Failed tracheal intubation in obstetrics: a 6-year review in a UK region

In the South Thames (West) region of the United Kingdom, during a 6-year period from 1993 to 1998, there was a significant increase in the Caesarean section rate accompanied by a significant decrease in the use of general anaesthesia for operative delivery. During this time, there were 36 failed tracheal intubations occurring in 8970 obstetric general anaesthetics (incidence 1/249). There was no significant difference in the incidence of failed tracheal intubation in each of the six years. In 24 of the 26 cases for which the patients' notes could be examined, there was either no recording of preoperative assessment, a failure to follow an accepted protocol for failed tracheal intubation, or no follow-up.     

Prediction of the oculocardiac reflex from pre-operative linear and nonlinear heart rate dynamics in children

This study was aimed to determine whether pre-operatively measured linear and nonlinear analysis of heart rate variability might predict the occurrence of the oculocardiac reflex (OCR) or other arrhythmia during strabismus surgery in children (n = 185, mean (SD) age = 8.09 (3.31) years). We compared time- and frequency-domain, and nonlinear dynamic indices of pre-operatively measured RR interval data between the OCR-positive group (maximum heart rate decrement = 20 beat.min-1 during the traction of extraocular muscle, n = 54), OCR-negative group (< 20 beat x min(-1), n = 78) and arrhythmia-positive group (all other arrhythmias; n = 53). pNN50, rMSSD, high-frequency power and nonlinear prediction error were significantly lower in the OCR-positive and arrhythmia-positive groups than in the OCR-negative group. Discriminant analysis using these indices could correctly identify 39/54 (72.2%) OCR-positive patients. Some pre-operatively measured indices of linear and nonlinear heart rate variability, especially when used in combination, are valuable for predicting significant bradycardia during strabismus surgery in children.     

Penetration Enhancers and Other Factors Governing Percutaneous Local Anaesthesia with Lidocaine

Abstract The percutaneous penetration of the local anaestetic lidocaine was investigated in the guinea-pig. Three different types of composition were employed: lidocaine hydrochloride in aqueous solution, lidocaine base in an aqueous alcoholic solvent mixture and lidocaine base in aqueous solutions of dipolar aprotic solvents. The latter solvents included simple tertiary aliphatic amides, amides related to dimethylacetamide, some cyclic amides as well as a number of miscellaneous compounds. The degree of dermal anaesthesia was noted in each case. In addition, the uptake and distribution of lidocaine in the skin and its absorption into the blood were studied using tritium-labelled drug. The results show that the percutaneous penetration of lidocaine is dependent on the concentration of the agent, the time of epicutaneous application of the composition, whether the agent was used as salt or free base, and the nature of the solvent medium. Lidocaine base in aqueous dimethylacetamide was most effective in producing percutaneous local anaesthesia.     

Controlled Hypotension with Sodium Nitroprusside: Effects on Cerebral Blood Flow and Cerebral Venous Blood Gases in Patients Operated for Cerebral Aneurysms

The effect on cerebral haemodynamics of arterial hypotension induced by sodium nitroprusside infusion was studied in nine patients at the end of operations for intracranial aneurysms under N2O-O2-halothane anaesthesia. Cerebral blood flow (CBF), using the intraarterial 133Xe injection method, and cerebral jugular venous blood gases were monitored before, during and after the induced hypotension. CBF and jugular venous oxygen tension (PvO2) remained constant during the hypotensive period. Following its termination, a 13% increase in CBF occurred (P less than 0.05) and PvO2 showed the same trend, a 5% increase (P less than 0.30). Regional CBF recordings (rCBF) in 16 small areas within the cerebral hemisphere were obtained at each measurement. In four of the patients, rCBF abnormalities were present in the form of hyperaemic regions, probably induced by the operation or the disease itself. The focal abnormalities were not accentuated during hypotension nor were ischaemic regions disclosed. It is concluded that sodium nitroprusside has only a minor influence on cerebral haemodynamics in the anaesthetized state.     

Subdural Haematoma. A Rare But Life-Threatening Complication after Spinal Anaesthesia

A 70-year-old patient developed severe headache after spinal anaesthesia. He was treated with an epidural autologous blood patch with only temporary relief. Three weeks after the spinal anaesthesia, the headache became more intense and was accompanied by nausea and vomiting. A second epidural blood patch was performed without effect. The patient became unconscious and an acute CT scan revealed a large subdural haematoma. This was immediately evacuated and the patient made a good recovery. This case demonstrates that subdural haematoma should be considered as a possible aetiology in severe postspinal headache.     

Alveolar Stability during Anaesthesia for Reconstructive Vascular Surgery in the Leg

Alveolar stability was studied during prolonged enflurane anaesthesia by using a multiple inert-gas elimination technique for the assessment of the "continuous" distribution of ventilation-perfusion ratios (_A/). All 10 patients (mean age: 61 years, six smokers) presented with increased _A/ mismatching during anaesthesia, with a redistribution of lung blood flow to regions with low or high _A/. Five patients had perfusion of units with _A/≤0.07 which may cause unstable alveoli with the presently used inspiratory gas mixture. However, only two patients displayed increasing shunting suggestive of alveolar collapse during the 3.5 h observation period. This lower than expected incidence may indicate protective mechanisms against atelectasis, such as mechanical interdependence between lung units, or collateral ventilation.     

Haemodynamic Effects of Calcium Chloride Administered Intravenously to Patients with and without Cardiac Disease during Neurolept Anaesthesia

During neurolept anaesthesia, calcium chloride (15 mg/kg) was administered intravenously to two different groups of patients undergoing vascular surgery on the abdominal aorta. The patients in group I all suffered from cardiac disease and were treated with digoxin, while the patients in group II had no cardiac symptoms. Cardiovascular measurements were made during steady-state anaesthesia. In group I, CaCl₂ increased cardiac index (CI) significantly while systemic vascular resistance index (SVRI) remained unchanged. Mean arterial pressure (MAP) increased. In group II, both MAP and SVRI increased while CI remained unchanged. No significant changes in heart rate were observed and no arrhythmias occurred. It is concluded that CaCl₂ administered intravenously is an effective means of improving cardiac function when it is depressed by anaesthesia, underlying cardiac disease, or both.     

Influence of Two Different Anaesthetic Agents on the Newborn and the Correlation between Foetal Oxygenation and Induction-Delivery Time in Elective Caesarean Section

The PO2 and acid-base balance (pH, PCO2 and base deficit) of the newborn, determined at the moment of birth and at 10 and 60 min after birth, were compared in two series of elective caesarean section, anaesthesia being induced with thiopentone in one series (n = 12), and with ketamine in the other (n = 16). The PO2 and acid base values of umbilical cord blood at birth were correlated with the induction delivery (ID) times of the total series of patients subjected to elective caesarean section (n = 28). The ID-times were varied between 2 and 10 min. The PO2, acid-base values and Apgar scores did not differ between the thiopentone and ketamine groups. A significant negative correlation between the PO2 of the newborn at the moment of birth and the ID-time was found in the thiopentone group. The study suggests that ketamine is a good alternative to barbiturate as an induction agent for caesarean section.