Martin Zoremba

Comparison between intubation and the laryngeal mask airway in moderately obese adults

Background: Obesity is a well‐established risk factor for perioperative pulmonary complications. Anaesthetic drugs and the effect of obesity on respiratory mechanics are responsible for these pathophysiological changes, but tracheal intubation with muscle relaxation may also contribute. This study evaluates the influence of airway management, i.e. intubation vs. laryngeal mask airway (LMA), on postoperative lung volumes and arterial oxygen saturation in the early postoperative period.

Forced needle advancement during needle-nerve contact in a porcine model: histological outcome.

BACKGROUND: In this study, we determined whether needle advancement during needle-nerve contact (forced needle-nerve contact) is associated with a higher risk of nerve injury compared with needle-nerve contact without needle advancement (nonforced needle-nerve contact). METHODS: In 8 anesthetized pigs, the brachial plexus nerves underwent forced (0.15 Newton) or nonforced (0.0 Newton) needle-nerve contact without nerve penetration. The grade of nerve injury was histologically assessed using an objective score ranging from 0 (no injury) to 4 (severe injury). RESULTS: Sixty-nine nerves, including controls, were examined. Histology revealed a significant difference between forced and nonforced needle-nerve contact (median [interquartile range] 3 [2–4] vs 2 [1–2]; P = 0.004). Myelin damage and intraneural hematoma occurred only after forced needle-nerve contact. CONCLUSIONS: The severity of structural nerve injury after needle-nerve contact was directly related to force exposure via needle advancement.

The influence of perioperative oxygen concentration on postoperative lung function in moderately obese adults.

Background and objective Obesity aggravates the negative effects of general anaesthesia and surgery on the respiratory system, resulting in decreased functional residual capacity and expiratory reserve volume, and increased atelectasis and ventilation/perfusion (Va/Q) mismatch. High-inspired oxygen concentrations also promote atelectasis. This study compares the effects of perioperative inspired low-oxygen and high-oxygen concentrations on postoperative lung function and pulse oximetry values in moderately obese patients (BMI 25–35). Methods We prospectively studied 142 overweight patients, BMI 25–35, undergoing minor peripheral surgery; they were randomly allocated to receive either low-inspired or high-inspired oxygen concentrations during general anaesthesia. Premedication, general anaesthesia and respiratory patterns were standardized. Arterial oxygen saturation (pulse oximetry) was measured on air breathing. Inspiratory and expiratory lung functions were measured preoperatively (baseline) and at 10 min, 0.5, 2 and 24 h after extubation with the patient supine, in a 30° head-up position. The two groups were compared using repeated-measure analysis of variance and t-test analysis. Results The low-inspired oxygen group had significantly better arterial saturation during the first 24 h (P < 0.01). Mid-expiratory flow 25 values indicating small airway collapse were significantly better in the low-oxygen group at all measurements (P < 0.05). Conclusion We conclude that postoperative lung function and arterial saturation is better preserved by a low-oxygen strategy, although it is not clear whether this has clinical relevance for the prevention of postoperative pulmonary complications.

A simplified risk score to predict difficult intubation: development and prospective evaluation in 3763 patients.

Background and objective Despite the presence of numerous preoperative tests to predict a difficult airway, there is no reliable bedside method. The aim of this study was to create and verify a simplified risk model with an acceptable discriminating power. Methods A total of 3763 patients from two university hospitals were screened for potential risk factors for difficult intubation, defined as needing additional technical or human resources, more than three attempts or duration more than 10 min. A random sample (n = 2509) was subjected to multivariate stepwise logistic regression analysis, and the most powerful independent risk factors were used to build a simplified model that was applied to a validation dataset (n = 1254). Results The following factors (odds ratio) were associated with a difficult intubation: presence of upper front teeth (3.61), history of difficult intubation (2.88), any Mallampati status different from ‘1’ (2.55) or equal to ‘4’ (1.91) and mouth opening less than 4 cm (1.80). The discriminating power of the score was 0.72 (95% confidence interval 0.63–0.81). The likelihood for a difficult intubation increases continuously from 0 (when no risk factor is present) to 2, 4, 8 and 17%, when one, two, three and more than three factors are present. Conclusion The new simplified multivariate risk score for difficult intubation may prove to be useful in clinical practice for predicting a difficult airway. Presence of upper front teeth, a history of difficult intubation, any Mallampati status different from ‘1’ and equal to ‘4’ and mouth opening less than 4 cm are independent risk factors for difficult endotracheal intubation. With each of these risk factors, the likelihood increases from 0 (when no risk factor is present) to 17% (when four or five factors are present).

