic-constructivist techniques) debriefing. We hypothesized (a) the scale collective orientation, as demonstrated in other team setting, is applicable to fourth year German medical students, (b) collective orientation increases by a four-hour anaesthesia simulation course, (c) the change in collective orientation can be influenced by type of debriefing.

METHOD

All classes of an anaesthesia module (4th year medical students) were randomized into two groups. Students took part in a four-hour simulation course with team scenarios, supported by a simulated nurse. In group one the trainer focused on a debriefing on medical problems and in group two, a debriefing according to the specifications of the TeamGAINS concept was conducted. The primary outcome was the mean difference between the collective orientation measured (via questionnaires) immediately before (T1) and after (T2) training.

RESULTS

Cronbach's alpha for all scales and measurement points was higher than 0.72. The scale "affiliation" decreases in the group medical debriefing MD = 0.1 (p = 0.008; r = 0.31) and was unchanged in the group TeamGAINS. "Dominance" increases in both groups. The values were MD = 0.19 (p = 0.003; r = 0.25) for medical debriefing and MD = 0.22 (p = 0.01; r = 0.40) for TeamGAINS debriefing.

CONCLUSION

The collective orientation questionnaire can be applied to fourth year medical students. Simulation courses influence the attitude towards teamwork. The influence is negatively to the subscale "affiliation" by a "medical debriefing" and independently regardless of the nature of the debriefing for the subscale "dominance". We recommend a debriefing for medical students using the TeamGAINS approach to clarify the connection between the individual performance and non-technical skills. Anaesthesia simulation courses have the potential being a part of a longitudinal education curriculum for teaching non-technical skills.

Mannitol and the Combination of Mannitol and Gelatin Impair Whole Blood Coagulation and the Platelet Function In Vitro

Objective

Mannitol 20% and succinylated gelatin 4% are routinely used in neurosurgical procedures. The aim of this in vitro study was to explore the influence of both agents on blood coagulation and platelet function.

Methods

Blood from 21 healthy volunteers was obtained and then diluted so as to form five groups: (1) 7% dilution with mannitol; (2) 10% dilution with gelatin; (3) 17% dilution with isotonic balanced electrolyte solution; (4) 17% dilution with mannitol+gelatin; and (5) undiluted blood. The extrinsic thrombelastometry (EXTEM) and fibrin thrombelastometry (FIBTEM) tests were examined by rotational thrombelastometry via ROTEM®, and thrombocyte aggregometry with the aspirin inhibiting- (ASPI), adenosine diphosphate- (ADP), and thrombin-activating protein (TRAP) tests performed by Multiplate.

Results

In the EXTEM test clot formation time, the alpha angle, and maximum clot firmness were significantly reduced by mannitol and the combination of mannitol with gelatin. The platelet function tested in the ADP test was also significantly reduced with this combination.

Conclusion

In this in vitro study, clinically relevant dilutions of mannitol and gelatin showed a significant inhibition of whole blood coagulation and the platelet function, which could be detrimental in neurosurgical settings.

Albumin combined with Mannitol impairs whole blood coagulation and platelet function in vitro

BACKGROUND

The indication of hydroxyethyl starch is currently under critical discussion and albumin 5% (ALB) has an increasing use in the operating theatre. Therefore, ALB is routinely used in neurosurgical procedures and often combined with mannitol 20% (MAN). Purpose of this in vitro study was to determine the influence of the combination of MAN and ALB on blood coagulation and platelet function.

METHODS

22 healthy volunteers were included into this study and 21 analysed. Blood was obtained and diluted into five groups: (1) 7% dilution with MAN, (2) 10% dilution with ALB (3) 17% dilution with isotonic balanced electrolyte solution, (4) 17% dilution with MAN + ALB and (5) undiluted blood as control group (CON). Rotational thrombelastometry via ROTEM® (EXTEM, FIBTEM-Test) and thrombocyte aggregometry via Multiplate® (ASPI, ADP and TRAP-test) were used to detect differences within the intervention groups and compared to the control group.

RESULTS

The maximum clot firmness in the FIBTEM test decreased under the normal range with the combination of MAN+ALB: 8mm (5.5-11) compared to CON: 15mm (12.5-20), p<0.05. Platelet function (ADP-test) showed significant decreases for ALB: 51 AUC (40-84) and MAN+ALB: 54 AUC (41-68) compared to CON: 92 AUC (75-101), p<0.05. Except in clotting time all other EXTEM tests of MAN+ALB subgroup showed significant impairment on blood coagulation compared to the control group.

