Point-of-care testing apparatus. Measurement of coagulation.

Point-of-care testing of coagulation parameters provides a more rapid assessment of test results compared with laboratory testing. A new coagulation monitor (GEM PCL, Instrumentation Laboratory, Kirchheim, Germany) was evaluated. Point-of-care data for activated partial thromboplastin time and prothrombin time (expressed as the international normalised ratio) and turn-around-time were compared. Coagulation parameters were compared in the blood of 57 patients with and without heparin therapy. The point-of-care and laboratory test results showed a bias (SD) of -0.26 (4.55) s for activated partial thromboplastin time and -0.011 (0.150) s for prothrombin time. The average turn-around-time was 3 min for point-of-care testing vs. 52 min for laboratory testing. We conclude that the reliability of point-of-care testing is sufficient for clinical use.

Preoxygenation: a comparison of three different breathing systems.

An end-tidal expiratory oxygen concentration (FE'O2) greater than 0.90 is considered to be adequate for preoxygenation. This is generally achieved using a face mask, but this can be unsatisfactory in some patients. We compared preoxygenation in 30 healthy volunteers using a face mask, the NasOral system, which is a novel preoxygenation device, and a mouthpiece with a nose-clip. We measured the maximal FE'O2, the FE'O2 after 2 min and the time to reach maximal FE'O2 and recorded the subjective judgement of the volunteers. The maximal FE'O2 with face mask and mouthpiece was significantly greater than with the modified NasOral system (P<0.05 and P<0.01). With the former devices, a FE'O2 of 0.90 was achieved in 73% of the volunteers vs 46% with the modified NasOral system. Using the mouthpiece, the FE'O2 after 2 min was significantly higher than using the face mask (P<0.01) or the modified NasOral system (P<0.01). The time to maximal FE'O2 was significantly shorter using the modified NasOral system than with the face mask or mouthpiece (P<0.001 and P=0.0001). The volunteers gave more positive ratings to the face mask and mouthpiece than to the modified NasOral system (P<0.001 and P<0.01). We conclude that the use of a mouthpiece can improve preoxygenation in some patients. The results obtained with the modified NasOral system do not justify its introduction into clinical practice.

Hearing loss after spinal and general anesthesia: A comparative study.

Hearing loss has been described after spinal anesthesia. We examined the hearing in patients before and after spinal and general anesthesia by pure tone audiometry (LdB: 125-1500 Hz; HdB: 2000-8000 Hz). Tympanic membrane displacement analysis was used to noninvasively monitor the intralabyrinthine and intracranial pressure. Eighteen patients received spinal anesthesia (G(SA)); 19 patients general anesthesia (G(GA)). Pure tone audiometry and TMD data were obtained preoperatively ((0)) and postoperatively on day 1 ((1)) and 2 ((2)). The mean threshold differences (Delta) in LdB(10) and LdB(20) were significantly different in G(SA) compared with G(GA) (DeltaLdB(10) + 0.15+/-3.07 dB vs. -1.34+/-3.77 dB, P = 0.05; DeltaLdB(20) -0.54+/-2.24 dB vs. -2.45+/-3.39 dB, P<0.01). However, there were no differences in DeltaHdB(10) between G(SA) and G(GA), but in DeltaHdB(20) (-1.40+/-3.95 dB vs -5.12+/- 6.35 dB, P = <0.01). We found a significant correlation between the magnitude of intraoperative intravascular volume replacement and low-frequency hearing loss. Tympanic membrane displacement values were not different pre- and postoperatively. Hearing was impaired after spinal and general anesthesia. Low-frequency hearing loss was correlated with intraoperative volume replacement. Tympanic membrane recordings did not reveal significant changes.

[Intraoperative transesophageal versus preoperative transthoracic contrast echocardiography. A method for detection of patent foramen ovale in neurosurgical patients]. / Intraoperative transösophageale versus präoperative transthorakale Kontrast-Echokardiographie. Eine Methode zum Nachweis eines funktionell offenen Foramen ovale bei neurochirurgischen Patienten.

