Viewpoint: survival benefit by selective decontamination of the digestive tract (SDD)

Morbidity and mortality due to infection acquired either before or after admission to the intensive care unit is still a major problem. A limited range of potentially pathogenic microorganisms (PPM) are involved, and infection with these PPM usually follows a predictable pattern. Selective decontamination of the digestive tract (SDD) should be investigated further in patients with primarily curable diseases who are not infected on admission to intensive care but become infected there.

Use of liposuction and saline washout for the treatment of extensive subcutaneous extravasation of corrosive drugs

We report a case of extensive subcutaneous extravasation of corrosive drugs used during cardiac resuscitation, in a neonate undergoing cardiac catheterization. Early management with hyaluronic acid, liposuction and saline washout of the extravasated fluid prevented development of any tissue damage. This simple technique was easy to use and extremely effective.

Modification of the iso-shunt lines for low inspired oxygen concentrations

Arterial PO2 (PaO2) has been related to inspired oxygen concentration (FIO2 range 0.21-0.60) in 20 patients, breathing spontaneously, while recovering from a range of conditions treated in an intensive therapy unit. There was a highly significant linear trend (P < 0.001) for the mean venous admixture ("virtual shunt"), calculated from the iso-shunt diagram (model A), to increase from 0.11 to 0.19 as FIO2 decreased from 0.60 to 0.21. As this appeared to be caused by relative ventilation/perfusion (V/Q) mismatch, we prepared a second model (model B) with a variable two-compartment relative V/Q mismatch in addition to a shunt. Regression of the degree of mismatch on the shunt gave good agreement between predicted and observed PaO2 values (mean bias -0.17 kPa, pooled within patient SD 1.22). Model B is now proposed to extend the applicability of the iso-shunt diagram for FIO2 values less than 0.35. Published postoperative PaO2 data from other workers showed good agreement with our final model (mean bias 0.10 kPa, pooled SD 0.41). The new diagram may therefore have wide applicability in the field of anaesthesia and intensive care.

A simple method for monitoring the concentration of inhaled nitric oxide

Nitric oxide is a potent endogenous vasodilator involved in the homeostatic control of systemic blood pressure. It has also recently been demonstrated that when inhaled in low concentrations it acts as a specific pulmonary vasodilator. The concept of inhaled nitric oxide as a form of therapy is almost an anathema to anaesthetists. However, nitric oxide is being used increasingly for the treatment of persistent pulmonary hypertension of the neonate and in the adult respiratory distress syndrome. One major limitation to its frequent and widespread use is the problem of measuring the concentration of nitric oxide delivered. Currently, the gold standard technique used is chemiluminesence. However, the equipment required is costly and can be difficult to use. If the use of inhaled nitric oxide increases and it develops a therapeutic role then its applications may be limited only to centres which can afford such equipment. Others may be prevented from using a potentially valuable therapy due to lack of a controlled delivery system for nitric oxide. An inexpensive, simple alternative technique to chemiluminesence is described, which will allow most intensive care units the freedom to use inhaled nitric oxide if necessary.

The Bicore pulmonary monitor. A device to assess the work of breathing while weaning from mechanical ventilation

The Bicore CP-100 pulmonary monitor offers the advantage of continuous pulmonary monitoring at the bedside. Using an easily placed oesophageal balloon catheter and a flow transducer within the ventilator system, intrathoracic pressures, airway pressures and airway flow can be measured, and from these the Bicore calculates 25 other respiratory variables. The monitor screen displays real time waveforms of airway pressure, airway flow, oesophageal pressure and inspired tidal volume, and with these data it should be possible to determine more accurately when patients can be weaned from mechanical ventilation. It should also be possible to assess objectively the onset of respiratory fatigue and failure so that intervention can take place at an earlier stage. To assess the ease of use and potential benefit, the Bicore was used to calculate the work of breathing while weaning eight patients from mechanical ventilation in a spontaneous breathing mode. The pressure support ranged from 20 cmH2O, 10 cmH2O and 5 cmH2O, to a continuous positive airway pressure of 5 cmH2O, all with a positive end-expiratory pressure of 5 cmH2O, down to a single T-circuit with no positive airway pressure or end-expiratory pressure. The work of breathing while on a Veola Hamilton ventilator was found to be about the same, while receiving pressure support of 20 cmH2O compared to a continuous positive airway pressure of 5; the other forms of respiratory support increased the work of breathing significantly.

