Management of a pregnant patient with mechanical heart valve is a complex issue for all health care providers involved in the care of such patients. Complications may arise at any stage due to the increased haemodynamic load imposed by pregnancy or because of impaired cardiac performance often seen in these patients. In addition, the use of various cardiovascular drugs in pregnancy (especially anticoagulants) may lead to foetal loss or teratogenic complications. Additionally, the risk of thrombo-embolic complications in the mother is increased by the hypercoagulable state of pregnancy. In this review, we have attempted to draw inferences to guide management of such patients based on the available literature. It seems that in pregnant women with mechanical heart valves, recent data support warfarin use throughout pregnancy, followed by a switch to heparin and planned induction of labour. However, the complexity of this situation demands a cafeteria approach where the patient herself can choose from the available options that are supported by evidence-based information. Unfortunately there is no consensus on such data. An overview of the available literature forms the basis of this review. In conclusion, a guideline comprising pragmatic considerations is proffered.

Acute catastrophic pulmonary vasoconstriction frequently leads to cardiovascular collapse. Rapid and selective pulmonary vasodilation is desired in order to restore haemodynamic stability. This pilot study examined the effectiveness of inhaled amyl nitrite as a selective pulmonary vasodilator. Nine adult swine were anaesthetized. Acute pulmonary hypertension with haemodynamic collapse was induced with a bolus administration of a thromboxane analogue, U46619. Six animals then received a capsule of amyl nitrite. The administration of inhaled amyl nitrite decreased mean pulmonary artery pressure from 42±3 to 22±3 mmHg at five minutes (p<0.05), with a concomitant increase in cardiac output and mean arterial pressure. Pulmonary vascular resistance decreased from 4889±1338 to 380±195 dyne. sec. cm ^-5 (by 92% from the maximal pulmonary hypertension change), with significant improvement in systemic haemodynamics. During acute thromboxane-mediated pulmonary hypertension with cardiovascular collapse, prompt administration of inhaled amyl nitrite was effective in restoring pulmonary and systemic haemodynamics within five minutes.

We prospectively compared four techniques of cardiac output measurement: bolus thermodilution cardiac output (TDCO), continuous cardiac output (CCO), pulse contour cardiac output (PiCCO™), and Flowtrac^™ (FCCO), simultaneously in fifteen patients undergoing off-pump coronary artery bypass grafting (OPCAB). All the patients received pulmonary artery catheter (capable of measuring both bolus thermodilution cardiac output and CCO), PiCCO^™ arterial cannula in the left and FCCO in the right femoral artery. Cardiac indices (CI) were obtained every fifteen minutes by using all the four techniques. TDCO was treated as 'control' and the rest were treated as 'test' values. Interchangeability of techniques with TDCO was assessed by Bland and Altman plotting and mountain plot. Four hundred and thirty eight sets of data were obtained from fifteen patients. The values of cardiac output varied between 1 to 6.9 L/min. We found that the values of all the techniques were interchangeable. At certain times, the values of CI measured by both PiCCO and FCCO appeared erratic. The values of CI measured simultaneously appeared in the following descending order of accuracy; TDCO>CCO>FCCO>PiCCO ( the % times TDCO correlated with CCO, FCCO, PiCCO was 93, 86 and 80 respectively). The bias and precision (in L/ min) for CCO were 0.03, 0.06, PiCCO 0.13, 0.1 and flowtrac^™ 0.15, 0.04 respectively suggesting interchangeability. We conclude that the cardiac output measured by CCO technique and the pulse contour as measured by PiCCO and FCCO were interchangeable with TDCO more than 80% of the times.

We investigated the potential utility of transoesophageal echocardiography (TOE) in facilitating central venous catheter (CVC) insertion in patients undergoing cardiac surgery. Thirty five patients undergoing elective cardiac surgery and CVC insertion were prospectively included in the observational, single-centre clinical investigation. Following induction of general anaesthesia and tracheal intubation, the TOE probe was inserted and the bicaval view obtained prior to CVC insertion (site at discretion of the anaesthesiologist). Prospectively collected data included site and sequence of CVC insertion attempts, information regarding ease of guidewire insertion, whether or not guidewire was visualized via TOE, and other pertinent information. In 1 patient, the TOE bicaval view could not be readily obtained because of right atrial (RA) distortion. In 31 patients, the TOE bicaval view was obtained and CVC access was successful at the site of first choice (guidewire visualized in all). Three patients had noteworthy CVC insertions. In one, CVC insertion was difficult despite visualization of guidewire in the RA. In another, multiple guidewire insertions met with substantial resistance and without visualization of guidewire in the RA. One patient was found to have an unanticipated large mobile superior vena cava thrombus that extended into the RA, which changed clinical management by prompting initial CVC insertion into the femoral vein (potentially avoiding morbidity associated with thrombus dislodgement). Our prospective observational clinical study indicates that routine use of TOE during CVC insertion may help avoid potential complications associated with this intervention. If both CVC insertion and TOE are going to be used in the same patient, the benefits of TOE should be maximized by routine visualization of the bicaval view during guidewire insertion.

The present study compares the cardiac output (CO) estimated by a new, non-invsive continuous Doppler device (Ultrasonic cardiac output monitor-USCOM) with that by bolus thermodilution technique (TD). Thirty post off-pump coronary artery bypass graft surgery patients were studied in this prospective non­randomozed study. Right heart CO estimation by USCOM and TD was performed and measured in quadruplet. A total of 120 paired observations were made. The mean CO was 4.63 and 4.76 L/min as estimated by TD and USCOM respectively. For TD and USCOM, the CO had a mean bias (tendency of one technique to differ from other) of -0.13 L/min and limits of agreement (mean bias±2SD) at -0.86 and 0.59 L/min. The study reveals very good agreement between the values of CO estimated by USCOM and TD.