Evaluation of the Effects of Two Types of Fluid in the Recovery From Anaesthesia.

Treatment of postoperative nausea and vomiting (PONV) is extremely important for patient comfort and satisfaction after surgery.1 There has been a recent change in emphasis from inpatient to day care surgery and anaesthesia with attendant increased interest in the problem of PONV. The incidence of PONV following day case gynaecologic surgery is 40% to 90%.2,3 Postoperative nausea and vomiting has the potential to cause delays in meeting discharge criteria both from the recovery room to ward, and from the day ward to home. On rare occasions, it may lead to unanticipated overnight hospital admission which leads to an increased emotional cost to the patient and economic cost to the healthcare provider. The efficacy of routine use of prophylactic antiemetics remains controversial.4 Pharmacologic prophylaxis has limited effect and increases the risk of adverse drug effects for the patient in addition to increasing overall cost of care.5,6

Studies suggest that increased crystalloid infusion for day case gynaecologic procedures in healthy patients reduces the incidence of nausea, vomiting and antiemetic use.7,8 The suggested mechanism is an improvement in gastrointestinal mucosal perfusion that mitigates the both the deleterious effects of preoperative fasting and consequent dehydration,9 and those of raised intra-abdominal pressure and surgical manipulation of bowel during laparoscopic procedures. However, excessive fluid administration in major surgery has been shown to have a negative effect on postoperative gastrointestinal function (causing an increased incidence of postoperative ileus) due to bowel oedema.10 It has been demonstrated that colloid causes less bowel oedema than equivalent volumes of crystalloid.11 Moretti et al showed that intraoperative colloid administration reduces PONV and improves the quality of postoperative recovery versus crystalloid solutions.¹² Clearly, there is an optimum perioperative fluid balance to reduce PONV without the risk of additional gastrointestinal side effects.

An arbitrary perioperative fluid load measured in ml.kg-1 does not take account of the individual fasting period and resultant preoperative fluid deficit for each patient, which can vary substantially depending on early or late (morning or afternoon) operating time.

We propose to prospectively examine the effect of intravenous fluids on PONV in a double-blind study, utilizing a standardised anaesthetic technique as normally carried out in this hospital. We hypothesise that replacement of preoperative fluid deficit with colloid will reduce the incidence of PONV versus crystalloid solution. We further propose to examine secondary outcomes relating to patient wellbeing such as headache and dizziness which are symptoms of dehydration.

Healthy patients should not experience any cardiorespiratory effects associated with administration of intravenous fluids to correct dehydration due to preoperative fasting. There may however be subclinical effects which can be detected by sensitive pulmonary function testing. Patients will be asked to perform a simple bedside lung function test before surgery and 2 hours after surgery. This will be done with a portable spirometer (Micromedical Micro Lab Spirometer), which is used routinely in our anaesthesia preoperative assessment clinic to evaluate lung function. Forced expiratory volume in the first second (litre) (FEV1), forced vital capacity (litre) (FVC) and peak flow rates (l/min) will be measured at a 45 degree position of recumbency. The best of three attempts will be chosen for further analysis as recommended by the British Thoracic Society.