CONCLUSIONS

In this in vitro study clinically relevant dilutions of MAN+ALB showed a significant inhibition of blood coagulation and platelet function. Further in vivo studies are necessary to confirm these results.

Impact of the laryngeal tube as supraglottic airway device on blood flow of the internal carotid artery in patients undergoing general anaesthesia

INTRODUCTION

Laryngeal tubes (LT) are supraglottic airway devices routinely used in emergency airway management. During cardiac arrest in a swine model, the carotid artery blood flow is reduced after insertion of a LT. A compression of the internal carotid (ICA) artery by the inflated cuff was shown. Up to now there is no information if the LT has similar effects in humans with possible negative implications for use of the LT in case of cardiac arrest.

OBJECTIVE

We hypothesized that the use of a LT in humans significantly reduces the blood flow in the ICA compared facemask ventilation. A significant reduction was defined as a 25% reduction from baseline values.

MATERIAL AND METHODS

After induction of general anaesthesia and reaching a haemodynamic steady state (stable heart rate >50/min and mean arterial pressure >60 mmHg), blood flow within the ICA was measured via doppler sonography during pressure-controlled ventilation with facemask-, laryngeal tube- and laryngeal mask.

RESULTS

We found no differences in the carotid blood flow. Neither between the facemask ventilation (right side 419 ± 159 ml min^-1, left side 355 ± 120 ml min^-1) and the laryngeal tube ventilation (right side 400 ± 131 ml min^-1, left side 384 ± 124 ml min^-1. p = 0.86 and p = 0.12), nor the facemask-ventilation and the laryngeal mask ventilation (right ICA 415 ± 150 ml min^-1, left ICA 485 ± 274 ml min^-1, p = 0.49 and 0.26).

CONCLUSIONS

In humans the LT does not impair blood flow of the internal carotid artery during ventilation in general anaesthesia. Further studies are needed to confirm our findings under the conditions of cardiac arrest.

Venous air embolism in the sitting position in cranial neurosurgery: incidence and severity according to the used monitoring

BACKGROUND

There is an ongoing debate about the sitting position (SP) in neurosurgical patients. The SP provides a number of advantages as well as severe complications such as commonly concerning venous air embolism (VAE). The best monitoring system for the detection of VAE is still controversial.

METHODS

In this retrospective analysis we compared 208 patients. Transesophageal echocardiography (TEE) or transthoracic Doppler (TTD) were used as monitoring devices to detect VAE; 101 cases were monitored with TEE and 107 with TTD.

RESULTS

The overall incidence of VAE was 23% (TTD: 10%; TEE: 37%), but the incidence of clinically relevant VAE (drop in end-tidal carbon dioxide above 3 mmHg) was higher in the TTD group (9 out of 17 VAE, 53%) compared to the TEE group (19 out of 62 VAE, 31%). None of the patients with recorded VAE had clinically significant sequelae.

CONCLUSIONS

In this small sample we found more VAE events in the TEE group, but the incidence of clinically relevant VAE was rare and comparable to other data. There is no consensus in the definition of clinically relevant VAE.

[Anaesthesia in patients after transplantation]

More than 17000 patients currently live in Germany who have had organ transplants. The implications of this for the anaesthetists are that they are very likely to be confronted by such a patient at some point during their active career. Besides the preoperative assessment which includes that of the function of the transplanted organ, appropriate immunosuppression poses a particular challenge. Close collaboration with both patients and their transplant specialists is essential to preempt the perioperative consequences and plan continuation of immunosuppression. Strictly aseptic measures are mandatory as well as detailed evaluation of the risk-benefit balance of all invasive procedures.There are no significant differences between the anaesthetic approaches and agents in transplant and non-transplant patients. However, in the latter group, homeostasis of all organ systems should be more focused on.

Post-resuscitation haemodynamics in a novel acute myocardial infarction cardiac arrest model in the pig

BACKGROUND AND OBJECTIVES

Although a considerable amount of promising experimental research has been performed on cardiopulmonary resuscitation, clinical data indicate an ongoing limited outcome in human beings. One reason for this discrepancy could be that experimental studies use healthy animals whereas most human beings undergoing cardiopulmonary resuscitation suffer from acute or chronic myocardial dysfunction. To overcome this problem, we sought to develop a new model of myocardial infarction, that is easy to perform in all kind of laboratories and compromises on the myocardial function significantly.