A comparison of desflurane versus propofol: the effects on early postoperative lung function in overweight patients.

BACKGROUND: In this study, we evaluated the influence of propofol versus desflurane anesthesia in overweight patients on postoperative lung function and pulse oximetry values. METHODS: We prospectively studied 134 patients with body mass indices of 25 to 35 kg/m2 undergoing minor peripheral surgery lasting 40 to 120 minutes. Patients were randomly assigned to receive propofol (total IV anesthesia) or desflurane anesthesia via a tracheal tube targeting bispectral index values of 40 to 60. Premedication, adjuvant drug usage, and ventilation were standardized. We measured oxyhemoglobin saturation and lung function preoperatively (baseline), and at 10 minutes, 0.5 hour, 2 hours, and 24 hours after tracheal extubation. All values were measured with the patient supine, in a 30° head-up position. Changes from preoperative baseline values were first analyzed for the impact of body mass index and type of anesthesia using univariate methods, followed by linear regression and multivariate analysis of variance. RESULTS: Within the first 2 hours after surgery, the propofol group displayed lower oxyhemoglobin saturation (at 2 hours, mean ± SD, 93.8% ± 2.0% vs 94.6% ± 2.1%; P < 0.007) and lung function (forced vital capacity, forced expiratory volume exhaled in 1 second [FEV1], peak expiratory flow, midexpiratory flow [MEF], forced inspiratory vital capacity, and peak inspiratory flow; between 11% and 20% larger reduction from baseline in the propofol group, all P < 0.001) compared with the desflurane group. Even 24 hours after surgery, FEV1, peak expiratory flow, MEF, forced inspiratory vital capacity, and peak inspiratory flow were reduced more in the propofol group (all P < 0.01). At 2 hours after extubation, increasing obesity was associated with decreasing FEV1 and MEF in patients anesthetized with propofol but not desflurane (P < 0.01). CONCLUSION: We conclude that, for superficial surgical procedures of up to 120 minutes, maintenance of anesthesia with propofol impairs early postoperative lung function and pulse oximetry values more than with desflurane. Furthermore, increasing obesity decreases pulmonary function at 2 hours after propofol anesthesia but not after desflurane anesthesia.

Compound imaging technology and echogenic needle design: effects on needle visibility and tissue imaging.

Introduction Needle visualization in ultrasound-guided regional anesthesia can be improved by using needles of echogenic design with higher rate of reflection of ultrasound waves. Imaging solutions such as compound imaging might further improve imaging of both needle and tissue; these effects have not yet been studied. We hypothesized that compound imaging would significantly improve needle visibility, regardless of the insertion angle or needle type used. The effects of compound imaging on needle artifacts and tissue imaging were also investigated. Methods A total of 200 video clips of in-plane needle insertions were obtained in embalmed cadavers with a conventional needle and an echogenic needle at 5 different insertion angles, with both conventional B-mode ultrasound imaging and compound imaging technology. Visibility of the needle shaft and needle tip as well as the needle artifact rate were assessed by a blinded investigator on a 4-point ordinal scale. The effects on tissue image quality and speckle artifacts were also assessed. Stepwise linear regression was performed to differentiate effects on needle visibility scores. Results Imaging of the needle shaft and tip was significantly enhanced when compound imaging technology was used (P < 0.0001). Use of echogenically designed needles or shallow needle insertion angles improved visibility of both shaft and tip (both P < 0.0001). With compound imaging, there are fewer needle artifacts, and tissue imaging quality and speckle artifact rate are significantly improved. Conclusions Compound imaging technology enhances needle imaging with both echogenic and conventional needles. Tissue imaging and speckle artifacts are also optimized. Echogenic needle design results in better needle visibility scores in both B-mode and compound imaging.

