Bowel function after bowel surgery: morphine with ketamine or placebo; a randomized controlled trial pilot study.

BACKGROUND: Morphine decreases gut peristalsis, and ketamine decreases morphine use after surgery, and does not slow peristalsis. Thus, the combination should result in faster return of bowel function after surgery than morphine alone. METHOD: A double-blind randomized controlled trial of saline vs. ketamine with intravenous patient-controlled-analgesia morphine for post-operative pain control was conducted on 42 patients having bowel resection. Bowel function was assessed by auscultation, time to passage of flatus and stool, and time to first retained oral intake; pain by visual analog scale. Time to return of all four measures of bowel function was the primary outcome. RESULTS: Despite a ketamine dose that in other studies had decreased morphine use without side-effects, there was no difference in bowel function, pain control, or morphine use between the two groups. Ketamine resulted in hallucinations in six out of 19 patients, with none in the placebo group (P =0.018). CONCLUSION: Low-dose ketamine was not efficacious for hastening return of bowel function, or for decreasing post-operative pain after surgery for bowel resection. It resulted in hallucinations in some patients. Those reporting hallucinations all wished to remain in the study.

Distribution of randomised controlled trials of drugs for post-operative nausea and vomiting.

PURPOSE: Randomised controlled trials (RCTs) guide therapeutic decisions. But which RCTs are done; which omitted; and which should be done? This study illustrates a method to explore these questions applied to drugs for post-operative nausea and vomiting (PONV). METHODS: Review articles listed 18 drugs for PONV. All RCTs of these drugs for PONV were sought. The first drug mentioned in an RCT was counted and tabulated against others in all the arms of the RCT (against itself in a dose-ranging RCT). Additional drugs mentioned in these RCTs were added to the study, for a total of 40 drugs. RESULTS: Drugs involved in the most RCTs were: ondansetron 131 RCTs; propofol 118; droperidol 74; metoclopramide 67; granisetron 52; scopolamine 22; tropisetron 16. Drugs involved in the fewest RCTs: two drugs with 2 RCTs; twelve drugs with one; three with none. Probability that this distribution occurred by chance: P < 0.00001; that the distribution of dose-ranging RCTs occurred by chance: P < 0.001. Regression of RCT numbers on cost: R = 0.86, P < 0.0001; on year of drug introduction: R = 0.14. Of 1600 possible comparisons of drugs for PONV, (including dose-ranging) 97.8% have never been published. CONCLUSION: Although some antiemetic drugs for PONV have been studied in large numbers of RCTs, many have not been adequately evaluated. Finding relevant RCTs and tabulating their comparison arms is useful for directing future research, and is applicable to any symptom or disorder.

Sternal acceleration ballistocardiography and arterial pressure wave analysis to determine stroke volume.

OBJECTIVE: To describe a cardiac output measurement using a new method to derive and analyze the long-axis ballistocardiogram that is less invasive than pulmonary artery thermodilution. DESIGN: Prospective physiologic study. SETTING: Intensive care unit of The Halifax Infirmary, a teaching hospital of Dalhousie University, Halifax, NS. PATIENTS: Thirty-nine patients in sinus rhythm with pulmonary artery thermodilution catheters or radial artery catheters in place. The first 30 subjects were the "learning set" and the next 9 were the "test set." INTERVENTIONS: A small (54-g) accelerometer was taped on the patient's chest. OUTCOME MEASURES: Measurements of time and amplitude coordinates of the acceleration and radial artery pressure wavepeaks, as well as anthropometric information. RESULTS: A stroke volume prediction equation was generated (R2 = 0.76) from the learning set. This equation was applied to the test set and correlated with the pulmonary artery thermodilution-derived stroke volumes (R = 0.79). Stroke volumes were compared using a previously described statistical method: a) bias (predicted > thermodilution) = 0.03 mL (95% confidence interval [CI] -4.2 to 4.8 mL); b) lower limit of agreement = -21 mL (95% CI -29 to -13 mL); c) upper limit of agreement = 22 mL (95% CI 14 to 29 mL). Of derived stroke volumes, 82% were within 15 mL of pulmonary artery thermodilution-derived values. CONCLUSIONS: The sternal acceleration ballistocardiogram combined with hemodynamic and demographic data in a probabilistic model shows promise of providing a less invasive measure of cardiac output than thermodilution.

Resting muscle sounds in anesthetized patients.

It is known that contracting muscle makes low frequency sound vibrations. Small vibrations of uncertain origin are found over resting muscle. These could be shown to be of muscle origin if they significantly diminish in response to agents expected to decrease muscle activity. Thiopental, propofol, and neuromuscular-junction blocking muscle relaxants have such properties. Twenty-one subjects slated for elective surgery for which they would routinely be anesthetized and paralysed gave informed consent to having a small accelerometer taped upon their supine biceps (9 subjects), or volar forearm (12 subjects). Recordings were made in four stages while subjects: (i) lifted a 2-kg weight just off the sponge armrest on which their outstretched arm lay; (ii) relaxed their arm in the awake state prior to anesthesia; (iii) had anesthesia induced with intravenous thiopental (n = 11) or propofol (n = 10); and (iv) were paralysed. Recordings were digitised at 172-Hz and 6-s segments fast Fourier transformed (FFT). Total signal power, as determined by the area under the power spectrum, was significantly different (p < 0.05) in all stages for the biceps and in all but stages (iii) from (iv) in the forearm. It appears that resting muscle generates measurable vibrations.

Critical incidents detected by pulse oximetry during anaesthesia.

The Critical Incident Technique was used to study anaesthetics given in a major tertiary care teaching hospital in order to define indications for monitoring with a pulse oximeter during anaesthesia. Anaesthetists were asked to use a pulse oximeter in every case and trained to report Critical Incidents in order to determine if the oximeter can shorten the time to detection of these events. Four thousand seven hundred and ninety-seven anaesthetics were given during a four-month period in 1986-87. A Critical Incident was recorded when an unexpected physiologic deterioration requiring intervention by the anaesthetist to prevent a likely bad outcome was signalled first by the pulse oximeter. Critical Incidents were classified by patient characteristics, physiologic change, type of anaesthetic, and the type, length, and place of surgery. Reports were received in 65 per cent of cases, and a Critical Incident occurred in 191 (six per cent) of these. Desaturation was the commonest physiologic change (151) and was further classified as to severity (mild 85-94 per cent saturation, moderate 75-84 per cent, and severe 75 per cent). Desaturations during the maintenance phase of anaesthesia were milder but more frequent than those in the induction or emergence phases. There were no severe desaturations in elderly patients or those receiving regional anaesthesia. No group was free of Critical Incidents. Since undetected hypoxaemia may lead to disastrous complications we recommend that a pulse oximeter be used for every anaesthetic.