Does fresh gas flow rate affect monitoring requirements?

Opinions vary on the monitoring requirements associated with low flow to closed circuit anesthesia. Fresh gas flow rate affects variables of anesthesia ventilation such as the time constant of the breathing system, the inspired concentrations of O2, N2O and anesthetic vapor and the potential for rebreathing. Furthermore, very low flow rates challenge the performance of rotameters and vaporizers. Consequently, the safe conduct of minimal flow or closed circuit anesthesia mandates oximetry, which should be redundant; the use of anesthetic agent monitors ("anesthetico-meters") is extremely helpful, and so is capnometry. However, none of these safety monitors is beyond the scope of the "essential requirements" proposed for anesthesia workstations by international standard-writing groups, such as CEN or ISO. It may hence be concluded that fresh gas flow rate does affect variables to be monitored, but it does not affect essential monitoring requirements.     

The effect of muscle relaxants on masseter tone. An experimental study in an MH-susceptible swine model]

Malignant hyperthermia (MH) may occur, when a genetically predisposed individual or pig (MHS) is exposed to triggering agents. The increase in free, ionized sarcoplasmic calcium inducing the vicious circle of MH is believed to result from calcium-induced release with volatile anaesthetics, and from depolarization-induced calcium release with succinylcholine (SCH). The administration of SCH to susceptible humans or pigs frequently produces an increase in masticatory muscle tone. This hitherto ill-defined phenomenon is referred to as "masseter spasm" (MS). We have attempted to elucidate the pathophysiology of MS in a porcine model. METHODS. After the protocol had been approved by the state authorities, 6 MHS pigs were investigated. The pigs were mixed breeds (German Landrace and Dutch Pietrain) and were 9 +/- 1 weeks old with an average body weight of 25.5 kg. Premedication consisted of intramuscular injection of azaperone, 7.5 mg.kg-1. Anaesthesia was induced with piritramide, 1.2 mg.kg-1, administered via a cannulated ear vein. Subsequent to laryngoscopic endotracheal intubation, neuromuscular blockade was achieved with 4 mg pancuronium. Ventilation was set at 12 breaths per minute and adjusted to maintain an end-tidal CO2 concentration of 4.7% by adapting the tidal volume (PhysioFlex). Anaesthesia was maintained with piritramide, 2.25 mg.kg-1.h-1, pancuronium, 0.4 mg.kg-1.h-1, and N2O (60% in O2). Instrumentation included an arterial line, a central venous line, and a fiberoptic pulmonary artery catheter (Oximetrix). Masticatory muscle tone (MMT) was assessed with an intermolar balloon, connected to a pressure transducer and calibrated to zero prior to SCH administration. As a reference variable for effects produced by SCH, intraocular pressure (IOP) was measured manometrically in the anterior chamber. After stabilization of haemodynamic variables, the neuromuscular blockade was allowed to wear off. After recovery of the evoked masseter electromyogram, a paralyzing dose of pancuronium was administered (0.5 mg.kg-1). When paralysis was complete, SCH was administered (1.5 mg.kg-1), followed a few minutes later by dantrolene infusion (5 mg.kg-1 over 10 min). RESULTS. The administration of SCH was followed by clinically unequivocal MH episodes in all pigs, indicated by an increase in oxygen uptake (VO2; PhysioFlex; Fig. 1) and end-tidal CO2 concentration and a decrease in oxygen saturation of mixed venous blood (svO2; Fig. 2). Despite complete neuromuscular blockade (monitored with EMG), SCH produced an increase in MMT in all pigs which was reversed by dantrolene (Fig. 3). The time course of MMT paralleled that of IOP, suggesting a similar underlying mechanism. DISCUSSION. Succinylcholine is a trigger of MH in susceptible individuals; onset of the syndrome may be associated with "masseter spasm". SCH increases extraocular muscle tone, probably by means of stimulating multiply innervated fibers; the resulting IOP increase is not prevented by competitive neuromuscular blockade. The existence of multiple innervated fibers has also been shown in muscle spindles in the deep layers of the masseter, with their stimulation resulting in elevation of the jaw. We speculate that the increases in MMT and IOP observed in this study reflect the same process, i.e. a motor response, initiated by SCH-induced stimulation of the intramyocellular contractile system of multiply innervated muscle fibers, that is independent of neuromuscular transmission. Triggering of MH with SCH despite complete neuromuscular blockage suggests a mechanism other than depolarization-induced calcium increase. And, for the semantics, according to neurological terminology MS should be referred to as contracture not as spasm.     

A myoclonic seizure during propofol-alfentanil anesthesia?]