Spinalanästhesie – Ambulante Spinalanästhesie – Neue Trends einer alten Technik

Day case surgery is becoming more and more important. In order to perform these services cost-efficiently it is of primary importance to ensure that procedures can be scheduled with the largest possible patient satisfaction. Up to now spinal anaesthesia was of little importance in day case surgery due to prolonged nerve block and negative side effects especially when using long acting local anaesthetics. Since prilocaine and 2-chloroprocaine, two short acting local anaesthetics with a known low incidence of side effects, were recently introduced into clinical practice a reevaluation of spinal anaesthesia in a day case setting according to EMB guidelines still has to be done.

Short term non-invasive ventilation post-surgery improves arterial blood-gases in obese subjects compared to supplemental oxygen delivery - a randomized controlled trial

BackgroundIn the immediate postoperative period, obese patients are more likely to exhibit hypoxaemia due to atelectasis and impaired respiratory mechanics, changes which can be attenuated by non-invasive ventilation (NIV). The aim of the study was to evaluate the duration of any effects of early initiation of short term pressure support NIV vs. traditional oxygen delivery via venturi mask in obese patients during their stay in the PACU.MethodsAfter ethics committee approval and informed consent, we prospectively studied 60 obese patients (BMI 30-45) undergoing minor peripheral surgery. Half were randomly assigned to receive short term NIV during their PACU stay, while the others received routine treatment (supplemental oxygen via venturi mask). Premedication, general anaesthesia and respiratory settings were standardized. We measured arterial oxygen saturation by pulse oximetry and blood gas analysis on air breathing. Inspiratory and expiratory lung function was measured preoperatively (baseline) and at 10 min, 1 h, 2 h, 6 h and 24 h after extubation, with the patient supine, in a 30 degrees head-up position. The two groups were compared using repeated-measure analysis of variance (ANOVA) and t-test analysis. Statistical significance was considered to be P < 0.05.ResultsThere were no differences at the first assessment. During the PACU stay, pulmonary function in the NIV group was significantly better than in the controls (p < 0.0001). Blood gases and the alveolar to arterial oxygen partial pressure difference were also better (p < 0.03), but with the addition that overall improvements are of questionable clinical relevance. These effects persisted for at least 24 hours after surgery (p < 0.05).ConclusionEarly initiation of short term NIV during in the PACU promotes more rapid recovery of postoperative lung function and oxygenation in the obese. The effect lasted 24 hours after discontinuation of NIV. Patient selection is necessary in order to establish clinically relevant improvements.Trial Registration#DRKS00000751; http://www.germanctr.de

Occurrence of Rapid Eye Movement Sleep Deprivation After Surgery Under Regional Anesthesia

BACKGROUND:Sleep disturbances after general surgery have been described. In this study, we assessed rapid eye movement (REM) sleep in patients undergoing knee replacement surgery using a regional anesthetic technique. METHODS:Ambulatory polysomnography (PSG) was performed on 3 nights: the night before surgery (PSG1), the first night after surgery (PSG2), and the fifth postoperative night (PSG3). Postoperative analgesia was maintained with peripheral nerve catheters for the first 3 days and with oral opioids thereafter. In addition, nonsteroidal antiinflammatory drugs were administered. Postoperative pain was monitored using a visual analog scale. RESULTS:PSG was performed in 12 patients, 6 men and 6 women, with a mean age of 61 (±12) years. REM sleep was reduced from PSG1 (median 16.4%) to PSG2 (median 6.3%; P = 0.02). The Hodges-Lehmann estimate for the median reduction is −7.8% (95% confidence interval −14.8% to −0.7%). During PSG3, significantly more REM sleep was detected (median 15.4%) compared with PSG2 (P = 0.01). The Hodges-Lehmann estimate for this median increase is 10.0% (95% confidence interval 1.7%–25.3%). CONCLUSION:Postoperative reduction of REM sleep also occurs after surgery and regional anesthesia.