METHODS

Following approval by the local authorities, 14 domestic pigs were instrumented for measurement of arterial, central venous, left atrial and left ventricular pressures. Myocardial infarction was induced in eight pigs by clipping the circumflex artery close to its origin from the left coronary artery (infarction group; n = 8). Six animals (no infarction group, n = 6) served as no-infarct controls. Following a 4-min period of cardiac arrest, internal cardiac massage was performed in these two groups, and haemodynamics were recorded during the first 30 min of reperfusion.

RESULTS

All animals were resuscitated successfully. Compared to the no-infarction group, the infarction group showed significantly decreased myocardial contractility, coronary perfusion pressure and cardiac index (30 min after restoration of spontaneous circulation: infarction group: 57 +/- 7 and 89 +/- 19 mL min-1 kg-1 in the no-infarction group; mean +/- SD; P < 0.05) during reperfusion. Two animals from the infarction group (25%), but none of the animals in the no-infarction group, died during the reperfusion period.

CONCLUSION

These data demonstrate that clipping of the circumflex artery leads to a reduced myocardial performance after successful resuscitation, whereas the rate of restoration of spontaneous circulation is not reduced. Therefore, this set-up provides a reproducible model for future studies of post-resuscitation haemodynamics and treatment.

Milrinone combined with vasopressin improves cardiac index after cardiopulmonary resuscitation in a pig model of myocardial infarction

BACKGROUND

Milrinone used for acute cardiac insufficiency could be of interest during cardiopulmonary resuscitation because of its positive inotropic effects. In this study, the combination of milrinone-vasopressin was compared with epinephrine and vasopressin, as well as with the combination of epinephrine-vasopressin, in reference to hemodynamics.

METHODS

Thirty-two pigs underwent ligation of the circumflex coronary artery and induction of ventricular fibrillation lasting for 4 min. Cardiopulmonary resuscitation was performed after randomization to one of four groups: epinephrine (30-microg/kg bolus), vasopressin (0.4-U/kg bolus), epinephrine-vasopressin (15-microg/kg epinephrine bolus, 0.2-U/kg vasopressin bolus), or milrinone-vasopressin (0.4-U/kg vasopressin bolus, 50-microg/kg milrinone bolus over 5 min and a continuous infusion of 0.4 microg.kg.min). The hemodynamic variables were measured before cardiopulmonary resuscitation as well as 4, 8, 15, and 30 min after return of spontaneous circulation.

RESULTS

All animals were resuscitated successfully. The animals of the milrinone-vasopressin group displayed significantly (P<0.05) higher cardiac index values (30 min after return of spontaneous circulation: epinephrine, 65.8+/-13.2; vasopressin, 70.7+/-18.3; epinephrine-vasopressin, 69.1+/-36.2; milrinone-vasopressin, 120.7+/-34.8 ml.min.kg) without a decrease in mean arterial pressure or coronary perfusion pressure.

CONCLUSIONS

The combination of vasopressin-milrinone as compared with epinephrine during cardiopulmonary resuscitation leads to an improved cardiac index without relevant decrease of mean arterial pressure or coronary perfusion pressure.

Low-flow perfusion via the innominate artery during aortic arch operations provides only limited somatic circulatory support☆

BACKGROUND

Aortic arch operations in pediatric patients using low-flow perfusion techniques have been standardized to a certain degree, but some of the often-stated beneficial effects have never been proven. Especially, the existence or efficacy of any subdiaphragmal perfusion still remains unclear.

METHODS

Twenty-six newborn male piglets (10-15 kg) underwent aortic arch surgery under general anesthesia using either low-flow perfusion via the innominate artery (LF, 30 ml/(kg min), 25 degrees C, n=12) or conventional deep hypothermic circulatory arrest (DHCA, 20 degrees C, n=14). Cortical somatosensory-evoked potentials (SSEPs), carotid, and subdiaphragmal blood flows were measured. The animals of both groups have been randomized to either pH-stat or alpha-stat management on cardiopulmonary bypass (CPB).

RESULTS

During low-flow perfusion via the innominate artery only negligible flows of maximum 1-3 ml/min in the femoral arteries were detected, whereas the right carotid artery flow doubled. During reperfusion, serum-lactate and aspartate amino-transferase (AST) levels were significantly higher compared to the circulatory arrest group, whereas alanine amino-transferase (ALT), gamma-glutamyl transpeptidase (gamma-GT), AP, and creatinine did not show any significant differences. Cortical SSEP returned to preoperative values in all but two low-flow animals. There was no return of SSEP in all piglets operated under deep hypothermic circulatory arrest (p<0.01).