Total intravenous anaesthesia with propofol and alfentanil is an established alternative to inhalation anaesthesia for intracranial neurosurgical procedures. Its usefulness has been somewhat overshadowed by reports of seizure-like movements, both during anaesthesia and in the recovery period. These can be related to the use of either anaesthetic agent, but true epileptogenic properties still remain to be demonstrated in man. Opioid-induced rigidity is a well known phenomenon and must not be mistaken for an epileptic seizure. Myoclonic motor activity can be observed even under physiological conditions, e.g. sleep. Almost all anaesthetic agents have been found to produce "epileptic" EEG changes (spikes, polyspikes, spike-wave complexes), but in man these have never been correlated to motor reactions. Propofol's pro- or anticonvulsive action is unclear. While some groups found shortened convulsing times in patients undergoing electroconvulsive therapy with propofol instead of methohexitone, others have reported activation of epileptogenic foci in the EEGs of known epileptic patients. A synergistic effect of propofol and alfentanil in the generation of seizure-like movements cannot be excluded. Whether seizure-like movements indicate a true "epileptogenic potency" of the anaesthetic drugs or are related to other phenomena remains to be studied. Electro-encephalographic monitoring during anaesthesia as well as careful observation and documentation of motor reactions may contribute to elucidation of the problem. We report a case of seizure-like movements during propofol-alfentanil anaesthesia for an elective craniotomy. A 52-year-old patient presented with a history of headaches of increasing frequency. A CT brain scan demonstrated a tumor in the left occipital region.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rectal administration of drugs. Fundamentals and applications in anesthesia]

Rectal administration of drugs has become a standard procedure in clinical anesthesia, most notably for anorectal induction in children. Limitations of this method include low bioavailability, a wide scatter of pharmacokinetic and pharmacological results, and poor predictability of the clinical effect in any particular patient. Historically, the rectal route has been used for the administration of smoke ("fumigation") for resuscitation and various other purposes. An ether boiler for rectal application was developed by Pirogoff as early as 1847. The pharmacokinetics of rectally administered drugs are determined by the anatomical properties of the rectum and, owing to interindividual variance, this adds to the inconsistency of absorption. Aspects that can be better controlled include the drug preparation and the vehicle, with hydrophilic solutions resulting in improved absorption. Larger volumes such as are associated with lower concentrations increase the bioavailability by enlarging the mucosal surface in contact with the drug. In contrast to the hypothetical assumption that hepatic circulation may be circumvented--thus avoiding first-pass metabolism--by direct venous drainage from the rectum into the systemic circulation via the vena cava, it has been shown that hepatic clearance is the main factor affecting bioavailability. This may be due to blood flow through anastomoses interconnecting the superior, medium and inferior rectal venous systems. Resorption from the rectum is also determined by physicochemical properties of drugs. According to the pH-partition hypothesis, only the non-ionized moiety of a compound will be available for transmucosal diffusion. The degree of ionization is a function of the local (or microclimate) milieu pH and pKa of the drug; the former is close to neutral in adults but alkaline in most children. Adsorption of feces, intraluminal degradation by microorganisms, metabolism within the mucosal cell, and lymphatic drainage do not significantly affect the fate of rectally administered drugs. In clinical practice, the rectal administration of methohexital and midazolam is an established method of premedication or induction of anesthesia in children; so far, midazolam appears to be associated with fewer complications. Ketamine has been shown to be as effective and as quick-acting as methohexital, but at least in one study its use as sole induction agent was associated with respiratory distress in some cases. However, painful diagnostic or therapeutic procedures in children may be indications for the rectal administration of ketamine. Early trials with rectally administered etomidate have been abandoned since its implication in suppression of cortisol synthesis. Narcotic analgesics in a hydrogel vehicle are effective in adult pain management.(ABSTRACT TRUNCATED AT 400 WORDS)     

CT-Cephalometry—A study in Indian population

Determination of obstructive site in obstructive sleep apnoea (OSA) is of paramount importance is planning the management. Cephalometric evaluation of lateral X-rays when combined with clinical assessment and fibreoptic examination of the airway helps in locating the site of obstruction. The usual technique of cephalometry has been modified so as to give a better delineation of the soft tissues. Holding a 2mm card board in the mouth and using barium paste helped in more accurate calculations. Using our technique, various parameters have been quantified and a number of controls were studied and normal range derived. Further improvement in cephalometry has been done by using C.T. cephlometry topogram technique. A topogram is a scan done on a running table top cranio-caudally. Using the topogram technique 38 OSA patients were evaluated for all the parameters. The technique, its advantages over traditional cephalometry and the values obtained in the study are discussed in this paper.     