Hypoxemia after general anesthesia

ZusammenfassungHintergrundStudien aus den Zeiten der klinischen Einführung der Pulsoxymetrie zeigten, dass nach Allgemeinanästhesien ein großer Anteil der Patienten auf dem Weg vom OP in den Aufwachraum (AWR) unter Atmung von Raumluft hypoxämisch [pulsoxymetrisch gemessene Sauerstoffsättigung (SpO2) < 90%] war und dass das Erkennen der Hypoxämie anhand von klinischen Kriterien sehr unzuverlässig ist. Unklarheit besteht darüber, ob die Inzidenz von Hypoxämien trotz modernerer Anästhesieverfahren immer noch so hoch ist, ob sich die Unzuverlässigkeit der Detektion von Hypoxämien nach klinischen Kriterien bestätigt und was die Risikofaktoren für Hypoxämien nach Allgemeinanästhesie sind.MethodenBei 970 in Allgemeinanästhesie operierten Patienten wurde nach dem Transport vom OP in den AWR unter Atmung von Raumluft die SpO2 gemessen, nachdem der betreuende Anästhesist eine Schätzung der SpO2 vorgenommen hatte. Zusammenhänge zwischen biometrischen, operativen und anästhesiologischen Variablen einerseits sowie Hypoxämie andererseits wurden multivariat untersucht.ErgebnisseEs hatten 17% der 959 ausgewerteten Patienten eine SpO2 < 90%; hierbei wiesen 6,6% der Patienten eine SpO2 < 85% auf. Die Hypoxämie wurde in 82% der Fälle nicht erkannt. Unabhängige Einflussfaktoren auf eine Hypoxämie waren: Ausgangssättigung, Body-Mass-Index, Alter, körperlicher Status gemäß Klassifikation der American Society of Anesthesiologists, Differenz zwischen maximalem und minimalem Beatmungsdruck, Beatmungsmodus, Wahl des Opioids, des Relaxans und Verwendung von Lachgas.SchlussfolgerungDurch die Wahl von Anästhetika können Hypoxämien und Sättigungsabfälle günstig beeinflusst werden, ohne dass dadurch diese Problematik vollständig gelöst werden kann, weil die stärksten Risikofaktoren patientenassoziiert sind. Da bislang selbst bei Kenntnis von Risikofaktoren nicht vorherzusagen ist, wer nach Allgemeinanästhesie eine SpO2 < 90% haben wird und überdies die Abschätzung der SpO2 anhand klinischer Kriterien höchst unzuverlässig ist, erscheint der Transport von spontan-atmenden Patienten nach Narkose ohne Überwachung der SpO2 bzw. ohne O2-Gabe überdenkenswert.AbstractBackgroundStudies conducted shortly after the implementation of pulse oximetry (PO) into clinical practice 20–25 years ago revealed that many patients breathing room air during transfer from the operating room (OR) to the post-anesthesia care unit (PACU) directly after general anesthesia (GA) had a peripheral oxygen saturation (SpO2) below 90%. Moreover, it was shown that the detection of hypoxemia by clinical criteria is extremely unreliable. Meanwhile, the use of PO has become part of the obligatory standard monitoring during GA in Germany and many other countries. Likewise, the use of PO is standard care in the PACU although there are no official recommendations. However, for the time period in between, i.e. immediately after GA during transportation of patients from the OR to the PACU, monitoring of the SpO2 in patients breathing room air is neither obligatory in Germany nor are there any official recommendations or guidelines in this respect. Given the introduction of shorter acting anesthetic agents within the last 25 years, the main goal of this study was to explore whether the incidence of hypoxemia in the immediate period after GA is still so high. Additional aims of this study were to examine whether the detection of hypoxemia based on clinical criteria can be confirmed to be very unreliable, what the risk factors for hypoxemia following GA are and how common it is in Germany to transport patients from the OR to the PACU without PO and supplemental oxygen.MethodsIn a prospective observational study 970 patients who underwent a broad spectrum of elective surgery under GA in a university hospital setting were included. The SpO2 was measured at the end of the transfer from the OR to the PACU immediately after the anesthetist who had taken care of the patient during the operation had estimated the SpO2. The association between biometric, surgical and anesthesiological variables on the one hand and hypoxemia as well as a decrease of SpO2 on the other hand were studied using multivariate methods. Finally, a survey including all university hospitals was carried out to find out about the use of PO and oxygen during patient transfer from the OR to the PACU.ResultsOf the 959 patients who were eligible for analysis 17% had a SpO2 < 90% and 6.6% a SpO2 < 85%. Hypoxemia was not recognized in 82% of the patients in whom an assessment based on clinical grounds was carried out. Variables with an independent influence on hypoxemia and decrease of SpO2 were as follows: saturation before induction of GA, body mass index, age, American