Preoperative detection of a patent foramen ovale (PFO) may be achieved employing either transthoracic echocardiography (TTE) with the Valsalva manoeuvre in the awake patient or trans-oesophageal echocardiography (TEE) in the anaesthesised patient. Our study was undertaken to validate these methods with regard to their efficacy in identifying patients at risk for paradoxical air embolism (PAE). METHODS. In 67 patients ranging from 28 to 70 years of age, TTE was performed utilising the Valsalva manoeuvre prior to surgery. The patients were informed about all procedures and agreed to take part in the study. After induction of anaesthesia the patients were evaluated with TEE in the supine and sitting positions. At end-inspiration 10 ml agitated gelatine solution (Gelafundin) was injected through a central venous catheter into the right atrium after airway pressure of 20 cm H2O had been maintained for 5 s. The injected bolus was observed throughout the ventilatory cycle, with special attention being given to early expiration and systole. A right-to-left shunt was assumed if five echo targets were observed in the left atrium. RESULTS. The prevalence of PFO detected by TTE/Valsalva was 9%. The diagnosis was confirmed by TEE in 2 patients in the supine and 1 in the sitting position. An echocardiogram in these patients showed bulging of the septum to the left, which was not seen in those patients in whom PFO was detected only by TTE. DISCUSSION. The reason for the lower incidence of PFO detected by TEE during airway pressure 20 cm H2O may have been an insufficient increase of pressure in the right atrium with a negative right-to-left atrial pressure gradient. A standardised ventilation manoeuvre with supra-atmospheric airway pressure of 20 cm H2O is not sufficient. Bulging of the intra-atrial septum from right to left during airway pressure is a possible indication of the efficacy of the manoeuvre, regardless of the influence of the breathing pattern.

Venous and paradoxical air embolism in the sitting position. A prospective study with transoesophageal echocardiography.

This prospective study investigates the frequency of patent foramen ovale (PFO), venous air embolism (VAE) and paradoxical air embolism (PAE) by transoesophageal echocardiography (TOE) in neurosurgical patients operated on in the sitting position. The risk of PAE after exclusion of PFO is assessed. A PFO was identified by pre-operative TOE and VAE and PAE by continuous intraoperative TOE. Sixty-two patients were divided into two groups, 22 patients were studied in group 1 (posterior fossa surgery) and group 2 (cervical surgery) contained 40 patients. Pre-operative TOE demonstrated a PFO in 5 of the 22 patients in group 1 (23%). Patients with proven PFO were excluded from the sitting position. Two further patients of this group (12% of 17 patients), in whom a PFO had been excluded pre-operatively, nevertheless had PAE, air occurring in all cavities of the heart. In group 2 the incidence of PFO was 4 out of 40 patients (10%). No PAE was observed in this group. Three morphological types of VAE with different haemodynamic and ventilation changes were demonstrated. VAE was observed in 76% of all posterior fossa operations and in 25% of cervical laminectomies. We conclude that a pre-operative search for PFO is mandatory considering its incidence of 23% in group 1 and of 10% in group 2, and the risk of PAE. If a PFO is detected, the sitting position should be avoided. A residual risk for PAE remains despite exclusion of PFO because the reliability of TOE is limited. TOE is the method of choice for detecting VAE and PAE.

[Postoperative air embolism caused by pneumatocephalus following occlusion of the posterior fossa. A rare complication indicative of a bridging vein disruption]. / Postoperative Luftembolie durch Pneumatozephalus nach Verschluss der hinteren Schädelgrube. Eine seltene Komplikation als Hinweis auf einen Brückenvenenabriss.

Many neurosurgeons prefer the sitting position for patients undergoing surgery in the posterior fossa because of the easier access and better conditions for haemostasis. Pneumatocephalus is a possible consequence of surgery in the posterior fossa with the patient in the sitting position. When this occurs air may enter the subarachnoid space, the cisternae, the ventricular system or the subdural space; it becomes more likely when any of the following is/are present: loss of CSF, a large cavity resulting from surgery, external or internal drainage of CSF, osmotic diuresis, and hyperventilation. Distances of 1-2 cm between cranium and brain may be found. The rupture of bridging veins may cause a subsequent subdural haematoma. Air embolism due to pneumatocephalus via the same vein after closure of the cranium is in this paper for the first time. Case report. A 37-year-old man with known Hippel-Lindau disease presented for posterior fossa surgery for treatment of a haemangioblastoma of the right cerebellar hemisphere. Surgery was done with the patient in a sitting position. Apart from one short episode of air embolism without haemodynamic changes no intraoperative complications occurred. After closure of the cranium and galea an unexpected and inexplicable air embolism of 10 min duration occurred again. TEE demonstrated the air looking like a string of beads in the right atrium. As complete skin had already been closure no explanation for the air embolism could be found. The patient was positioned supine, and air was no longer detectable in the right heart after 1 min. Approximately 1 h later both pupils were dilated and unreactive to light.(ABSTRACT TRUNCATED AT 250 WORDS)