CONCLUSION

Compared to DHCA, low-flow perfusion via the innominate artery provides superior neuroprotection despite higher tissue temperatures. Although collateral blood flow via the subclavian artery and the circulus arteriosus willisii has often been presumed, only 'trickle-flow' with some protective potential was detectable in the femoral arteries during low-flow perfusion. Origin of elevated lactate and AST levels seems to be the lower limbs.

Perioperative monitoring of circulating and central blood volume in cardiac surgery by pulse dye densitometry

OBJECTIVE

To determine perioperative changes in circulating (BVI) and central blood volume (CBVI) by a new dye dilution technique using pulse dye densitometry.

DESIGN AND SETTING

Prospective observational study in the cardiac anesthesia and intensive care unit of a university hospital.

PATIENTS

Sixty-six patients undergoing coronary artery bypass surgery.

MEASUREMENTS AND RESULTS

Hemodynamic measurements by the dye dilution method using pulse dye densitometry were performed prior to skin incision and 3.3+/-1.4 h and 17+/-2.7 h after surgery. Based on conventional monitoring the therapeutic goals of hemodynamic therapy were achieved in all of the patients of this study. Despite a marked positive fluid balance which developed during surgery mean BVI decreased significantly after surgery while CBVI remained unchanged. Postoperative BVI deficits vs. preoperative values were observed in 78% of patients; these BVI deficits were profound in 29% of the cases. In contrast, 65% of the individual patients showed no or only minor postoperative changes in CBVI vs. preoperative values.

CONCLUSIONS

Changes in the intravascular volume compartments affected BVI to a greater extent than CBVI. Therefore measuring circulating in addition to central blood volume may be useful to ensure a normal circulating blood volume that can compensate for any change in the central vascular compartment.

Modelling the pharmacodynamic interaction between remifentanil and propofol by EEG-controlled dosing

BACKGROUND AND OBJECTIVE

Knowledge of the pharmacodynamic interaction between remifentanil and propofol is important to permit optimal dosage strategies. We studied this pharmacodynamic interaction using the median power frequency of the processed electroencephalogram as a control parameter for feedback-controlled dosing of propofol.

METHODS

Twenty-one patients were given total intravenous anaesthesia with remifentanil and propofol. During three target-controlled infusion regimens, the target concentrations of remifentanil (5, 10, 15 ng mL(-1)) and propofol dosing were automatically adjusted to keep the median power frequency in the range 2 +/- 0.5 Hz. In each patient and during each remifentanil target concentration, four arterial propofol/remifentanil concentration pairs were measured. The type of interaction was tested using the relative distance from the line of additivity and the isobole was modelled using Bernstein splines.

RESULTS

The results from 13 patients were used for data analysis. The measured remifentanil concentrations during the three targets were (mean +/- SD): 3.6 +/- 0.9, 8.1 +/- 2.5 and 12.4 +/- 2.8 ng mL(-1). The corresponding propofol concentrations were 2.64 +/- 0.86, 2.13 +/- 0.58 and 2.09 +/- 0.58 microg mL(-1). The data were best described with an additive type of interaction and the isobole was estimated using: ((c)Remifentanil/64.2 ng mL(-1)) + ((c)Propofol/2.61 microg mL(-1)) = 1.

CONCLUSIONS

Within the studied concentration range, remifentanil and propofol showed an additive type of pharmacodynamic interaction on the electroencephalogram.

[Emergency management of an acute rupture of a perforated thoracic aortic aneurysm]

The emergency medical service was called to a 60-year-old woman with intensive chest pain, signs of shock, dyspnoea, intermittent paraesthesia of the right leg and disturbance of consciousness. With the diagnosis of an acute rupture of an aneurysm of the thoracic aorta, the patient was stabilised with volume, catecholamines, intubation and mechanical ventilation before being rushed to the preinformed department of cardiovascular surgery. The diagnosis was verified by transesophageal echocardiography immediately and the patient underwent surgery 2 h after onset of symptoms. Despite the rupture of the aorta and a short period of cardiac arrest, the patient recovered totally and could be discharged without any residual problems. This case shows that a ruptured thoracic aortic aneurysm can be survived although the overall mortality of this incident is more than 97%. The essentials of a good outcome are: 1. perfectly coordinated rescue operation which means an emergency medical service which includes the rupture of an aortic aneurysm in the differential diagnosis of acute chest pain, 2. an early verification of the diagnosis by means of transesophageal echocardiography which should also be carried out by anaesthesiologists due to its importance in the differential diagnosis in haemodynamic unstable patients.