Propofol stimulates nitric oxide release from cultured porcine aortic endothelial cells

Propofol, an intravenous anaesthetic agent, causes marked vasodilatation in vivo. In the present study the effects of propofol on the release of nitric oxide (NO) from vascular endothelial cells was determined in vitro. Application of propofol to co-cultures of porcine aortic endothelial and smooth muscle cells resulted in a rapid increase in cyclic GMP formation. This increase was significantly inhibited following pretreatment of the cells with either NG-nitro-L-arginine (L-NOARG) or in the presence of haemoglobin. When applied to smooth muscle cells alone, propofol did not result in an increase in cyclic GMP levels. These results demonstrate that propofol stimulates the production and release of NO from cultured endothelial cells and suggest that the vasodilatation and hypotension observed when propofol is given in vivo may be due to NO release.

Continuous spinal anesthesia: dose requirements and characteristics of the block

BACKGROUND AND OBJECTIVES

A fine-bore 28G CoSpan spinal catheter was used to provide continuous spinal anesthesia for major upper and lower abdominal, peripheral vascular, and orthopedic surgery in 90 patients, aged 31-91 years.

METHODS

Initial doses (0.5-2.0 mL) of hyperbaric bupivacaine 0.5% were given and followed, if needed, by additional doses of 0.5-1.0 mL to achieve a satisfactory blockade for the proposed type of surgery. The incidence of hypotension, ambulatory postdural puncture headache, and technical problems encountered with insertion of the spinal catheters were recorded.

RESULTS

The technique of continuous spinal anesthesia was successful and easy to learn. Satisfactory sensory and motor blockade was achieved within 12-18 minutes, and surprisingly small amounts were needed in those patients undergoing limb surgery.

CONCLUSIONS

Mild postdural puncture headache occurred in four patients, but none of the patients required blood patch. One catheter broke during removal; since then, it has been our policy to remove a catheter with the patient in a flexed position.

Torsade de pointes and long QT syndrome following major blood transfusion

We report a rare complication following transfusion of a large volume of blood in an adult patient. An electrophysiological disturbance of the cardiac cycle with prolongation of the QT interval developed, which was followed by recurrent episodes of torsade de pointes, a unique form of ventricular tachycardia. The most likely cause of this acquired long QT syndrome was hypomagnesaemia secondary to massive blood transfusion. Treatment with a magnesium infusion restored the QT interval to normal and temporary ventricular pacing prevented further ventricular arrhythmias.

Low-flow anaesthesia. Practice, cost implications and acceptability

An 8-week survey was conducted to determine whether the introduction of low-flow anaesthesia (a fresh gas flow of 4 litres/minute or less) into routine use would be acceptable to members of a representative anaesthetic department and if the consequent reduction in use of volatile anaesthetics would result in financial savings. The hourly consumption of the volatile agents was measured during anaesthesia conducted using either conventional or low fresh gas flows. Anaesthetists' acceptance of low-flow anaesthesia was assessed using a questionnaire. Data were gathered on 286 patients undergoing inhalational anaesthesia for routine operative procedures. A 54.7% reduction in the consumption of isoflurane and a 55.9% reduction in that of enflurane was found. Of the 28 anaesthetists at the hospital, 21 would use low-flow anaesthesia routinely. The routine use of low-flow anaesthesia would therefore be acceptable and could result in annual savings of 26,870 pounds at Northwick Park Hospital.

Rib cage contribution to resting and carbon dioxide stimulated ventilation during 1 MAC isoflurane anaesthesia

Using respiratory inductive plethysmography, we have measured rib cage and abdominal motion during isoflurane anaesthesia in 16 healthy day-surgery patients. Anaesthesia was induced with propofol and maintained with 1 MAC isoflurane in air-oxygen via a laryngeal mask. Measurements were taken during both resting ventilation and hyperpnoea induced by rebreathing carbon dioxide. For resting ventilation, the rib cage contributed a mean (SD) of 33 (15)% of the total ventilation whilst awake, and 39 (12)% during anaesthesia (ns). With increasing end-tidal carbon dioxide whilst awake, the subjects showed a mean increase in the percentage rib cage contribution of 7.1 (12.5)%/kPa of carbon dioxide. With isoflurane anaesthesia, there was significant depression of this rib cage recruitment with the mean contribution decreasing by 3.6 (7.4)% kPa-1 (P less than 0.05). These results indicate that 1 MAC of isoflurane does not selectively depress rib cage motion, except during carbon dioxide stimulated hyperpnoea.

Oral ketamine. Its use for mentally retarded adults requiring day care dental treatment

Four cases of severely mentally handicapped young adults requiring day care dental treatment are reported. All had required varying degrees of restraint during previous dental treatments, which had been distressing for the patient, the relatives and the ward staff. In all cases, administration of oral ketamine 10 mg/kg, 30-60 minutes before the procedure, facilitated subsequent induction of anaesthesia.