Temporal trends in hip fracture incidence,mortality, and morbidity in Denmark from 1999 to 2012

Background and purpose — While development in hip fracture incidence and mortality is well examined, none has yet looked at the temporal trends regarding prevalence of co-morbidities. Therefore we investigated changes in incidence of first hip fracture, co-morbidity prevalence, 30?day- and 1-year mortality in hip fracture patients in the Danish population during the period 1999 to 2012.

Patients and methods — Patients >18 years admitted with a fractured hip in Denmark between 1996 and 2012 were identified with data for the period 1999–2012 being analyzed regarding prevalence of co-morbidities, incidence, and mortality.

Results — 122,923 patients were identified. Incidence in the whole population declined but sex-specific analysis showed no changes for men. For the whole study population, 30-day and 1-year mortality remained unchanged. Age at time of first hip fracture also remained unchanged. Of the included co-morbidities a decrease in prevalence of malignancy and dementia in women was found while there was an increase in the prevalence of all remaining co-morbidities, except hemi- or paraplegia for both sexes, rheumatic diseases for women, and for men diabetes with complications, myocardial infarction, AIDS/HIV, and malignancy.

Interpretation — While hip fracture incidence declined for women it was unchanged for men; likewise, 30-day and 1-year mortality rates together with age at first fracture remained unchanged. When these results are compared with the relatively large increase in the prevalence of co-morbidities, it does not seem likely that the increased disease burden is affecting either the incidence or the mortality.     

Correlation between serum lipoprotein (a) and angiographic coronary artery disease in non-insulin-dependent diabetes mellitus

Abstract. Comlekqi A, Biberoglu S, Kozan 0, Bahqeci 0, Ergene 0, Nazli C, Kinay 0, Guner G (Dokuz Eylul University, Medical School, Inciralti, Izmir, Turkey). Correlation between serum lipoprotein(a) and angio-graphic coronary artery disease in non-insulin-dependent diabetes mellitus. J Intern Med 1997; 242:449-54.
Objectives: To examine the impact of diabetic state on the concentrations of lipoprotein(a) [Lp(a)] in patients with non-insulin-dependent diabetes mellitus (NIDDM) and the correlation between angiographic coronary artery disease (CAD) and serum Lp(a) concentrations in NIDDM.
Design: In this cross-sectional study of 26 patients with NIDDM and 19 nondiabetic sex- and agematched patients who underwent coronary angiography, CAD was assessed visually using coronary artery score (CAS), and plasma Lp(a) was measured by an enzyme-linked immunosorbent assay.
Setting: The study was performed in an internal medicine clinic at a university hospital.
Subjects: Twenty-six age- and sex-matched patients with NIDDM and 19 control patients without diabetes.
Results: There was no significant difference between the Lp(a) concentrations of patientswith NIDDM and nondiabetic subjects (P > 0.05). When patients with NIDDM were stratified by absence or presence of CAD, patients with CAD had higher levels of Lp(a) (P < 0.05). However, there was no significant correlation between the concentrations of Lp(a) and CAS (P > 0.05).
Conclusions: Diabetic state does not have any impact on Lp(a) concentrations. Lp(a) excess seems to be atherogenic in patients with NIDDM as shown in nondiabetic patients in previous studies. Although diabetic patients with CAD have higher Lp(a) concentrations than the diabetic patients without CAD, Lp(a) levels were not correlated with CAS.     

Characterization of non-human primate antisera to acute lymphoblastic leukemia (ALL): evidence for unique antigen(s) on childhood ALL of "T" phenotype

A non-human primate antiserum was prepared to acute lymphoblastic leukemia of T-cell phenotype (T-ALL) and, after absorptions with normal blood elements, reacted by immunofluorescence and microcytotoxicity to all the T-ALL tested. In addition, the antiserum reacted with cells from about 70% of the common ALL studied and immunoprecipitated the common ALL antigen of 100,000 daltons. However, when the anti-T-ALL serum was absorbed with with lymphoblasts from common ALL, it failed to react with common ALL lymphoblasts, yet reacted significantly with cells from patients with T-ALL phenotype and defined a 100,000-dalton membrane component not found on common ALL lymphoblasts. In addition, sequential immunoprecipitation of 125I-labeled T-ALL membranes by anti- common-ALL serum followed by anti-T-ALL serum detected the T-ALL membrane component of 100,000 daltons that was not found on common ALL. Thus, our results demonstrate the presence of of a unique human T-ALL antigen present on all T-ALL distinct from the common ALL antigen.