Arterial and transcutaneous oxygen tension measurement during hypotensive anaesthesia.

The values of oxygen tension (PO2) as measured by transcutaneous (at two different sites) and invasive methods were compared during hypotensive anaesthesia with sodium nitroprusside (SNP) in 15 patients. Generally the PO2 significantly decreased during and increased after SNP-induced hypotensive anaesthesia (p less than 0.001). A positive correlation was found between the ratios of change of invasive arterial oxygen tension (PaO2) and supraclavicular transcutaneous oxygen tension (tcPO2) both during (r = 0.64) and after (r = 0.83) hypotension. A similar correlation existed between the ratios of change of PaO2 and forearm tcPO2 only after (r = 0.66) but not during (r =0.33) hypotensive anaesthesia. It is concluded that any of the above methods can be used to give an assessment of PO2 changes during SNP-induced hypotension provided the prehypotensive value is measured. For quantitative measurement of PO2 the invasive method is the first choice. Supraclavicular tcPO2, however, can give an accurate result, while the forearm tcPO2 is the least sensitive.

The effects of oral diazepam premedication on blood gases.

Blood gas analysis was performed before and 1 h after 10 mg oral diazepam premedication on 50 adult male patients undergoing different surgical operations. There was a significant (p less than 0.01) decrease in arterial oxygen tension, a significant (p less than 0.01) increase in alveolar--arterial oxygen tension difference, and no significant change in arterial carbon dioxide tension or pH after administration of the drug. It is concluded that diazepam given by mouth 1 h before operation increases venous admixture. It is suggested therefore that oral diazepam premedication should be given cautiously to patients with impaired cardiorespiratory reserve, preferably without adding a narcotic drug.

Foreign bodies in the respiratory tract. A review of forty-one cases.

The nature of inhaled foreign bodies in the respiratory tract and problems in their removal are reviewed with reference to experience in a series of 41 cases, 36 of them in children under 4 years old. Bronchoscopic removal under general anaesthesia is preferred to inhalational therapy and postural drainage.

Hygienic practices of consultant anaesthetists: a survey in the north-west region of the UK.

Questionnaires were distributed to all 213 consultant anaesthetists in the North-West region of the UK with a response rate of 68%. These questionnaires were designed to assess the hygienic precautions taken to reduce the potential for transmission of infectious agents to and from the patients under their care. Face masks and gloves were always used by 35.2% and 14.5%, respectively, while only 36.4% washed their hands between cases. Most respondents have changed their practice since the recognition of HIV transmission (74.8%) and hepatitis B and C (69.8%). A high proportion of anaesthetists continue to administer anaesthesia despite suffering from respiratory (94%), gastrointestinal (42.9%) or herpes simplex (32.6%) infections. The anaesthetic breathing system was changed at the end of each day or following a high-risk case by 33.3% of the respondents, while just over 25% changed it following a known infected case. Bacterial filters were used by 17% and changed after each case by 7.2%. On a scale of 0-10 (10 = significant) anaesthetists rated their potential for transmitting or contributing to patient infection as a median of 3 (interquartile range: 2-6). The results of this study show that, although anaesthetists are well aware of proper hygienic practices, their performance falls short of accepted recommendations.

Pulmonary function and head lift during spontaneous recovery from pipecuronium neuromuscular block.

We have studied in seven healthy conscious volunteers the correlation between the electromyographic (EMG) and clinical criteria used to identify adequate recovery from sub-paralysing doses of pipecuronium. Pipecuronium (mean dose 1.88 (range 0.92-3.16) mg) was administered to reach a T4/T1 ratio of 0.5; full recovery to 1.0 was produced in a mean time of 25.3 (14-39) min. During recovery from neuromuscular block, we measured tidal volume, forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) negative inspiratory pressure (NIP), peak expiratory flow rate (PEFR), mid-expiratory flow rate (MEFR) and 5-s head lift. The assessments were started when the train-of-four (TOF) ratio reached 0.5 +/- 0.001 and repeated at each 0.1 +/- 0.001 increase up to a ratio of 1.0. All volunteers showed ptosis and diplopia after the first dose and difficulty in swallowing with subsequent doses. They also experienced a pleasant, relaxing sedative sensation. All could sustain head lift for 5 s at a TOF ratio of 0.5 and higher, except for one subject who could not lift his head only at a ratio of 0.5. There was a statistically significant decrease in FVC, FEV1 and PEFR with a nonsignificant decrease in other pulmonary measurements, except for NIP which only decreased significantly at a ratio of 0.5. These changes are probably of no clinical importance. All the measured respiratory variables returned to control values at a TOF ratio of 0.9.

Gastric regurgitation during general anaesthesia in different positions with the laryngeal mask airway.

Ninety patients, divided into three groups of 30, were investigated to determine the incidence of gastric regurgitation during general anaesthesia administered via the laryngeal mask airway in the supine, Trendelenburg and lithotomy positions. Fifteen minutes before induction of anaesthesia each patient swallowed a 75 mg methylene blue capsule. At the end of surgery, the LMA and the oropharynx were inspected for bluish discoloration which was considered to be a sign of gastric regurgitation. No blue dye was detected in the supine group but it was observed in one patient in each of the other two groups.