Society of Anesthesiologists (ASA) physical status, difference between maximum and minimum inspiratory pressure, mode of ventilation, the choice of opioid and muscle relaxant as well as the use of nitrous oxide. Patient-dependent risk factors had the strongest impact on hypoxemia. In about 80% of the university hospitals neither PO nor supplemental oxygen is used during transportation of the patient from the OR to the PACU.ConclusionsThe use of opioids and relaxants with short duration of action may have favorable effects on preventing hypoxemia and decreases of SpO2. These measures will, however, not be sufficient to solve this problem because the highest risk factors for hypoxemia are patient-related. Despite knowing risk factors for oxygen desaturation, it is currently not possible to reliably predict which patients will become hypoxemic or have a decrease of SpO2. Therefore, transportation of patients breathing room air from the OR to the PACU directly after GA without use of PO or supplemental oxygen seems to be questionable in terms of patient safety.BACKGROUND Studies conducted shortly after the implementation of pulse oximetry (PO) into clinical practice 20-25 years ago revealed that many patients breathing room air during transfer from the operating room (OR) to the post-anesthesia care unit (PACU) directly after general anesthesia (GA) had a peripheral oxygen saturation (S(p)O(2)) below 90%. Moreover, it was shown that the detection of hypoxemia by clinical criteria is extremely unreliable. Meanwhile, the use of PO has become part of the obligatory standard monitoring during GA in Germany and many other countries. Likewise, the use of PO is standard care in the PACU although there are no official recommendations. However, for the time period in between, i.e. immediately after GA during transportation of patients from the OR to the PACU, monitoring of the S(p)O(2) in patients breathing room air is neither obligatory in Germany nor are there any official recommendations or guidelines in this respect. Given the introduction of shorter acting anesthetic agents within the last 25 years, the main goal of this study was to explore whether the incidence of hypoxemia in the immediate period after GA is still so high. Additional aims of this study were to examine whether the detection of hypoxemia based on clinical criteria can be confirmed to be very unreliable, what the risk factors for hypoxemia following GA are and how common it is in Germany to transport patients from the OR to the PACU without PO and supplemental oxygen. METHODS In a prospective observational study 970 patients who underwent a broad spectrum of elective surgery under GA in a university hospital setting were included. The S(p)O(2) was measured at the end of the transfer from the OR to the PACU immediately after the anesthetist who had taken care of the patient during the operation had estimated the S(p)O(2). The association between biometric, surgical and anesthesiological variables on the one hand and hypoxemia as well as a decrease of S(p)O(2) on the other hand were studied using multivariate methods. Finally, a survey including all university hospitals was carried out to find out about the use of PO and oxygen during patient transfer from the OR to the PACU. RESULTS Of the 959 patients who were eligible for analysis 17% had a S(p)O(2) < 90% and 6.6% a S(p)O(2) < 85%. Hypoxemia was not recognized in 82% of the patients in whom an assessment based on clinical grounds was carried out. Variables with an independent influence on hypoxemia and decrease of S(p)O(2) were as follows: saturation before induction of GA, body mass index, age, American Society of Anesthesiologists (ASA) physical status, difference between maximum and minimum inspiratory pressure, mode of ventilation, the choice of opioid and muscle relaxant as well as the use of nitrous oxide. Patient-dependent risk factors had the strongest impact on hypoxemia. In about 80% of the university hospitals neither PO nor supplemental oxygen is used during transportation of the patient from the OR to the PACU. CONCLUSIONS The use of opioids and relaxants with short duration of action may have favorable effects on preventing hypoxemia and decreases of S(p)O(2). These measures will, however, not be sufficient to solve this problem because the highest risk factors for hypoxemia are patient-related. Despite knowing risk factors for oxygen desaturation, it is currently not possible to reliably predict which patients will become hypoxemic or have a decrease of S(p)O(2). Therefore, transportation of patients breathing room air from the OR to the PACU directly after GA without use of PO or supplemental oxygen seems to be questionable in terms of patient safety.